[pypy-commit] pypy default: Merge heads again

ademan noreply at buildbot.pypy.org
Sun Jul 3 05:33:48 CEST 2011


Author: Daniel Roberts <Ademan555 at gmail.com>
Branch: 
Changeset: r45297:a36aaf542bb2
Date: 2011-07-02 20:32 -0700
http://bitbucket.org/pypy/pypy/changeset/a36aaf542bb2/

Log:	Merge heads again

diff --git a/lib-python/modified-2.7/opcode.py b/lib-python/modified-2.7/opcode.py
--- a/lib-python/modified-2.7/opcode.py
+++ b/lib-python/modified-2.7/opcode.py
@@ -189,7 +189,6 @@
 def_op('MAP_ADD', 147)
 
 # pypy modification, experimental bytecode
-def_op('CALL_LIKELY_BUILTIN', 200)    # #args + (#kwargs << 8)
 def_op('LOOKUP_METHOD', 201)          # Index in name list
 hasname.append(201)
 def_op('CALL_METHOD', 202)            # #args not including 'self'
diff --git a/lib-python/modified-2.7/pickle.py b/lib-python/modified-2.7/pickle.py
--- a/lib-python/modified-2.7/pickle.py
+++ b/lib-python/modified-2.7/pickle.py
@@ -873,7 +873,7 @@
 
 # Unpickling machinery
 
-class Unpickler:
+class Unpickler(object):
 
     def __init__(self, file):
         """This takes a file-like object for reading a pickle data stream.
diff --git a/lib-python/modified-2.7/test/test_descr.py b/lib-python/modified-2.7/test/test_descr.py
--- a/lib-python/modified-2.7/test/test_descr.py
+++ b/lib-python/modified-2.7/test/test_descr.py
@@ -4399,14 +4399,8 @@
         self.assertTrue(l.__add__ != [5].__add__)
         self.assertTrue(l.__add__ != l.__mul__)
         self.assertTrue(l.__add__.__name__ == '__add__')
-        if hasattr(l.__add__, '__self__'):
-            # CPython
-            self.assertTrue(l.__add__.__self__ is l)
-            self.assertTrue(l.__add__.__objclass__ is list)
-        else:
-            # Python implementations where [].__add__ is a normal bound method
-            self.assertTrue(l.__add__.im_self is l)
-            self.assertTrue(l.__add__.im_class is list)
+        self.assertTrue(l.__add__.__self__ is l)
+        self.assertTrue(l.__add__.__objclass__ is list)
         self.assertEqual(l.__add__.__doc__, list.__add__.__doc__)
         try:
             hash(l.__add__)
diff --git a/lib-python/modified-2.7/test/test_dis.py b/lib-python/modified-2.7/test/test_dis.py
deleted file mode 100644
--- a/lib-python/modified-2.7/test/test_dis.py
+++ /dev/null
@@ -1,152 +0,0 @@
-# Minimal tests for dis module
-
-from test.test_support import run_unittest
-import unittest
-import sys
-import dis
-import StringIO
-
-
-def _f(a):
-    print a
-    return 1
-
-dis_f = """\
- %-4d         0 LOAD_FAST                0 (a)
-              3 PRINT_ITEM
-              4 PRINT_NEWLINE
-
- %-4d         5 LOAD_CONST               1 (1)
-              8 RETURN_VALUE
-"""%(_f.func_code.co_firstlineno + 1,
-     _f.func_code.co_firstlineno + 2)
-
-
-# we "call" rangexxx() instead of range() to disable the
-# pypy optimization that turns it into CALL_LIKELY_BUILTIN.
-def bug708901():
-    for res in rangexxx(1,
-                        10):
-        pass
-
-dis_bug708901 = """\
- %-4d         0 SETUP_LOOP              23 (to 26)
-              3 LOAD_GLOBAL              0 (rangexxx)
-              6 LOAD_CONST               1 (1)
-
- %-4d         9 LOAD_CONST               2 (10)
-             12 CALL_FUNCTION            2
-             15 GET_ITER
-        >>   16 FOR_ITER                 6 (to 25)
-             19 STORE_FAST               0 (res)
-
- %-4d        22 JUMP_ABSOLUTE           16
-        >>   25 POP_BLOCK
-        >>   26 LOAD_CONST               0 (None)
-             29 RETURN_VALUE
-"""%(bug708901.func_code.co_firstlineno + 1,
-     bug708901.func_code.co_firstlineno + 2,
-     bug708901.func_code.co_firstlineno + 3)
-
-
-def bug1333982(x=[]):
-    assert 0, ([s for s in x] +
-              1)
-    pass
-
-dis_bug1333982 = """\
- %-4d         0 LOAD_CONST               1 (0)
-              3 POP_JUMP_IF_TRUE        38
-              6 LOAD_GLOBAL              0 (AssertionError)
-              9 BUILD_LIST               0
-             12 LOAD_FAST                0 (x)
-             15 GET_ITER
-        >>   16 FOR_ITER                12 (to 31)
-             19 STORE_FAST               1 (s)
-             22 LOAD_FAST                1 (s)
-             25 LIST_APPEND              2
-             28 JUMP_ABSOLUTE           16
-
- %-4d   >>   31 LOAD_CONST               2 (1)
-             34 BINARY_ADD
-             35 RAISE_VARARGS            2
-
- %-4d   >>   38 LOAD_CONST               0 (None)
-             41 RETURN_VALUE
-"""%(bug1333982.func_code.co_firstlineno + 1,
-     bug1333982.func_code.co_firstlineno + 2,
-     bug1333982.func_code.co_firstlineno + 3)
-
-_BIG_LINENO_FORMAT = """\
-%3d           0 LOAD_GLOBAL              0 (spam)
-              3 POP_TOP
-              4 LOAD_CONST               0 (None)
-              7 RETURN_VALUE
-"""
-
-class DisTests(unittest.TestCase):
-    def do_disassembly_test(self, func, expected):
-        s = StringIO.StringIO()
-        save_stdout = sys.stdout
-        sys.stdout = s
-        dis.dis(func)
-        sys.stdout = save_stdout
-        got = s.getvalue()
-        # Trim trailing blanks (if any).
-        lines = got.split('\n')
-        lines = [line.rstrip() for line in lines]
-        expected = expected.split("\n")
-        import difflib
-        if expected != lines:
-            self.fail(
-                "events did not match expectation:\n" +
-                "\n".join(difflib.ndiff(expected,
-                                        lines)))
-
-    def test_opmap(self):
-        self.assertEqual(dis.opmap["STOP_CODE"], 0)
-        self.assertIn(dis.opmap["LOAD_CONST"], dis.hasconst)
-        self.assertIn(dis.opmap["STORE_NAME"], dis.hasname)
-
-    def test_opname(self):
-        self.assertEqual(dis.opname[dis.opmap["LOAD_FAST"]], "LOAD_FAST")
-
-    def test_boundaries(self):
-        self.assertEqual(dis.opmap["EXTENDED_ARG"], dis.EXTENDED_ARG)
-        self.assertEqual(dis.opmap["STORE_NAME"], dis.HAVE_ARGUMENT)
-
-    def test_dis(self):
-        self.do_disassembly_test(_f, dis_f)
-
-    def test_bug_708901(self):
-        self.do_disassembly_test(bug708901, dis_bug708901)
-
-    def test_bug_1333982(self):
-        # This one is checking bytecodes generated for an `assert` statement,
-        # so fails if the tests are run with -O.  Skip this test then.
-        if __debug__:
-            self.do_disassembly_test(bug1333982, dis_bug1333982)
-
-    def test_big_linenos(self):
-        def func(count):
-            namespace = {}
-            func = "def foo():\n " + "".join(["\n "] * count + ["spam\n"])
-            exec func in namespace
-            return namespace['foo']
-
-        # Test all small ranges
-        for i in xrange(1, 300):
-            expected = _BIG_LINENO_FORMAT % (i + 2)
-            self.do_disassembly_test(func(i), expected)
-
-        # Test some larger ranges too
-        for i in xrange(300, 5000, 10):
-            expected = _BIG_LINENO_FORMAT % (i + 2)
-            self.do_disassembly_test(func(i), expected)
-
-def test_main():
-    run_unittest(DisTests)
-
-
-if __name__ == "__main__":
-    test_main()
diff --git a/lib-python/modified-2.7/test/test_weakref.py b/lib-python/modified-2.7/test/test_weakref.py
--- a/lib-python/modified-2.7/test/test_weakref.py
+++ b/lib-python/modified-2.7/test/test_weakref.py
@@ -993,13 +993,13 @@
         self.assertTrue(len(weakdict) == 2)
         k, v = weakdict.popitem()
         self.assertTrue(len(weakdict) == 1)
-        if k is key1:
+        if k == key1:
             self.assertTrue(v is value1)
         else:
             self.assertTrue(v is value2)
         k, v = weakdict.popitem()
         self.assertTrue(len(weakdict) == 0)
-        if k is key1:
+        if k == key1:
             self.assertTrue(v is value1)
         else:
             self.assertTrue(v is value2)
diff --git a/pypy/annotation/bookkeeper.py b/pypy/annotation/bookkeeper.py
--- a/pypy/annotation/bookkeeper.py
+++ b/pypy/annotation/bookkeeper.py
@@ -299,12 +299,13 @@
             listdef.generalize_range_step(flags['range_step'])
         return SomeList(listdef)
 
-    def getdictdef(self, is_r_dict=False):
+    def getdictdef(self, is_r_dict=False, force_non_null=False):
         """Get the DictDef associated with the current position."""
         try:
             dictdef = self.dictdefs[self.position_key]
         except KeyError:
-            dictdef = DictDef(self, is_r_dict=is_r_dict)
+            dictdef = DictDef(self, is_r_dict=is_r_dict,
+                              force_non_null=force_non_null)
             self.dictdefs[self.position_key] = dictdef
         return dictdef
 
diff --git a/pypy/annotation/builtin.py b/pypy/annotation/builtin.py
--- a/pypy/annotation/builtin.py
+++ b/pypy/annotation/builtin.py
@@ -311,8 +311,14 @@
 def robjmodel_we_are_translated():
     return immutablevalue(True)
 
-def robjmodel_r_dict(s_eqfn, s_hashfn):
-    dictdef = getbookkeeper().getdictdef(is_r_dict=True)
+def robjmodel_r_dict(s_eqfn, s_hashfn, s_force_non_null=None):
+    if s_force_non_null is None:
+        force_non_null = False
+    else:
+        assert s_force_non_null.is_constant()
+        force_non_null = s_force_non_null.const
+    dictdef = getbookkeeper().getdictdef(is_r_dict=True,
+                                         force_non_null=force_non_null)
     dictdef.dictkey.update_rdict_annotations(s_eqfn, s_hashfn)
     return SomeDict(dictdef)
 
@@ -351,17 +357,6 @@
 def llmemory_cast_int_to_adr(s):
     return SomeAddress()
 
-
-##def rarith_ovfcheck(s_obj):
-##    if isinstance(s_obj, SomeInteger) and s_obj.unsigned:
-##        getbookkeeper().warning("ovfcheck on unsigned")
-##    return s_obj
-
-##def rarith_ovfcheck_lshift(s_obj1, s_obj2):
-##    if isinstance(s_obj1, SomeInteger) and s_obj1.unsigned:
-##        getbookkeeper().warning("ovfcheck_lshift with unsigned")
-##    return SomeInteger()
-
 def unicodedata_decimal(s_uchr):
     raise TypeError, "unicodedate.decimal() calls should not happen at interp-level"    
 
@@ -379,8 +374,6 @@
         original = getattr(__builtin__, name[8:])
         BUILTIN_ANALYZERS[original] = value
 
-##BUILTIN_ANALYZERS[pypy.rlib.rarithmetic.ovfcheck] = rarith_ovfcheck
-##BUILTIN_ANALYZERS[pypy.rlib.rarithmetic.ovfcheck_lshift] = rarith_ovfcheck_lshift
 BUILTIN_ANALYZERS[pypy.rlib.rarithmetic.intmask] = rarith_intmask
 BUILTIN_ANALYZERS[pypy.rlib.objectmodel.instantiate] = robjmodel_instantiate
 BUILTIN_ANALYZERS[pypy.rlib.objectmodel.we_are_translated] = (
diff --git a/pypy/annotation/dictdef.py b/pypy/annotation/dictdef.py
--- a/pypy/annotation/dictdef.py
+++ b/pypy/annotation/dictdef.py
@@ -85,12 +85,14 @@
 
     def __init__(self, bookkeeper, s_key = s_ImpossibleValue,
                                  s_value = s_ImpossibleValue,
-                               is_r_dict = False):
+                               is_r_dict = False,
+                           force_non_null = False):
         self.dictkey = DictKey(bookkeeper, s_key, is_r_dict)
         self.dictkey.itemof[self] = True
         self.dictvalue = DictValue(bookkeeper, s_value)
         self.dictvalue.itemof[self] = True
         self.bookkeeper = bookkeeper
+        self.force_non_null = force_non_null
 
     def read_key(self, position_key=None):
         if position_key is None:
diff --git a/pypy/config/pypyoption.py b/pypy/config/pypyoption.py
--- a/pypy/config/pypyoption.py
+++ b/pypy/config/pypyoption.py
@@ -129,9 +129,6 @@
                  cmdline='--objspace -o'),
 
     OptionDescription("opcodes", "opcodes to enable in the interpreter", [
-        BoolOption("CALL_LIKELY_BUILTIN", "emit a special bytecode for likely calls to builtin functions",
-                   default=False,
-                   requires=[("translation.stackless", False)]),
         BoolOption("CALL_METHOD", "emit a special bytecode for expr.name()",
                    default=False),
         ]),
@@ -266,13 +263,7 @@
         BoolOption("withcelldict",
                    "use dictionaries that are optimized for being used as module dicts",
                    default=False,
-                   requires=[("objspace.opcodes.CALL_LIKELY_BUILTIN", False),
-                             ("objspace.honor__builtins__", False)]),
-
-        BoolOption("withdictmeasurement",
-                   "create huge files with masses of information "
-                   "about dictionaries",
-                   default=False),
+                   requires=[("objspace.honor__builtins__", False)]),
 
         BoolOption("withmapdict",
                    "make instances really small but slow without the JIT",
@@ -355,8 +346,6 @@
     backend = config.translation.backend
 
     # all the good optimizations for PyPy should be listed here
-    if level in ['2', '3']:
-        config.objspace.opcodes.suggest(CALL_LIKELY_BUILTIN=True)
     if level in ['2', '3', 'jit']:
         config.objspace.opcodes.suggest(CALL_METHOD=True)
         config.objspace.std.suggest(withrangelist=True)
diff --git a/pypy/doc/config/objspace.opcodes.CALL_LIKELY_BUILTIN.txt b/pypy/doc/config/objspace.opcodes.CALL_LIKELY_BUILTIN.txt
deleted file mode 100644
--- a/pypy/doc/config/objspace.opcodes.CALL_LIKELY_BUILTIN.txt
+++ /dev/null
@@ -1,12 +0,0 @@
-Introduce a new opcode called ``CALL_LIKELY_BUILTIN``. It is used when something
-is called, that looks like a builtin function (but could in reality be shadowed
-by a name in the module globals). For all module globals dictionaries it is
-then tracked which builtin name is shadowed in this module. If the
-``CALL_LIKELY_BUILTIN`` opcode is executed, it is checked whether the builtin is
-shadowed. If not, the corresponding builtin is called. Otherwise the object that
-is shadowing it is called instead. If no shadowing is happening, this saves two
-dictionary lookups on calls to builtins.
-
-For more information, see the section in `Standard Interpreter Optimizations`_.
-
-.. _`Standard Interpreter Optimizations`: ../interpreter-optimizations.html#call-likely-builtin
diff --git a/pypy/doc/config/objspace.std.withdictmeasurement.txt b/pypy/doc/config/objspace.std.withdictmeasurement.txt
deleted file mode 100644
--- a/pypy/doc/config/objspace.std.withdictmeasurement.txt
+++ /dev/null
@@ -1,3 +0,0 @@
-Internal option.
-
-.. internal
diff --git a/pypy/doc/cpython_differences.rst b/pypy/doc/cpython_differences.rst
--- a/pypy/doc/cpython_differences.rst
+++ b/pypy/doc/cpython_differences.rst
@@ -248,5 +248,7 @@
   never a dictionary as it sometimes is in CPython. Assigning to
   ``__builtins__`` has no effect.
 
+* object identity of immutable keys in dictionaries is not necessarily preserved.
+  Never compare immutable objects with ``is``.
+
 .. include:: _ref.txt
-
diff --git a/pypy/interpreter/argument.py b/pypy/interpreter/argument.py
--- a/pypy/interpreter/argument.py
+++ b/pypy/interpreter/argument.py
@@ -17,7 +17,7 @@
         self.varargname = varargname
         self.kwargname = kwargname
 
-    @jit.purefunction
+    @jit.elidable
     def find_argname(self, name):
         try:
             return self.argnames.index(name)
diff --git a/pypy/interpreter/astcompiler/assemble.py b/pypy/interpreter/astcompiler/assemble.py
--- a/pypy/interpreter/astcompiler/assemble.py
+++ b/pypy/interpreter/astcompiler/assemble.py
@@ -655,9 +655,6 @@
 def _compute_CALL_FUNCTION_VAR_KW(arg):
     return -_num_args(arg) - 2
 
-def _compute_CALL_LIKELY_BUILTIN(arg):
-    return -(arg & 0xFF) + 1
-
 def _compute_CALL_METHOD(arg):
     return -_num_args(arg) - 1
 
diff --git a/pypy/interpreter/astcompiler/codegen.py b/pypy/interpreter/astcompiler/codegen.py
--- a/pypy/interpreter/astcompiler/codegen.py
+++ b/pypy/interpreter/astcompiler/codegen.py
@@ -12,7 +12,6 @@
 from pypy.interpreter.pyparser.error import SyntaxError
 from pypy.tool import stdlib_opcode as ops
 from pypy.interpreter.error import OperationError
-from pypy.module.__builtin__.__init__ import BUILTIN_TO_INDEX
 
 
 def compile_ast(space, module, info):
@@ -942,8 +941,7 @@
 
     def visit_Call(self, call):
         self.update_position(call.lineno)
-        if self._optimize_builtin_call(call) or \
-                self._optimize_method_call(call):
+        if self._optimize_method_call(call):
             return
         call.func.walkabout(self)
         arg = 0
@@ -977,28 +975,6 @@
     def _call_has_simple_args(self, call):
         return self._call_has_no_star_args(call) and not call.keywords
 
-    def _optimize_builtin_call(self, call):
-        if not self.space.config.objspace.opcodes.CALL_LIKELY_BUILTIN or \
-                not self._call_has_simple_args(call) or \
-                not isinstance(call.func, ast.Name):
-            return False
-        func_name = call.func
-        assert isinstance(func_name, ast.Name)
-        name_scope = self.scope.lookup(func_name.id)
-        if name_scope == symtable.SCOPE_GLOBAL_IMPLICIT or \
-                name_scope == symtable.SCOPE_UNKNOWN:
-            builtin_index = BUILTIN_TO_INDEX.get(func_name.id, -1)
-            if builtin_index != -1:
-                if call.args:
-                    args_count = len(call.args)
-                    self.visit_sequence(call.args)
-                else:
-                    args_count = 0
-                arg = builtin_index << 8 | args_count
-                self.emit_op_arg(ops.CALL_LIKELY_BUILTIN, arg)
-                return True
-        return False
-
     def _optimize_method_call(self, call):
         if not self.space.config.objspace.opcodes.CALL_METHOD or \
                 not self._call_has_no_star_args(call) or \
diff --git a/pypy/interpreter/baseobjspace.py b/pypy/interpreter/baseobjspace.py
--- a/pypy/interpreter/baseobjspace.py
+++ b/pypy/interpreter/baseobjspace.py
@@ -311,9 +311,6 @@
             mod = self.interpclass_w(w_mod)
             if isinstance(mod, Module) and mod.startup_called:
                 mod.shutdown(self)
-        if self.config.objspace.std.withdictmeasurement:
-            from pypy.objspace.std.dictmultiobject import report
-            report()
         if self.config.objspace.logbytecodes:
             self.reportbytecodecounts()
         if self.config.objspace.std.logspaceoptypes:
diff --git a/pypy/interpreter/function.py b/pypy/interpreter/function.py
--- a/pypy/interpreter/function.py
+++ b/pypy/interpreter/function.py
@@ -16,7 +16,7 @@
 
 funccallunrolling = unrolling_iterable(range(4))
 
- at jit.purefunction_promote()
+ at jit.elidable_promote()
 def _get_immutable_code(func):
     assert not func.can_change_code
     return func.code
@@ -63,7 +63,7 @@
         if jit.we_are_jitted():
             if not self.can_change_code:
                 return _get_immutable_code(self)
-            return jit.hint(self.code, promote=True)
+            return jit.promote(self.code)
         return self.code
 
     def funccall(self, *args_w): # speed hack
diff --git a/pypy/interpreter/generator.py b/pypy/interpreter/generator.py
--- a/pypy/interpreter/generator.py
+++ b/pypy/interpreter/generator.py
@@ -62,7 +62,7 @@
             raise operr
         # XXX it's not clear that last_instr should be promoted at all
         # but as long as it is necessary for call_assembler, let's do it early
-        last_instr = jit.hint(frame.last_instr, promote=True)
+        last_instr = jit.promote(frame.last_instr)
         if last_instr == -1:
             if w_arg and not space.is_w(w_arg, space.w_None):
                 msg = "can't send non-None value to a just-started generator"
diff --git a/pypy/interpreter/pyopcode.py b/pypy/interpreter/pyopcode.py
--- a/pypy/interpreter/pyopcode.py
+++ b/pypy/interpreter/pyopcode.py
@@ -1060,18 +1060,6 @@
     def SET_LINENO(self, lineno, next_instr):
         pass
 
-    def CALL_LIKELY_BUILTIN(self, oparg, next_instr):
-        # overridden by faster version in the standard object space.
-        from pypy.module.__builtin__ import OPTIMIZED_BUILTINS
-        varname = OPTIMIZED_BUILTINS[oparg >> 8]
-        w_function = self._load_global(varname)
-        nargs = oparg&0xFF
-        try:
-            w_result = self.space.call_valuestack(w_function, nargs, self)
-        finally:
-            self.dropvalues(nargs)
-        self.pushvalue(w_result)
-
     # overridden by faster version in the standard object space.
     LOOKUP_METHOD = LOAD_ATTR
     CALL_METHOD = CALL_FUNCTION
diff --git a/pypy/interpreter/test/test_executioncontext.py b/pypy/interpreter/test/test_executioncontext.py
--- a/pypy/interpreter/test/test_executioncontext.py
+++ b/pypy/interpreter/test/test_executioncontext.py
@@ -232,31 +232,6 @@
         assert [i[0] for i in events] == ['c_call', 'c_return', 'return', 'c_call']
         assert events[0][1] == events[1][1]
 
-    def test_tracing_range_builtinshortcut(self):
-        opts = {"objspace.opcodes.CALL_LIKELY_BUILTIN": True}
-        space = gettestobjspace(**opts)
-        source = """def f(profile):
-        import sys
-        sys.setprofile(profile)
-        range(10)
-        sys.setprofile(None)
-        """
-        w_events = space.appexec([space.wrap(source)], """(source):
-        import sys
-        l = []
-        def profile(frame, event, arg):
-            l.append((event, arg))
-        d = {}
-        exec source in d
-        f = d['f']
-        f(profile)
-        import dis
-        print dis.dis(f)
-        return l
-        """)
-        events = space.unwrap(w_events)
-        assert [i[0] for i in events] == ['c_call', 'c_return', 'c_call']
-
     def test_profile_and_exception(self):
         space = self.space
         w_res = space.appexec([], """():
@@ -280,9 +255,6 @@
         """)
 
 
-class TestExecutionContextWithCallLikelyBuiltin(TestExecutionContext):
-    keywords = {'objspace.opcodes.CALL_LIKELY_BUILTIN': True}
-
 class TestExecutionContextWithCallMethod(TestExecutionContext):
     keywords = {'objspace.opcodes.CALL_METHOD': True}
 
diff --git a/pypy/interpreter/test/test_typedef.py b/pypy/interpreter/test/test_typedef.py
--- a/pypy/interpreter/test/test_typedef.py
+++ b/pypy/interpreter/test/test_typedef.py
@@ -16,7 +16,7 @@
 
         def g():
             f()
-        
+
         try:
             g()
         except:
@@ -205,6 +205,7 @@
         raises(OSError, os.lseek, fd, 7, 0)
 
     def test_method_attrs(self):
+        import sys
         class A(object):
             def m(self):
                 "aaa"
diff --git a/pypy/interpreter/typedef.py b/pypy/interpreter/typedef.py
--- a/pypy/interpreter/typedef.py
+++ b/pypy/interpreter/typedef.py
@@ -9,7 +9,7 @@
 from pypy.interpreter.error import OperationError, operationerrfmt
 from pypy.tool.sourcetools import compile2, func_with_new_name
 from pypy.rlib.objectmodel import instantiate, compute_identity_hash, specialize
-from pypy.rlib.jit import hint
+from pypy.rlib.jit import promote
 
 class TypeDef:
     def __init__(self, __name, __base=None, **rawdict):
@@ -206,7 +206,7 @@
             user_overridden_class = True
 
             def getclass(self, space):
-                return hint(self.w__class__, promote=True)
+                return promote(self.w__class__)
 
             def setclass(self, space, w_subtype):
                 # only used by descr_set___class__
diff --git a/pypy/jit/backend/x86/assembler.py b/pypy/jit/backend/x86/assembler.py
--- a/pypy/jit/backend/x86/assembler.py
+++ b/pypy/jit/backend/x86/assembler.py
@@ -895,7 +895,7 @@
 
     def regalloc_push(self, loc):
         if isinstance(loc, RegLoc) and loc.is_xmm:
-            self.mc.SUB_ri(esp.value, 2*WORD)
+            self.mc.SUB_ri(esp.value, 8)   # = size of doubles
             self.mc.MOVSD_sx(0, loc.value)
         elif WORD == 4 and isinstance(loc, StackLoc) and loc.width == 8:
             # XXX evil trick
@@ -907,7 +907,7 @@
     def regalloc_pop(self, loc):
         if isinstance(loc, RegLoc) and loc.is_xmm:
             self.mc.MOVSD_xs(loc.value, 0)
-            self.mc.ADD_ri(esp.value, 2*WORD)
+            self.mc.ADD_ri(esp.value, 8)   # = size of doubles
         elif WORD == 4 and isinstance(loc, StackLoc) and loc.width == 8:
             # XXX evil trick
             self.mc.POP_b(get_ebp_ofs(loc.position + 1))
diff --git a/pypy/jit/backend/x86/test/test_assembler.py b/pypy/jit/backend/x86/test/test_assembler.py
--- a/pypy/jit/backend/x86/test/test_assembler.py
+++ b/pypy/jit/backend/x86/test/test_assembler.py
@@ -1,13 +1,15 @@
 from pypy.jit.backend.x86.regloc import *
 from pypy.jit.backend.x86.assembler import Assembler386
 from pypy.jit.backend.x86.regalloc import X86FrameManager, get_ebp_ofs
-from pypy.jit.metainterp.history import BoxInt, BoxPtr, BoxFloat, INT, REF, FLOAT
+from pypy.jit.metainterp.history import BoxInt, BoxPtr, BoxFloat, ConstFloat
+from pypy.jit.metainterp.history import INT, REF, FLOAT
 from pypy.rlib.rarithmetic import intmask
 from pypy.rpython.lltypesystem import lltype, llmemory, rffi
 from pypy.jit.backend.x86.arch import WORD, IS_X86_32, IS_X86_64
 from pypy.jit.backend.detect_cpu import getcpuclass 
 from pypy.jit.backend.x86.regalloc import X86RegisterManager, X86_64_RegisterManager, X86XMMRegisterManager, X86_64_XMMRegisterManager
 from pypy.jit.codewriter import longlong
+import ctypes
 
 ACTUAL_CPU = getcpuclass()
 
@@ -238,3 +240,103 @@
         assert assembler.fail_boxes_int.getitem(i) == expected_ints[i]
         assert assembler.fail_boxes_ptr.getitem(i) == expected_ptrs[i]
         assert assembler.fail_boxes_float.getitem(i) == expected_floats[i]
+
+# ____________________________________________________________
+
+class TestRegallocPushPop(object):
+
+    def do_test(self, callback):
+        from pypy.jit.backend.x86.regalloc import X86FrameManager
+        from pypy.jit.backend.x86.regalloc import X86XMMRegisterManager
+        class FakeToken:
+            class compiled_loop_token:
+                asmmemmgr_blocks = None
+        cpu = ACTUAL_CPU(None, None)
+        cpu.setup()
+        looptoken = FakeToken()
+        asm = cpu.assembler
+        asm.setup_once()
+        asm.setup(looptoken)
+        self.fm = X86FrameManager()
+        self.xrm = X86XMMRegisterManager(None, frame_manager=self.fm,
+                                         assembler=asm)
+        callback(asm)
+        asm.mc.RET()
+        rawstart = asm.materialize_loop(looptoken)
+        #
+        F = ctypes.CFUNCTYPE(ctypes.c_long)
+        fn = ctypes.cast(rawstart, F)
+        res = fn()
+        return res
+
+    def test_simple(self):
+        def callback(asm):
+            asm.mov(imm(42), edx)
+            asm.regalloc_push(edx)
+            asm.regalloc_pop(eax)
+        res = self.do_test(callback)
+        assert res == 42
+
+    def test_push_stack(self):
+        def callback(asm):
+            loc = self.fm.frame_pos(5, INT)
+            asm.mc.SUB_ri(esp.value, 64)
+            asm.mov(imm(42), loc)
+            asm.regalloc_push(loc)
+            asm.regalloc_pop(eax)
+            asm.mc.ADD_ri(esp.value, 64)
+        res = self.do_test(callback)
+        assert res == 42
+
+    def test_pop_stack(self):
+        def callback(asm):
+            loc = self.fm.frame_pos(5, INT)
+            asm.mc.SUB_ri(esp.value, 64)
+            asm.mov(imm(42), edx)
+            asm.regalloc_push(edx)
+            asm.regalloc_pop(loc)
+            asm.mov(loc, eax)
+            asm.mc.ADD_ri(esp.value, 64)
+        res = self.do_test(callback)
+        assert res == 42
+
+    def test_simple_xmm(self):
+        def callback(asm):
+            c = ConstFloat(longlong.getfloatstorage(-42.5))
+            loc = self.xrm.convert_to_imm(c)
+            asm.mov(loc, xmm5)
+            asm.regalloc_push(xmm5)
+            asm.regalloc_pop(xmm0)
+            asm.mc.CVTTSD2SI(eax, xmm0)
+        res = self.do_test(callback)
+        assert res == -42
+
+    def test_push_stack_xmm(self):
+        def callback(asm):
+            c = ConstFloat(longlong.getfloatstorage(-42.5))
+            loc = self.xrm.convert_to_imm(c)
+            loc2 = self.fm.frame_pos(4, FLOAT)
+            asm.mc.SUB_ri(esp.value, 64)
+            asm.mov(loc, xmm5)
+            asm.mov(xmm5, loc2)
+            asm.regalloc_push(loc2)
+            asm.regalloc_pop(xmm0)
+            asm.mc.ADD_ri(esp.value, 64)
+            asm.mc.CVTTSD2SI(eax, xmm0)
+        res = self.do_test(callback)
+        assert res == -42
+
+    def test_pop_stack_xmm(self):
+        def callback(asm):
+            c = ConstFloat(longlong.getfloatstorage(-42.5))
+            loc = self.xrm.convert_to_imm(c)
+            loc2 = self.fm.frame_pos(4, FLOAT)
+            asm.mc.SUB_ri(esp.value, 64)
+            asm.mov(loc, xmm5)
+            asm.regalloc_push(xmm5)
+            asm.regalloc_pop(loc2)
+            asm.mov(loc2, xmm0)
+            asm.mc.ADD_ri(esp.value, 64)
+            asm.mc.CVTTSD2SI(eax, xmm0)
+        res = self.do_test(callback)
+        assert res == -42
diff --git a/pypy/jit/backend/x86/test/test_zrpy_gc.py b/pypy/jit/backend/x86/test/test_zrpy_gc.py
--- a/pypy/jit/backend/x86/test/test_zrpy_gc.py
+++ b/pypy/jit/backend/x86/test/test_zrpy_gc.py
@@ -10,7 +10,7 @@
 from pypy.rlib import rgc
 from pypy.rpython.lltypesystem import lltype, llmemory, rffi
 from pypy.rlib.jit import JitDriver, dont_look_inside
-from pypy.rlib.jit import purefunction, unroll_safe
+from pypy.rlib.jit import elidable, unroll_safe
 from pypy.jit.backend.llsupport.gc import GcLLDescr_framework
 from pypy.tool.udir import udir
 from pypy.config.translationoption import DEFL_GC
@@ -561,7 +561,7 @@
         self.run('compile_framework_external_exception_handling')
 
     def define_compile_framework_bug1(self):
-        @purefunction
+        @elidable
         def nonmoving():
             x = X(1)
             for i in range(7):
diff --git a/pypy/jit/backend/x86/test/test_ztranslation.py b/pypy/jit/backend/x86/test/test_ztranslation.py
--- a/pypy/jit/backend/x86/test/test_ztranslation.py
+++ b/pypy/jit/backend/x86/test/test_ztranslation.py
@@ -2,7 +2,7 @@
 from pypy.tool.udir import udir
 from pypy.rlib.jit import JitDriver, unroll_parameters
 from pypy.rlib.jit import PARAMETERS, dont_look_inside
-from pypy.rlib.jit import hint
+from pypy.rlib.jit import promote
 from pypy.jit.metainterp.jitprof import Profiler
 from pypy.jit.backend.detect_cpu import getcpuclass
 from pypy.jit.backend.test.support import CCompiledMixin
@@ -78,8 +78,7 @@
             x = float(j)
             while i > 0:
                 jitdriver2.jit_merge_point(i=i, res=res, func=func, x=x)
-                jitdriver2.can_enter_jit(i=i, res=res, func=func, x=x)
-                func = hint(func, promote=True)
+                promote(func)
                 argchain = ArgChain()
                 argchain.arg(x)
                 res = func.call(argchain, rffi.DOUBLE)
diff --git a/pypy/jit/codewriter/call.py b/pypy/jit/codewriter/call.py
--- a/pypy/jit/codewriter/call.py
+++ b/pypy/jit/codewriter/call.py
@@ -208,12 +208,12 @@
         assert NON_VOID_ARGS == [T for T in ARGS if T is not lltype.Void]
         assert RESULT == FUNC.RESULT
         # ok
-        # get the 'pure' and 'loopinvariant' flags from the function object
-        pure = False
+        # get the 'elidable' and 'loopinvariant' flags from the function object
+        elidable = False
         loopinvariant = False
         if op.opname == "direct_call":
             func = getattr(get_funcobj(op.args[0].value), '_callable', None)
-            pure = getattr(func, "_pure_function_", False)
+            elidable = getattr(func, "_elidable_function_", False)
             loopinvariant = getattr(func, "_jit_loop_invariant_", False)
             if loopinvariant:
                 assert not NON_VOID_ARGS, ("arguments not supported for "
@@ -225,9 +225,9 @@
                 extraeffect = EffectInfo.EF_FORCES_VIRTUAL_OR_VIRTUALIZABLE
             elif loopinvariant:
                 extraeffect = EffectInfo.EF_LOOPINVARIANT
-            elif pure:
+            elif elidable:
                 # XXX check what to do about exceptions (also MemoryError?)
-                extraeffect = EffectInfo.EF_PURE
+                extraeffect = EffectInfo.EF_ELIDABLE
             elif self._canraise(op):
                 extraeffect = EffectInfo.EF_CAN_RAISE
             else:
@@ -239,7 +239,7 @@
         #
         if oopspecindex != EffectInfo.OS_NONE:
             assert effectinfo is not None
-        if pure or loopinvariant:
+        if elidable or loopinvariant:
             assert effectinfo is not None
             assert extraeffect != EffectInfo.EF_FORCES_VIRTUAL_OR_VIRTUALIZABLE
             # XXX this should also say assert not can_invalidate, but
diff --git a/pypy/jit/codewriter/effectinfo.py b/pypy/jit/codewriter/effectinfo.py
--- a/pypy/jit/codewriter/effectinfo.py
+++ b/pypy/jit/codewriter/effectinfo.py
@@ -9,7 +9,7 @@
     _cache = {}
 
     # the 'extraeffect' field is one of the following values:
-    EF_PURE                            = 0 #pure function (and cannot raise)
+    EF_ELIDABLE                        = 0 #elidable function (and cannot raise)
     EF_LOOPINVARIANT                   = 1 #special: call it only once per loop
     EF_CANNOT_RAISE                    = 2 #a function which cannot raise
     EF_CAN_RAISE                       = 3 #normal function (can raise)
@@ -92,7 +92,7 @@
         result.readonly_descrs_fields = readonly_descrs_fields
         result.readonly_descrs_arrays = readonly_descrs_arrays
         if extraeffect == EffectInfo.EF_LOOPINVARIANT or \
-           extraeffect == EffectInfo.EF_PURE:            
+           extraeffect == EffectInfo.EF_ELIDABLE:
             result.write_descrs_fields = []
             result.write_descrs_arrays = []
         else:
diff --git a/pypy/jit/codewriter/jtransform.py b/pypy/jit/codewriter/jtransform.py
--- a/pypy/jit/codewriter/jtransform.py
+++ b/pypy/jit/codewriter/jtransform.py
@@ -847,7 +847,7 @@
                 op1 = self.prepare_builtin_call(op, "llong_%s", args)
                 op2 = self._handle_oopspec_call(op1, args,
                                                 EffectInfo.OS_LLONG_%s,
-                                                EffectInfo.EF_PURE)
+                                                EffectInfo.EF_ELIDABLE)
                 if %r == "TO_INT":
                     assert op2.result.concretetype == lltype.Signed
                 return op2
@@ -1328,13 +1328,13 @@
                     otherindex += EffectInfo._OS_offset_uni
                 self._register_extra_helper(otherindex, othername,
                                             argtypes, resulttype,
-                                            EffectInfo.EF_PURE)
+                                            EffectInfo.EF_ELIDABLE)
         #
         return self._handle_oopspec_call(op, args, dict[oopspec_name],
-                                         EffectInfo.EF_PURE)
+                                         EffectInfo.EF_ELIDABLE)
 
     def _handle_str2unicode_call(self, op, oopspec_name, args):
-        # ll_str2unicode is not EF_PURE, because it can raise
+        # ll_str2unicode is not EF_ELIDABLE, because it can raise
         # UnicodeDecodeError...
         return self._handle_oopspec_call(op, args, EffectInfo.OS_STR2UNICODE)
 
@@ -1380,7 +1380,7 @@
     
     def _handle_math_sqrt_call(self, op, oopspec_name, args):
         return self._handle_oopspec_call(op, args, EffectInfo.OS_MATH_SQRT,
-                                         EffectInfo.EF_PURE)
+                                         EffectInfo.EF_ELIDABLE)
 
     def rewrite_op_jit_force_quasi_immutable(self, op):
         v_inst, c_fieldname = op.args
diff --git a/pypy/jit/codewriter/policy.py b/pypy/jit/codewriter/policy.py
--- a/pypy/jit/codewriter/policy.py
+++ b/pypy/jit/codewriter/policy.py
@@ -35,8 +35,8 @@
     def _reject_function(self, func):
         if hasattr(func, '_jit_look_inside_'):
             return not func._jit_look_inside_
-        # explicitly pure functions are always opaque
-        if getattr(func, '_pure_function_', False):
+        # explicitly elidable functions are always opaque
+        if getattr(func, '_elidable_function_', False):
             return True
         # pypy.rpython.module.* are opaque helpers
         mod = func.__module__ or '?'
diff --git a/pypy/jit/codewriter/test/test_jtransform.py b/pypy/jit/codewriter/test/test_jtransform.py
--- a/pypy/jit/codewriter/test/test_jtransform.py
+++ b/pypy/jit/codewriter/test/test_jtransform.py
@@ -122,7 +122,7 @@
             if oopspecindex == EI.OS_STR2UNICODE:
                 assert extraeffect == None    # not pure, can raise!
             else:
-                assert extraeffect == EI.EF_PURE
+                assert extraeffect == EI.EF_ELIDABLE
         return 'calldescr-%d' % oopspecindex
     def calldescr_canraise(self, calldescr):
         return False
diff --git a/pypy/jit/codewriter/test/test_policy.py b/pypy/jit/codewriter/test/test_policy.py
--- a/pypy/jit/codewriter/test/test_policy.py
+++ b/pypy/jit/codewriter/test/test_policy.py
@@ -45,8 +45,8 @@
     policy.set_supports_floats(False)
     assert not policy.look_inside_graph(graph)
 
-def test_purefunction():
-    @jit.purefunction
+def test_elidable():
+    @jit.elidable
     def g(x):
         return x + 2
     graph = support.getgraph(g, [5])
diff --git a/pypy/jit/metainterp/compile.py b/pypy/jit/metainterp/compile.py
--- a/pypy/jit/metainterp/compile.py
+++ b/pypy/jit/metainterp/compile.py
@@ -3,7 +3,7 @@
 from pypy.rpython.ootypesystem import ootype
 from pypy.objspace.flow.model import Constant, Variable
 from pypy.rlib.objectmodel import we_are_translated
-from pypy.rlib.debug import debug_start, debug_stop
+from pypy.rlib.debug import debug_start, debug_stop, debug_print
 from pypy.rlib import rstack
 from pypy.conftest import option
 from pypy.tool.sourcetools import func_with_new_name
@@ -119,6 +119,7 @@
         old_loop_token = optimize_loop(metainterp_sd, old_loop_tokens, loop,
                                        jitdriver_sd.warmstate.enable_opts)
     except InvalidLoop:
+        debug_print("compile_new_loop: got an InvalidLoop")
         return None
     if old_loop_token is not None:
         metainterp.staticdata.log("reusing old loop")
@@ -633,6 +634,7 @@
                                             new_loop, state.enable_opts,
                                             inline_short_preamble, retraced)
     except InvalidLoop:
+        debug_print("compile_new_bridge: got an InvalidLoop")
         # XXX I am fairly convinced that optimize_bridge cannot actually raise
         # InvalidLoop
         return None
diff --git a/pypy/jit/metainterp/history.py b/pypy/jit/metainterp/history.py
--- a/pypy/jit/metainterp/history.py
+++ b/pypy/jit/metainterp/history.py
@@ -765,6 +765,7 @@
     """
     short_preamble = None
     failed_states = None
+    retraced_count = 0
     terminating = False # see TerminatingLoopToken in compile.py
     outermost_jitdriver_sd = None
     # and more data specified by the backend when the loop is compiled
diff --git a/pypy/jit/metainterp/optimizeopt/intbounds.py b/pypy/jit/metainterp/optimizeopt/intbounds.py
--- a/pypy/jit/metainterp/optimizeopt/intbounds.py
+++ b/pypy/jit/metainterp/optimizeopt/intbounds.py
@@ -382,6 +382,18 @@
                     v1.intbound.make_gt(IntBound(0, 0))
                     self.propagate_bounds_backward(op.getarg(0))
 
+    def propagate_bounds_INT_IS_ZERO(self, op):
+        r = self.getvalue(op.result)
+        if r.is_constant():
+            if r.box.same_constant(CONST_1):
+                v1 = self.getvalue(op.getarg(0))
+                # Clever hack, we can't use self.make_constant_int yet because
+                # the args aren't in the values dictionary yet so it runs into
+                # an assert, this is a clever way of expressing the same thing.
+                v1.intbound.make_ge(IntBound(0, 0))
+                v1.intbound.make_lt(IntBound(1, 1))
+                self.propagate_bounds_backward(op.getarg(0))
+
     def propagate_bounds_INT_ADD(self, op):
         v1 = self.getvalue(op.getarg(0))
         v2 = self.getvalue(op.getarg(1))
diff --git a/pypy/jit/metainterp/optimizeopt/test/test_optimizebasic.py b/pypy/jit/metainterp/optimizeopt/test/test_optimizebasic.py
--- a/pypy/jit/metainterp/optimizeopt/test/test_optimizebasic.py
+++ b/pypy/jit/metainterp/optimizeopt/test/test_optimizebasic.py
@@ -439,6 +439,23 @@
         """
         self.optimize_loop(ops, expected)
 
+    def test_int_is_zero_int_is_true(self):
+        ops = """
+        [i0]
+        i1 = int_is_zero(i0)
+        guard_true(i1) []
+        i2 = int_is_true(i0)
+        guard_false(i2) []
+        jump(i0)
+        """
+        expected = """
+        [i0]
+        i1 = int_is_zero(i0)
+        guard_true(i1) []
+        jump(0)
+        """
+        self.optimize_loop(ops, expected)
+
     def test_ooisnull_oononnull_2(self):
         ops = """
         [p0]
diff --git a/pypy/jit/metainterp/optimizeopt/unroll.py b/pypy/jit/metainterp/optimizeopt/unroll.py
--- a/pypy/jit/metainterp/optimizeopt/unroll.py
+++ b/pypy/jit/metainterp/optimizeopt/unroll.py
@@ -546,7 +546,7 @@
             effectinfo = descr.get_extra_info()
             if effectinfo is not None:
                 if effectinfo.extraeffect == EffectInfo.EF_LOOPINVARIANT or \
-                   effectinfo.extraeffect == EffectInfo.EF_PURE:
+                   effectinfo.extraeffect == EffectInfo.EF_ELIDABLE:
                     return True
         return False
     
@@ -676,24 +676,28 @@
                             jumpop = self.optimizer.newoperations.pop()
                             assert jumpop.getopnum() == rop.JUMP
                             for guard in extra_guards:
-                                descr = sh.start_resumedescr.clone_if_mutable()
-                                self.inliner.inline_descr_inplace(descr)
-                                guard.setdescr(descr)
+                                d = sh.start_resumedescr.clone_if_mutable()
+                                self.inliner.inline_descr_inplace(d)
+                                guard.setdescr(d)
                                 self.emit_operation(guard)
                             self.optimizer.newoperations.append(jumpop)
                         return
-                retraced_count = len(short)
-                if descr.failed_states:
-                    retraced_count += len(descr.failed_states)
+                retraced_count = descr.retraced_count
+                descr.retraced_count += 1
                 limit = self.optimizer.metainterp_sd.warmrunnerdesc.memory_manager.retrace_limit
                 if not self.retraced and retraced_count<limit:
                     if not descr.failed_states:
+                        debug_print("Retracing (%d of %d)" % (retraced_count,
+                                                              limit))
                         raise RetraceLoop
                     for failed in descr.failed_states:
                         if failed.generalization_of(virtual_state):
                             # Retracing once more will most likely fail again
                             break
                     else:
+                        debug_print("Retracing (%d of %d)" % (retraced_count,
+                                                              limit))
+                                                              
                         raise RetraceLoop
                 else:
                     if not descr.failed_states:
diff --git a/pypy/jit/metainterp/pyjitpl.py b/pypy/jit/metainterp/pyjitpl.py
--- a/pypy/jit/metainterp/pyjitpl.py
+++ b/pypy/jit/metainterp/pyjitpl.py
@@ -867,7 +867,7 @@
         any_operation = len(self.metainterp.history.operations) > 0
         jitdriver_sd = self.metainterp.staticdata.jitdrivers_sd[jdindex]
         self.verify_green_args(jitdriver_sd, greenboxes)
-        self.debug_merge_point(jdindex, self.metainterp.in_recursion,
+        self.debug_merge_point(jitdriver_sd, jdindex, self.metainterp.in_recursion,
                                greenboxes)
 
         if self.metainterp.seen_loop_header_for_jdindex < 0:
@@ -914,8 +914,10 @@
                                     assembler_call=True)
             raise ChangeFrame
 
-    def debug_merge_point(self, jd_index, in_recursion, greenkey):
+    def debug_merge_point(self, jitdriver_sd, jd_index, in_recursion, greenkey):
         # debugging: produce a DEBUG_MERGE_POINT operation
+        loc = jitdriver_sd.warmstate.get_location_str(greenkey)
+        debug_print(loc)
         args = [ConstInt(jd_index), ConstInt(in_recursion)] + greenkey
         self.metainterp.history.record(rop.DEBUG_MERGE_POINT, args, None)
 
@@ -1231,7 +1233,7 @@
             effect = effectinfo.extraeffect
             if effect == effectinfo.EF_CANNOT_RAISE:
                 return self.execute_varargs(rop.CALL, allboxes, descr, False)
-            elif effect == effectinfo.EF_PURE:
+            elif effect == effectinfo.EF_ELIDABLE:
                 return self.metainterp.record_result_of_call_pure(
                     self.execute_varargs(rop.CALL, allboxes, descr, False))
             elif effect == effectinfo.EF_LOOPINVARIANT:
diff --git a/pypy/jit/metainterp/test/test_ajit.py b/pypy/jit/metainterp/test/test_ajit.py
--- a/pypy/jit/metainterp/test/test_ajit.py
+++ b/pypy/jit/metainterp/test/test_ajit.py
@@ -1,7 +1,7 @@
 import py
 import sys
 from pypy.rlib.jit import JitDriver, we_are_jitted, hint, dont_look_inside
-from pypy.rlib.jit import loop_invariant
+from pypy.rlib.jit import loop_invariant, elidable, promote
 from pypy.rlib.jit import jit_debug, assert_green, AssertGreenFailed
 from pypy.rlib.jit import unroll_safe, current_trace_length
 from pypy.jit.metainterp import pyjitpl, history
@@ -304,12 +304,12 @@
         assert res == 42
         self.check_operations_history(int_add=1, int_mul=0, call=1, guard_no_exception=0)
 
-    def test_residual_call_pure(self):
+    def test_residual_call_elidable(self):
         def externfn(x, y):
             return x * y
-        externfn._pure_function_ = True
+        externfn._elidable_function_ = True
         def f(n):
-            n = hint(n, promote=True)
+            promote(n)
             return externfn(n, n+1)
         res = self.interp_operations(f, [6])
         assert res == 42
@@ -317,10 +317,10 @@
         self.check_operations_history(int_add=0, int_mul=0,
                                       call=0, call_pure=0)
 
-    def test_residual_call_pure_1(self):
+    def test_residual_call_elidable_1(self):
+        @elidable
         def externfn(x, y):
             return x * y
-        externfn._pure_function_ = True
         def f(n):
             return externfn(n, n+1)
         res = self.interp_operations(f, [6])
@@ -329,11 +329,11 @@
         self.check_operations_history(int_add=1, int_mul=0,
                                       call=0, call_pure=1)
 
-    def test_residual_call_pure_2(self):
+    def test_residual_call_elidable_2(self):
         myjitdriver = JitDriver(greens = [], reds = ['n'])
+        @elidable
         def externfn(x):
             return x - 1
-        externfn._pure_function_ = True
         def f(n):
             while n > 0:
                 myjitdriver.can_enter_jit(n=n)
@@ -346,11 +346,11 @@
         # by optimizeopt.py
         self.check_loops(int_sub=0, call=1, call_pure=0)
 
-    def test_constfold_call_pure(self):
+    def test_constfold_call_elidable(self):
         myjitdriver = JitDriver(greens = ['m'], reds = ['n'])
+        @elidable
         def externfn(x):
             return x - 3
-        externfn._pure_function_ = True
         def f(n, m):
             while n > 0:
                 myjitdriver.can_enter_jit(n=n, m=m)
@@ -362,11 +362,11 @@
         # the CALL_PURE is constant-folded away by optimizeopt.py
         self.check_loops(int_sub=1, call=0, call_pure=0)
 
-    def test_constfold_call_pure_2(self):
+    def test_constfold_call_elidable_2(self):
         myjitdriver = JitDriver(greens = ['m'], reds = ['n'])
+        @elidable
         def externfn(x):
             return x - 3
-        externfn._pure_function_ = True
         class V:
             def __init__(self, value):
                 self.value = value
@@ -382,19 +382,19 @@
         # the CALL_PURE is constant-folded away by optimizeopt.py
         self.check_loops(int_sub=1, call=0, call_pure=0)
 
-    def test_pure_function_returning_object(self):
+    def test_elidable_function_returning_object(self):
         myjitdriver = JitDriver(greens = ['m'], reds = ['n'])
         class V:
             def __init__(self, x):
                 self.x = x
         v1 = V(1)
         v2 = V(2)
+        @elidable
         def externfn(x):
             if x:
                 return v1
             else:
                 return v2
-        externfn._pure_function_ = True
         def f(n, m):
             while n > 0:
                 myjitdriver.can_enter_jit(n=n, m=m)
@@ -1252,7 +1252,7 @@
                 myjitdriver.jit_merge_point(x=x, l=l)
                 a = l[x]
                 x = a.g(x)
-                hint(a, promote=True)
+                promote(a)
             return x
         res = self.meta_interp(f, [299], listops=True)
         assert res == f(299)
@@ -1312,7 +1312,7 @@
                     x -= 5
                 else:
                     x -= 7
-                hint(a, promote=True)
+                promote(a)
             return x
         res = self.meta_interp(f, [299], listops=True)
         assert res == f(299)
@@ -1343,7 +1343,7 @@
                     x -= 5
                 else:
                     x -= 7
-                hint(a, promote=True)
+                promote(a)
             return x
         res = self.meta_interp(f, [299], listops=True)
         assert res == f(299)
@@ -1377,7 +1377,7 @@
                     x = a.g(x)
                 else:
                     x -= 7
-                hint(a, promote=True)
+                promote(a)
             return x
         res = self.meta_interp(f, [399], listops=True)
         assert res == f(399)
@@ -1496,7 +1496,7 @@
                     glob.a = B()
                     const = 2
                 else:
-                    const = hint(const, promote=True)
+                    promote(const)
                     x -= const
                     res += a.x
                     a = None
@@ -1531,7 +1531,7 @@
                 myjitdriver.can_enter_jit(x=x)
                 myjitdriver.jit_merge_point(x=x)
                 a = A()
-                hint(a, promote=True)
+                promote(a)
                 x -= 1
         self.meta_interp(f, [50])
         self.check_loop_count(1)
@@ -1595,9 +1595,9 @@
         self.check_loops(jit_debug=2)
 
     def test_assert_green(self):
-        def f(x, promote):
-            if promote:
-                x = hint(x, promote=True)
+        def f(x, promote_flag):
+            if promote_flag:
+                promote(x)
             assert_green(x)
             return x
         res = self.interp_operations(f, [8, 1])
@@ -1676,8 +1676,8 @@
             return a1.val + b1.val
         res = self.meta_interp(g, [6, 14])
         assert res == g(6, 14)
-        self.check_loop_count(9)
-        self.check_loops(getarrayitem_gc=8, everywhere=True)
+        self.check_loop_count(8)
+        self.check_loops(getarrayitem_gc=7, everywhere=True)
         py.test.skip("for the following, we need setarrayitem(varindex)")
         self.check_loops(getarrayitem_gc=6, everywhere=True)
 
@@ -1817,7 +1817,7 @@
             while y > 0:
                 myjitdriver.can_enter_jit(y=y, x=x, res=res, const=const)
                 myjitdriver.jit_merge_point(y=y, x=x, res=res, const=const)
-                const = hint(const, promote=True)
+                const = promote(const)
                 res = res.binop(A(const))
                 if y<7:
                     res = x
@@ -2002,7 +2002,7 @@
             n = sa = 0
             while n < 10:
                 myjitdriver.jit_merge_point(a=a, b=b, n=n, sa=sa)
-                if 0 < a < hint(sys.maxint/2, promote=True): pass
+                if 0 < a < promote(sys.maxint/2): pass
                 if 0 < b < 100: pass
                 sa += (((((a << b) << b) << b) >> b) >> b) >> b                
                 n += 1
@@ -2047,7 +2047,7 @@
             n = sa = 0
             while n < 10:
                 myjitdriver.jit_merge_point(a=a, b=b, n=n, sa=sa)
-                if -hint(sys.maxint/2, promote=True) < a < 0: pass
+                if -promote(sys.maxint/2) < a < 0: pass
                 if 0 < b < 100: pass
                 sa += (((((a << b) << b) << b) >> b) >> b) >> b                
                 n += 1
@@ -2082,7 +2082,7 @@
             n = sa = 0
             while n < 10:
                 myjitdriver.jit_merge_point(a=a, b=b, n=n, sa=sa)
-                if 0 < a < hint(sys.maxint/2, promote=True): pass
+                if 0 < a < promote(sys.maxint/2): pass
                 if 0 < b < 100: pass
                 sa += (a << b) >> b
                 n += 1
@@ -2139,7 +2139,7 @@
                 if op == 'j':
                     j += 1
                 elif op == 'c':
-                    c = hint(c, promote=True)
+                    promote(c)
                     c = 1 - c
                 elif op == '2':
                     if j < 3:
@@ -2208,7 +2208,8 @@
                 self.local_names[0] = 1
 
             def retrieve(self):
-                variables = hint(self.variables, promote=True)
+                variables = self.variables
+                promote(variables)
                 result = self.local_names[0]
                 if result == 0:
                     return -1
@@ -2313,6 +2314,67 @@
         assert res == -2
         #self.check_loops(getarrayitem_gc=0, setarrayitem_gc=0) -- xxx?
 
+    def test_retrace_ending_up_retrazing_another_loop(self):
+
+        myjitdriver = JitDriver(greens = ['pc'], reds = ['n', 'i', 'sa'])
+        bytecode = "0+sI0+SI"
+        def f(n):
+            myjitdriver.set_param('threshold', 3)
+            myjitdriver.set_param('trace_eagerness', 1)
+            myjitdriver.set_param('retrace_limit', 5)
+            myjitdriver.set_param('function_threshold', -1)
+            pc = sa = i = 0
+            while pc < len(bytecode):
+                myjitdriver.jit_merge_point(pc=pc, n=n, sa=sa, i=i)
+                n = hint(n, promote=True)
+                op = bytecode[pc]
+                if op == '0':
+                    i = 0
+                elif op == '+':
+                    i += 1
+                elif op == 's':
+                    sa += i
+                elif op == 'S':
+                    sa += 2
+                elif op == 'I':
+                    if i < n:
+                        pc -= 2
+                        myjitdriver.can_enter_jit(pc=pc, n=n, sa=sa, i=i)
+                        continue
+                pc += 1
+            return sa
+
+        def g(n1, n2):
+            for i in range(10):
+                f(n1)
+            for i in range(10):                
+                f(n2)
+
+        nn = [10, 3]
+        assert self.meta_interp(g, nn) == g(*nn)
+        
+        # The attempts of retracing first loop will end up retracing the
+        # second and thus fail 5 times, saturating the retrace_count. Instead a
+        # bridge back to the preamble of the first loop is produced. A guard in
+        # this bridge is later traced resulting in a retrace of the second loop.
+        # Thus we end up with:
+        #   1 preamble and 1 specialized version of first loop
+        #   1 preamble and 2 specialized version of second loop
+        self.check_tree_loop_count(2 + 3)
+
+        # FIXME: Add a gloabl retrace counter and test that we are not trying more than 5 times.
+        
+        def g(n):
+            for i in range(n):
+                for j in range(10):
+                    f(n-i)
+
+        res = self.meta_interp(g, [10])
+        assert res == g(10)
+        # 1 preamble and 6 speciealized versions of each loop
+        self.check_tree_loop_count(2*(1 + 6))
+
+
 class TestOOtype(BasicTests, OOJitMixin):
 
     def test_oohash(self):
diff --git a/pypy/jit/metainterp/test/test_fficall.py b/pypy/jit/metainterp/test/test_fficall.py
--- a/pypy/jit/metainterp/test/test_fficall.py
+++ b/pypy/jit/metainterp/test/test_fficall.py
@@ -1,7 +1,7 @@
 
 import py
 from pypy.rlib.rarithmetic import r_singlefloat, r_longlong, r_ulonglong
-from pypy.rlib.jit import JitDriver, hint, dont_look_inside
+from pypy.rlib.jit import JitDriver, promote, dont_look_inside
 from pypy.rlib.unroll import unrolling_iterable
 from pypy.rlib.libffi import ArgChain, longlong2float, float2longlong
 from pypy.rlib.libffi import IS_32_BIT
@@ -49,8 +49,7 @@
             res = init_result
             while n < 10:
                 driver.jit_merge_point(n=n, res=res, func=func)
-                driver.can_enter_jit(n=n, res=res, func=func)
-                func = hint(func, promote=True)
+                promote(func)
                 argchain = ArgChain()
                 # this loop is unrolled
                 for method_name, argval in method_and_args:
diff --git a/pypy/jit/metainterp/test/test_jitprof.py b/pypy/jit/metainterp/test/test_jitprof.py
--- a/pypy/jit/metainterp/test/test_jitprof.py
+++ b/pypy/jit/metainterp/test/test_jitprof.py
@@ -1,6 +1,6 @@
 
 from pypy.jit.metainterp.warmspot import ll_meta_interp
-from pypy.rlib.jit import JitDriver, dont_look_inside, purefunction
+from pypy.rlib.jit import JitDriver, dont_look_inside, elidable
 from pypy.jit.metainterp.test.support import LLJitMixin
 from pypy.jit.metainterp import pyjitpl
 from pypy.jit.metainterp.jitprof import *
@@ -89,7 +89,7 @@
         assert profiler.calls == 1
 
     def test_blackhole_pure(self):
-        @purefunction
+        @elidable
         def g(n):
             return n+1
         
diff --git a/pypy/jit/metainterp/test/test_recursive.py b/pypy/jit/metainterp/test/test_recursive.py
--- a/pypy/jit/metainterp/test/test_recursive.py
+++ b/pypy/jit/metainterp/test/test_recursive.py
@@ -1,6 +1,6 @@
 import py
 from pypy.rlib.jit import JitDriver, we_are_jitted, hint
-from pypy.rlib.jit import unroll_safe, dont_look_inside
+from pypy.rlib.jit import unroll_safe, dont_look_inside, promote
 from pypy.rlib.objectmodel import we_are_translated
 from pypy.rlib.debug import fatalerror
 from pypy.jit.metainterp.test.support import LLJitMixin, OOJitMixin
@@ -926,7 +926,7 @@
                 myjitdriver.can_enter_jit(codeno=codeno, frame=frame, n=n, x=x)
                 myjitdriver.jit_merge_point(codeno=codeno, frame=frame, n=n,
                                             x=x)
-                frame.s = hint(frame.s, promote=True)
+                frame.s = promote(frame.s)
                 n -= 1
                 s = frame.s
                 assert s >= 0
diff --git a/pypy/jit/metainterp/test/test_send.py b/pypy/jit/metainterp/test/test_send.py
--- a/pypy/jit/metainterp/test/test_send.py
+++ b/pypy/jit/metainterp/test/test_send.py
@@ -1,5 +1,5 @@
 import py
-from pypy.rlib.jit import JitDriver, hint, purefunction
+from pypy.rlib.jit import JitDriver, promote, elidable
 from pypy.jit.codewriter.policy import StopAtXPolicy
 from pypy.jit.metainterp.test.support import LLJitMixin, OOJitMixin
 
@@ -604,7 +604,7 @@
     def test_constfold_pure_oosend(self):
         myjitdriver = JitDriver(greens=[], reds = ['i', 'obj'])
         class A:
-            @purefunction
+            @elidable
             def foo(self):
                 return 42
         def fn(n, i):
@@ -613,7 +613,7 @@
             while i > 0:
                 myjitdriver.can_enter_jit(i=i, obj=obj)
                 myjitdriver.jit_merge_point(i=i, obj=obj)
-                obj = hint(obj, promote=True)
+                promote(obj)
                 res = obj.foo()
                 i-=1
             return res
diff --git a/pypy/jit/metainterp/test/test_virtual.py b/pypy/jit/metainterp/test/test_virtual.py
--- a/pypy/jit/metainterp/test/test_virtual.py
+++ b/pypy/jit/metainterp/test/test_virtual.py
@@ -1,5 +1,5 @@
 import py
-from pypy.rlib.jit import JitDriver, hint
+from pypy.rlib.jit import JitDriver, promote
 from pypy.rlib.objectmodel import compute_unique_id
 from pypy.jit.codewriter.policy import StopAtXPolicy
 from pypy.jit.metainterp.test.support import LLJitMixin, OOJitMixin
@@ -300,7 +300,7 @@
             while n > 0:
                 myjitdriver.can_enter_jit(n=n, i=i, stufflist=stufflist)
                 myjitdriver.jit_merge_point(n=n, i=i, stufflist=stufflist)
-                i = hint(i, promote=True)
+                promote(i)
                 v = Stuff(i)
                 n -= stufflist.lst[v.x].x
             return n
diff --git a/pypy/jit/metainterp/test/test_virtualizable.py b/pypy/jit/metainterp/test/test_virtualizable.py
--- a/pypy/jit/metainterp/test/test_virtualizable.py
+++ b/pypy/jit/metainterp/test/test_virtualizable.py
@@ -5,7 +5,7 @@
 from pypy.rpython.rclass import IR_IMMUTABLE, IR_IMMUTABLE_ARRAY
 from pypy.jit.codewriter.policy import StopAtXPolicy
 from pypy.jit.codewriter import heaptracker
-from pypy.rlib.jit import JitDriver, hint, dont_look_inside
+from pypy.rlib.jit import JitDriver, hint, dont_look_inside, promote
 from pypy.rlib.rarithmetic import intmask
 from pypy.jit.metainterp.test.support import LLJitMixin, OOJitMixin
 from pypy.rpython.rclass import FieldListAccessor
@@ -480,7 +480,7 @@
             while n > 0:
                 myjitdriver.can_enter_jit(frame=frame, n=n, x=x)
                 myjitdriver.jit_merge_point(frame=frame, n=n, x=x)
-                frame.s = hint(frame.s, promote=True)
+                frame.s = promote(frame.s)
                 n -= 1
                 s = frame.s
                 assert s >= 0
diff --git a/pypy/jit/tl/spli/interpreter.py b/pypy/jit/tl/spli/interpreter.py
--- a/pypy/jit/tl/spli/interpreter.py
+++ b/pypy/jit/tl/spli/interpreter.py
@@ -2,7 +2,7 @@
 from pypy.tool import stdlib_opcode
 from pypy.jit.tl.spli import objects, pycode
 from pypy.rlib.unroll import unrolling_iterable
-from pypy.rlib.jit import JitDriver, hint, dont_look_inside
+from pypy.rlib.jit import JitDriver, promote, dont_look_inside
 from pypy.rlib.objectmodel import we_are_translated
 
 opcode_method_names = stdlib_opcode.host_bytecode_spec.method_names
@@ -78,7 +78,7 @@
         while True:
             jitdriver.jit_merge_point(code=code, instr_index=instr_index,
                                       frame=self)
-            self.stack_depth = hint(self.stack_depth, promote=True)
+            self.stack_depth = promote(self.stack_depth)
             op = ord(code[instr_index])
             instr_index += 1
             if op >= HAVE_ARGUMENT:
diff --git a/pypy/jit/tl/tiny2.py b/pypy/jit/tl/tiny2.py
--- a/pypy/jit/tl/tiny2.py
+++ b/pypy/jit/tl/tiny2.py
@@ -27,7 +27,7 @@
     { #1 #1 1 SUB ->#1 #1 }    => when called with 5, gives '5 4 3 2 1'
 
 """
-from pypy.rlib.jit import hint
+from pypy.rlib.jit import hint, promote
 
 #
 # See pypy/doc/jit.txt for a higher-level overview of the JIT techniques
@@ -75,9 +75,9 @@
     # ones.  The JIT compiler cannot look into indirect calls, but it
     # can analyze and inline the code in directly-called functions.
     y = stack.pop()
-    hint(y.__class__, promote=True)
+    promote(y.__class__)
     x = stack.pop()
-    hint(x.__class__, promote=True)
+    promote(x.__class__)
     try:
         z = IntBox(func_int(x.as_int(), y.as_int()))
     except ValueError:
@@ -108,7 +108,7 @@
     # doesn't have to worry about the 'args' list being unpredictably
     # modified.
     oldargs = args
-    argcount = hint(len(oldargs), promote=True)
+    argcount = promote(len(oldargs))
     args = []
     n = 0
     while n < argcount:
@@ -160,8 +160,7 @@
                 # read out of the 'loops' list will be a compile-time constant
                 # because it was pushed as a compile-time constant by the '{'
                 # case above into 'loops', which is a virtual list, so the
-                # promotion below is just a way to make the colors match.
-                pos = hint(pos, promote=True)
+                promote(pos)
         else:
             stack.append(StrBox(opcode))
     return stack
diff --git a/pypy/jit/tl/tiny2_hotpath.py b/pypy/jit/tl/tiny2_hotpath.py
--- a/pypy/jit/tl/tiny2_hotpath.py
+++ b/pypy/jit/tl/tiny2_hotpath.py
@@ -27,7 +27,7 @@
     { #1 #1 1 SUB ->#1 #1 }    => when called with 5, gives '5 4 3 2 1'
 
 """
-from pypy.rlib.jit import hint, JitDriver
+from pypy.rlib.jit import hint, promote, JitDriver
 
 #
 # See pypy/doc/jit.txt for a higher-level overview of the JIT techniques
@@ -77,9 +77,9 @@
     # ones.  The JIT compiler cannot look into indirect calls, but it
     # can analyze and inline the code in directly-called functions.
     stack, y = stack.pop()
-    hint(y.__class__, promote=True)
+    promote(y.__class__)
     stack, x = stack.pop()
-    hint(x.__class__, promote=True)
+    promote(x.__class__)
     try:
         z = IntBox(func_int(x.as_int(), y.as_int()))
     except ValueError:
@@ -120,7 +120,7 @@
         # modified.
         oldloops = invariants
         oldargs = reds.args
-        argcount = hint(len(oldargs), promote=True)
+        argcount = promote(len(oldargs))
         args = []
         n = 0
         while n < argcount:
@@ -189,7 +189,7 @@
                 # because it was pushed as a compile-time constant by the '{'
                 # case above into 'loops', which is a virtual list, so the
                 # promotion below is just a way to make the colors match.
-                pos = hint(pos, promote=True)
+                pos = promote(pos)
                 tinyjitdriver.can_enter_jit(args=args, loops=loops, stack=stack,
                                             bytecode=bytecode, pos=pos)
         else:
diff --git a/pypy/jit/tl/tiny3_hotpath.py b/pypy/jit/tl/tiny3_hotpath.py
--- a/pypy/jit/tl/tiny3_hotpath.py
+++ b/pypy/jit/tl/tiny3_hotpath.py
@@ -28,7 +28,7 @@
     { #1 #1 1 SUB ->#1 #1 }    => when called with 5, gives '5 4 3 2 1'
 
 """
-from pypy.rlib.jit import hint, JitDriver
+from pypy.rlib.jit import promote, hint, JitDriver
 from pypy.rlib.objectmodel import specialize
 
 #
@@ -83,9 +83,9 @@
     # ones.  The JIT compiler cannot look into indirect calls, but it
     # can analyze and inline the code in directly-called functions.
     stack, y = stack.pop()
-    hint(y.__class__, promote=True)
+    promote(y.__class__)
     stack, x = stack.pop()
-    hint(x.__class__, promote=True)
+    promote(x.__class__)
     if isinstance(x, IntBox) and isinstance(y, IntBox):
         z = IntBox(func_int(x.as_int(), y.as_int()))
     else:
@@ -125,7 +125,7 @@
         # modified.
         oldloops = invariants
         oldargs = reds.args
-        argcount = hint(len(oldargs), promote=True)
+        argcount = promote(len(oldargs))
         args = []
         n = 0
         while n < argcount:
@@ -194,7 +194,7 @@
                 # because it was pushed as a compile-time constant by the '{'
                 # case above into 'loops', which is a virtual list, so the
                 # promotion below is just a way to make the colors match.
-                pos = hint(pos, promote=True)
+                pos = promote(pos)
                 tinyjitdriver.can_enter_jit(args=args, loops=loops, stack=stack,
                                             bytecode=bytecode, pos=pos)
         else:
diff --git a/pypy/jit/tl/tl.py b/pypy/jit/tl/tl.py
--- a/pypy/jit/tl/tl.py
+++ b/pypy/jit/tl/tl.py
@@ -2,7 +2,7 @@
 
 import py
 from pypy.jit.tl.tlopcode import *
-from pypy.rlib.jit import JitDriver, hint, dont_look_inside
+from pypy.rlib.jit import JitDriver, hint, dont_look_inside, promote
 
 def char2int(c):
     t = ord(c)
@@ -81,7 +81,7 @@
             myjitdriver.jit_merge_point(pc=pc, code=code,
                                         stack=stack, inputarg=inputarg)
             opcode = ord(code[pc])
-            stack.stackpos = hint(stack.stackpos, promote=True)
+            stack.stackpos = promote(stack.stackpos)
             pc += 1
 
             if opcode == NOP:
diff --git a/pypy/jit/tl/tlc.py b/pypy/jit/tl/tlc.py
--- a/pypy/jit/tl/tlc.py
+++ b/pypy/jit/tl/tlc.py
@@ -5,7 +5,7 @@
 from pypy.rlib.objectmodel import specialize, we_are_translated
 from pypy.jit.tl.tlopcode import *
 from pypy.jit.tl import tlopcode
-from pypy.rlib.jit import JitDriver
+from pypy.rlib.jit import JitDriver, elidable
 
 class Obj(object):
 
@@ -71,6 +71,7 @@
 
     classes = [] # [(descr, cls), ...]
 
+    @elidable
     def get(key):
         for descr, cls in Class.classes:
             if key.attributes == descr.attributes and\
@@ -79,7 +80,6 @@
         result = Class(key)
         Class.classes.append((key, result))
         return result
-    get._pure_function_ = True
     get = staticmethod(get)
 
     def __init__(self, descr):
diff --git a/pypy/module/__builtin__/__init__.py b/pypy/module/__builtin__/__init__.py
--- a/pypy/module/__builtin__/__init__.py
+++ b/pypy/module/__builtin__/__init__.py
@@ -5,20 +5,6 @@
 
 # put builtins here that should be optimized somehow
 
-OPTIMIZED_BUILTINS = ["len", "range", "xrange", "min", "max", "enumerate",
-        "isinstance", "type", "zip", "file", "format", "open", "abs", "chr",
-        "unichr", "ord", "pow", "repr", "hash", "oct", "hex", "round", "cmp",
-        "getattr", "setattr", "delattr", "callable", "int", "str", "float"]
-
-assert len(OPTIMIZED_BUILTINS) <= 256
-
-BUILTIN_TO_INDEX = {}
-
-for i, name in enumerate(OPTIMIZED_BUILTINS):
-    BUILTIN_TO_INDEX[name] = i
-
-assert len(OPTIMIZED_BUILTINS) == len(BUILTIN_TO_INDEX)
-
 class Module(MixedModule):
     """Built-in functions, exceptions, and other objects."""
     expose__file__attribute = False
@@ -141,9 +127,6 @@
     def setup_after_space_initialization(self):
         """NOT_RPYTHON"""
         space = self.space
-        self.builtins_by_index = [None] * len(OPTIMIZED_BUILTINS)
-        for i, name in enumerate(OPTIMIZED_BUILTINS):
-            self.builtins_by_index[i] = space.getattr(self, space.wrap(name))
         # install the more general version of isinstance() & co. in the space
         from pypy.module.__builtin__ import abstractinst as ab
         space.abstract_isinstance_w = ab.abstract_isinstance_w.__get__(space)
diff --git a/pypy/module/__builtin__/test/test_builtin.py b/pypy/module/__builtin__/test/test_builtin.py
--- a/pypy/module/__builtin__/test/test_builtin.py
+++ b/pypy/module/__builtin__/test/test_builtin.py
@@ -631,62 +631,6 @@
         raises(TypeError, pr, end=3)
         raises(TypeError, pr, sep=42)
 
-class AppTestBuiltinOptimized(object):
-    def setup_class(cls):
-        from pypy.conftest import gettestobjspace
-        cls.space = gettestobjspace(**{"objspace.opcodes.CALL_LIKELY_BUILTIN": True})
-
-    # hum, we need to invoke the compiler explicitely
-    def test_xrange_len(self):
-        s = """def test():
-        x = xrange(33)
-        assert len(x) == 33
-        x = xrange(33.2)
-        assert len(x) == 33
-        x = xrange(33,0,-1)
-        assert len(x) == 33
-        x = xrange(33,0)
-        assert len(x) == 0
-        x = xrange(33,0.2)
-        assert len(x) == 0
-        x = xrange(0,33)
-        assert len(x) == 33
-        x = xrange(0,33,-1)
-        assert len(x) == 0
-        x = xrange(0,33,2)
-        assert len(x) == 17
-        x = xrange(0,32,2)
-        assert len(x) == 16
-        """
-        ns = {}
-        exec s in ns
-        ns["test"]()
-
-    def test_delete_from_builtins(self):
-        s = """ """
-        # XXX write this test!
-
-    def test_shadow_case_bound_method(self):
-        s = """def test(l):
-        n = len(l)
-        old_len = len
-        class A(object):
-            x = 5
-            def length(self, o):
-                return self.x*old_len(o)
-        import __builtin__
-        __builtin__.len = A().length
-        try:
-            m = len(l)
-        finally:
-            __builtin__.len = old_len
-        return n+m
-        """
-        ns = {}
-        exec s in ns
-        res = ns["test"]([2,3,4])
-        assert res == 18
-
     def test_round(self):
         assert round(11.234) == 11.0
         assert round(11.234, -1) == 10.0
diff --git a/pypy/module/__builtin__/test/test_classobj.py b/pypy/module/__builtin__/test/test_classobj.py
--- a/pypy/module/__builtin__/test/test_classobj.py
+++ b/pypy/module/__builtin__/test/test_classobj.py
@@ -987,9 +987,9 @@
         if option.runappdirect:
             py.test.skip("can only be run on py.py")
         def is_strdict(space, w_class):
-            from pypy.objspace.std.dictmultiobject import StrDictImplementation
+            from pypy.objspace.std.dictmultiobject import StringDictStrategy
             w_d = w_class.getdict(space)
-            return space.wrap(isinstance(w_d, StrDictImplementation) and w_d.r_dict_content is None)
+            return space.wrap(isinstance(w_d.strategy, StringDictStrategy))
 
         cls.w_is_strdict = cls.space.wrap(gateway.interp2app(is_strdict))
 
diff --git a/pypy/module/_ffi/interp_ffi.py b/pypy/module/_ffi/interp_ffi.py
--- a/pypy/module/_ffi/interp_ffi.py
+++ b/pypy/module/_ffi/interp_ffi.py
@@ -235,7 +235,7 @@
         argchain.arg_longlong(floatval)
 
     def call(self, space, args_w):
-        self = jit.hint(self, promote=True)
+        self = jit.promote(self)
         argchain = self.build_argchain(space, args_w)
         w_restype = self.w_restype
         if w_restype.is_longlong():
diff --git a/pypy/module/_lsprof/interp_lsprof.py b/pypy/module/_lsprof/interp_lsprof.py
--- a/pypy/module/_lsprof/interp_lsprof.py
+++ b/pypy/module/_lsprof/interp_lsprof.py
@@ -149,7 +149,7 @@
                             factor * float(self.ll_it), w_sublist)
         return space.wrap(w_se)
 
-    @jit.purefunction
+    @jit.elidable
     def _get_or_make_subentry(self, entry, make=True):
         try:
             return self.calls[entry]
@@ -167,7 +167,7 @@
         self.previous = profobj.current_context
         entry.recursionLevel += 1
         if profobj.subcalls and self.previous:
-            caller = jit.hint(self.previous.entry, promote=True)
+            caller = jit.promote(self.previous.entry)
             subentry = caller._get_or_make_subentry(entry)
             subentry.recursionLevel += 1
         self.ll_t0 = profobj.ll_timer()
@@ -179,7 +179,7 @@
             self.previous.ll_subt += tt
         entry._stop(tt, it)
         if profobj.subcalls and self.previous:
-            caller = jit.hint(self.previous.entry, promote=True)
+            caller = jit.promote(self.previous.entry)
             subentry = caller._get_or_make_subentry(entry, False)
             if subentry is not None:
                 subentry._stop(tt, it)
@@ -282,7 +282,7 @@
         c_setup_profiling()
         space.getexecutioncontext().setllprofile(lsprof_call, space.wrap(self))
 
-    @jit.purefunction
+    @jit.elidable
     def _get_or_make_entry(self, f_code, make=True):
         try:
             return self.data[f_code]
@@ -293,7 +293,7 @@
                 return entry
             return None
 
-    @jit.purefunction
+    @jit.elidable
     def _get_or_make_builtin_entry(self, key, make=True):
         try:
             return self.builtin_data[key]
@@ -306,7 +306,7 @@
 
     def _enter_call(self, f_code):
         # we have a superb gc, no point in freelist :)
-        self = jit.hint(self, promote=True)
+        self = jit.promote(self)
         entry = self._get_or_make_entry(f_code)
         self.current_context = ProfilerContext(self, entry)
 
@@ -314,14 +314,14 @@
         context = self.current_context
         if context is None:
             return
-        self = jit.hint(self, promote=True)
+        self = jit.promote(self)
         entry = self._get_or_make_entry(f_code, False)
         if entry is not None:
             context._stop(self, entry)
         self.current_context = context.previous
 
     def _enter_builtin_call(self, key):
-        self = jit.hint(self, promote=True)
+        self = jit.promote(self)
         entry = self._get_or_make_builtin_entry(key)
         self.current_context = ProfilerContext(self, entry)
 
@@ -329,7 +329,7 @@
         context = self.current_context
         if context is None:
             return
-        self = jit.hint(self, promote=True)
+        self = jit.promote(self)
         entry = self._get_or_make_builtin_entry(key, False)
         if entry is not None:
             context._stop(self, entry)
diff --git a/pypy/module/_lsprof/test/test_cprofile.py b/pypy/module/_lsprof/test/test_cprofile.py
--- a/pypy/module/_lsprof/test/test_cprofile.py
+++ b/pypy/module/_lsprof/test/test_cprofile.py
@@ -181,8 +181,7 @@
 
 
 class AppTestWithDifferentBytecodes(AppTestCProfile):
-    keywords = {'objspace.opcodes.CALL_LIKELY_BUILTIN': True,
-                'objspace.opcodes.CALL_METHOD': True}
+    keywords = {'objspace.opcodes.CALL_METHOD': True}
 
 
 expected_output = {}
diff --git a/pypy/module/cpyext/api.py b/pypy/module/cpyext/api.py
--- a/pypy/module/cpyext/api.py
+++ b/pypy/module/cpyext/api.py
@@ -562,7 +562,8 @@
             elif callable.api_func.restype is not lltype.Void:
                 retval = rffi.cast(callable.api_func.restype, result)
         except Exception, e:
-            print 'Fatal error in cpyext, calling', callable.__name__
+            print 'Fatal error in cpyext, CPython compatibility layer, calling', callable.__name__
+            print 'Either report a bug or consider not using this particular extension'
             if not we_are_translated():
                 import traceback
                 traceback.print_exc()
diff --git a/pypy/module/imp/importing.py b/pypy/module/imp/importing.py
--- a/pypy/module/imp/importing.py
+++ b/pypy/module/imp/importing.py
@@ -120,7 +120,7 @@
 def check_sys_modules_w(space, modulename):
     return space.finditem_str(space.sys.get('modules'), modulename)
 
- at jit.purefunction
+ at jit.elidable
 def _get_dot_position(str, n):
     # return the index in str of the '.' such that there are n '.'-separated
     # strings after it
@@ -133,8 +133,8 @@
 def _get_relative_name(space, modulename, level, w_globals):
     w = space.wrap
     ctxt_w_package = space.finditem_str(w_globals, '__package__')
-    ctxt_w_package = jit.hint(ctxt_w_package, promote=True)
-    level = jit.hint(level, promote=True)
+    ctxt_w_package = jit.promote(ctxt_w_package)
+    level = jit.promote(level)
 
     ctxt_package = None
     if ctxt_w_package is not None and ctxt_w_package is not space.w_None:
@@ -184,7 +184,7 @@
         ctxt_w_name = space.finditem_str(w_globals, '__name__')
         ctxt_w_path = space.finditem_str(w_globals, '__path__')
 
-        ctxt_w_name = jit.hint(ctxt_w_name, promote=True)
+        ctxt_w_name = jit.promote(ctxt_w_name)
         ctxt_name = None
         if ctxt_w_name is not None:
             try:
@@ -799,14 +799,13 @@
 
 """
 
-# XXX picking a magic number is a mess.  So far it works because we
-# have only two extra opcodes, which bump the magic number by +1 and
-# +2 respectively, and CPython leaves a gap of 10 when it increases
+# picking a magic number is a mess.  So far it works because we
+# have only one extra opcode, which bumps the magic number by +2, and CPython
+# leaves a gap of 10 when it increases
 # its own magic number.  To avoid assigning exactly the same numbers
 # as CPython we always add a +2.  We'll have to think again when we
-# get at the fourth new opcode :-(
+# get three more new opcodes
 #
-#  * CALL_LIKELY_BUILTIN    +1
 #  * CALL_METHOD            +2
 #
 # In other words:
@@ -829,8 +828,6 @@
             return struct.unpack('<i', magic)[0]
 
     result = default_magic
-    if space.config.objspace.opcodes.CALL_LIKELY_BUILTIN:
-        result += 1
     if space.config.objspace.opcodes.CALL_METHOD:
         result += 2
     return result
diff --git a/pypy/module/pyexpat/__init__.py b/pypy/module/pyexpat/__init__.py
--- a/pypy/module/pyexpat/__init__.py
+++ b/pypy/module/pyexpat/__init__.py
@@ -2,6 +2,22 @@
 
 from pypy.interpreter.mixedmodule import MixedModule
 
+class ErrorsModule(MixedModule):
+    "Definition of pyexpat.errors module."
+
+    appleveldefs = {
+        }
+
+    interpleveldefs = {
+        }
+
+    def setup_after_space_initialization(self):
+        from pypy.module.pyexpat import interp_pyexpat
+        for name in interp_pyexpat.xml_error_list:
+            self.space.setattr(self, self.space.wrap(name),
+                    interp_pyexpat.ErrorString(self.space,
+                    getattr(interp_pyexpat, name)))
+
 class Module(MixedModule):
     "Python wrapper for Expat parser."
 
@@ -21,6 +37,10 @@
         'version_info':  'interp_pyexpat.get_expat_version_info(space)',
         }
 
+    submodules = {
+        'errors': ErrorsModule,
+    }
+
     for name in ['XML_PARAM_ENTITY_PARSING_NEVER',
                  'XML_PARAM_ENTITY_PARSING_UNLESS_STANDALONE',
                  'XML_PARAM_ENTITY_PARSING_ALWAYS']:
diff --git a/pypy/module/pyexpat/interp_pyexpat.py b/pypy/module/pyexpat/interp_pyexpat.py
--- a/pypy/module/pyexpat/interp_pyexpat.py
+++ b/pypy/module/pyexpat/interp_pyexpat.py
@@ -31,6 +31,48 @@
 XML_Content_Ptr = lltype.Ptr(lltype.ForwardReference())
 XML_Parser = rffi.COpaquePtr(typedef='XML_Parser')
 
+xml_error_list = [
+    "XML_ERROR_NO_MEMORY",
+    "XML_ERROR_SYNTAX",
+    "XML_ERROR_NO_ELEMENTS",
+    "XML_ERROR_INVALID_TOKEN",
+    "XML_ERROR_UNCLOSED_TOKEN",
+    "XML_ERROR_PARTIAL_CHAR",
+    "XML_ERROR_TAG_MISMATCH",
+    "XML_ERROR_DUPLICATE_ATTRIBUTE",
+    "XML_ERROR_JUNK_AFTER_DOC_ELEMENT",
+    "XML_ERROR_PARAM_ENTITY_REF",
+    "XML_ERROR_UNDEFINED_ENTITY",
+    "XML_ERROR_RECURSIVE_ENTITY_REF",
+    "XML_ERROR_ASYNC_ENTITY",
+    "XML_ERROR_BAD_CHAR_REF",
+    "XML_ERROR_BINARY_ENTITY_REF",
+    "XML_ERROR_ATTRIBUTE_EXTERNAL_ENTITY_REF",
+    "XML_ERROR_MISPLACED_XML_PI",
+    "XML_ERROR_UNKNOWN_ENCODING",
+    "XML_ERROR_INCORRECT_ENCODING",
+    "XML_ERROR_UNCLOSED_CDATA_SECTION",
+    "XML_ERROR_EXTERNAL_ENTITY_HANDLING",
+    "XML_ERROR_NOT_STANDALONE",
+    "XML_ERROR_UNEXPECTED_STATE",
+    "XML_ERROR_ENTITY_DECLARED_IN_PE",
+    "XML_ERROR_FEATURE_REQUIRES_XML_DTD",
+    "XML_ERROR_CANT_CHANGE_FEATURE_ONCE_PARSING",
+    # Added in Expat 1.95.7.
+    "XML_ERROR_UNBOUND_PREFIX",
+    # Added in Expat 1.95.8.
+    "XML_ERROR_UNDECLARING_PREFIX",
+    "XML_ERROR_INCOMPLETE_PE",
+    "XML_ERROR_XML_DECL",
+    "XML_ERROR_TEXT_DECL",
+    "XML_ERROR_PUBLICID",
+    "XML_ERROR_SUSPENDED",
+    "XML_ERROR_NOT_SUSPENDED",
+    "XML_ERROR_ABORTED",
+    "XML_ERROR_FINISHED",
+    "XML_ERROR_SUSPEND_PE",
+    ]
+
 class CConfigure:
     _compilation_info_ = eci
     XML_Content = rffi_platform.Struct('XML_Content', [
@@ -56,6 +98,9 @@
     XML_FALSE = rffi_platform.ConstantInteger('XML_FALSE')
     XML_TRUE = rffi_platform.ConstantInteger('XML_TRUE')
 
+    for name in xml_error_list:
+        locals()[name] = rffi_platform.ConstantInteger(name)
+
 for k, v in rffi_platform.configure(CConfigure).items():
     globals()[k] = v
 
@@ -298,7 +343,8 @@
 XML_GetErrorCode = expat_external(
     'XML_GetErrorCode', [XML_Parser], rffi.INT)
 XML_ErrorString = expat_external(
-    'XML_ErrorString', [rffi.INT], rffi.CCHARP)
+    'XML_ErrorString', [rffi.INT],
+    rffi.CCHARP)
 XML_GetCurrentLineNumber = expat_external(
     'XML_GetCurrentLineNumber', [XML_Parser], rffi.INT)
 XML_GetErrorLineNumber = XML_GetCurrentLineNumber
diff --git a/pypy/module/pyexpat/test/test_parser.py b/pypy/module/pyexpat/test/test_parser.py
--- a/pypy/module/pyexpat/test/test_parser.py
+++ b/pypy/module/pyexpat/test/test_parser.py
@@ -38,7 +38,7 @@
         parser = pyexpat.ParserCreate()
         raises(pyexpat.ExpatError, "parser.Parse(xml, True)")
 
-    def test_encoding(self):
+    def test_encoding_argument(self):
         import pyexpat
         for encoding_arg in (None, 'utf-8', 'iso-8859-1'):
             for namespace_arg in (None, '{'):
@@ -68,7 +68,7 @@
         assert p.buffer_size == 150
         raises(TypeError, setattr, p, 'buffer_size', sys.maxint + 1)
 
-    def test_encoding(self):
+    def test_encoding_xml(self):
         # use one of the few encodings built-in in expat
         xml = "<?xml version='1.0' encoding='iso-8859-1'?><s>caf\xe9</s>"
         import pyexpat
@@ -120,3 +120,14 @@
             return True
         p.ExternalEntityRefHandler = handler
         p.Parse(xml)
+
+    def test_errors(self):
+        import types
+        import pyexpat
+        assert isinstance(pyexpat.errors, types.ModuleType)
+        # check a few random errors
+        assert pyexpat.errors.XML_ERROR_SYNTAX == 'syntax error'
+        assert (pyexpat.errors.XML_ERROR_INCORRECT_ENCODING ==
+               'encoding specified in XML declaration is incorrect')
+        assert (pyexpat.errors.XML_ERROR_XML_DECL ==
+                'XML declaration not well-formed')
diff --git a/pypy/module/pypyjit/policy.py b/pypy/module/pypyjit/policy.py
--- a/pypy/module/pypyjit/policy.py
+++ b/pypy/module/pypyjit/policy.py
@@ -15,7 +15,7 @@
         if modname in ['pypyjit', 'signal', 'micronumpy', 'math', 'exceptions',
                        'imp', 'sys', 'array', '_ffi', 'itertools', 'operator',
                        'posix', '_socket', '_sre', '_lsprof', '_weakref',
-                       '__pypy__']:
+                       '__pypy__', 'cStringIO']:
             return True
         return False
 
diff --git a/pypy/module/pypyjit/test_pypy_c/test_call.py b/pypy/module/pypyjit/test_pypy_c/test_call.py
--- a/pypy/module/pypyjit/test_pypy_c/test_call.py
+++ b/pypy/module/pypyjit/test_pypy_c/test_call.py
@@ -66,13 +66,13 @@
         ops = entry_bridge.ops_by_id('cond', opcode='LOAD_GLOBAL')
         assert log.opnames(ops) == ["guard_value",
                                     "getfield_gc", "guard_value",
-                                    "getfield_gc", "guard_isnull",
+                                    "getfield_gc", "guard_value",
                                     "getfield_gc", "guard_nonnull_class"]
         # LOAD_GLOBAL of OFFSET but in different function partially folded
         # away
         # XXX could be improved
         ops = entry_bridge.ops_by_id('add', opcode='LOAD_GLOBAL')
-        assert log.opnames(ops) == ["guard_value", "getfield_gc", "guard_isnull"]
+        assert log.opnames(ops) == ["guard_value", "getfield_gc", "guard_value"]
         #
         # two LOAD_GLOBAL of f, the second is folded away
         ops = entry_bridge.ops_by_id('call', opcode='LOAD_GLOBAL')
@@ -209,6 +209,26 @@
             i16 = force_token()
         """)
 
+    def test_kwargs_empty(self):
+        def main(x):
+            def g(**args):
+                return len(args) + 1
+            #
+            s = 0
+            d = {}
+            i = 0
+            while i < x:
+                s += g(**d)       # ID: call
+                i += 1
+            return s
+        #
+        log = self.run(main, [1000])
+        assert log.result == 1000
+        loop, = log.loops_by_id('call')
+        ops = log.opnames(loop.ops_by_id('call'))
+        guards = [ops for ops in ops if ops.startswith('guard')]
+        assert guards == ["guard_no_overflow"]
+
     def test_kwargs(self):
         # this is not a very precise test, could be improved
         def main(x):
@@ -216,20 +236,24 @@
                 return len(args)
             #
             s = 0
-            d = {}
-            for i in range(x):
+            d = {"a": 1}
+            i = 0
+            while i < x:
                 s += g(**d)       # ID: call
                 d[str(i)] = i
                 if i % 100 == 99:
-                    d = {}
+                    d = {"a": 1}
+                i += 1
             return s
         #
         log = self.run(main, [1000])
-        assert log.result == 49500
+        assert log.result == 50500
         loop, = log.loops_by_id('call')
+        print loop.ops_by_id('call')
         ops = log.opnames(loop.ops_by_id('call'))
         guards = [ops for ops in ops if ops.startswith('guard')]
-        assert len(guards) <= 5
+        print guards
+        assert len(guards) <= 20
 
     def test_stararg_virtual(self):
         def main(x):
diff --git a/pypy/module/pypyjit/test_pypy_c/test_containers.py b/pypy/module/pypyjit/test_pypy_c/test_containers.py
new file mode 100644
--- /dev/null
+++ b/pypy/module/pypyjit/test_pypy_c/test_containers.py
@@ -0,0 +1,25 @@
+
+import py, sys
+from pypy.module.pypyjit.test_pypy_c.test_00_model import BaseTestPyPyC
+
+
+class TestDicts(BaseTestPyPyC):
+    def test_strdict(self):
+        def fn(n):
+            import sys
+            d = {}
+            class A(object):
+                pass
+            a = A()
+            a.x = 1
+            for s in sys.modules.keys() * 1000:
+                inc = a.x # ID: look
+                d[s] = d.get(s, 0) + inc
+            return sum(d.values())
+        #
+        log = self.run(fn, [1000])
+        assert log.result % 1000 == 0
+        loop, = log.loops_by_filename(self.filepath)
+        ops = loop.ops_by_id('look')
+        assert log.opnames(ops) == ['setfield_gc',
+                                    'guard_not_invalidated']
diff --git a/pypy/module/pypyjit/test_pypy_c/test_instance.py b/pypy/module/pypyjit/test_pypy_c/test_instance.py
--- a/pypy/module/pypyjit/test_pypy_c/test_instance.py
+++ b/pypy/module/pypyjit/test_pypy_c/test_instance.py
@@ -115,7 +115,7 @@
         # ----------------------
         loop, = log.loops_by_filename(self.filepath)
         assert loop.match("""
-            i9 = int_lt(i8, i7)
+            i9 = int_lt(i7, i8)
             guard_true(i9, descr=.*)
             guard_not_invalidated(descr=.*)
             i11 = int_add(i8, 1)
@@ -124,7 +124,7 @@
             p20 = new_with_vtable(ConstClass(W_IntObject))
             setfield_gc(p20, i11, descr=<SignedFieldDescr.*W_IntObject.inst_intval .*>)
             setfield_gc(ConstPtr(ptr21), p20, descr=<GcPtrFieldDescr .*TypeCell.inst_w_value .*>)
-            jump(p0, p1, p2, p3, p4, p20, p6, i11, i7, descr=<Loop.>)
+            jump(p0, p1, p2, p3, p4, p20, p6, i11, i8, descr=<Loop.>)
         """)
 
     def test_oldstyle_newstyle_mix(self):
diff --git a/pypy/module/signal/interp_signal.py b/pypy/module/signal/interp_signal.py
--- a/pypy/module/signal/interp_signal.py
+++ b/pypy/module/signal/interp_signal.py
@@ -80,7 +80,7 @@
 
 pypysig_getaddr_occurred = external('pypysig_getaddr_occurred', [],
                                     lltype.Ptr(LONG_STRUCT), _nowrapper=True,
-                                    pure_function=True)
+                                    elidable_function=True)
 c_alarm = external('alarm', [rffi.INT], rffi.INT)
 c_pause = external('pause', [], rffi.INT)
 c_siginterrupt = external('siginterrupt', [rffi.INT, rffi.INT], rffi.INT)
diff --git a/pypy/objspace/flow/operation.py b/pypy/objspace/flow/operation.py
--- a/pypy/objspace/flow/operation.py
+++ b/pypy/objspace/flow/operation.py
@@ -143,9 +143,6 @@
 def mod_ovf(x, y):
     return ovfcheck(x % y)
 
-##def pow_ovf(*two_or_three_args):
-##    return ovfcheck(pow(*two_or_three_args))
-
 def lshift_ovf(x, y):
     return ovfcheck_lshift(x, y)
 
diff --git a/pypy/objspace/std/celldict.py b/pypy/objspace/std/celldict.py
--- a/pypy/objspace/std/celldict.py
+++ b/pypy/objspace/std/celldict.py
@@ -4,8 +4,9 @@
 speed up global lookups a lot."""
 
 from pypy.objspace.std.dictmultiobject import IteratorImplementation
-from pypy.objspace.std.dictmultiobject import W_DictMultiObject, _is_sane_hash
-from pypy.rlib import jit
+from pypy.objspace.std.dictmultiobject import DictStrategy, _never_equal_to_string
+from pypy.objspace.std.dictmultiobject import ObjectDictStrategy
+from pypy.rlib import jit, rerased
 
 class ModuleCell(object):
     def __init__(self, w_value=None):
@@ -19,49 +20,59 @@
     def __repr__(self):
         return "<ModuleCell: %s>" % (self.w_value, )
 
-class ModuleDictImplementation(W_DictMultiObject):
+class ModuleDictStrategy(DictStrategy):
+
+    erase, unerase = rerased.new_erasing_pair("modulecell")
+    erase = staticmethod(erase)
+    unerase = staticmethod(unerase)
+
     def __init__(self, space):
         self.space = space
-        self.content = {}
 
-    def getcell(self, key, makenew):
+    def get_empty_storage(self):
+       return self.erase({})
+
+    def getcell(self, w_dict, key, makenew):
         if makenew or jit.we_are_jitted():
             # when we are jitting, we always go through the pure function
             # below, to ensure that we have no residual dict lookup
-            self = jit.hint(self, promote=True)
-            return self._getcell_makenew(key)
-        return self.content.get(key, None)
+            w_dict = jit.promote(w_dict)
+            self = jit.promote(self)
+            return self._getcell_makenew(w_dict, key)
+        return self.unerase(w_dict.dstorage).get(key, None)
 
-    @jit.purefunction
-    def _getcell_makenew(self, key):
-        return self.content.setdefault(key, ModuleCell())
+    @jit.elidable
+    def _getcell_makenew(self, w_dict, key):
+        return self.unerase(w_dict.dstorage).setdefault(key, ModuleCell())
 
-    def impl_setitem(self, w_key, w_value):
+    def setitem(self, w_dict, w_key, w_value):
         space = self.space
         if space.is_w(space.type(w_key), space.w_str):
-            self.impl_setitem_str(self.space.str_w(w_key), w_value)
+            self.setitem_str(w_dict, self.space.str_w(w_key), w_value)
         else:
-            self._as_rdict().impl_fallback_setitem(w_key, w_value)
+            self.switch_to_object_strategy(w_dict)
+            w_dict.setitem(w_key, w_value)
 
-    def impl_setitem_str(self, name, w_value):
-        self.getcell(name, True).w_value = w_value
+    def setitem_str(self, w_dict, key, w_value):
+        self.getcell(w_dict, key, True).w_value = w_value
 
-    def impl_setdefault(self, w_key, w_default):
+    def setdefault(self, w_dict, w_key, w_default):
         space = self.space
         if space.is_w(space.type(w_key), space.w_str):
-            cell = self.getcell(space.str_w(w_key), True)
+            cell = self.getcell(w_dict, space.str_w(w_key), True)
             if cell.w_value is None:
                 cell.w_value = w_default
             return cell.w_value
         else:
-            return self._as_rdict().impl_fallback_setdefault(w_key, w_default)
+            self.switch_to_object_strategy(w_dict)
+            return w_dict.setdefault(w_key, w_default)
 
-    def impl_delitem(self, w_key):
+    def delitem(self, w_dict, w_key):
         space = self.space
         w_key_type = space.type(w_key)
         if space.is_w(w_key_type, space.w_str):
             key = space.str_w(w_key)
-            cell = self.getcell(key, False)
+            cell = self.getcell(w_dict, key, False)
             if cell is None or cell.w_value is None:
                 raise KeyError
             # note that we don't remove the cell from self.content, to make
@@ -69,75 +80,91 @@
             # maps to the same cell later (even if this cell no longer
             # represents a key)
             cell.invalidate()
-        elif _is_sane_hash(space, w_key_type):
+        elif _never_equal_to_string(space, w_key_type):
             raise KeyError
         else:
-            self._as_rdict().impl_fallback_delitem(w_key)
-        
-    def impl_length(self):
+            self.switch_to_object_strategy(w_dict)
+            w_dict.delitem(w_key)
+
+    def length(self, w_dict):
         # inefficient, but do we care?
         res = 0
-        for cell in self.content.itervalues():
+        for cell in self.unerase(w_dict.dstorage).itervalues():
             if cell.w_value is not None:
                 res += 1
         return res
 
-    def impl_getitem(self, w_lookup):
+    def getitem(self, w_dict, w_key):
         space = self.space
-        w_lookup_type = space.type(w_lookup)
+        w_lookup_type = space.type(w_key)
         if space.is_w(w_lookup_type, space.w_str):
-            return self.impl_getitem_str(space.str_w(w_lookup))
+            return self.getitem_str(w_dict, space.str_w(w_key))
 
-        elif _is_sane_hash(space, w_lookup_type):
+        elif _never_equal_to_string(space, w_lookup_type):
             return None
         else:
-            return self._as_rdict().impl_fallback_getitem(w_lookup)
+            self.switch_to_object_strategy(w_dict)
+            return w_dict.getitem(w_key)
 
-    def impl_getitem_str(self, lookup):
-        res = self.getcell(lookup, False)
+    def getitem_str(self, w_dict, key):
+        res = self.getcell(w_dict, key, False)
         if res is None:
             return None
         # note that even if the res.w_value is None, the next line is fine
         return res.w_value
 
-    def impl_iter(self):
-        return ModuleDictIteratorImplementation(self.space, self)
+    def iter(self, w_dict):
+        return ModuleDictIteratorImplementation(self.space, self, w_dict)
 
-    def impl_keys(self):
+    def keys(self, w_dict):
         space = self.space
-        return [space.wrap(key) for key, cell in self.content.iteritems()
+        iterator = self.unerase(w_dict.dstorage).iteritems
+        return [space.wrap(key) for key, cell in iterator()
                     if cell.w_value is not None]
 
-    def impl_values(self):
-        return [cell.w_value for cell in self.content.itervalues()
+    def values(self, w_dict):
+        iterator = self.unerase(w_dict.dstorage).itervalues
+        return [cell.w_value for cell in iterator()
                     if cell.w_value is not None]
 
-    def impl_items(self):
+    def items(self, w_dict):
         space = self.space
+        iterator = self.unerase(w_dict.dstorage).iteritems
         return [space.newtuple([space.wrap(key), cell.w_value])
-                    for (key, cell) in self.content.iteritems()
+                    for (key, cell) in iterator()
                         if cell.w_value is not None]
 
-    def impl_clear(self):
-        for k, cell in self.content.iteritems():
+    def clear(self, w_dict):
+        iterator = self.unerase(w_dict.dstorage).iteritems
+        for k, cell in iterator():
             cell.invalidate()
 
-    def _as_rdict(self):
-        r_dict_content = self.initialize_as_rdict()
-        for k, cell in self.content.iteritems():
+    def popitem(self, w_dict):
+        # This is O(n) if called repeatadly, you probably shouldn't be on a
+        # Module's dict though
+        for k, cell in self.unerase(w_dict.dstorage).iteritems():
             if cell.w_value is not None:
-                r_dict_content[self.space.wrap(k)] = cell.w_value
-            cell.invalidate()
-        self._clear_fields()
-        return self
+                w_value = cell.w_value
+                cell.invalidate()
+                return self.space.wrap(k), w_value
+        else:
+            raise KeyError
 
-    def _clear_fields(self):
-        self.content = None
+    def switch_to_object_strategy(self, w_dict):
+        d = self.unerase(w_dict.dstorage)
+        strategy = self.space.fromcache(ObjectDictStrategy)
+        d_new = strategy.unerase(strategy.get_empty_storage())
+        for key, cell in d.iteritems():
+            if cell.w_value is not None:
+                d_new[self.space.wrap(key)] = cell.w_value
+        w_dict.strategy = strategy
+        w_dict.dstorage = strategy.erase(d_new)
 
 class ModuleDictIteratorImplementation(IteratorImplementation):
-    def __init__(self, space, dictimplementation):
+    def __init__(self, space, strategy, dictimplementation):
         IteratorImplementation.__init__(self, space, dictimplementation)
-        self.iterator = dictimplementation.content.iteritems()
+        dict_w = strategy.unerase(dictimplementation.dstorage)
+        self.iterator = dict_w.iteritems()
 
     def next_entry(self):
         for key, cell in self.iterator:
diff --git a/pypy/objspace/std/dictmultiobject.py b/pypy/objspace/std/dictmultiobject.py
--- a/pypy/objspace/std/dictmultiobject.py
+++ b/pypy/objspace/std/dictmultiobject.py
@@ -1,18 +1,20 @@
 import py, sys
 from pypy.objspace.std.model import registerimplementation, W_Object
 from pypy.objspace.std.register_all import register_all
+from pypy.objspace.std.settype import set_typedef as settypedef
 from pypy.interpreter import gateway
 from pypy.interpreter.argument import Signature
 from pypy.interpreter.error import OperationError, operationerrfmt
-from pypy.module.__builtin__.__init__ import BUILTIN_TO_INDEX, OPTIMIZED_BUILTINS
 
-from pypy.rlib.objectmodel import r_dict, we_are_translated
-from pypy.objspace.std.settype import set_typedef as settypedef
+from pypy.rlib.objectmodel import r_dict, we_are_translated, specialize
+from pypy.rlib.debug import mark_dict_non_null
+
+from pypy.rlib import rerased
 
 def _is_str(space, w_key):
     return space.is_w(space.type(w_key), space.w_str)
 
-def _is_sane_hash(space, w_lookup_type):
+def _never_equal_to_string(space, w_lookup_type):
     """ Handles the case of a non string key lookup.
     Types that have a sane hash/eq function should allow us to return True
     directly to signal that the key is not in the dict in any case.
@@ -28,48 +30,38 @@
 class W_DictMultiObject(W_Object):
     from pypy.objspace.std.dicttype import dict_typedef as typedef
 
-    r_dict_content = None
-
     @staticmethod
     def allocate_and_init_instance(space, w_type=None, module=False,
                                    instance=False, classofinstance=None,
                                    strdict=False):
+
         if space.config.objspace.std.withcelldict and module:
-            from pypy.objspace.std.celldict import ModuleDictImplementation
+            from pypy.objspace.std.celldict import ModuleDictStrategy
             assert w_type is None
-            return ModuleDictImplementation(space)
-        elif space.config.objspace.opcodes.CALL_LIKELY_BUILTIN and module:
-            assert w_type is None
-            return WaryDictImplementation(space)
-        elif space.config.objspace.std.withdictmeasurement:
-            assert w_type is None
-            return MeasuringDictImplementation(space)
+            strategy = space.fromcache(ModuleDictStrategy)
+
         elif instance or strdict or module:
             assert w_type is None
-            return StrDictImplementation(space)
+            strategy = space.fromcache(StringDictStrategy)
+
         else:
-            if w_type is None:
-                w_type = space.w_dict
-            w_self = space.allocate_instance(W_DictMultiObject, w_type)
-            W_DictMultiObject.__init__(w_self, space)
-            return w_self
+            strategy = space.fromcache(EmptyDictStrategy)
 
-    def __init__(self, space):
+        if w_type is None:
+            w_type = space.w_dict
+        storage = strategy.get_empty_storage()
+        w_self = space.allocate_instance(W_DictMultiObject, w_type)
+        W_DictMultiObject.__init__(w_self, space, strategy, storage)
+        return w_self
+
+    def __init__(self, space, strategy, storage):
         self.space = space
-
-    def initialize_as_rdict(self):
-        assert self.r_dict_content is None
-        self.r_dict_content = r_dict(self.space.eq_w, self.space.hash_w)
-        return self.r_dict_content
-
-
-    def initialize_content(w_self, list_pairs_w):
-        for w_k, w_v in list_pairs_w:
-            w_self.setitem(w_k, w_v)
+        self.strategy = strategy
+        self.dstorage = storage
 
     def __repr__(w_self):
         """ representation for debugging purposes """
-        return "%s()" % (w_self.__class__.__name__, )
+        return "%s(%s)" % (w_self.__class__.__name__, w_self.strategy)
 
     def unwrap(w_dict, space):
         result = {}
@@ -88,51 +80,38 @@
         else:
             return None
 
-    # _________________________________________________________________
-    # implementation methods
-    def impl_getitem(self, w_key):
-        #return w_value or None
-        # in case the key is unhashable, try to hash it
-        self.space.hash(w_key)
-        # return None anyway
-        return None
+    def initialize_content(w_self, list_pairs_w):
+        for w_k, w_v in list_pairs_w:
+            w_self.setitem(w_k, w_v)
 
-    def impl_getitem_str(self, key):
-        #return w_value or None
-        return None
+def _add_indirections():
+    dict_methods = "setitem setitem_str getitem \
+                    getitem_str delitem length \
+                    clear keys values \
+                    items iter setdefault \
+                    popitem".split()
 
-    def impl_setdefault(self, w_key, w_default):
-        # here the dict is always empty
-        self._as_rdict().impl_fallback_setitem(w_key, w_default)
-        return w_default
+    def make_method(method):
+        def f(self, *args):
+            return getattr(self.strategy, method)(self, *args)
+        f.func_name = method
+        return f
 
-    def impl_setitem(self, w_key, w_value):
-        self._as_rdict().impl_fallback_setitem(w_key, w_value)
+    for method in dict_methods:
+        setattr(W_DictMultiObject, method, make_method(method))
 
-    def impl_setitem_str(self, key, w_value):
-        self._as_rdict().impl_fallback_setitem_str(key, w_value)
+_add_indirections()
 
-    def impl_delitem(self, w_key):
-        # in case the key is unhashable, try to hash it
-        self.space.hash(w_key)
-        raise KeyError
+class DictStrategy(object):
 
-    def impl_length(self):
-        return 0
+    def __init__(self, space):
+        self.space = space
 
-    def impl_iter(self):
-        # XXX I guess it's not important to be fast in this case?
-        return self._as_rdict().impl_fallback_iter()
+    def get_empty_storage(self):
+        raise NotImplementedError
 
-    def impl_clear(self):
-        self.r_dict_content = None
-
-    def _as_rdict(self):
-        r_dict_content = self.initialize_as_rdict()
-        return self
-
-    def impl_keys(self):
-        iterator = self.impl_iter()
+    def keys(self, w_dict):
+        iterator = self.iter(w_dict)
         result = []
         while 1:
             w_key, w_value = iterator.next()
@@ -140,8 +119,9 @@
                 result.append(w_key)
             else:
                 return result
-    def impl_values(self):
-        iterator = self.impl_iter()
+
+    def values(self, w_dict):
+        iterator = self.iter(w_dict)
         result = []
         while 1:
             w_key, w_value = iterator.next()
@@ -149,8 +129,9 @@
                 result.append(w_value)
             else:
                 return result
-    def impl_items(self):
-        iterator = self.impl_iter()
+
+    def items(self, w_dict):
+        iterator = self.iter(w_dict)
         result = []
         while 1:
             w_key, w_value = iterator.next()
@@ -159,106 +140,87 @@
             else:
                 return result
 
-    # the following method only makes sense when the option to use the
-    # CALL_LIKELY_BUILTIN opcode is set. Otherwise it won't even be seen
-    # by the annotator
-    def impl_get_builtin_indexed(self, i):
-        key = OPTIMIZED_BUILTINS[i]
-        return self.impl_getitem_str(key)
+    def clear(self, w_dict):
+        strategy = self.space.fromcache(EmptyDictStrategy)
+        storage = strategy.get_empty_storage()
+        w_dict.strategy = strategy
+        w_dict.dstorage = storage
 
-    def impl_popitem(self):
-        # default implementation
-        space = self.space
-        iterator = self.impl_iter()
-        w_key, w_value = iterator.next()
-        if w_key is None:
-            raise KeyError
-        self.impl_delitem(w_key)
-        return w_key, w_value
 
-    # _________________________________________________________________
-    # fallback implementation methods
+class EmptyDictStrategy(DictStrategy):
 
-    def impl_fallback_setdefault(self, w_key, w_default):
-        return self.r_dict_content.setdefault(w_key, w_default)
+    erase, unerase = rerased.new_erasing_pair("empty")
+    erase = staticmethod(erase)
+    unerase = staticmethod(unerase)
 
-    def impl_fallback_setitem(self, w_key, w_value):
-        self.r_dict_content[w_key] = w_value
+    def get_empty_storage(self):
+       return self.erase(None)
 
-    def impl_fallback_setitem_str(self, key, w_value):
-        return self.impl_fallback_setitem(self.space.wrap(key), w_value)
+    def switch_to_correct_strategy(self, w_dict, w_key):
+        #XXX implement other strategies later
+        if type(w_key) is self.space.StringObjectCls:
+            self.switch_to_string_strategy(w_dict)
+        elif self.space.is_w(self.space.type(w_key), self.space.w_int):
+            self.switch_to_int_strategy(w_dict)
+        else:
+            strategy = self.space.fromcache(ObjectDictStrategy)
+            storage = strategy.get_empty_storage()
+            w_dict.strategy = strategy
+            w_dict.dstorage = storage
 
-    def impl_fallback_delitem(self, w_key):
-        del self.r_dict_content[w_key]
+    def switch_to_string_strategy(self, w_dict):
+        strategy = self.space.fromcache(StringDictStrategy)
+        storage = strategy.get_empty_storage()
+        w_dict.strategy = strategy
+        w_dict.dstorage = storage
 
-    def impl_fallback_length(self):
-        return len(self.r_dict_content)
+    def switch_to_int_strategy(self, w_dict):
+        strategy = self.space.fromcache(IntDictStrategy)
+        storage = strategy.get_empty_storage()
+        w_dict.strategy = strategy
+        w_dict.dstorage = storage
 
-    def impl_fallback_getitem(self, w_key):
-        return self.r_dict_content.get(w_key, None)
+    def getitem(self, w_dict, w_key):
+        #return w_value or None
+        # in case the key is unhashable, try to hash it
+        self.space.hash(w_key)
+        # return None anyway
+        return None
 
-    def impl_fallback_getitem_str(self, key):
-        return self.r_dict_content.get(self.space.wrap(key), None)
+    def getitem_str(self, w_dict, key):
+        #return w_value or None
+        return None
 
-    def impl_fallback_iter(self):
-        return RDictIteratorImplementation(self.space, self)
+    def setdefault(self, w_dict, w_key, w_default):
+        # here the dict is always empty
+        self.switch_to_correct_strategy(w_dict, w_key)
+        w_dict.setitem(w_key, w_default)
+        return w_default
 
-    def impl_fallback_keys(self):
-        return self.r_dict_content.keys()
-    def impl_fallback_values(self):
-        return self.r_dict_content.values()
-    def impl_fallback_items(self):
-        return [self.space.newtuple([w_key, w_val])
-                    for w_key, w_val in self.r_dict_content.iteritems()]
+    def setitem(self, w_dict, w_key, w_value):
+        self.switch_to_correct_strategy(w_dict, w_key)
+        w_dict.setitem(w_key, w_value)
 
-    def impl_fallback_clear(self):
-        self.r_dict_content.clear()
+    def setitem_str(self, w_dict, key, w_value):
+        self.switch_to_string_strategy(w_dict)
+        w_dict.setitem_str(key, w_value)
 
-    def impl_fallback_get_builtin_indexed(self, i):
-        key = OPTIMIZED_BUILTINS[i]
-        return self.impl_fallback_getitem_str(key)
+    def delitem(self, w_dict, w_key):
+        # in case the key is unhashable, try to hash it
+        self.space.hash(w_key)
+        raise KeyError
 
-    def impl_fallback_popitem(self):
-        return self.r_dict_content.popitem()
+    def length(self, w_dict):
+        return 0
 
+    def iter(self, w_dict):
+        return EmptyIteratorImplementation(self.space, w_dict)
 
-implementation_methods = [
-    ("getitem", 1),
-    ("getitem_str", 1),
-    ("length", 0),
-    ("setitem_str", 2),
-    ("setitem", 2),
-    ("setdefault", 2),
-    ("delitem", 1),
-    ("iter", 0),
-    ("items", 0),
-    ("values", 0),
-    ("keys", 0),
-    ("clear", 0),
-    ("get_builtin_indexed", 1),
-    ("popitem", 0),
-]
+    def clear(self, w_dict):
+        return
 
-
-def _make_method(name, implname, fallback, numargs):
-    args = ", ".join(["a" + str(i) for i in range(numargs)])
-    code = """def %s(self, %s):
-        if self.r_dict_content is not None:
-            return self.%s(%s)
-        return self.%s(%s)""" % (name, args, fallback, args, implname, args)
-    d = {}
-    exec py.code.Source(code).compile() in d
-    implementation_method = d[name]
-    implementation_method.func_defaults = getattr(W_DictMultiObject, implname).func_defaults
-    return implementation_method
-
-def _install_methods():
-    for name, numargs in implementation_methods:
-        implname = "impl_" + name
-        fallbackname = "impl_fallback_" + name
-        func = _make_method(name, implname, fallbackname, numargs)
-        setattr(W_DictMultiObject, name, func)
-_install_methods()
+    def popitem(self, w_dict):
+        raise KeyError
 
 registerimplementation(W_DictMultiObject)
 
@@ -300,319 +262,255 @@
             return self.len - self.pos
         return 0
 
+class EmptyIteratorImplementation(IteratorImplementation):
+    def next(self):
+        return (None, None)
+
 
 
 # concrete subclasses of the above
 
-class StrDictImplementation(W_DictMultiObject):
-    def __init__(self, space):
-        self.space = space
-        self.content = {}
+class AbstractTypedStrategy(object):
+    _mixin_ = True
 
-    def impl_setitem(self, w_key, w_value):
+    @staticmethod
+    def erase(storage):
+        raise NotImplementedError("abstract base class")
+
+    @staticmethod
+    def unerase(obj):
+        raise NotImplementedError("abstract base class")
+
+    def wrap(self, unwrapped):
+        raise NotImplementedError
+
+    def unwrap(self, wrapped):
+        raise NotImplementedError
+
+    def is_correct_type(self, w_obj):
+        raise NotImplementedError("abstract base class")
+
+    def get_empty_storage(self):
+        raise NotImplementedError("abstract base class")
+
+    def _never_equal_to(self, w_lookup_type):
+        raise NotImplementedError("abstract base class")
+
+    def setitem(self, w_dict, w_key, w_value):
         space = self.space
-        if space.is_w(space.type(w_key), space.w_str):
-            self.impl_setitem_str(self.space.str_w(w_key), w_value)
+        if self.is_correct_type(w_key):
+            self.unerase(w_dict.dstorage)[self.unwrap(w_key)] = w_value
+            return
         else:
-            self._as_rdict().impl_fallback_setitem(w_key, w_value)
+            self.switch_to_object_strategy(w_dict)
+            w_dict.setitem(w_key, w_value)
 
-    def impl_setitem_str(self, key, w_value):
-        self.content[key] = w_value
+    def setitem_str(self, w_dict, key, w_value):
+        self.switch_to_object_strategy(w_dict)
+        w_dict.setitem(self.space.wrap(key), w_value)
 
-    def impl_setdefault(self, w_key, w_default):
+    def setdefault(self, w_dict, w_key, w_default):
         space = self.space
-        if space.is_w(space.type(w_key), space.w_str):
-            return self.content.setdefault(space.str_w(w_key), w_default)
+        if self.is_correct_type(w_key):
+            return self.unerase(w_dict.dstorage).setdefault(self.unwrap(w_key), w_default)
         else:
-            return self._as_rdict().impl_fallback_setdefault(w_key, w_default)
+            self.switch_to_object_strategy(w_dict)
+            return w_dict.setdefault(w_key, w_default)
 
-
-    def impl_delitem(self, w_key):
+    def delitem(self, w_dict, w_key):
         space = self.space
         w_key_type = space.type(w_key)
-        if space.is_w(w_key_type, space.w_str):
-            del self.content[space.str_w(w_key)]
+        if self.is_correct_type(w_key):
+            del self.unerase(w_dict.dstorage)[self.unwrap(w_key)]
             return
-        elif _is_sane_hash(space, w_key_type):
-            raise KeyError
         else:
-            self._as_rdict().impl_fallback_delitem(w_key)
+            self.switch_to_object_strategy(w_dict)
+            return w_dict.delitem(w_key)
 
-    def impl_length(self):
-        return len(self.content)
+    def length(self, w_dict):
+        return len(self.unerase(w_dict.dstorage))
 
-    def impl_getitem_str(self, key):
-        return self.content.get(key, None)
+    def getitem_str(self, w_dict, key):
+        return self.getitem(w_dict, self.space.wrap(key))
 
-    def impl_getitem(self, w_key):
+    def getitem(self, w_dict, w_key):
+        space = self.space
+
+        if self.is_correct_type(w_key):
+            return self.unerase(w_dict.dstorage).get(self.unwrap(w_key), None)
+        elif self._never_equal_to(space.type(w_key)):
+            return None
+        else:
+            self.switch_to_object_strategy(w_dict)
+            return w_dict.getitem(w_key)
+
+    def keys(self, w_dict):
+        return [self.wrap(key) for key in self.unerase(w_dict.dstorage).iterkeys()]
+
+    def values(self, w_dict):
+        return self.unerase(w_dict.dstorage).values()
+
+    def items(self, w_dict):
+        space = self.space
+        dict_w = self.unerase(w_dict.dstorage)
+        return [space.newtuple([self.wrap(key), w_value])
+                    for (key, w_value) in dict_w.iteritems()]
+
+    def popitem(self, w_dict):
+        key, value = self.unerase(w_dict.dstorage).popitem()
+        return (self.wrap(key), value)
+
+    def clear(self, w_dict):
+        self.unerase(w_dict.dstorage).clear()
+
+    def switch_to_object_strategy(self, w_dict):
+        d = self.unerase(w_dict.dstorage)
+        strategy = self.space.fromcache(ObjectDictStrategy)
+        d_new = strategy.unerase(strategy.get_empty_storage())
+        for key, value in d.iteritems():
+            d_new[self.wrap(key)] = value
+        w_dict.strategy = strategy
+        w_dict.dstorage = strategy.erase(d_new)
+
+class ObjectDictStrategy(AbstractTypedStrategy, DictStrategy):
+
+    erase, unerase = rerased.new_erasing_pair("object")
+    erase = staticmethod(erase)
+    unerase = staticmethod(unerase)
+
+    def wrap(self, unwrapped):
+        return unwrapped
+
+    def unwrap(self, wrapped):
+        return wrapped
+
+    def is_correct_type(self, w_obj):
+        return True
+
+    def get_empty_storage(self):
+       new_dict = r_dict(self.space.eq_w, self.space.hash_w,
+                         force_non_null=True)
+       return self.erase(new_dict)
+
+    def _never_equal_to(self, w_lookup_type):
+        return False
+
+    def iter(self, w_dict):
+        return ObjectIteratorImplementation(self.space, self, w_dict)
+
+    def keys(self, w_dict):
+        return self.unerase(w_dict.dstorage).keys()
+
+class StringDictStrategy(AbstractTypedStrategy, DictStrategy):
+
+    erase, unerase = rerased.new_erasing_pair("string")
+    erase = staticmethod(erase)
+    unerase = staticmethod(unerase)
+
+    def wrap(self, unwrapped):
+        return self.space.wrap(unwrapped)
+
+    def unwrap(self, wrapped):
+        return self.space.str_w(wrapped)
+
+    def is_correct_type(self, w_obj):
+        space = self.space
+        return space.is_w(space.type(w_obj), space.w_str)
+
+    def get_empty_storage(self):
+        res = {}
+        mark_dict_non_null(res)
+        return self.erase(res)
+
+    def _never_equal_to(self, w_lookup_type):
+        return _never_equal_to_string(self.space, w_lookup_type)
+
+    def setitem_str(self, w_dict, key, w_value):
+        assert key is not None
+        self.unerase(w_dict.dstorage)[key] = w_value
+
+    def getitem(self, w_dict, w_key):
         space = self.space
         # -- This is called extremely often.  Hack for performance --
         if type(w_key) is space.StringObjectCls:
-            return self.impl_getitem_str(w_key.unwrap(space))
+            return self.getitem_str(w_dict, w_key.unwrap(space))
         # -- End of performance hack --
-        w_lookup_type = space.type(w_key)
-        if space.is_w(w_lookup_type, space.w_str):
-            return self.impl_getitem_str(space.str_w(w_key))
-        elif _is_sane_hash(space, w_lookup_type):
-            return None
-        else:
-            return self._as_rdict().impl_fallback_getitem(w_key)
+        return AbstractTypedStrategy.getitem(self, w_dict, w_key)
 
-    def impl_iter(self):
-        return StrIteratorImplementation(self.space, self)
+    def getitem_str(self, w_dict, key):
+        assert key is not None
+        return self.unerase(w_dict.dstorage).get(key, None)
 
-    def impl_keys(self):
-        space = self.space
-        return [space.wrap(key) for key in self.content.iterkeys()]
+    def iter(self, w_dict):
+        return StrIteratorImplementation(self.space, self, w_dict)
 
-    def impl_values(self):
-        return self.content.values()
-
-    def impl_items(self):
-        space = self.space
-        return [space.newtuple([space.wrap(key), w_value])
-                    for (key, w_value) in self.content.iteritems()]
-
-    def impl_clear(self):
-        self.content.clear()
-
-
-    def _as_rdict(self):
-        r_dict_content = self.initialize_as_rdict()
-        for k, w_v in self.content.items():
-            r_dict_content[self.space.wrap(k)] = w_v
-        self._clear_fields()
-        return self
-
-    def _clear_fields(self):
-        self.content = None
 
 class StrIteratorImplementation(IteratorImplementation):
-    def __init__(self, space, dictimplementation):
+    def __init__(self, space, strategy, dictimplementation):
         IteratorImplementation.__init__(self, space, dictimplementation)
-        self.iterator = dictimplementation.content.iteritems()
+        self.iterator = strategy.unerase(dictimplementation.dstorage).iteritems()
 
     def next_entry(self):
         # note that this 'for' loop only runs once, at most
-        for str, w_value in self.iterator:
-            return self.space.wrap(str), w_value
+        for key, w_value in self.iterator:
+            return self.space.wrap(key), w_value
         else:
             return None, None
 
 
-class WaryDictImplementation(StrDictImplementation):
-    def __init__(self, space):
-        StrDictImplementation.__init__(self, space)
-        self.shadowed = [None] * len(BUILTIN_TO_INDEX)
+class IntDictStrategy(AbstractTypedStrategy, DictStrategy):
+    erase, unerase = rerased.new_erasing_pair("int")
+    erase = staticmethod(erase)
+    unerase = staticmethod(unerase)
 
-    def impl_setitem_str(self, key, w_value):
-        i = BUILTIN_TO_INDEX.get(key, -1)
-        if i != -1:
-            self.shadowed[i] = w_value
-        self.content[key] = w_value
+    def wrap(self, unwrapped):
+        return self.space.wrap(unwrapped)
 
-    def impl_delitem(self, w_key):
+    def unwrap(self, wrapped):
+        return self.space.int_w(wrapped)
+
+    def get_empty_storage(self):
+        return self.erase({})
+
+    def is_correct_type(self, w_obj):
         space = self.space
-        w_key_type = space.type(w_key)
-        if space.is_w(w_key_type, space.w_str):
-            key = space.str_w(w_key)
-            del self.content[key]
-            i = BUILTIN_TO_INDEX.get(key, -1)
-            if i != -1:
-                self.shadowed[i] = None
-        elif _is_sane_hash(space, w_key_type):
-            raise KeyError
-        else:
-            self._as_rdict().impl_fallback_delitem(w_key)
+        return space.is_w(space.type(w_obj), space.w_int)
 
-    def impl_get_builtin_indexed(self, i):
-        return self.shadowed[i]
+    def _never_equal_to(self, w_lookup_type):
+        space = self.space
+        # XXX there are many more types
+        return (space.is_w(w_lookup_type, space.w_NoneType) or
+                space.is_w(w_lookup_type, space.w_str) or
+                space.is_w(w_lookup_type, space.w_unicode)
+                )
 
+    def iter(self, w_dict):
+        return IntIteratorImplementation(self.space, self, w_dict)
 
-class RDictIteratorImplementation(IteratorImplementation):
-    def __init__(self, space, dictimplementation):
+class IntIteratorImplementation(IteratorImplementation):
+    def __init__(self, space, strategy, dictimplementation):
         IteratorImplementation.__init__(self, space, dictimplementation)
-        self.iterator = dictimplementation.r_dict_content.iteritems()
+        self.iterator = strategy.unerase(dictimplementation.dstorage).iteritems()
 
     def next_entry(self):
         # note that this 'for' loop only runs once, at most
-        for item in self.iterator:
-            return item
+        for key, w_value in self.iterator:
+            return self.space.wrap(key), w_value
         else:
             return None, None
 
 
+class ObjectIteratorImplementation(IteratorImplementation):
+    def __init__(self, space, strategy, dictimplementation):
+        IteratorImplementation.__init__(self, space, dictimplementation)
+        self.iterator = strategy.unerase(dictimplementation.dstorage).iteritems()
 
-# XXX fix this thing
-import time
-
-class DictInfo(object):
-    _dict_infos = []
-    def __init__(self):
-        self.id = len(self._dict_infos)
-
-        self.setitem_strs = 0; self.setitems = 0;  self.delitems = 0
-        self.lengths = 0;   self.gets = 0
-        self.iteritems = 0; self.iterkeys = 0; self.itervalues = 0
-        self.keys = 0;      self.values = 0;   self.items = 0
-
-        self.maxcontents = 0
-
-        self.reads = 0
-        self.hits = self.misses = 0
-        self.writes = 0
-        self.iterations = 0
-        self.listings = 0
-
-        self.seen_non_string_in_write = 0
-        self.seen_non_string_in_read_first = 0
-        self.size_on_non_string_seen_in_read = -1
-        self.size_on_non_string_seen_in_write = -1
-
-        self.createtime = time.time()
-        self.lifetime = -1.0
-
-        if not we_are_translated():
-            # very probable stack from here:
-            # 0 - us
-            # 1 - MeasuringDictImplementation.__init__
-            # 2 - W_DictMultiObject.__init__
-            # 3 - space.newdict
-            # 4 - newdict's caller.  let's look at that
-            try:
-                frame = sys._getframe(4)
-            except ValueError:
-                pass # might be at import time
-            else:
-                self.sig = '(%s:%s)%s'%(frame.f_code.co_filename, frame.f_lineno, frame.f_code.co_name)
-
-        self._dict_infos.append(self)
-    def __repr__(self):
-        args = []
-        for k in sorted(self.__dict__):
-            v = self.__dict__[k]
-            if v != 0:
-                args.append('%s=%r'%(k, v))
-        return '<DictInfo %s>'%(', '.join(args),)
-
-class OnTheWayOut:
-    def __init__(self, info):
-        self.info = info
-    def __del__(self):
-        self.info.lifetime = time.time() - self.info.createtime
-
-class MeasuringDictImplementation(W_DictMultiObject):
-    def __init__(self, space):
-        self.space = space
-        self.content = r_dict(space.eq_w, space.hash_w)
-        self.info = DictInfo()
-        self.thing_with_del = OnTheWayOut(self.info)
-
-    def __repr__(self):
-        return "%s<%s>" % (self.__class__.__name__, self.content)
-
-    def _is_str(self, w_key):
-        space = self.space
-        return space.is_true(space.isinstance(w_key, space.w_str))
-    def _read(self, w_key):
-        self.info.reads += 1
-        if not self.info.seen_non_string_in_write \
-               and not self.info.seen_non_string_in_read_first \
-               and not self._is_str(w_key):
-            self.info.seen_non_string_in_read_first = True
-            self.info.size_on_non_string_seen_in_read = len(self.content)
-        hit = w_key in self.content
-        if hit:
-            self.info.hits += 1
+    def next_entry(self):
+        # note that this 'for' loop only runs once, at most
+        for w_key, w_value in self.iterator:
+            return w_key, w_value
         else:
-            self.info.misses += 1
-
-    def impl_setitem(self, w_key, w_value):
-        if not self.info.seen_non_string_in_write and not self._is_str(w_key):
-            self.info.seen_non_string_in_write = True
-            self.info.size_on_non_string_seen_in_write = len(self.content)
-        self.info.setitems += 1
-        self.info.writes += 1
-        self.content[w_key] = w_value
-        self.info.maxcontents = max(self.info.maxcontents, len(self.content))
-    def impl_setitem_str(self, key, w_value):
-        self.info.setitem_strs += 1
-        self.impl_setitem(self.space.wrap(key), w_value)
-    def impl_delitem(self, w_key):
-        if not self.info.seen_non_string_in_write \
-               and not self.info.seen_non_string_in_read_first \
-               and not self._is_str(w_key):
-            self.info.seen_non_string_in_read_first = True
-            self.info.size_on_non_string_seen_in_read = len(self.content)
-        self.info.delitems += 1
-        self.info.writes += 1
-        del self.content[w_key]
-
-    def impl_length(self):
-        self.info.lengths += 1
-        return len(self.content)
-    def impl_getitem_str(self, key):
-        return self.impl_getitem(self.space.wrap(key))
-    def impl_getitem(self, w_key):
-        self.info.gets += 1
-        self._read(w_key)
-        return self.content.get(w_key, None)
-
-    def impl_iteritems(self):
-        self.info.iteritems += 1
-        self.info.iterations += 1
-        return RDictItemIteratorImplementation(self.space, self)
-    def impl_iterkeys(self):
-        self.info.iterkeys += 1
-        self.info.iterations += 1
-        return RDictKeyIteratorImplementation(self.space, self)
-    def impl_itervalues(self):
-        self.info.itervalues += 1
-        self.info.iterations += 1
-        return RDictValueIteratorImplementation(self.space, self)
-
-    def impl_keys(self):
-        self.info.keys += 1
-        self.info.listings += 1
-        return self.content.keys()
-    def impl_values(self):
-        self.info.values += 1
-        self.info.listings += 1
-        return self.content.values()
-    def impl_items(self):
-        self.info.items += 1
-        self.info.listings += 1
-        return [self.space.newtuple([w_key, w_val])
-                    for w_key, w_val in self.content.iteritems()]
-
-
-_example = DictInfo()
-del DictInfo._dict_infos[-1]
-tmpl = 'os.write(fd, "%(attr)s" + ": " + str(info.%(attr)s) + "\\n")'
-bodySrc = []
-for attr in sorted(_example.__dict__):
-    if attr == 'sig':
-        continue
-    bodySrc.append(tmpl%locals())
-exec py.code.Source('''
-from pypy.rlib.objectmodel import current_object_addr_as_int
-def _report_one(fd, info):
-    os.write(fd, "_address" + ": " + str(current_object_addr_as_int(info))
-                 + "\\n")
-    %s
-'''%'\n    '.join(bodySrc)).compile()
-
-def report():
-    if not DictInfo._dict_infos:
-        return
-    os.write(2, "Starting multidict report.\n")
-    fd = os.open('dictinfo.txt', os.O_CREAT|os.O_WRONLY|os.O_TRUNC, 0644)
-    for info in DictInfo._dict_infos:
-        os.write(fd, '------------------\n')
-        _report_one(fd, info)
-    os.close(fd)
-    os.write(2, "Reporting done.\n")
-
+            return None, None
 
 
 init_signature = Signature(['seq_or_map'], None, 'kwargs')
diff --git a/pypy/objspace/std/dictproxyobject.py b/pypy/objspace/std/dictproxyobject.py
--- a/pypy/objspace/std/dictproxyobject.py
+++ b/pypy/objspace/std/dictproxyobject.py
@@ -1,96 +1,98 @@
 from pypy.objspace.std.model import registerimplementation, W_Object
 from pypy.objspace.std.register_all import register_all
 from pypy.objspace.std.dictmultiobject import W_DictMultiObject, IteratorImplementation
+from pypy.objspace.std.dictmultiobject import DictStrategy
 from pypy.objspace.std.typeobject import unwrap_cell
 from pypy.interpreter.error import OperationError
 
+from pypy.rlib import rerased
 
-class W_DictProxyObject(W_DictMultiObject):
-    def __init__(w_self, space, w_type):
-        W_DictMultiObject.__init__(w_self, space)
-        w_self.w_type = w_type
 
-    def impl_getitem(self, w_lookup):
+class DictProxyStrategy(DictStrategy):
+
+    erase, unerase = rerased.new_erasing_pair("dictproxy")
+    erase = staticmethod(erase)
+    unerase = staticmethod(unerase)
+
+    def __init__(w_self, space):
+        DictStrategy.__init__(w_self, space)
+
+    def getitem(self, w_dict, w_key):
         space = self.space
-        w_lookup_type = space.type(w_lookup)
+        w_lookup_type = space.type(w_key)
         if space.is_w(w_lookup_type, space.w_str):
-            return self.impl_getitem_str(space.str_w(w_lookup))
+            return self.getitem_str(w_dict, space.str_w(w_key))
         else:
             return None
 
-    def impl_getitem_str(self, lookup):
-        return self.w_type.getdictvalue(self.space, lookup)
+    def getitem_str(self, w_dict, key):
+        return self.unerase(w_dict.dstorage).getdictvalue(self.space, key)
 
-    def impl_setitem(self, w_key, w_value):
+    def setitem(self, w_dict, w_key, w_value):
         space = self.space
         if space.is_w(space.type(w_key), space.w_str):
-            self.impl_setitem_str(self.space.str_w(w_key), w_value)
+            self.setitem_str(w_dict, self.space.str_w(w_key), w_value)
         else:
             raise OperationError(space.w_TypeError, space.wrap("cannot add non-string keys to dict of a type"))
 
-    def impl_setitem_str(self, name, w_value):
+    def setitem_str(self, w_dict, key, w_value):
+        w_type = self.unerase(w_dict.dstorage)
         try:
-            self.w_type.setdictvalue(self.space, name, w_value)
+            w_type.setdictvalue(self.space, key, w_value)
         except OperationError, e:
             if not e.match(self.space, self.space.w_TypeError):
                 raise
-            w_type = self.w_type
             if not w_type.is_cpytype():
                 raise
             # xxx obscure workaround: allow cpyext to write to type->tp_dict.
             # xxx like CPython, we assume that this is only done early after
             # xxx the type is created, and we don't invalidate any cache.
-            w_type.dict_w[name] = w_value
+            w_type.dict_w[key] = w_value
 
-    def impl_setdefault(self, w_key, w_default):
+    def setdefault(self, w_dict, w_key, w_default):
         space = self.space
-        w_result = self.impl_getitem(w_key)
+        w_result = self.getitem(w_dict, w_key)
         if w_result is not None:
             return w_result
-        self.impl_setitem(w_key, w_default)
+        self.setitem(w_dict, w_key, w_default)
         return w_default
 
-    def impl_delitem(self, w_key):
+    def delitem(self, w_dict, w_key):
         space = self.space
         w_key_type = space.type(w_key)
         if space.is_w(w_key_type, space.w_str):
-            if not self.w_type.deldictvalue(space, w_key):
+            if not self.unerase(w_dict.dstorage).deldictvalue(space, w_key):
                 raise KeyError
         else:
             raise KeyError
 
-    def impl_length(self):
-        return len(self.w_type.dict_w)
+    def length(self, w_dict):
+        return len(self.unerase(w_dict.dstorage).dict_w)
 
-    def impl_iter(self):
-        return DictProxyIteratorImplementation(self.space, self)
+    def iter(self, w_dict):
+        return DictProxyIteratorImplementation(self.space, self, w_dict)
 
-    def impl_keys(self):
+    def keys(self, w_dict):
         space = self.space
-        return [space.wrap(key) for key in self.w_type.dict_w.iterkeys()]
+        return [space.wrap(key) for key in self.unerase(w_dict.dstorage).dict_w.iterkeys()]
 
-    def impl_values(self):
-        return [unwrap_cell(self.space, w_value) for w_value in self.w_type.dict_w.itervalues()]
+    def values(self, w_dict):
+        return [unwrap_cell(self.space, w_value) for w_value in self.unerase(w_dict.dstorage).dict_w.itervalues()]
 
-    def impl_items(self):
+    def items(self, w_dict):
         space = self.space
         return [space.newtuple([space.wrap(key), unwrap_cell(self.space, w_value)])
-                    for (key, w_value) in self.w_type.dict_w.iteritems()]
+                    for (key, w_value) in self.unerase(w_dict.dstorage).dict_w.iteritems()]
 
-    def impl_clear(self):
-        self.w_type.dict_w.clear()
-        self.w_type.mutated()
-
-    def _as_rdict(self):
-        assert 0, "should be unreachable"
-
-    def _clear_fields(self):
-        assert 0, "should be unreachable"
+    def clear(self, w_dict):
+        self.unerase(w_dict.dstorage).dict_w.clear()
+        self.unerase(w_dict.dstorage).mutated()
 
 class DictProxyIteratorImplementation(IteratorImplementation):
-    def __init__(self, space, dictimplementation):
+    def __init__(self, space, strategy, dictimplementation):
         IteratorImplementation.__init__(self, space, dictimplementation)
-        self.iterator = dictimplementation.w_type.dict_w.iteritems()
+        w_type = strategy.unerase(dictimplementation.dstorage)
+        self.iterator = w_type.dict_w.iteritems()
 
     def next_entry(self):
         for key, w_value in self.iterator:
diff --git a/pypy/objspace/std/frame.py b/pypy/objspace/std/frame.py
--- a/pypy/objspace/std/frame.py
+++ b/pypy/objspace/std/frame.py
@@ -6,7 +6,7 @@
 from pypy.interpreter import pyopcode, function
 from pypy.interpreter.pyframe import PyFrame
 from pypy.interpreter.error import OperationError, operationerrfmt
-from pypy.module.__builtin__ import OPTIMIZED_BUILTINS, Module
+from pypy.module.__builtin__ import Module
 from pypy.objspace.std import intobject, smallintobject
 from pypy.objspace.std.multimethod import FailedToImplement
 from pypy.objspace.std.dictmultiobject import W_DictMultiObject
@@ -66,41 +66,6 @@
         w_result = f.space.getitem(w_1, w_2)
     f.pushvalue(w_result)
 
-def CALL_LIKELY_BUILTIN(f, oparg, next_instr):
-    w_globals = f.w_globals
-    num = oparg >> 8
-    assert isinstance(w_globals, W_DictMultiObject)
-    w_value = w_globals.get_builtin_indexed(num)
-    if w_value is None:
-        builtins = f.get_builtin()
-        assert isinstance(builtins, Module)
-        w_builtin_dict = builtins.getdict(f.space)
-        assert isinstance(w_builtin_dict, W_DictMultiObject)
-        w_value = w_builtin_dict.get_builtin_indexed(num)
-    if w_value is None:
-        varname = OPTIMIZED_BUILTINS[num]
-        message = "global name '%s' is not defined"
-        raise operationerrfmt(f.space.w_NameError,
-                              message, varname)
-    nargs = oparg & 0xff
-    w_function = w_value
-    try:
-        w_result = call_likely_builtin(f, w_function, nargs)
-    finally:
-        f.dropvalues(nargs)
-    f.pushvalue(w_result)
-
-def call_likely_builtin(f, w_function, nargs):
-    if isinstance(w_function, function.Function):
-        executioncontext = f.space.getexecutioncontext()
-        executioncontext.c_call_trace(f, w_function)
-        res = w_function.funccall_valuestack(nargs, f)
-        executioncontext.c_return_trace(f, w_function)
-        return res
-    args = f.make_arguments(nargs)
-    return f.space.call_args(w_function, args)
-
-
 compare_table = [
     "lt",   # "<"
     "le",   # "<="
@@ -145,8 +110,6 @@
             StdObjSpaceFrame.BINARY_ADD = int_BINARY_ADD
     if space.config.objspace.std.optimized_list_getitem:
         StdObjSpaceFrame.BINARY_SUBSCR = list_BINARY_SUBSCR
-    if space.config.objspace.opcodes.CALL_LIKELY_BUILTIN:
-        StdObjSpaceFrame.CALL_LIKELY_BUILTIN = CALL_LIKELY_BUILTIN
     if space.config.objspace.opcodes.CALL_METHOD:
         from pypy.objspace.std.callmethod import LOOKUP_METHOD, CALL_METHOD
         StdObjSpaceFrame.LOOKUP_METHOD = LOOKUP_METHOD
diff --git a/pypy/objspace/std/mapdict.py b/pypy/objspace/std/mapdict.py
--- a/pypy/objspace/std/mapdict.py
+++ b/pypy/objspace/std/mapdict.py
@@ -4,9 +4,9 @@
 from pypy.rlib import rerased
 
 from pypy.interpreter.baseobjspace import W_Root
-from pypy.objspace.std.dictmultiobject import W_DictMultiObject
+from pypy.objspace.std.dictmultiobject import W_DictMultiObject, DictStrategy, ObjectDictStrategy
 from pypy.objspace.std.dictmultiobject import IteratorImplementation
-from pypy.objspace.std.dictmultiobject import _is_sane_hash
+from pypy.objspace.std.dictmultiobject import _never_equal_to_string
 from pypy.objspace.std.objectobject import W_ObjectObject
 from pypy.objspace.std.typeobject import TypeCell
 
@@ -53,7 +53,7 @@
         else:
             return self._index_indirection(selector)
 
-    @jit.purefunction
+    @jit.elidable
     def _index_jit_pure(self, name, index):
         return self._index_indirection((name, index))
 
@@ -113,14 +113,14 @@
     def set_terminator(self, obj, terminator):
         raise NotImplementedError("abstract base class")
 
-    @jit.purefunction
+    @jit.elidable
     def size_estimate(self):
         return self._size_estimate >> NUM_DIGITS
 
     def search(self, attrtype):
         return None
 
-    @jit.purefunction
+    @jit.elidable
     def _get_new_attr(self, name, index):
         selector = name, index
         cache = self.cache_attrs
@@ -154,7 +154,7 @@
         obj._set_mapdict_map(attr)
         obj._mapdict_write_storage(attr.position, w_value)
 
-    def materialize_r_dict(self, space, obj, w_d):
+    def materialize_r_dict(self, space, obj, dict_w):
         raise NotImplementedError("abstract base class")
 
     def remove_dict_entries(self, obj):
@@ -205,7 +205,7 @@
         Terminator.__init__(self, space, w_cls)
         self.devolved_dict_terminator = DevolvedDictTerminator(space, w_cls)
 
-    def materialize_r_dict(self, space, obj, w_d):
+    def materialize_r_dict(self, space, obj, dict_w):
         result = Object()
         result.space = space
         result._init_empty(self.devolved_dict_terminator)
@@ -297,11 +297,11 @@
             return self
         return self.back.search(attrtype)
 
-    def materialize_r_dict(self, space, obj, w_d):
-        new_obj = self.back.materialize_r_dict(space, obj, w_d)
+    def materialize_r_dict(self, space, obj, dict_w):
+        new_obj = self.back.materialize_r_dict(space, obj, dict_w)
         if self.selector[1] == DICT:
             w_attr = space.wrap(self.selector[0])
-            w_d.r_dict_content[w_attr] = obj._mapdict_read_storage(self.position)
+            dict_w[w_attr] = obj._mapdict_read_storage(self.position)
         else:
             self._copy_attr(obj, new_obj)
         return new_obj
@@ -357,7 +357,7 @@
         self._set_mapdict_storage_and_map(new_obj.storage, new_obj.map)
 
     def _get_mapdict_map(self):
-        return jit.hint(self.map, promote=True)
+        return jit.promote(self.map)
     def _set_mapdict_map(self, map):
         self.map = map
     # _____________________________________________
@@ -382,7 +382,10 @@
         if w_dict is not None:
             assert isinstance(w_dict, W_DictMultiObject)
             return w_dict
-        w_dict = MapDictImplementation(space, self)
+
+        strategy = space.fromcache(MapDictStrategy)
+        storage = strategy.erase(self)
+        w_dict = W_DictMultiObject(space, strategy, storage)
         flag = self._get_mapdict_map().write(self, ("dict", SPECIAL), w_dict)
         assert flag
         return w_dict
@@ -392,8 +395,8 @@
         w_dict = check_new_dictionary(space, w_dict)
         w_olddict = self.getdict(space)
         assert isinstance(w_dict, W_DictMultiObject)
-        if w_olddict.r_dict_content is None:
-            w_olddict._as_rdict()
+        if type(w_olddict.strategy) is not ObjectDictStrategy:
+            w_olddict.strategy.switch_to_object_strategy(w_olddict)
         flag = self._get_mapdict_map().write(self, ("dict", SPECIAL), w_dict)
         assert flag
 
@@ -575,105 +578,119 @@
 # ____________________________________________________________
 # dict implementation
 
+class MapDictStrategy(DictStrategy):
 
-class MapDictImplementation(W_DictMultiObject):
-    def __init__(self, space, w_obj):
+    erase, unerase = rerased.new_erasing_pair("map")
+    erase = staticmethod(erase)
+    unerase = staticmethod(unerase)
+
+    def __init__(self, space):
         self.space = space
-        self.w_obj = w_obj
 
-    def impl_getitem(self, w_lookup):
+    def switch_to_object_strategy(self, w_dict):
+        w_obj = self.unerase(w_dict.dstorage)
+        strategy = self.space.fromcache(ObjectDictStrategy)
+        dict_w = strategy.unerase(strategy.get_empty_storage())
+        w_dict.strategy = strategy
+        w_dict.dstorage = strategy.erase(dict_w)
+        assert w_obj.getdict(self.space) is w_dict
+        materialize_r_dict(self.space, w_obj, dict_w)
+
+    def getitem(self, w_dict, w_key):
         space = self.space
-        w_lookup_type = space.type(w_lookup)
+        w_lookup_type = space.type(w_key)
         if space.is_w(w_lookup_type, space.w_str):
-            return self.impl_getitem_str(space.str_w(w_lookup))
-        elif _is_sane_hash(space, w_lookup_type):
+            return self.getitem_str(w_dict, space.str_w(w_key))
+        elif _never_equal_to_string(space, w_lookup_type):
             return None
         else:
-            return self._as_rdict().impl_fallback_getitem(w_lookup)
+            self.switch_to_object_strategy(w_dict)
+            return w_dict.getitem(w_key)
 
-    def impl_getitem_str(self, key):
-        return self.w_obj.getdictvalue(self.space, key)
+    def getitem_str(self, w_dict, key):
+        w_obj = self.unerase(w_dict.dstorage)
+        return w_obj.getdictvalue(self.space, key)
 
-    def impl_setitem_str(self,  key, w_value):
-        flag = self.w_obj.setdictvalue(self.space, key, w_value)
+    def setitem_str(self, w_dict, key, w_value):
+        w_obj = self.unerase(w_dict.dstorage)
+        flag = w_obj.setdictvalue(self.space, key, w_value)
         assert flag
 
-    def impl_setitem(self,  w_key, w_value):
+    def setitem(self, w_dict, w_key, w_value):
         space = self.space
         if space.is_w(space.type(w_key), space.w_str):
-            self.impl_setitem_str(self.space.str_w(w_key), w_value)
+            self.setitem_str(w_dict, self.space.str_w(w_key), w_value)
         else:
-            self._as_rdict().impl_fallback_setitem(w_key, w_value)
+            self.switch_to_object_strategy(w_dict)
+            w_dict.setitem(w_key, w_value)
 
-    def impl_setdefault(self,  w_key, w_default):
+    def setdefault(self, w_dict, w_key, w_default):
         space = self.space
         if space.is_w(space.type(w_key), space.w_str):
             key = space.str_w(w_key)
-            w_result = self.impl_getitem_str(key)
+            w_result = self.getitem_str(w_dict, key)
             if w_result is not None:
                 return w_result
-            self.impl_setitem_str(key, w_default)
+            self.setitem_str(w_dict, key, w_default)
             return w_default
         else:
-            return self._as_rdict().impl_fallback_setdefault(w_key, w_default)
+            self.switch_to_object_strategy(w_dict)
+            return w_dict.setdefault(w_key, w_default)
 
-    def impl_delitem(self, w_key):
+    def delitem(self, w_dict, w_key):
         space = self.space
         w_key_type = space.type(w_key)
+        w_obj = self.unerase(w_dict.dstorage)
         if space.is_w(w_key_type, space.w_str):
-            flag = self.w_obj.deldictvalue(space, w_key)
+            flag = w_obj.deldictvalue(space, w_key)
             if not flag:
                 raise KeyError
-        elif _is_sane_hash(space, w_key_type):
+        elif _never_equal_to_string(space, w_key_type):
             raise KeyError
         else:
-            self._as_rdict().impl_fallback_delitem(w_key)
+            self.switch_to_object_strategy(w_dict)
+            w_dict.delitem(w_key)
 
-    def impl_length(self):
+    def length(self, w_dict):
         res = 0
-        curr = self.w_obj._get_mapdict_map().search(DICT)
+        curr = self.unerase(w_dict.dstorage)._get_mapdict_map().search(DICT)
         while curr is not None:
             curr = curr.back
             curr = curr.search(DICT)
             res += 1
         return res
 
-    def impl_iter(self):
-        return MapDictIteratorImplementation(self.space, self)
+    def iter(self, w_dict):
+        return MapDictIteratorImplementation(self.space, self, w_dict)
 
-    def impl_clear(self):
-        w_obj = self.w_obj
+    def clear(self, w_dict):
+        w_obj = self.unerase(w_dict.dstorage)
         new_obj = w_obj._get_mapdict_map().remove_dict_entries(w_obj)
         _become(w_obj, new_obj)
 
-    def _clear_fields(self):
-        self.w_obj = None
+    def popitem(self, w_dict):
+        curr = self.unerase(w_dict.dstorage)._get_mapdict_map().search(DICT)
+        key = curr.selector[0]
+        w_value = self.getitem_str(w_dict, key)
+        w_key = self.space.wrap(key)
+        self.delitem(w_dict, w_key)
+        return (w_key, w_value)
 
-    def _as_rdict(self):
-        self.initialize_as_rdict()
-        space = self.space
-        w_obj = self.w_obj
-        materialize_r_dict(space, w_obj, self)
-        self._clear_fields()
-        return self
-
-
-def materialize_r_dict(space, obj, w_d):
+def materialize_r_dict(space, obj, dict_w):
     map = obj._get_mapdict_map()
-    assert obj.getdict(space) is w_d
-    new_obj = map.materialize_r_dict(space, obj, w_d)
+    new_obj = map.materialize_r_dict(space, obj, dict_w)
     _become(obj, new_obj)
 
 class MapDictIteratorImplementation(IteratorImplementation):
-    def __init__(self, space, dictimplementation):
+    def __init__(self, space, strategy, dictimplementation):
         IteratorImplementation.__init__(self, space, dictimplementation)
-        w_obj = dictimplementation.w_obj
+        w_obj = strategy.unerase(dictimplementation.dstorage)
         self.w_obj = w_obj
         self.orig_map = self.curr_map = w_obj._get_mapdict_map()
 
     def next_entry(self):
         implementation = self.dictimplementation
-        assert isinstance(implementation, MapDictImplementation)
+        assert isinstance(implementation.strategy, MapDictStrategy)
         if self.orig_map is not self.w_obj._get_mapdict_map():
             return None, None
         if self.curr_map:
diff --git a/pypy/objspace/std/objspace.py b/pypy/objspace/std/objspace.py
--- a/pypy/objspace/std/objspace.py
+++ b/pypy/objspace/std/objspace.py
@@ -11,7 +11,7 @@
 from pypy.rlib.debug import make_sure_not_resized
 from pypy.rlib.rarithmetic import base_int, widen
 from pypy.rlib.objectmodel import we_are_translated
-from pypy.rlib.jit import hint
+from pypy.rlib import jit
 from pypy.rlib.rbigint import rbigint
 from pypy.tool.sourcetools import func_with_new_name
 
@@ -322,7 +322,7 @@
         return W_SeqIterObject(w_obj)
 
     def type(self, w_obj):
-        hint(w_obj.__class__, promote=True)
+        jit.promote(w_obj.__class__)
         return w_obj.getclass(self)
 
     def lookup(self, w_obj, name):
diff --git a/pypy/objspace/std/setobject.py b/pypy/objspace/std/setobject.py
--- a/pypy/objspace/std/setobject.py
+++ b/pypy/objspace/std/setobject.py
@@ -112,7 +112,7 @@
 # some helper functions
 
 def newset(space):
-    return r_dict(space.eq_w, space.hash_w)
+    return r_dict(space.eq_w, space.hash_w, force_non_null=True)
 
 def make_setdata_from_w_iterable(space, w_iterable=None):
     """Return a new r_dict with the content of w_iterable."""
@@ -466,12 +466,11 @@
     return space.wrap(hash)
 
 def set_pop__Set(space, w_left):
-    for w_key in w_left.setdata:
-        break
-    else:
+    try:
+        w_key, _ = w_left.setdata.popitem()
+    except KeyError:
         raise OperationError(space.w_KeyError,
                                 space.wrap('pop from an empty set'))
-    del w_left.setdata[w_key]
     return w_key
 
 def and__Set_Set(space, w_left, w_other):
diff --git a/pypy/objspace/std/test/test_celldict.py b/pypy/objspace/std/test/test_celldict.py
--- a/pypy/objspace/std/test/test_celldict.py
+++ b/pypy/objspace/std/test/test_celldict.py
@@ -1,6 +1,7 @@
 import py
 from pypy.conftest import gettestobjspace, option
-from pypy.objspace.std.celldict import ModuleCell, ModuleDictImplementation
+from pypy.objspace.std.dictmultiobject import W_DictMultiObject
+from pypy.objspace.std.celldict import ModuleCell, ModuleDictStrategy
 from pypy.objspace.std.test.test_dictmultiobject import FakeSpace
 from pypy.interpreter import gateway
 
@@ -8,7 +9,15 @@
 
 class TestCellDict(object):
     def test_basic_property(self):
-        d = ModuleDictImplementation(space)
+        strategy = ModuleDictStrategy(space)
+        storage = strategy.get_empty_storage()
+        d = W_DictMultiObject(space, strategy, storage)
+
+        # replace getcell with getcell from strategy
+        def f(key, makenew):
+            return strategy.getcell(d, key, makenew)
+        d.getcell = f
+
         d.setitem("a", 1)
         assert d.getcell("a", False) is d.getcell("a", False)
         acell = d.getcell("a", False)
@@ -29,3 +38,31 @@
         assert d.getitem("a") is None
         assert d.getcell("a", False) is acell
         assert d.length() == 0
+
+class AppTestCellDict(object):
+    OPTIONS = {"objspace.std.withcelldict": True}
+
+    def setup_class(cls):
+        strategy = ModuleDictStrategy(cls.space)
+        storage = strategy.get_empty_storage()
+        cls.w_d = W_DictMultiObject(cls.space, strategy, storage)
+
+    def test_popitem(self):
+        import __pypy__
+
+        d = self.d
+        assert "ModuleDict" in __pypy__.internal_repr(d)
+        raises(KeyError, d.popitem)
+        d["a"] = 3
+        x = d.popitem()
+        assert x == ("a", 3)
+
+    def test_degenerate(self):
+        import __pypy__
+
+        d = self.d
+        assert "ModuleDict" in __pypy__.internal_repr(d)
+        d["a"] = 3
+        del d["a"]
+        d[object()] = 5
+        assert d.values() == [5]
\ No newline at end of file
diff --git a/pypy/objspace/std/test/test_dictmultiobject.py b/pypy/objspace/std/test/test_dictmultiobject.py
--- a/pypy/objspace/std/test/test_dictmultiobject.py
+++ b/pypy/objspace/std/test/test_dictmultiobject.py
@@ -1,12 +1,13 @@
+import py
 import sys
 from pypy.interpreter.error import OperationError
 from pypy.objspace.std.dictmultiobject import \
      W_DictMultiObject, setitem__DictMulti_ANY_ANY, getitem__DictMulti_ANY, \
-     StrDictImplementation
+     StringDictStrategy, ObjectDictStrategy
 
-from pypy.objspace.std.celldict import ModuleDictImplementation
+from pypy.objspace.std.celldict import ModuleDictStrategy
 from pypy.conftest import gettestobjspace
-
+from pypy.conftest import option
 
 class TestW_DictObject:
 
@@ -17,7 +18,7 @@
         space = self.space
         d = self.space.newdict()
         assert not self.space.is_true(d)
-        assert d.r_dict_content is None
+        assert type(d.strategy) is not ObjectDictStrategy
 
     def test_nonempty(self):
         space = self.space
@@ -233,6 +234,31 @@
         assert it1 == ('x', 5)
         raises(KeyError, d.popitem)
 
+    def test_popitem3(self):
+        #object
+        d = {"a": 1, 2:2, "c":3}
+        l = []
+        while True:
+            try:
+                l.append(d.popitem())
+            except KeyError:
+                break;
+        assert ("a",1) in l
+        assert (2,2) in l
+        assert ("c",3) in l
+
+        #string
+        d = {"a": 1, "b":2, "c":3}
+        l = []
+        while True:
+            try:
+                l.append(d.popitem())
+            except KeyError:
+                break;
+        assert ("a",1) in l
+        assert ("b",2) in l
+        assert ("c",3) in l
+
     def test_setdefault(self):
         d = {1:2, 3:4}
         dd = d.copy()
@@ -527,6 +553,12 @@
             __missing__ = SpecialDescr(missing)
         assert X()['hi'] == 42
 
+    def test_empty_dict(self):
+        d = {}
+        raises(KeyError, d.popitem)
+        assert d.items() == []
+        assert d.values() == []
+        assert d.keys() == []
 
 class AppTest_DictMultiObject(AppTest_DictObject):
 
@@ -706,10 +738,12 @@
 class AppTestModuleDict(object):
     def setup_class(cls):
         cls.space = gettestobjspace(**{"objspace.std.withcelldict": True})
+        if option.runappdirect:
+            py.test.skip("__repr__ doesn't work on appdirect")
 
     def w_impl_used(self, obj):
         import __pypy__
-        assert "ModuleDictImplementation" in __pypy__.internal_repr(obj)
+        assert "ModuleDictStrategy" in __pypy__.internal_repr(obj)
 
     def test_check_module_uses_module_dict(self):
         m = type(__builtins__)("abc")
@@ -719,6 +753,64 @@
         d = type(__builtins__)("abc").__dict__
         raises(KeyError, "d['def']")
 
+    def test_fallback_evil_key(self):
+        class F(object):
+            def __hash__(self):
+                return hash("s")
+            def __eq__(self, other):
+                return other == "s"
+        d = type(__builtins__)("abc").__dict__
+        d["s"] = 12
+        assert d["s"] == 12
+        assert d[F()] == d["s"]
+
+        d = type(__builtins__)("abc").__dict__
+        x = d.setdefault("s", 12)
+        assert x == 12
+        x = d.setdefault(F(), 12)
+        assert x == 12
+
+        d = type(__builtins__)("abc").__dict__
+        x = d.setdefault(F(), 12)
+        assert x == 12
+
+        d = type(__builtins__)("abc").__dict__
+        d["s"] = 12
+        del d[F()]
+
+        assert "s" not in d
+        assert F() not in d
+
+class AppTestStrategies(object):
+    def setup_class(cls):
+        if option.runappdirect:
+            py.test.skip("__repr__ doesn't work on appdirect")
+
+    def w_get_strategy(self, obj):
+        import __pypy__
+        r = __pypy__.internal_repr(obj)
+        return r[r.find("(") + 1: r.find(")")]
+
+    def test_empty_to_string(self):
+        d = {}
+        assert "EmptyDictStrategy" in self.get_strategy(d)
+        d["a"] = 1
+        assert "StringDictStrategy" in self.get_strategy(d)
+
+        class O(object):
+            pass
+        o = O()
+        d = o.__dict__ = {}
+        assert "EmptyDictStrategy" in self.get_strategy(d)
+        o.a = 1
+        assert "StringDictStrategy" in self.get_strategy(d)
+
+    def test_empty_to_int(self):
+        import sys
+        d = {}
+        d[1] = "hi"
+        assert "IntDictStrategy" in self.get_strategy(d)
+        assert d[1L] == "hi"
 
 
 class FakeString(str):
@@ -759,6 +851,10 @@
         assert isinstance(string, str)
         return string
 
+    def int_w(self, integer):
+        assert isinstance(integer, int)
+        return integer
+
     def wrap(self, obj):
         return obj
 
@@ -790,6 +886,10 @@
 
     w_StopIteration = StopIteration
     w_None = None
+    w_NoneType = type(None, None)
+    w_int = int
+    w_bool = bool
+    w_float = float
     StringObjectCls = FakeString
     w_dict = W_DictMultiObject
     iter = iter
@@ -799,12 +899,9 @@
 class Config:
     class objspace:
         class std:
-            withdictmeasurement = False
             withsmalldicts = False
             withcelldict = False
             withmethodcache = False
-        class opcodes:
-            CALL_LIKELY_BUILTIN = False
 
 FakeSpace.config = Config()
 
@@ -834,14 +931,20 @@
         self.impl = self.get_impl()
 
     def get_impl(self):
-        return self.ImplementionClass(self.fakespace)
+        strategy = self.StrategyClass(self.fakespace)
+        storage = strategy.get_empty_storage()
+        w_dict = self.fakespace.allocate_instance(W_DictMultiObject, None)
+        W_DictMultiObject.__init__(w_dict, self.fakespace, strategy, storage)
+        return w_dict
 
     def fill_impl(self):
         self.impl.setitem(self.string, 1000)
         self.impl.setitem(self.string2, 2000)
 
     def check_not_devolved(self):
-        assert self.impl.r_dict_content is None
+        #XXX check if strategy changed!?
+        assert type(self.impl.strategy) is self.StrategyClass
+        #assert self.impl.r_dict_content is None
 
     def test_setitem(self):
         self.impl.setitem(self.string, 1000)
@@ -913,7 +1016,7 @@
         for x in xrange(100):
             impl.setitem(self.fakespace.str_w(str(x)), x)
             impl.setitem(x, x)
-        assert impl.r_dict_content is not None
+        assert type(impl.strategy) is ObjectDictStrategy
 
     def test_setdefault_fast(self):
         on_pypy = "__pypy__" in sys.builtin_module_names
@@ -928,8 +1031,38 @@
         if on_pypy:
             assert key.hash_count == 2
 
+    def test_fallback_evil_key(self):
+        class F(object):
+            def __hash__(self):
+                return hash("s")
+            def __eq__(self, other):
+                return other == "s"
+
+        d = self.get_impl()
+        d.setitem("s", 12)
+        assert d.getitem("s") == 12
+        assert d.getitem(F()) == d.getitem("s")
+
+        d = self.get_impl()
+        x = d.setdefault("s", 12)
+        assert x == 12
+        x = d.setdefault(F(), 12)
+        assert x == 12
+
+        d = self.get_impl()
+        x = d.setdefault(F(), 12)
+        assert x == 12
+
+        d = self.get_impl()
+        d.setitem("s", 12)
+        d.delitem(F())
+
+        assert "s" not in d.keys()
+        assert F() not in d.keys()
+
 class TestStrDictImplementation(BaseTestRDictImplementation):
-    ImplementionClass = StrDictImplementation
+    StrategyClass = StringDictStrategy
+    #ImplementionClass = StrDictImplementation
 
     def test_str_shortcut(self):
         self.fill_impl()
@@ -942,10 +1075,10 @@
 ##     DevolvedClass = MeasuringDictImplementation
 
 class TestModuleDictImplementation(BaseTestRDictImplementation):
-    ImplementionClass = ModuleDictImplementation
+    StrategyClass = ModuleDictStrategy
 
 class TestModuleDictImplementationWithBuiltinNames(BaseTestRDictImplementation):
-    ImplementionClass = ModuleDictImplementation
+    StrategyClass = ModuleDictStrategy
 
     string = "int"
     string2 = "isinstance"
@@ -954,19 +1087,19 @@
 class BaseTestDevolvedDictImplementation(BaseTestRDictImplementation):
     def fill_impl(self):
         BaseTestRDictImplementation.fill_impl(self)
-        self.impl._as_rdict()
+        self.impl.strategy.switch_to_object_strategy(self.impl)
 
     def check_not_devolved(self):
         pass
 
 class TestDevolvedStrDictImplementation(BaseTestDevolvedDictImplementation):
-    ImplementionClass = StrDictImplementation
+    StrategyClass = StringDictStrategy
 
 class TestDevolvedModuleDictImplementation(BaseTestDevolvedDictImplementation):
-    ImplementionClass = ModuleDictImplementation
+    StrategyClass = ModuleDictStrategy
 
 class TestDevolvedModuleDictImplementationWithBuiltinNames(BaseTestDevolvedDictImplementation):
-    ImplementionClass = ModuleDictImplementation
+    StrategyClass = ModuleDictStrategy
 
     string = "int"
     string2 = "isinstance"
@@ -975,5 +1108,4 @@
 def test_module_uses_strdict():
     fakespace = FakeSpace()
     d = fakespace.newdict(module=True)
-    assert isinstance(d, StrDictImplementation)
-
+    assert type(d.strategy) is StringDictStrategy
diff --git a/pypy/objspace/std/test/test_mapdict.py b/pypy/objspace/std/test/test_mapdict.py
--- a/pypy/objspace/std/test/test_mapdict.py
+++ b/pypy/objspace/std/test/test_mapdict.py
@@ -250,13 +250,18 @@
 
     class FakeDict(W_DictMultiObject):
         def __init__(self, d):
-            self.r_dict_content = d
+            self.dstorage = d
+
+        class strategy:
+            def unerase(self, x):
+                return d
+        strategy = strategy()
 
     d = {}
     w_d = FakeDict(d)
     flag = obj.map.write(obj, ("dict", SPECIAL), w_d)
     assert flag
-    materialize_r_dict(space, obj, w_d)
+    materialize_r_dict(space, obj, d)
     assert d == {"a": 5, "b": 6, "c": 7}
     assert obj.storage == [50, 60, 70, w_d]
 
@@ -291,18 +296,18 @@
     w_obj = cls.instantiate(self.fakespace)
     return w_obj.getdict(self.fakespace)
 class TestMapDictImplementation(BaseTestRDictImplementation):
-    ImplementionClass = MapDictImplementation
+    StrategyClass = MapDictStrategy
     get_impl = get_impl
 class TestDevolvedMapDictImplementation(BaseTestDevolvedDictImplementation):
     get_impl = get_impl
-    ImplementionClass = MapDictImplementation
+    StrategyClass = MapDictStrategy
 
 # ___________________________________________________________
 # tests that check the obj interface after the dict has devolved
 
 def devolve_dict(space, obj):
     w_d = obj.getdict(space)
-    w_d._as_rdict()
+    w_d.strategy.switch_to_object_strategy(w_d)
 
 def test_get_setdictvalue_after_devolve():
     cls = Class()
@@ -463,6 +468,19 @@
         d['dd'] = 43
         assert a.dd == 41
 
+    def test_popitem(self):
+        class A(object):
+            pass
+        a = A()
+        a.x = 5
+        a.y = 6
+        it1 = a.__dict__.popitem()
+        assert it1 == ("y", 6)
+        it2 = a.__dict__.popitem()
+        assert it2 == ("x", 5)
+        assert a.__dict__ == {}
+
+
 
     def test_slot_name_conflict(self):
         class A(object):
diff --git a/pypy/objspace/std/typeobject.py b/pypy/objspace/std/typeobject.py
--- a/pypy/objspace/std/typeobject.py
+++ b/pypy/objspace/std/typeobject.py
@@ -9,8 +9,8 @@
 from pypy.objspace.std.objecttype import object_typedef
 from pypy.rlib.objectmodel import we_are_translated
 from pypy.rlib.objectmodel import current_object_addr_as_int, compute_hash
-from pypy.rlib.jit import hint, purefunction_promote, we_are_jitted
-from pypy.rlib.jit import purefunction, dont_look_inside, unroll_safe
+from pypy.rlib.jit import promote, elidable_promote, we_are_jitted
+from pypy.rlib.jit import elidable, dont_look_inside, unroll_safe
 from pypy.rlib.rarithmetic import intmask, r_uint
 
 class TypeCell(W_Root):
@@ -177,7 +177,7 @@
         # prebuilt objects cannot get their version_tag changed
         return w_self._pure_version_tag()
 
-    @purefunction_promote()
+    @elidable_promote()
     def _pure_version_tag(w_self):
         return w_self._version_tag
 
@@ -247,7 +247,7 @@
                     return w_value
         return w_value
 
-    @purefunction
+    @elidable
     def _pure_getdictvalue_no_unwrapping(w_self, space, version_tag, attr):
         return w_self._getdictvalue_no_unwrapping(space, attr)
 
@@ -351,16 +351,16 @@
 
     def lookup_where_with_method_cache(w_self, name):
         space = w_self.space
-        w_self = hint(w_self, promote=True)
+        promote(w_self)
         assert space.config.objspace.std.withmethodcache
-        version_tag = hint(w_self.version_tag(), promote=True)
+        version_tag = promote(w_self.version_tag())
         if version_tag is None:
             tup = w_self._lookup_where(name)
             return tup
         w_class, w_value = w_self._pure_lookup_where_with_method_cache(name, version_tag)
         return w_class, unwrap_cell(space, w_value)
 
-    @purefunction
+    @elidable
     def _pure_lookup_where_with_method_cache(w_self, name, version_tag):
         space = w_self.space
         cache = space.fromcache(MethodCache)
@@ -423,10 +423,13 @@
         return False
 
     def getdict(w_self, space): # returning a dict-proxy!
-        from pypy.objspace.std.dictproxyobject import W_DictProxyObject
+        from pypy.objspace.std.dictproxyobject import DictProxyStrategy
+        from pypy.objspace.std.dictmultiobject import W_DictMultiObject
         if w_self.lazyloaders:
             w_self._freeze_()    # force un-lazification
-        return W_DictProxyObject(space, w_self)
+        strategy = space.fromcache(DictProxyStrategy)
+        storage = strategy.erase(w_self)
+        return W_DictMultiObject(space, strategy, storage)
 
     def unwrap(w_self, space):
         if w_self.instancetypedef.fakedcpytype is not None:
@@ -447,8 +450,8 @@
         w_self.flag_abstract = bool(abstract)
 
     def issubtype(w_self, w_type):
-        w_self = hint(w_self, promote=True)
-        w_type = hint(w_type, promote=True)
+        promote(w_self)
+        promote(w_type)
         if w_self.space.config.objspace.std.withtypeversion and we_are_jitted():
             version_tag1 = w_self.version_tag()
             version_tag2 = w_type.version_tag()
@@ -774,7 +777,7 @@
 # ____________________________________________________________
 
 def call__Type(space, w_type, __args__):
-    w_type = hint(w_type, promote=True)
+    promote(w_type)
     # special case for type(x)
     if space.is_w(w_type, space.w_type):
         try:
@@ -820,7 +823,7 @@
 def _issubtype(w_sub, w_type):
     return w_type in w_sub.mro_w
 
- at purefunction_promote()
+ at elidable_promote()
 def _pure_issubtype(w_sub, w_type, version_tag1, version_tag2):
     return _issubtype(w_sub, w_type)
 
diff --git a/pypy/rlib/debug.py b/pypy/rlib/debug.py
--- a/pypy/rlib/debug.py
+++ b/pypy/rlib/debug.py
@@ -262,6 +262,28 @@
         return hop.inputarg(hop.args_r[0], arg=0)
 
 
+def mark_dict_non_null(d):
+    """ Mark dictionary as having non-null keys and values. A warning would
+    be emitted (not an error!) in case annotation disagrees.
+    """
+    assert isinstance(d, dict)
+    return d
+
+
+class DictMarkEntry(ExtRegistryEntry):
+    _about_ = mark_dict_non_null
+    
+    def compute_result_annotation(self, s_dict):
+        from pypy.annotation.model import SomeDict, s_None
+
+        assert isinstance(s_dict, SomeDict)
+        s_dict.dictdef.force_non_null = True
+        return s_dict
+
+    def specialize_call(self, hop):
+        hop.exception_cannot_occur()
+        return hop.inputarg(hop.args_r[0], arg=0)
+
 class IntegerCanBeNegative(Exception):
     pass
 
diff --git a/pypy/rlib/jit.py b/pypy/rlib/jit.py
--- a/pypy/rlib/jit.py
+++ b/pypy/rlib/jit.py
@@ -6,21 +6,26 @@
 from pypy.rlib.unroll import unrolling_iterable
 from pypy.rlib.nonconst import NonConstant
 
-def purefunction(func):
-    """ Decorate a function as pure. Pure means precisely that:
+def elidable(func):
+    """ Decorate a function as "trace-elidable". This means precisely that:
 
     (1) the result of the call should not change if the arguments are
         the same (same numbers or same pointers)
     (2) it's fine to remove the call completely if we can guess the result
     according to rule 1
 
-    Most importantly it doesn't mean that pure function has no observable
-    side effect, but those side effects can be ommited (ie caching).
+    Most importantly it doesn't mean that an elidable function has no observable
+    side effect, but those side effects are idempotent (ie caching).
     For now, such a function should never raise an exception.
     """
-    func._pure_function_ = True
+    func._elidable_function_ = True
     return func
 
+def purefunction(*args, **kwargs):
+    import warnings
+    warnings.warn("purefunction is deprecated, use elidable instead", DeprecationWarning)
+    return elidable(*args, **kwargs)
+
 def hint(x, **kwds):
     """ Hint for the JIT
 
@@ -36,6 +41,10 @@
     """
     return x
 
+ at specialize.argtype(0)
+def promote(x):
+    return hint(x, promote=True)
+
 def dont_look_inside(func):
     """ Make sure the JIT does not trace inside decorated function
     (it becomes a call instead)
@@ -60,13 +69,13 @@
     func._jit_loop_invariant_ = True
     return func
 
-def purefunction_promote(promote_args='all'):
+def elidable_promote(promote_args='all'):
     """ A decorator that promotes all arguments and then calls the supplied
     function
     """
     def decorator(func):
         import inspect
-        purefunction(func)
+        elidable(func)
         args, varargs, varkw, defaults = inspect.getargspec(func)
         args = ["v%s" % (i, ) for i in range(len(args))]
         assert varargs is None and varkw is None
@@ -85,6 +94,12 @@
         return result
     return decorator
 
+def purefunction_promote(*args, **kwargs):
+    import warnings
+    warnings.warn("purefunction_promote is deprecated, use elidable_promote instead", DeprecationWarning)
+    return elidable_promote(*args, **kwargs)
+
+
 def oopspec(spec):
     def decorator(func):
         func.oopspec = spec
diff --git a/pypy/rlib/libffi.py b/pypy/rlib/libffi.py
--- a/pypy/rlib/libffi.py
+++ b/pypy/rlib/libffi.py
@@ -40,7 +40,7 @@
         del cls._import
 
     @staticmethod
-    @jit.purefunction
+    @jit.elidable
     def getkind(ffi_type):
         """Returns 'v' for void, 'f' for float, 'i' for signed integer,
         and 'u' for unsigned integer.
@@ -74,7 +74,7 @@
         raise KeyError
 
     @staticmethod
-    @jit.purefunction
+    @jit.elidable
     def is_struct(ffi_type):
         return intmask(ffi_type.c_type) == intmask(FFI_TYPE_STRUCT)
 
@@ -253,7 +253,7 @@
         # the optimizer will fail to recognize the pattern and won't turn it
         # into a fast CALL.  Note that "arg = arg.next" is optimized away,
         # assuming that archain is completely virtual.
-        self = jit.hint(self, promote=True)
+        self = jit.promote(self)
         if argchain.numargs != len(self.argtypes):
             raise TypeError, 'Wrong number of arguments: %d expected, got %d' %\
                 (argchain.numargs, len(self.argtypes))
diff --git a/pypy/rlib/longlong2float.py b/pypy/rlib/longlong2float.py
--- a/pypy/rlib/longlong2float.py
+++ b/pypy/rlib/longlong2float.py
@@ -49,9 +49,9 @@
 longlong2float = rffi.llexternal(
     "pypy__longlong2float", [rffi.LONGLONG], rffi.DOUBLE,
     _callable=longlong2float_emulator, compilation_info=eci,
-    _nowrapper=True, pure_function=True)
+    _nowrapper=True, elidable_function=True)
 
 float2longlong = rffi.llexternal(
     "pypy__float2longlong", [rffi.DOUBLE], rffi.LONGLONG,
     _callable=float2longlong_emulator, compilation_info=eci,
-    _nowrapper=True, pure_function=True)
+    _nowrapper=True, elidable_function=True)
diff --git a/pypy/rlib/objectmodel.py b/pypy/rlib/objectmodel.py
--- a/pypy/rlib/objectmodel.py
+++ b/pypy/rlib/objectmodel.py
@@ -448,10 +448,11 @@
     The functions key_eq() and key_hash() are used by the key comparison
     algorithm."""
 
-    def __init__(self, key_eq, key_hash):
+    def __init__(self, key_eq, key_hash, force_non_null=False):
         self._dict = {}
         self.key_eq = key_eq
         self.key_hash = key_hash
+        self.force_non_null = force_non_null
 
     def __getitem__(self, key):
         return self._dict[_r_dictkey(self, key)]
diff --git a/pypy/rlib/rbigint.py b/pypy/rlib/rbigint.py
--- a/pypy/rlib/rbigint.py
+++ b/pypy/rlib/rbigint.py
@@ -124,7 +124,7 @@
         return len(self._digits)
 
     @staticmethod
-    @jit.purefunction
+    @jit.elidable
     def fromint(intval):
         # This function is marked as pure, so you must not call it and
         # then modify the result.
@@ -156,7 +156,7 @@
         return v
 
     @staticmethod
-    @jit.purefunction
+    @jit.elidable
     def frombool(b):
         # This function is marked as pure, so you must not call it and
         # then modify the result.
@@ -179,7 +179,7 @@
             raise OverflowError
 
     @staticmethod
-    @jit.purefunction
+    @jit.elidable
     def _fromfloat_finite(dval):
         sign = 1
         if dval < 0.0:
@@ -201,7 +201,7 @@
         return v
 
     @staticmethod
-    @jit.purefunction
+    @jit.elidable
     @specialize.argtype(0)
     def fromrarith_int(i):
         # This function is marked as pure, so you must not call it and
@@ -209,7 +209,7 @@
         return rbigint(*args_from_rarith_int(i))
 
     @staticmethod
-    @jit.purefunction
+    @jit.elidable
     def fromdecimalstr(s):
         # This function is marked as pure, so you must not call it and
         # then modify the result.
diff --git a/pypy/rlib/rgc.py b/pypy/rlib/rgc.py
--- a/pypy/rlib/rgc.py
+++ b/pypy/rlib/rgc.py
@@ -272,7 +272,9 @@
     if isinstance(TP.OF, lltype.Ptr) and TP.OF.TO._gckind == 'gc':
         # perform a write barrier that copies necessary flags from
         # source to dest
-        if not llop.gc_writebarrier_before_copy(lltype.Bool, source, dest):
+        if not llop.gc_writebarrier_before_copy(lltype.Bool, source, dest,
+                                                source_start, dest_start,
+                                                length):
             # if the write barrier is not supported, copy by hand
             for i in range(length):
                 dest[i + dest_start] = source[i + source_start]
diff --git a/pypy/rlib/rmd5.py b/pypy/rlib/rmd5.py
--- a/pypy/rlib/rmd5.py
+++ b/pypy/rlib/rmd5.py
@@ -51,7 +51,7 @@
     _rotateLeft = rffi.llexternal(
         "pypy__rotateLeft", [lltype.Unsigned, lltype.Signed], lltype.Unsigned,
         _callable=_rotateLeft_emulator, compilation_info=eci,
-        _nowrapper=True, pure_function=True)
+        _nowrapper=True, elidable_function=True)
     # we expect the function _rotateLeft to be actually inlined
 
 
diff --git a/pypy/rlib/test/test_debug.py b/pypy/rlib/test/test_debug.py
--- a/pypy/rlib/test/test_debug.py
+++ b/pypy/rlib/test/test_debug.py
@@ -1,11 +1,12 @@
 
 import py
-from pypy.rlib.debug import check_annotation, make_sure_not_resized
-from pypy.rlib.debug import debug_print, debug_start, debug_stop
-from pypy.rlib.debug import have_debug_prints, debug_offset, debug_flush
-from pypy.rlib.debug import check_nonneg, IntegerCanBeNegative
+from pypy.rlib.debug import (check_annotation, make_sure_not_resized,
+                             debug_print, debug_start, debug_stop,
+                             have_debug_prints, debug_offset, debug_flush,
+                             check_nonneg, IntegerCanBeNegative,
+                             mark_dict_non_null)
 from pypy.rlib import debug
-from pypy.rpython.test.test_llinterp import interpret
+from pypy.rpython.test.test_llinterp import interpret, gengraph
 
 def test_check_annotation():
     class Error(Exception):
@@ -52,8 +53,17 @@
     py.test.raises(ListChangeUnallowed, interpret, f, [], 
                    list_comprehension_operations=True)
 
+def test_mark_dict_non_null():
+    def f():
+        d = {"ac": "bx"}
+        mark_dict_non_null(d)
+        return d
 
-class DebugTests:
+    t, typer, graph = gengraph(f, [])
+    assert sorted(graph.returnblock.inputargs[0].concretetype.TO.entries.TO.OF._flds.keys()) == ['key', 'value']
+
+
+class DebugTests(object):
 
     def test_debug_print_start_stop(self):
         def f(x):
diff --git a/pypy/rlib/test/test_jit.py b/pypy/rlib/test/test_jit.py
--- a/pypy/rlib/test/test_jit.py
+++ b/pypy/rlib/test/test_jit.py
@@ -1,6 +1,6 @@
 import py
 from pypy.conftest import option
-from pypy.rlib.jit import hint, we_are_jitted, JitDriver, purefunction_promote
+from pypy.rlib.jit import hint, we_are_jitted, JitDriver, elidable_promote
 from pypy.rlib.jit import JitHintError, oopspec
 from pypy.translator.translator import TranslationContext, graphof
 from pypy.rpython.test.tool import BaseRtypingTest, LLRtypeMixin, OORtypeMixin
@@ -31,8 +31,8 @@
         res = self.interpret(f, [4])
         assert res == 5
 
-    def test_purefunction_promote(self):
-        @purefunction_promote()
+    def test_elidable_promote(self):
+        @elidable_promote()
         def g(func):
             return func + 1
         def f(x):
@@ -40,8 +40,8 @@
         res = self.interpret(f, [2])
         assert res == 5
 
-    def test_purefunction_promote_args(self):
-        @purefunction_promote(promote_args='0')
+    def test_elidable_promote_args(self):
+        @elidable_promote(promote_args='0')
         def g(func, x):
             return func + 1
         def f(x):
diff --git a/pypy/rpython/llinterp.py b/pypy/rpython/llinterp.py
--- a/pypy/rpython/llinterp.py
+++ b/pypy/rpython/llinterp.py
@@ -737,9 +737,12 @@
     def op_zero_gc_pointers_inside(self, obj):
         raise NotImplementedError("zero_gc_pointers_inside")
 
-    def op_gc_writebarrier_before_copy(self, source, dest):
+    def op_gc_writebarrier_before_copy(self, source, dest,
+                                       source_start, dest_start, length):
         if hasattr(self.heap, 'writebarrier_before_copy'):
-            return self.heap.writebarrier_before_copy(source, dest)
+            return self.heap.writebarrier_before_copy(source, dest,
+                                                      source_start, dest_start,
+                                                      length)
         else:
             return True
 
diff --git a/pypy/rpython/lltypesystem/ll_str.py b/pypy/rpython/lltypesystem/ll_str.py
--- a/pypy/rpython/lltypesystem/ll_str.py
+++ b/pypy/rpython/lltypesystem/ll_str.py
@@ -1,12 +1,13 @@
 from pypy.rpython.lltypesystem.lltype import GcArray, Array, Char, malloc
 from pypy.rpython.annlowlevel import llstr
 from pypy.rlib.rarithmetic import r_uint, r_longlong, r_ulonglong
+from pypy.rlib import jit
 
 CHAR_ARRAY = GcArray(Char)
 
+ at jit.elidable
 def ll_int_str(repr, i):
     return ll_int2dec(i)
-ll_int_str._pure_function_ = True
 
 def ll_unsigned(i):
     if isinstance(i, r_longlong) or isinstance(i, r_ulonglong):
@@ -14,6 +15,7 @@
     else:
         return r_uint(i)
 
+ at jit.elidable
 def ll_int2dec(i):
     from pypy.rpython.lltypesystem.rstr import mallocstr
     temp = malloc(CHAR_ARRAY, 20)
@@ -44,13 +46,13 @@
         result.chars[j] = temp[len-j-1]
         j += 1
     return result
-ll_int2dec._pure_function_ = True
 
 hex_chars = malloc(Array(Char), 16, immortal=True)
 
 for i in range(16):
     hex_chars[i] = "%x"%i
 
+ at jit.elidable
 def ll_int2hex(i, addPrefix):
     from pypy.rpython.lltypesystem.rstr import mallocstr
     temp = malloc(CHAR_ARRAY, 20)
@@ -86,8 +88,8 @@
         result.chars[j] = temp[len-j-1]
         j += 1
     return result
-ll_int2hex._pure_function_ = True
 
+ at jit.elidable
 def ll_int2oct(i, addPrefix):
     from pypy.rpython.lltypesystem.rstr import mallocstr
     if i == 0:
@@ -123,9 +125,8 @@
         result.chars[j] = temp[len-j-1]
         j += 1
     return result
-ll_int2oct._pure_function_ = True
 
+ at jit.elidable
 def ll_float_str(repr, f):
     from pypy.rlib.rfloat import formatd
     return llstr(formatd(f, 'f', 6))
-ll_float_str._pure_function_ = True
diff --git a/pypy/rpython/lltypesystem/module/ll_math.py b/pypy/rpython/lltypesystem/module/ll_math.py
--- a/pypy/rpython/lltypesystem/module/ll_math.py
+++ b/pypy/rpython/lltypesystem/module/ll_math.py
@@ -58,7 +58,7 @@
 math_log10 = llexternal('log10', [rffi.DOUBLE], rffi.DOUBLE)
 math_copysign = llexternal(underscore + 'copysign',
                            [rffi.DOUBLE, rffi.DOUBLE], rffi.DOUBLE,
-                           pure_function=True)
+                           elidable_function=True)
 math_atan2 = llexternal('atan2', [rffi.DOUBLE, rffi.DOUBLE], rffi.DOUBLE)
 math_frexp = llexternal('frexp', [rffi.DOUBLE, rffi.INTP], rffi.DOUBLE)
 math_modf  = llexternal('modf',  [rffi.DOUBLE, rffi.DOUBLEP], rffi.DOUBLE)
@@ -67,11 +67,11 @@
 math_fmod  = llexternal('fmod',  [rffi.DOUBLE, rffi.DOUBLE], rffi.DOUBLE)
 math_hypot = llexternal(underscore + 'hypot',
                         [rffi.DOUBLE, rffi.DOUBLE], rffi.DOUBLE)
-math_floor = llexternal('floor', [rffi.DOUBLE], rffi.DOUBLE, pure_function=True)
+math_floor = llexternal('floor', [rffi.DOUBLE], rffi.DOUBLE, elidable_function=True)
 
 math_sqrt = llexternal('sqrt', [rffi.DOUBLE], rffi.DOUBLE)
 
- at jit.purefunction
+ at jit.elidable
 def sqrt_nonneg(x):
     return math_sqrt(x)
 sqrt_nonneg.oopspec = "math.sqrt_nonneg(x)"
diff --git a/pypy/rpython/lltypesystem/opimpl.py b/pypy/rpython/lltypesystem/opimpl.py
--- a/pypy/rpython/lltypesystem/opimpl.py
+++ b/pypy/rpython/lltypesystem/opimpl.py
@@ -473,12 +473,16 @@
     checkadr(addr2)
     return addr1 - addr2
 
-def op_gc_writebarrier_before_copy(source, dest):
+def op_gc_writebarrier_before_copy(source, dest,
+                                   source_start, dest_start, length):
     A = lltype.typeOf(source)
     assert A == lltype.typeOf(dest)
     assert isinstance(A.TO, lltype.GcArray)
     assert isinstance(A.TO.OF, lltype.Ptr)
     assert A.TO.OF.TO._gckind == 'gc'
+    assert type(source_start) is int
+    assert type(dest_start) is int
+    assert type(length) is int
     return True
 
 def op_getfield(p, name):
diff --git a/pypy/rpython/lltypesystem/rdict.py b/pypy/rpython/lltypesystem/rdict.py
--- a/pypy/rpython/lltypesystem/rdict.py
+++ b/pypy/rpython/lltypesystem/rdict.py
@@ -9,6 +9,7 @@
 from pypy.rpython import robject
 from pypy.rlib import objectmodel, jit
 from pypy.rpython import rmodel
+from pypy.rpython.error import TyperError
 
 HIGHEST_BIT = intmask(1 << (LONG_BIT - 1))
 MASK = intmask(HIGHEST_BIT - 1)
@@ -42,7 +43,7 @@
 class DictRepr(AbstractDictRepr):
 
     def __init__(self, rtyper, key_repr, value_repr, dictkey, dictvalue,
-                 custom_eq_hash=None):
+                 custom_eq_hash=None, force_non_null=False):
         self.rtyper = rtyper
         self.DICT = lltype.GcForwardReference()
         self.lowleveltype = lltype.Ptr(self.DICT)
@@ -61,6 +62,7 @@
         self.dictvalue = dictvalue
         self.dict_cache = {}
         self._custom_eq_hash_repr = custom_eq_hash
+        self.force_non_null = force_non_null
         # setup() needs to be called to finish this initialization
 
     def _externalvsinternal(self, rtyper, item_repr):
@@ -97,6 +99,13 @@
             s_value = self.dictvalue.s_value
             nullkeymarker = not self.key_repr.can_ll_be_null(s_key)
             nullvaluemarker = not self.value_repr.can_ll_be_null(s_value)
+            if self.force_non_null:
+                if not nullkeymarker:
+                    rmodel.warning("%s can be null, but forcing non-null in dict key" % s_key)
+                    nullkeymarker = True
+                if not nullvaluemarker:
+                    rmodel.warning("%s can be null, but forcing non-null in dict value" % s_value)
+                    nullvaluemarker = True
             dummykeyobj = self.key_repr.get_ll_dummyval_obj(self.rtyper,
                                                             s_key)
             dummyvalueobj = self.value_repr.get_ll_dummyval_obj(self.rtyper,
@@ -640,12 +649,15 @@
     pass
 
 
-def rtype_r_dict(hop):
+def rtype_r_dict(hop, i_force_non_null=None):
     r_dict = hop.r_result
     if not r_dict.custom_eq_hash:
         raise TyperError("r_dict() call does not return an r_dict instance")
-    v_eqfn, v_hashfn = hop.inputargs(r_dict.r_rdict_eqfn,
-                                     r_dict.r_rdict_hashfn)
+    v_eqfn = hop.inputarg(r_dict.r_rdict_eqfn, arg=0)
+    v_hashfn = hop.inputarg(r_dict.r_rdict_hashfn, arg=1)
+    if i_force_non_null is not None:
+        assert i_force_non_null == 2
+        hop.inputarg(lltype.Void, arg=2)
     cDICT = hop.inputconst(lltype.Void, r_dict.DICT)
     hop.exception_cannot_occur()
     v_result = hop.gendirectcall(ll_newdict, cDICT)
@@ -833,10 +845,16 @@
 POPITEMINDEX = lltype.Struct('PopItemIndex', ('nextindex', lltype.Signed))
 global_popitem_index = lltype.malloc(POPITEMINDEX, zero=True, immortal=True)
 
-def ll_popitem(ELEM, dic):
+def _ll_getnextitem(dic):
     entries = dic.entries
+    ENTRY = lltype.typeOf(entries).TO.OF
     dmask = len(entries) - 1
-    base = global_popitem_index.nextindex
+    if hasattr(ENTRY, 'f_hash'):
+        if entries.valid(0):
+            return 0
+        base = entries[0].f_hash
+    else:
+        base = global_popitem_index.nextindex
     counter = 0
     while counter <= dmask:
         i = (base + counter) & dmask
@@ -845,8 +863,16 @@
             break
     else:
         raise KeyError
-    global_popitem_index.nextindex += counter
-    entry = entries[i]
+    if hasattr(ENTRY, 'f_hash'):
+        entries[0].f_hash = base + counter
+    else:
+        global_popitem_index.nextindex = base + counter
+    return i
+
+ at jit.dont_look_inside
+def ll_popitem(ELEM, dic):
+    i = _ll_getnextitem(dic)
+    entry = dic.entries[i]
     r = lltype.malloc(ELEM.TO)
     r.item0 = recast(ELEM.TO.item0, entry.key)
     r.item1 = recast(ELEM.TO.item1, entry.value)
diff --git a/pypy/rpython/lltypesystem/rffi.py b/pypy/rpython/lltypesystem/rffi.py
--- a/pypy/rpython/lltypesystem/rffi.py
+++ b/pypy/rpython/lltypesystem/rffi.py
@@ -55,7 +55,7 @@
                compilation_info=ExternalCompilationInfo(),
                sandboxsafe=False, threadsafe='auto',
                _nowrapper=False, calling_conv='c',
-               oo_primitive=None, pure_function=False,
+               oo_primitive=None, elidable_function=False,
                macro=None):
     """Build an external function that will invoke the C function 'name'
     with the given 'args' types and 'result' type.
@@ -87,8 +87,8 @@
                 name, macro, ext_type, compilation_info)
         else:
             _callable = ll2ctypes.LL2CtypesCallable(ext_type, calling_conv)
-    if pure_function:
-        _callable._pure_function_ = True
+    if elidable_function:
+        _callable._elidable_function_ = True
     kwds = {}
     if oo_primitive:
         kwds['oo_primitive'] = oo_primitive
diff --git a/pypy/rpython/lltypesystem/rstr.py b/pypy/rpython/lltypesystem/rstr.py
--- a/pypy/rpython/lltypesystem/rstr.py
+++ b/pypy/rpython/lltypesystem/rstr.py
@@ -4,7 +4,7 @@
 from pypy.rlib.objectmodel import malloc_zero_filled, we_are_translated
 from pypy.rlib.objectmodel import _hash_string, enforceargs
 from pypy.rlib.debug import ll_assert
-from pypy.rlib.jit import purefunction, we_are_jitted, dont_look_inside
+from pypy.rlib.jit import elidable, we_are_jitted, dont_look_inside
 from pypy.rlib.rarithmetic import ovfcheck
 from pypy.rpython.robject import PyObjRepr, pyobj_repr
 from pypy.rpython.rmodel import inputconst, IntegerRepr
@@ -144,7 +144,7 @@
         self.ll = LLHelpers
         self.malloc = mallocunicode
 
-    @purefunction
+    @elidable
     def ll_str(self, s):
         # XXX crazy that this is here, but I don't want to break
         #     rmodel logic
@@ -159,7 +159,7 @@
             result.chars[i] = cast_primitive(Char, c)
         return result
 
-    @purefunction
+    @elidable
     def ll_encode_latin1(self, s):
         length = len(s.chars)
         result = mallocstr(length)
@@ -258,7 +258,7 @@
 
 
 class LLHelpers(AbstractLLHelpers):
-    @purefunction
+    @elidable
     def ll_str_mul(s, times):
         if times < 0:
             times = 0
@@ -280,7 +280,7 @@
             i += j
         return newstr
 
-    @purefunction
+    @elidable
     def ll_char_mul(ch, times):
         if typeOf(ch) is Char:
             malloc = mallocstr
@@ -325,8 +325,7 @@
         return s
     ll_str2unicode.oopspec = 'str.str2unicode(str)'
 
-    # it's pure but it does not look like it
-    @purefunction
+    @elidable
     def ll_strhash(s):
         # unlike CPython, there is no reason to avoid to return -1
         # but our malloc initializes the memory to zero, so we use zero as the
@@ -342,7 +341,7 @@
     def ll_strfasthash(s):
         return s.hash     # assumes that the hash is already computed
 
-    @purefunction
+    @elidable
     def ll_strconcat(s1, s2):
         len1 = len(s1.chars)
         len2 = len(s2.chars)
@@ -352,7 +351,7 @@
         return newstr
     ll_strconcat.oopspec = 'stroruni.concat(s1, s2)'
 
-    @purefunction
+    @elidable
     def ll_strip(s, ch, left, right):
         s_len = len(s.chars)
         if s_len == 0:
@@ -370,7 +369,7 @@
         s.copy_contents(s, result, lpos, 0, r_len)
         return result
 
-    @purefunction
+    @elidable
     def ll_upper(s):
         s_chars = s.chars
         s_len = len(s_chars)
@@ -387,7 +386,7 @@
             i += 1
         return result
 
-    @purefunction
+    @elidable
     def ll_lower(s):
         s_chars = s.chars
         s_len = len(s_chars)
@@ -428,7 +427,7 @@
             i += 1
         return result
 
-    @purefunction
+    @elidable
     def ll_strcmp(s1, s2):
         if not s1 and not s2:
             return True
@@ -451,7 +450,7 @@
             i += 1
         return len1 - len2
 
-    @purefunction
+    @elidable
     def ll_streq(s1, s2):
         if s1 == s2:       # also if both are NULLs
             return True
@@ -471,7 +470,7 @@
         return True
     ll_streq.oopspec = 'stroruni.equal(s1, s2)'
 
-    @purefunction
+    @elidable
     def ll_startswith(s1, s2):
         len1 = len(s1.chars)
         len2 = len(s2.chars)
@@ -487,7 +486,7 @@
 
         return True
 
-    @purefunction
+    @elidable
     def ll_endswith(s1, s2):
         len1 = len(s1.chars)
         len2 = len(s2.chars)
@@ -504,7 +503,7 @@
 
         return True
 
-    @purefunction
+    @elidable
     def ll_find_char(s, ch, start, end):
         i = start
         if end > len(s.chars):
@@ -516,7 +515,7 @@
         return -1
     ll_find_char._annenforceargs_ = [None, None, int, int]
 
-    @purefunction
+    @elidable
     def ll_rfind_char(s, ch, start, end):
         if end > len(s.chars):
             end = len(s.chars)
@@ -527,7 +526,7 @@
                 return i
         return -1
 
-    @purefunction
+    @elidable
     def ll_count_char(s, ch, start, end):
         count = 0
         i = start
@@ -595,7 +594,7 @@
             res = 0
         return res
 
-    @purefunction
+    @elidable
     def ll_search(s1, s2, start, end, mode):
         count = 0
         n = end - start
@@ -718,7 +717,7 @@
             i += 1
         return result
 
-    @purefunction
+    @elidable
     def _ll_stringslice(s1, start, stop):
         lgt = stop - start
         assert start >= 0
@@ -816,7 +815,7 @@
         item.copy_contents(s, item, j, 0, i - j)
         return res
 
-    @purefunction
+    @elidable
     def ll_replace_chr_chr(s, c1, c2):
         length = len(s.chars)
         newstr = s.malloc(length)
@@ -831,7 +830,7 @@
             j += 1
         return newstr
 
-    @purefunction
+    @elidable
     def ll_contains(s, c):
         chars = s.chars
         strlen = len(chars)
@@ -842,7 +841,7 @@
             i += 1
         return False
 
-    @purefunction
+    @elidable
     def ll_int(s, base):
         if not 2 <= base <= 36:
             raise ValueError
diff --git a/pypy/rpython/memory/gc/generation.py b/pypy/rpython/memory/gc/generation.py
--- a/pypy/rpython/memory/gc/generation.py
+++ b/pypy/rpython/memory/gc/generation.py
@@ -517,7 +517,8 @@
             objhdr.tid &= ~GCFLAG_NO_HEAP_PTRS
             self.last_generation_root_objects.append(addr_struct)
 
-    def writebarrier_before_copy(self, source_addr, dest_addr):
+    def writebarrier_before_copy(self, source_addr, dest_addr,
+                                 source_start, dest_start, length):
         """ This has the same effect as calling writebarrier over
         each element in dest copied from source, except it might reset
         one of the following flags a bit too eagerly, which means we'll have
diff --git a/pypy/rpython/memory/gc/minimark.py b/pypy/rpython/memory/gc/minimark.py
--- a/pypy/rpython/memory/gc/minimark.py
+++ b/pypy/rpython/memory/gc/minimark.py
@@ -75,10 +75,16 @@
 
 first_gcflag = 1 << (LONG_BIT//2)
 
-# The following flag is never set on young objects.  It is initially set
-# on all prebuilt and old objects, and gets cleared by the write_barrier()
-# when we write in them a pointer to a young object.
-GCFLAG_NO_YOUNG_PTRS = first_gcflag << 0
+# The following flag is set on objects if we need to do something to
+# track the young pointers that it might contain.  The flag is not set
+# on young objects (unless they are large arrays, see below), and we
+# simply assume that any young object can point to any other young object.
+# For old and prebuilt objects, the flag is usually set, and is cleared
+# when we write a young pointer to it.  For large arrays with
+# GCFLAG_HAS_CARDS, we rely on card marking to track where the
+# young pointers are; the flag GCFLAG_TRACK_YOUNG_PTRS is set in this
+# case too, to speed up the write barrier.
+GCFLAG_TRACK_YOUNG_PTRS = first_gcflag << 0
 
 # The following flag is set on some prebuilt objects.  The flag is set
 # unless the object is already listed in 'prebuilt_root_objects'.
@@ -246,17 +252,23 @@
         self.ac = ArenaCollectionClass(arena_size, page_size,
                                        small_request_threshold)
         #
-        # Used by minor collection: a list of non-young objects that
+        # Used by minor collection: a list of (mostly non-young) objects that
         # (may) contain a pointer to a young object.  Populated by
-        # the write barrier.
-        self.old_objects_pointing_to_young = self.AddressStack()
+        # the write barrier: when we clear GCFLAG_TRACK_YOUNG_PTRS, we
+        # add it to this list.
+        class Cls(self.AddressStack):
+            def append(self2, addr):
+                assert addr not in self2.tolist()
+                self.AddressStack.append(self2, addr)
+        self.objects_pointing_to_young = self.AddressStack()
         #
-        # Similar to 'old_objects_pointing_to_young', but lists objects
+        # Similar to 'objects_pointing_to_young', but lists objects
         # that have the GCFLAG_CARDS_SET bit.  For large arrays.  Note
         # that it is possible for an object to be listed both in here
-        # and in 'old_objects_pointing_to_young', in which case we
+        # and in 'objects_pointing_to_young', in which case we
         # should just clear the cards and trace it fully, as usual.
-        self.old_objects_with_cards_set = self.AddressStack()
+        # Note also that young array objects may be added to this list.
+        self.objects_with_cards_set = self.AddressStack()
         #
         # A list of all prebuilt GC objects that contain pointers to the heap
         self.prebuilt_root_objects = self.AddressStack()
@@ -625,7 +637,7 @@
             # if 'can_make_young'.  The interesting case of 'can_make_young'
             # is for large objects, bigger than the 'large_objects' threshold,
             # which are raw-malloced but still young.
-            extra_flags = GCFLAG_NO_YOUNG_PTRS
+            extra_flags = GCFLAG_TRACK_YOUNG_PTRS
             #
         else:
             # No, so proceed to allocate it externally with raw_malloc().
@@ -643,7 +655,7 @@
                 # Reserve N extra words containing card bits before the object.
                 extra_words = self.card_marking_words_for_length(length)
                 cardheadersize = WORD * extra_words
-                extra_flags = GCFLAG_HAS_CARDS
+                extra_flags = GCFLAG_HAS_CARDS | GCFLAG_TRACK_YOUNG_PTRS
                 # note that if 'can_make_young', then card marking will only
                 # be used later, after (and if) the object becomes old
             #
@@ -686,7 +698,7 @@
                 self.young_rawmalloced_objects.add(result + size_gc_header)
             else:
                 self.old_rawmalloced_objects.append(result + size_gc_header)
-                extra_flags |= GCFLAG_NO_YOUNG_PTRS
+                extra_flags |= GCFLAG_TRACK_YOUNG_PTRS
         #
         # Common code to fill the header and length of the object.
         self.init_gc_object(result, typeid, extra_flags)
@@ -777,7 +789,7 @@
     def init_gc_object_immortal(self, addr, typeid16, flags=0):
         # For prebuilt GC objects, the flags must contain
         # GCFLAG_NO_xxx_PTRS, at least initially.
-        flags |= GCFLAG_NO_HEAP_PTRS | GCFLAG_NO_YOUNG_PTRS
+        flags |= GCFLAG_NO_HEAP_PTRS | GCFLAG_TRACK_YOUNG_PTRS
         self.init_gc_object(addr, typeid16, flags)
 
     def is_in_nursery(self, addr):
@@ -870,8 +882,8 @@
         ll_assert(not self.is_in_nursery(obj),
                   "object in nursery after collection")
         # similarily, all objects should have this flag:
-        ll_assert(self.header(obj).tid & GCFLAG_NO_YOUNG_PTRS,
-                  "missing GCFLAG_NO_YOUNG_PTRS")
+        ll_assert(self.header(obj).tid & GCFLAG_TRACK_YOUNG_PTRS,
+                  "missing GCFLAG_TRACK_YOUNG_PTRS")
         # the GCFLAG_VISITED should not be set between collections
         ll_assert(self.header(obj).tid & GCFLAG_VISITED == 0,
                   "unexpected GCFLAG_VISITED")
@@ -910,7 +922,7 @@
     # for the JIT: a minimal description of the write_barrier() method
     # (the JIT assumes it is of the shape
     #  "if addr_struct.int0 & JIT_WB_IF_FLAG: remember_young_pointer()")
-    JIT_WB_IF_FLAG = GCFLAG_NO_YOUNG_PTRS
+    JIT_WB_IF_FLAG = GCFLAG_TRACK_YOUNG_PTRS
 
     @classmethod
     def JIT_max_size_of_young_obj(cls):
@@ -921,11 +933,11 @@
         return cls.minimal_size_in_nursery
 
     def write_barrier(self, newvalue, addr_struct):
-        if self.header(addr_struct).tid & GCFLAG_NO_YOUNG_PTRS:
+        if self.header(addr_struct).tid & GCFLAG_TRACK_YOUNG_PTRS:
             self.remember_young_pointer(addr_struct, newvalue)
 
     def write_barrier_from_array(self, newvalue, addr_array, index):
-        if self.header(addr_array).tid & GCFLAG_NO_YOUNG_PTRS:
+        if self.header(addr_array).tid & GCFLAG_TRACK_YOUNG_PTRS:
             if self.card_page_indices > 0:     # <- constant-folded
                 self.remember_young_pointer_from_array2(addr_array, index)
             else:
@@ -943,20 +955,23 @@
         def remember_young_pointer(addr_struct, newvalue):
             # 'addr_struct' is the address of the object in which we write.
             # 'newvalue' is the address that we are going to write in there.
+            # We know that 'addr_struct' has GCFLAG_TRACK_YOUNG_PTRS so far.
+            #
             if DEBUG:   # note: PYPY_GC_DEBUG=1 does not enable this
-                ll_assert(self.debug_is_old_object(addr_struct),
-                          "young object with GCFLAG_NO_YOUNG_PTRS")
+                ll_assert(self.debug_is_old_object(addr_struct) or
+                          self.header(addr_struct).tid & GCFLAG_HAS_CARDS != 0,
+                      "young object with GCFLAG_TRACK_YOUNG_PTRS and no cards")
             #
-            # If it seems that what we are writing is a pointer to the nursery
+            # If it seems that what we are writing is a pointer to a young obj
             # (as checked with appears_to_be_young()), then we need
-            # to remove the flag GCFLAG_NO_YOUNG_PTRS and add the old object
-            # to the list 'old_objects_pointing_to_young'.  We know that
+            # to remove the flag GCFLAG_TRACK_YOUNG_PTRS and add the object
+            # to the list 'objects_pointing_to_young'.  We know that
             # 'addr_struct' cannot be in the nursery, because nursery objects
-            # never have the flag GCFLAG_NO_YOUNG_PTRS to start with.
+            # never have the flag GCFLAG_TRACK_YOUNG_PTRS to start with.
             objhdr = self.header(addr_struct)
             if self.appears_to_be_young(newvalue):
-                self.old_objects_pointing_to_young.append(addr_struct)
-                objhdr.tid &= ~GCFLAG_NO_YOUNG_PTRS
+                self.objects_pointing_to_young.append(addr_struct)
+                objhdr.tid &= ~GCFLAG_TRACK_YOUNG_PTRS
             #
             # Second part: if 'addr_struct' is actually a prebuilt GC
             # object and it's the first time we see a write to it, we
@@ -980,16 +995,18 @@
             # 'addr_array' is the address of the object in which we write,
             # which must have an array part;  'index' is the index of the
             # item that is (or contains) the pointer that we write.
-            if DEBUG:   # note: PYPY_GC_DEBUG=1 does not enable this
-                ll_assert(self.debug_is_old_object(addr_array),
-                          "young array with GCFLAG_NO_YOUNG_PTRS")
+            # We know that 'addr_array' has GCFLAG_TRACK_YOUNG_PTRS so far.
+            #
             objhdr = self.header(addr_array)
             if objhdr.tid & GCFLAG_HAS_CARDS == 0:
                 #
+                if DEBUG:   # note: PYPY_GC_DEBUG=1 does not enable this
+                    ll_assert(self.debug_is_old_object(addr_array),
+                        "young array with no card but GCFLAG_TRACK_YOUNG_PTRS")
+                #
                 # no cards, use default logic.  Mostly copied from above.
-                self.old_objects_pointing_to_young.append(addr_array)
-                objhdr = self.header(addr_array)
-                objhdr.tid &= ~GCFLAG_NO_YOUNG_PTRS
+                self.objects_pointing_to_young.append(addr_array)
+                objhdr.tid &= ~GCFLAG_TRACK_YOUNG_PTRS
                 if objhdr.tid & GCFLAG_NO_HEAP_PTRS:
                     objhdr.tid &= ~GCFLAG_NO_HEAP_PTRS
                     self.prebuilt_root_objects.append(addr_array)
@@ -1002,9 +1019,7 @@
             bitmask = 1 << (bitindex & 7)
             #
             # If the bit is already set, leave now.
-            size_gc_header = self.gcheaderbuilder.size_gc_header
-            addr_byte = addr_array - size_gc_header
-            addr_byte = llarena.getfakearenaaddress(addr_byte) + (~byteindex)
+            addr_byte = self.get_card(addr_array, byteindex)
             byte = ord(addr_byte.char[0])
             if byte & bitmask:
                 return
@@ -1016,7 +1031,7 @@
             addr_byte.char[0] = chr(byte | bitmask)
             #
             if objhdr.tid & GCFLAG_CARDS_SET == 0:
-                self.old_objects_with_cards_set.append(addr_array)
+                self.objects_with_cards_set.append(addr_array)
                 objhdr.tid |= GCFLAG_CARDS_SET
 
         remember_young_pointer_from_array2._dont_inline_ = True
@@ -1026,9 +1041,6 @@
 
         # xxx trying it out for the JIT: a 3-arguments version of the above
         def remember_young_pointer_from_array3(addr_array, index, newvalue):
-            if DEBUG:   # note: PYPY_GC_DEBUG=1 does not enable this
-                ll_assert(self.debug_is_old_object(addr_array),
-                          "young array with GCFLAG_NO_YOUNG_PTRS")
             objhdr = self.header(addr_array)
             #
             # a single check for the common case of neither GCFLAG_HAS_CARDS
@@ -1044,8 +1056,8 @@
             else:
                 # case with cards.
                 #
-                # If the newly written address does not actually point to the
-                # nursery, leave now.
+                # If the newly written address does not actually point to a
+                # young object, leave now.
                 if not self.appears_to_be_young(newvalue):
                     return
                 #
@@ -1056,46 +1068,53 @@
                 bitmask = 1 << (bitindex & 7)
                 #
                 # If the bit is already set, leave now.
-                size_gc_header = self.gcheaderbuilder.size_gc_header
-                addr_byte = addr_array - size_gc_header
-                addr_byte = llarena.getfakearenaaddress(addr_byte) + \
-                            (~byteindex)
+                addr_byte = self.get_card(addr_array, byteindex)
                 byte = ord(addr_byte.char[0])
                 if byte & bitmask:
                     return
                 addr_byte.char[0] = chr(byte | bitmask)
                 #
                 if objhdr.tid & GCFLAG_CARDS_SET == 0:
-                    self.old_objects_with_cards_set.append(addr_array)
+                    self.objects_with_cards_set.append(addr_array)
                     objhdr.tid |= GCFLAG_CARDS_SET
                 return
             #
             # Logic for the no-cards case, put here to minimize the number
             # of checks done at the start of the function
+            if DEBUG:   # note: PYPY_GC_DEBUG=1 does not enable this
+                ll_assert(self.debug_is_old_object(addr_array),
+                        "young array with no card but GCFLAG_TRACK_YOUNG_PTRS")
+            #
             if self.appears_to_be_young(newvalue):
-                self.old_objects_pointing_to_young.append(addr_array)
-                objhdr.tid &= ~GCFLAG_NO_YOUNG_PTRS
+                self.objects_pointing_to_young.append(addr_array)
+                objhdr.tid &= ~GCFLAG_TRACK_YOUNG_PTRS
 
         remember_young_pointer_from_array3._dont_inline_ = True
         assert self.card_page_indices > 0
         self.remember_young_pointer_from_array3 = (
             remember_young_pointer_from_array3)
 
+    def get_card(self, obj, byteindex):
+        size_gc_header = self.gcheaderbuilder.size_gc_header
+        addr_byte = obj - size_gc_header
+        return llarena.getfakearenaaddress(addr_byte) + (~byteindex)
+
 
     def assume_young_pointers(self, addr_struct):
         """Called occasionally by the JIT to mean ``assume that 'addr_struct'
         may now contain young pointers.''
         """
         objhdr = self.header(addr_struct)
-        if objhdr.tid & GCFLAG_NO_YOUNG_PTRS:
-            self.old_objects_pointing_to_young.append(addr_struct)
-            objhdr.tid &= ~GCFLAG_NO_YOUNG_PTRS
+        if objhdr.tid & GCFLAG_TRACK_YOUNG_PTRS:
+            self.objects_pointing_to_young.append(addr_struct)
+            objhdr.tid &= ~GCFLAG_TRACK_YOUNG_PTRS
             #
             if objhdr.tid & GCFLAG_NO_HEAP_PTRS:
                 objhdr.tid &= ~GCFLAG_NO_HEAP_PTRS
                 self.prebuilt_root_objects.append(addr_struct)
 
-    def writebarrier_before_copy(self, source_addr, dest_addr):
+    def writebarrier_before_copy(self, source_addr, dest_addr,
+                                 source_start, dest_start, length):
         """ This has the same effect as calling writebarrier over
         each element in dest copied from source, except it might reset
         one of the following flags a bit too eagerly, which means we'll have
@@ -1103,18 +1122,36 @@
         """
         source_hdr = self.header(source_addr)
         dest_hdr = self.header(dest_addr)
-        if dest_hdr.tid & GCFLAG_NO_YOUNG_PTRS == 0:
+        if dest_hdr.tid & GCFLAG_TRACK_YOUNG_PTRS == 0:
             return True
         # ^^^ a fast path of write-barrier
         #
-        if source_hdr.tid & GCFLAG_CARDS_SET != 0:
-            # there might be young objects, let ll_arraycopy find them
-            return False
+        if source_hdr.tid & GCFLAG_HAS_CARDS != 0:
+            #
+            if source_hdr.tid & GCFLAG_TRACK_YOUNG_PTRS == 0:
+                # The source object may have random young pointers.
+                # Return False to mean "do it manually in ll_arraycopy".
+                return False
+            #
+            if source_hdr.tid & GCFLAG_CARDS_SET == 0:
+                # The source object has no young pointers at all.  Done.
+                return True
+            #
+            if dest_hdr.tid & GCFLAG_HAS_CARDS == 0:
+                # The dest object doesn't have cards.  Do it manually.
+                return False
+            #
+            if source_start != 0 or dest_start != 0:
+                # Misaligned.  Do it manually.
+                return False
+            #
+            self.manually_copy_card_bits(source_addr, dest_addr, length)
+            return True
         #
-        if source_hdr.tid & GCFLAG_NO_YOUNG_PTRS == 0:
+        if source_hdr.tid & GCFLAG_TRACK_YOUNG_PTRS == 0:
             # there might be in source a pointer to a young object
-            self.old_objects_pointing_to_young.append(dest_addr)
-            dest_hdr.tid &= ~GCFLAG_NO_YOUNG_PTRS
+            self.objects_pointing_to_young.append(dest_addr)
+            dest_hdr.tid &= ~GCFLAG_TRACK_YOUNG_PTRS
         #
         if dest_hdr.tid & GCFLAG_NO_HEAP_PTRS:
             if source_hdr.tid & GCFLAG_NO_HEAP_PTRS == 0:
@@ -1122,6 +1159,22 @@
                 self.prebuilt_root_objects.append(dest_addr)
         return True
 
+    def manually_copy_card_bits(self, source_addr, dest_addr, length):
+        # manually copy the individual card marks from source to dest
+        bytes = self.card_marking_bytes_for_length(length)
+        #
+        i = 0
+        while i < bytes:
+            addr_srcbyte = self.get_card(source_addr, i)
+            addr_dstbyte = self.get_card(dest_addr, i)
+            byte = ord(addr_srcbyte.char[0])
+            addr_dstbyte.char[0] = chr(ord(addr_dstbyte.char[0]) | byte)
+            i += 1
+        #
+        dest_hdr = self.header(dest_addr)
+        if dest_hdr.tid & GCFLAG_CARDS_SET == 0:
+            self.objects_with_cards_set.append(dest_addr)
+            dest_hdr.tid |= GCFLAG_CARDS_SET
 
     # ----------
     # Nursery collection
@@ -1138,20 +1191,28 @@
         # Note that during this step, we ignore references to further
         # young objects; only objects directly referenced by roots
         # are copied out or flagged.  They are also added to the list
-        # 'old_objects_pointing_to_young'.
+        # 'objects_pointing_to_young'.
         self.collect_roots_in_nursery()
         #
-        # If we are using card marking, do a partial trace of the arrays
-        # that are flagged with GCFLAG_CARDS_SET.
-        if self.card_page_indices > 0:
-            self.collect_cardrefs_to_nursery()
-        #
-        # Now trace objects from 'old_objects_pointing_to_young'.
-        # All nursery objects they reference are copied out of the
-        # nursery, and again added to 'old_objects_pointing_to_young'.
-        # All young raw-malloced object found is flagged GCFLAG_VISITED.
-        # We proceed until 'old_objects_pointing_to_young' is empty.
-        self.collect_oldrefs_to_nursery()
+        while True:
+            # If we are using card marking, do a partial trace of the arrays
+            # that are flagged with GCFLAG_CARDS_SET.
+            if self.card_page_indices > 0:
+                self.collect_cardrefs_to_nursery()
+            #
+            # Now trace objects from 'objects_pointing_to_young'.
+            # All nursery objects they reference are copied out of the
+            # nursery, and again added to 'objects_pointing_to_young'.
+            # All young raw-malloced object found is flagged GCFLAG_VISITED.
+            # We proceed until 'objects_pointing_to_young' is empty.
+            self.collect_oldrefs_to_nursery()
+            #
+            # We have to loop back if collect_oldrefs_to_nursery caused
+            # new objects to show up in objects_with_cards_set
+            if self.card_page_indices > 0:
+                if self.objects_with_cards_set.non_empty():
+                    continue
+            break
         #
         # Now all live nursery objects should be out.  Update the young
         # weakrefs' targets.
@@ -1184,7 +1245,7 @@
         # we don't need to trace prebuilt GcStructs during a minor collect:
         # if a prebuilt GcStruct contains a pointer to a young object,
         # then the write_barrier must have ensured that the prebuilt
-        # GcStruct is in the list self.old_objects_pointing_to_young.
+        # GcStruct is in the list self.objects_pointing_to_young.
         self.root_walker.walk_roots(
             MiniMarkGC._trace_drag_out1,  # stack roots
             MiniMarkGC._trace_drag_out1,  # static in prebuilt non-gc
@@ -1192,7 +1253,7 @@
 
     def collect_cardrefs_to_nursery(self):
         size_gc_header = self.gcheaderbuilder.size_gc_header
-        oldlist = self.old_objects_with_cards_set
+        oldlist = self.objects_with_cards_set
         while oldlist.non_empty():
             obj = oldlist.pop()
             #
@@ -1208,11 +1269,11 @@
             bytes = self.card_marking_bytes_for_length(length)
             p = llarena.getfakearenaaddress(obj - size_gc_header)
             #
-            # If the object doesn't have GCFLAG_NO_YOUNG_PTRS, then it
-            # means that it is in 'old_objects_pointing_to_young' and
+            # If the object doesn't have GCFLAG_TRACK_YOUNG_PTRS, then it
+            # means that it is in 'objects_pointing_to_young' and
             # will be fully traced by collect_oldrefs_to_nursery() just
             # afterwards.
-            if self.header(obj).tid & GCFLAG_NO_YOUNG_PTRS == 0:
+            if self.header(obj).tid & GCFLAG_TRACK_YOUNG_PTRS == 0:
                 #
                 # In that case, we just have to reset all card bits.
                 while bytes > 0:
@@ -1248,19 +1309,30 @@
 
 
     def collect_oldrefs_to_nursery(self):
-        # Follow the old_objects_pointing_to_young list and move the
+        # Follow the objects_pointing_to_young list and move the
         # young objects they point to out of the nursery.
-        oldlist = self.old_objects_pointing_to_young
+        oldlist = self.objects_pointing_to_young
         while oldlist.non_empty():
             obj = oldlist.pop()
             #
-            # Add the flag GCFLAG_NO_YOUNG_PTRS.  All live objects should have
-            # this flag set after a nursery collection.
-            self.header(obj).tid |= GCFLAG_NO_YOUNG_PTRS
+            # Check (somehow) that the flags are correct: we must not have
+            # GCFLAG_TRACK_YOUNG_PTRS so far.  But in a rare case, it's
+            # possible that the same obj is appended twice to the list
+            # (see _trace_drag_out, GCFLAG_VISITED case).  Filter it out
+            # here.
+            if self.header(obj).tid & GCFLAG_TRACK_YOUNG_PTRS != 0:
+                ll_assert(self.header(obj).tid & GCFLAG_VISITED != 0,
+                          "objects_pointing_to_young contains obj with "
+                          "GCFLAG_TRACK_YOUNG_PTRS and not GCFLAG_VISITED")
+                continue
+            #
+            # Add the flag GCFLAG_TRACK_YOUNG_PTRS.  All live objects should
+            # have this flag set after a nursery collection.
+            self.header(obj).tid |= GCFLAG_TRACK_YOUNG_PTRS
             #
             # Trace the 'obj' to replace pointers to nursery with pointers
             # outside the nursery, possibly forcing nursery objects out
-            # and adding them to 'old_objects_pointing_to_young' as well.
+            # and adding them to 'objects_pointing_to_young' as well.
             self.trace_and_drag_out_of_nursery(obj)
 
     def trace_and_drag_out_of_nursery(self, obj):
@@ -1299,7 +1371,19 @@
                 # 'obj' points to a young, raw-malloced object
                 if (self.header(obj).tid & GCFLAG_VISITED) == 0:
                     self.header(obj).tid |= GCFLAG_VISITED
-                    self.old_objects_pointing_to_young.append(obj)
+                    #
+                    # we just made 'obj' old, so we may need to add it
+                    # in the correct list:
+                    if self.header(obj).tid & GCFLAG_TRACK_YOUNG_PTRS == 0:
+                        # common case: GCFLAG_TRACK_YOUNG_PTRS is not set, so
+                        # the object may contain young pointers anywhere
+                        self.objects_pointing_to_young.append(obj)
+                    else:
+                        # large array case: the object contains card marks
+                        # that tell us where young pointers are, and it
+                        # is already in objects_with_cards_set.
+                        ll_assert(self.header(obj).tid & GCFLAG_HAS_CARDS != 0,
+                                  "neither YOUNG_PTRS nor HAS_CARDS??")
             return
         #
         # If 'obj' was already forwarded, change it to its forwarding address.
@@ -1346,11 +1430,11 @@
         # Change the original pointer to this object.
         root.address[0] = newobj
         #
-        # Add the newobj to the list 'old_objects_pointing_to_young',
+        # Add the newobj to the list 'objects_pointing_to_young',
         # because it can contain further pointers to other young objects.
         # We will fix such references to point to the copy of the young
-        # objects when we walk 'old_objects_pointing_to_young'.
-        self.old_objects_pointing_to_young.append(newobj)
+        # objects when we walk 'objects_pointing_to_young'.
+        self.objects_pointing_to_young.append(newobj)
 
 
     def _malloc_out_of_nursery(self, totalsize):
diff --git a/pypy/rpython/memory/gc/test/test_direct.py b/pypy/rpython/memory/gc/test/test_direct.py
--- a/pypy/rpython/memory/gc/test/test_direct.py
+++ b/pypy/rpython/memory/gc/test/test_direct.py
@@ -539,27 +539,61 @@
         hdr_src = self.gc.header(addr_src)
         hdr_dst = self.gc.header(addr_dst)
         #
-        assert hdr_src.tid & minimark.GCFLAG_NO_YOUNG_PTRS
-        assert hdr_dst.tid & minimark.GCFLAG_NO_YOUNG_PTRS
+        assert hdr_src.tid & minimark.GCFLAG_TRACK_YOUNG_PTRS
+        assert hdr_dst.tid & minimark.GCFLAG_TRACK_YOUNG_PTRS
         #
-        res = self.gc.writebarrier_before_copy(addr_src, addr_dst)
+        res = self.gc.writebarrier_before_copy(addr_src, addr_dst, 0, 0, 10)
         assert res
-        assert hdr_dst.tid & minimark.GCFLAG_NO_YOUNG_PTRS
+        assert hdr_dst.tid & minimark.GCFLAG_TRACK_YOUNG_PTRS
         #
-        hdr_src.tid &= ~minimark.GCFLAG_NO_YOUNG_PTRS  # pretend we have young ptrs
-        res = self.gc.writebarrier_before_copy(addr_src, addr_dst)
+        hdr_src.tid &= ~minimark.GCFLAG_TRACK_YOUNG_PTRS  # pretend we have young ptrs
+        res = self.gc.writebarrier_before_copy(addr_src, addr_dst, 0, 0, 10)
         assert res # we optimized it
-        assert hdr_dst.tid & minimark.GCFLAG_NO_YOUNG_PTRS == 0 # and we copied the flag
+        assert hdr_dst.tid & minimark.GCFLAG_TRACK_YOUNG_PTRS == 0 # and we copied the flag
         #
-        # in this case, we have cards, so GCFLAG_NO_YOUNG_PTRS is set (because
-        # cards takes precedence over it)
-        hdr_src.tid |= minimark.GCFLAG_NO_YOUNG_PTRS
-        hdr_dst.tid |= minimark.GCFLAG_NO_YOUNG_PTRS
+        hdr_src.tid |= minimark.GCFLAG_TRACK_YOUNG_PTRS
+        hdr_dst.tid |= minimark.GCFLAG_TRACK_YOUNG_PTRS
+        hdr_src.tid |= minimark.GCFLAG_HAS_CARDS
         hdr_src.tid |= minimark.GCFLAG_CARDS_SET
-        res = self.gc.writebarrier_before_copy(addr_src, addr_dst)
+        # hdr_dst.tid does not have minimark.GCFLAG_HAS_CARDS
+        res = self.gc.writebarrier_before_copy(addr_src, addr_dst, 0, 0, 10)
         assert not res # there might be young ptrs, let ll_arraycopy to find them
-        assert hdr_dst.tid & minimark.GCFLAG_NO_YOUNG_PTRS
 
-        
+    def test_writebarrier_before_copy_preserving_cards(self):
+        from pypy.rpython.lltypesystem import llarena
+        from pypy.rpython.memory.gc import minimark
+        tid = self.get_type_id(VAR)
+        largeobj_size =  self.gc.nonlarge_max + 1
+        addr_src = self.gc.external_malloc(tid, largeobj_size)
+        addr_dst = self.gc.external_malloc(tid, largeobj_size)
+        hdr_src = self.gc.header(addr_src)
+        hdr_dst = self.gc.header(addr_dst)
+        #
+        assert hdr_src.tid & minimark.GCFLAG_HAS_CARDS
+        assert hdr_dst.tid & minimark.GCFLAG_HAS_CARDS
+        #
+        young_p = self.malloc(S)
+        self.gc.write_barrier_from_array(young_p, addr_src, 0)
+        index_in_third_page = int(2.5 * self.gc.card_page_indices)
+        assert index_in_third_page < largeobj_size
+        self.gc.write_barrier_from_array(young_p, addr_src,
+                                         index_in_third_page)
+        #
+        assert hdr_src.tid & minimark.GCFLAG_CARDS_SET
+        addr_byte = self.gc.get_card(addr_src, 0)
+        assert ord(addr_byte.char[0]) == 0x01 | 0x04  # bits 0 and 2
+        #
+        res = self.gc.writebarrier_before_copy(addr_src, addr_dst,
+                                             0, 0, 2*self.gc.card_page_indices)
+        assert res
+        #
+        assert hdr_dst.tid & minimark.GCFLAG_CARDS_SET
+        addr_byte = self.gc.get_card(addr_dst, 0)
+        assert ord(addr_byte.char[0]) == 0x01 | 0x04  # bits 0 and 2
+
+    test_writebarrier_before_copy_preserving_cards.GC_PARAMS = {
+        "card_page_indices": 4}
+
+
 class TestMiniMarkGCFull(DirectGCTest):
     from pypy.rpython.memory.gc.minimark import MiniMarkGC as GCClass
diff --git a/pypy/rpython/memory/gctransform/framework.py b/pypy/rpython/memory/gctransform/framework.py
--- a/pypy/rpython/memory/gctransform/framework.py
+++ b/pypy/rpython/memory/gctransform/framework.py
@@ -322,7 +322,8 @@
         if hasattr(GCClass, 'writebarrier_before_copy'):
             self.wb_before_copy_ptr = \
                     getfn(GCClass.writebarrier_before_copy.im_func,
-                    [s_gc] + [annmodel.SomeAddress()] * 2, annmodel.SomeBool())
+                    [s_gc] + [annmodel.SomeAddress()] * 2 +
+                    [annmodel.SomeInteger()] * 3, annmodel.SomeBool())
         elif GCClass.needs_write_barrier:
             raise NotImplementedError("GC needs write barrier, but does not provide writebarrier_before_copy functionality")
 
@@ -884,7 +885,7 @@
         dest_addr = hop.genop('cast_ptr_to_adr', [op.args[1]],
                                 resulttype=llmemory.Address)
         hop.genop('direct_call', [self.wb_before_copy_ptr, self.c_const_gc,
-                                  source_addr, dest_addr],
+                                  source_addr, dest_addr] + op.args[2:],
                   resultvar=op.result)
 
     def gct_weakref_create(self, hop):
diff --git a/pypy/rpython/memory/gctransform/test/test_framework.py b/pypy/rpython/memory/gctransform/test/test_framework.py
--- a/pypy/rpython/memory/gctransform/test/test_framework.py
+++ b/pypy/rpython/memory/gctransform/test/test_framework.py
@@ -163,7 +163,8 @@
     GC_PARAMS = {}
     class GCClass(MarkSweepGC):
         needs_write_barrier = True
-        def writebarrier_before_copy(self, source, dest):
+        def writebarrier_before_copy(self, source, dest,
+                                     source_start, dest_start, length):
             return True
 
 def write_barrier_check(spaceop, needs_write_barrier=True):
diff --git a/pypy/rpython/memory/gcwrapper.py b/pypy/rpython/memory/gcwrapper.py
--- a/pypy/rpython/memory/gcwrapper.py
+++ b/pypy/rpython/memory/gcwrapper.py
@@ -136,11 +136,14 @@
         ptr = lltype.cast_opaque_ptr(llmemory.GCREF, ptr)
         return self.gc.id(ptr)
 
-    def writebarrier_before_copy(self, source, dest):
+    def writebarrier_before_copy(self, source, dest,
+                                 source_start, dest_start, length):
         if self.gc.needs_write_barrier:
             source_addr = llmemory.cast_ptr_to_adr(source)
             dest_addr   = llmemory.cast_ptr_to_adr(dest)
-            return self.gc.writebarrier_before_copy(source_addr, dest_addr)
+            return self.gc.writebarrier_before_copy(source_addr, dest_addr,
+                                                    source_start, dest_start,
+                                                    length)
         else:
             return True
 
diff --git a/pypy/rpython/memory/support.py b/pypy/rpython/memory/support.py
--- a/pypy/rpython/memory/support.py
+++ b/pypy/rpython/memory/support.py
@@ -140,6 +140,14 @@
             self.foreach(_add_in_dict, result)
             return result
 
+        def tolist(self):
+            """NOT_RPYTHON.  Returns the content as a list."""
+            lst = []
+            def _add(obj, lst):
+                lst.append(obj)
+            self.foreach(_add, lst)
+            return lst
+
         def remove(self, addr):
             """Remove 'addr' from the stack.  The addr *must* be in the list,
             and preferrably near the top.
diff --git a/pypy/rpython/ootypesystem/rdict.py b/pypy/rpython/ootypesystem/rdict.py
--- a/pypy/rpython/ootypesystem/rdict.py
+++ b/pypy/rpython/ootypesystem/rdict.py
@@ -18,7 +18,7 @@
 
 class DictRepr(AbstractDictRepr):
     def __init__(self, rtyper, key_repr, value_repr, dictkey, dictvalue,
-                 custom_eq_hash=None):
+                 custom_eq_hash=None, force_non_null=False):
         self.rtyper = rtyper
         self.custom_eq_hash = custom_eq_hash is not None
 
diff --git a/pypy/rpython/rdict.py b/pypy/rpython/rdict.py
--- a/pypy/rpython/rdict.py
+++ b/pypy/rpython/rdict.py
@@ -15,6 +15,7 @@
         dictvalue = self.dictdef.dictvalue
         s_key     = dictkey  .s_value
         s_value   = dictvalue.s_value
+        force_non_null = self.dictdef.force_non_null
         if (s_key.__class__ is annmodel.SomeObject and s_key.knowntype == object and
             s_value.__class__ is annmodel.SomeObject and s_value.knowntype == object):
             return robject.pyobj_repr
@@ -29,7 +30,8 @@
                                                      lambda: rtyper.getrepr(s_value),
                                                      dictkey,
                                                      dictvalue,
-                                                     custom_eq_hash)
+                                                     custom_eq_hash,
+                                                     force_non_null)
 
     def rtyper_makekey(self):
         self.dictdef.dictkey  .dont_change_any_more = True
diff --git a/pypy/rpython/test/test_rdict.py b/pypy/rpython/test/test_rdict.py
--- a/pypy/rpython/test/test_rdict.py
+++ b/pypy/rpython/test/test_rdict.py
@@ -598,6 +598,29 @@
         res = self.interpret(func, [])
         assert res in [5263, 6352]
 
+    def test_dict_popitem_hash(self):
+        def deq(n, m):
+            return n == m
+        def dhash(n):
+            return ~n
+        def func():
+            d = r_dict(deq, dhash)
+            d[5] = 2
+            d[6] = 3
+            k1, v1 = d.popitem()
+            assert len(d) == 1
+            k2, v2 = d.popitem()
+            try:
+                d.popitem()
+            except KeyError:
+                pass
+            else:
+                assert 0, "should have raised KeyError"
+            assert len(d) == 0
+            return k1*1000 + v1*100 + k2*10 + v2
+
+        res = self.interpret(func, [])
+        assert res in [5263, 6352]
 
 class TestLLtype(BaseTestRdict, LLRtypeMixin):
     def test_dict_but_not_with_char_keys(self):
@@ -860,6 +883,25 @@
         res = f()
         assert res == 1
 
+    def test_nonnull_hint(self):
+        def eq(a, b):
+            return a == b
+        def rhash(a):
+            return 3
+        
+        def func(i):
+            d = r_dict(eq, rhash, force_non_null=True)
+            if not i:
+                d[None] = i
+            else:
+                d[str(i)] = i
+            return "12" in d, d
+
+        llres = self.interpret(func, [12])
+        assert llres.item0 == 1
+        DICT = lltype.typeOf(llres.item1)
+        assert sorted(DICT.TO.entries.TO.OF._flds) == ['f_hash', 'key', 'value']
+
     # ____________________________________________________________
 
 
diff --git a/pypy/tool/jitlogparser/parser.py b/pypy/tool/jitlogparser/parser.py
--- a/pypy/tool/jitlogparser/parser.py
+++ b/pypy/tool/jitlogparser/parser.py
@@ -121,6 +121,9 @@
     def getcode(self):
         return self.code
 
+    def has_valid_code(self):
+        return self.code is not None
+
     def getopcode(self):
         return self.code.map[self.bytecode_no]
 
@@ -220,6 +223,12 @@
         return self._lineset
     lineset = property(getlineset)
 
+    def has_valid_code(self):
+        for chunk in self.chunks:
+            if not chunk.has_valid_code():
+                return False
+        return True
+
     def _compute_linerange(self):
         self._lineset = set()
         minline = sys.maxint
diff --git a/pypy/tool/jitlogparser/test/test_parser.py b/pypy/tool/jitlogparser/test/test_parser.py
--- a/pypy/tool/jitlogparser/test/test_parser.py
+++ b/pypy/tool/jitlogparser/test/test_parser.py
@@ -168,7 +168,7 @@
     []
     int_add(0, 1)
     ''')
-    loops = LoopStorage().reconnect_loops([main, bridge])
+    LoopStorage().reconnect_loops([main, bridge])
     assert adjust_bridges(main, {})[1].name == 'guard_true'
     assert adjust_bridges(main, {'loop-13': True})[1].name == 'int_add'
 


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