[pypy-svn] pypy default: (alex, kleptog): optimize int_{l, r}shift where the second argument is 0.

[alex_gaynor]

Author: Alex Gaynor <alex.gaynor at gmail.com>
Branch: 
Changeset: r43265:aa9754ba032c
Date: 2011-04-09 16:49 -0400
http://bitbucket.org/pypy/pypy/changeset/aa9754ba032c/

Log:	(alex, kleptog): optimize int_{l,r}shift where the second argument
	is 0.

diff --git a/pypy/jit/metainterp/test/test_optimizeopt.py b/pypy/jit/metainterp/test/test_optimizeopt.py
--- a/pypy/jit/metainterp/test/test_optimizeopt.py
+++ b/pypy/jit/metainterp/test/test_optimizeopt.py
@@ -2757,7 +2757,7 @@
         """
         self.optimize_loop(ops, expected)
 
-    def test_fold_partially_constant_ops(self):
+    def test_fold_partially_constant_add_sub(self):
         ops = """
         [i0]
         i1 = int_sub(i0, 0)
@@ -2791,7 +2791,7 @@
         """
         self.optimize_loop(ops, expected)
 
-    def test_fold_partially_constant_ops_ovf(self):
+    def test_fold_partially_constant_add_sub_ovf(self):
         ops = """
         [i0]
         i1 = int_sub_ovf(i0, 0)
@@ -2828,6 +2828,21 @@
         """
         self.optimize_loop(ops, expected)
 
+    def test_fold_partially_constant_shift(self):
+        ops = """
+        [i0]
+        i1 = int_lshift(i0, 0)
+        i2 = int_rshift(i1, 0)
+        i3 = int_eq(i2, i0)
+        guard_true(i3) []
+        jump(i2)
+        """
+        expected = """
+        [i0]
+        jump(i0)
+        """
+        self.optimize_loop(ops, expected)
+
     # ----------
 
 class TestLLtype(OptimizeOptTest, LLtypeMixin):

diff --git a/pypy/jit/metainterp/optimizeopt/rewrite.py b/pypy/jit/metainterp/optimizeopt/rewrite.py
--- a/pypy/jit/metainterp/optimizeopt/rewrite.py
+++ b/pypy/jit/metainterp/optimizeopt/rewrite.py
@@ -154,6 +154,24 @@
 
             self.emit_operation(op)
 
+    def optimize_INT_LSHIFT(self, op):
+        v1 = self.getvalue(op.getarg(0))
+        v2 = self.getvalue(op.getarg(1))
+
+        if v2.is_constant() and v2.box.getint() == 0:
+            self.make_equal_to(op.result, v1)
+        else:
+            self.emit_operation(op)
+
+    def optimize_INT_RSHIFT(self, op):
+        v1 = self.getvalue(op.getarg(0))
+        v2 = self.getvalue(op.getarg(1))
+
+        if v2.is_constant() and v2.box.getint() == 0:
+            self.make_equal_to(op.result, v1)
+        else:
+            self.emit_operation(op)
+
     def optimize_CALL_PURE(self, op):
         arg_consts = []
         for i in range(op.numargs()):