[pypy-dev] Number of constants in a jitted rpython interpreter

[Zariko Taba]

Hi pypy !

I'm still exploring rpython and I face a problem when adding a jit to an
interpreter.
In Assembler class (pypy.jit.codewriter.assembler), in emit_const method, it
seems to be assumed that there is no more than 256 constants. (constant
seems to be accessed in a array with a 1 byte index).

If I try to translate an interpreter with more than 256 constant objects
(like string ?), I get this error :

[translation:ERROR] Error:
[translation:ERROR]  Traceback (most recent call last):
[translation:ERROR]    File
"/home/olivier/workspace/talstai_ext/pypy-1.6-src/pypy/translator/goal/translate.py",
line 308, in main
[translation:ERROR]     drv.proceed(goals)
[translation:ERROR]    File
"/home/olivier/workspace/talstai_ext/pypy-1.6-src/pypy/translator/driver.py",
line 810, in proceed
[translation:ERROR]     return self._execute(goals, task_skip =
self._maybe_skip())
[translation:ERROR]    File
"/home/olivier/workspace/talstai_ext/pypy-1.6-src/pypy/translator/tool/taskengine.py",
line 116, in _execute
[translation:ERROR]     res = self._do(goal, taskcallable, *args, **kwds)
[translation:ERROR]    File
"/home/olivier/workspace/talstai_ext/pypy-1.6-src/pypy/translator/driver.py",
line 286, in _do
[translation:ERROR]     res = func()
[translation:ERROR]    File
"/home/olivier/workspace/talstai_ext/pypy-1.6-src/pypy/translator/driver.py",
line 397, in task_pyjitpl_lltype
[translation:ERROR]     backend_name=self.config.translation.jit_backend,
inline=True)
[translation:ERROR]    File
"/home/olivier/workspace/talstai_ext/pypy-1.6-src/pypy/jit/metainterp/warmspot.py",
line 42, in apply_jit
[translation:ERROR]     **kwds)
[translation:ERROR]    File
"/home/olivier/workspace/talstai_ext/pypy-1.6-src/pypy/jit/metainterp/warmspot.py",
line 199, in __init__
[translation:ERROR]     self.codewriter.make_jitcodes(verbose=verbose)
[translation:ERROR]    File
"/home/olivier/workspace/talstai_ext/pypy-1.6-src/pypy/jit/codewriter/codewriter.py",
line 72, in make_jitcodes
[translation:ERROR]     self.transform_graph_to_jitcode(graph, jitcode,
verbose)
[translation:ERROR]    File
"/home/olivier/workspace/talstai_ext/pypy-1.6-src/pypy/jit/codewriter/codewriter.py",
line 61, in transform_graph_to_jitcode
[translation:ERROR]     self.assembler.assemble(ssarepr, jitcode)
[translation:ERROR]    File
"/home/olivier/workspace/talstai_ext/pypy-1.6-src/pypy/jit/codewriter/assembler.py",
line 35, in assemble
[translation:ERROR]     self.write_insn(insn)
[translation:ERROR]    File
"/home/olivier/workspace/talstai_ext/pypy-1.6-src/pypy/jit/codewriter/assembler.py",
line 135, in write_insn
[translation:ERROR]     is_short = self.emit_const(x, kind,
allow_short=True)
[translation:ERROR]    File
"/home/olivier/workspace/talstai_ext/pypy-1.6-src/pypy/jit/codewriter/assembler.py",
line 108, in emit_const
[translation:ERROR]     self.code.append(chr(self.constants_dict[key]))
[translation:ERROR]  ValueError: character code not in range(256)

With this snippet of code :

self.constants_dict[key] = 256 - len(constants)

If len(constants) is 257,
then self.constants_dict[key] is -1
and chr(-1) raise the ValueError.

I attached a (really) stupid example to reproduce.
When I browse pypy sources in rpython, I can't believe there is less than
256 constants of type 'ref'.

What do you think ? Did I miss something ?

Thanks !

Zariko.
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