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GH-128685: Specialize (rather than quicken) LOAD_CONST into LOAD_CONST_[IM]MORTAL #128708

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Merged
markshannon merged 4 commits into from
Jan 13, 2025
Merged

GH-128685: Specialize (rather than quicken) LOAD_CONST into LOAD_CONST_[IM]MORTAL #128708

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e7a7f22
Specialize (rather than quicken) LOAD_CONST into LOAD_CONST_[IM]MORTAL
markshannon Jan 10, 2025
043f978
Account for LOAD_CONST_MORTAL in jit optimizer.
markshannon Jan 10, 2025
d342864
Disable specialization for free-threaded build
markshannon Jan 10, 2025
6cc0241
#if not #ifdef
markshannon Jan 10, 2025
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Disable specialization for free-threaded build
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@markshannon
markshannon committed Jan 10, 2025
commit d342864a1407151bae8d6b93864d298eb884a91f
2 changes: 2 additions & 0 deletions Python/bytecodes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -294,9 +294,11 @@ dummy_func(
* marshalling can intern strings and make them immortal. */
PyObject *obj = GETITEM(FRAME_CO_CONSTS, oparg);
value = PyStackRef_FromPyObjectNew(obj);
#ifdef ENABLE_SPECIALIZATION
if (this_instr->op.code == LOAD_CONST) {
this_instr->op.code = _Py_IsImmortal(obj) ? LOAD_CONST_IMMORTAL : LOAD_CONST_MORTAL;
}
#endif
}
Comment on lines +292 to +302
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@brandtbucher brandtbucher Jan 10, 2025

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Why the check for this_instr->op.code == LOAD_CONST?

Also, minor, but maybe a bit more idiomatic with the rest of the bytecode definitions to split the specializing part out and reuse the code for loading the const? I think this would also make LOAD_CONST a viable tier two instruction (which it currently isn't). Though actually tracing through one should be rare, I can think of cases where it might happen.

Suggested change
inst(LOAD_CONST, (-- value)) {
/* We can't do this in the bytecode compiler as
* marshalling can intern strings and make them immortal. */
PyObject *obj = GETITEM(FRAME_CO_CONSTS, oparg);
value = PyStackRef_FromPyObjectNew(obj);
#if ENABLE_SPECIALIZATION
if (this_instr->op.code == LOAD_CONST) {
this_instr->op.code = _Py_IsImmortal(obj) ? LOAD_CONST_IMMORTAL : LOAD_CONST_MORTAL;
}
#endif
}
specializing op(_SPECIALIZE_LOAD_CONST, (--)) {
/* We can't do this in the bytecode compiler as
* marshalling can intern strings and make them immortal. */
#if ENABLE_SPECIALIZATION
this_instr->op.code = _Py_IsImmortal(obj) ? LOAD_CONST_IMMORTAL : LOAD_CONST_MORTAL;
#endif
}
macro(LOAD_CONST) = _SPECIALIZE_LOAD_CONST + LOAD_CONST_MORTAL;

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@markshannon markshannon Jan 13, 2025

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Why the check for this_instr->op.code == LOAD_CONST?

Instrumentation. The opcode might be INSTRUMENTED_LINE for example.

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@markshannon markshannon Jan 13, 2025

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split the specializing part out

The specializing part needs to load the value to test it, so separating out the specialization just duplicates that.


inst(LOAD_CONST_MORTAL, (-- value)) {
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2 changes: 2 additions & 0 deletions Python/generated_cases.c.h
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