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gh-106529: Make FOR_ITER a viable uop (#112134)

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This uses the new mechanism whereby certain uops
are replaced by others during translation,
using the `_PyUop_Replacements` table.
We further special-case the `_FOR_ITER_TIER_TWO` uop
to update the deoptimization target to point
just past the corresponding `END_FOR` opcode.

Two tiny code cleanups are also part of this PR.
This commit is contained in:
Guido van Rossum 2023-11-20 10:08:53 -08:00 • committed by GitHub
parent d59feb5dbe
commit 1995955173
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8 changed files with 138 additions and 43 deletions
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23
Python/bytecodes.c
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@ -2369,7 +2369,7 @@ dummy_func(
goto enter_tier_one;
}
replaced op(_POP_JUMP_IF_FALSE, (unused/1, cond -- )) {
replaced op(_POP_JUMP_IF_FALSE, (unused/1, cond -- )) {
assert(PyBool_Check(cond));
int flag = Py_IsFalse(cond);
#if ENABLE_SPECIALIZATION
@ -2513,7 +2513,7 @@ dummy_func(
#endif /* ENABLE_SPECIALIZATION */
}
op(_FOR_ITER, (iter -- iter, next)) {
replaced op(_FOR_ITER, (iter -- iter, next)) {
/* before: [iter]; after: [iter, iter()] *or* [] (and jump over END_FOR.) */
next = (*Py_TYPE(iter)->tp_iternext)(iter);
if (next == NULL) {
@ -2536,6 +2536,25 @@ dummy_func(
// Common case: no jump, leave it to the code generator
}
op(_FOR_ITER_TIER_TWO, (iter -- iter, next)) {
/* before: [iter]; after: [iter, iter()] *or* [] (and jump over END_FOR.) */
next = (*Py_TYPE(iter)->tp_iternext)(iter);
if (next == NULL) {
if (_PyErr_Occurred(tstate)) {
if (!_PyErr_ExceptionMatches(tstate, PyExc_StopIteration)) {
GOTO_ERROR(error);
}
_PyErr_Clear(tstate);
}
/* iterator ended normally */
Py_DECREF(iter);
STACK_SHRINK(1);
/* The translator sets the deopt target just past END_FOR */
DEOPT_IF(true);
}
// Common case: no jump, leave it to the code generator
}
macro(FOR_ITER) = _SPECIALIZE_FOR_ITER + _FOR_ITER;
inst(INSTRUMENTED_FOR_ITER, (unused/1 -- )) {