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gh-106581: Fix two bugs in the code generator's copy optimization (#108380)

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I was comparing the last preceding poke with the *last* peek,
rather than the *first* peek.

Unfortunately this bug obscured another bug:
When the last preceding poke is UNUSED, the first peek disappears,
leaving the variable unassigned. This is how I fixed it:

- Rename CopyEffect to CopyItem.
- Change CopyItem to contain StackItems instead of StackEffects.
- Update those StackItems when adjusting the manager higher or lower.
- Assert that those StackItems' offsets are equivalent.
- Other clever things.

---------

Co-authored-by: Irit Katriel <1055913+iritkatriel@users.noreply.github.com>
This commit is contained in:
Guido van Rossum 2023-08-24 12:10:51 -07:00 • committed by GitHub
parent c494fb333b
commit 88941d665f
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2 changed files with 62 additions and 20 deletions
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3
Python/generated_cases.c.h generated
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@ -3833,7 +3833,6 @@
DEOPT_IF(code->co_argcount != oparg + (self_or_null != NULL), CALL);
}
// _CHECK_STACK_SPACE
callable = stack_pointer[-2 - oparg];
{
PyFunctionObject *func = (PyFunctionObject *)callable;
PyCodeObject *code = (PyCodeObject *)func->func_code;
@ -3841,8 +3840,6 @@
}
// _INIT_CALL_PY_EXACT_ARGS
args = stack_pointer - oparg;
self_or_null = stack_pointer[-1 - oparg];
callable = stack_pointer[-2 - oparg];
{
int argcount = oparg;
if (self_or_null != NULL) {