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GeezerVison is showing github.com — gh-146381: Fold frozendict(key=const, ...) calls to LOAD_CONST by corona10 · Pull Request #146423 · python/cpython

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@corona10

@corona10 corona10 commented Mar 25, 2026 •
edited by brianschubert
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This PR folds frozendict calls into LOAD_CONST at compile time.

This is a prerequisite for JIT constant folding of frozendict lookups. Without this, frozendict compiles to CALL_KW, which the JIT cannot recognize as a constant. With this change, it becomes LOAD_CONST frozendict(...), enabling the JIT to promote it and fold subscript operations like d['x'] at optimization time.

Without codegen-level folding like this, supporting frozendict constants in the JIT would likely require introducing a new literal syntax (e.g., <1: 3, 5: 6>) at the language level, and it might need a PEP for this change.

cc @vstinner

  • Issue: Fold _BINARY_OP_SUBSCR_DICT for promoted frozendict constants #146381

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@corona10
pythongh-146381: Fold frozendict(key=const, ...) calls to LOAD_CONST
a09aef5
@corona10
corona10 requested a review from Fidget-Spinner March 25, 2026 14:23
@corona10
corona10 requested review from FFY00, ZeroIntensity, ericsnowcurrently, iritkatriel and markshannon as code owners March 25, 2026 14:23
@bedevere-app bedevere-app Bot added the awaiting core review label Mar 25, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Mar 25, 2026
Fold _BINARY_OP_SUBSCR_DICT for promoted frozendict constants #146381
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@corona10

corona10 commented Mar 25, 2026 •
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## main
5           LOAD_GLOBAL              1 (frozendict + NULL)
LOAD_SMALL_INT           1
LOAD_SMALL_INT           2
LOAD_CONST               1 (('x', 'y'))
CALL_KW                  2
STORE_FAST               0 (d)


## gh-146381
5           LOAD_GLOBAL              0 (frozendict)
COPY                     1
LOAD_COMMON_CONSTANT     7 (frozendict)
IS_OP                    0 (is)
POP_JUMP_IF_FALSE        4 (to L1)
NOT_TAKEN
POP_TOP
LOAD_CONST               0 (frozendict({'x': 1, 'y': 2}))  ← compile-time constant
JUMP_FORWARD             8 (to L2)
L1:     PUSH_NULL
LOAD_SMALL_INT           1
LOAD_SMALL_INT           2
LOAD_CONST               1 (('x', 'y'))
CALL_KW                  2                                  ← fallback
L2:     STORE_FAST               0 (d)
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@corona10
corona10 marked this pull request as draft March 25, 2026 14:29
@bedevere-app bedevere-app Bot removed the awaiting core review label Mar 25, 2026
@corona10

corona10 commented Mar 25, 2026

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Since @Fidget-Spinner suggeted to optimize from JIT pipeline directly, I covert this PR to the draft.
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@corona10 corona10 closed this Apr 4, 2026
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@Fidget-Spinner Fidget-Spinner Awaiting requested review from Fidget-Spinner
@ericsnowcurrently ericsnowcurrently Awaiting requested review from ericsnowcurrently ericsnowcurrently is a code owner
@ZeroIntensity ZeroIntensity Awaiting requested review from ZeroIntensity ZeroIntensity is a code owner
@FFY00 FFY00 Awaiting requested review from FFY00 FFY00 is a code owner
@markshannon markshannon Awaiting requested review from markshannon markshannon is a code owner
@iritkatriel iritkatriel Awaiting requested review from iritkatriel iritkatriel is a code owner

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@corona10
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