[mypyc] Move private generator spills from environ to generator objects - #21955
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Keep the continuation label and the spill slots added by the post-IRBuild liveness pass for temporary operation results that remain live across a yield on the generator object, even when the generator needs a separate closure environment. Source-level generator variables remain in that shared environment, since nested functions may capture and access them independently. Spills emitted explicitly during IRBuild, including spillable registers, are also unchanged and remain in the environment. The helper-only state is protected by the generator running flag, unlike a closure environment that nested functions can access independently. Keeping it on the private generator frame lets free-threaded builds use plain attribute access safely. Include the owning class name in spill attributes as well, so spills from overriding generator methods cannot alias inherited fields with different native types.
p-sawicki
approved these changes
Sep 7, 2026
JukkaL
changed the title
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Move the continuation label and the spill slots added by the
temp liveness pass (for temporary op results that survive
across a yield) to the generator object, even when the
generator needs a separate closure environment.
Locals still remain in the shared environment, since nested
functions may capture and access them independently. Spills
emitted explicitly during irbuild, are also unchanged and remain
in the environment. I'll fix some of these in follow-up PR(s).
The state migrated to the generator is protected by the generator
running flag, unlike a closure environment that nested functions
can access without restriction. Keeping it on the private generator
frame lets free-threaded builds use plain attribute access safely.
Include the owning class name in spill attributes as well, so spills
from overriding generator methods cannot alias inherited fields
with different native types.
I used a microbenchmark to validate that this makes spilled
values over suspends faster on free-threaded Python 3.14.
I used coding agent assist.