gh-133371: Don't optimize LOAD_FAST instructions whose local is killed by DELETE_FAST
#133383
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…_FAST` In certain cases it's possible for locals loaded by `LOAD_FAST` instructions to be on the stack when the local is killed by `DEL_FAST`. These `LOAD_FAST` instructions should not be optimized into `LOAD_FAST_BORROW` as the strong reference in the frame is killed while there is still a reference on the stack.
mpage
changed the title
LOAD_FAST instructions whose local is killed by DEL_FASTLOAD_FAST instructions whose local is killed by DELETE_FAST
| case DELETE_FAST: { | ||
| kill_local(instr_flags, &refs, oparg); | ||
| break; | ||
| } | ||
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FWIW: This change by itself is not enough to make the crash in test_asyncio go away.
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When you're done making the requested changes, leave the comment: |
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@gvanrossum - This fixes both of the repros in the linked issue. Even if this doesn't fix the original issue, it's worth merging by itself. |
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@gvanrossum - I forgot to bump the magic number. I suspect that you have some cached bytecode. I've bumped the magic number, double checked that this fixes both of the repros on the linked issue, and applied this on top of the affected PR and verified that it fixes the crash in |
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I have made the requested changes; please review again |
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Thanks for making the requested changes! @Yhg1s, @gvanrossum, @Fidget-Spinner: please review the changes made to this pull request. |
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I think the hypothesis failure is unrelated to this PR. It looks like |
Yes. This optimization happens statically during bytecode compilation. Maybe you are thinking of the specializing interpreter, which optimizes the compiled bytecode at runtime? |
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Go ahead and merge then! |
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Thanks! |
In certain cases it's possible for locals loaded by
LOAD_FASTinstructions to be on the stack when the local is killed byDELETE_FAST. TheseLOAD_FASTinstructions should not be optimized intoLOAD_FAST_BORROWas the strong reference in the frame is killed while there is still a reference on the stack.