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gh-131798: Small improvements toremove_unneeded_uops#134554
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tomasr8 commentedMay 22, 2025
| @@ -617,7 +618,7 @@ remove_unneeded_uops(_PyUOpInstruction *buffer, int buffer_size) | |||
| while (op_skip[last->opcode]) { | |||
| last--; | |||
| } | |||
| if (op_without_push[last->opcode]) { | |||
| if (op_without_push[last->opcode]&&op_without_pop[opcode]) { | |||
| last->opcode=op_without_push[last->opcode]; | |||
| opcode=buffer[pc].opcode=op_without_pop[opcode]; | |||
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When we are here, we know thatop_without_pop[opcode] || op_without_pop_null[opcode] is true. But we should also make sure thatop_without_pop[opcode] itself is true, otherwise it is possible to accidentally write0 as the opcode.
I read the code but just checking that I understand it right: |
Yes, that's exactly the case! This allows us to optimize for instance: into just |
Fidget-Spinner approved these changesMay 23, 2025
71dea74 intopython:main 61 checks passed
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bedevere-bot commentedMay 23, 2025
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_CHECK_PERIODICto the list of skipped instructions. I believe this is safe to do since this instruction does not modify the stack. It is also relatively common so I think it's worth it to skip it.