[DNM: Draft][SILOpt] TempRValueElimination: 'let' copy source values cant be over… #61502
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…writen by apply instructions TempRValueElimination checks if a copy of a value can be eliminated. Checking that the original source value was not modified during the copy is one of the requirements for the elimination. Prior to this change, TempRValueElimination checked if apply instructions could've potentially modified the original source value, even if the source value was an immutable 'let'. This prevented some optimization opportunities. With this change, we can recognize that 'let' source value won't be modified by an apply, so that we can proceed with copy elimination.
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still needs tests |
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@swift-ci please benchmark |
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@swift-ci please test |
atrick
reviewed
Oct 8, 2022
| if ((FullApplySite::isa(inst) || isa<YieldInst>(inst)) && | ||
| aa->mayWriteToMemory(inst, copySrc)) { | ||
| !isLetObject(copySrc) && aa->mayWriteToMemory(inst, copySrc)) { |
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Now, you can just use bool swift::isLetAddress(SILValue address). That uses the canonical AccessBase utility. It's a bit less ad-hoc and you don't need to DIY.
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@meg-gupta pointed out that if you just check AllocStack::isLet() inside isLetAddress, then you shouldn't need to touch this pass at all.
atrick
reviewed
Oct 8, 2022
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Closing in favor of #61504 |
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I think @meg-gupta will introduce a PR very similar to this, maybe with a comment that we can't safely rely on |
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…writen by apply instructions
TempRValueElimination checks if a copy of a value can be eliminated. Checking that the original source value was not modified during the copy is one of the requirements for the elimination. Prior to this change, TempRValueElimination checked if apply instructions could've potentially modified the original source value, even if the source value was an immutable 'let'. This prevented some optimization opportunities. With this change, we can recognize that 'let' source value won't be modified by an apply, so that we can proceed with copy elimination.