[SILOptimizer] Keep lexical lifetime markers. #39883
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This ensures that while in OSSA, we have in the IR information about the lexical lifetime of let variables.
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@swift-ci please test |
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LGTM! If SIL tests don't exist for these cases with lexical borrows, can you add them too ? |
Previously, TempRValueElimination would peephole simple alloc_stacks, even when they were lexical; here, they are left for Mem2Reg to properly handle. Previously, SemanticARCOpts would eliminate lexical begin_borrows, incorrectly allowing the lifetime of the value borrowed by them to be observably shortened. Here, those borrow scopes are not eliminated if they are lexical. Added an executable test that verifies that a local variable strongly referencing a delegate object keeps that delegate alive through the call to an object that weakly references the delegate and calls out to it.
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@swift-ci please test |
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Yup! |
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I am a little nervous about this. We should really run benchmarks with the flag enabled on this. |
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I talked with Nate. He is going to do some benchmarking with everything enabled to check for perf issues. That being said, he said he would also look into my suggestion in a week or so (which I am happy with) as follow up work. |
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@meg-gupta I will add the tests in a follow-up PR to unblock Michael. |
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Previously, TempRValueElimination would peephole simple alloc_stacks, even when they were lexical; here, they are left for Mem2Reg to properly handle.
Previously, SemanticARCOpts would eliminate lexical begin_borrows, incorrectly allowing the lifetime of the value borrowed by them to be observably shortened. Here, those borrow scopes are not eliminated if they are lexical.
Added an executable test that verifies that a local variable strongly referencing a delegate object keeps that delegate alive through the call to an object that weakly references the delegate and calls out to it.