[4.0] SILGen: Ease off +0 peepholes for load exprs. #11043
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Now that we more tightly close formal accesses on lvalues, having LoadExpr and friends try to return a +0 loaded value is unsafe without deeper analysis, since the access will be closed immediately after the load and potentially free temporary memory that might be the only thing keeping the borrowed object alive. Fixes rdar://problem/32730865. (cherry picked from commit 7705393)
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@swift-ci Please test |
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@swift-ci Please test source compatibility |
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@swift-ci Please benchmark |
jckarter
changed the title
Build comment file:Build failed before running benchmark. |
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Benchmark build failed because it looks like there isn't result history for the 4.0 branch. The PR for master at #11026 has results that are probably in line with what we'd see. |
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Explanation: Due to stricter handling of lvalues, peepholes that would attempt to load an rvalue without retaining would lead to use-after-free bugs.
Scope: Regression from 3.1
Issue: rdar://problem/32730865
Risk: Low, removal of a peephole optimization, small risk of performance regressions
Testing: Swift CI, project from radar