Fix misoptimizations when matching against strings/slices #22385
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This should probably have a // compile-flags: -O to force optimizations.
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Unfortunately this break when the tests are compiled with optimizations, because -O is given twice then. So I'll remove that again.
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Addressed both comments. Thanks! |
When matching against strings/slices, we call the comparison function for strings, which takes two string slices by value. The slices are passed in memory, and currently we just pass in a pointer to the original slice. That can cause misoptimizations because we emit a call to llvm.lifetime.end for all by-value arguments at the end of a function, which in this case marks the original slice as dead. So we need to properly create copies of the slices to pass them to the comparison function. Fixes rust-lang#22008
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Nice find for a subtle bug. |
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Hmm not sure why I put rollup there. I guess because the patch was so small. |
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…tsakis When matching against strings/slices, we call the comparison function for strings, which takes two string slices by value. The slices are passed in memory, and currently we just pass in a pointer to the original slice. That can cause misoptimizations because we emit a call to llvm.lifetime.end for all by-value arguments at the end of a function, which in this case marks the original slice as dead. So we need to properly create copies of the slices to pass them to the comparison function. Fixes rust-lang#22008
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When matching against strings/slices, we call the comparison function
for strings, which takes two string slices by value. The slices are
passed in memory, and currently we just pass in a pointer to the
original slice. That can cause misoptimizations because we emit a call
to llvm.lifetime.end for all by-value arguments at the end of a
function, which in this case marks the original slice as dead.
So we need to properly create copies of the slices to pass them to the
comparison function.
Fixes #22008