Avoid calling memcpy in swap
#5500
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StephanTLavavej
approved these changes
May 15, 2025
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I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed. |
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Fixes #5481
The release codegen is the same, the benchmark results are the same.
memcpycalls are now not emitted in any mode. In/Odwe haverep movsb, which is pretty good for a debug mode.unsigned charis kept for underlying type as it doesn't have alignment requirements, and also is a valid alias for any object.@frederick-vs-ja pointed out that the strict aliasing rule is still violated here.
I excluded Clang (and thus Intel), I verified Clang already optimizes the usual swap loop on its own.MSVC doesn't take advantage of strict aliasing, so it is fine 🔥🐶☕🔥