[PATCH] D115602: [X86] Memset is lowered to rep stos if MinSize is present

Thu Dec 16 00:16:40 PST 2021

pengfei added a comment.

In D115602#3195463 <https://reviews.llvm.org/D115602#3195463>, @spatel wrote:

> I don't remember seeing this part of x86 codegen before, so adding some more reviewers. I'm also not sure what is recommended as the best perf x86 asm on recent CPUs. Should we be using this for "optsize" too?

Neither do I. I saw Clang only has the builtin support `__builtin_memcpy_inline` by D73543 <https://reviews.llvm.org/D73543>. But GCC has the tuning code: https://github.com/gcc-mirror/gcc/commit/a32452a5442cd05040af53787af0d8b537ac77a6
Like the descriptions in GCC patch, this is not all win solution. But for minsize and optsize, this should be good to go. https://godbolt.org/z/4r8zTqfhY

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https://reviews.llvm.org/D115602