[llvm-dev] report a clang bug: SSE4.1 instruction problem

[wade via llvm-dev]

Hi,
  I was build SSE performance work on mac intel. But I found the performance of my SSE4.1 version code using in xcode 12.4 is not as good as xcode 10.1, so I checked the assembly of my code. The one _mm_mul_epi() instruction was translated into three pmuludq, which is the SSE2 instruction, while this was normal when compiling on xcode 10.1 and _mm_mul_epi() was translated into pmuldq. So I checked the clang version, and I found this error occured when clang version larger than 7.0.0.
  The simple case can be found: https://godbolt.org/z/Tf7qeocvz
  I probably think this is a clang compiler bug. And I hope to get some advice on how to solve this issue.
  Thanks.
Best,
  Wade















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