[PATCH] D48768: [X86] When have BMI2, prefer shifts to clear low/high bits, rather than variable mask.

Roman Lebedev via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Fri Jun 29 06:55:05 PDT 2018


lebedev.ri added a comment.

This is always good re instruction count.
This is good for Ryzen: https://godbolt.org/g/bd6xLh
But e.g. for Haswell, `IPC` halves, and `RThroughput` slightly decreases: https://godbolt.org/g/2gUzfP
So i'm not sure, maybe some more guards are needed?


Repository:
  rL LLVM

https://reviews.llvm.org/D48768





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