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Benjamin Kramer
444dccecfc
X86: Promote i8 cmov when both operands are coming from truncates of the same width.
X86 doesn't have i8 cmovs so isel would emit a branch. Emitting branches at this level is often not a good idea because it's too late for many optimizations to kick in. This solution doesn't add any extensions (truncs are free) and tries to avoid introducing partial register stalls by filtering direct copyfromregs. I'm seeing a ~10% speedup on reading a random .png file with libpng15 via graphicsmagick on x86_64/westmere, but YMMV depending on the microarchitecture. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165868 91177308-0d34-0410-b5e6-96231b3b80d8
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