[PATCH] D28354: [X86][MCU] replace select with bit manipulation instead of branches

[Asaf Badouh via Phabricator via llvm-commits]

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In case of the following select pattern, where :

1. the condition is a result of "x & 0x1"
2. the select operand are (z ^ y) , y or (z | y) , y

we can eliminate the branch (there is no "cmov" in MCU)  by generate bitwise sequence.

  select (and (x & 0x1) == 0), (z ^ y) , y )

to:

  (-(and (x & 0x1)) & z ) ^ y


Repository:
  rL LLVM

https://reviews.llvm.org/D28354

Files:
  ../tunkClang/lib/Target/X86/X86ISelLowering.cpp
  ../tunkClang/test/CodeGen/X86/select.ll

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