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a2b5600e61
1. generalize
(select (x == 0), -1, 0) -> (sign_bit (x - 1))
to:
(select (x == 0), -1, y) -> (sign_bit (x - 1)) | y
2. Handle the identical pattern that happens with !=:
(select (x != 0), y, -1) -> (sign_bit (x - 1)) | y
cmov is often high latency and can't fold immediates or
memory operands. For example for (x == 0) ? -1 : 1, before
we got:
< testb %sil, %sil
< movl $-1, %ecx
< movl $1, %eax
< cmovel %ecx, %eax
now we get:
> cmpb $1, %sil
> sbbl %eax, %eax
> orl $1, %eax
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120929 91177308-0d34-0410-b5e6-96231b3b80d8
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