X86: optimize generated code for integer ABS
This patch will generate the following for integer ABS:
movl %edi, %eax
negl %eax
cmovll %edi, %eax
INSTEAD OF
movl %edi, %ecx
sarl $31, %ecx
leal (%rdi,%rcx), %eax
xorl %ecx, %eax
There exists a target-independent DAG combine for integer ABS, which converts
integer ABS to sar+add+xor. For X86, we match this pattern back to neg+cmov.
This is implemented in PerformXorCombine.
rdar://
10695237
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158175
91177308-0d34-0410-b5e6-
96231b3b80d8