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f51a6d5fae
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
llvm-svn: 158175
21 lines
484 B
LLVM
21 lines
484 B
LLVM
; RUN: llc < %s -march=x86-64 | FileCheck %s
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;; Integer absolute value, should produce something at least as good as:
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;; movl %edi, %eax
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;; negl %eax
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;; cmovll %edi, %eax
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;; ret
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; rdar://10695237
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define i32 @test(i32 %a) nounwind {
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; CHECK: test:
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; CHECK: mov
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; CHECK-NEXT: neg
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; CHECK-NEXT: cmov
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; CHECK-NEXT: ret
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%tmp1neg = sub i32 0, %a
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%b = icmp sgt i32 %a, -1
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%abs = select i1 %b, i32 %a, i32 %tmp1neg
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ret i32 %abs
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}
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