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X86: optimization for max-like struct

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This patch will optimize the following cases on X86
(a > b) ? (a-b) : 0
(a >= b) ? (a-b) : 0
(b < a) ? (a-b) : 0
(b <= a) ? (a-b) : 0

FROM
movl    %edi, %ecx
subl    %esi, %ecx
cmpl    %edi, %esi
movl    $0, %eax
cmovll  %ecx, %eax
TO
xorl    %eax, %eax
subl    %esi, %edi
cmovll  %eax, %edi
movl    %edi, %eax

rdar: 10734411


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155919 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Manman Ren
2012-05-01 17:16:15 +00:00
parent d07d06ceef
commit 769ea2f93f
2 changed files with 82 additions and 0 deletions
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test/CodeGen/X86/jump_sign.ll
+42
View File
@@ -32,3 +32,45 @@ entry:
%cond = select i1 %cmp, i32 %sub, i32 0
ret i32 %cond
}
; rdar://10734411
define i32 @h(i32 %a, i32 %b) nounwind {
entry:
; CHECK: h:
; CHECK-NOT: cmp
; CHECK: cmov
%cmp = icmp slt i32 %b, %a
%sub = sub nsw i32 %a, %b
%cond = select i1 %cmp, i32 %sub, i32 0
ret i32 %cond
}
define i32 @i(i32 %a, i32 %b) nounwind {
entry:
; CHECK: i:
; CHECK-NOT: cmp
; CHECK: cmov
%cmp = icmp sgt i32 %a, %b
%sub = sub nsw i32 %a, %b
%cond = select i1 %cmp, i32 %sub, i32 0
ret i32 %cond
}
define i32 @j(i32 %a, i32 %b) nounwind {
entry:
; CHECK: j:
; CHECK-NOT: cmp
; CHECK: cmov
%cmp = icmp ugt i32 %a, %b
%sub = sub i32 %a, %b
%cond = select i1 %cmp, i32 %sub, i32 0
ret i32 %cond
}
define i32 @k(i32 %a, i32 %b) nounwind {
entry:
; CHECK: k:
; CHECK-NOT: cmp
; CHECK: cmov
%cmp = icmp ult i32 %b, %a
%sub = sub i32 %a, %b
%cond = select i1 %cmp, i32 %sub, i32 0
ret i32 %cond
}