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[InstCombine] (~X) - (~Y) --> Y - X

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llvm-svn: 326660
This commit is contained in:
Sanjay Patel 2018-03-03 17:53:25 +00:00
parent 728449bd27
commit 9968c706bd
2 changed files with 7 additions and 4 deletions
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5
lib/Transforms/InstCombine/InstCombineAddSub.cpp
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@ -1511,6 +1511,11 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
if (match(Op0, m_AllOnes()))
return BinaryOperator::CreateNot(Op1);
// (~X) - (~Y) --> Y - X
Value *X, *Y;
if (match(Op0, m_Not(m_Value(X))) && match(Op1, m_Not(m_Value(Y))))
return BinaryOperator::CreateSub(Y, X);
if (Constant *C = dyn_cast<Constant>(Op0)) {
Value *X;
// C - zext(bool) -> bool ? C - 1 : C

6
test/Transforms/InstCombine/sub.ll
View File

@ -50,7 +50,7 @@ define i8 @notnotsub(i8 %x, i8 %y) {
; CHECK-LABEL: @notnotsub(
; CHECK-NEXT: [[NX:%.*]] = xor i8 [[X:%.*]], -1
; CHECK-NEXT: [[NY:%.*]] = xor i8 [[Y:%.*]], -1
; CHECK-NEXT: [[SUB:%.*]] = sub i8 [[NX]], [[NY]]
; CHECK-NEXT: [[SUB:%.*]] = sub i8 [[Y]], [[X]]
; CHECK-NEXT: call void @use8(i8 [[NX]])
; CHECK-NEXT: call void @use8(i8 [[NY]])
; CHECK-NEXT: ret i8 [[SUB]]
@ -65,9 +65,7 @@ define i8 @notnotsub(i8 %x, i8 %y) {
define <2 x i8> @notnotsub_vec(<2 x i8> %x, <2 x i8> %y) {
; CHECK-LABEL: @notnotsub_vec(
; CHECK-NEXT: [[NX:%.*]] = xor <2 x i8> [[X:%.*]], <i8 -1, i8 -1>
; CHECK-NEXT: [[NY:%.*]] = xor <2 x i8> [[Y:%.*]], <i8 -1, i8 -1>
; CHECK-NEXT: [[SUB:%.*]] = sub <2 x i8> [[NX]], [[NY]]
; CHECK-NEXT: [[SUB:%.*]] = sub <2 x i8> [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: ret <2 x i8> [[SUB]]
;
%nx = xor <2 x i8> %x, <i8 -1, i8 -1>