if (Instruction *NV = foldBinOpIntoSelectOrPhi(Add))
return NV;
- Value *X;
+ Value *X, *Y;
+
+ // add (sub X, Y), -1 --> add (not Y), X
+ if (match(Op0, m_OneUse(m_Sub(m_Value(X), m_Value(Y)))) &&
+ match(Op1, m_AllOnes()))
+ return BinaryOperator::CreateAdd(Builder.CreateNot(Y), X);
+
// zext(bool) + C -> bool ? C + 1 : C
if (match(Op0, m_ZExt(m_Value(X))) &&
X->getType()->getScalarSizeInBits() == 1)
define i8 @dec_sub(i8 %x, i8 %y) {
; CHECK-LABEL: @dec_sub(
-; CHECK-NEXT: [[S:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT: [[R:%.*]] = add i8 [[S]], -1
+; CHECK-NEXT: [[TMP1:%.*]] = xor i8 [[Y:%.*]], -1
+; CHECK-NEXT: [[R:%.*]] = add i8 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i8 [[R]]
;
%s = sub i8 %x, %y
define <2 x i8> @dec_sub_vec(<2 x i8> %x, <2 x i8> %y) {
; CHECK-LABEL: @dec_sub_vec(
-; CHECK-NEXT: [[S:%.*]] = sub <2 x i8> [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT: [[R:%.*]] = add <2 x i8> [[S]], <i8 -1, i8 undef>
+; CHECK-NEXT: [[TMP1:%.*]] = xor <2 x i8> [[Y:%.*]], <i8 -1, i8 -1>
+; CHECK-NEXT: [[R:%.*]] = add <2 x i8> [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret <2 x i8> [[R]]
;
%s = sub <2 x i8> %x, %y