1 files changed, 16 insertions, 2 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index aa31e0d850dd..83054588a9aa 100644
--- a/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -926,7 +926,13 @@ Instruction *InstCombiner::foldAddWithConstant(BinaryOperator &Add) {
   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)
@@ -1608,6 +1614,14 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
   if (match(Op0, m_Not(m_Value(X))) && match(Op1, m_Not(m_Value(Y))))
     return BinaryOperator::CreateSub(Y, X);
 
+  // (X + -1) - Y --> ~Y + X
+  if (match(Op0, m_OneUse(m_Add(m_Value(X), m_AllOnes()))))
+    return BinaryOperator::CreateAdd(Builder.CreateNot(Op1), X);
+
+  // Y - (X + 1) --> ~X + Y
+  if (match(Op1, m_OneUse(m_Add(m_Value(X), m_One()))))
+    return BinaryOperator::CreateAdd(Builder.CreateNot(X), Op0);
+
   if (Constant *C = dyn_cast<Constant>(Op0)) {
     bool IsNegate = match(C, m_ZeroInt());
     Value *X;
@@ -1858,7 +1872,7 @@ Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
   Constant *C;
   if (match(Op1, m_Constant(C)) && !isa<ConstantExpr>(Op1))
     return BinaryOperator::CreateFAddFMF(Op0, ConstantExpr::getFNeg(C), &I);
-  
+
   // X - (-Y) --> X + Y
   if (match(Op1, m_FNeg(m_Value(Y))))
     return BinaryOperator::CreateFAddFMF(Op0, Y, &I);