1 files changed, 18 insertions, 9 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 287a5167fe2ae..d5f0dd1914157 100644
--- a/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -988,15 +988,24 @@ static Instruction *foldAddWithConstant(BinaryOperator &Add,
     return new ZExtInst(Builder.CreateNUWAdd(X, NewC), Ty);
   }
 
-  // Shifts and add used to flip and mask off the low bit:
-  // add (ashr (shl i32 X, 31), 31), 1 --> and (not X), 1
-  const APInt *C3;
-  if (C->isOneValue() &&
-      match(Op0,
-            m_OneUse(m_AShr(m_Shl(m_Value(X), m_APInt(C2)), m_APInt(C3)))) &&
-      C2 == C3 && *C2 == Ty->getScalarSizeInBits() - 1) {
-    Value *NotX = Builder.CreateNot(X);
-    return BinaryOperator::CreateAnd(NotX, ConstantInt::get(Ty, 1));
+  if (C->isOneValue() && Op0->hasOneUse()) {
+    // add (sext i1 X), 1 --> zext (not X)
+    // TODO: The smallest IR representation is (select X, 0, 1), and that would
+    // not require the one-use check. But we need to remove a transform in
+    // visitSelect and make sure that IR value tracking for select is equal or
+    // better than for these ops.
+    if (match(Op0, m_SExt(m_Value(X))) &&
+        X->getType()->getScalarSizeInBits() == 1)
+      return new ZExtInst(Builder.CreateNot(X), Ty);
+
+    // Shifts and add used to flip and mask off the low bit:
+    // add (ashr (shl i32 X, 31), 31), 1 --> and (not X), 1
+    const APInt *C3;
+    if (match(Op0, m_AShr(m_Shl(m_Value(X), m_APInt(C2)), m_APInt(C3))) &&
+        C2 == C3 && *C2 == Ty->getScalarSizeInBits() - 1) {
+      Value *NotX = Builder.CreateNot(X);
+      return BinaryOperator::CreateAnd(NotX, ConstantInt::get(Ty, 1));
+    }
   }
 
   return nullptr;