[llvm] [InstCombine] Fold (X + C) + (Y & ~C) to X + (Y | C) (PR #191334)

[via llvm-commits]

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@@ -1523,6 +1523,47 @@ static Instruction *foldBoxMultiply(BinaryOperator &I) {
   return nullptr;
 }
 
+static Instruction *
+foldAddWithMaskedOverwrite(BinaryOperator &Add,
+                           InstCombiner::BuilderTy &Builder) {
+  Value *LHS = Add.getOperand(0), *RHS = Add.getOperand(1);
+  Value *X, *Y;
+  const APInt *C;
+
+  auto Match = [&](Value *AddOp, Value *AndOp) -> Instruction * {
+    if (!match(AddOp, m_c_Add(m_Value(X), m_APInt(C))) ||
+        !match(AndOp, m_c_And(m_Value(Y), m_SpecificInt(~*C))))
+      return nullptr;
+
+    // Replacing one add with {or, add}. Avoid growth if both sides are shared.
+    if (!AddOp->hasOneUse() && !AndOp->hasOneUse())
+      return nullptr;
+
+    bool PreserveNSW = false;
+    bool PreserveNUW = false;
+    if (auto *InnerAdd = dyn_cast<OverflowingBinaryOperator>(AddOp)) {
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ParkHanbum wrote:

Changed according to other code logic inside the foldAddLikeCommutative.

https://github.com/llvm/llvm-project/pull/191334