Adding i1 is always Xor.

llvm-svn: 51816

lib/Transforms/Scalar/InstructionCombining.cpp

@@ -2551,6 +2551,9 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
   bool Changed = SimplifyCommutative(I);
   Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
 
+  if (I.getType() == Type::Int1Ty)
+    return BinaryOperator::CreateXor(LHS, RHS);
+
   if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
     // X + undef -> undef
     if (isa<UndefValue>(RHS))

test/Transforms/InstCombine/2008-05-31-AddBool.ll

@@ -0,0 +1,7 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {xor}
+; PR2389
+
+define i1 @test(i1 %a, i1 %b) {
+  %A = add i1 %a, %b
+  ret i1 %A
+}