From fd12a0b20b12b0199011fb3903aa1f8ca4b387f5 Mon Sep 17 00:00:00 2001
From: Nick Lewycky <nicholas@mxc.ca>
Date: Sat, 31 May 2008 17:10:28 +0000
Subject: [PATCH] Adding i1 is always Xor.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51816 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/InstructionCombining.cpp    | 3 +++
 test/Transforms/InstCombine/2008-05-31-AddBool.ll | 7 +++++++
 2 files changed, 10 insertions(+)
 create mode 100644 test/Transforms/InstCombine/2008-05-31-AddBool.ll

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 74e6b6f6b06..5199578b1f8 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/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))
diff --git a/test/Transforms/InstCombine/2008-05-31-AddBool.ll b/test/Transforms/InstCombine/2008-05-31-AddBool.ll
new file mode 100644
index 00000000000..7008587c40d
--- /dev/null
+++ b/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
+}