From e06535b2f63f2c2fcc3082a9d5d29cce7415fd21 Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Fri, 16 Mar 2012 00:52:42 +0000
Subject: [PATCH] In InstCombiner::visitOr, make sure we reverse the operand
 swap used for checking for or-of-xor operations after those checks; a later
 check expects that any constant will be in Op1.  PR12234.

llvm-svn: 152884
---
 .../Transforms/InstCombine/InstCombineAndOrXor.cpp   |  8 +++++++-
 .../InstCombine/2012-3-15-or-xor-constant.ll         | 12 ++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/Transforms/InstCombine/2012-3-15-or-xor-constant.ll

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index cc8f5bf43e55..1165660f40f2 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1929,8 +1929,11 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
       }
 
   // Canonicalize xor to the RHS.
-  if (match(Op0, m_Xor(m_Value(), m_Value())))
+  bool SwappedForXor = false;
+  if (match(Op0, m_Xor(m_Value(), m_Value()))) {
     std::swap(Op0, Op1);
+    SwappedForXor = true;
+  }
 
   // A | ( A ^ B) -> A |  B
   // A | (~A ^ B) -> A | ~B
@@ -1961,6 +1964,9 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
         return BinaryOperator::CreateOr(Not, Op0);
       }
 
+  if (SwappedForXor)
+    std::swap(Op0, Op1);
+
   if (ICmpInst *RHS = dyn_cast<ICmpInst>(I.getOperand(1)))
     if (ICmpInst *LHS = dyn_cast<ICmpInst>(I.getOperand(0)))
       if (Value *Res = FoldOrOfICmps(LHS, RHS))
diff --git a/llvm/test/Transforms/InstCombine/2012-3-15-or-xor-constant.ll b/llvm/test/Transforms/InstCombine/2012-3-15-or-xor-constant.ll
new file mode 100644
index 000000000000..c1602da4c84d
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/2012-3-15-or-xor-constant.ll
@@ -0,0 +1,12 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+; PR12234
+
+@g = extern_weak global i32
+define i32 @function(i32 %x) nounwind {
+entry:
+  %xor = xor i32 %x, 1
+  store volatile i32 %xor, i32* inttoptr (i64 1 to i32*), align 4
+  %or4 = or i32 or (i32 zext (i1 icmp eq (i32* @g, i32* null) to i32), i32 1), %xor
+  ret i32 %or4
+}
+; CHECK: define i32 @function
-- 
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