From 5a443ac000c667302135f0c4735cb3c98bac1763 Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Mon, 19 Dec 2016 18:35:37 +0000
Subject: [PATCH] [InstCombine] use commutative matcher for pattern with
 commutative operators

This is a case that was missed in:
https://reviews.llvm.org/rL290067
...and it would regress if we fix operand complexity (PR28296).

llvm-svn: 290127
---
 llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp |  8 +++++---
 llvm/test/Transforms/InstCombine/or.ll                  | 17 ++++++++++++++++-
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 2ab76d6..52b611f 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2263,9 +2263,11 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
       match(Op1, m_Xor(m_Specific(A), m_Specific(B))))
     return BinaryOperator::CreateXor(A, B);
 
-  // (A ^ B) | ( A & (~B)) -> (A ^ B)
-  if (match(Op0, m_Xor(m_Value(A), m_Value(B))) &&
-      match(Op1, m_And(m_Specific(A), m_Not(m_Specific(B)))))
+  // Commute the 'or' operands.
+  // (A ^ B) | (A & ~B) -> (A ^ B)
+  // (A ^ B) | (~B & A) -> (A ^ B)
+  if (match(Op1, m_c_And(m_Value(A), m_Not(m_Value(B)))) &&
+      match(Op0, m_Xor(m_Specific(A), m_Specific(B))))
     return BinaryOperator::CreateXor(A, B);
 
   // (A & C)|(B & D)
diff --git a/llvm/test/Transforms/InstCombine/or.ll b/llvm/test/Transforms/InstCombine/or.ll
index facd630..2c90884 100644
--- a/llvm/test/Transforms/InstCombine/or.ll
+++ b/llvm/test/Transforms/InstCombine/or.ll
@@ -596,7 +596,7 @@ define i32 @test42_commuted_xor(i32 %a, i32 %b) {
   ret i32 %or
 }
 
-; Commute operands of the 'or'.
+; (A & ~B) | (A ^ B) -> A ^ B
 
 define i32 @test43(i32 %a, i32 %b) {
 ; CHECK-LABEL: @test43(
@@ -622,6 +622,9 @@ define i32 @test43_commuted_and(i32 %a, i32 %b) {
   ret i32 %or
 }
 
+; Commute operands of the 'or'.
+; (A ^ B) | (A & ~B) -> A ^ B
+
 define i32 @test44(i32 %a, i32 %b) {
 ; CHECK-LABEL: @test44(
 ; CHECK-NEXT:    [[OR:%.*]] = xor i32 %a, %b
@@ -634,6 +637,18 @@ define i32 @test44(i32 %a, i32 %b) {
   ret i32 %or
 }
 
+define i32 @test44_commuted_and(i32 %a, i32 %b) {
+; CHECK-LABEL: @test44_commuted_and(
+; CHECK-NEXT:    [[OR:%.*]] = xor i32 %a, %b
+; CHECK-NEXT:    ret i32 [[OR]]
+;
+  %xor = xor i32 %a, %b
+  %neg = xor i32 %b, -1
+  %and = and i32 %neg, %a
+  %or = or i32 %xor, %and
+  ret i32 %or
+}
+
 define i32 @test45(i32 %x, i32 %y, i32 %z) {
 ; CHECK-LABEL: @test45(
 ; CHECK-NEXT:    [[TMP1:%.*]] = and i32 %x, %z
-- 
2.7.4