From 6fe6ea740cf6b7b1139ee8825571e8194aa4cc89 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Fri, 5 Sep 2014 06:09:24 +0000
Subject: [PATCH] InstCombine: Remove a special case pattern

The special case did not work when run under -reassociate and can easily
be expressed by a further generalization of an existing pattern.

llvm-svn: 217227
---
 .../InstCombine/InstCombineAndOrXor.cpp       | 31 ++++++++++---------
 llvm/test/Transforms/InstCombine/xor2.ll      | 27 ++++++++++++----
 2 files changed, 38 insertions(+), 20 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index b19e8b4d72de..ed6253532e09 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2614,17 +2614,25 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
         match(Op1I, m_And(m_Specific(A), m_Not(m_Specific(B))))) {
       return BinaryOperator::CreateXor(A, B);
     }
-    // (A ^ B)^(A | B) -> A & B
-    if (match(Op0I, m_Xor(m_Value(A), m_Value(B))) &&
-        match(Op1I, m_Or(m_Value(C), m_Value(D)))) {
-      if ((A == C && B == D) || (A == D && B == C))
-        return BinaryOperator::CreateAnd(A, B);
+    // (A ^ C)^(A | B) -> ((~A) & B) ^ C
+    if (match(Op0I, m_Xor(m_Value(D), m_Value(C))) &&
+        match(Op1I, m_Or(m_Value(A), m_Value(B)))) {
+      if (D == A)
+        return BinaryOperator::CreateXor(
+            Builder->CreateAnd(Builder->CreateNot(A), B), C);
+      if (D == B)
+        return BinaryOperator::CreateXor(
+            Builder->CreateAnd(Builder->CreateNot(B), A), C);
     }
-    // (A | B)^(A ^ B) -> A & B
+    // (A | B)^(A ^ C) -> ((~A) & B) ^ C
     if (match(Op0I, m_Or(m_Value(A), m_Value(B))) &&
-        match(Op1I, m_Xor(m_Value(C), m_Value(D)))) {
-      if ((A == C && B == D) || (A == D && B == C))
-        return BinaryOperator::CreateAnd(A, B);
+        match(Op1I, m_Xor(m_Value(D), m_Value(C)))) {
+      if (D == A)
+        return BinaryOperator::CreateXor(
+            Builder->CreateAnd(Builder->CreateNot(A), B), C);
+      if (D == B)
+        return BinaryOperator::CreateXor(
+            Builder->CreateAnd(Builder->CreateNot(B), A), C);
     }
     // (A & B) ^ (A ^ B) -> (A | B)
     if (match(Op0I, m_And(m_Value(A), m_Value(B))) &&
@@ -2636,12 +2644,7 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
       return BinaryOperator::CreateOr(A, B);
   }
 
-  // (A | B)^(~A) -> (A | ~B)
   Value *A = nullptr, *B = nullptr;
-  if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
-      match(Op1, m_Not(m_Specific(A))))
-    return BinaryOperator::CreateOr(A, Builder->CreateNot(B));
-
   // (A & ~B) ^ (~A) -> ~(A & B)
   if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
       match(Op1, m_Not(m_Specific(A))))
diff --git a/llvm/test/Transforms/InstCombine/xor2.ll b/llvm/test/Transforms/InstCombine/xor2.ll
index 2f78b294a75a..a449e12c5b0e 100644
--- a/llvm/test/Transforms/InstCombine/xor2.ll
+++ b/llvm/test/Transforms/InstCombine/xor2.ll
@@ -85,25 +85,27 @@ define i32 @test6(i32 %x) {
 
 
 ; (A | B) ^ (~A) -> (A | ~B)
-define i32 @test7(i32 %a, i32 %b) #0 {
+define i32 @test7(i32 %a, i32 %b) {
  %or = or i32 %a, %b
  %neg = xor i32 %a, -1
  %xor = xor i32 %or, %neg
  ret i32 %xor
 ; CHECK-LABEL: @test7(
-; CHECK-NEXT: %1 = xor i32 %b, -1
-; CHECK-NEXT: %xor = or i32 %a, %1
+; CHECK-NEXT: %[[b_not:.*]] = xor i32 %b, -1
+; CHECK-NEXT: %[[or:.*]] = or i32 %a, %[[b_not]]
+; CHECK-NEXT: ret i32 %[[or]]
 }
 
 ; (~A) ^ (A | B) -> (A | ~B)
-define i32 @test8(i32 %a, i32 %b) #0 {
+define i32 @test8(i32 %a, i32 %b) {
  %neg = xor i32 %a, -1
  %or = or i32 %a, %b
  %xor = xor i32 %neg, %or
  ret i32 %xor
 ; CHECK-LABEL: @test8(
-; CHECK-NEXT: %1 = xor i32 %b, -1
-; CHECK-NEXT: %xor = or i32 %a, %1
+; CHECK-NEXT: %[[b_not:.*]] = xor i32 %b, -1
+; CHECK-NEXT: %[[or:.*]] = or i32 %a, %[[b_not]]
+; CHECK-NEXT: ret i32 %[[or]]
 }
 
 ; (A & B) ^ (A ^ B) -> (A | B)
@@ -167,3 +169,16 @@ define i32 @test14(i32 %a, i32 %b) {
 ; CHECK-NEXT: %1 = and i32 %a, %b
 ; CHECK-NEXT: %xor = xor i32 %1, -1
 }
+
+; (A ^ C) ^ (A | B) -> ((~A) & B) ^ C
+define i32 @test15(i32 %a, i32 %b, i32 %c) {
+ %neg = xor i32 %a, %c
+ %or = or i32 %a, %b
+ %xor = xor i32 %neg, %or
+ ret i32 %xor
+; CHECK-LABEL: @test15(
+; CHECK-NEXT: %[[not:.*]] = xor i32 %a, -1
+; CHECK-NEXT: %[[and:.*]] = and i32 %[[not]], %b
+; CHECK-NEXT: %[[xor:.*]] = xor i32 %[[and]], %c
+; CHECK-NEXT: ret i32 %[[xor]]
+}