[PATCH] InstCombine ((A | ~B) ^ (~A | B)) to A ^ B

[David Majnemer]

Closed by commit rL215621 (authored by @majnemer).

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D4883

Files:
  llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  llvm/trunk/test/Transforms/InstCombine/or-xor.ll

Index: llvm/trunk/test/Transforms/InstCombine/or-xor.ll
===================================================================
--- llvm/trunk/test/Transforms/InstCombine/or-xor.ll
+++ llvm/trunk/test/Transforms/InstCombine/or-xor.ll
@@ -147,3 +147,16 @@
 ; CHECK-NEXT: %1 = and i32 %y, %x
 ; CHECK-NEXT: ret i32 %1
 }
+
+; ((x | ~y) ^ (~x | y)) -> x ^ y
+define i32 @test16(i32 %x, i32 %y) {
+  %noty = xor i32 %y, -1
+  %notx = xor i32 %x, -1
+  %or1 = or i32 %x, %noty
+  %or2 = or i32 %notx, %y
+  %xor = xor i32 %or1, %or2
+  ret i32 %xor
+; CHECK-LABEL: @test16(
+; CHECK-NEXT: %xor = xor i32 %x, %y
+; CHECK-NEXT: ret i32 %xor
+}
Index: llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2512,6 +2512,16 @@
       if ((A == C && B == D) || (A == D && B == C))
         return BinaryOperator::CreateXor(A, B);
     }
+    // (A | ~B) ^ (~A | B) -> A ^ B
+    if (match(Op0I, m_Or(m_Value(A), m_Not(m_Value(B)))) &&
+        match(Op1I, m_Or(m_Not(m_Specific(A)), m_Specific(B)))) {
+      return BinaryOperator::CreateXor(A, B);
+    }
+    // (~A | B) ^ (A | ~B) -> A ^ B
+    if (match(Op0I, m_Or(m_Not(m_Value(A)), m_Value(B))) &&
+        match(Op1I, m_Or(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)))) {
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