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

[David Majnemer]

================
Comment at: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp:2511-2538
@@ -2510,2 +2510,30 @@
     }
+    // (A | ~B) ^ (~A | B) -> A ^ B
+    // (A | ~B) ^ (B | ~A) -> 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))) ||
+         match(Op1I, m_Or(m_Specific(B), m_Not(m_Specific(A)))))) {
+      return BinaryOperator::CreateXor(A, B);
+    }
+    // (~B | A) ^ (~A | B) -> A ^ B
+    // (~B | A) ^ (B | ~A) -> A ^ B
+    if (match(Op0I, m_Or(m_Not(m_Value(B)), m_Value(A))) &&
+        (match(Op1I, m_Or(m_Not(m_Specific(A)), m_Specific(B))) ||
+         match(Op1I, m_Or(m_Specific(B), m_Not(m_Specific(A)))))) {
+      return BinaryOperator::CreateXor(A, B);
+    }
+    // (~A | B) ^ (A | ~B) -> A ^ B
+    // (~A | B) ^ (~B | A) -> 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)))) ||
+         match(Op1I, m_Or(m_Not(m_Specific(B)), m_Specific(A))))) {
+      return BinaryOperator::CreateXor(A, B);
+    }
+    // (B | ~A) ^ (A | ~B) -> A ^ B
+    // (B | ~A) ^ (~B | A) -> A ^ B
+    if (match(Op0I, m_Or(m_Value(B), m_Not(m_Value(A)))) &&
+        (match(Op1I, m_Or(m_Specific(A), m_Not(m_Specific(B)))) ||
+         match(Op1I, m_Or(m_Not(m_Specific(B)), m_Specific(A))))) {
+      return BinaryOperator::CreateXor(A, B);
+    }
     // (A ^ B)^(A | B) -> A & B
----------------
You have what appear to be eight different patterns you are trying to match.  Are you sure we need all of them? What happens if you ran a reassociate pass first?

http://reviews.llvm.org/D4883