[PATCH] Instcombine (A|B) ^(A^B) to A&B

[Karthik Bhat]

Hi David,
Thanks for the review. Yes the newer version is definetly more simple and correct place to do this transform.
Updated the patch as per review comments.

Thanks
Karthik Bhat

http://reviews.llvm.org/D4866

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

Index: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2508,6 +2508,18 @@
       if ((A == C && B == D) || (A == D && B == C))
         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 | B)^(A ^ B) -> A & B
+    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);
+    }
     // (A & B) ^ (A ^ B) -> (A | B)
     if (match(Op0I, m_And(m_Value(A), m_Value(B))) &&
         match(Op1I, m_Xor(m_Specific(A), m_Specific(B))))
Index: test/Transforms/InstCombine/or-xor.ll
===================================================================
--- test/Transforms/InstCombine/or-xor.ll
+++ test/Transforms/InstCombine/or-xor.ll
@@ -136,3 +136,13 @@
 ; CHECK-NEXT: %and = and i32 %x, %y
 ; CHECK-NEXT: ret i32 %and
 }
+
+define i32 @test15(i32 %x, i32 %y) {
+  %1 = xor i32 %y, %x
+  %2 = or i32 %y, %x
+  %3 = xor i32 %2, %1
+  ret i32 %3
+; CHECK-LABEL: @test15(
+; CHECK-NEXT: %1 = and i32 %y, %x
+; CHECK-NEXT: ret i32 %1
+}
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