[PATCH] Added InstCombine transform for pattern "(A ^ B) & ((~A) ^ B) -> False"

[sonam kumari]

Hi dexonsmith, rafael, nicholas, silvas,

This patch implements transform for pattern "(A ^ B) & ((~A) ^ B) -> False".

Please help in reviewing the same.

Thanks,
Sonam.

http://reviews.llvm.org/D4690

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

Index: test/Transforms/InstCombine/or-xor.ll
===================================================================
--- test/Transforms/InstCombine/or-xor.ll
+++ test/Transforms/InstCombine/or-xor.ll
@@ -92,3 +92,13 @@
 ; CHECK-NEXT: %z = or i32 %y.not, %x
 ; CHECK-NEXT: ret i32 %z
 }
+
+define i32 @test10(i32%x,i32%y){
+;CHECK-LABEL: @test10(
+;CHECK-NEXT: ret i32 0
+%xor = xor i32%x,%y
+%nega = xor i32%x,-1
+%xor1 = xor i32%nega,%y
+%and = and i32%xor,%xor1
+ret i32 %and
+}
Index: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1280,6 +1280,11 @@
     if (match(Op1, m_Or(m_Not(m_Specific(Op0)), m_Value(A))) ||
         match(Op1, m_Or(m_Value(A), m_Not(m_Specific(Op0)))))
       return BinaryOperator::CreateAnd(A, Op0);
+
+// (A^B) & ((~(A)^B) -> 0
+  if(match(Op0,m_Xor(m_Value(A),m_Value(B)))
+          && match(Op1,m_Xor(m_Not(m_Specific(A)),m_Specific(B))))
+      return BinaryOperator::CreateAnd(A, Builder->CreateNot(A));
   }
 
   if (ICmpInst *RHS = dyn_cast<ICmpInst>(Op1))
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