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

[suyog]

Hi dexonsmith, nicholas, silvas, rafael,

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

 Please help in reviewing the same.

Z3 link : http://rise4fun.com/Z3/4TE2

Thanks,
Suyog

http://reviews.llvm.org/D4628

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 +92,27 @@
 ; CHECK-NEXT: %z = or i32 %y.not, %x
 ; CHECK-NEXT: ret i32 %z
 }
+
+; (x | y) & ((~x) ^ y) -> (x & y)
+define i32 @test10(i32 %x, i32 %y) {
+  %or = or i32 %x, %y
+  %neg = xor i32 %x, -1
+  %xor = xor i32 %neg, %y
+  %and = and i32 %or, %xor
+  ret i32 %and
+; CHECK-LABEL: @test10(
+; CHECK-NEXT: %and = and i32 %x, %y
+; CHECK-NEXT: ret i32 %and
+}
+
+; ((~x) ^ y) & (x | y) -> (x & y)
+define i32 @test11(i32 %x, i32 %y) {
+  %neg = xor i32 %x, -1
+  %xor = xor i32 %neg, %y
+  %or = or i32 %x, %y
+  %and = and i32 %xor, %or
+  ret i32 %and
+; CHECK-LABEL: @test11(
+; CHECK-NEXT: %and = and i32 %x, %y
+; CHECK-NEXT: ret i32 %and
+}
Index: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1283,6 +1283,15 @@
     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) -> (A & B)
+    if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
+        match(Op1, m_Xor(m_Not(m_Specific(A)), m_Specific(B))))
+      return BinaryOperator::CreateAnd(A, B);
+    // ((~A) ^ B) & (A | B) -> (A & B)
+    if (match(Op0, m_Xor(m_Not(m_Value(A)), m_Value(B))) &&
+        match(Op1, m_Or(m_Specific(A), m_Specific(B))))
+      return BinaryOperator::CreateAnd(A, B);
   }
 
   if (ICmpInst *RHS = dyn_cast<ICmpInst>(Op1))
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