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

[suyog]

Hi dexonsmith, nicholas, rafael,

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

Please help in reviewing the same.

Thanks,
Suyog

http://reviews.llvm.org/D4618

Files:
  lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  test/Transforms/InstCombine/xor2.ll

Index: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2444,6 +2444,14 @@
       if ((A == C && B == D) || (A == D && B == C))
         return BinaryOperator::CreateXor(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))))
+      return BinaryOperator::CreateOr(A, B);
+    // (A ^ B) ^ (A & B) -> (A | B)
+    if (match(Op0I, m_Xor(m_Value(A), m_Value(B))) &&
+        match(Op1I, m_And(m_Specific(A), m_Specific(B))))
+      return BinaryOperator::CreateOr(A, B);
   }
 
   // (icmp1 A, B) ^ (icmp2 A, B) --> (icmp3 A, B)
Index: test/Transforms/InstCombine/xor2.ll
===================================================================
--- test/Transforms/InstCombine/xor2.ll
+++ test/Transforms/InstCombine/xor2.ll
@@ -82,3 +82,23 @@
 ; CHECK: lshr i32 %x, 16
 ; CHECK: ret
 }
+
+; (A & B) ^ (A ^ B) -> (A | B)
+define i32 @test9(i32 %b, i32 %c) {
+  %and = and i32 %b, %c
+  %xor = xor i32 %b, %c
+  %xor2 = xor i32 %and, %xor
+  ret i32 %xor2
+; CHECK-LABEL: @test9(
+; CHECK-NEXT: %xor2 = or i32 %b, %c
+}
+
+; (A ^ B) ^ (A & B) -> (A | B)
+define i32 @test10(i32 %b, i32 %c) {
+  %xor = xor i32 %b, %c
+  %and = and i32 %b, %c
+  %xor2 = xor i32 %xor, %and
+  ret i32 %xor2
+; CHECK-LABEL: @test10(
+; CHECK-NEXT: %xor2 = or i32 %b, %c
+}
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