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

Patch idea by Ankit Jain !

Differential Revision: http://reviews.llvm.org/D4618

llvm-svn: 213677

2 files changed, 28 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index ef6a848357e..718cf29f184 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2454,6 +2454,14 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
       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);
   }
 
   // (A | B)^(~A) -> (A | ~B)
diff --git a/llvm/test/Transforms/InstCombine/xor2.ll b/llvm/test/Transforms/InstCombine/xor2.ll
index e7b1b1bbda8..4ae50a140e1 100644
--- a/llvm/test/Transforms/InstCombine/xor2.ll
+++ b/llvm/test/Transforms/InstCombine/xor2.ll
@@ -105,3 +105,23 @@ define i32 @test8(i32 %a, i32 %b) #0 {
 ; CHECK-NEXT: %1 = xor i32 %b, -1
 ; CHECK-NEXT: %xor = or i32 %a, %1
 }
+
+; (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
+}