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

…(A & B)".

Differential Revision: http://reviews.llvm.org/D4628

llvm-svn: 214478

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -1295,6 +1295,16 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
       if (match(Op1, m_Xor(m_Specific(B), m_Specific(A))))
         if (Op0->hasOneUse() || cast<BinaryOperator>(Op0)->hasOneUse())
           return BinaryOperator::CreateAnd(Op1, Builder->CreateNot(C));
+
+    // (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))

llvm/test/Transforms/InstCombine/or-xor.ll

@@ -112,3 +112,27 @@ define i32 @test11(i32 %A, i32 %B) {
 ; CHECK-LABEL: @test11(
 ; CHECK-NEXT: ret i32 -1
 }
+
+; (x | y) & ((~x) ^ y) -> (x & y)
+define i32 @test12(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: @test12(
+; CHECK-NEXT: %and = and i32 %x, %y
+; CHECK-NEXT: ret i32 %and
+}
+
+; ((~x) ^ y) & (x | y) -> (x & y)
+define i32 @test13(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: @test13(
+; CHECK-NEXT: %and = and i32 %x, %y
+; CHECK-NEXT: ret i32 %and
+}