Added InstCombine Transform for pattern "(A | B)^(~A) = (~A)^(A | B) -> (A | ~B)"

[suyog]

Summary

This patch implements transformation for pattern

(A | B)^(~A) = (~A)^(A | B) -> (A | ~B)

Please help in reviewing the same.

Thanks,
Suyog

lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

if (Op0I && Op1I) {
     // (A | B)^(A & B) -> A ^ B
     if (match(Op0I, m_Or(m_Value(A), m_Value(B))) &&
         match(Op1I, m_And(m_Value(C), m_Value(D)))) {
       if ((A == C && B == D) || (A == D && B == C))
         return BinaryOperator::CreateXor(A, B);
     }
   }
 
+  // (A | B)^(~A) = (~A)^(A | B) -> (A | ~B)
+  Value *A = nullptr, *B = nullptr;
+  if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
+      match(Op1, m_Not(m_Specific(A))))
+    return BinaryOperator::CreateOr(A, Builder->CreateNot(B));
+
   // (icmp1 A, B) ^ (icmp2 A, B) --> (icmp3 A, B)
   if (ICmpInst *RHS = dyn_cast<ICmpInst>(I.getOperand(1)))
     if (ICmpInst *LHS = dyn_cast<ICmpInst>(I.getOperand(0)))
       if (PredicatesFoldable(LHS->getPredicate(), RHS->getPredicate())) {
         if (LHS->getOperand(0) == RHS->getOperand(1) &&
             LHS->getOperand(1) == RHS->getOperand(0))
           LHS->swapOperands();
         if (LHS->getOperand(0) == RHS->getOperand(0) &&

test/Transforms/InstCombine/xor2.ll

define i32 @test6(i32 %x) {
   %xor = xor i32 %x, 1234
   %shr = lshr i32 %xor, 16
   %add = add i32 %shr, %xor
   ret i32 %add
 ; CHECK-LABEL: @test6(
 ; CHECK: lshr i32 %x, 16
 ; CHECK: ret
 }
+
+; (A | B) ^ (~A) -> (A | ~B)
+define i32 @test7(i32 %a, i32 %b) #0 {
+  %or = or i32 %a, %b
+  %neg = xor i32 %a, -1
+  %xor = xor i32 %or, %neg
+  ret i32 %xor
+; CHECK-LABEL: @test7(
+; CHECK-NEXT: %1 = xor i32 %b, -1
+; CHECK-NEXT: %xor = or i32 %a, %1
+}
+
+; (~A) ^ (A | B) -> (A | ~B)
+define i32 @test8(i32 %a, i32 %b) #0 {
+  %neg = xor i32 %a, -1
+  %or = or i32 %a, %b
+  %xor = xor i32 %neg, %or
+  ret i32 %xor
+; CHECK-LABEL: @test8(
+; CHECK-NEXT: %1 = xor i32 %b, -1
+; CHECK-NEXT: %xor = or i32 %a, %1
+}