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

[suyog]

Summary

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

Please help in reviewing the same.

Z3 link : http://www.rise4fun.com/Z3/FslAug

Thanks,
Suyog

[suyog]

Gentle Ping !!

Patch won't take much time to review :)

[majnemer]

LGTM

[suyog]

Closed by commit rL214476 (authored by @suyog).

lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

if (BinaryOperator *B = dyn_cast<BinaryOperator>(A))
           Op1->hasOneUse() && (B->getOpcode() == Instruction::Or ||
                                B->getOpcode() == Instruction::Xor)) {
         Value *NotOp = Op0 == B->getOperand(0) ? B->getOperand(1) :
                                                  B->getOperand(0);
         Value *Not = Builder->CreateNot(NotOp, NotOp->getName()+".not");
         return BinaryOperator::CreateOr(Not, Op0);
       }
 
+  // (A & B) | ((~A) ^ B) -> (~A ^ B)
+  if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
+      match(Op1, m_Xor(m_Not(m_Specific(A)), m_Specific(B))))
+    return BinaryOperator::CreateXor(Builder->CreateNot(A), B);
+
+  // ((~A) ^ B) | (A & B) -> (~A ^ B)
+  if (match(Op0, m_Xor(m_Not(m_Value(A)), m_Value(B))) &&
+      match(Op1, m_And(m_Specific(A), m_Specific(B))))
+    return BinaryOperator::CreateXor(Builder->CreateNot(A), B);
+
   if (SwappedForXor)
     std::swap(Op0, Op1);
 
   if (ICmpInst *RHS = dyn_cast<ICmpInst>(I.getOperand(1)))
     if (ICmpInst *LHS = dyn_cast<ICmpInst>(I.getOperand(0)))
       if (Value *Res = FoldOrOfICmps(LHS, RHS))
         return ReplaceInstUsesWith(I, Res);
 

test/Transforms/InstCombine/or.ll

 ; CHECK-LABEL: test40(
 ; CHECK-NEXT:   %1 = xor i32 %a, -1 
 ; CHECK-NEXT: %or = or i32 %1, %b
  %and = and i32 %a, %b
  %xor = xor i32 %a, -1
  %or = or i32 %and, %xor
  ret i32 %or
 }
+
+define i32 @test43(i32 %a, i32 %b) {
+; CHECK-LABEL: test43(
+; CHECK-NEXT: %1 = xor i32 %a, -1
+; CHECK-NEXT: %or = xor i32 %1, %b
+  %and = and i32 %a, %b
+  %nega = xor i32 %a, -1
+  %xor = xor i32 %nega, %b
+  %or = or i32 %and, %xor
+  ret i32 %or
+}
+
+define i32 @test44(i32 %a, i32 %b) {
+; CHECK-LABEL: test44(
+; CHECK-NEXT: %1 = xor i32 %a, -1
+; CHECK-NEXT: %or = xor i32 %1, %b
+  %nega = xor i32 %a, -1
+  %xor = xor i32 %nega, %b
+  %and = and i32 %a, %b
+  %or = or i32 %xor, %and
+  ret i32 %or
+}