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

[suyog]

Summary

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

Please help in reviewing the same.

Z3 link : http://www.rise4fun.com/Z3/ld95

Thanks,
Suyog

[suyog]

Gentle Ping !!

Patch won't take much time to review :)

[majnemer]

LGTM

[suyog]

Closed by commit rL214479 (authored by @suyog).

llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

Instruction *InstCombiner::visitXor(BinaryOperator &I) {
   }
 
   // (A | B)^(~A) -> (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));
 
+  // (A & ~B) ^ (~A) -> ~(A & B)
+  if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
+      match(Op1, m_Not(m_Specific(A))))
+    return BinaryOperator::CreateNot(Builder->CreateAnd(A, 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) &&

llvm/trunk/test/Transforms/InstCombine/xor2.ll

define i32 @test12(i32 %A, i32 %B) {
   %xor1 = xor i32 %B, %A
   %not = xor i32 %A, -1
   %xor2 = xor i32 %not, %B
   %and = and i32 %xor1, %xor2
   ret i32 %and
 ; CHECK-LABEL: @test12(
 ; CHECK-NEXT: ret i32 0
 }
+
+define i32 @test13(i32 %a, i32 %b) {
+ %negb = xor i32 %b, -1
+ %and = and i32 %a, %negb
+ %nega = xor i32 %a, -1
+ %xor = xor i32 %and, %nega
+ ret i32 %xor
+; CHECK-LABEL: @test13(
+; CHECK-NEXT: %1 = and i32 %a, %b
+; CHECK-NEXT: %xor = xor i32 %1, -1
+}
+
+define i32 @test14(i32 %a, i32 %b) {
+ %nega = xor i32 %a, -1
+ %negb = xor i32 %b, -1
+ %and = and i32 %a, %negb
+ %xor = xor i32 %nega, %and
+ ret i32 %xor
+; CHECK-LABEL: @test14(
+; CHECK-NEXT: %1 = and i32 %a, %b
+; CHECK-NEXT: %xor = xor i32 %1, -1
+}