[llvm] r247061 - refactor matches for De Morgan's Laws; NFCI

[Sanjay Patel via llvm-commits]

Sorry, I'm not understanding. Are you referring to the opcode selection of
'and' / 'or' before calling CreateBinOp()? That's a result of hoisting the
code so it can be called from visitAnd / visitOr, and I added the assert to
make sure this helper wouldn't be misused. Let me know if there's a hole in
that logic.


On Wed, Sep 9, 2015 at 2:27 PM, David Majnemer <david.majnemer at gmail.com>
wrote:

>
>
> On Tue, Sep 8, 2015 at 1:14 PM, Sanjay Patel via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: spatel
>> Date: Tue Sep  8 15:14:13 2015
>> New Revision: 247061
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=247061&view=rev
>> Log:
>> refactor matches for De Morgan's Laws; NFCI
>>
>> Modified:
>>     llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
>>
>> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp?rev=247061&r1=247060&r2=247061&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
>> (original)
>> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp Tue
>> Sep  8 15:14:13 2015
>> @@ -1200,6 +1200,34 @@ Value *InstCombiner::FoldAndOfFCmps(FCmp
>>    return nullptr;
>>  }
>>
>> +/// Match De Morgan's Laws:
>> +/// (~A & ~B) == (~(A | B))
>> +/// (~A | ~B) == (~(A & B))
>> +static Instruction *matchDeMorgansLaws(BinaryOperator &I,
>> +                                       InstCombiner::BuilderTy *Builder)
>> {
>> +  auto Opcode = I.getOpcode();
>> +  assert((Opcode == Instruction::And || Opcode == Instruction::Or) &&
>> +         "Trying to match De Morgan's Laws with something other than
>> and/or");
>> +
>> +  Value *Op0 = I.getOperand(0);
>> +  Value *Op1 = I.getOperand(1);
>> +  // TODO: Use pattern matchers instead of dyn_cast.
>> +  if (Value *Op0NotVal = dyn_castNotVal(Op0))
>> +    if (Value *Op1NotVal = dyn_castNotVal(Op1))
>> +      if (Op0->hasOneUse() && Op1->hasOneUse()) {
>> +        // Flip the logic operation.
>> +        if (Opcode == Instruction::And)
>> +          Opcode = Instruction::Or;
>> +        else
>> +          Opcode = Instruction::And;
>>
>
> Excuse me but how is this "no functional change" ?  I don't believe we had
> the logic to conditional create an Or before.
>
>
>> +        Value *LogicOp = Builder->CreateBinOp(Opcode, Op0NotVal,
>> Op1NotVal,
>> +                                              I.getName() + ".demorgan");
>> +        return BinaryOperator::CreateNot(LogicOp);
>> +      }
>> +
>> +  return nullptr;
>> +}
>> +
>>  Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
>>    bool Changed = SimplifyAssociativeOrCommutative(I);
>>    Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
>> @@ -1330,15 +1358,8 @@ Instruction *InstCombiner::visitAnd(Bina
>>          return NV;
>>    }
>>
>> -
>> -  // (~A & ~B) == (~(A | B)) - De Morgan's Law
>> -  if (Value *Op0NotVal = dyn_castNotVal(Op0))
>> -    if (Value *Op1NotVal = dyn_castNotVal(Op1))
>> -      if (Op0->hasOneUse() && Op1->hasOneUse()) {
>> -        Value *Or = Builder->CreateOr(Op0NotVal, Op1NotVal,
>> -                                      I.getName()+".demorgan");
>> -        return BinaryOperator::CreateNot(Or);
>> -      }
>> +  if (Instruction *DeMorgan = matchDeMorgansLaws(I, Builder))
>> +    return DeMorgan;
>>
>>    {
>>      Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
>> @@ -2360,14 +2381,8 @@ Instruction *InstCombiner::visitOr(Binar
>>    if (match(Op0, m_And(m_Or(m_Specific(Op1), m_Value(C)), m_Value(A))))
>>      return BinaryOperator::CreateOr(Op1, Builder->CreateAnd(A, C));
>>
>> -  // (~A | ~B) == (~(A & B)) - De Morgan's Law
>> -  if (Value *Op0NotVal = dyn_castNotVal(Op0))
>> -    if (Value *Op1NotVal = dyn_castNotVal(Op1))
>> -      if (Op0->hasOneUse() && Op1->hasOneUse()) {
>> -        Value *And = Builder->CreateAnd(Op0NotVal, Op1NotVal,
>> -                                        I.getName()+".demorgan");
>> -        return BinaryOperator::CreateNot(And);
>> -      }
>> +  if (Instruction *DeMorgan = matchDeMorgansLaws(I, Builder))
>> +    return DeMorgan;
>>
>>    // Canonicalize xor to the RHS.
>>    bool SwappedForXor = false;
>>
>>
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>>
>
>
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