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

[David Majnemer via llvm-commits]

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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