[llvm-commits] CVS: llvm/lib/VMCore/ConstantFolding.cpp

[Chris Lattner]

On Dec 18, 2006, at 7:16 PM, Reid Spencer wrote:

> Rewrite ConstantFoldCastInstruction so that it doesn't use any of the
> ConstRules. Remove the casting rules from ConstRules and  
> subclasses. This
> cleans up ConstantFolding significantly. Passes all tests.

Nice!

>   case Instruction::UIToFP: {
> +    // First, extract the unsigned integer value
> +    uint64_t Val;
> +    if (isa<ConstantInt>(V))
> +      Val = cast<ConstantIntegral>(V)->getZExtValue();
> +    else if (const ConstantBool *CB = dyn_cast<ConstantBool>(V))
> +      Val = CB->getValue() ? 1 : 0;

ConstantBool is ConstantIntegral.  You should be able to do:

> +    if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(V))
> +      Val = CI->getZExtValue();

to handle both cases.

> +    // Now generate the equivalent floating point value
> +    double dVal = (double) Val;
> +    return ConstantFP::get(DestTy, dVal);
> +  }
> +  case Instruction::SIToFP: {
> +    // First, extract the signed integer value
> +    int64_t Val;
> +    if (isa<ConstantInt>(V))
> +      Val = cast<ConstantIntegral>(V)->getSExtValue();
> +    else if (const ConstantBool *CB = dyn_cast<ConstantBool>(V))
> +      Val = CB->getValue() ? -1 : 0;

Likewise.

> +    // Now generate the equivalent floating point value
> +    double dVal = (double) Val;
> +    return ConstantFP::get(DestTy, dVal);
> +  }
>    case Instruction::ZExt:
> +    // Handle trunc directly here if it is a ConstantIntegral.
>      if (isa<ConstantInt>(V))
> +      return ConstantInt::get(DestTy, cast<ConstantInt>(V)- 
> >getZExtValue());
> +    else if (const ConstantBool *CB = dyn_cast<ConstantBool>(V))
> +      return ConstantInt::get(DestTy, CB->getValue() ? 1 : 0);

Likewise, also, please correct the comment.

> +    return 0;
>    case Instruction::SExt:
>      // A SExt always produces a signed value so we need to cast  
> the value
>      // now before we try to cast it to the destiniation type.
>      if (isa<ConstantInt>(V))
> +      return ConstantInt::get(DestTy, cast<ConstantInt>(V)- 
> >getSExtValue());
>      else if (const ConstantBool *CB = dyn_cast<ConstantBool>(V))
> +      return ConstantInt::get(DestTy, CB->getValue() ? -1 : 0);

Likewise.

> +    return 0;
>    case Instruction::Trunc:
>      // We just handle trunc directly here.  The code below doesn't  
> work for
>      // trunc to bool.
> @@ -896,7 +743,8 @@
>        return ConstantIntegral::get(DestTy, CI->getZExtValue());
>      return 0;
>    case Instruction::BitCast:
> -    if (SrcTy == DestTy) return (Constant*)V; // no-op cast
> +    if (SrcTy == DestTy)
> +      return (Constant*)V; // no-op cast

Does this fold (int)4U ?

-Chris