[PATCH] Generalize getExtendAddRecStart to work with both sign and zero extensions.

[Sanjoy Das]

Looks like I misinterpreted your review comment. :)  Does what I
checked in look okay though?

-- Sanjoy


On Tue, Feb 17, 2015 at 11:00 PM, Andrew Trick <atrick at apple.com> wrote:
> I can see how my comment about duplicating the typedef would seem silly. I was actually thinking about bringing the members defined by that type into the base, as shown below. But I didn't think it through because now that I write it out, the out-of-line static definitions are utterly horrid:
>
> template <SCEV::NoWrapFlags W, GetExtendExprTy ExtendF,
>
>   GetOverflowLimitForStepTy OverflowF>
>
> struct ExtendOpTraitsBase {
>
>   static const SCEV::NoWrapFlags WrapType = W;
>   static const GetExtendExprTy GetExtendExpr;
>   static const GetOverflowLimitForStepTy GetOverflowLimitForStep;
>
> };
>
> template <SCEV::NoWrapFlags W, GetExtendExprTy ExtendF,
>
>   GetOverflowLimitForStepTy OverflowF>
>
> const GetExtendExprTy ExtendOpTraitsBase<W, ExtendF, OverflowF>::
> GetExtendExpr = ExtendF;
>
> template <SCEV::NoWrapFlags W, GetExtendExprTy ExtendF,
>
>   GetOverflowLimitForStepTy OverflowF>
>
> const GetOverflowLimitForStepTy ExtendOpTraitsBase<W, ExtendF, OverflowF>::
> GetOverflowLimitForStep = OverflowF;
>
> template <typename ExtendOp> struct ExtendOpTraits {};
>
> template <>
> struct ExtendOpTraits<SCEVSignExtendExpr>
>
>   : public ExtendOpTraitsBase<SCEV::FlagNSW, getSignExtendExpr,
>                               getSignedOverflowLimitForStep>
>
> {};
>
> template <>
> struct ExtendOpTraits<SCEVZeroExtendExpr>
>
>   : public ExtendOpTraitsBase<SCEV::FlagNUW, getZeroExtendExpr,
>                               getUnsignedOverflowLimitForStep>
>
> {};
> ---
>
> Oh well, at any rate, you shouldn't need to refer to the type like this anymore:
> ExtendOpTraits<SCEVSignExtendExpr>::GetExtendExprTy
>
>
> REPOSITORY
>   rL LLVM
>
> http://reviews.llvm.org/D7645
>
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