aaron.ballman added a subscriber: erichkeane. aaron.ballman added a comment.
In D150528#4342646 <https://reviews.llvm.org/D150528#4342646>, @yronglin wrote: > In D150528#4342600 <https://reviews.llvm.org/D150528#4342600>, @aaron.ballman > wrote: > >> In D150528#4342535 <https://reviews.llvm.org/D150528#4342535>, @yronglin >> wrote: >> >>> Thanks a lot for your review @aaron.ballman ! BTW, does the most good >>> approach is that we just add a new `ParsedAttribute` with `TypeSourceInfo` >>> but not an `UnaryExprOrTypeTraitExpr`, and only do a sema check same as >>> `alignof(type-id)`? >> >> Because you've already got a `ParsedAttr`, I think you'd use this >> constructor: >> https://github.com/llvm/llvm-project/blob/main/clang/include/clang/Sema/ParsedAttr.h#L274 >> and move the call to `GetTypeFromParser()` until later, but it should still >> be modelled as a `UnaryExprOrTypeTraitExpr`. > > Many thanks for the tips, I think the next step is to build > `UnaryExprOrTypeTraitExpr ` in this place > (https://github.com/llvm/llvm-project/blob/9715af434579022b5ef31781be40b722d7e63bee/clang/lib/Sema/SemaDeclAttr.cpp#L4335-L4358) > and then calculate the alignment? If this approach is correct, I'm glad to > investigate it. Hmm, not quite. Roping in @erichkeane in case he's got other ideas, but I think this will be more involved. What I think needs to happen is: - We need to add another argument to `Aligned` in Attr.td so that the attribute takes either an expression argument or a type argument. - We need to update SemaDeclAttr.cpp and other places accordingly - We need to add an overload of `Sema::AddAlignedAttr()` that takes a `ParsedType` and call this overload when given `alignas(type)` - We need to add code to TreeTransform.h to instantiate a dependent type so we can support `template <typename Ty> alignas(Ty) int foo = 12;` Your approach of creating a `UnaryExprOrTypeTraitExpr` would still end up having us model as `alignas(alignof(type))` because the argument to the `alignas` attribute would be the type trait. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D150528/new/ https://reviews.llvm.org/D150528 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
