erichkeane added a comment. In D147714#4251208 <https://reviews.llvm.org/D147714#4251208>, @xbolva00 wrote:
>>> Could we instead encode the platform specific tail-call rules in Sema? We >>> definitely have attributes that differ in behavior between platforms, and >>> this seems like a perfect candidate. > > But then you break promise of musttail that code with musttail will work on > any target supported by LLVM. I should have been clearer: I meant this with a new attribute. > Plus, while we can relax frontend checks (based on target info), it is true > that current LLVM LangRef says that there must be a match between prototypes. Right, this would require its own llvm-level concept as well. >>> Higher-level question: are we sure there's enough evidence this will be >>> used in practice to warrant adding it to Clang? > > Originally mentioned as request for CTRE project, I have use cases as well, > @jacobsa (Github issue) mentioned it: > >> Personally I would like the semantics "give me an error if this can't be a >> tail call on this target", not the semantics "give me an error if this can't >> be a tail call on all targets clang supports". I suspect most people would >> be looking for the former, since most people care about nearly none of the >> supported targets by volume. > > I agree with that. I see value in that, absolutely, but this isn't the way about it. Said new attribute (whether it be `[[should_tail]]` for `[[nonportable_musttail]]`) shouldn't be diagnosing the code generator, it should be diagnosing in SEMA. This requires encoding the platform specific/LLVM-IR specific rules. If LLVM-IR docs require `musttail` rules (that this patch seems to be breaking!), we perhaps need an alternative at the IR level as well. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D147714/new/ https://reviews.llvm.org/D147714 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
