jyknight added a comment. In D57450#1641190 <https://reviews.llvm.org/D57450#1641190>, @lenary wrote:
> @jyknight I hear where you're coming from. I'll see what I can do about the > psABI document. > > In that ticket, it's mentioned that the Darwin ABI explicitly says that > non-power-of-two atomic types should be padded and realigned, but I cannot > find any documentation explaining this. That would be useful, given > presumably GCC does have to pad/align on Darwin. AFAIK, there is no such documentation, at least publicly. Possibly Apple has some internally, but I suspect it more likely just some in-person conversation or something. GCC is not really supported on Darwin, so I suspect it just gets it wrong. > Then the only outstanding question relates to zero-sized atomics, which GCC > does not pad, but I think Clang has to pad to get the semantics correct, > based on this comment: > https://github.com/llvm/llvm-project/blob/master/clang/lib/AST/ASTContext.cpp#L2176 The semantics in GCC are that you can create such an object, but any attempt to load or store it will result in a compile-time error. E.g., "error: argument 1 of ‘__atomic_load’ must be a pointer to a nonzero size object". So I don't think there's really an issue there. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D57450/new/ https://reviews.llvm.org/D57450 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
