jfb added inline comments.
================ Comment at: test/Sema/sizeless-1.c:66 + _Static_assert(__atomic_always_lock_free(1, &local_int8) == __atomic_always_lock_free(1, incomplete_ptr), ""); + _Static_assert(__atomic_always_lock_free(2, &local_int8) == __atomic_always_lock_free(2, incomplete_ptr), ""); + ---------------- rsandifo-arm wrote: > jfb wrote: > > I expect sizeless types are never lock free. > Yeah, that's right. But AIUI `__atomic_always_lock_free(N, P)` asks whether > an N-byte access at P is lock-free (where P can be null to query standard > alignment). So the question isn't whether sizeless types are lock-free, but > whether an N-byte access is lock-free given the alignment guarantees of P. > For this line the answer would be yes if `&local_int8` was aligned to a > 2-byte boundary. > > The query isn't really that interesting for sizeless types. The reason for > having it is that `IntExprEvaluator::VisitBuiltinCallExpr` says that 1-byte > accesses are lock-free if the target has lock-free accesses, whatever P > happens to be. But for larger N it punts when P is a pointer to incomplete > type, because in that case it knows nothing about the alignment of P. The > test is enforcing this behaviour for sizeless types too. Ah yes, that makes sense. Thanks! Repository: rC Clang CHANGES SINCE LAST ACTION https://reviews.llvm.org/D62962/new/ https://reviews.llvm.org/D62962 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
