[PATCH] D71726: Let clang atomic builtins fetch add/sub support floating point types

[Yaxun Liu via Phabricator via cfe-commits]

yaxunl added a comment.

In D71726#2351069 <https://reviews.llvm.org/D71726#2351069>, @rjmccall wrote:

>> Yes, there are no generically available libcalls for atomic float math -- but that's okay -- let LLVM handle transform into a cmpxchg loop when required.
>
> I suspect Yaxun's target cannot provide libcalls at all, which is why he wants to diagnose up-front.  But I agree that we should be thinking about this uniformly, and that his target should be diagnosing *all* unsupported atomics.

amdgpu target currently does not support atomic libcalls. I added a target hook for atomic operation support and diagnostics for generic atomic operations by John's comments.

Clang has existing diagnostics for unsupported atomic load/store for some platforms, and functions about atomic support scattered in target info, AST context, and codegen. This change refactors these codes and unify them as a target hook.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71726/new/

https://reviews.llvm.org/D71726