Re: [PATCH] middle-end, c++, i386, libgcc: std::bfloat16_t and __bf16 arithmetic support

[Joseph Myers <joseph@codesourcery.com>]

On Tue, 4 Oct 2022, Jakub Jelinek via Gcc-patches wrote:

> Yet another problem is because I've only enabled the bf16/BF16 suffixes in
> C++ because for C it might clash with some later extension.  Am I right to
> fear about that, or do you think C will never standardize suffixes that
> would clash with that because C++ standardized the bf16/BF16 suffixes for
> something already?  If I could enable it, I'd always pedwarn for C for those

I think any C proposal to standardize something conflicting with C++ would 
get objections from the WG21 liaison.

> Another question is the suffixes of the builtins.  For now I have added
> bf16 suffix and enabled the builtins with !both_p, so one always needs to
> use __builtin_* form for them.  None of the GCC builtins end with b,
> so this isn't ambiguous with __builtin_*f16, but some libm functions do end
> with b, in particular ilogb, logb and f{??,??x}sub.  ilogb and the subs
> always have it, but is __builtin_logbf16 f16 suffixed logb or bf16 suffixed
> log?  Shall the builtins use f16b suffixes instead like the mangling does?

Indeed, that conflict means bf16 isn't suitable for the built-in function 
suffix.

-- 
Joseph S. Myers
joseph@codesourcery.com