Re: Implement C11 _Atomic

["Joseph S. Myers" <joseph at codesourcery dot com>]

On Fri, 8 Nov 2013, Dominique Dhumieres wrote:

> This revision may also causes the failures of
> gfortran.dg/typebound_operator_9.f03 and 
> FAIL: gfortran.fortran-torture/execute/forall_1.f90.

I doubt the patch affects Fortran (there are language-independent changes, 
but they are fairly small and shouldn't affect code not using _Atomic 
qualifiers).

> Undefined symbols for architecture i386:
>   "___atomic_compare_exchange_16", referenced from:

>   "___atomic_load_16", referenced from:

Either those functions should be in libatomic (using locking where 
necessary), or the built-in functions should be expanding to use the 
size-generic libatomic function rather than the _16 one.  Richard or 
Andrew should be able to advise on which the design was for systems that 
don't have lock-free atomics for all of the standard sizes (1, 2, 4, 8, 
16).

My guess is that it would be hard to provide the _16 functions in 
libatomic when TImode types aren't supported, and so the bug is that _16 
function calls are generated when not supported.  That is, c-common.c 
functions resolve_overloaded_atomic_exchange, 
resolve_overloaded_atomic_compare_exchange, 
resolve_overloaded_atomic_load, resolve_overloaded_atomic_store, where 
they check n != 16, should do something like (n != 16 || 
!targetm.scalar_mode_supported_p (TImode)).  (Better, refactor the (n != 1 
&& n != 2 && n != 4 && n != 8 && n != 16) into an atomic_size_supported_p 
or similar function.)

-- 
Joseph S. Myers
joseph@codesourcery.com