Re: [patch] Provide a can_compare_and_swap_p target hook.

[Andrew MacLeod <amacleod at redhat dot com>]

On 11/04/2014 12:57 PM, Richard Henderson wrote:
> On 11/04/2014 06:56 PM, Andrew MacLeod wrote:
> > On 11/04/2014 12:25 PM, Richard Henderson wrote:
> > > On 11/04/2014 05:28 PM, Andrew MacLeod wrote:
> > > > + bool
> > > > + default_can_compare_and_swap_p (machine_mode mode, bool allow_libcall)
> > > > + {
> > > > +   return can_compare_and_swap_p (mode, allow_libcall);
> > > > + }
> > > This is silly.  I think the problem you point out can be better fixed by moving
> > > the can_compare_and_swap_p prototype elsewhere.
> > yeah, except it uses some of the optab table stuff that is static to
> > optabs.c...   so the basic functionality remains there.
> I said move the prototype.  Of course the implementation remains where it is.
prototype is in optabs.h where it belongs since its defined in 
optabs.c.  :-)

I'm not sure why this is much different than something like the targhook 
for builtin_support_vector_misalignment(), other than we are calling the 
routine in optabs.c rather than putting the actual code in targhooks.c.

from targhooks.c:
bool
default_builtin_support_vector_misalignment (machine_mode mode, 
const_tree type, <...>)
 {
  if (optab_handler (movmisalign_optab, mode) != CODE_FOR_nothing)
    return true;
  return false;
}

the idea is to move all the functionality that front ends need into well 
defined and controlled places so we can increase the separation.  "can 
perform a  compare_and_swap operation" is clearly a target specific 
question isn't it?

Andrew