Re: [patch] Provide a can_compare_and_swap_p target hook.

[Andrew MacLeod <amacleod@redhat.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