Re: [PATCH] Add atomic type qualifier

[Andrew MacLeod <amacleod@redhat.com>]

On 07/30/2013 09:44 AM, Andrew MacLeod wrote:
> On 07/30/2013 09:16 AM, Joseph S. Myers wrot
>
>
>>> THis also means that for the 3 floating point operations all we need 
>>> are RTL
>>> insn patterns, no buitin.  And as with the other atomics, if the 
>>> pattern
>> I think something will also be needed to specify allocation of the 
>> fenv_t
>> temporary (whether in memory or registers).
>>
>>> doesnt exist, we just wont emit it.  we could add a warning easily 
>>> enough in
>>> this case.
>> Note there's a difference between no need to emit it, no warning 
>> should be
>> given (soft float) and need to emit it but patterns not yet written so
>> warning should be given (hard float but patterns not yet implemented for
>> the architecture).
>
> In fact, the flag could be the presence of the fenv_t variable.. Null 
> for that variable field in the builtin indicate you don't need the 
> patterns emitted.
>
> I';ll get back to you in a bit with the actual built-in's format once 
> I poke around the existing one and see how I can leverage it. I 
> rewrote all that code last year and it ought to be pretty simple to 
> add new operand support.  It better be anyway :-)
>

I worked out the built-ins and what they need to do... and you know 
what?  I'm not sure I see the point any more.

I am going to give a shot at simply expanding this code right in the 
front end.   For the floating and complex types I'll create temps and 
pass them to the generic atomic routines for load and 
compare_exchange... I should be able to directly call the same routines 
that sort out what can be mapped to lock free and what can't.  And in 
the end, the optimizers can sort out how to make things better. that way 
we dont need any support anywhere else. (well, we may need 3 builtins 
for the floating point stuff.. I don't know..  I'll worry about that later.)

On a side note,  after Friday, I'm off for 2 weeks, so I'll be pretty 
quiet until  the 19th or 20th.

Btw, if anyone wants to take a stab at a stdatomic.h file, that would be 
OK with me :-)

Andrew