[patch] Provide a can_compare_and_swap_p target hook.

Andrew MacLeod amacleod@redhat.com
Fri Nov 7 13:31:00 GMT 2014


On 11/07/2014 04:31 AM, Andrew Haley wrote:
> On 06/11/14 19:05, Andrew MacLeod wrote:
>>
>> 1) Given that the compiler *always* provides support via libatomic now
>> (even if it is via locks), does that mean that VMSupportsCS8_builtin()
>> should always return true?
>>
>> or should we map to that a call to __atomic_always_lock_free() ? (that
>> always gets folded to a true or false at compile time)  my guess is the
>> latter?
> Perhaps so.  The problem is that some targets can't do CAS on 64-bit
> doublewords.
with libatomic present, I believe they always can, even if it drops to a 
lock implementation.

> I'm sorry, I really can't remember.  I can't think of any reason to
> want to turn off builtin support.  You have to remember that all this
> was written when our support for atomic builtins was seriously flaky
> and we would just punt back to the user anything we hadn't written
> yet.
>
>
No worries, i cant remember why i did something last year, let along 8 
years ago :-)

I'll take a best stab and we'll see what happens :-)

Andrew



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