[PATCH 1/3][AArch64][PR target/65797] Strengthen barriers for sync-fetch-op builtins.

[Marcus Shawcroft]

>> Attached updated patch:
>> - Expanded the comment for aarch64_emit_post_barrier.
>> - Used 'barrier' rather than 'fence' in comments.
>> - Simplified the code for the initial load.
>>
>> Tested with check-gcc for aarch64-none-linux-gnu.
>>
>> Ok?
>> Matthew
>>
>> 2015-06-01  Matthew Wahab  <matthew.wahab@arm.com>
>>
>>       PR target/65697
>>       * config/aarch64/aarch64.c (aarch64_split_compare_and_swap): Check
>>       for __sync memory models, emit initial loads and final barriers as
>>       appropriate.
>>
>
> OK,
>
> Thanks,
> James

We are emitting __sync primitives with insufficient barriers in gcc5
(and gcc4.9?) I would expect that anyone hitting this issue in
production will have a tough job debugging it.   We need to look at
back porting this patch set and the prerequisite patches.... Cheers
/Marcus