[PATCH] Detect whether target can use -fprofile-update=atomic

[Martin Liška]

On 08/16/2016 04:30 PM, Nathan Sidwell wrote:
> On 08/16/16 08:55, Martin Liška wrote:
>> Hello.
>>
>> As reported in [1], m68k has been broken since I installed the patch. Reason is that the target
>> does not support atomic operations (add, or) for a mode of gcov_type. Because of that, we see
>> an undefined symbols.
>>
>> Proper fix contains of 2 parts:
>> a) compiler emission must verify that -fprofile-update=atomic is doable for a given target; it's done
>> via a new function can_generate_atomic_builtin
>> b) libgcc must detect whether __atomic_fetch_add_x can be expanded on the target; that requires configure
>> support and if the target is not capable to expand these, we must conditionally remove all gcov_.*profiler_atomic
>> functions from libgcov.a.
> 
> I'm fine with the coverage-pecific changes, but the new hooks etc are not something I can approve.
> 
> gcc/ChangeLog:
> 
> 2016-08-12  Martin Liska  <mliska@suse.cz>
> 
>     * optabs.c (can_generate_atomic_builtin): New function.
>     * optabs.h (can_generate_atomic_builtin): Declare the function.
> Need GWM or similar review
> 
>     * tree-profile.c (tree_profiling):  Detect whether target can use
>     -fprofile-update=atomic.
> ok
> 
> gcc/testsuite/ChangeLog:
> 
> 2016-08-12  Martin Liska  <mliska@suse.cz>
> 
>     * gcc.dg/profile-update-warning.c: New test.
> ok
> 
> libgcc/ChangeLog:
> 
> 2016-08-16  Martin Liska  <mliska@suse.cz>
> 
>     * acinclude.m4: New file.
>     * config.in: New macro defines.
>     * configure: Regenerated.
>     * configure.ac: Detect atomic operations.
> need GWM or similar review
> 
>     * libgcov-profiler.c: Detect GCOV_SUPPORTS_ATOMIC and
>     conditionaly enable/disable *_atomic functions.
> OK.
> 
> nathan

Hi Nathan.

Thanks for review, I'm CCing Jakub and Richard for the review.
The patch should fix very similar issue spotted on AIX target by David.

Thanks,
Martin