Does libatomic support all targets? I think it's a good idea to change the driver to link in this library if the option is specified. But still, we need to make the builtin weak.
Thanks, -Rong On Wed, Jan 2, 2013 at 5:25 PM, Andrew Pinski <pins...@gmail.com> wrote: > On Wed, Jan 2, 2013 at 5:15 PM, Rong Xu <x...@google.com> wrote: >> Hi, >> >> Here is a new patch. The only difference is to declare >> __atomic_fetch_add as weak. This is >> needed for targets without sync/atomic builtin support. The patch >> contains a call to the builtin regardless of the new options >> -fprofile-gen-atomic. This results in a unsat in these targets even >> for regular profile-gen built. >> >> With this new patch, if the user uses -fprofile-gen-atomic in these >> target, the generated code will seg fault. >> >> We think a better solution is to emit the builtin call only in these >> targets with the support, and give warning for non-supported target. >> But I did not find any target hook for this. Does anyone know how to >> do this? > > Why not use libatomic for those targets? > > Thanks, > Andrew Pinski > > > >> >> Thanks, >> >> -Rong >> >> >> On Fri, Dec 28, 2012 at 11:35 AM, Xinliang David Li <davi...@google.com> >> wrote: >>> It would be great if this can make into gcc4.8. The patch has close to >>> 0 impact on code stability. >>> >>> David >>> >>> On Fri, Dec 28, 2012 at 11:32 AM, Rong Xu <x...@google.com> wrote: >>>> Hi Honza, >>>> >>>> In the other thread of discussion (similar patch in google-4_7 >>>> branch), you said you were thinking if to let this patch into trunk in >>>> stage 3. Can you give some update? >>>> >>>> Thanks, >>>> >>>> -Rong >>>> >>>> On Fri, Dec 21, 2012 at 10:37 AM, Rong Xu <x...@google.com> wrote: >>>>> On Fri, Dec 21, 2012 at 1:25 AM, Jan Hubicka <hubi...@ucw.cz> wrote: >>>>>>> Hi, >>>>>>> >>>>>>> This patch adds support of atomic update of profiles counters. The goal >>>>>>> is to improve >>>>>>> the poor counter values for highly thread programs. >>>>>>> >>>>>>> The atomic update is under a new option -fprofile-gen-atomic=<N> >>>>>>> N=0: default, no atomic update >>>>>>> N=1: atomic update edge counters. >>>>>>> N=2: atomic update some of value profile counters (currently >>>>>>> indirect-call and one value profile). >>>>>>> N=3: both edge counter and the above value profile counters. >>>>>>> Other value: fall back to the default. >>>>>>> >>>>>>> This patch is a simple porting of the version in google-4_7 branch. It >>>>>>> uses __atomic_fetch_add >>>>>>> based on Andrew Pinski's suggestion. Note I did not apply to all the >>>>>>> value profiles as >>>>>>> the indirect-call profile is the most relevant one here. >>>>>>> >>>>>>> Test with bootstrap. >>>>>>> >>>>>>> Comments and suggestions are welcomed. >>>>>>> >>>>>>> Thanks, >>>>>>> >>>>>>> -Rong >>>>>>> >>>>>>> >>>>>>> 2012-12-20 Rong Xu <x...@google.com> >>>>>>> >>>>>>> * libgcc/libgcov.c (__gcov_one_value_profiler_body_atomic): New >>>>>>> function. Atomic update profile counters. >>>>>>> (__gcov_one_value_profiler_atomic): Ditto. >>>>>>> (__gcov_indirect_call_profiler_atomic): Ditto. >>>>>>> * gcc/gcov-io.h: Macros for atomic update. >>>>>>> * gcc/common.opt: New option. >>>>>>> * gcc/tree-profile.c (gimple_init_edge_profiler): Atomic >>>>>>> update profile counters. >>>>>>> (gimple_gen_edge_profiler): Ditto. >>>>>> >>>>>> The patch looks resonable. Eventually we probably should provide rest >>>>>> of the value counters >>>>>> in thread safe manner. What happens on targets not having atomic >>>>>> operations? >>>>> >>>>> From >>>>> http://gcc.gnu.org/onlinedocs/gcc/_005f_005fsync-Builtins.html#_005f_005fsync-Builtins, >>>>> it says: >>>>> "If a particular operation cannot be implemented on the target >>>>> processor, a warning is generated and a call an external function is >>>>> generated. " >>>>> >>>>> So I think there will be a warning and eventually a link error of unsat. >>>>> >>>>> Thanks, >>>>> >>>>> -Rong >>>>> >>>>> >>>>>> >>>>>> Honza
