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
