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
