> 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? Honza
