From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 16153 invoked by alias); 3 Jan 2013 09:05:30 -0000 Received: (qmail 16137 invoked by uid 22791); 3 Jan 2013 09:05:29 -0000 X-SWARE-Spam-Status: No, hits=-4.9 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,KHOP_RCVD_TRUST,KHOP_THREADED,RCVD_IN_DNSWL_LOW,RCVD_IN_HOSTKARMA_YE X-Spam-Check-By: sourceware.org Received: from mail-we0-f172.google.com (HELO mail-we0-f172.google.com) (74.125.82.172) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 03 Jan 2013 09:05:23 +0000 Received: by mail-we0-f172.google.com with SMTP id r3so7202583wey.17 for ; Thu, 03 Jan 2013 01:05:21 -0800 (PST) MIME-Version: 1.0 Received: by 10.180.39.143 with SMTP id p15mr73595549wik.14.1357203921768; Thu, 03 Jan 2013 01:05:21 -0800 (PST) Received: by 10.194.179.130 with HTTP; Thu, 3 Jan 2013 01:05:21 -0800 (PST) In-Reply-To: References: <20121221064539.0E1A7100704@rong.mtv.corp.google.com> <20121221092532.GA7055@kam.mff.cuni.cz> Date: Thu, 03 Jan 2013 09:05:00 -0000 Message-ID: Subject: Re: atomic update of profile counters (issue7000044) From: Richard Biener To: Andrew Pinski Cc: Rong Xu , Xinliang David Li , Jan Hubicka , GCC Patches , reply@codereview.appspotmail.com Content-Type: text/plain; charset=ISO-8859-1 X-IsSubscribed: yes Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org X-SW-Source: 2013-01/txt/msg00088.txt.bz2 On Thu, Jan 3, 2013 at 2:25 AM, Andrew Pinski wrote: > On Wed, Jan 2, 2013 at 5:15 PM, Rong Xu 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? Also note that not all targets support 'weak' linkage. Richard. > Thanks, > Andrew Pinski > > > >> >> Thanks, >> >> -Rong >> >> >> On Fri, Dec 28, 2012 at 11:35 AM, Xinliang David Li 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 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 wrote: >>>>> On Fri, Dec 21, 2012 at 1:25 AM, Jan Hubicka 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=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 >>>>>>> >>>>>>> * 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