On Tue, Sep 6, 2016 at 6:45 AM, Martin Liška <mli...@suse.cz> wrote:
>>> Proper fix contains of 2 parts: >>> a) compiler emission must verify that -fprofile-update=atomic is doable for >>> a given target; it's done >>> via a new function can_generate_atomic_builtin >>> b) libgcc must detect whether __atomic_fetch_add_x can be expanded on the >>> target; that requires configure >>> support and if the target is not capable to expand these, we must >>> conditionally remove all gcov_.*profiler_atomic >>> functions from libgcov.a. >> >> I'm fine with the coverage-pecific changes, but the new hooks etc are not >> something I can approve. >> >> gcc/ChangeLog: >> >> 2016-08-12 Martin Liska <mli...@suse.cz> >> >> * optabs.c (can_generate_atomic_builtin): New function. >> * optabs.h (can_generate_atomic_builtin): Declare the function. >> Need GWM or similar review >> >> * tree-profile.c (tree_profiling): Detect whether target can use >> -fprofile-update=atomic. >> ok >> >> gcc/testsuite/ChangeLog: >> >> 2016-08-12 Martin Liska <mli...@suse.cz> >> >> * gcc.dg/profile-update-warning.c: New test. >> ok >> >> libgcc/ChangeLog: >> >> 2016-08-16 Martin Liska <mli...@suse.cz> >> >> * acinclude.m4: New file. >> * config.in: New macro defines. >> * configure: Regenerated. >> * configure.ac: Detect atomic operations. >> need GWM or similar review >> >> * libgcov-profiler.c: Detect GCOV_SUPPORTS_ATOMIC and >> conditionaly enable/disable *_atomic functions. >> OK. >> >> nathan > > Hi Nathan. > > Thanks for review, I'm CCing Jakub and Richard for the review. > The patch should fix very similar issue spotted on AIX target by David. What about Jakub's comment in the PR? https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77378#c6 The proposed patch seems wrong or at least incomplete. The recent change is imposing a 64 bit DImode counter when producing 32 bit code. PowerPC does support 64 bit atomic operations in 32 bit mode. Was there a design decision that profile counters always should be 64 bits? Either 32 bit targets won't support multi-threaded profiling or 32 bit targets can overflow the counter sooner. Which is worse? Which is more likely? Thanks, David
