https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67463
Bug ID: 67463 Summary: PGO (Profile Guided Optimizations) are not applied with gcc-5.2.1 (they are fine on gcc-4.9.x) Product: gcc Version: 5.2.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: pending Assignee: unassigned at gcc dot gnu.org Reporter: shlomif at shlomifish dot org Target Milestone: --- With these source files: http://www.shlomifish.org/Files/files/arcs/investigate-gcc-PGO-0.2.0.tar.xz Generated from tag "0.2.0" of the repository at https://github.com/shlomif/investigate-lack-of-PGO-in-gcc-5.2.x--re-fc-solve and by following the instructions in the README namely: <<< 1. Make sure gcc, GNU make , etc. are in the path (a GNU/Linux system is preferable). Also install libtcmalloc, which is part of the gperftools / google-perftools package. 2. cd to the source/ directory and type "bash RUN_PGO.bash" . This will build everything. 3. Type "bash RUN_ME_TO_TIME.bash" to time the results. Here (= Mageia Linux x86-64 6/Cauldron) the gcc-4.9.x results are faster than those of the ones with gcc-5.2.1-0.20150811.4.mga6 . >>> Then I'm getting the benchmarks for the PGO version of the sources running at about 9.29seconds with gcc-5.2.1 while at gcc-4.9.x they are about 9.00seconds. It seems that for some reason -fprofile-use has no effect in gcc-5.2.1. Regards, -- Shlomi Fish