[Bug pending/67463] New: PGO (Profile Guided Optimizations) are not applied with gcc-5.2.1 (they are fine on gcc-4.9.x)

["shlomif at shlomifish dot org" <gcc-bugzilla at gcc dot gnu dot org>]

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