[Bug gcov-profile/47618] New: Collecting multiple profiles and using all for PGO

[roland at rschulz dot eu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47618

           Summary: Collecting multiple profiles and using all for PGO
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: gcov-profile
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: roland@rschulz.eu


Currently only the file from one profiling run can be used for PGO. Especially
for MPI programs it would be nice if several folders containing profiling files
could be merged or several directories could be used together for
-fprofile-use.

For saving the profiling files it would be great if the folder name could
contain an environment variable or could be set by an environment variable.

Thus I suggest that one could either say:
-fprofile-dir /some/path/%q{SOME_ENV}  #same syntax as valgrind
or
export GCC_PROFILE_DIR=/some/path/$SOME_ENV

This would be very useful because MPI implementation provide the MPI rank as a
environment variable. Thus with the suggestion one could store the profile of
each MPI rank in a different folder.