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

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67463

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |marxin at gcc dot gnu.org
         Resolution|---                         |WORKSFORME

--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
Hi.

Sorry for waiting for some time. I tested your benchmark, where I had to
disable tcmalloc as I can't link it with GCC 4.9, caused by C++ abi change. I
also enhanced dump output to print total time spent (when function
FCS_PRINT_FINISHED is called):

4.9.4:
Finished in 3.607
Finished in 3.613
Finished in 3.621
Finished in 3.662

5.4.0:
Finished in 3.643
Finished in 3.636
Finished in 3.630
Finished in 3.708

6.3.0:
Finished in 3.618
Finished in 3.618
Finished in 3.627
Finished in 3.652

Tested on my desktop machine with Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz.
That mentioned, I cannot see the regression, all numbers look within noise
level.
The regression you reported is very small (~3%) and it would be very hard to
compare generated assembly to find different decisions made by GCC. Please try
to
test GCC 6 and possible GCC 7 (which will be released in couple of weeks) and
if seen
a significant regress, please reopen the issue.