[Bug lto/47916] New: Using -flto leads to halved performance of unrar unarchiver

["t.artem at mailcity dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47916

           Summary: Using -flto leads to halved performance of unrar
                    unarchiver
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: t.artem@mailcity.com


Created attachment 23483
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=23483
unrar sources

Using the last released GCC snapshot (gcc-4.6-20110226) and the following
compilation flags performance halves.

GCC flags used:

CXXFLAGS=-O2 -march=i686 -mtune=generic [-flto|]
LDFLAGS=[-flto|]

Execution times:



With -flto:

time ./unrar t -inul testarchive.rar

real    0m33.496s
user    0m33.171s
sys     0m0.140s




Without -flto:

time ./unrar t -inul testarchive.rar

real    0m16.326s
user    0m16.242s
sys     0m0.067s

___________________________________________________________________

This bug will probably attract zero attention from GCC developers but since
-flto is not meant to behave such badly I'm posting it.

You can produce a rar archive using Rar for Linux
(http://rarlabs.com/download.htm):

rar a -m5 -mdG -r -s archive.name.rar file1 file2 file3 ... etc.