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profile directed feedback.
- From: girish vaitheeswaran <girish_vaithees at yahoo dot com>
- To: gcc-help at gcc dot gnu dot org
- Date: Tue, 12 Jul 2005 13:29:21 -0700 (PDT)
- Subject: profile directed feedback.
Has anyone gotten performance gains on account of
profile directed feedback optimization. I used
gcc-3.4.3 and tried using profile directed feedback.
This is what I did
1. Compiled the program using -fprofile-generate. I
used this flag both in the compile flags and as part
of the link flags. I also had to use libgcov.a during
the link phase otherwise it would die looking for gcov
functions.
2. Ran a representative work-load
3. Followed (1) except that instead of
-fprofile-generate used -fprofile-use
I had to drop the "-fprofile-use" on 2 files as they
had corrupted profile data. So far so good.
When I ran the profile directed feedback optimized
executable, the performance was 20% slower.
Anyone has experience with PDF they can share and
point out what I am doing wrong?
Thanks
-girish