Re: -fprofile-generate and -fprofile-use

[girish vaitheeswaran <girish_vaithees at yahoo dot com>]

I am using -O3. This is the only flag apart from the
profile flag -fprofile-use.

I had independently tried -march=pentium4 and that did
not buy any performance for this app.

-girish

--- Kelley Cook <kcook34@ford.com> wrote:

> > I started with a clean slate in my build
> environment 
> > and did not have any residual files hanging
> around. 
> > Are the steps I have indicated in my earlier email
> 
> > correct. Is there a way I can break down the
> problem 
> > into a smaller sub-set of flags and eliminate the
> flag 
> > causing the performance problem. What I mean is
> since 
> > -fprofile-generate and -fprofile-use enable a
> bunch of 
> > flags, would it make sense to avoid profiling and
> try 
> > out some of the individual flags on a trial and
> error 
> > basis. If so what would be the flags to start the 
> > trials with.
> > 
> > -girish
> 
> Before we go any farther, are you sure that you are
> also turning on optimization with -fprofile-generate
> and -fprofile-use?
> 
> In other words, you aren't just using "gcc
> -fprofile-generate xxx.c" to create your object
> files are you?
> 
> You need to use something like "gcc -O2
> -march=pentium4 -fprofile-generate" as unoptimized
> profiles are pretty pointless.
> 
> Instead of general terms, specific examples would
> help a lot.  Like a link to your code that is having
> problems.
> 
> Kelley Cook
> 
>