Using FDO to speed up compiler?

[Richard Henderson]

On Wed, Feb 12, 2003 at 10:17:10PM +0100, Jan Hubicka wrote:
> The number reminds me not-so-related note.  I've also hacked makefiles
> in the past to add profiling into the bootstrap.  I used "make check"
> for train run and measured speedup in between 5-10% on compiling 
> on compiling binutils on early rtlopt-branch tree.

Nice.

> Do we want such a machinery in mainline? Using FDO for compiler seems to
> make sense, but it makes bootstrap much longer.  I set it up as
> "profiledbootstrap" in makefile that would imply that for development we
> will use different switches that for production that can cause problems
> in future...
> Also getting this right for crosscompilation may be dificult.

Cross-compilation doesn't bootstrap.  You just "make all" instead.

I think it would be interesting to have this in place.  Could be 
useful for distributions packaging the compiler.  Pay the extra
bootstrap time up front for a nice improvement to the users.


r~