Re: Need an older gcc version on my cygwin due to poor performance on gcc-3.x series.

[Reini Urban <rurban at x-ray dot at>]

Danny Smith schrieb:
> Gerrit P. Haase wrote:
> > Danny Smith wrote:
> > > Gerrit wrote:
> > > > Ole Jacob Hagen wrote:
> > > > > I've compiled Octave-2.1.60 with gcc-3.3.3 successfully, but the
> > > > > performance is pretty bad with gcc-3.3.3.
> > > > > The performance should of Octave is much better, when compiling it
> > > > > with gcc-3.2.x instead.
> > >
> > > > It would make more sense to identify the problem and do s.th.
> > > > about it to resolve this issue then.
> > >
> > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14563
> >
> > Wow, this is an interesting story about exception handling.
> >
> > What I'm asking myself now:
> >
> > Should we try again to use dwarf2 exceptions?
>
> My personal builds of gcc-3.4.x are bullt with dwarf2 EH enabled.  No
> problems But  I don't use w32 callbacks within functions that throw.  I
> had never even thought of doing that, but I don't think much.anymore

Max,
Do we use some win32 callbacks with exceptions in setup.exe?
I do see some candidates, but I didn't follow the codepath exactly.

On the other side, our setup.exe is not that performance critical as 
octave. But postgresql and apache are likely candidates for Dwarf2 
enabled builds. I experienced severe postgresql penalties with the 
latest builds, compared to earlier versions. current beta4 only allows 
MAX_CONNECTIONS=2, vs. ~50 with earlier gcc/postgresql. But postgresql 
internals also had changed a lot lately.

> > Should we try to find the reason why SjLj exceptions are slower on
> > Cygwin than for the rest of the world?
>
> Most of the rest of the GCC world has abandoned sjlj EH as inefficient
> Look  within function prologues.
--
Reini Urban
http://xarch.tu-graz.ac.at/home/rurban/

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