Re: [Linuxsampler-devel] profiling, etc.

[Vladimir S. <ha...@gm...>]

Hello Garett,

Feel free to upgrade your gcc. I can easily reproduce this problem on
my system using 3.2.3 gcc. and unfortunately many subsequent problems
too :(
I have a few versions of GCC on my test system and i don't mind to
have as many as disk permits, i'm just putting then in different
prefixes.
So don't let this problem put your upgrades on hold.

Some of the problems with "not enough registers" i can easily fix, but
those fixes are most likely going to hurt performance (somewhat, hard
to tell exactly by how much).
Some of the problems with internal errors are not as easy to fix
though. I'm stuck with some problem in the filter code, i think gcc is
confused by the fact that we are trying to inline everything . . .
this is a known gcc bug and it looks like it is not going to be fixed
on 3.2.x because someone in gcc land deemed 3.2 not supported and
advised folks to upgrade.

Another issue is that old gcc won't inline some of the things that new
gcc can. So performance of the code built with newer gcc will in most
cases be better.

Long story short i'm considering fixing the code up so that there is a
macro ASM_SYNTHESIZER (or something like that). It could be driven by
platrorm specific macros like ARCH_X86 (and other architectures where
synthesizer will be implemented in assembly) OR gcc version being
below 3.3 or something like that.
I'd appreciate any comments, thoughts, etc on this from all interested
parties :)

Also, if you do upgrade gcc please let us know of any LS bugs you see
(assuming the build will be OK after the upgrade ;)

Regards,
Vladimir.

PS: i'm not very "debian aware" so if someone could enlighten me on
what the gcc situation  is in debian i'd appreciate it. i think debian
packaging is very important and it is therefore important to
understand the state they are in as far as gcc versions are concerned.

On Mon, 20 Dec 2004 19:33:58 -0700, Garett Shulman
<shu...@co...> wrote:
> Hello Christian, I will try your suggestion this evening. Also, I
> noticed that I replied to Vladimir this morning instead of the list. The
> version of gcc that I am using is 3.2.3 (Debian). I can try upgrading
> this to whatever debian unstable is now at. I can also just leave the
> current version to test any fixes for this issue. Thanks. -Garett
> 
> Christian Schoenebeck wrote:
> 
> >Es geschah am Dienstag 21 Dezember 2004 14:33 als Vladimir Senkov schrieb:
> >
> >
> >>Hi Garett,
> >>
> >>This is a bummer. GCC can't find enough registers for assembly code to use.
> >>We've had these problems on and off and had to guide it a bit in these
> >>areas. In general, building with -O2 seems to have a better chance
> >>then -O1 or -O0.
> >>But it looks like you already have -O2 there.
> >>
> >>
> >
> >I was able to reproduce this with some GCC version coming with Redhat 9.
> >Unfortunately the hard drive is currently detached on that box and I forgot
> >to look for the GCC version. But I will look at it ASAP.
> >
> >Garett, in the meantime you can disable LS to be compiled with MMX SSE
> >optimization. Even without those it's faster than with previous versions. Do
> >the following:
> >
> > * comment out all SynthesizeFragment_modeX() methods in
> >   src/engines/gig/Synthesizer.cpp from mode 32 to the end, thus all which use
> >   the ASM_X86_MMX_SSE typedef in their method body
> >
> > * comment out all respective cases from 32 to the end in
> >   GetSynthesisFunction() (same file)
> >
> > * and finally place a simple 'return' or something at the beginning of method
> >   Features::detect(), so it won't detect MMX / SSE on your box
> >
> >CU
> >Christian
> >
> >
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-- 
Regards,
Vladimir