Re: gEDA-user: Icarus Verilog building from CVS

[Lars Segerlund <lars.segerlund@comsys.se>]

 Well, I am running some computationally intensive code, ( CFD ), and gcc 3.5 ( upcoming ) is giving a boost of up to 30 % for FORTRAN and C code in some instances.
 The 'new' gcc does have a much better optimization framework, and it is really starting to show, it should fx. be able to run head to head with intels compiler provided that it is supplied with a reasonable set of compiler flags, ( which is an area of itself :-) ).
 SO if you look for the code generated by the 'state of the art' gcc i do not believe your statement to be true, ( check out code for the sh and h8 processors or the mips32 instruction set ).

 If you have any cases which can be reduced to misoptimizations please post a bug report on gcc.gnu.org

 If not, ( and from my opinion and experience ), I can only conider your statement an ill informed opinion.

 ( btw. dec's compiler used to build on gcc :-) especially the openMP part ), and this should give some indication of the performance of gcc.

 The big thing I have against the beast is it's compilatioon speed and memory requirements, it's slow and big.

 / best regards, Lars Segerlund.


On Sat, 7 Aug 2004 00:07:51 -0400
Dave McGuire <mcguire@neurotica.com> wrote:

> On Aug 6, 2004, at 11:44 PM, Al Davis wrote:
> >>   Despite its popularity in the x86 world, GCC generates
> >> horrid code on most, if not all, modern RISC platforms.  The
> >> vendor-supplied compilers represent a tremendous amount of
> >> in-the-know optimization and well-funded development that is
> >> specific to their processor architectures.
> >
> > Really????
> 
>    Really. :)
> 
> > A few years ago, when I had access to a bunch of machines and a
> > bunch of compilers I tried ACS (precursor to Gnucap) on all of
> > them, with both GCC and the native one if possible.  The only
> > one that had any significant difference was Sun's.  The Sun
> > compiler was about 20% slower than GCC.  Has Sun's compiler
> > improved that much, or has GCC gotten that much worse?  Perhaps
> > Sun's compiler is better in some cases, and GCC better in
> > others?
> 
>    That's certainly possible.  I have enough data points, however, that 
> I don't even bother to install GCC on my Solaris systems anymore.
> 
>    Now bear in mind, this is coming from a long-time GCC lover.  Back In 
> The Day(tm), I remember the very first thing to do on any new VAX 
> system (running either VMS or UNIX) was to install GCC because it 
> generated code that was much faster.  The same went for M68K-based 
> Suns...GCC produced much, much faster executables than the 
> vendor-supplied compiler.  That said, however, M68K and VAX are 
> *extremely* CISC processors, designed to support compilers from the 
> ground up.  GCC's initial development was on processors like 
> that...Very CISC architectures, and that's where it really seems to 
> shine, even today.
> 
>    (except, of course, for all the non-standard crap that it allows that 
> many people unknowingly or uncaringly use, resulting in nonportable 
> code)
> 
>    But try it on a MIPS, SPARC, or other modern RISC or post-RISC 
> architecture and things don't look so good.  I've not done extensive 
> reading on this, but I'm told that the inclusion of IBM's Haifa 
> instruction scheduler in GCC a few years ago helped matters for RISC 
> architectures, but the situation still gives me that "not so fresh" 
> feeling.
> 
> > Having said that...  Looking at the assembly code for C++, I see
> > that they are still missing some significant optimizations that
> > are not possible in C.
> 
>    Hmm.  I'm not much into C++ (I'm a C guy) so I can't speak to that.  
> I'd love to see some examples though.
> 
>          -Dave
> 
> --
> Dave McGuire             "...it's a matter of how tightly
> Cape Coral, FL             you pull the zip-tie."       -Nadine Miller
>