C++ compile and execution times

[Karel Gardas]

Folks,

I'd like to add something to Wolfgang Bangerth's email
(http://gcc.gnu.org/ml/gcc/2002-11/msg00821.html).

Please don't take my notes as a criticism, you're doing great job on many
fronts, but please take them as a reminder that some kind of people are
still unsatisfied with some gcc features.

I'm using gcc for development of MICO (http://www.mico.org) and as I
already said for this project gcc 2.95.4 delivers twice the compilation
performance than gcc3.2.1. I'm talking about C++ compilation performance
here. While testing various gcc versions I can witness continuous
degradation of gcc compilation performance as Wolfgang already wrote.
Three weeks ago, I was a bit frustrated by trying to do development with
using gcc3.2.1 instead of gcc2.95.4 and this frustration leads me to
purchasing Comeau's C++ compiler and Dinkumware libstdc++ 4.0 (as both
companies claim, the only one full ISO C++ compliant solution). This was
just risk, since during that time I don't know if this compiler is not
even slower than gcc3.2.1. I've made some changes to the sources to use
PCH more effectivelly and build times looks (my minimal build
configuration for development):

gcc2.95.4          12min
gcc3.2.1           24min
como4.3.0.1        16min
como4.3.0.1+pch    11min

These are just build times of whole build. For simple development:
edit/compile/debug cycle, comeau's pch are very good. It's clear that as
soon as gcc's pch-branch will be able to compile MICO, I'll give it a try
too.

Note that for development I usually switch off all performance
optimizations.

Note2: Even with MICO, I can claim that our simple benchmark runs faster
while compiled with gcc3.2.1 - so here gcc3.2.1 is doing very good job.
Times look:

gcc3.2.1       35s
gcc2.95.4      38s
comeau         1m50s

Note3: at the moment I'm doing all development with comeau's compiler and
testing with both gcc...and I'm waiting for faster gcc compiler.

Thanks for all your great job,

Cheers,

Karel
PS: Since Comeau is translating C++ into C, I'm using gcc2.95.4 as a C
backend.
--
Karel Gardas                  kgardas@objectsecurity.com
ObjectSecurity Ltd.           http://www.objectsecurity.com