Re: poor gcc-4.0 performance
On Thu, Jun 16, 2005 at 02:47:45PM +0200, Thomas Steffen wrote:
> Maybe someone knows the precise reason, where I can only report
> hear-say. I had read that the developers only claim that gcc 4 has a
> lot of potential for better performance, but it may not have been
> realised yet. And I have seen benchmarks that report a drop in
> performance on AMD64 (whereas there seems to be a slight increase for
> x86).
>
> I have to admin that the difference you experience is rather big, and
> I cannot explain the size. Maybe gcc 4.1 will be better.
I thought the idea in gcc 4.x was to have a nice new optimization tree
system to make it easier to add new optimization systems. I would be
surprised if they have implemented very many optimizations in it yet
other than just getting the framework in place. I don't even know if
all the old optimization systems have been ported to the new
architecture and even if they have, some may not fit in to it very well
yet.
On the other hand I did read somewhere that g++ 4.0 runs MUCH faster
than g++ 3.x although it doesn't quite generate as fast code yet. The
compile time is much better though.
I expect to see great improvements over the next while as people start
to add optimization ideas to gcc 4.x without having to fiddle with all
the code the way it seemed to require doing in 3.x and older.
Len Sorensen
Reply to: