GCC 3.3 compile speed regression - AN ANSWER

[Jan Hubicka]

> > 
> > And this will slow things down. There's no question about it. At dubious
> > gain - because you _can_ plot a line where gcc is getting slower and
> > slower to compile over the last few years, but you can _not_ plot a 
> > line which shows the resulting improvement in resultant code quality.

You can take a look at http://www.suse.de/~aj/SPEC.  It plots such
lines.  For SPECint score at -O2, 2.95 did 369, current GCC does 398 and
with profile feedback 2.95 didn't supported 410.  This is about 11%
speedup. (7.8% in apples-to-apples comparsion witout profile feedback)

The compiler speed is tracked only since Jun 2002 and since that it
degraded from 500 seconds to 649 seconds.  29%.  I agree that this is a
lot.  Over half of it is the slowdown in compilation of the single C++
benchmark EON that went up from roughtly 220 to 300 seconds, but it also
accounts rougly half of the overall time...

The size has changed from 5.2 to 4.7MB since Jul 2001 when the graph
starts (10%).  This include debug info that changed from stabs to dwarf2
and got bigger and more exact over a time.

This is not complette image of the development, but I don't see the
trend of getting bigger and slower code in post-2.95 releases
(I agree that is has commonly been the case for eariler and partly for
3.0 as well).

In case you notice different results, can you give the examples?

Honza