C compile time

[Jan Hubicka]

> Hello,
> 
> I've now updated results at
> http://www.myownlittleworld.com/computers/gcctable.html
> to include a table of the percentage change for
> compile time between the various compilers.
> 
> Some things which stick out:
> 
> 1) Andrew Pinski's patch gets us back on average about
> 10% on mainline and 7.5% on branch. Hopefully his
> copyright assignment arrives soon!
> 
> 2) Kaveh's work the garbage collection algorithm means
> that gcc 3.3 is the first major gcc release since egcs
> 1.0.3a that's not more than 5% slower than the last
> major release on the preceding branch. gcc 3.2.3 for
> instance is between 14% and 42% slower than gcc 3.0.4
> depending on optimizations.
> 
> 3) The biggest slowdown to gcc was between gcc 3.0.X
> and 3.1.X (ie different branches), but between 3.1.1
> and 3.2.3, there was quite a slowdown too, ~6-9%. I
> didn't realize that such big changes occurred on
> release branches.
> 
> 4) -funit-at-a-time is expensive!

Can you please try -O2 -funit-at-a-time?  That way we see how much of
overhead comes from -funit-at-a-time itself and inlining functions
called once and how much from the inlining heuristics.
I will try to prepare patch limiting function body for inlining once
soon.

Honza