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Arthur Hagen <art@broomstick.com> wrote:
> Martin Vaeth <vaeth@mathematik.uni-wuerzburg.de> wrote:
>>
>> But I doubt that you get all package compiled with gcc-4.3 which is
>> meanwhile almost the case with gentoo...
>
> But since gentoo is source based, just /why/ would one want to compile
> everything with gcc-4.3? The erroneous belief that higher version numbers
> are always better?

Sooner or later, everybody will switch to gcc-4.3 anyway,
and it is better to not use mixed libraries on one system.
So better get rid of gcc-4.2.1 ASAP.
Personally, I wanted to test my projects with gcc-4.3 anyway and,
moreover, I wanted to recompile anyway, in order to push
-fstack-protector and -D_FORTIFY_SOURCE=2 in some apps where it was
yet missing and to add -Wl,-z,relro (about which I learnt only recently;
of course, I use throughout -Wl,-z,now anyway where possible).

> It also means that most hand-crafted optimisations are gone.

On most modern CPUs, it is really very hard to say what is a good
optimisation: What might be good for one CPU might be close to the
worst case for a slightly different model; one false branch prediction
can be worse than any cumbersome considerations.
E.g. 90% of the information which I heard about the effect of
various -f... flags were plain wrong with my CPU, although I have no
doubt they were correct for others.

> Speedwise, if you look at actual performance benchmarks instead of
> listening to anecdotal evidence ("my system seems faster")

For the above reason, I don't trust any benchmarks that I haven't faked.

> It was not made to produce faster or smaller binaries, and in some
> cases it sure doesn't.

In theory that's true, because most optimisations are a two-edged sword.
However, most users speak about a slight general speed increase of some
percent. I experienced nothing which is slower, and some things really
feel faster, but I made no benchmarks and did not use all new compiled
applications yet. So probably the about 5% general improvement which I
read at several places is correct (as a rule of thumb).
Of course, just for speed reasons this would not be worth all the
trouble.