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SubjectGCC speed (was [PATCH] Isapnp warning)
Hi Andrew,

On Sunday 22 June 2003 04:17, you wrote:
> Compared to 2.95.3, gcc-3.3 takes 1.5x as long to compile, and produces a
> kernel which is 200k larger.
> It is simply worthless.

Recently, we did an unscientific but nonetheless informative tour through
various optimization and compiler version questions here:
[RFC][PATCH] Faster generic_fls

As a result, my general impression is GCC 3.2 (and, I presume, GCC 3.3 as
well) comes out better than 2.95.3 in terms of binary performance on x86. I
seem to recall there was one case in one algorithm variation on one procesor
type where 2.95.3 won marginally, and otherwise GCC 3.2 took the trophy every
time, sometimes by a significant margin. I was able to get satisfactory
performance in terms of size as well, by tweaking compile options. (In
general, just mindlessly setting O3 seems to work well.)

So I like GCC 3.2 in terms of code quality, at least for the limited set of
things I've tested, but that's not the only consideration. Current GCC is a
whole lot better in terms of C99 compliance and produces better warnings.

As for compilation speed, yes, that sucks. I doubt there's any rational
reason for it, but I also agree with the idea that correctness and binary
code performance should come first, then the compilation speed issue should
be addressed. I hope the gcc team does make it a priority at some point.
For my own part, I'm putting together a cluster to address the compilation
speed issue, i.e., I don't really care about it. Even a dual PIII turns in
satisfactory results in that regard, or a single K7.



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