Re: [patch 00/2] improve .text size on gcc 4.0 and newer compilers

Arjan van de Ven
2005-12-28T21:17:10Z

On Wed, 2005-12-28 at 13:02 -0800, Linus Torvalds wrote:
>
> On Wed, 28 Dec 2005, Arjan van de Ven wrote:
> >
> > yup that's why the patch only does it for gcc4, in which the inlining
> > heuristics finally got rewritten to something that seems to resemble
> > sanity...
>
> Is that actually true of all gcc4 versions? I seem to remember gcc-4.0
> being a real stinker.

it is... if you disable unit-at-a-time for sure.
But I'm not entirely sure when this got in, if it was 4.0 or 4.1

> > (unit-at-a-time allows gcc to look at the entire .c file, eg things like
> > number of callers etc etc, disabling that tells gcc to do the .c file as
> > single pass top-to-bottom only)
>
> I'd still prefer to see numbers with -funit-at-a-time only. I think it's
> an independent knob, and I'd be much less worried about that, because we
> do know that unit-at-a-time has been enabled on x86-64 for a long time
> ("forever"). So that's less of a change, I feel.

the only effect I expect is more inlining actually, since we on the one
hand tie gcc's hands via the forced inline, and one the other hand now
give it more room to inline more. But yeah it's worth to look at for
sure, even if it is to see it's getting bigger ;)