Re: Suggestions for improving gcc 3.2 compilation speed?

[Geoff Keating <geoffk at geoffk dot org>]

Mike Stump <mrs at apple dot com> writes:

> On Friday, March 7, 2003, at 11:12 AM, Benjamin Kosnik wrote:
> >> I have a g++ compiler that is 5.6x faster than the current g++ when
> >> compiling large C++ code bases. That's when compared to a g++ PCH,
> >> without it, more like 8x to 16x faster when PCH isn't used.
> >
> > Your PCH numbers are interesting to me.
> >
> > I cannot get PCH to work with g++. How are you able to do this? Are you
> > generating individual .pch files for each header (don't see any
> > significant speed improvement), or are you using -include
> > big_globbed_header.h.pch (and if so, can you port the patches to do
> > this
> > to mainline g++, because it currently doesn't work), or is there
> > another
> > approach?
> 
> We use -include.  We generate one large application .gch file that
> include tons of things in it.
> 
> bash-2.05a$ wc MillenniumFE.ii
>    152201  333117 4298858 MillenniumFE.ii
> 
> That is the .ii file of the file that is -included.  This generates a
> 30-40 MB .gch file.  The application has 279 translation units in it.
> 
> I don't know offhand why it works for us and not you.  Random guess, I
> thought I saw something about TAKES_ARG go by recently in another
> context...  Found it, in cppspec.c Devang added
> DEFFAULT_WORD_TAKES_ARG, is this related to why -include doesn't work?

It could be that problem; we don't hit it because the prefix headers
in much of our source aren't named like *.h and the problem only
occurs if you do '-include xxx.h'.

-- 
- Geoffrey Keating <geoffk at geoffk dot org>