This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: Precompiled headers
- From: Mike Stump <mrs at apple dot com>
- To: Robert Vazan <robertvazan at privateweb dot sk>
- Cc: gcc at gcc dot gnu dot org
- Date: Mon, 3 Nov 2003 12:14:09 -0800
- Subject: Re: Precompiled headers
On Sunday, November 2, 2003, at 02:20 AM, Robert Vazan wrote:
It is rumoured to give six times faster compilations. Improvement from
12 to 2 minutes is not enough for me, not to mention that simplified
header structure means 2-3 times more
recompiling. I need it under one second.
12 minutes to 1 second isn't on the horizon. If you want that this
year, you will either have to work very hard or go someplace else. If
you want to work on it, the compile server is a natural fit. The
approach you cite is a very natural fit for it. Currently, if you go
from 12 to 2, you might make 1 minute with the compile server. On
changes that invalidate most coarse gained dependency checks but
preserve the fine gain checks, you should be able to get additional
speed ups with some work. I'd love to see this case benchmarked, I'd
guess that an additional 4-10x (over PCH) might be possible, but even
at 10x, that'd only be 6 seconds, and only in an odd sort of case.
I have code in there now for C++ at least that for code that doesn't
change, can consume and spit it out very fast the second time
(dependency check plus fprintf speeds). It uses fine grain dependency
checking and will redo just the parts that have changed or failed the
dependency check.