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Re: intermodule optimisation patch
- From: Geoffrey Keating <geoffk at apple dot com>
- To: Neil Booth <neil at daikokuya dot co dot uk>
- Cc: Geoffrey Keating <gkeating at apple dot com>, gcc-patches at gcc dot gnu dot org
- Date: Mon, 19 May 2003 13:02:36 -0700
- Subject: Re: intermodule optimisation patch
On Monday, May 19, 2003, at 12:53 PM, Neil Booth wrote:
Geoffrey Keating wrote:-
The attached patch allows GCC to perform optimisations between
modules. It works by allowing GCC to compile more than one file in
one invocation of the backend, and by setting up appropriate links
between the trees so that information about one file is available
while generating code for routines from another.
What effect does it have on bootstrap time?
If you don't use the new functionality, none to speak of (other than
the impact of the extra code to be compiled, of course). You can see
that when only one file is built, much of the new code doesn't get run.
I'm not exactly sure what happens if you *do* try to use the new
functionality. Factors to consider are:
1. Lots more memory use
2. Reduced total GCC startup time
3. The time required by any extra optimisations you use
4. Less efficient use of multiple processors.
I suspect it's somewhat slower, but haven't really tried.
Geoff Keating <email@example.com>