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Re: Precompiled headers (or other speed ups)
- To: dewar at gnat dot com
- Subject: Re: Precompiled headers (or other speed ups)
- From: Andi Kleen <ak at suse dot de>
- Date: 10 Jan 2001 14:29:03 +0100
- Cc: gcc at gcc dot gnu dot org, shebs at apple dot com
- References: <20010109225504.7663A34D87@nile.gnat.com>
dewar@gnat.com writes:
>
> Of course the speeds that Stan is reporting are horribly slow in absolute
> terms. The real question is *why* slo slow. 150K lines of decls
> to be crunched should not be taking anywhere NEAR that long, since it
> is not necessary to generate full code for these decls, or at least
> should not be.
In my experience g++ is much slower than the gcc C compiler, even without
excessive include files -- the include heavy style common for C++ makes
things just worse. The difference is visible when you just watch Makefile
runs.
I don't know why that's the case, but I suspect all the operator overloading
resolving and handling of the non regular C++ grammar etc. has a cost over C.
[It actually quite surprised me, I always assumed that the backend would
dominate compile cost]
I guess it would be useful if Stan could post a few a profile logs of
g++ compiling PowerPlant code, just to see where the hot spots are.
-Andi