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Re: C++ compile-time regressions (was: GCC 3.0.1 Status Report)
- To: Loren James Rittle <rittle at latour dot rsch dot comm dot mot dot com>
- Subject: Re: C++ compile-time regressions (was: GCC 3.0.1 Status Report)
- From: Gerald Pfeifer <pfeifer at dbai dot tuwien dot ac dot at>
- Date: Mon, 23 Jul 2001 14:17:23 +0200 (CEST)
- cc: <gcc at gcc dot gnu dot org>
On Fri, 20 Jul 2001, Loren James Rittle wrote:
> From what I understand, the above data is for the build of an entire
> program and not just one source translation. Is that correct, Gerald?
Yes.
> [This issue was studied a bit before the 3.0 release, see
> http://gcc.gnu.org/ml/libstdc++/2001-02/msg00365.html and followup.]
> [...]
> I conclude that in terms of header declaration processing, g++ 3.0 is
> slower than g++ 2.95.3 by a factor of 1.6 (4.3/2.7) to 2.1 (9.1/4.2).
> When one considers that the standard headers are now bigger (much
> bigger, in some common cases), it appears slower by a larger factor
> when comparing compilation speed of user-provided code.
Very interesting; thanks!
> I am the only one that finds it odd that -O0 takes longer to compile
> than -O1, -O2 and -O3 under 2.95.3?
Having rerun the tests in the meantime to analyse this particular strange
data point, it seems that the timing for -O0 using GCC 2.95.3 indeed must
have been skewed by some external influences; I now obtained timings also
for -O0 along the lines you'd expect.
Gerald
--
Gerald "Jerry" pfeifer@dbai.tuwien.ac.at http://www.dbai.tuwien.ac.at/~pfeifer/