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gcc-4.0.0-prerelease: -O0 build time higher than -O1?
- From: Rene Rebe <rene at exactcode dot de>
- To: gcc at gnu dot org
- Cc: t2 developers mailing list <t2 at exactcode dot de>
- Date: Thu, 24 Mar 2005 00:57:12 +0100
- Subject: gcc-4.0.0-prerelease: -O0 build time higher than -O1?
- Organization: ExactCode
Hi all,
I'm just doing the first benchmarking with the 4.0.0 pre release
(20050319) and just noticed that -O0 build time is not always the
fastest. (In contrast to what the changes suggest: "When compiling
without optimizations (-O0), the C++ frontend is much faster than in any
previous versions of GCC. ..." - Or is it just that previous versions
have already been way slower ...)
One of the tests is Richard Guenther's tramp3d and the -O0 build time is
_significantly_ higher than with -O1: (user + system)
CXX used: g++ (4.0.0) -O0 -march=i386
tramp3d-v3
Building ... 63.85 + 2.02
Running ... 76.71 + 0.11
CXX used: g++ (4.0.0) -O1 -march=i386
tramp3d-v3
Building ... 49.62 + 0.98
Running ... 12.82 + 0.11
CXX used: g++ (4.0.0) -O2 -march=i386
tramp3d-v3
Building ... 66.33 + 1.05
Running ... 13.55 + 0.12
Most probably due to -O1 eliminates much more of the template stuff and
needs to generate far less code?
Currently my athlon is busy crunching all the optimization permutations
I want to get numbers for - and then 3.4.3 results are build up for
comparision ... I hope to have a full set available tomorrow ...
Yours,
--
René Rebe - Rubensstr. 64 - 12157 Berlin (Europe / Germany)
http://www.exactcode.de/ | http://www.t2-project.org/
+49 (0)30 255 897 45