FACTS instead of FUD about gcc3
j.h.veenstra at stud.tue.nl
Wed May 8 09:29:50 PDT 2002
Ian Molton wrote:
> On Wed, 8 May 2002 16:41:59 +0200
> Matthias Benkmann <matthias at winterdrache.de> wrote:
>> After reading a 2nd-hand account about GCC3's 20% performance
>> regression I thought you might be interested in the actual facts.
> Er. theres nothing below I didnt mention.
> And bear in mind that aside from media processing, 90% or more
> operations are integer based.
> Its great that the problem can be worked around, but we shouldnt use
> something until the problems are FIXED, or we should provide patches
> for all the regressions it causes in other packages (unrealistic).
As it turns out, the performance regression had nothing to do with
integer based operations, it was all about not-inlining memset() from
M. Lespinasse: "OK, so I worked more to find the cause of the
slowdown, and I figured out its all because of memset(). This
function seems to be about twice slower than in 2.95"
Without this inlining problem:
M. Lespinasse: "now that I've worked around the two issues I had with
inlining and with memset, the 3.1 snapshot does provide superior
performance on my libmpeg2 codebase"
J. Hubicka: "I will send a patch"
All this happened around the 24th of April, so you can expect it to
be in CVS for some time now.
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