"Dependent on" ??? [LWN.net]

"Dependent on" ???

Posted Feb 28, 2007 22:13 UTC (Wed) by massimiliano (subscriber, #3048)
In reply to: "Dependent on" ??? by k8to
Parent article: Mitchell Baker and the Firefox Paradox (Inc)

Want to do a big favor to the gcc developers?

Profile those applications, and find the hot spots that get significantly worse. Then, write small benchmarks with the same code, and test them to see that the slowdown is still there.

Finally, open the bug with the small benchmarks :-)

And if you do it, remember to send the samples to me as well (massi(at)ximan"dot"com)! I work on the Mono JIT, and am generally interested in performance tests...

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"Dependent on" ???

Posted Mar 1, 2007 12:09 UTC (Thu) by k8to (subscriber, #15413) [Link]

Off the top, the n-queens "benchmark" shows a significant drop from 3.x to 4.x. http://www.arch.cs.titech.ac.jp/~kise/nq/index.htm

A larger one I care more about is UAE, the amiga emulator, without JIT. Both mainline and E-UAE from rcdrummond.net

"Dependent on" ???

Posted Mar 9, 2007 19:49 UTC (Fri) by anton (guest, #25547) [Link]

Want to do a big favor to the gcc developers?
Profile those applications, and find the hot spots that get significantly worse. Then, write small benchmarks with the same code, and test them to see that the slowdown is still there.
Finally, open the bug with the small benchmarks :-)

And see it closed as invalid after an hour (less time than it took to do create the bug report).

Given this reaction, I don't think the gcc developers consider such bug reports as favors, and it certainly has not inspired me to report other gcc bugs.

"Dependent on" ???

Posted Mar 9, 2007 20:52 UTC (Fri) by massimiliano (subscriber, #3048) [Link]

And see it closed as invalid after an hour (less time than it took to do create the bug report).

Interesting discussion in that bug :-)

Anyway, I wrote my suggestion without knowing how gcc development actually works... I would welcome bugs like that opened for the Mono JIT!
At worst, I would mark it as "Wishlist", and keep it open that way...

"Dependent on" ???

Posted Mar 10, 2007 1:42 UTC (Sat) by nix (subscriber, #2304) [Link]

It seems that fixing this would be ridiculously difficult and not terribly
beneficial (how many programs have you seen that use computed goto? How
much effort is it worth going to to speed it up?)

I'd have kept it open, too, but there is so much low-hanging optimization
fruit in GCC that fixing fairly small one-platform optimization bugs in
rarely-used language extensions isn't going to get much attention at the
best of times.

GCC development actually works in much the same way everything else works
in the free software community: if you have a performance bug in a tiny
obscure feature it's probably not going to get fixed unless you fix it. A
noninvasive patch would probably have made it...

"Dependent on" ???

Posted Apr 7, 2007 20:29 UTC (Sat) by anton (guest, #25547) [Link]

>how many programs have you seen that use computed goto? How
>much effort is it worth going to to speed it up?

Many interpreters are using labels-as-values for a significant
speedup. And a huge number of programs use interpreters.

>one-platform optimization bugs

As far as I understand the reply to the bug report, this bug affects
every platform that does not have a conditional indirect branch, i.e.,
pretty much every platform except PPC and IA64.

>A noninvasive patch would probably have made it...

They consider the bug "invalid", so they probably would not have
accepted the patch, and I am glad that I did not waste my time on
trying to build one.