Messages in this thread | | | From | Segher Boessenkool <> | Subject | Re: kernel + gcc 4.1 = several problems | Date | Sat, 6 Jan 2007 09:23:01 +0100 |
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>> For a different mailing list indeed; let me just point >> out >> that for certain important quite common cases it's an >> ~50% >> overall speedup. > > Hmm, what code was that? 'signed int does not wrap around' does not > seem to provide _that_ much info...
One of the recent huge threads on the GCC dev list has a post that says *some other* compiler gets a result like this from this optimisation (I don't have a link to the exact post and I don't remember the details; perhaps it was XLC?)
Sorry if I wasn't clear enough and you understood I meant that GCC exploits this optimisation opportunity well enough for such nice results already.
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So I searched for it anyway:
<http://gcc.gnu.org/ml/gcc/2006-12/msg00768.html>
It looks like the result for *integer* code wasn't *all* that dramatic a difference. Anyway, it's obvious that the optimisation can certainly give nice results and it wouldn't be a good idea for the Linux kernel to dismiss it without really evaluating the impact first; and anyway, this is for some future date, GCC-4.2 isn't here yet.
Segher
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