On Wed, Apr 13, 2011 at 12:38 PM, Richard Guenther <richard.guent...@gmail.com> wrote: > On Wed, Apr 13, 2011 at 11:42 AM, Paul Richard Thomas > <paul.richard.tho...@gmail.com> wrote: >> Dear Dominique, >> >>> I think it is the automatic array in the subroutine trisolve. Note that the >>> speedup is rather 27->19s and may be darwin specific (slow malloc). >> >> I saw a speed-up of similar order on FC9/x86_64. >> >> I strongly doubt that it is anything to do with the automatic array - >> if it is there is an error somewhere, since none of the references to >> trisolve need copy-in/copy-out. >> >>> >>> Note also that -fstack-arrays prevents some optimizations on >>> fatigue: 4.7->7s. This may be related to pr45810. >> >> Has PR45810 converged now? If I have understood properly, a patch has >> been devised that cures the problem and does not cause slow-downs >> anywhere else? > > VLAs and malloc based arrays may behave differently with respect to alias > analysis (I'd have to look at some examples). All effects other than malloc > overhead I would attribute to that. That said, the general idea of the patch > is sound and I see nothing wrong with it. Both performance improvements > and regressions are worth looking at - they hint at possible improvements > in the middle-end parts of the compiler.
I have opened PR48590 for at least one issue that I see. It has a very simple patch which you might want to try ... Richard.