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Re: alias time explosion
On 3/21/06, Daniel Berlin <dberlin@dberlin.org> wrote:
> On Tue, 2006-03-21 at 17:30 -0500, Andrew MacLeod wrote:
> >
> > I seem to have narrowed it down to this patch:
> >
> > http://gcc.gnu.org/ml/gcc-patches/2006-01/msg00908.html
> >
>
> That's quite a while ago :).
>
> >
> >
> > Dan, this appear to *not* be compile time neutral:
> >
> > Timings on this patch show that it is not faster or slower than
> > what we
> > do now (even with the removal of the call clobbering patch). This is
> > true even on fortran tests i had that clobber a lot of stuff.
>
> >
> >
> > running cpgram.ii shows a regression:
> >
> > before patch:
> >
> > tree alias analysis : 2.49 ( 7%) usr 0.25 ( 5%) sys 6.13 ( 5%) wall 4971 kB ( 1%) ggc
> > TOTAL : 36.90 4.72 130.34 467341 kB
> >
> > after patch:
> >
> > tree alias analysis : 59.00 (63%) usr 0.40 ( 7%) sys 70.43 (36%) wall 4957 kB ( 1%) ggc
> > TOTAL : 94.13 5.43 193.85 468339 kB
> >
>
> > on a 386 linux machine bootstrapped with checking disabled.
>
> Can you send me cpgram.ii, so i can look into it?
>
> i will note the patch is pretty much required for correctness. We were
> getting seriously wrong answers before in some cases.
Maybe someone can have a look at the attribute((pointer_no_escape))
patch I posted a while ago. With some IPA machinery we could possibly
trim down the clobber lists quite a bit.
Richard.