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Re: alias time explosion


On Tue, 2006-03-21 at 17:30 -0500, Andrew MacLeod wrote:
> On Tue, 2006-03-21 at 10:10 +0100, Richard Guenther wrote:
> > On 3/21/06, Andrew MacLeod <amacleod@redhat.com> wrote:
> > > On Mon, 2006-03-20 at 18:55 -0500, Andrew Pinski wrote:
> > > > On Mar 20, 2006, at 5:18 PM, Andrew MacLeod wrote:
> > > 
> > > It looks like sometime between 10/30 and 01/23 alias analysis got out of
> > > hand. Odd it hasn't been noted before.
> > 
> > Can you do a comparison to 4.1.0 and file a PR with the testcase please?
> 
> I will do so in a day or so when I get a chance. until then:
> 
> 
> 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.




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