On Sat, Dec 4, 2010 at 9:48 AM, Ravindran, Rajiv <ravind...@hp.com> wrote:
> Hi,
>
>
>
> Basically, it compares how precise we are w.r.t to alias classification. We
> measured the fraction of alias queries in BE for which we do not alias. As
> you can see, for C++ benchmarks we are not performing that well. There are
> several reasons for this -
>
> 1) Alias classification is done after inlining and since we aren’t
> context-sensitive yet we tend to be less precise.
>
OK, I understood that.
> 2) Alias classification is called multiple times in BE and therefore
> is more up-to-date. We do not have this luxury since solving the constraint
> graph is more expensive. Moreover to make it worse, there are still a number
> of cases (after VHO/PreOpt) where after the transformation we no longer have
> the WN to AliasTag (point-to sets) mapping, and we end up being
> conservative. This is something we are currently looking at.
>
What does the AliasTag look like? A global id or a bit-vector like set? I
may check your implementation
I think the SSA-based flow-sensitive alias analysis (or the base+offset+size
rule) did a quite well job, if we can compare its result with your new Alias
analysis result, that will be great. Although the field-sensitive alias
analysis only work at intra-procedural level, we still can add a hook in the
alias manager to see the effects that all existing alias facilities can not
distinguish while new alias analysis can.
> 3) We still have scalability issues in 483.xalancbmk. We have managed
> to address this by selectively “collapsing” objects – thus losing
> field-sensitivity. But more tuning is required.
>
Cool, that's great.
> 4) Moreover, I believe this provides a better infrastructure to
> accurately compute mod/ref sets as well as improve the precision on memory
> SSA which can hopefully lead to better performance. So far we are only
> seeing minor improvements as shown in the same slide. Fortunately, we aren’t
> degrading the performance J
>
>
>
Agree, I am looking forward to that. We may get more interesting results
based on your infrastructure.
>
>
> Thanks
>
> Rajiv
>
>
>
> *From:* Tianwei [mailto:tianwei.sh...@gmail.com]
> *Sent:* Friday, December 03, 2010 5:10 PM
> *To:* Ravindran, Rajiv
> *Cc:* open64-devel@lists.sourceforge.net
> *Subject:* Re: [Open64-devel] nextgen alias analysis review request
>
>
>
> Hi, Ravindran,
>
> Do you mind to explain a bit more for the page 18 of the slides?
> what's the two bar? and what's the performance result? If they are real
> running time improvement at IPA, since you can pass 483(especially with your
> field-sensitivity), that is really exciting.
>
>
>
> I will try to look at all your files later.
>
>
>
> Tianwei
>
> On Sat, Dec 4, 2010 at 5:51 AM, Ravindran, Rajiv <ravind...@hp.com> wrote:
>
> Hi folks,
>
>
>
> Attached is a high-level design document describing our implementation of a
> new alias analysis infrastructure in Open64. Also included is the
> presentation we made of the same at the recent developer’s forum. A patch
> containing the changes to the existing files is included in
> nextgenalias.diff, while the new files have been directly attached.
>
>
>
> We plan to initially check this in disabled. Any comments or suggestions is
> greatly appreciated.
>
>
>
> Thanks
>
> Rajiv
>
>
>
>
>
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>
>
> --
> Sheng, Tianwei
> Inst. of High Performance Computing
> Dept. of Computer Sci. & Tech.
> Tsinghua Univ.
>
--
Sheng, Tianwei
Inst. of High Performance Computing
Dept. of Computer Sci. & Tech.
Tsinghua Univ.
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