On 11/17/2017 01:49 AM, Hongbin Zheng wrote:> Could you elaborate "Note that, without further analysis of the uses > of the potentially-noalias pointers, you can do this only ..."? > Why the uses, instead of the def, of pointer matter?Both matter. static int foo(int *a, int *b) { return a[0] + b[1]; } int bar(int *x) { return foo(x+1, x); } You can't mark a and b as noalias here, even though NoAlias(x+1, x) == true. This is why I was saying that, unless the pointers come from distinct, identified underlying objects, you need to look at the uses of the pointers too. -Hal P.S. As discussed in D4609, we probably want to try adding CGSCC AA wrappers, to look back through function arguments, instead of using attribute propagation.> > Thanks > Hongbin > > On Thu, Nov 16, 2017 at 11:21 PM, Hal Finkel via llvm-dev > <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote: > > Hi, Alexandre, > > We don't have anything currently which does this. Note that, > without further analysis of the uses of the potentially-noalias > pointers, you can do this only for arguments with distinct (and > identified) underlying objects (i.e., you need something a bit > stronger than just "non-aliasing pointers"). > > -Hal > > > On 11/16/2017 10:11 AM, via llvm-dev wrote: > > Is this what you are looking for? > > https://reviews.llvm.org/D4609 > > Best, > > Haicheng Wu > > On 2017-11-14 20:34, Alexandre Isoard via llvm-dev wrote: > > Hello, > > Do we have a pass that propagate the noalias annotation > down to the > callee when: > - it is static > - it is always called with non aliasing pointers > ? > > Or maybe that is incorrect? > > -- > > ALEXANDRE ISOARD > > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev > <http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev> > > > -- > Hal Finkel > Lead, Compiler Technology and Programming Languages > Leadership Computing Facility > Argonne National Laboratory > > > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev > <http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev> > >-- Hal Finkel Lead, Compiler Technology and Programming Languages Leadership Computing Facility Argonne National Laboratory -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20171117/0226b3c0/attachment.html>
Hongbin Zheng via llvm-dev
2017-Nov-17 08:01 UTC
[llvm-dev] Propagating noalias annotation
Do you mean a and b are noalias if:
static int foo(int *a, int *b) {
return a[0] + b[0];
}
int bar(int *x) {
return foo(x+1, x);
}
?
To me, because "AA.alias((x+1, MemoryLocation::UnknownSize),
(x, MemoryLocation::UnknownSize)) != NoAlias", so a and b are not noalias.
Maybe my version is too conservative.
Thanks
Hongbin
On Thu, Nov 16, 2017 at 11:55 PM, Hal Finkel <hfinkel at anl.gov> wrote:
>
> On 11/17/2017 01:49 AM, Hongbin Zheng wrote:
>
> Could you elaborate "Note that, without further analysis of the uses
of
> the potentially-noalias pointers, you can do this only ..."?
> Why the uses, instead of the def, of pointer matter?
>
>
> Both matter.
>
> static int foo(int *a, int *b) {
> return a[0] + b[1];
> }
>
> int bar(int *x) {
> return foo(x+1, x);
> }
>
> You can't mark a and b as noalias here, even though NoAlias(x+1, x)
=> true. This is why I was saying that, unless the pointers come from
> distinct, identified underlying objects, you need to look at the uses of
> the pointers too.
>
> -Hal
>
> P.S. As discussed in D4609, we probably want to try adding CGSCC AA
> wrappers, to look back through function arguments, instead of using
> attribute propagation.
>
>
>
> Thanks
> Hongbin
>
> On Thu, Nov 16, 2017 at 11:21 PM, Hal Finkel via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi, Alexandre,
>>
>> We don't have anything currently which does this. Note that,
without
>> further analysis of the uses of the potentially-noalias pointers, you
can
>> do this only for arguments with distinct (and identified) underlying
>> objects (i.e., you need something a bit stronger than just
"non-aliasing
>> pointers").
>>
>> -Hal
>>
>>
>> On 11/16/2017 10:11 AM, via llvm-dev wrote:
>>
>>> Is this what you are looking for?
>>>
>>> https://reviews.llvm.org/D4609
>>>
>>> Best,
>>>
>>> Haicheng Wu
>>>
>>> On 2017-11-14 20:34, Alexandre Isoard via llvm-dev wrote:
>>>
>>>> Hello,
>>>>
>>>> Do we have a pass that propagate the noalias annotation down to
the
>>>> callee when:
>>>> - it is static
>>>> - it is always called with non aliasing pointers
>>>> ?
>>>>
>>>> Or maybe that is incorrect?
>>>>
>>>> --
>>>>
>>>> ALEXANDRE ISOARD
>>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>
>> --
>> Hal Finkel
>> Lead, Compiler Technology and Programming Languages
>> Leadership Computing Facility
>> Argonne National Laboratory
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
>
> --
> Hal Finkel
> Lead, Compiler Technology and Programming Languages
> Leadership Computing Facility
> Argonne National Laboratory
>
>
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Hongbin Zheng via llvm-dev
2017-Nov-17 08:05 UTC
[llvm-dev] Propagating noalias annotation
On Thu, Nov 16, 2017 at 11:55 PM, Hal Finkel <hfinkel at anl.gov> wrote:> > On 11/17/2017 01:49 AM, Hongbin Zheng wrote: > > Could you elaborate "Note that, without further analysis of the uses of > the potentially-noalias pointers, you can do this only ..."? > Why the uses, instead of the def, of pointer matter? > > > Both matter. > > static int foo(int *a, int *b) { > return a[0] + b[1]; > } > > int bar(int *x) { > return foo(x+1, x); > } > > You can't mark a and b as noalias here, even though NoAlias(x+1, x) => true. This is why I was saying that, unless the pointers come from > distinct, identified underlying objects, you need to look at the uses of > the pointers too. > > -Hal > > P.S. As discussed in D4609, we probably want to try adding CGSCC AA > wrappers, to look back through function arguments, instead of using > attribute propagation. >Also, is CFLSteensAA able to help D4609? Thanks Hongbin> > > > Thanks > Hongbin > > On Thu, Nov 16, 2017 at 11:21 PM, Hal Finkel via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > >> Hi, Alexandre, >> >> We don't have anything currently which does this. Note that, without >> further analysis of the uses of the potentially-noalias pointers, you can >> do this only for arguments with distinct (and identified) underlying >> objects (i.e., you need something a bit stronger than just "non-aliasing >> pointers"). >> >> -Hal >> >> >> On 11/16/2017 10:11 AM, via llvm-dev wrote: >> >>> Is this what you are looking for? >>> >>> https://reviews.llvm.org/D4609 >>> >>> Best, >>> >>> Haicheng Wu >>> >>> On 2017-11-14 20:34, Alexandre Isoard via llvm-dev wrote: >>> >>>> Hello, >>>> >>>> Do we have a pass that propagate the noalias annotation down to the >>>> callee when: >>>> - it is static >>>> - it is always called with non aliasing pointers >>>> ? >>>> >>>> Or maybe that is incorrect? >>>> >>>> -- >>>> >>>> ALEXANDRE ISOARD >>>> >>> _______________________________________________ >>> LLVM Developers mailing list >>> llvm-dev at lists.llvm.org >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >>> >> >> -- >> Hal Finkel >> Lead, Compiler Technology and Programming Languages >> Leadership Computing Facility >> Argonne National Laboratory >> >> >> _______________________________________________ >> LLVM Developers mailing list >> llvm-dev at lists.llvm.org >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >> > > > -- > Hal Finkel > Lead, Compiler Technology and Programming Languages > Leadership Computing Facility > Argonne National Laboratory > >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20171117/6acff414/attachment.html>
On 11/17/2017 02:01 AM, Hongbin Zheng wrote:> Do you mean a and b are noalias if: > > static int foo(int *a, int *b) { > return a[0] + b[0]; > } > > int bar(int *x) { > return foo(x+1, x); > } > > ? > > To me, because "AA.alias((x+1, MemoryLocation::UnknownSize), > (x, MemoryLocation::UnknownSize)) != NoAlias", so a and b are not noalias.Remember that MemoryLocation::UnknownSize is unknown, but positive. So you need to check both "AA.alias((x+1, MemoryLocation::UnknownSize), (x, MemoryLocation::UnknownSize)) == NoAlias" and "AA.alias((x, MemoryLocation::UnknownSize), (x+1, MemoryLocation::UnknownSize)) == NoAlias" to partition by underlying object. One of these should be false. -Hal> Maybe my version is too conservative. > > Thanks > Hongbin > > > On Thu, Nov 16, 2017 at 11:55 PM, Hal Finkel <hfinkel at anl.gov > <mailto:hfinkel at anl.gov>> wrote: > > > On 11/17/2017 01:49 AM, Hongbin Zheng wrote: >> Could you elaborate "Note that, without further analysis of the >> uses of the potentially-noalias pointers, you can do this only ..."? >> Why the uses, instead of the def, of pointer matter? > > Both matter. > > static int foo(int *a, int *b) { > return a[0] + b[1]; > } > > int bar(int *x) { > return foo(x+1, x); > } > > You can't mark a and b as noalias here, even though NoAlias(x+1, > x) == true. This is why I was saying that, unless the pointers > come from distinct, identified underlying objects, you need to > look at the uses of the pointers too. > > -Hal > > P.S. As discussed in D4609, we probably want to try adding CGSCC > AA wrappers, to look back through function arguments, instead of > using attribute propagation. > > >> >> Thanks >> Hongbin >> >> On Thu, Nov 16, 2017 at 11:21 PM, Hal Finkel via llvm-dev >> <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote: >> >> Hi, Alexandre, >> >> We don't have anything currently which does this. Note that, >> without further analysis of the uses of the >> potentially-noalias pointers, you can do this only for >> arguments with distinct (and identified) underlying objects >> (i.e., you need something a bit stronger than just >> "non-aliasing pointers"). >> >> -Hal >> >> >> On 11/16/2017 10:11 AM, via llvm-dev wrote: >> >> Is this what you are looking for? >> >> https://reviews.llvm.org/D4609 >> >> Best, >> >> Haicheng Wu >> >> On 2017-11-14 20:34, Alexandre Isoard via llvm-dev wrote: >> >> Hello, >> >> Do we have a pass that propagate the noalias >> annotation down to the >> callee when: >> - it is static >> - it is always called with non aliasing pointers >> ? >> >> Or maybe that is incorrect? >> >> -- >> >> ALEXANDRE ISOARD >> >> _______________________________________________ >> LLVM Developers mailing list >> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org> >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >> <http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev> >> >> >> -- >> Hal Finkel >> Lead, Compiler Technology and Programming Languages >> Leadership Computing Facility >> Argonne National Laboratory >> >> >> _______________________________________________ >> LLVM Developers mailing list >> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org> >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >> <http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev> >> >> > > -- > Hal Finkel > Lead, Compiler Technology and Programming Languages > Leadership Computing Facility > Argonne National Laboratory > >-- Hal Finkel Lead, Compiler Technology and Programming Languages Leadership Computing Facility Argonne National Laboratory -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20171117/1c95a6a1/attachment.html>