Hi all,
>>> if (a == b)
>>> ...
>>>
>>> # c = PHI
>>>
>>> where we'd lose eliding such a conditional. IMHO that's bad
>>> and very undesirable.
>> But if we only suppress this optimization for pointers is it that terrible?
>
> I've at least seen a lot of cases with c = PHI for null pointer
>
On Thu, 25 Apr 2019, Peter Sewell wrote:
> (The standard does also have a defect in its definition of equality - on
> the one hand, it says that &x+1==&y comparison must be true
> if they are adjacent, but on the other (in DR260) that everything
> might be provenance-aware. My preference would b
On 25/04/2019, Richard Biener wrote:
> On Thu, Apr 25, 2019 at 3:03 PM Peter Sewell
> wrote:
>>
>> On 25/04/2019, Richard Biener wrote:
>> > On Wed, Apr 24, 2019 at 11:18 PM Peter Sewell
>> >
>> > wrote:
>> >>
>> >> On 24/04/2019, Jeff Law wrote:
>> >> > On 4/24/19 4:19 AM, Richard Biener wrot
On Thu, Apr 25, 2019 at 3:03 PM Peter Sewell wrote:
>
> On 25/04/2019, Richard Biener wrote:
> > On Wed, Apr 24, 2019 at 11:18 PM Peter Sewell
> > wrote:
> >>
> >> On 24/04/2019, Jeff Law wrote:
> >> > On 4/24/19 4:19 AM, Richard Biener wrote:
> >> >> On Thu, Apr 18, 2019 at 3:42 PM Jeff Law w
On 25/04/2019, Richard Biener wrote:
> On Wed, Apr 24, 2019 at 11:18 PM Peter Sewell
> wrote:
>>
>> On 24/04/2019, Jeff Law wrote:
>> > On 4/24/19 4:19 AM, Richard Biener wrote:
>> >> On Thu, Apr 18, 2019 at 3:42 PM Jeff Law wrote:
>> >>>
>> >>> On 4/18/19 6:20 AM, Uecker, Martin wrote:
>>
On Wed, Apr 24, 2019 at 11:18 PM Peter Sewell wrote:
>
> On 24/04/2019, Jeff Law wrote:
> > On 4/24/19 4:19 AM, Richard Biener wrote:
> >> On Thu, Apr 18, 2019 at 3:42 PM Jeff Law wrote:
> >>>
> >>> On 4/18/19 6:20 AM, Uecker, Martin wrote:
> Am Donnerstag, den 18.04.2019, 11:45 +0100 schri
On Wed, Apr 24, 2019 at 8:41 PM Jeff Law wrote:
>
> On 4/24/19 4:19 AM, Richard Biener wrote:
> > On Thu, Apr 18, 2019 at 3:42 PM Jeff Law wrote:
> >>
> >> On 4/18/19 6:20 AM, Uecker, Martin wrote:
> >>> Am Donnerstag, den 18.04.2019, 11:45 +0100 schrieb Peter Sewell:
> On Thu, 18 Apr 2019 a
On 24/04/2019, Jeff Law wrote:
> On 4/24/19 4:19 AM, Richard Biener wrote:
>> On Thu, Apr 18, 2019 at 3:42 PM Jeff Law wrote:
>>>
>>> On 4/18/19 6:20 AM, Uecker, Martin wrote:
Am Donnerstag, den 18.04.2019, 11:45 +0100 schrieb Peter Sewell:
> On Thu, 18 Apr 2019 at 10:32, Richard Biener
Am Mittwoch, den 24.04.2019, 21:30 +0200 schrieb Philipp Klaus Krause:
> Am 24.04.19 um 20:41 schrieb Jeff Law:
> > > > > 4.) Compilers make sure that exposed objects never
> > > > > are allocated next to each other (as Jens proposed).
> > > >
> > > > Ugh. Not sure how you enforce that. Consider
On Wed, Apr 24, 2019 at 12:41:25PM -0600, Jeff Law wrote:
> >>> 4.) Compilers make sure that exposed objects never
> >>> are allocated next to each other (as Jens proposed).
> >> Ugh. Not sure how you enforce that. Consider that the compiler may
> >> ultimately have no control over layout of data
Am 24.04.19 um 20:41 schrieb Jeff Law:
4.) Compilers make sure that exposed objects never
are allocated next to each other (as Jens proposed).
>>> Ugh. Not sure how you enforce that. Consider that the compiler may
>>> ultimately have no control over layout of data in static storage.
>>
Am 24. April 2019 20:43:03 MESZ schrieb Jeff Law :
>On 4/24/19 4:24 AM, Richard Biener wrote:
>> On Fri, Apr 19, 2019 at 11:09 AM Jens Gustedt
>wrote:
>>>
>>> Hello Jakub,
>>>
>>> On Fri, 19 Apr 2019 10:49:08 +0200 Jakub Jelinek
>>> wrote:
>>>
On Fri, Apr 19, 2019 at 10:19:28AM +0200, Jens G
On 4/24/19 4:24 AM, Richard Biener wrote:
> On Fri, Apr 19, 2019 at 11:09 AM Jens Gustedt wrote:
>>
>> Hello Jakub,
>>
>> On Fri, 19 Apr 2019 10:49:08 +0200 Jakub Jelinek
>> wrote:
>>
>>> On Fri, Apr 19, 2019 at 10:19:28AM +0200, Jens Gustedt wrote:
> OTOH GCC transforms
> (uintptr_t)&a !
On 4/24/19 4:19 AM, Richard Biener wrote:
> On Thu, Apr 18, 2019 at 3:42 PM Jeff Law wrote:
>>
>> On 4/18/19 6:20 AM, Uecker, Martin wrote:
>>> Am Donnerstag, den 18.04.2019, 11:45 +0100 schrieb Peter Sewell:
On Thu, 18 Apr 2019 at 10:32, Richard Biener
wrote:
>>>
>>>
An equality
On Fri, Apr 19, 2019 at 11:09 AM Jens Gustedt wrote:
>
> Hello Jakub,
>
> On Fri, 19 Apr 2019 10:49:08 +0200 Jakub Jelinek
> wrote:
>
> > On Fri, Apr 19, 2019 at 10:19:28AM +0200, Jens Gustedt wrote:
> > > > OTOH GCC transforms
> > > > (uintptr_t)&a != (uintptr_t)(&b+1)
> > > > into &a != &b + 1
On Thu, Apr 18, 2019 at 3:42 PM Jeff Law wrote:
>
> On 4/18/19 6:20 AM, Uecker, Martin wrote:
> > Am Donnerstag, den 18.04.2019, 11:45 +0100 schrieb Peter Sewell:
> >> On Thu, 18 Apr 2019 at 10:32, Richard Biener
> >> wrote:
> >
> >
> >> An equality test of two pointers, on the other hand, doesn
On Thu, Apr 18, 2019 at 3:29 PM Jeff Law wrote:
>
> On 4/18/19 6:50 AM, Jakub Jelinek wrote:
> > On Thu, Apr 18, 2019 at 02:47:18PM +0200, Jakub Jelinek wrote:
> >> On Thu, Apr 18, 2019 at 02:42:22PM +0200, Richard Biener wrote:
> 1.) Compilers do not use conditional equivalences for
> o
Hello Jakub,
On Fri, 19 Apr 2019 11:34:33 +0200 Jakub Jelinek
wrote:
> On Fri, Apr 19, 2019 at 11:09:27AM +0200, Jens Gustedt wrote:
> > > similarly, if one of the
> > > pointers is &object or &object + sizeof (object).
> >
> > Here I don't follow. Why would one waste brain and ressources to
Am Freitag, den 19.04.2019, 10:35 +0100 schrieb Peter Sewell:
> On 19/04/2019, Jens Gustedt wrote:
> > Hello Peter,
> >
> > On Fri, 19 Apr 2019 10:11:43 +0100 Peter Sewell
> > wrote:
> >
> > > On 19/04/2019, Jakub Jelinek wrote:
> > > > On Fri, Apr 19, 2019 at 10:19:28AM +0200, Jens Gustedt wr
Am Freitag, den 19.04.2019, 10:19 +0200 schrieb Jens Gustedt:
> Hello,
>
> On Thu, 18 Apr 2019 14:42:22 +0200 Richard Biener
> wrote:
>
> > On Thu, Apr 18, 2019 at 2:20 PM Uecker, Martin
> > wrote:
> > > 1.) Compilers do not use conditional equivalences for
> > > optimizations of pointers (or o
On 19/04/2019, Jens Gustedt wrote:
> Hello Peter,
>
> On Fri, 19 Apr 2019 10:11:43 +0100 Peter Sewell
> wrote:
>
>> On 19/04/2019, Jakub Jelinek wrote:
>> > On Fri, Apr 19, 2019 at 10:19:28AM +0200, Jens Gustedt wrote:
>> [...]
>
>> > That penalizes quite a few optimizations though.
>> > If you
On Fri, Apr 19, 2019 at 11:09:27AM +0200, Jens Gustedt wrote:
> > similarly, if one of the
> > pointers is &object or &object + sizeof (object).
>
> Here I don't follow. Why would one waste brain and ressources to
> optimize code that does such tricks?
What tricks? A normal pointer comparison ei
Hello Peter,
On Fri, 19 Apr 2019 10:11:43 +0100 Peter Sewell
wrote:
> On 19/04/2019, Jakub Jelinek wrote:
> > On Fri, Apr 19, 2019 at 10:19:28AM +0200, Jens Gustedt wrote:
> [...]
> > That penalizes quite a few optimizations though.
> > If you have
> > ptr != ptr2
> > and points-to analys
On 19/04/2019, Jakub Jelinek wrote:
> On Fri, Apr 19, 2019 at 10:19:28AM +0200, Jens Gustedt wrote:
>> > OTOH GCC transforms
>> > (uintptr_t)&a != (uintptr_t)(&b+1)
>> > into &a != &b + 1 (for equality compares) and then
>> > doesn't follow this C rule anyways.
>>
>> Actually our proposal we are d
Hello Jakub,
On Fri, 19 Apr 2019 10:49:08 +0200 Jakub Jelinek
wrote:
> On Fri, Apr 19, 2019 at 10:19:28AM +0200, Jens Gustedt wrote:
> > > OTOH GCC transforms
> > > (uintptr_t)&a != (uintptr_t)(&b+1)
> > > into &a != &b + 1 (for equality compares) and then
> > > doesn't follow this C rule anyway
On Fri, Apr 19, 2019 at 10:19:28AM +0200, Jens Gustedt wrote:
> > OTOH GCC transforms
> > (uintptr_t)&a != (uintptr_t)(&b+1)
> > into &a != &b + 1 (for equality compares) and then
> > doesn't follow this C rule anyways.
>
> Actually our proposal we are discussing here goes exactly the other
> way
Hello,
On Thu, 18 Apr 2019 14:42:22 +0200 Richard Biener
wrote:
> On Thu, Apr 18, 2019 at 2:20 PM Uecker, Martin
> wrote:
> > 1.) Compilers do not use conditional equivalences for
> > optimizations of pointers (or only when additional
> > conditions apply which make it safe)
> >
> > 2.) We mak
Am Donnerstag, den 18.04.2019, 15:49 +0100 schrieb Peter Sewell:
> On Thu, 18 Apr 2019 at 14:54, Uecker, Martin
> wrote:
> >
> > Am Donnerstag, den 18.04.2019, 07:42 -0600 schrieb Jeff Law:
> > > On 4/18/19 6:20 AM, Uecker, Martin wrote:
> > > > Am Donnerstag, den 18.04.2019, 11:45 +0100 schrieb
On Thu, 18 Apr 2019 at 14:54, Uecker, Martin
wrote:
>
> Am Donnerstag, den 18.04.2019, 07:42 -0600 schrieb Jeff Law:
> > On 4/18/19 6:20 AM, Uecker, Martin wrote:
> > > Am Donnerstag, den 18.04.2019, 11:45 +0100 schrieb Peter Sewell:
> > > > On Thu, 18 Apr 2019 at 10:32, Richard Biener
> > > > w
Am Donnerstag, den 18.04.2019, 07:42 -0600 schrieb Jeff Law:
> On 4/18/19 6:20 AM, Uecker, Martin wrote:
> > Am Donnerstag, den 18.04.2019, 11:45 +0100 schrieb Peter Sewell:
> > > On Thu, 18 Apr 2019 at 10:32, Richard Biener
> > > wrote:
...
> > 4.) Compilers make sure that exposed objects never
Am Donnerstag, den 18.04.2019, 14:42 +0200 schrieb Richard Biener:
> On Thu, Apr 18, 2019 at 2:20 PM Uecker, Martin
> wrote:
> >
> > Am Donnerstag, den 18.04.2019, 11:45 +0100 schrieb Peter Sewell:
> > > On Thu, 18 Apr 2019 at 10:32, Richard Biener
> > > wrote:
> >
> >
> > > An equality test
On 4/18/19 6:20 AM, Uecker, Martin wrote:
> Am Donnerstag, den 18.04.2019, 11:45 +0100 schrieb Peter Sewell:
>> On Thu, 18 Apr 2019 at 10:32, Richard Biener
>> wrote:
>
>
>> An equality test of two pointers, on the other hand, doesn't necessarily
>> mean that they are interchangeable. I don't
On 4/18/19 6:50 AM, Jakub Jelinek wrote:
> On Thu, Apr 18, 2019 at 02:47:18PM +0200, Jakub Jelinek wrote:
>> On Thu, Apr 18, 2019 at 02:42:22PM +0200, Richard Biener wrote:
1.) Compilers do not use conditional equivalences for
optimizations of pointers (or only when additional
condit
Am Donnerstag, den 18.04.2019, 14:30 +0200 schrieb Richard Biener:
> On Thu, Apr 18, 2019 at 1:57 PM Uecker, Martin
> wrote:
> >
> > Am Donnerstag, den 18.04.2019, 11:56 +0200 schrieb Richard Biener:
> > > On Thu, Apr 18, 2019 at 11:31 AM Richard Biener
> > > wrote:
> > > >
> > > > The additio
On Thu, Apr 18, 2019 at 02:47:18PM +0200, Jakub Jelinek wrote:
> On Thu, Apr 18, 2019 at 02:42:22PM +0200, Richard Biener wrote:
> > > 1.) Compilers do not use conditional equivalences for
> > > optimizations of pointers (or only when additional
> > > conditions apply which make it safe)
> > >
> >
On Thu, Apr 18, 2019 at 02:42:22PM +0200, Richard Biener wrote:
> > 1.) Compilers do not use conditional equivalences for
> > optimizations of pointers (or only when additional
> > conditions apply which make it safe)
> >
> > 2.) We make pointer comparison between a pointer
> > and a one-after poin
On Thu, Apr 18, 2019 at 2:20 PM Uecker, Martin
wrote:
>
> Am Donnerstag, den 18.04.2019, 11:45 +0100 schrieb Peter Sewell:
> > On Thu, 18 Apr 2019 at 10:32, Richard Biener
> > wrote:
>
>
> > An equality test of two pointers, on the other hand, doesn't necessarily
> > mean that they are interchan
On Thu, Apr 18, 2019 at 1:57 PM Uecker, Martin
wrote:
>
> Am Donnerstag, den 18.04.2019, 11:56 +0200 schrieb Richard Biener:
> > On Thu, Apr 18, 2019 at 11:31 AM Richard Biener
> > wrote:
> > >
> > > On Wed, Apr 17, 2019 at 4:12 PM Uecker, Martin
> > > wrote:
> > > >
> > > > Am Mittwoch, den 17.
Am Donnerstag, den 18.04.2019, 11:45 +0100 schrieb Peter Sewell:
> On Thu, 18 Apr 2019 at 10:32, Richard Biener
> wrote:
> An equality test of two pointers, on the other hand, doesn't necessarily
> mean that they are interchangeable. I don't see any good way to
> avoid that in a provenance sem
Am Donnerstag, den 18.04.2019, 11:56 +0200 schrieb Richard Biener:
> On Thu, Apr 18, 2019 at 11:31 AM Richard Biener
> wrote:
> >
> > On Wed, Apr 17, 2019 at 4:12 PM Uecker, Martin
> > wrote:
> > >
> > > Am Mittwoch, den 17.04.2019, 15:34 +0200 schrieb Richard Biener:
> > > > On Wed, Apr 17, 20
On Thu, 18 Apr 2019 at 10:56, Richard Biener wrote:
>
> On Thu, Apr 18, 2019 at 11:31 AM Richard Biener
> wrote:
> >
> > On Wed, Apr 17, 2019 at 4:12 PM Uecker, Martin
> > wrote:
> > >
> > > Am Mittwoch, den 17.04.2019, 15:34 +0200 schrieb Richard Biener:
> > > > On Wed, Apr 17, 2019 at 2:56 PM
On Thu, 18 Apr 2019 at 10:32, Richard Biener wrote:
>
> On Wed, Apr 17, 2019 at 4:12 PM Uecker, Martin
> wrote:
> >
> > Am Mittwoch, den 17.04.2019, 15:34 +0200 schrieb Richard Biener:
> > > On Wed, Apr 17, 2019 at 2:56 PM Uecker, Martin
> > > wrote:
> > > >
> > > > Am Mittwoch, den 17.04.2019,
On Thu, Apr 18, 2019 at 11:31 AM Richard Biener
wrote:
>
> On Wed, Apr 17, 2019 at 4:12 PM Uecker, Martin
> wrote:
> >
> > Am Mittwoch, den 17.04.2019, 15:34 +0200 schrieb Richard Biener:
> > > On Wed, Apr 17, 2019 at 2:56 PM Uecker, Martin
> > > wrote:
> > > >
> > > > Am Mittwoch, den 17.04.201
On Wed, Apr 17, 2019 at 4:12 PM Uecker, Martin
wrote:
>
> Am Mittwoch, den 17.04.2019, 15:34 +0200 schrieb Richard Biener:
> > On Wed, Apr 17, 2019 at 2:56 PM Uecker, Martin
> > wrote:
> > >
> > > Am Mittwoch, den 17.04.2019, 14:41 +0200 schrieb Richard Biener:
> > > > On Wed, Apr 17, 2019 at 1:5
On Wed, 17 Apr 2019 at 15:12, Uecker, Martin
wrote:
>
> Am Mittwoch, den 17.04.2019, 15:34 +0200 schrieb Richard Biener:
> > On Wed, Apr 17, 2019 at 2:56 PM Uecker, Martin
> > wrote:
> > >
> > > Am Mittwoch, den 17.04.2019, 14:41 +0200 schrieb Richard Biener:
> > > > On Wed, Apr 17, 2019 at 1:53
Am Mittwoch, den 17.04.2019, 15:34 +0200 schrieb Richard Biener:
> On Wed, Apr 17, 2019 at 2:56 PM Uecker, Martin
> wrote:
> >
> > Am Mittwoch, den 17.04.2019, 14:41 +0200 schrieb Richard Biener:
> > > On Wed, Apr 17, 2019 at 1:53 PM Uecker, Martin
> > > wrote:
> > > >
> > > > > Since
> > > >
On Wed, Apr 17, 2019 at 2:56 PM Uecker, Martin
wrote:
>
> Am Mittwoch, den 17.04.2019, 14:41 +0200 schrieb Richard Biener:
> > On Wed, Apr 17, 2019 at 1:53 PM Uecker, Martin
> > wrote:
>
> > >
> > > > Since
> > > > your proposal is based on an abstract machine there isn't anything
> > > > like a
Am Mittwoch, den 17.04.2019, 14:41 +0200 schrieb Richard Biener:
> On Wed, Apr 17, 2019 at 1:53 PM Uecker, Martin
> wrote:
> >
> > > Since
> > > your proposal is based on an abstract machine there isn't anything
> > > like a pointer with multiple provenances (which "anything" is), just
> > > po
On Wed, Apr 17, 2019 at 1:53 PM Uecker, Martin
wrote:
>
>
> Hi Richard,
>
> Am Mittwoch, den 17.04.2019, 11:41 +0200 schrieb Richard Biener:
> > On Wed, Apr 17, 2019 at 11:15 AM Peter Sewell
> > wrote:
> > >
> > > On 17/04/2019, Richard Biener wrote:
> > > > On Fri, Apr 12, 2019 at 5:31 PM Pete
Hi Richard,
Am Mittwoch, den 17.04.2019, 11:41 +0200 schrieb Richard Biener:
> On Wed, Apr 17, 2019 at 11:15 AM Peter Sewell
> wrote:
> >
> > On 17/04/2019, Richard Biener wrote:
> > > On Fri, Apr 12, 2019 at 5:31 PM Peter Sewell
> > > wrote:
...
> > > So this is not what GCC implements whi
On Wed, Apr 17, 2019 at 11:15 AM Peter Sewell wrote:
>
> On 17/04/2019, Richard Biener wrote:
> > On Fri, Apr 12, 2019 at 5:31 PM Peter Sewell
> > wrote:
> >>
> >> On Fri, 12 Apr 2019 at 15:51, Jeff Law wrote:
> >> >
> >> > On 4/2/19 2:11 AM, Peter Sewell wrote:
> >> > > Dear all,
> >> > >
> >>
On 17/04/2019, Richard Biener wrote:
> On Fri, Apr 12, 2019 at 5:31 PM Peter Sewell
> wrote:
>>
>> On Fri, 12 Apr 2019 at 15:51, Jeff Law wrote:
>> >
>> > On 4/2/19 2:11 AM, Peter Sewell wrote:
>> > > Dear all,
>> > >
>> > > continuing the discussion from the 2018 GNU Tools Cauldron, we
>> > > (
On Fri, Apr 12, 2019 at 5:31 PM Peter Sewell wrote:
>
> On Fri, 12 Apr 2019 at 15:51, Jeff Law wrote:
> >
> > On 4/2/19 2:11 AM, Peter Sewell wrote:
> > > Dear all,
> > >
> > > continuing the discussion from the 2018 GNU Tools Cauldron, we
> > > (the WG14 C memory object model study group) now
>
On Fri, 12 Apr 2019 at 15:51, Jeff Law wrote:
>
> On 4/2/19 2:11 AM, Peter Sewell wrote:
> > Dear all,
> >
> > continuing the discussion from the 2018 GNU Tools Cauldron, we
> > (the WG14 C memory object model study group) now
> > have a detailed proposal for pointer provenance semantics, refining
On 4/2/19 2:11 AM, Peter Sewell wrote:
> Dear all,
>
> continuing the discussion from the 2018 GNU Tools Cauldron, we
> (the WG14 C memory object model study group) now
> have a detailed proposal for pointer provenance semantics, refining
> the "provenance not via integers (PNVI)" model presented
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