similar to: RFC: Emitting empty invariant group for vtable loads

Hi Piotr, I think makes sense. Modulo bitcasts, the invariant is identified by a particular pointer SSA value. Given that you can't sensibly have two nonequivalent invariants associated with the same pointer SSA value simultaneously, there's no need to also identify the invariant with a metadata string as well. When we need a new "identifier" for the pointed-to value, we

2017-01-26 3:28 GMT+01:00 Richard Smith <richard at metafoo.co.uk>: > On 25 January 2017 at 15:03, Hal Finkel via cfe-dev < > cfe-dev at lists.llvm.org> wrote: > >> Hi Piotr, >> >> I think makes sense. Modulo bitcasts, the invariant is identified by a >> particular pointer SSA value. Given that you can't sensibly have two >> nonequivalent

2017-01-26 15:41 GMT+01:00 Hal Finkel <hfinkel at anl.gov>: > > On 01/26/2017 06:44 AM, Piotr Padlewski wrote: > > > > 2017-01-26 3:28 GMT+01:00 Richard Smith <richard at metafoo.co.uk>: > >> On 25 January 2017 at 15:03, Hal Finkel via cfe-dev < >> cfe-dev at lists.llvm.org> wrote: >> >>> Hi Piotr, >>> >>> I think

On 01/28/2017 10:36 AM, Piotr Padlewski wrote: > > > 2017-01-26 15:41 GMT+01:00 Hal Finkel <hfinkel at anl.gov > <mailto:hfinkel at anl.gov>>: > > > On 01/26/2017 06:44 AM, Piotr Padlewski wrote: >> >> >> 2017-01-26 3:28 GMT+01:00 Richard Smith <richard at metafoo.co.uk >> <mailto:richard at metafoo.co.uk>>: >>

2017-04-01 15:59 GMT+02:00 Piotr Padlewski <piotr.padlewski at gmail.com>: > > > 2017-03-31 23:20 GMT+02:00 Sanjoy Das <sanjoy at playingwithpointers.com>: > >> Hi Piotr, >> >> On March 31, 2017 at 1:07:12 PM, Piotr Padlewski >> (piotr.padlewski at gmail.com) wrote: >> > [snip] >> > Do I understand it correctly, that it is legal to

> On Mar 19, 2018, at 7:27 PM, Piotr Padlewski via cfe-dev <cfe-dev at lists.llvm.org> wrote: > > Hi folks, > > here is a link to the proposal that we've been working on lately: > https://docs.google.com/document/d/16GVtCpzK8sIHNc2qZz6RN8amICNBtvjWUod2SujZVEo/edit?usp=sharing

Hi folks, here is a link to the proposal that we've been working on lately: https://docs.google.com/document/d/16GVtCpzK8sIHNc2qZz6RN8amICNBt vjWUod2SujZVEo/edit?usp=sharing But for the record, I also paste it here. Feedback will be really appreciated!

Hi Piotr, On March 31, 2017 at 1:07:12 PM, Piotr Padlewski (piotr.padlewski at gmail.com) wrote: > [snip] > Do I understand it correctly, that it is legal to do the hoist because all > of the instructions above %vtable does not throw? Yes, I think you're right.  HeaderMayThrow is a conservative approximation, and the conservativeness is biting us here. > Are there any plans to

Hi John, 2018-03-28 23:23 GMT+02:00 John McCall <rjmccall at apple.com>: > > > On Mar 19, 2018, at 7:27 PM, Piotr Padlewski via cfe-dev < > cfe-dev at lists.llvm.org> wrote: > > Hi folks, > > here is a link to the proposal that we've been working on lately: > https://docs.google.com/document/d/16GVtCpzK8sIHNc2qZz6RN8am >

Hi all, I have a question about dereferenceable metadata on load instruction. I have a patch (https://reviews.llvm.org/D31539) for LICM that hoists loads with !invariant.group. The motivation example is devirtualization: struct A { virtual void foo(); }; int bar(); void indirect(A &a) { while(bar()) a.foo(); } With -O2 -fstrict-vtable-pointers we get: define void

On Fri, Mar 31, 2017 at 10:23 AM, Sanjoy Das <sanjoy at playingwithpointers.com > wrote: > Hi Piotr, > > On March 31, 2017 at 9:07:42 AM, Piotr Padlewski > (piotr.padlewski at gmail.com) wrote: > > Hi all, > > I have a question about dereferenceable metadata on load instruction. I > > have a patch (https://reviews.llvm.org/D31539) for LICM that hoists >

Hi folks, please check out our RFC: Supported Optimizations attribute https://docs.google.com/document/d/1s0n-JVaSNML1Z9SCZVg2bgisxswIJAK2Tp9DahucW10/edit?usp=sharing Pasting it here for the record: RFC: supported_optimizations attribute Piotr Padlewski - piotr.padlewski at gmail.com Krzysztof Pszeniczny - kpszeniczny at google.com December 2018 Introduction Sometimes a possible class of

On Fri, Jul 31, 2015 at 3:53 PM, Philip Reames <listmail at philipreames.com> wrote: > > Quoting from the google doc: "If we don’t know definition of some > function, we assume that it will not call @llvm.invariant.group.barrier(). > " > This part really really bugs me. We generally try to assume minimal > knowledge of external functions (i.e. they can do

2018-03-29 18:01 GMT+02:00 John McCall <rjmccall at apple.com>: > On Mar 29, 2018, at 9:12 AM, Piotr Padlewski <piotr.padlewski at gmail.com> > wrote: > 2018-03-28 23:23 GMT+02:00 John McCall <rjmccall at apple.com>: >> >> On Mar 19, 2018, at 7:27 PM, Piotr Padlewski via cfe-dev < >> cfe-dev at lists.llvm.org> wrote: >> *Note that adding

Hi folks, I would like to ask for some help with handling invariant.group metadata for pointer comparison. Currently, we have a problem with devirtualization of this code: void compare() { A* a = new A; a->foo(); A* b = new(a) B; if (a == b) { b->foo(); } } Now because it is legal to replace b with an in the branch the vtable load will use old pointer operand

> On Mar 29, 2018, at 9:12 AM, Piotr Padlewski <piotr.padlewski at gmail.com> wrote: > 2018-03-28 23:23 GMT+02:00 John McCall <rjmccall at apple.com <mailto:rjmccall at apple.com>>: >> On Mar 19, 2018, at 7:27 PM, Piotr Padlewski via cfe-dev <cfe-dev at lists.llvm.org <mailto:cfe-dev at lists.llvm.org>> wrote: >> Note that adding calls to strip and

On Thu, Jul 23, 2015 at 11:42 AM, Piotr Padlewski <prazek at google.com> wrote: > HI, > Yep, our proposal doesn't cover it, because this load ; icmp ; assume; > will land global initilizer function, and main will not see it. > At least if foo would be called multiple times, then we would only have > one load from vtable, but unfortunatelly we will not be able to inline,

There are another things left: 1. Adding check for ubsan to detect UBs caused by inplace new 2. upgrading GVN to optimize based on !invariant.group across BBs 3. Adding something like "nocapture-global" that will say that this pointer is not being captured by global, but may be captured for example by returning it from function. This thing is important because this is exactly what

HI, Yep, our proposal doesn't cover it, because this load ; icmp ; assume; will land global initilizer function, and main will not see it. At least if foo would be called multiple times, then we would only have one load from vtable, but unfortunatelly we will not be able to inline, or make direct call to it with this approach. I think that this case is rare enough to solve it right now. Piotr

Hi folks, this summer I will work with Richard Smith on clang devirtualization. Check out our proposal: https://docs.google.com/document/d/1f2SGa4TIPuBGm6y6YO768GrQsA8awNfGEJSBFukLhYA/edit?usp=sharing And modified LangRef http://reviews.llvm.org/D11399 You can also check out previous disscussion that was started before our proposal was ready -