similar to: Publication - Devirtualization in LLVM

> On Mar 30, 2018, at 09:39, John McCall via llvm-dev <llvm-dev at lists.llvm.org> wrote: > >> On Mar 30, 2018, at 10:36 AM, Piotr Padlewski <piotr.padlewski at gmail.com <mailto:piotr.padlewski at gmail.com>> wrote: >> >> Do you know any other specific situations and metadata that would require, or would be good if would use the same solution? >

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,

Hi Piotr, You may be interested in a recent patch I posted: http://reviews.llvm.org/D11043 This patch addresses a de-virtualization case that I’m not sure would be handled by your current proposal, namely that of a virtual call where the ‘this’ object is a global variable. For example: struct A { A(); virtual void foo(); }; void g(A * a) { a->foo(); } A a; int main()

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

> On Mar 30, 2018, at 10:36 AM, Piotr Padlewski <piotr.padlewski at gmail.com> wrote: > 2018-03-29 18:01 GMT+02:00 John McCall <rjmccall at apple.com <mailto:rjmccall at apple.com>>: >> On Mar 29, 2018, at 9:12 AM, Piotr Padlewski <piotr.padlewski at gmail.com <mailto:piotr.padlewski at gmail.com>> wrote: >> 2018-03-28 23:23 GMT+02:00 John McCall

Hi Piotr, Thanks for posting this! First, a question. When you say, regarding i8* @llvm.invariant.group.barrier(i8*): "Required to handle destructors, placement new and std::launder. Call of this function will be put on the end of each of this functions" I completely understand placement new and std::launder. I don't understand destructors, could you explain? Also, am I correct

On Sat, Jul 25, 2015 at 12:39 PM, Hal Finkel <hfinkel at anl.gov> wrote: > Hi Piotr, > > Thanks for posting this! First, a question. When you say, regarding i8* > @llvm.invariant.group.barrier(i8*): > > "Required to handle destructors, placement new and std::launder. Call of > this function will be put on the end of each of this functions" > > I

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, 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 -

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 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

Sounds like it works! Basically, adding these extra strip.invariant.group calls before pointer comparisons breaks the transform that was problematic. Presumably, clang would only strip invariant groups from pointers to dynamic types before casting them or using them in a comparison, so that the value equivalence optimization still works in the general case. The proposal trades value equivalence

Hi Piotr, On Thu, May 4, 2017 at 6:44 AM, Piotr Padlewski <piotr.padlewski at gmail.com> wrote: > Also, Sanjoy proposed to mark invariant.group features as experimental, so > we will not be afraid to break behavior of frontends that already use it. > > Right now I am pretty sure that clang is the only one that curently uses it > (and not by default). Firstly, yes, I think we

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

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 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

> 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

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

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 >

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