similar to: [LLVMdev] RFC: attribute for a pointer which is dereferenceable xor null

Hi, While working on PR21780, I used "dereferenceable_or_null" metadata and I realized now that it is not correct for my solution to use this metadata type since it might point to an address that it is not dereferenceable but null. I think that we need another new metadata type, something like "dereferenceable" with that we could annotate any load (not just pointer type like

Indeed. But the problem here is that Dinar is trying to keep information after a load/store is removed by instcombine For example: v4sf v = {p[0], p[1], p[2], p[3]}; v4sf v2 = shuffle(v, 0, 0, 2, 2); Some pass comes in and removes the p[3] and p[1]. Now you have smaller code, but lost the ability to use a vector load for all those values + shuffle. The code got scalarized because we lost the

On 02/19, Juneyoung Lee via llvm-dev wrote: > Hello, > > > Would it be correct to resolve this by saying that dereferenceable(N) > > *implies* not_poison? This would be helpful as a clarification of how > > it all fits together. > > Yes, I think it makes sense. I don't we should do that. Take the `gep inbounds` example: char* foo(char *arg) { return `gep

On Wed, Feb 19, 2020 at 3:51 AM Juneyoung Lee via llvm-dev <llvm-dev at lists.llvm.org> wrote: > I think not_poison (Johannes's used keyword) makes sense. We can simulate the original UB semantics by simply attaching it, as explained. > For the attributes other than nonnull, we may need more discussion; align attribute seems to be okay with defining it as poison, dereferenceable

Two thoughts: 1. I think that we should aim for regularity, to the extent possible, and so we should treat nonnull, align, etc. similarly w.r.t. to whether they produce poison or UB. 2. I was thinking about the following last night, and it clarified for me why having an not_poison attribute makes sense and seems useful, and how poison/UB might affect things on a function-call boundary itself.

----- Original Message ----- > From: "Philip Reames" <listmail at philipreames.com> > To: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> > Sent: Friday, February 27, 2015 5:34:36 PM > Subject: Re: [LLVMdev] RFC: PerfGuide for frontend authors > > The first version of this document is now live: >

This email is just to summarize a bit of digging I did last night into our attribute inference.  Unfortunately, I'm not going to have time to implement any of the gaps I noticed, but I figured someone else out there might be interested. *Missing Attributes* argmemonly - influences AA, particularly relevant for libraries which wrap build in functions which are annotated, but don't

Maybe we could list some of these as a GSoC project? Seems like a self-contained task that can be simple as desired and as hard as the student wants it to be. Nuno -----Original Message----- From: Philip Reames via llvm-dev Sent: Friday, February 16, 2018 6:48 PM To: llvm-dev Subject: Re: [llvm-dev] Missing attribute inference cases On 02/16/2018 10:29 AM, Philip Reames via llvm-dev wrote:

I left a comment on https://reviews.llvm.org/D18738 earlier which I feel is related to this discussion, so I'm reproducing it here: I wonder though if what we want to express isn't some sort of "type-based dereferencability annotations". For example the semantics I care about are essentially, "if you know you have a defereferencable pointer, you can go and dereference any

I'd like to propose that we create a new Performance Guide document. The target of this document will be frontend authors, not necessarily LLVM contributors. The content will be a collection of items a frontend author might want to know about how to generate LLVM IR which will optimize well. Some ideas on topics that might be worthwhile: - Prefer sext over zext when value is known to be

LLVM's Attribute APIs need an overhaul. Current problems ================ First, testing for an attribute on an Argument is slow. llvm::AttributeSet::getAttributes(int) consumed 2% of cycles while optimizing llc during LTO. Our mid-level optimizations are constantly asking if a given argument has some attribute (nonnull, dereferencable, etc), and this is currently linear in the size of the

Sure, but is anyone willing to mentor?  I don't have time.  I can advise, but only infrequently. Philip On 02/16/2018 03:47 PM, Davide Italiano wrote: > Yes, I agree with you this sounds like a great GSoC. > > On Fri, Feb 16, 2018 at 3:42 PM, Nuno Lopes via llvm-dev > <llvm-dev at lists.llvm.org> wrote: >> Maybe we could list some of these as a GSoC project?

> On Feb 27, 2015, at 3:58 PM, Hal Finkel <hfinkel at anl.gov> wrote: > > ----- Original Message ----- >> From: "Philip Reames" <listmail at philipreames.com> >> To: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> >> Sent: Friday, February 27, 2015 5:34:36 PM >> Subject: Re: [LLVMdev] RFC: PerfGuide for frontend

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

Hi everyone, Nick and Philip suggested something yesterday that I'd also thought about: supporting attributes on values (http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20140908/234323.html). The primary motivation for this is to provide a way of attaching pointer information, such as noalias, nonnull and dereferenceable(n), to pointers generated by loads. Doing this for pointers

HI, When compiling the open-source software cryptopp (https://www.cryptopp.com/#download <https://www.cryptopp.com/#download>) version 5.6.4 I found a strange issue with the IR generated. The issue only appears when compiling with -O2 optimisation in the integer.cpp file (the function is _ZN8CryptoPPrsERNSt3__113basic_istreamIcNS0_11char_traitsIcEEEERNS_7IntegerE ->

On 02/16/2018 10:29 AM, Philip Reames via llvm-dev wrote: > > This email is just to summarize a bit of digging I did last night into > our attribute inference.  Unfortunately, I'm not going to have time to > implement any of the gaps I noticed, but I figured someone else out > there might be interested. > > *Missing Attributes* > > argmemonly - influences AA,

2017-04-05 18:30 GMT+02:00 Sanjoy Das <sanjoy at playingwithpointers.com>: > Hi Piotr, > > On Mon, Apr 3, 2017 at 2:01 PM, Piotr Padlewski > <piotr.padlewski at gmail.com> wrote: > >> I don't see any way to model it right now in LLVM, but I see a one > simple > >> solution: > >> add extra information to the metadata nodes indicating that

Yes, I agree with you this sounds like a great GSoC. On Fri, Feb 16, 2018 at 3:42 PM, Nuno Lopes via llvm-dev <llvm-dev at lists.llvm.org> wrote: > Maybe we could list some of these as a GSoC project? > Seems like a self-contained task that can be simple as desired and as hard > as the student wants it to be. > > Nuno > > -----Original Message----- From: Philip Reames

2017-04-06 17:57 GMT+02:00 Sanjoy Das <sanjoy at playingwithpointers.com>: > Hi Piotr, > > On April 6, 2017 at 2:36:53 AM, Piotr Padlewski > (piotr.padlewski at gmail.com) wrote: > > I disagree, I find it different than the patch you mentioned. We don't > have > > any problems with code like this: > > > > ptr = load i8*, i8** %ptrptr,