search for: speculatibility

FYI, see also the previous discussion about "speculatable": http://lists.cs.uiuc.edu/pipermail/llvmdev/2013-July/064426.html I think such an attribute should be added. In the thread which lead up to that thread, I proposed using more fine-grained attributes and Michael rightly pointed out the problem with that: you'd need one for every possible form of undefined behaviour. You

Hi! I'm interested in what attributes in LLVM mean, specifically how to say that the result is always the same for the given input parameters. The main thing would be to merge two calls with the same parameters when the function is declared but not defined. (just like two stores). I'll call this property mergability. %1 := call @test(%0) %2 := call @test(%0) and the optimization would

A patch is attached. Not sure I'm happy with this due to the aforementioned orthogonality concerns, but I really don't have any better ideas. If anyone does, feel free to offer them, I don't mind throwing this patch into the trash. (Also, not happy with the name, using "speculatable" as Nick suggested, for the lack of other options. If the name stays I'll add it to the

Kuperstein, Michael M wrote: > A patch is attached. + const CallInst* CI = dyn_cast<CallInst>(Inst); + return CI->isSafeToSpeculativelyExecute(); "return cast<CallInst>(Inst)->isSafeToSpeculativelyExecute();"? Use cast<> instead of dyn_cast<>. See http://llvm.org/docs/ProgrammersManual.html#isa . Then I don't think it needs to be two lines.

I'd like to suggest a different direction which should accomplish similar ends. I think it would make sense to introduce an attribute: csecandidate. If we see a call-site "X" marked as csecandidate, it would imply that it can be replaced with any other call-site "Y" with the same arguments which dominate the call-site at "X". However, there are some cases that

On 22 July 2013 01:11, Kuperstein, Michael M <michael.m.kuperstein at intel.com > wrote: > Of course frontends are free to put attributes, but it would be nice if > optimizations actually used them. ;-) > My use case is that of proprietary frontend that happens to know some > library function calls - which are only resolved at link time - have no > side effects and are safe

Right, will fix the CallInst, copy/pasted from a different case and didn't notice what I was doing, thanks. Re LangRef.rst, that's what I meant, I'm still hoping for better suggestions regarding the name... As to the conflict - Tobias, feel free to go first, I'll merge. -----Original Message----- From: Nick Lewycky [mailto:nicholas at mxc.ca] Sent: Thursday, July 25, 2013 12:11

Hey list, I've recently done the first test run of bumping our Burst compiler from LLVM 10 -> 11 now that the branch has been cut, and have noticed an apparent loop vectorization codegen regression for X86 with AVX or AVX2 enabled. The following IR example is vectorized to 4 wide with LLVM 11 and trunk whereas in LLVM 10 it (correctly as per what we want) vectorized it 8 wide matching the

Hi László, On 8/13/20 5:21 PM, László Radnai via llvm-dev wrote: > (Sorry I clicked reply instead of reply to all) > I'm fighting with my email client, I hope the quoted text contains > what I want it to contain. > > ---------- Forwarded message ---------- > From: László Radnai <radlaci97 at gmail.com> > Date: Fri, 14 Aug 2020 00:11:35 +0200 > Subject:

Hello, OpenCL C specifies that instructions should not trap (it is "discouraged" in the specs). If they do, it's vendor-specific how the hardware exceptions are handled. It might be also the case with some other (future) languages targeting "streamlined" parallel accelerators in an heterogeneous setting. At least CUDA comes to mind. What about OpenACC and the new OpenMP,

Of course frontends are free to put attributes, but it would be nice if optimizations actually used them. ;-) My use case is that of proprietary frontend that happens to know some library function calls - which are only resolved at link time - have no side effects and are safe to execute speculatively, and wants to tell the optimizer it can move them around however it likes. I'll gladly submit

Hal Finkel wrote: > But it is not all optimizations that are the problem. Rather, it > seems like a select few (e.g. things involving collapsing allowed > non-determinism in atomics), and losing those optimizations seems > better than generally losing function-attribute deduction. If we go by the langref, then optimizations that fold undef are also problematic (though most C/C++

Tried a bunch of them there (x86-64, haswell, znver2) and they all defaulted to 4-wide - haswell additionally caused some extra loop unrolling but still with 8-wide pows. Cheers, -Neil. On Thu, Jul 16, 2020 at 2:39 PM Roman Lebedev <lebedev.ri at gmail.com> wrote: > Did you specify the target CPU the code should be optimized for? > For clang that is -march=native/znver2/... /

Hi, I try to use llvm-dis to disassemble the result after opt, my pass will add a intrinsic after the load instruction, like following: bool fpscan::ldAddMetadata (Instruction *Inst, StringRef c) { std::vector<Metadata *> dataTuples; // Add metadata in list dataTuples.push_back(MDString::get(Inst->getContext(), c)); MDNode* N = MDNode::get(Inst->getContext(),

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:

...ther* transforms that we ourselves want to do, where these "other transforms" pretend certain abnormal cases do not exist. Poison is a "stand-in" for these transforms, which are sometimes non-local. For instance, continuing the previous example, say we're interested in the speculatibility of t = K `udiv` (-1 + (sum.sext >> 32)) We don't _really_ care about doing something intelligent when sum.sext is provably poison. However, we do care about taking into the _possibility_ of sum.sext being poison, which is really just a more precise way of saying that we care about taki...

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 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,

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

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,