similar to: Calling a null pointer. How undefined it is?

Hi Sanjoy, >> I'm not familiar with fiber-type APIs, but I assume fiber_fork is like >> setjmp, in that it can "return twice"? Yes, user-mode stack switching API are somewhat similar to setjmp. Here are links to a doc page and implementation, just in case you are curious: http://www.boost.org/doc/libs/1_59_0/libs/context/doc/html/context/context.html

Hi all: Below is a proposal to add experimental coroutine support to LLVM. Though this proposal is motivated primarily by the desire to support C++ Coroutines [1], the llvm representation is language neutral and can be used to support coroutines in other languages as well. Clang + llvm coroutines allows you to take this code: generator<int> range(int from, int to) { for(int i =

(Dropped llvm-dev by accident. Putting it back) HI Eli: >> coro.barrier() doesn't work: if the address of the alloca doesn't escape, >> alias analysis will assume the barrier can't read or write the value of >> the alloca, so the barrier doesn't actually block code movement. Got it. I am new to this and learning a lot over the course of this thread. Thank you

Hi Sanjoy: >> Now in the above CFG %val can be folded to 10, but in reality you need >> a PHI of 10 and 20 Quick answer: folding %val to 10 is OK, but, I would prefer it to be 'undef' or even catch it in the verifier as it is a programmer/frontend error. Details are in the second half of my reply. I would like to start with the thought experiment you suggested, as it might

Hi David: >> How do you deal with basic blocks which appear to be used by multiple parts >> of the coroutine? We handled this in WinEHPrepare by cloning any BBs which >> were shared. I experimented with several approaches, but, cloning ended up being the simplest and most reliable. Suspend points express three different control flows that can happen at the suspend point: a

On Fri, Jun 10, 2016 at 5:25 PM, Gor Nishanov <gornishanov at gmail.com> wrote: > Hi Eli: > > >> Naively, you would expect that it would be legal to hoist the store... > >> but that breaks your coroutine semantics because the global could be > mutated > >> between the first return and the resume. > > Hmmm... I don't see the problem. I think

cc llvm-dev On Thu, Jul 21, 2016 at 9:57 AM, Vadim Chugunov <vadimcn at gmail.com> wrote: > Hi Gor, > Does you design support resumption with parameter(s)? (such as Python's > generator.send(x)). I suppose the "promise" could be used for passing data > both ways, but if that's the plan, please mention this explicitly in the > design doc. > Also, how is

Hi Eli: >> semantics of the fork intrinsic... thinking about it a bit more, I think >> you're going to run into problems with trying to keep around a return block >> through optimizations: How about this? Make all control flow explicit (duh). declare i8 coro.suspend([...]) returns: 0 - resume 1 - cleanup anything else - suspend Now we can get

On Fri, Jun 10, 2016 at 6:36 AM, Gor Nishanov <gornishanov at gmail.com> wrote: > >> If you're going down that route, that still leaves the question of the > >> semantics of the fork intrinsic... thinking about it a bit more, I think > >> you're going to run into problems with trying to keep around a return > block > >> through optimizations:

I think I got it. Original model (with coro.fork and two-way coro.suspend) will work with a tiny tweak. In the original model, I was replacing coro.suspend with br %return in original function. The problem was coming from potential phi-nodes introduces into return block during optimizations. Let's make sure that there is only entry into the return block. In the original model, ReturnBB had

Hi Eli: >> Block1: >> %0 = call i8 coro.suspend() >> switch i8 %0, label suspend1 [i8 0 %return] ; or icmp + br i1 >> Suspend1: >> switch i8 %0, label %resume1 [i8 1 %destroy1] ; or icmp + br i1 >> >> This doesn't look right: intuitively the suspend happens after the return >> block runs. Perhaps, but, that is not the intended

Hi Eli: Thank you very much for your comments! >> If you need some sort of unusual control flow construct, make it a >> proper terminator instruction I would love to. I was going by the advice in "docs/ExtendingLLVM.rst": "WARNING: Adding instructions changes the bitcode format, and it will take some effort to maintain compatibility with the previous

Hi all: I've included below a brief description of coroutine related optimization passes and some questions/thoughts related to them. Looking forward to your feedback, comments and questions. Thank you! Roadmap: ======== 1) Get agreement on coroutine representation and overall direction. .. repeat 1) until happy http://lists.llvm.org/pipermail/llvm-dev/2016-June/100838.html (Initial)

On Thu, Jun 9, 2016 at 1:49 PM, Eli Friedman <eli.friedman at gmail.com> wrote: >> Right... but that doesn't mean the call to the suspend intrinsic has to be >> the last non-terminator instruction in the basic block before you run >> CoroSplit. You can split the basic block in CoroSplit so any instructions >> after the suspend call are part of a different basic

Hello all! (+cc Vedant Kumar, who I've been told knows a lot about UBSan!) I am trying to fix an assert that occurs when the transforms in llvm/lib/Transforms/Coroutines are applied to LLVM IR that has been generated with UBSan enabled -- specifically, '-fsanitize=null'. You can see an example of the assert in this 26-line C++ file here: https://godbolt.org/g/Gw9UZq Note that

> On Mar 19, 2018, at 3:44 PM, Brian Gesiak <modocache at gmail.com> wrote: > > Hello all! > (+cc Vedant Kumar, who I've been told knows a lot about UBSan!) > > I am trying to fix an assert that occurs when the transforms in llvm/lib/Transforms/Coroutines are applied to LLVM IR that has been generated with UBSan enabled -- specifically, '-fsanitize=null'. >

Summary I would like to propose that we add the following function attribute to LLVM: synthetic(<string>) This attribute can only be applied to functions. It is not a semantic statement about the function it decorates. It is, instead, an explicit directive to LLVM to not attempt to propagate information about the function body outside of the function, including by changing the

I'm going to show the same function, first normally, and then as a coroutine, and show how gdb can see the variable when it's a normal function, but not when it's a coroutine. I'd like to understand if this can be improved. I'm trying to debug a real world problem, but the lack of debug info on variables in coroutines is making it difficult. Should I file a bug? Is this a

That all makes sense. I don't think the name "synthetic" is all that intuitive, though. Enum attributes are pretty cheap, maybe we should try to use a name closer to what we're trying to implement? For example, we could add a new "coroutine_foo" attribute for every coroutine style we implement. We would have analysis helper functions to answer questions like "is

Hello all, It's been a month since my previous email on the topic, and since then I've done some initial work on porting the coroutines passes to the new pass manager. In total there are 6 patches -- that's a lot to review, so allow me to introduce the changes being made in each of them. # What's finished In these first 6 patches, I focused on lowering coroutine intrinsics