[llvm-dev] kaleidoscope ch4 jit example regression?

Nick Desaulniers via llvm-dev llvm-dev at lists.llvm.org
Thu Feb 21 09:02:56 PST 2019

Just saw this (while looking for another patch).
Thanks! (Can we add a test so this part of kaleidoscope doesn't regress

On Wed, Feb 20, 2019, 4:50 PM Lang Hames <lhames at gmail.com> wrote:

> Ok. For the curious: The problem is that ORCv2 did away with symbol
> resolvers in favor of fixed symbol tables with resolution rules intended to
> match the static and dynamic linkers. That gave us a structure with which
> we could coordinate concurrent compilation, but took away our ability to
> arbitrarily hide old definitions (which is what we were relying on in the
> tutorial).
> In the short term I think we can hack around this by detecting symbol
> clashes (DuplicateDefinition errors) in the KaleidoscopeJIT class and
> starting a new JITDylib each time we see one: Duplicate symbols within a
> dylib are not allowed, but duplicate symbols in *different* dylibs are.
> Then we just search our dylibs from last to first when resolving.
> In the long term we would like a way to rename or delete symbol table
> entries (without deleting their underlying memory). This is probably still
> a little way off: deleting / renaming in the context of concurrent
> compilation is tricky.
> Cheers,
> Lang.
> On Wed, Feb 20, 2019 at 3:20 PM Lang Hames <lhames at gmail.com> wrote:
>> Not yet unfortunately. I've had my head down working on a jut-linker
>> replacement.
>> Let me take a look right now...
>> On Mon, Feb 18, 2019 at 10:40 AM David Blaikie <dblaikie at gmail.com>
>> wrote:
>>> Ping - did this end up getting addressed?
>>> On Mon, Jan 21, 2019, 6:15 PM Lang Hames <lhames at gmail.com wrote:
>>>> Hi Nick,
>>>> I was not aware of it, but it makes sense given the recent switch to
>>>> ORC2, which has different symbol resolution rules.
>>>> I am out on vacation this week, but will take a look when I get back
>>>> and see if I can restore the old behavior.
>>>> Cheers,
>>>> Lang.
>>>> Sent from my iPhone
>>>> On Jan 20, 2019, at 2:14 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>>> +Lang who does JIT things
>>>> Yeah, I can confirm my local build (using LLVM source from today) of
>>>> Chapter 4 behaves as you describe, and not as the documentation shows.
>>>> Looks like somethnig needs updating (either source or the documentation).
>>>> On Sun, Dec 30, 2018 at 3:28 PM Nick Desaulniers via llvm-dev <
>>>> llvm-dev at lists.llvm.org> wrote:
>>>>> https://llvm.org/docs/tutorial/LangImpl04.html has an example where
>>>>> the function `foo` gets redefined, and the JIT returns evaluation of
>>>>> the latest definition.  I thought my code was wrong, but it seems that
>>>>> the binary produced by `ninja Kaleidoscope-Ch4` has the same bug.
>>>>> Granted, my LLVM checkout is from Nov 3 2018 (r346062).  Is this a
>>>>> known issue?
>>>>> ~Nick Desaulniers
>>>>> _______________________________________________
>>>>> LLVM Developers mailing list
>>>>> llvm-dev at lists.llvm.org
>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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