[PATCH] Big update to Kaleidoscope tutorials.

Tue Aug 25 20:17:19 PDT 2015

Hi Philip,

This change is to the Kaleidoscope docs only, and those are fairly fundamentally broken in LLVM 3.7 as it stands: The code for chapter 4 is convoluted, and doesn't match the docs. The code for chapter 5 and beyond doesn't work properly.

While I didn't originally plan for this to go in to 3.7, and I'm not personally invested in seeing it make it in, I think it's a big improvement for very little risk. I'm currently sanity checking this patch (plus the c++11 and clang-format prerequisites) on the release branch. If it passes everything I'd be inclined to take it.

Did you have any particular points of concern, or were you just applying the usual high bar for late changes to the release branch? 

Cheers,
Lang.

> On Tuesday, August 25, 2015, Philip Reames via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>> On 08/25/2015 05:39 PM, Andy Somogyi via llvm-commits wrote:
>> I think this should go in the 3.7 release.
> I disagree.  I'd be fine with a forward reference (e.g. "This document is out of date, we suggest you read the one for ToT."), but this would be a large change to make at the last minute.  
>> 
>> The kaleidoscope tutorials have been broken for a long time, ever since the removal of the regular JIT, and nearly everyone I know used the Kaleidoscope tutorials to learn LLVM, they are a very good resource and they simply should work.  
>> 
>> Sent from my iPad
>> 
>> On Aug 25, 2015, at 6:35 PM, Eric Christopher via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>> 
>>> This looks pretty great.
>>> 
>>> Couple of comments:
>>> 
>>> Man, would the renaming have been nice to do before/after :)
>>> 
>>> +simple: The KaleidoscopeJIT has a straigtforward symbol resolution rule that
>>> 
>>> Typo.
>>> 
>>> Any reason not to have the KaleidoscopeJIT file in the tutorial?
>>> 
>>> +      : TM(EngineBuilder().selectTarget()), DL(TM->createDataLayout()),
>>> 
>>> As far as the data layout, this hurts. Can we get it from the module at use time?
>>> 
>>> Otherwise LGTM and hopefully we can just pull this into 3.7 if we have another RC. Otherwise we probably want to hold off?
>>> 
>>> -eric
>>> 
>>> 
>>>> On Tue, Aug 25, 2015 at 2:01 PM Lang Hames <lhames at gmail.com> wrote:
>>>> Hi All,
>>>> 
>>>> As some of you have noticed, Kaleidoscope has had some issues since we removed the legacy JIT last year. The tutorial code had been relying on the behavior of the legacy JIT, and the switch to MCJIT caused many simple use-cases to break (e.g. repeat calls to functions). Kaleidoscope Chapter 4, which introduces JIT support, had been largely fixed by taking some of the code from Andy Kaylor's Kaleidoscope/MCJIT tutorials, but this added a lot of engineering detail to what was supposed to be a beginner's tutorial. The later chapters were never updated.
>>>> 
>>>> The attached patch fixes this situation by updating all of the Kaleidoscope tutorials to use a new, custom, ORC-based JIT: KaleidoscopeJIT. By using this instead of MCJIT, all of the original Kaleidoscope functionality is restored, and we actually do a better job of behaving like a REPL (for example, functions can be redefined). Assuming this patch is accepted, in the near future I hope to add one or two new chapters to Kaleidoscope that involve modifying the KaleidoscopeJIT to support lazy compilation (This will mostly involve merging code from the Kaleidoscope/Orc tutorials).
>>>> 
>>>> Most of this patch is concerned with the switch to KaleidoscopeJIT and corresponding updates to the documentation. In particular, Chapter 4 has been substantially updated. There is also a little bit of C++11 modernization and general cleanup.
>>>> 
>>>> All comments welcome. If anyone would like to road-test the new tutorials I'd be particularly interested to hear feedback on that. 
>>>> 
>>>> Cheers,
>>>> Lang.
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