Re: [Tarantool-patches] [PATCH luajit v1] Fix BC_UCLO insertion for returns.

[Maxim Kokryashkin via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

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Hi!
Thanks for the fixes!
A few CI jobs are red, please address them.
--
Best regards,
Maxim Kokryashkin
 
 
> 
>>Hi, Max!
>> 
>>Thanks for review! Added more comments to the test and commit message.
>>New changes force-pushed to the branch. Please take a look.
>> 
>>S.
>>On 6/7/23 14:35, Maxim Kokryashkin wrote:
>>>Hi, Sergey and Sergey!
>>> 
>>> 
>>>> 
>>>>>Hi, Sergey!
>>>>>Thanks for the patch!
>>>>>Please, consider my comments below.
>>>>>
>>>>>On 30.05.23, Sergey Bronnikov wrote:
>>>>>> From: Sergey Bronnikov < sergeyb@tarantool.org >
>>>>>>
>>>>>> Contributed by XmiliaH.
>>>>>>
>>>>>> (cherry-picked from commit 93a65d3cc263aef2d2feb3d7ff2206aca3bee17e)
>>>>>>
>>>>>> After emitting bytecode instruction BC_FNEW fixup is not required,
>>>>Typo: s/bytecode/the bytecode
>>Fixed, thanks!
>> 
>>>>>> because FuncState will set a flag PROTO_CHILD that will trigger emitting
>>>>>> a pair of instructions BC_UCLO and BC_RET (see <src/lj_parse.c:2355>)
>>>>>> and BC_RET will close all upvalues from base equal to 0.
>>>>>
>>>>>This part describes why replacing UCLO with FNEW is good enough and
>>>>>better than just deleting
>>>>>| case BC_UCLO: return;
>>>>>But the original problem is that some of BC_RET are not fixup-ed, due to
>>>>>early return, if UCLO is obtained before, those leads to VM
>>>>>inconsistency after return from the function. Please, mention this too.
>>>>Agree here, it is hard to get what the patch is about from that description,
>>>>without diving into the changes.
>>Added more details.
>>  <snipped>
>>>>>Also, before the patch I got the following assertion in JIT:
>>>>>
>>>>>| LUA_PATH="src/?.lua;;" src/luajit -Ohotloop=1 -e '
>>>>>|
>>>>>| local function missing_uclo()
>>>>>| while true do -- luacheck: ignore
>>>>>| local f
>>>>>| if false then break end
>>>>>| while true do
>>>>>| if f then
>>>>>| return f
>>>>>| end
>>>>>| f = function()
>>>>>| return f
>>>>>| end
>>>>>| end
>>>>>| end
>>>>>| end
>>>>>| f = missing_uclo()
>>>>>| print(f())
>>>>>| f = missing_uclo()
>>>>>| print(f())
>>>>>| '
>>>>>| 3.1002202036551
>>>>>| luajit: /home/burii/reviews/luajit/lj-819-missing-uclo/src/lj_record.c:135: rec_check_slots: Assertion `((((((tr))>>24) & IRT_TYPE) - (TRef)(IRT_NUM) <= (TRef)
>>>>>| (IRT_INT-IRT_NUM)))' failed.
>>>>>| Aborted
>>>>>
>>>>>I don't sure that we should test this particular failure too, since the
>>>>>origin of the problem is the incorrect emitted bytecode.
>>>>>
>>>>>Thoughts?
>>>>We should not, because it is most likely caused by the issue
>>>>that was fixed in the LuaJIT/LuaJIT@5c46f477.
>> 
>>assert in rec_check_slots could be for many reasons, so I added a testcase for compiler too.
>> 
>>>>>
>>>>>> --
>>>>>> 2.34.1
>>>>>>
>>>>>
>>>>>--
>>>>>Best regards,
>>>>>Sergey Kaplun
>>>>--
>>>>Best regards,
>>>>Maxim Kokryashkin
>>>> 
> 

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