[Tarantool-patches] [PATCH luajit] FFI: Add tonumber() specialization for failed conversions.
sergos
sergos at tarantool.org
Mon Sep 26 00:37:31 MSK 2022
Since we fallback to interpreter it looks safe to keep the test for GC64.
Still you’d better mention it in commit message.
LGTM with above.
Sergos
> On 22 Sep 2022, at 14:28, Sergey Kaplun <skaplun at tarantool.org> wrote:
>
> Hi, Sergos!
>
> On 21.09.22, sergos wrote:
>> Hi!
>>
>> I see four ‘ok’s as a result of run.
>> See the full output for the run with dump() below:
>>
>>
>> s.ostanevich at s-ostanevich2:~/workspaces/t.sergos/third_party/luajit/test/tarantool-tests % ../../../../build-debug/src/tarantool -e 'require"jit.dump".start("ib")' lj-408-tonumber-cdata-record.test.lua
>>
>> TAP version 13
>> 1..4
>> ---- TRACE 1 start lj-408-tonumber-cdata-record.test.lua:17
>> 0001 GGET 1 0 ; "tonumber"
>> 0002 MOV 3 0
>> 0003 CALL 1 2 2
>> 0000 . FUNCC ; tonumber
>> 0004 RET1 1 2
>> ---- TRACE 1 IR
>> 0001 fun SLOAD #0 R
>> 0002 tab FLOAD 0001 func.env
>> 0003 int FLOAD 0002 tab.hmask
>> 0004 > int EQ 0003 +63
>> 0005 p64 FLOAD 0002 tab.node
>> 0006 > p64 HREFK 0005 "tonumber" @8
>> 0007 > fun HLOAD 0006
>> 0008 > cdt SLOAD #2 T
>> 0009 > fun EQ 0007 tonumber
>> ---- TRACE 1 stop -> return
>
> Gotcha!
> It's a funny thing:
> This is happening due to GC64 mode on x86_x64.
>
> There is an invalid type check for SLOAD IR with the following emitted
> mcode:
>
> | 55557f6bffc9 mov rdi, [rdx+0x4]
> | 55557f6bffcd sar rdi, 0x2f
> | 55557f6bffd1 cmp edi, -0x0b
> | 55557f6bffd4 jnz 0x55557f6b0010 ->0
>
> This 0x4 addiction is crucial:
> We got the invalid irtype value to compare (due wrong addressing) -- so
> the assertion guard is always failed and we always exit from the trace.
> This is why we fallback into the interpreter and the test is passed.
>
> In LuaJIT upstream this issue fixed via the following commit:
> https://github.com/LuaJIT/LuaJIT/commit/05fbdf56 <https://github.com/LuaJIT/LuaJIT/commit/05fbdf56>
>
> See also https://github.com/LuaJIT/LuaJIT/pull/350 <https://github.com/LuaJIT/LuaJIT/pull/350>
>
> <snipped>
>
>>
>
> --
> Best regards,
> Sergey Kaplun
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