[Tarantool-patches] [PATCH luajit] FFI: Add tonumber() specialization for failed conversions.
Sergey Kaplun
skaplun at tarantool.org
Thu Sep 22 14:28:11 MSK 2022
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
See also https://github.com/LuaJIT/LuaJIT/pull/350
<snipped>
>
--
Best regards,
Sergey Kaplun
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