Hi, Sergey!
Thanks for the patch!
Please consider my comments below.
> 
>>From: Mike Pall <mike>
>>
>>Thanks to Peter Cawley.
>>
>>(cherry picked from commit 05fbdf565c700365d22e38f11478101a0d92a23e)
>>
>>To reproduce the issue we need to assemble `IR_SLOAD` with
>>`IRSLOAD_TYPECHECK` flag set. Also, this IR shouldn't be used later and
>>be not pri, not any number, not any integer type. For GC64 mode, we get
>>the following mcode for this typecheck only variant of the IR:
>>
>>| 55557f6bffc9 mov rdi, [rdx+0x4]
>>| 55557f6bffcd sar rdi, 0x2f
>>| 55557f6bffd1 cmp edi, -0x0b
>>| 55557f6bffd4 jnz 0x55557f6b0010 ->0
>>
>>This 0x4 addition is excess and 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 patch removes this addition.
>>
>>Sergey Kaplun:
>>* added the description and the test for the problem
>>
>>Part of tarantool/tarantool#7230
>>---
>>
>>Branch:  https://github.com/tarantool/luajit/tree/skaplun/lj-350-fix-sload-typecheck-full-ci
>>Issues:
>>*  https://github.com/tarantool/tarantool/issues/7230
>>*  https://github.com/LuaJIT/LuaJIT/pull/350
>>Tarantool PR:  https://github.com/tarantool/tarantool/pull/7995
>>
>> src/lj_asm_x86.h | 2 +-
>> .../lj-350-sload-typecheck.test.lua | 42 +++++++++++++++++++
>> .../lj-408-tonumber-cdata-record.test.lua | 10 -----
>> 3 files changed, 43 insertions(+), 11 deletions(-)
>> create mode 100644 test/tarantool-tests/lj-350-sload-typecheck.test.lua
>>
>>diff --git a/src/lj_asm_x86.h b/src/lj_asm_x86.h
>>index 8a4d4025..8efda8e5 100644
>>--- a/src/lj_asm_x86.h
>>+++ b/src/lj_asm_x86.h
>>@@ -1759,7 +1759,7 @@ static void asm_sload(ASMState *as, IRIns *ir)
>>       emit_i8(as, irt_toitype(t));
>>       emit_rr(as, XO_ARITHi8, XOg_CMP, tmp);
>>       emit_shifti(as, XOg_SAR|REX_64, tmp, 47);
>>- emit_rmro(as, XO_MOV, tmp|REX_64, base, ofs+4);
>>+ emit_rmro(as, XO_MOV, tmp|REX_64, base, ofs);
>> #else
>>     } else {
>>       emit_i8(as, irt_toitype(t));
>>diff --git a/test/tarantool-tests/lj-350-sload-typecheck.test.lua b/test/tarantool-tests/lj-350-sload-typecheck.test.lua
>>new file mode 100644
>>index 00000000..6ffc61fb
>>--- /dev/null
>>+++ b/test/tarantool-tests/lj-350-sload-typecheck.test.lua
>>@@ -0,0 +1,42 @@
>>+local tap = require('tap')
>>+local traceinfo = require('jit.util').traceinfo
>>+
>>+-- Test file to demonstrate the incorrect GC64 JIT asembling
>>+-- `IR_SLOAD`.
>>+-- See also  https://github.com/LuaJIT/LuaJIT/pull/350 .
>>+local test = tap.test('lj-350-sload-typecheck')
>>+
>>+test:plan(1)
>>+
>>+-- Contains only IR_SLOAD after recording.
>>+local function sload(arg)
>>+ return arg
>>+end
>>+
>>+local tab_arg = {}
>>+
>>+-- Reset JIT, remove any other traces.
>>+jit.off()
>>+jit.flush()
>>+
>>+assert(not traceinfo(1), 'no traces compiled after flush')
>>+
>>+-- Try to executed compiled trace wiht IR_SLOAD, if emitted mcode
>Typo: s/to executed/to execute
>Typo: s/wiht/with
>Typo: s/if emitted/if the emmited
>>+-- is incorrect, assertion guard type check will failed even for
>Typo: s/failed/fail
>Typo: s/for/ for the
>>+-- correct type of argument and a new trace is recorded.
>>+jit.opt.start('hotloop=1', 'hotexit=1')
>>+
>>+jit.on()
>>+
>>+-- Make the function hot.
>>+sload(tab_arg)
>>+-- Compile the trace.
>>+sload(tab_arg)
>>+-- Execute trace and try to compile a trace from the side exit.
>>+sload(tab_arg)
>>+
>>+jit.off()
>>+
>>+test:ok(not traceinfo(2), 'the second trace should not be compiled')
>>+
>>+os.exit(test:check() and 0 or 1)
>Also, that test passes even without the patch on Linux x86_64 GC64: OFF
>>diff --git a/test/tarantool-tests/lj-408-tonumber-cdata-record.test.lua b/test/tarantool-tests/lj-408-tonumber-cdata-record.test.lua
>>index bf9e8e46..a8235e93 100644
>>--- a/test/tarantool-tests/lj-408-tonumber-cdata-record.test.lua
>>+++ b/test/tarantool-tests/lj-408-tonumber-cdata-record.test.lua
>>@@ -6,7 +6,6 @@ local tap = require('tap')
>> -- conversions.
>> -- See also  https://github.com/LuaJIT/LuaJIT/issues/408 ,
>> --  https://github.com/LuaJIT/LuaJIT/pull/412 ,
>>---  https://github.com/LuaJIT/LuaJIT/pull/412 ,
>> --  https://github.com/tarantool/tarantool/issues/7655 .
>> local test = tap.test('lj-408-tonumber-cdata-record')
>> 
>>@@ -14,15 +13,6 @@ local NULL = ffi.cast('void *', 0)
>> 
>> test:plan(4)
>> 
>>--- This test won't fail for GC64 on x86_64. This happens due to
>>--- wrong instruction emitting for SLOAD IR -- we always exit by
>>--- the assertion guard on the argument type check. See also
>>---  https://github.com/LuaJIT/LuaJIT/pull/350 .
>>--- The test fails without fix in the current commit, if the
>>--- following commit is backported:
>>---  https://github.com/LuaJIT/LuaJIT/commit/05fbdf56
>>--- Feel free to remove this comment after backporting of the
>>--- aforementioned commit.
>> local function check(x)
>>   -- Don't use a tail call to avoid "leaving loop in root trace"
>>   -- error, so the trace will be compiled.
>>--
>>2.34.1
>--
>Best regards,
>Maxim Kokryashkin