Re: [Tarantool-patches] [PATCH luajit] DUALNUM: Add missing type conversion for FORI slots.

[Sergey Bronnikov via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

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Hi, Sergey,

thanks for the patch!

The bug cannot be reproduced with reverted fix.

CMake: cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug -DLUAJIT_NUMMODE=2


Sergey

On 3/2/26 11:14, Sergey Kaplun wrote:
> From: Mike Pall <mike>
>
> Reported by Sergey Kaplun.
>
> (cherry picked from commit 406cf69b3ae0a3ecd5ede2bb97b937b7a5d92074)
>
> `rec_for_loop()` narrows the FORL index values by getting them from the
> runtime. In case when the `start`, `stop`, `step` control variables are
> already loaded to the slots, their TRef isn't converted to the
> corresponding type. This leads to the following inconsistent IR dump and
> to the assertion failure later:
> | 0002 > int SLOAD  10   TCI
> | 0003   int ADD    0002  +1.
> | 0004 > int LE     0003  +1.
> | 0005   int ADD    0003  +1.
> | 0006 > int GT     0005  +1.
>
> This patch adds the missing type conversion.
>
> Sergey Kaplun:
> * added the description and the test for the problem
>
> Part of tarantool/tarantool#12134
> ---
>
> Branch:https://github.com/tarantool/luajit/tree/skaplun/lj-1413-missing-conv-fori
> Related issues:
> *https://github.com/LuaJIT/LuaJIT/issues/1413
> *https://github.com/tarantool/tarantool/issues/12134
>
>   src/lj_record.c                               | 25 +++++++----
>   .../lj-1413-missing-conv-fori.test.lua        | 43 +++++++++++++++++++
>   2 files changed, 60 insertions(+), 8 deletions(-)
>   create mode 100644 test/tarantool-tests/lj-1413-missing-conv-fori.test.lua
>
> diff --git a/src/lj_record.c b/src/lj_record.c
> index ba409a61..abb6334a 100644
> --- a/src/lj_record.c
> +++ b/src/lj_record.c
> @@ -365,12 +365,27 @@ static TRef fori_load(jit_State *J, BCReg slot, IRType t, int mode)
>   		mode + conv);
>   }
>   
> +/* Convert FORI argument to expected target type. */
> +static TRef fori_conv(jit_State *J, TRef tr, IRType t)
> +{
> +  if (t == IRT_INT) {
> +    if (!tref_isinteger(tr))
> +      return emitir(IRTGI(IR_CONV), tr, IRCONV_INT_NUM|IRCONV_CHECK);
> +  } else {
> +    if (!tref_isnum(tr))
> +      return emitir(IRTN(IR_CONV), tr, IRCONV_NUM_INT);
> +  }
> +  return tr;
> +}
> +
>   /* Peek before FORI to find a const initializer. Otherwise load from slot. */
>   static TRef fori_arg(jit_State *J, const BCIns *fori, BCReg slot,
>   		     IRType t, int mode)
>   {
>     TRef tr = J->base[slot];
> -  if (!tr) {
> +  if (tr) {
> +    tr = fori_conv(J, tr, t);
> +  } else {
>       tr = find_kinit(J, fori, slot, t);
>       if (!tr)
>         tr = fori_load(J, slot, t, mode);
> @@ -517,13 +532,7 @@ static LoopEvent rec_for(jit_State *J, const BCIns *fori, int isforl)
>         lj_assertJ(tref_isnumber_str(tr[i]), "bad FORI argument type");
>         if (tref_isstr(tr[i]))
>   	tr[i] = emitir(IRTG(IR_STRTO, IRT_NUM), tr[i], 0);
> -      if (t == IRT_INT) {
> -	if (!tref_isinteger(tr[i]))
> -	  tr[i] = emitir(IRTGI(IR_CONV), tr[i], IRCONV_INT_NUM|IRCONV_CHECK);
> -      } else {
> -	if (!tref_isnum(tr[i]))
> -	  tr[i] = emitir(IRTN(IR_CONV), tr[i], IRCONV_NUM_INT);
> -      }
> +      tr[i] = fori_conv(J, tr[i], t);
>       }
>       tr[FORL_EXT] = tr[FORL_IDX];
>       stop = tr[FORL_STOP];
> diff --git a/test/tarantool-tests/lj-1413-missing-conv-fori.test.lua b/test/tarantool-tests/lj-1413-missing-conv-fori.test.lua
> new file mode 100644
> index 00000000..ba1fa74a
> --- /dev/null
> +++ b/test/tarantool-tests/lj-1413-missing-conv-fori.test.lua
> @@ -0,0 +1,43 @@
> +local tap = require('tap')
> +
> +-- Test file to demonstrate LuaJIT incorrect recording of FORI
> +-- bytecode in the DUALNUM mode.
> +-- See also:https://github.com/LuaJIT/LuaJIT/issues/1413.
> +
> +local test = tap.test('lj-1413-missing-conv-fori'):skipcond({
> +  ['Test requires JIT enabled'] = not jit.status(),
> +})
> +
> +test:plan(1)
> +
> +local function always_number(val)
> +  -- Trace 3 starts as a side trace for the first one.
> +  return tonumber(val) or 1
> +end
> +
> +jit.opt.start('hotloop=1', 'hotexit=1')
> +
> +-- Compile the root trace with stitching.
> +always_number()
> +always_number('')
> +
> +-- An additional loop to evidentiate the issue for x86 arch in the
> +-- DUALNUM mode.
> +for _ = 1, 2 do
> +  -- Use '%' to force number slots.
> +  for i = always_number(9 % 1), 1 do
> +    -- The resulting IR for the trace 4 is the following:
> +    -- | 0002 > int SLOAD  10   TCI
> +    -- | 0003   int ADD    0002  +1.
> +    -- | 0004 > int LE     0003  +1.
> +    -- | 0005   int ADD    0003  +1.
> +    -- | 0006 > int GT     0005  +1.
> +    --
> +    -- The problem is within the type mismatch between the result
> +    -- type and the right operand in the IRs.
> +    for _ = '9' % i, always_number('') do end -- Trace 4.
> +  end
> +end
> +
> +test:ok(true, 'no assertion failure')
> +test:done(true)

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