Re: [Tarantool-patches] [PATCH luajit 2/2] DUALNUM: Fix recording of loops broken by previous change.

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

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Hi, Sergey,

thanks for the patch! LGTM

Sergey

On 3/12/26 18:55, Sergey Kaplun wrote:
> From: Mike Pall <mike>
>
> Thanks to Nicholas Davies.
>
> (cherry picked from commit 1c3b5a4d722598ecbb9219480142eda682e87bb1)
>
> The previous commit forbids recording for the NaN control variables
> stack slots. These checks are false positives for integers in DUALNUM
> mode. This prevents any for loop with integers as slots from being
> recorded.
>
> This patch fixes the checks.
>
> Sergey Kaplun:
> * added the description and the test for the problem
>
> Part of tarantool/tarantool#12134
> ---
>   src/lj_record.c                               |  6 ++---
>   .../lj-1438-jit-for-canary.test.lua           | 22 +++++++++++++++++++
>   2 files changed, 25 insertions(+), 3 deletions(-)
>   create mode 100644 test/tarantool-tests/lj-1438-jit-for-canary.test.lua
>
> diff --git a/src/lj_record.c b/src/lj_record.c
> index a3a68b57..dbfc7f47 100644
> --- a/src/lj_record.c
> +++ b/src/lj_record.c
> @@ -510,9 +510,9 @@ static LoopEvent rec_for(jit_State *J, const BCIns *fori, int isforl)
>     TRef stop;
>     IRType t;
>     /* Avoid semantic mismatches and always failing guards. */
> -  if (tvisnan(&tv[FORL_IDX]) ||
> -      tvisnan(&tv[FORL_STOP]) ||
> -      tvisnan(&tv[FORL_STEP]) ||
> +  if ((tvisnum(&tv[FORL_IDX]) && tvisnan(&tv[FORL_IDX])) ||
> +      (tvisnum(&tv[FORL_STOP]) && tvisnan(&tv[FORL_STOP])) ||
> +      (tvisnum(&tv[FORL_STEP]) && tvisnan(&tv[FORL_STEP])) ||
>         tvismzero(&tv[FORL_STEP]))
>       lj_trace_err(J, LJ_TRERR_GFAIL);
>     if (isforl) {  /* Handle FORL/JFORL opcodes. */
> diff --git a/test/tarantool-tests/lj-1438-jit-for-canary.test.lua b/test/tarantool-tests/lj-1438-jit-for-canary.test.lua
> new file mode 100644
> index 00000000..4b67df4c
> --- /dev/null
> +++ b/test/tarantool-tests/lj-1438-jit-for-canary.test.lua
> @@ -0,0 +1,22 @@
> +local tap = require('tap')
> +
> +-- The test file to check the correct recording of the for loop.
> +-- Used as a canary test, since we have none.
> +-- See alsohttps://github.com/LuaJIT/LuaJIT/issues/1438.
> +
> +local test = tap.test('lj-1438-jit-for-canary'):skipcond({
> +  ['Test requires JIT enabled'] = not jit.status(),
> +})
> +
> +test:plan(1)
> +
> +local traceinfo = require('jit.util').traceinfo
> +
> +jit.flush()
> +jit.opt.start('hotloop=1')
> +
> +for _ = 1, 4 do end
> +
> +test:ok(traceinfo(1), 'simple for loop is recorded')
> +
> +test:done(true)

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