Re: [Tarantool-patches] [PATCH luajit] LJ_GC64: Fix ir_khash for non-string GCobj.

[Igor Munkin via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Sergey,

I've checked the patches into all long-term branches in tarantool/luajit
and bumped a new version in master, 2.10 and 1.10.

On 08.12.22, Sergey Kaplun via Tarantool-patches wrote:
> From: Mike Pall <mike>
> 
> Contributed by Peter Cawley.
> 
> (cherry picked from commit b4ed3219a1a98dd9fe7d1e3eeea3b82f5a780948)
> 
> When emitting `IR_HREF` for constant value to lookup the `ir_khash()`
> function is used to calculate hash for the corresponding object.
> This calculation must be the same as in the corresponding `hashkey()`
> function from <lj_tab.c>.
> 
> Hash calculating via passing two arguments `lo`, and `hi` to `hashrot()`
> routine. For non-string GC objects the first `lo` argument is the same
> for GC64 and not GC64 mode -- lower 32 bits of the object address. For
> GC64 mode `hi` argument is upper 32 bits of the object address,
> including specific type NaN-tag. This `hi` argument in `ir_khash()`
> function is miscalculated in GC64 using non-GC64 value (`lo` +
> `HASH_BIAS`). As a result, the hash for the GC object is miscalculated
> on trace and we exit from trace due to assertion guard on the type or
> value check.
> 
> This patch fixes calculation of hash value on trace for GC64 mode by
> making it consistent with `hashkey()`.
> 
> 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-356-ir-khash-non-string-obj-full-ci
> Issue/PR:
> * https://github.com/tarantool/tarantool/issues/7230
> * https://github.com/LuaJIT/LuaJIT/pull/356
> Tarantool PR: https://github.com/tarantool/tarantool/pull/8020
> 
> Side note: Problems with red fuzzer jobs look irrelevant to the patch.
> 
>  src/lj_asm.c                                  |  4 +
>  .../lj-356-ir-khash-non-string-obj.test.lua   | 90 +++++++++++++++++++
>  2 files changed, 94 insertions(+)
>  create mode 100644 test/tarantool-tests/lj-356-ir-khash-non-string-obj.test.lua
> 

<snipped>

> -- 
> 2.34.1
> 

-- 
Best regards,
IM