[Tarantool-patches] [PATCH luajit 17/19] MIPS64: Fix register allocation in assembly of HREF.

[Sergey Bronnikov]

Hi, Sergey!


Thanks for the patch!

Test is passed after reverting the patch.


On 8/9/23 18:36, Sergey Kaplun wrote:
> From: Mike Pall <mike>
>
> Contributed by James Cowgill.
>
> (cherry-picked from commit 99cdfbf6a1e8856f64908072ef10443a7eab14f2)
>
> The issue is observed for the following merged IRs:
> |    p64 HREF   0001  "a"            ; or other keys
> | >  p64 EQ     0002  [0x4002d0c528] ; nilnode
> Sometimes, when we need to rematerialize a constant during evicting of
> the register. So, the instruction related to constant rematerialization
> is placed in the delay branch slot, which suppose to contain the loads
> of trace exit number to the `$ra` register. The resulting assembly is
> the following (for example):
> | beq     ra, r1, 0x400abee9b0  ->exit
> | lui     r1, 65531   ; delay slot without setting of the `ra`
> This leading to the assertion failure during trace exit in
> `lj_trace_exit()`, since a trace number is incorrect.
>
> This patch moves the constant register allocations above the main
> instruction emitting code in `asm_href()`.
>
> Sergey Kaplun:
> * added the description and the test for the problem

Test is passed after reverting the patch. LuaJIT was built with and 
without GC64.


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