Re: [Tarantool-patches] [PATCH] jit: fix cdatanum addressing for GC64 mode on x86

[Kirill Yukhin <kyukhin@tarantool.org>]

Hello,

On 14 окт 16:53, Igor Munkin wrote:
> This patch fixes the regression introduced in scope of
> 5f6775ae0e141422193ad9b492806834064027ca ('core: introduce various
> platform metrics'). As a result of the patch <cdatanum> displacement is
> misencoded when GC64 mode is enabled.
> 
> In X86 long mode 32-bit displacement is encoded either via SIB byte or
> is addressed relatively to RIP register value. The first approach is
> used in JIT for 32-bit addresses (i.e. when GC64 mode is disabled), but
> doesn't work for 64-bit ones. As a result all addresses to GG_State
> contents to be "hardcoded" on the trace are encoded relatively to
> RID_DISPATCH register (i.e. callee-safe R14 register) containing global
> dispatch table. For this purpose this register is not used by the JIT
> register allocator in GC64 build and not spoiled throughout LuaJIT VM
> cycle (and therefore trace execution).
> 
> NB: Since R14 is the additional GRP, the <add> instruction ought to be
> REX-prefixed.
> 
> Follows up tarantool/tarantool#5187
> 
> Reported-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
> Signed-off-by: Igor Munkin <imun@tarantool.org>

I've checked your patch into 1.10, 2.4, 2.5 and master.

--
Regards, Kirill Yukhin