Re: [Qemu-devel] [PATCH v2 2/2] target/m68k: add a mechanism to automatically free TCGv

[Richard Henderson]

On 03/19/2018 07:35 PM, Laurent Vivier wrote:
> SRC_EA() and gen_extend() can return either a temporary
> TCGv or a memory allocated one. Mark them when they are
> allocated, and free them automatically at end of the
> instruction translation.
> 
> We want to free locally allocated TCGv to avoid
> overflow in sequence like:
> 
>   0xc00ae406:  movel %fp@(-132),%fp@(-268)
>   0xc00ae40c:  movel %fp@(-128),%fp@(-264)
>   0xc00ae412:  movel %fp@(-20),%fp@(-212)
>   0xc00ae418:  movel %fp@(-16),%fp@(-208)
>   0xc00ae41e:  movel %fp@(-60),%fp@(-220)
>   0xc00ae424:  movel %fp@(-56),%fp@(-216)
>   0xc00ae42a:  movel %fp@(-124),%fp@(-252)
>   0xc00ae430:  movel %fp@(-120),%fp@(-248)
>   0xc00ae436:  movel %fp@(-12),%fp@(-260)
>   0xc00ae43c:  movel %fp@(-8),%fp@(-256)
>   0xc00ae442:  movel %fp@(-52),%fp@(-276)
>   0xc00ae448:  movel %fp@(-48),%fp@(-272)
>   ...
> 
> That can fill a lot of TCGv entries in a sequence,
> especially since 15fa08f845 ("tcg: Dynamically allocate TCGOps")
> we have no limit to fill the TCGOps cache and we can fill
> the entire TCG variables array and overflow it.
> 
> Suggested-by: Richard Henderson <address@hidden>
> Signed-off-by: Laurent Vivier <address@hidden>
> ---
>  target/m68k/translate.c | 56 
> +++++++++++++++++++++++++++++++++++++------------
>  1 file changed, 43 insertions(+), 13 deletions(-)

Reviewed-by: Richard Henderson <address@hidden>


r~