On Thu, 28 Sep 2023, Sergei Trofimovich wrote:
> From: Sergei Trofimovich <siarh...@google.com>
>
> There are 3 GC root tables:
>
> gt_ggc_rtab
> gt_ggc_deletable_rtab
> gt_pch_scalar_rtab
>
> `deletable` and `scalar` tables are both simple: each element always
> contains a pointer to the beginning of the object and it's size is the
> full object.
>
> `rtab` is different: it's `base` is a pointer in the middle of the
> struct and `stride` points to the next GC pointer in the array.
>
> Before the change there were 2 problems:
>
> 1. We memset()ed not just pointers but data around them.
> 2. We wen out of bounds of the last object described by gt_ggc_rtab
> and triggered bootstrap failures in profile and asan bootstraps.
>
> After the change we handle only pointers themselves like the rest of
> ggc-common.cc code.
OK/
Thanks,
Richard.
> gcc/
> PR/111505
> * ggc-common.cc (ggc_zero_out_root_pointers): New helper.
> * ggc-common.cc (ggc_common_finalize): Use helper instead of
> memset() to wipe out pointers.
> ---
> gcc/ggc-common.cc | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/gcc/ggc-common.cc b/gcc/ggc-common.cc
> index 95803fa95a1..39e2581affd 100644
> --- a/gcc/ggc-common.cc
> +++ b/gcc/ggc-common.cc
> @@ -75,6 +75,18 @@ ggc_mark_root_tab (const_ggc_root_tab_t rt)
> (*rt->cb) (*(void **) ((char *)rt->base + rt->stride * i));
> }
>
> +/* Zero out all the roots in the table RT. */
> +
> +static void
> +ggc_zero_rtab_roots (const_ggc_root_tab_t rt)
> +{
> + size_t i;
> +
> + for ( ; rt->base != NULL; rt++)
> + for (i = 0; i < rt->nelt; i++)
> + (*(void **) ((char *)rt->base + rt->stride * i)) = (void*)0;
> +}
> +
> /* Iterate through all registered roots and mark each element. */
>
> void
> @@ -1307,8 +1319,7 @@ ggc_common_finalize ()
> memset (rti->base, 0, rti->stride * rti->nelt);
>
> for (rt = gt_ggc_rtab; *rt; rt++)
> - for (rti = *rt; rti->base != NULL; rti++)
> - memset (rti->base, 0, rti->stride * rti->nelt);
> + ggc_zero_rtab_roots (*rt);
>
> for (rt = gt_pch_scalar_rtab; *rt; rt++)
> for (rti = *rt; rti->base != NULL; rti++)
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
