https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105769
--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #17)
> I'm not actually seeing the problematic use of the hoisted address - the
> address value itself is stored and the trick of looking at SSA uses defs to
> pick up
> indirect address uses later doesn't work here as the only use is in the
> vector CTOR:
>
> _15 = (long unsigned int) &bias;
> _10 = (long unsigned int) &cov_jn;
> _12 = {_10, _15};
> ...
> bias ={v} {CLOBBER(bob)};
>
> but _12 is only used in
>
> MEM <vector(2) long unsigned int> [(void *)&D.5715 + 32B] = _12;
>
> and then maybe indirectly
>
> __ct_comp (_14, &D.5715.__est);
>
> I can fix the miscompile with the following patch - we're treating all
> CLOBBER kinds as invalidating earlier mentions. I'm not sure that's
> really necessary and it's definitely harmful when there are hoisted
> address mentions. It also explains that -fstack-reuse=none doesn't
> help as the gimplifier only inserts CLOBBER_STORAGE_END clobbers.
> I'm also allowing CLOBBER_OBJECT_END here.
>
> I do not remember whether we discussed doing sth like this instead of the
> special SSA use handling we added?
>
> diff --git a/gcc/cfgexpand.cc b/gcc/cfgexpand.cc
> index eef565eddb5..92968075b04 100644
> --- a/gcc/cfgexpand.cc
> +++ b/gcc/cfgexpand.cc
> @@ -632,6 +632,13 @@ add_scope_conflicts_1 (basic_block bb, bitmap work,
> bool for_conflict)
> that are COMPONENT_REFs. */
> if (!VAR_P (lhs))
> continue;
> + tree cl = gimple_assign_rhs1 (stmt);
> + /* When the clobber is possibly a object/storage start do not
> + ignore previous mentions at this point. Those might
> + include hoisted address uses. */
> + if (CLOBBER_KIND (cl) != CLOBBER_STORAGE_END
> + && CLOBBER_KIND (cl) != CLOBBER_OBJECT_END)
> + continue;
> if (DECL_RTL_IF_SET (lhs) == pc_rtx
> && (v = decl_to_stack_part->get (lhs)))
> bitmap_clear_bit (work, *v);
It breaks g++.dg/opt/pr86214-1.C and gcc.target/i386/stack-check-17.c
