https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68785
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #3)
> So it folds
>
> # VUSE <.MEM_30>
> # rhs access alignment 32+0
> _92 = MEM[(u32 *)path_7];
>
> but path_7 is know to point to "". location of the stmt above is
> drivers/acpi/acpica/nsaccess.c:562:36 I guess that's
>
> *(u32 *)(void *)(&simple_name) = *(u32 *)(void *)(path);
>
> eventually jump-threaded from the
>
> if (!pathname) {
>
>
>
> num_segments = 0;
> this_node = acpi_gbl_root_node;
> path = "";
>
> case . Yeah, quite obvious.
>
> We avoid doing the work to zero the "undefined" area given the program does
> not invoke undefined behavior only if the uninitialized bits of the result
> are not used (like masked out or so).
>
> One could silence valgrind with some annotation I guess.
>
> Patch to make it trigger as ICE:
>
> Index: gcc/gimple-fold.c
> ===================================================================
> --- gcc/gimple-fold.c (revision 231355)
> +++ gcc/gimple-fold.c (working copy)
> @@ -5495,9 +5492,13 @@ fold_ctor_reference (tree type, tree cto
> && size <= MAX_BITSIZE_MODE_ANY_MODE)
> {
> unsigned char buf[MAX_BITSIZE_MODE_ANY_MODE / BITS_PER_UNIT];
> - if (native_encode_expr (ctor, buf, size / BITS_PER_UNIT,
> - offset / BITS_PER_UNIT) > 0)
> - return native_interpret_expr (type, buf, size / BITS_PER_UNIT);
> + int elen;
> + if ((elen = native_encode_expr (ctor, buf, size / BITS_PER_UNIT,
> + offset / BITS_PER_UNIT)) > 0)
> + {
> + gcc_assert (elen >= size / BITS_PER_UNIT);
> + return native_interpret_expr (type, buf, size / BITS_PER_UNIT);
> + }
> }
> if (TREE_CODE (ctor) == CONSTRUCTOR)
> {
Looks like the bug is right here (and in tree-ssa-sccvn.c) too.
The interfaces are really meant to be used the way fold_view_convert_expr uses
them, i.e. that native_interpret_expr is called with the length returned by
native_encode_expr. Will try to reduce the testcase and write a patch.
