https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113576
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rsandifo at gcc dot gnu.org
--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Hongtao Liu from comment #8)
> maybe
>
> diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
> index 1fd957288d4..6d321f9baef 100644
> --- a/gcc/fold-const.cc
> +++ b/gcc/fold-const.cc
> @@ -8035,6 +8035,9 @@ native_encode_vector_part (const_tree expr, unsigned
> char *ptr, int len,
> unsigned int extract_elts = extract_bytes * elts_per_byte;
> for (unsigned int i = 0; i < extract_elts; ++i)
> {
> + /* Don't encode any bit beyond the range of the vector. */
> + if (first_elt + i > count)
> + break;
Hmm. I think that VECTOR_CST_ELT should have ICEd for out-of-bound
element queries but it seems to make up elements for us here. Richard?
But yes, we do
unsigned int extract_elts = extract_bytes * elts_per_byte;
and since native_encode_* and native_interpret_* operate on bytes we have
difficulties dealing with bit-precision entities with padding.
There's either the possibility to fail encoding when that happens or
do something else. Note that RTL expansion will do
case VECTOR_CST:
{
tree tmp = NULL_TREE;
if (VECTOR_MODE_P (mode))
return const_vector_from_tree (exp);
scalar_int_mode int_mode;
if (is_int_mode (mode, &int_mode))
{
tree type_for_mode = lang_hooks.types.type_for_mode (int_mode, 1);
if (type_for_mode)
tmp = fold_unary_loc (loc, VIEW_CONVERT_EXPR,
type_for_mode, exp);
which I think should always succeed (otherwise it falls back to expanding
a CTOR). That means failing to encode/interpret might get into
store_constructor which I think will zero a register destination and thus
fill padding with zeros.
So yeah, something like this looks OK, but I think instead of only
testing against 'count' we should also test against TYPE_VECTOR_SUBPARTS
(that might be variable, so with known_gt).
Would be interesting to see whether this fixes the issue without the
now installed patch.
