On Wed, Nov 6, 2024 at 12:49 PM Tejas Belagod <tejas.bela...@arm.com> wrote:
>
> Ensure sizeless types don't end up trying to be canonicalised to
> BIT_FIELD_REFs.
You mean variable-sized? But don't we know, when there's a constant
array index,
that the size is at least so this indexing is OK? So what's wrong with a
fixed position, fixed size BIT_FIELD_REF extraction of a VLA object?
Richard.
> gcc/ChangeLog:
>
> * gimple-fold.cc (maybe_canonicalize_mem_ref_addr): Disallow sizeless
> types in BIT_FIELD_REFs.
> ---
> gcc/gimple-fold.cc | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
> index c19dac0dbfd..dd45d9f7348 100644
> --- a/gcc/gimple-fold.cc
> +++ b/gcc/gimple-fold.cc
> @@ -6281,6 +6281,7 @@ maybe_canonicalize_mem_ref_addr (tree *t, bool is_debug
> = false)
> && VECTOR_TYPE_P (TREE_TYPE (TREE_OPERAND (TREE_OPERAND (*t, 0), 0))))
> {
> tree vtype = TREE_TYPE (TREE_OPERAND (TREE_OPERAND (*t, 0), 0));
> + /* BIT_FIELD_REF can only happen on constant-size vectors. */
> if (VECTOR_TYPE_P (vtype))
> {
> tree low = array_ref_low_bound (*t);
> @@ -6294,7 +6295,7 @@ maybe_canonicalize_mem_ref_addr (tree *t, bool is_debug
> = false)
> (TYPE_SIZE (TREE_TYPE (*t))));
> widest_int ext
> = wi::add (idx, wi::to_widest (TYPE_SIZE (TREE_TYPE
> (*t))));
> - if (wi::les_p (ext, wi::to_widest (TYPE_SIZE (vtype))))
> + if (known_le (ext, wi::to_poly_widest (TYPE_SIZE (vtype))))
> {
> *t = build3_loc (EXPR_LOCATION (*t), BIT_FIELD_REF,
> TREE_TYPE (*t),
> --
> 2.25.1
>
