[PATCH 1/2] Use is_empty_type instead of zero-sized type.

[Richard Biener]

On Mon, May 31, 2021 at 7:29 PM apinski--- via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> From: Andrew Pinski <apinski@marvell.com>
>
> Instead of only removing assignments of zero-sized types,
> assignments of all empty types should be removed during gimplification.
> This moves to use is_empty_type which will be used in other places too.
>
> OK?  Bootstrapped and tested on aarch64-linux-gnu with no regressions.

OK.

Thanks,
Richard.

> Thanks,
> Andrew Pinski
>
> gcc/ChangeLog:
>
>         * gimplify.c (zero_sized_field_decl): Delete
>         (zero_sized_type): Delete
>         (gimplify_init_ctor_eval): Use is_empty_type instead
>         of zero_sized_field_decl.
>         (gimplify_modify_expr): Use is_empty_type instead of
>         zero_sized_type.
> ---
>  gcc/gimplify.c | 34 +++++++---------------------------
>  1 file changed, 7 insertions(+), 27 deletions(-)
>
> diff --git a/gcc/gimplify.c b/gcc/gimplify.c
> index 3ca29cedad8..39f5b973d18 100644
> --- a/gcc/gimplify.c
> +++ b/gcc/gimplify.c
> @@ -4644,28 +4644,6 @@ gimplify_init_ctor_eval_range (tree object, tree lower, tree upper,
>    gimplify_seq_add_stmt (pre_p, gimple_build_label (loop_exit_label));
>  }
>
> -/* Return true if FDECL is accessing a field that is zero sized.  */
> -
> -static bool
> -zero_sized_field_decl (const_tree fdecl)
> -{
> -  if (TREE_CODE (fdecl) == FIELD_DECL && DECL_SIZE (fdecl)
> -      && integer_zerop (DECL_SIZE (fdecl)))
> -    return true;
> -  return false;
> -}
> -
> -/* Return true if TYPE is zero sized.  */
> -
> -static bool
> -zero_sized_type (const_tree type)
> -{
> -  if (AGGREGATE_TYPE_P (type) && TYPE_SIZE (type)
> -      && integer_zerop (TYPE_SIZE (type)))
> -    return true;
> -  return false;
> -}
> -
>  /* A subroutine of gimplify_init_constructor.  Generate individual
>     MODIFY_EXPRs for a CONSTRUCTOR.  OBJECT is the LHS against which the
>     assignments should happen.  ELTS is the CONSTRUCTOR_ELTS of the
> @@ -4699,11 +4677,13 @@ gimplify_init_ctor_eval (tree object, vec<constructor_elt, va_gc> *elts,
>        gcc_assert (purpose);
>
>        /* Skip zero-sized fields, unless value has side-effects.  This can
> -        happen with calls to functions returning a zero-sized type, which
> +        happen with calls to functions returning a empty type, which
>          we shouldn't discard.  As a number of downstream passes don't
> -        expect sets of zero-sized fields, we rely on the gimplification of
> +        expect sets of empty type fields, we rely on the gimplification of
>          the MODIFY_EXPR we make below to drop the assignment statement.  */
> -      if (! TREE_SIDE_EFFECTS (value) && zero_sized_field_decl (purpose))
> +      if (!TREE_SIDE_EFFECTS (value)
> +         && TREE_CODE (purpose) == FIELD_DECL
> +         && is_empty_type (TREE_TYPE (purpose)))
>         continue;
>
>        /* If we have a RANGE_EXPR, we have to build a loop to assign the
> @@ -5781,11 +5761,11 @@ gimplify_modify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
>    if (ret != GS_UNHANDLED)
>      return ret;
>
> -  /* For zero sized types only gimplify the left hand side and right hand
> +  /* For empty types only gimplify the left hand side and right hand
>       side as statements and throw away the assignment.  Do this after
>       gimplify_modify_expr_rhs so we handle TARGET_EXPRs of addressable
>       types properly.  */
> -  if (zero_sized_type (TREE_TYPE (*from_p))
> +  if (is_empty_type (TREE_TYPE (*from_p))
>        && !want_value
>        /* Don't do this for calls that return addressable types, expand_call
>          relies on those having a lhs.  */
> --
> 2.17.1
>