https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78429
--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Eric Botcazou from comment #8)
> > where -1 no longer "fits" bool even though it should. So
> >
> > /* Short-circuit boolean types since various transformations assume that
> > they can only take values 0 and 1. */
> > if (TREE_CODE (type) == BOOLEAN_TYPE)
> > return eq_p (x, 0) || eq_p (x, 1);
> >
> > is wrong and should use eq_p (x, -1) instead as bool is signed? The
> > int_fits_type_p function is likely wrong as well (uses integer_onep).
>
> Standard boolean types as unsigned though, not signed:
>
> Index: tree.c
> ===================================================================
> --- tree.c (revision 242632)
> +++ tree.c (working copy)
> @@ -8218,7 +8218,7 @@ build_nonstandard_boolean_type (unsigned
>
> type = make_node (BOOLEAN_TYPE);
> TYPE_PRECISION (type) = precision;
> - fixup_signed_type (type);
> + fixup_unsigned_type (type);
>
> if (precision <= MAX_INT_CACHED_PREC)
> nonstandard_boolean_type_cache[precision] = type;
>
> fixes the ICE.
fortran does
static tree
gfc_build_logical_type (gfc_logical_info *info)
{
int bit_size = info->bit_size;
tree new_type;
if (bit_size == BOOL_TYPE_SIZE)
{
info->c_bool = 1;
return boolean_type_node;
}
new_type = make_unsigned_type (bit_size);
TREE_SET_CODE (new_type, BOOLEAN_TYPE);
TYPE_MAX_VALUE (new_type) = build_int_cst (new_type, 1);
TYPE_PRECISION (new_type) = 1;
note that the vectorizer emits code to widen the boolean types expecting
sign-extension of vector truth (-1). That matches what the RTL code gen
ends up doing semantics-wise.
It has been changed by
2015-11-09 Ilya Enkovich <enkovich....@gmail.com>
* optabs.c (expand_vec_cond_expr): Always get sign from type.
* tree.c (wide_int_to_tree): Support negative values for boolean.
(build_nonstandard_boolean_type): Use signed type for booleans.
thus the signedness is wanted (so is the precision). The issues arise
once we are extracting a vector element and performing the (_Bool) cast...
