On Wed, 18 May 2016, Prathamesh Kulkarni wrote:
> On 17 May 2016 at 18:36, Richard Biener <rguent...@suse.de> wrote:
> > On Wed, 11 May 2016, Prathamesh Kulkarni wrote:
> >
> >> On 6 May 2016 at 17:20, Richard Biener <rguent...@suse.de> wrote:
> >> >
> >> > You can't simply use
> >> >
> >> > + offset = int_byte_position (field);
> >> >
> >> > as it can be placed at variable offset which will make int_byte_position
> >> > ICE. Note it also returns a truncated byte position (bit position
> >> > stripped) which may be undesirable here. I think you want to use
> >> > bit_position and if and only if DECL_FIELD_OFFSET and
> >> > DECL_FIELD_BIT_OFFSET are INTEGER_CST.
> >> oops, I didn't realize offsets could be variable.
> >> Will that be the case only for VLA member inside struct ?
> >
> > And non-VLA members after such member.
> >
> >> > Your observation about the expensiveness of the walk still stands I guess
> >> > and eventually you should at least cache the
> >> > get_vec_alignment_for_record_decl cases. Please make those workers
> >> > _type rather than _decl helpers.
> >> Done
> >> >
> >> > You seem to simply get at the maximum vectorized field/array element
> >> > alignment possible for all arrays - you could restrict that to
> >> > arrays with at least vector size (as followup).
> >> Um sorry, I didn't understand this part.
> >
> > It doesn't make sense to align
> >
> > struct { int a; int b; int c; int d; float b[3]; int e; };
> >
> > because we have a float[3] member. There is no vector size that
> > would cover the float[3] array.
> Thanks for the explanation.
> So we do not want to align struct if sizeof (array_field) < sizeof
> (vector_type).
> This issue is also present without patch for global arrays, so I modified
> get_vec_alignment_for_array_type, to return 0 if sizeof (array_type) <
> sizeof (vectype).
> >
> >> >
> >> > + /* Skip artificial decls like typeinfo decls or if
> >> > + record is packed. */
> >> > + if (DECL_ARTIFICIAL (record_decl) || TYPE_PACKED (type))
> >> > + return 0;
> >> >
> >> > I think we should honor DECL_USER_ALIGN as well and not mess with those
> >> > decls.
> >> Done
> >> >
> >> > Given the patch now does quite some extra work it might make sense
> >> > to split the symtab part out of the vect_can_force_dr_alignment_p
> >> > predicate and call that early.
> >> In the patch I call symtab_node::can_increase_alignment_p early. I tried
> >> moving that to it's callers - vect_compute_data_ref_alignment and
> >> increase_alignment::execute, however that failed some tests in vect, and
> >> hence I didn't add the following hunk in the patch. Did I miss some
> >> check ?
> >
> > Not sure.
> >
> >> diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c
> >> index 7652e21..2c1acee 100644
> >> --- a/gcc/tree-vect-data-refs.c
> >> +++ b/gcc/tree-vect-data-refs.c
> >> @@ -795,7 +795,10 @@ vect_compute_data_ref_alignment (struct
> >> data_reference *dr)
> >> && TREE_CODE (TREE_OPERAND (base, 0)) == ADDR_EXPR)
> >> base = TREE_OPERAND (TREE_OPERAND (base, 0), 0);
> >>
> >> - if (!vect_can_force_dr_alignment_p (base, TYPE_ALIGN (vectype)))
> >> + if (!(TREE_CODE (base) == VAR_DECL
> >> + && decl_in_symtab_p (base)
> >> + && symtab_node::get (base)->can_increase_alignment_p ()
> >> + && vect_can_force_dr_alignment_p (base, TYPE_ALIGN
> >> (vectype))))
> >> {
> >> if (dump_enabled_p ())
> >> {
> >
> > + for (tree field = first_field (type);
> > + field != NULL_TREE;
> > + field = DECL_CHAIN (field))
> > + {
> > + /* Skip if not FIELD_DECL or has variable offset. */
> > + if (TREE_CODE (field) != FIELD_DECL
> > + || TREE_CODE (DECL_FIELD_OFFSET (field)) != INTEGER_CST
> > + || TREE_CODE (DECL_FIELD_BIT_OFFSET (field)) != INTEGER_CST
> > + || DECL_USER_ALIGN (field)
> > + || DECL_ARTIFICIAL (field))
> > + continue;
> >
> > you can stop processing the type and return 0 here if the offset
> > is not an INTEGER_CST. All following fields will have the same issue.
> >
> > + /* FIXME: is this check necessary since we check for variable
> > offset above ? */
> > + if (TREE_CODE (offset_tree) != INTEGER_CST)
> > + continue;
> >
> > the check should not be necessary.
> >
> > offset = tree_to_uhwi (offset_tree);
> >
> > but in theory offset_tree might not fit a unsigned HOST_WIDE_INT, so
> > instead of for INTEGER_CST please check ! tree_fits_uhwi_p (offset_tree).
> > As above all following fields will also fail the check if this fails so
> > you can return 0 early.
> >
> > +static unsigned
> > +get_vec_alignment_for_type (tree type)
> > +{
> > + if (type == NULL_TREE)
> > + return 0;
> > +
> > + gcc_assert (TYPE_P (type));
> > +
> > + unsigned *slot = type_align_map->get (type);
> > + if (slot)
> > + return *slot;
> >
> > I suggest to apply the caching only for the RECORD_TYPE case to keep
> > the size of the map low.
> >
> > Otherwise the patch looks ok now.
> I have done the suggested changes in attached patch.
> Is this version OK to commit after bootstrap+test ?
> The patch survives cross-testing on arm*-*-* and aarch64*-*-*.
+ tree type_size_tree = TYPE_SIZE (type);
+ if (!type_size_tree)
+ return TYPE_ALIGN (vectype);
+
+ if (TREE_CODE (type_size_tree) != INTEGER_CST)
+ return TYPE_ALIGN (vectype);
+
+ /* If array has constant size, ensure that it's at least equal to
+ size of vector type. */
+ if (!tree_fits_uhwi_p (type_size_tree))
+ return TYPE_ALIGN (vectype);
+ unsigned HOST_WIDE_INT type_size = tree_to_uhwi (type_size_tree);
+
+ tree vectype_size_tree = TYPE_SIZE (vectype);
+ if (!tree_fits_uhwi_p (vectype_size_tree))
+ return TYPE_ALIGN (vectype);
+
+ unsigned HOST_WIDE_INT vectype_size = tree_to_uhwi (vectype_size_tree);
+ return (type_size > vectype_size) ? TYPE_ALIGN (vectype) : 0;
please change this to
if (! TYPE_SIZE (type)
|| TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST
|| tree_int_cst_lt (TYPE_SIZE (type), TYPE_SIZE (vectype)))
return 0;
return TYPE_ALIGN (vectype);
consistent with the handling for "VLA" records.
+ unsigned *slot = type_align_map->get (type);
+ if (slot)
+ return *slot;
+
+ unsigned max_align = 0, alignment;
+ HOST_WIDE_INT offset;
+ tree offset_tree;
+
+ if (TYPE_PACKED (type))
+ return 0;
+
move the tye_align_map query after the TYPE_PACKED check.
+ /* We don't need to process the type further if offset is variable,
+ since the offsets of remaining members will also be variable. */
+ if (TREE_CODE (DECL_FIELD_OFFSET (field)) != INTEGER_CST
+ || TREE_CODE (DECL_FIELD_BIT_OFFSET (field)) != INTEGER_CST)
+ return 0;
just break; here (and in the other case returning zero). If a
previous record field said we'd want to align we still should align.
Also we want to store 0 into the type_align_map as well.
Ok with those changes.
Thanks,
Richard.
