+ /* See the docs for TARGET_MS_BITFIELD_LAYOUT_P for details.
+ A subtlety:
+ When a bit field is inserted into a packed record, the whole
+ size of the underlying type is used by one or more same-size
+ adjacent bitfields. (That is, if its long:3, 32 bits is
+ used in the record, and any additional adjacent long bitfields are
+ packed into the same chunk of 32 bits. However, if the size
+ changes, a new field of that size is allocated.) In an unpacked
+ record, this is the same as using alignment, but not equivalent
+ when packing.
+
+ Note: for compatibility, we use the type size, not the type alignment
+ to determine alignment, since that matches the documentation */
+
+ if ((* targetm.ms_bitfield_layout_p) (rli->t)
+ && ((DECL_BIT_FIELD_TYPE (field) && ! DECL_PACKED (field))
+ || (rli->prev_field && ! DECL_PACKED (rli->prev_field))))
+ {
+ /* At this point, either the prior or current are bitfields,
+ (possibly both), and we're dealing with MS packing. */
+ tree prev_saved = rli->prev_field;
+
+ /* Is the prior field a bitfield? If so, handle "runs" of same
+ type size fields. */
+ if (rli->prev_field /* necessarily a bitfield if it exists. */)
+ {
+ /* If both are bitfields, nonzero, and the same size, this is
+ the middle of a run. Zero declared size fields are special
+ and handled as "end of run". (Note: it's nonzero declared
+ size, but equal type sizes!) (Since we know that both
+ the current and previous fields are bitfields by the
+ time we check it, DECL_SIZE must be present for both.) */
+ if (DECL_BIT_FIELD_TYPE (field)
+ && !integer_zerop (DECL_SIZE (field))
+ && !integer_zerop (DECL_SIZE (rli->prev_field))
+ && host_integerp (DECL_SIZE (rli->prev_field), 0)
+ && host_integerp (TYPE_SIZE (type), 0)
+ && simple_cst_equal (TYPE_SIZE (type),
+ TYPE_SIZE (TREE_TYPE (rli->prev_field))))
+ {
+ /* We're in the middle of a run of equal type size fields; make
+ sure we realign if we run out of bits. (Not decl size,
+ type size!) */
+ HOST_WIDE_INT bitsize = tree_low_cst (DECL_SIZE (field), 0);
+
+ if (rli->remaining_in_alignment < bitsize)
+ {
+ /* out of bits; bump up to next 'word'. */
+ rli->offset = DECL_FIELD_OFFSET (rli->prev_field);
+ rli->bitpos
+ = size_binop (PLUS_EXPR, TYPE_SIZE (type),
+ DECL_FIELD_BIT_OFFSET (rli->prev_field));
+ rli->prev_field = field;
+ rli->remaining_in_alignment
+ = tree_low_cst (TYPE_SIZE (type), 0);
+ }
+
+ rli->remaining_in_alignment -= bitsize;
+ }
+ else
+ {
+ /* End of a run: if leaving a run of bitfields of the same type
+ size, we have to "use up" the rest of the bits of the type
+ size.
+
+ Compute the new position as the sum of the size for the prior
+ type and where we first started working on that type.
+ Note: since the beginning of the field was aligned then
+ of course the end will be too. No round needed. */
+
+ if (!integer_zerop (DECL_SIZE (rli->prev_field)))
+ {
+ tree type_size = TYPE_SIZE (TREE_TYPE (rli->prev_field));
+
+ rli->bitpos
+ = size_binop (PLUS_EXPR, type_size,
+ DECL_FIELD_BIT_OFFSET (rli->prev_field));
+ }
+ else
+ /* We "use up" size zero fields; the code below should behave
+ as if the prior field was not a bitfield. */
+ prev_saved = NULL;
+
+ /* Cause a new bitfield to be captured, either this time (if
+ currently a bitfield) or next time we see one. */
+ if (!DECL_BIT_FIELD_TYPE(field)
+ || integer_zerop (DECL_SIZE (field)))
+ rli->prev_field = NULL;
+ }
+
+ rli->offset_align = tree_low_cst (TYPE_SIZE (type), 0);
+ normalize_rli (rli);
+ }
+
+ /* If we're starting a new run of same size type bitfields
+ (or a run of non-bitfields), set up the "first of the run"
+ fields.
+
+ That is, if the current field is not a bitfield, or if there
+ was a prior bitfield the type sizes differ, or if there wasn't
+ a prior bitfield the size of the current field is nonzero.
+
+ Note: we must be sure to test ONLY the type size if there was
+ a prior bitfield and ONLY for the current field being zero if
+ there wasn't. */
+
+ if (!DECL_BIT_FIELD_TYPE (field)
+ || ( prev_saved != NULL
+ ? !simple_cst_equal (TYPE_SIZE (type),
+ TYPE_SIZE (TREE_TYPE (prev_saved)))
+ : !integer_zerop (DECL_SIZE (field)) ))
+ {
+ /* Never smaller than a byte for compatibility. */
+ unsigned int type_align = BITS_PER_UNIT;
+
+ /* (When not a bitfield), we could be seeing a flex array (with
+ no DECL_SIZE). Since we won't be using remaining_in_alignment
+ until we see a bitfield (and come by here again) we just skip
+ calculating it. */
+ if (DECL_SIZE (field) != NULL
+ && host_integerp (TYPE_SIZE (TREE_TYPE (field)), 0)
+ && host_integerp (DECL_SIZE (field), 0))
+ rli->remaining_in_alignment
+ = tree_low_cst (TYPE_SIZE (TREE_TYPE(field)), 0)
+ - tree_low_cst (DECL_SIZE (field), 0);
+
+ /* Now align (conventionally) for the new type. */
+ if (!DECL_PACKED(field))
+ type_align = MAX(TYPE_ALIGN (type), type_align);
+
+ if (prev_saved
+ && DECL_BIT_FIELD_TYPE (prev_saved)
+ /* If the previous bit-field is zero-sized, we've already
+ accounted for its alignment needs (or ignored it, if
+ appropriate) while placing it. */
+ && ! integer_zerop (DECL_SIZE (prev_saved)))
+ type_align = MAX (type_align,
+ TYPE_ALIGN (TREE_TYPE (prev_saved)));
+
+ if (maximum_field_alignment != 0)
+ type_align = MIN (type_align, maximum_field_alignment);
+
+ rli->bitpos = round_up (rli->bitpos, type_align);
+
+ /* If we really aligned, don't allow subsequent bitfields
+ to undo that. */
+ rli->prev_field = NULL;
+ }
+ }
+