+ if (a_elt && b_elt && a_elt->indx == b_elt->indx)
+ {
+ /* Matching elts, generate A ^ B. */
+ unsigned ix;
+ BITMAP_WORD ior = 0;
+
+ if (!dst_elt)
+ dst_elt = bitmap_elt_insert_after (dst, dst_prev);
+
+ dst_elt->indx = a_elt->indx;
+ for (ix = BITMAP_ELEMENT_WORDS; ix--;)
+ {
+ BITMAP_WORD r = a_elt->bits[ix] ^ b_elt->bits[ix];
+
+ ior |= r;
+ dst_elt->bits[ix] = r;
+ }
+ a_elt = a_elt->next;
+ b_elt = b_elt->next;
+ if (ior)
+ {
+ dst_prev = dst_elt;
+ dst_elt = dst_elt->next;
+ }
+ }
+ else
+ {
+ /* Copy a single element. */
+ bitmap_element *src;
+
+ if (!b_elt || (a_elt && a_elt->indx < b_elt->indx))
+ {
+ src = a_elt;
+ a_elt = a_elt->next;
+ }
+ else
+ {
+ src = b_elt;
+ b_elt = b_elt->next;
+ }
+
+ if (!dst_elt)
+ dst_elt = bitmap_elt_insert_after (dst, dst_prev);
+
+ dst_elt->indx = src->indx;
+ memcpy (dst_elt->bits, src->bits, sizeof (dst_elt->bits));
+ dst_prev = dst_elt;
+ dst_elt = dst_elt->next;
+ }
+ }
+ bitmap_elt_clear_from (dst, dst_elt);
+ gcc_assert (!dst->current == !dst->first);
+ if (dst->current)
+ dst->indx = dst->current->indx;
+}
+
+/* A ^= B */
+
+void
+bitmap_xor_into (bitmap a, bitmap b)
+{
+ bitmap_element *a_elt = a->first;
+ bitmap_element *b_elt = b->first;
+ bitmap_element *a_prev = NULL;
+
+ gcc_assert (a != b);
+ while (b_elt)
+ {
+ if (!a_elt || b_elt->indx < a_elt->indx)
+ {
+ /* Copy b_elt. */
+ bitmap_element *dst = bitmap_elt_insert_after (a, a_prev);
+
+ dst->indx = b_elt->indx;
+ memcpy (dst->bits, b_elt->bits, sizeof (dst->bits));
+ a_prev = dst;
+ b_elt = b_elt->next;
+ }
+ else if (a_elt->indx < b_elt->indx)
+ {
+ a_prev = a_elt;
+ a_elt = a_elt->next;
+ }
+ else
+ {
+ /* Matching elts, generate A ^= B. */
+ unsigned ix;
+ BITMAP_WORD ior = 0;
+ bitmap_element *next = a_elt->next;
+
+ for (ix = BITMAP_ELEMENT_WORDS; ix--;)
+ {
+ BITMAP_WORD r = a_elt->bits[ix] ^ b_elt->bits[ix];
+
+ ior |= r;
+ a_elt->bits[ix] = r;
+ }
+ b_elt = b_elt->next;
+ if (ior)
+ a_prev = a_elt;
+ else
+ bitmap_element_free (a, a_elt);
+ a_elt = next;
+ }