+/*
+ * Cardtable scanning
+ */
+
+#define MWORD_MASK (sizeof (mword) - 1)
+
+static inline int
+find_card_offset (mword card)
+{
+/*XXX Use assembly as this generates some pretty bad code */
+#if defined(__i386__) && defined(__GNUC__)
+ return (__builtin_ffs (card) - 1) / 8;
+#elif defined(__x86_64__) && defined(__GNUC__)
+ return (__builtin_ffsll (card) - 1) / 8;
+#elif defined(__s390x__)
+ return (__builtin_ffsll (GUINT64_TO_LE(card)) - 1) / 8;
+#else
+ int i;
+ guint8 *ptr = (guint8 *) &card;
+ for (i = 0; i < sizeof (mword); ++i) {
+ if (ptr[i])
+ return i;
+ }
+ return 0;
+#endif
+}
+
+guint8*
+sgen_find_next_card (guint8 *card_data, guint8 *end)
+{
+ mword *cards, *cards_end;
+ mword card;
+
+ while ((((mword)card_data) & MWORD_MASK) && card_data < end) {
+ if (*card_data)
+ return card_data;
+ ++card_data;
+ }
+
+ if (card_data == end)
+ return end;
+
+ cards = (mword*)card_data;
+ cards_end = (mword*)((mword)end & ~MWORD_MASK);
+ while (cards < cards_end) {
+ card = *cards;
+ if (card)
+ return (guint8*)cards + find_card_offset (card);
+ ++cards;
+ }
+
+ card_data = (guint8*)cards_end;
+ while (card_data < end) {
+ if (*card_data)
+ return card_data;
+ ++card_data;
+ }
+
+ return end;
+}
+