+void *htable_prev_(const struct htable *ht, struct htable_iter *i)
+{
+ for (;;) {
+ if (!i->off)
+ return NULL;
+ i->off--;
+ if (entry_is_valid(ht->table[i->off]))
+ return get_raw_ptr(ht, ht->table[i->off]);
+ }
+}
+
+/* Another bit currently in mask needs to be exposed, so that a bucket with p in
+ * it won't appear invalid */
+static COLD void unset_another_common_bit(struct htable *ht,
+ uintptr_t *maskdiff,
+ const void *p)
+{
+ size_t i;
+
+ for (i = sizeof(uintptr_t) * CHAR_BIT - 1; i > 0; i--) {
+ if (((uintptr_t)p & ((uintptr_t)1 << i))
+ && ht->common_mask & ~*maskdiff & ((uintptr_t)1 << i))
+ break;
+ }
+ /* There must have been one, right? */
+ assert(i > 0);
+
+ *maskdiff |= ((uintptr_t)1 << i);
+}
+
+/* We want to change the common mask: this fixes up the table */
+static COLD void fixup_table_common(struct htable *ht, uintptr_t maskdiff)
+{
+ size_t i;
+ uintptr_t bitsdiff;
+
+again:
+ bitsdiff = ht->common_bits & maskdiff;
+
+ for (i = 0; i < (size_t)1 << ht->bits; i++) {
+ uintptr_t e;
+ if (!entry_is_valid(e = ht->table[i]))
+ continue;
+
+ /* Clear the bits no longer in the mask, set them as
+ * expected. */
+ e &= ~maskdiff;
+ e |= bitsdiff;
+ /* If this made it invalid, restart with more exposed */
+ if (!entry_is_valid(e)) {
+ unset_another_common_bit(ht, &maskdiff, get_raw_ptr(ht, e));
+ goto again;
+ }
+ ht->table[i] = e;
+ }
+
+ /* Take away those bits from our mask, bits and perfect bit. */
+ ht->common_mask &= ~maskdiff;
+ ht->common_bits &= ~maskdiff;
+ if (ht_perfect_mask(ht) & maskdiff)
+ ht->perfect_bitnum = NO_PERFECT_BIT;
+}
+
+/* Limited recursion */
+static void ht_add(struct htable *ht, const void *new, size_t h);
+
+/* We tried to add this entry, but it looked invalid! We need to
+ * let another pointer bit through mask */
+static COLD void update_common_fix_invalid(struct htable *ht, const void *p, size_t h)
+{
+ uintptr_t maskdiff;
+
+ assert(ht->elems != 0);
+
+ maskdiff = 0;
+ unset_another_common_bit(ht, &maskdiff, p);
+ fixup_table_common(ht, maskdiff);
+
+ /* Now won't recurse */
+ ht_add(ht, p, h);
+}
+