+struct node_to_temp_map {
+ uint32_t temp;
+ uint32_t priority;
+};
+
+static int
+node_to_temp_priority(const void *in_a, const void *in_b)
+{
+ const struct node_to_temp_map *a = in_a;
+ const struct node_to_temp_map *b = in_b;
+
+ return a->priority - b->priority;
+}
+
+#define CLASS_BIT_A (1 << 0)
+#define CLASS_BIT_B (1 << 1)
+#define CLASS_BIT_R4 (1 << 2)
+#define CLASS_BIT_R0_R3 (1 << 4)
+
+struct vc4_ra_select_callback_data {
+ uint32_t next_acc;
+ uint32_t next_ab;
+};
+
+static unsigned int
+vc4_ra_select_callback(struct ra_graph *g, BITSET_WORD *regs, void *data)
+{
+ struct vc4_ra_select_callback_data *vc4_ra = data;
+
+ /* If r4 is available, always choose it -- few other things can go
+ * there, and choosing anything else means inserting a mov.
+ */
+ if (BITSET_TEST(regs, ACC_INDEX + 4))
+ return ACC_INDEX + 4;
+
+ /* Choose an accumulator if possible (no delay between write and
+ * read), but round-robin through them to give post-RA instruction
+ * selection more options.
+ */
+ for (int i = 0; i < ACC_COUNT; i++) {
+ int acc_off = (vc4_ra->next_acc + i) % ACC_COUNT;
+ int acc = ACC_INDEX + acc_off;
+
+ if (BITSET_TEST(regs, acc)) {
+ vc4_ra->next_acc = acc_off + 1;
+ return acc;
+ }
+ }
+
+ for (int i = 0; i < AB_COUNT; i++) {
+ int ab_off = (vc4_ra->next_ab + i) % AB_COUNT;
+ int ab = AB_INDEX + ab_off;
+
+ if (BITSET_TEST(regs, ab)) {
+ vc4_ra->next_ab = ab_off + 1;
+ return ab;
+ }
+ }
+
+ unreachable("RA must pass us at least one possible reg.");
+}
+