- /* Figure out our register classes and preallocated registers*/
- list_for_each_entry(struct qinst, inst, &c->instructions, link) {
+ /* Figure out our register classes and preallocated registers. We
+ * start with any temp being able to be in any file, then instructions
+ * incrementally remove bits that the temp definitely can't be in.
+ */
+ memset(class_bits,
+ CLASS_BIT_A | CLASS_BIT_B_OR_ACC | CLASS_BIT_R4,
+ sizeof(class_bits));
+
+ int ip = 0;
+ qir_for_each_inst_inorder(inst, c) {
+ if (qir_writes_r4(inst)) {
+ /* This instruction writes r4 (and optionally moves
+ * its result to a temp), so nothing else can be
+ * stored in r4 across it.
+ */
+ for (int i = 0; i < c->num_temps; i++) {
+ if (c->temp_start[i] < ip && c->temp_end[i] > ip)
+ class_bits[i] &= ~CLASS_BIT_R4;
+ }
+ } else {
+ /* R4 can't be written as a general purpose
+ * register. (it's TMU_NOSWAP as a write address).
+ */
+ if (inst->dst.file == QFILE_TEMP)
+ class_bits[inst->dst.index] &= ~CLASS_BIT_R4;
+ }
+