static void
replace_with_mov(struct vc4_compile *c, struct qinst *inst, struct qreg arg)
{
dump_from(c, inst);
if (qir_is_mul(inst))
inst->op = QOP_MMOV;
else if (qir_is_float_input(inst))
inst->op = QOP_FMOV;
else
inst->op = QOP_MOV;
inst->src[0] = arg;
inst->src[1] = c->undef;
dump_to(c, inst);
}
static bool
try_copy_prop(struct vc4_compile *c, struct qinst *inst, struct qinst **movs)
{
bool debug = false;
bool progress = false;
for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
if (inst->src[i].file != QFILE_TEMP)
continue;
/* We have two ways of finding MOVs we can copy propagate
* from. One is if it's an SSA def: then we can reuse it from
* any block in the program, as long as its source is also an
* SSA def. Alternatively, if it's in the "movs" array
* tracked within the block, then we know the sources for it
* haven't been changed since we saw the instruction within
* our block.
*/
struct qinst *mov = movs[inst->src[i].index];
if (!mov) {
if (!is_copy_mov(c->defs[inst->src[i].index]))
continue;
mov = c->defs[inst->src[i].index];
if (mov->src[0].file == QFILE_TEMP &&
!c->defs[mov->src[0].index])
continue;
}
/* Mul rotation's source needs to be in an r0-r3 accumulator,
* so no uniforms or regfile-a/r4 unpacking allowed.
*/
if (inst->op == QOP_ROT_MUL &&
(mov->src[0].file != QFILE_TEMP ||
mov->src[0].pack))
continue;
uint8_t unpack;
if (mov->src[0].pack) {
/* Make sure that the meaning of the unpack
* would be the same between the two
* instructions.
*/
if (qir_is_float_input(inst) !=
qir_is_float_input(mov)) {
continue;
}
/* There's only one unpack field, so make sure
* this instruction doesn't already use it.
*/
bool already_has_unpack = false;
for (int j = 0; j < qir_get_op_nsrc(inst->op); j++) {
if (inst->src[j].pack)
already_has_unpack = true;
}
if (already_has_unpack)
continue;
/* A destination pack requires the PM bit to
* be set to a specific value already, which
* may be different from ours.
*/
if (inst->dst.pack)
continue;
unpack = mov->src[0].pack;
} else {
unpack = inst->src[i].pack;
}
if (debug) {
fprintf(stderr, "Copy propagate: ");
qir_dump_inst(c, inst);
fprintf(stderr, "\n");
}
inst->src[i] = mov->src[0];
inst->src[i].pack = unpack;
if (debug) {
fprintf(stderr, "to: ");
qir_dump_inst(c, inst);
fprintf(stderr, "\n");
}
progress = true;
}
return progress;
}
/**
* Returns a mapping from QFILE_TEMP indices to struct qpu_regs.
*
* The return value should be freed by the caller.
*/
struct qpu_reg *
vc4_register_allocate(struct vc4_context *vc4, struct vc4_compile *c)
{
struct node_to_temp_map map[c->num_temps];
uint32_t temp_to_node[c->num_temps];
uint8_t class_bits[c->num_temps];
struct qpu_reg *temp_registers = calloc(c->num_temps,
sizeof(*temp_registers));
/* If things aren't ever written (undefined values), just read from
* r0.
*/
for (uint32_t i = 0; i < c->num_temps; i++)
temp_registers[i] = qpu_rn(0);
vc4_alloc_reg_set(vc4);
struct ra_graph *g = ra_alloc_interference_graph(vc4->regs,
c->num_temps);
/* Compute the live ranges so we can figure out interference. */
qir_calculate_live_intervals(c);
for (uint32_t i = 0; i < c->num_temps; i++) {
map[i].temp = i;
map[i].priority = c->temp_end[i] - c->temp_start[i];
}
qsort(map, c->num_temps, sizeof(map[0]), node_to_temp_priority);
for (uint32_t i = 0; i < c->num_temps; i++) {
temp_to_node[map[i].temp] = i;
}
/* 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;
}
switch (inst->op) {
case QOP_FRAG_Z:
ra_set_node_reg(g, temp_to_node[inst->dst.index],
AB_INDEX + QPU_R_FRAG_PAYLOAD_ZW * 2 + 1);
break;
case QOP_FRAG_W:
ra_set_node_reg(g, temp_to_node[inst->dst.index],
AB_INDEX + QPU_R_FRAG_PAYLOAD_ZW * 2);
break;
case QOP_ROT_MUL:
assert(inst->src[0].file == QFILE_TEMP);
class_bits[inst->src[0].index] &= ~CLASS_BIT_R0_R3;
break;
default:
break;
}
if (inst->dst.pack && !qir_is_mul(inst)) {
/* The non-MUL pack flags require an A-file dst
* register.
*/
class_bits[inst->dst.index] &= CLASS_BIT_A;
}
/* Apply restrictions for src unpacks. The integer unpacks
* can only be done from regfile A, while float unpacks can be
* either A or R4.
*/
for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
if (inst->src[i].file == QFILE_TEMP &&
inst->src[i].pack) {
if (qir_is_float_input(inst)) {
class_bits[inst->src[i].index] &=
CLASS_BIT_A | CLASS_BIT_R4;
} else {
class_bits[inst->src[i].index] &=
CLASS_BIT_A;
}
}
}
ip++;
}
for (uint32_t i = 0; i < c->num_temps; i++) {
int node = temp_to_node[i];
switch (class_bits[i]) {
case CLASS_BIT_A | CLASS_BIT_B_OR_ACC | CLASS_BIT_R4:
ra_set_node_class(g, node, vc4->reg_class_any);
break;
case CLASS_BIT_A | CLASS_BIT_B_OR_ACC:
ra_set_node_class(g, node, vc4->reg_class_a_or_b_or_acc);
break;
case CLASS_BIT_A | CLASS_BIT_R4:
ra_set_node_class(g, node, vc4->reg_class_r4_or_a);
break;
case CLASS_BIT_A:
ra_set_node_class(g, node, vc4->reg_class_a);
break;
case CLASS_BIT_R0_R3:
ra_set_node_class(g, node, vc4->reg_class_r0_r3);
break;
default:
fprintf(stderr, "temp %d: bad class bits: 0x%x\n",
i, class_bits[i]);
abort();
break;
}
}
for (uint32_t i = 0; i < c->num_temps; i++) {
for (uint32_t j = i + 1; j < c->num_temps; j++) {
if (!(c->temp_start[i] >= c->temp_end[j] ||
c->temp_start[j] >= c->temp_end[i])) {
ra_add_node_interference(g,
temp_to_node[i],
temp_to_node[j]);
}
}
}
bool ok = ra_allocate(g);
if (!ok) {
fprintf(stderr, "Failed to register allocate:\n");
qir_dump(c);
c->failed = true;
return NULL;
}
for (uint32_t i = 0; i < c->num_temps; i++) {
temp_registers[i] = vc4_regs[ra_get_node_reg(g, temp_to_node[i])];
/* If the value's never used, just write to the NOP register
* for clarity in debug output.
*/
if (c->temp_start[i] == c->temp_end[i])
temp_registers[i] = qpu_ra(QPU_W_NOP);
}
ralloc_free(g);
return temp_registers;
}
