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aco: improve live variable analysis

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This patch makes the live variable analysis more precise
w.r.t. killed phi operands and the block's register pressure.

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
This commit is contained in:
Daniel Schürmann
2019-10-29 11:56:09 +01:00
parent 0b8216b2cd
commit 78bca0d0ce
1 changed files with 64 additions and 25 deletions
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src/amd/compiler/aco_live_var_analysis.cpp
+64 -25
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@@ -71,14 +71,17 @@ void process_live_temps_per_block(Program *program, live& lives, Block* block,
new_demand.sgpr -= phi_sgpr_ops[block->index];
/* traverse the instructions backwards */
for (int idx = block->instructions.size() -1; idx >= 0; idx--)
{
int idx;
for (idx = block->instructions.size() -1; idx >= 0; idx--) {
Instruction *insn = block->instructions[idx].get();
if (is_phi(insn))
break;
/* substract the 2 sgprs from exec */
if (exec_live)
assert(new_demand.sgpr >= 2);
register_demand[idx] = RegisterDemand(new_demand.vgpr, new_demand.sgpr - (exec_live ? 2 : 0));
Instruction *insn = block->instructions[idx].get();
/* KILL */
for (Definition& definition : insn->definitions) {
if (!definition.isTemp()) {
@@ -105,28 +108,7 @@ void process_live_temps_per_block(Program *program, live& lives, Block* block,
}
/* GEN */
if (insn->opcode == aco_opcode::p_phi ||
insn->opcode == aco_opcode::p_linear_phi) {
/* directly insert into the predecessors live-out set */
std::vector<unsigned>& preds = insn->opcode == aco_opcode::p_phi
? block->logical_preds
: block->linear_preds;
for (unsigned i = 0; i < preds.size(); ++i)
{
Operand &operand = insn->operands[i];
if (!operand.isTemp()) {
continue;
}
/* check if we changed an already processed block */
const bool inserted = live_temps[preds[i]].insert(operand.getTemp()).second;
if (inserted) {
operand.setFirstKill(true);
worklist.insert(preds[i]);
if (insn->opcode == aco_opcode::p_phi && operand.getTemp().type() == RegType::sgpr)
phi_sgpr_ops[preds[i]] += operand.size();
}
}
} else if (insn->opcode == aco_opcode::p_logical_end) {
if (insn->opcode == aco_opcode::p_logical_end) {
new_demand.sgpr += phi_sgpr_ops[block->index];
} else {
for (unsigned i = 0; i < insn->operands.size(); ++i)
@@ -160,6 +142,37 @@ void process_live_temps_per_block(Program *program, live& lives, Block* block,
block->register_demand.update(register_demand[idx]);
}
/* update block's register demand for a last time */
if (exec_live)
assert(new_demand.sgpr >= 2);
new_demand.sgpr -= exec_live ? 2 : 0;
block->register_demand.update(new_demand);
/* handle phi definitions */
int phi_idx = idx;
while (phi_idx >= 0) {
register_demand[phi_idx] = new_demand;
Instruction *insn = block->instructions[phi_idx].get();
assert(is_phi(insn));
assert(insn->definitions.size() == 1 && insn->definitions[0].isTemp());
Definition& definition = insn->definitions[0];
const Temp temp = definition.getTemp();
size_t n = 0;
if (temp.is_linear())
n = live_sgprs.erase(temp);
else
n = live_vgprs.erase(temp);
if (n)
definition.setKill(false);
else
definition.setKill(true);
phi_idx--;
}
/* now, we have the live-in sets and need to merge them into the live-out sets */
for (unsigned pred_idx : block->logical_preds) {
for (Temp vgpr : live_vgprs) {
@@ -177,6 +190,32 @@ void process_live_temps_per_block(Program *program, live& lives, Block* block,
}
}
/* handle phi operands */
phi_idx = idx;
while (phi_idx >= 0) {
Instruction *insn = block->instructions[phi_idx].get();
assert(is_phi(insn));
/* directly insert into the predecessors live-out set */
std::vector<unsigned>& preds = insn->opcode == aco_opcode::p_phi
? block->logical_preds
: block->linear_preds;
for (unsigned i = 0; i < preds.size(); ++i) {
Operand &operand = insn->operands[i];
if (!operand.isTemp()) {
continue;
}
/* check if we changed an already processed block */
const bool inserted = live_temps[preds[i]].insert(operand.getTemp()).second;
if (inserted) {
operand.setKill(true);
worklist.insert(preds[i]);
if (insn->opcode == aco_opcode::p_phi && operand.getTemp().type() == RegType::sgpr)
phi_sgpr_ops[preds[i]] += operand.size();
}
}
phi_idx--;
}
if (!(block->index != 0 || (live_vgprs.empty() && live_sgprs.empty()))) {
aco_print_program(program, stderr);
fprintf(stderr, "These temporaries are never defined or are defined after use:\n");