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Move special RPO computation into separate class.

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R=jarin@chromium.org

Review URL: https://codereview.chromium.org/673753003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24853 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
mstarzinger@chromium.org 2014-10-23 16:29:43 +00:00
parent 48a52aef74
commit f194b3cc9e
2 changed files with 465 additions and 434 deletions
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879
src/compiler/scheduler.cc
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@ -49,7 +49,7 @@ Schedule* Scheduler::ComputeSchedule(ZonePool* zone_pool, Graph* graph) {
Scheduler scheduler(zone_scope.zone(), graph, schedule); Scheduler scheduler(zone_scope.zone(), graph, schedule);
scheduler.BuildCFG(); scheduler.BuildCFG();
Scheduler::ComputeSpecialRPO(zone_pool, schedule); scheduler.ComputeSpecialRPONumbering();
scheduler.GenerateImmediateDominatorTree(); scheduler.GenerateImmediateDominatorTree();
scheduler.PrepareUses(); scheduler.PrepareUses();
@ -173,7 +173,7 @@ BasicBlock* Scheduler::GetCommonDominator(BasicBlock* b1, BasicBlock* b2) {
// ----------------------------------------------------------------------------- // -----------------------------------------------------------------------------
// Phase 1: Build control-flow graph and dominator tree. // Phase 1: Build control-flow graph.
// Internal class to build a control flow graph (i.e the basic blocks and edges // Internal class to build a control flow graph (i.e the basic blocks and edges
@ -395,10 +395,456 @@ void Scheduler::BuildCFG() {
} }
// -----------------------------------------------------------------------------
// Phase 2: Compute special RPO and dominator tree.
// Compute the special reverse-post-order block ordering, which is essentially
// a RPO of the graph where loop bodies are contiguous. Properties:
// 1. If block A is a predecessor of B, then A appears before B in the order,
// unless B is a loop header and A is in the loop headed at B
// (i.e. A -> B is a backedge).
// => If block A dominates block B, then A appears before B in the order.
// => If block A is a loop header, A appears before all blocks in the loop
// headed at A.
// 2. All loops are contiguous in the order (i.e. no intervening blocks that
// do not belong to the loop.)
// Note a simple RPO traversal satisfies (1) but not (2).
class SpecialRPONumberer {
public:
SpecialRPONumberer(Zone* zone, Schedule* schedule)
: zone_(zone), schedule_(schedule) {}
void ComputeSpecialRPO() {
// RPO should not have been computed for this schedule yet.
CHECK_EQ(kBlockUnvisited1, schedule_->start()->rpo_number());
CHECK_EQ(0, static_cast<int>(schedule_->rpo_order()->size()));
// Perform an iterative RPO traversal using an explicit stack,
// recording backedges that form cycles. O(|B|).
ZoneList<std::pair<BasicBlock*, size_t> > backedges(1, zone_);
SpecialRPOStackFrame* stack = zone_->NewArray<SpecialRPOStackFrame>(
static_cast<int>(schedule_->BasicBlockCount()));
BasicBlock* entry = schedule_->start();
BlockList* order = NULL;
int stack_depth = Push(stack, 0, entry, kBlockUnvisited1);
int num_loops = 0;
while (stack_depth > 0) {
int current = stack_depth - 1;
SpecialRPOStackFrame* frame = stack + current;
if (frame->index < frame->block->SuccessorCount()) {
// Process the next successor.
BasicBlock* succ = frame->block->SuccessorAt(frame->index++);
if (succ->rpo_number() == kBlockVisited1) continue;
if (succ->rpo_number() == kBlockOnStack) {
// The successor is on the stack, so this is a backedge (cycle).
backedges.Add(
std::pair<BasicBlock*, size_t>(frame->block, frame->index - 1),
zone_);
if (succ->loop_end() < 0) {
// Assign a new loop number to the header if it doesn't have one.
succ->set_loop_end(num_loops++);
}
} else {
// Push the successor onto the stack.
DCHECK(succ->rpo_number() == kBlockUnvisited1);
stack_depth = Push(stack, stack_depth, succ, kBlockUnvisited1);
}
} else {
// Finished with all successors; pop the stack and add the block.
order = order->Add(zone_, frame->block);
frame->block->set_rpo_number(kBlockVisited1);
stack_depth--;
}
}
// If no loops were encountered, then the order we computed was correct.
LoopInfo* loops = NULL;
if (num_loops != 0) {
// Otherwise, compute the loop information from the backedges in order
// to perform a traversal that groups loop bodies together.
loops = ComputeLoopInfo(stack, num_loops, schedule_->BasicBlockCount(),
&backedges);
// Initialize the "loop stack". Note the entry could be a loop header.
LoopInfo* loop = entry->IsLoopHeader() ? &loops[entry->loop_end()] : NULL;
order = NULL;
// Perform an iterative post-order traversal, visiting loop bodies before
// edges that lead out of loops. Visits each block once, but linking loop
// sections together is linear in the loop size, so overall is
// O(|B| + max(loop_depth) * max(|loop|))
stack_depth = Push(stack, 0, entry, kBlockUnvisited2);
while (stack_depth > 0) {
SpecialRPOStackFrame* frame = stack + (stack_depth - 1);
BasicBlock* block = frame->block;
BasicBlock* succ = NULL;
if (frame->index < block->SuccessorCount()) {
// Process the next normal successor.
succ = block->SuccessorAt(frame->index++);
} else if (block->IsLoopHeader()) {
// Process additional outgoing edges from the loop header.
if (block->rpo_number() == kBlockOnStack) {
// Finish the loop body the first time the header is left on the
// stack.
DCHECK(loop != NULL && loop->header == block);
loop->start = order->Add(zone_, block);
order = loop->end;
block->set_rpo_number(kBlockVisited2);
// Pop the loop stack and continue visiting outgoing edges within
// the context of the outer loop, if any.
loop = loop->prev;
// We leave the loop header on the stack; the rest of this iteration
// and later iterations will go through its outgoing edges list.
}
// Use the next outgoing edge if there are any.
int outgoing_index =
static_cast<int>(frame->index - block->SuccessorCount());
LoopInfo* info = &loops[block->loop_end()];
DCHECK(loop != info);
if (info->outgoing != NULL &&
outgoing_index < info->outgoing->length()) {
succ = info->outgoing->at(outgoing_index);
frame->index++;
}
}
if (succ != NULL) {
// Process the next successor.
if (succ->rpo_number() == kBlockOnStack) continue;
if (succ->rpo_number() == kBlockVisited2) continue;
DCHECK(succ->rpo_number() == kBlockUnvisited2);
if (loop != NULL && !loop->members->Contains(succ->id().ToInt())) {
// The successor is not in the current loop or any nested loop.
// Add it to the outgoing edges of this loop and visit it later.
loop->AddOutgoing(zone_, succ);
} else {
// Push the successor onto the stack.
stack_depth = Push(stack, stack_depth, succ, kBlockUnvisited2);
if (succ->IsLoopHeader()) {
// Push the inner loop onto the loop stack.
DCHECK(succ->loop_end() >= 0 && succ->loop_end() < num_loops);
LoopInfo* next = &loops[succ->loop_end()];
next->end = order;
next->prev = loop;
loop = next;
}
}
} else {
// Finished with all successors of the current block.
if (block->IsLoopHeader()) {
// If we are going to pop a loop header, then add its entire body.
LoopInfo* info = &loops[block->loop_end()];
for (BlockList* l = info->start; true; l = l->next) {
if (l->next == info->end) {
l->next = order;
info->end = order;
break;
}
}
order = info->start;
} else {
// Pop a single node off the stack and add it to the order.
order = order->Add(zone_, block);
block->set_rpo_number(kBlockVisited2);
}
stack_depth--;
}
}
}
// Construct the final order from the list.
BasicBlockVector* final_order = schedule_->rpo_order();
order->Serialize(final_order);
// Compute the correct loop header for every block and set the correct loop
// ends.
LoopInfo* current_loop = NULL;
BasicBlock* current_header = NULL;
int loop_depth = 0;
for (BasicBlockVectorIter i = final_order->begin(); i != final_order->end();
++i) {
BasicBlock* current = *i;
current->set_loop_header(current_header);
if (current->IsLoopHeader()) {
loop_depth++;
current_loop = &loops[current->loop_end()];
BlockList* end = current_loop->end;
current->set_loop_end(end == NULL
? static_cast<int>(final_order->size())
: end->block->rpo_number());
current_header = current_loop->header;
Trace("B%d is a loop header, increment loop depth to %d\n",
current->id().ToInt(), loop_depth);
} else {
while (current_header != NULL &&
current->rpo_number() >= current_header->loop_end()) {
DCHECK(current_header->IsLoopHeader());
DCHECK(current_loop != NULL);
current_loop = current_loop->prev;
current_header = current_loop == NULL ? NULL : current_loop->header;
--loop_depth;
}
}
current->set_loop_depth(loop_depth);
if (current->loop_header() == NULL) {
Trace("B%d is not in a loop (depth == %d)\n", current->id().ToInt(),
current->loop_depth());
} else {
Trace("B%d has loop header B%d, (depth == %d)\n", current->id().ToInt(),
current->loop_header()->id().ToInt(), current->loop_depth());
}
}
// Compute the assembly order (non-deferred code first, deferred code
// afterwards).
int32_t number = 0;
for (auto block : *final_order) {
if (block->deferred()) continue;
block->set_ao_number(number++);
}
for (auto block : *final_order) {
if (!block->deferred()) continue;
block->set_ao_number(number++);
}
#if DEBUG
if (FLAG_trace_turbo_scheduler) PrintRPO(num_loops, loops, final_order);
VerifySpecialRPO(num_loops, loops, final_order);
#endif
}
private:
// Numbering for BasicBlockData.rpo_number_ for this block traversal:
static const int kBlockOnStack = -2;
static const int kBlockVisited1 = -3;
static const int kBlockVisited2 = -4;
static const int kBlockUnvisited1 = -1;
static const int kBlockUnvisited2 = kBlockVisited1;
struct SpecialRPOStackFrame {
BasicBlock* block;
size_t index;
};
struct BlockList {
BasicBlock* block;
BlockList* next;
BlockList* Add(Zone* zone, BasicBlock* b) {
BlockList* list = static_cast<BlockList*>(zone->New(sizeof(BlockList)));
list->block = b;
list->next = this;
return list;
}
void Serialize(BasicBlockVector* final_order) {
for (BlockList* l = this; l != NULL; l = l->next) {
l->block->set_rpo_number(static_cast<int>(final_order->size()));
final_order->push_back(l->block);
}
}
};
struct LoopInfo {
BasicBlock* header;
ZoneList<BasicBlock*>* outgoing;
BitVector* members;
LoopInfo* prev;
BlockList* end;
BlockList* start;
void AddOutgoing(Zone* zone, BasicBlock* block) {
if (outgoing == NULL) {
outgoing = new (zone) ZoneList<BasicBlock*>(2, zone);
}
outgoing->Add(block, zone);
}
};
int Push(SpecialRPOStackFrame* stack, int depth, BasicBlock* child,
int unvisited) {
if (child->rpo_number() == unvisited) {
stack[depth].block = child;
stack[depth].index = 0;
child->set_rpo_number(kBlockOnStack);
return depth + 1;
}
return depth;
}
// Computes loop membership from the backedges of the control flow graph.
LoopInfo* ComputeLoopInfo(
SpecialRPOStackFrame* queue, int num_loops, size_t num_blocks,
ZoneList<std::pair<BasicBlock*, size_t> >* backedges) {
LoopInfo* loops = zone_->NewArray<LoopInfo>(num_loops);
memset(loops, 0, num_loops * sizeof(LoopInfo));
// Compute loop membership starting from backedges.
// O(max(loop_depth) * max(|loop|)
for (int i = 0; i < backedges->length(); i++) {
BasicBlock* member = backedges->at(i).first;
BasicBlock* header = member->SuccessorAt(backedges->at(i).second);
int loop_num = header->loop_end();
if (loops[loop_num].header == NULL) {
loops[loop_num].header = header;
loops[loop_num].members =
new (zone_) BitVector(static_cast<int>(num_blocks), zone_);
}
int queue_length = 0;
if (member != header) {
// As long as the header doesn't have a backedge to itself,
// Push the member onto the queue and process its predecessors.
if (!loops[loop_num].members->Contains(member->id().ToInt())) {
loops[loop_num].members->Add(member->id().ToInt());
}
queue[queue_length++].block = member;
}
// Propagate loop membership backwards. All predecessors of M up to the
// loop header H are members of the loop too. O(|blocks between M and H|).
while (queue_length > 0) {
BasicBlock* block = queue[--queue_length].block;
for (size_t i = 0; i < block->PredecessorCount(); i++) {
BasicBlock* pred = block->PredecessorAt(i);
if (pred != header) {
if (!loops[loop_num].members->Contains(pred->id().ToInt())) {
loops[loop_num].members->Add(pred->id().ToInt());
queue[queue_length++].block = pred;
}
}
}
}
}
return loops;
}
#if DEBUG
void PrintRPO(int num_loops, LoopInfo* loops, BasicBlockVector* order) {
OFStream os(stdout);
os << "-- RPO with " << num_loops << " loops ";
if (num_loops > 0) {
os << "(";
for (int i = 0; i < num_loops; i++) {
if (i > 0) os << " ";
os << "B" << loops[i].header->id();
}
os << ") ";
}
os << "-- \n";
for (size_t i = 0; i < order->size(); i++) {
BasicBlock* block = (*order)[i];
BasicBlock::Id bid = block->id();
// TODO(jarin,svenpanne): Add formatting here once we have support for
// that in streams (we want an equivalent of PrintF("%5d:", i) here).
os << i << ":";
for (int j = 0; j < num_loops; j++) {
bool membership = loops[j].members->Contains(bid.ToInt());
bool range = loops[j].header->LoopContains(block);
os << (membership ? " |" : " ");
os << (range ? "x" : " ");
}
os << " B" << bid << ": ";
if (block->loop_end() >= 0) {
os << " range: [" << block->rpo_number() << ", " << block->loop_end()
<< ")";
}
os << "\n";
}
}
void VerifySpecialRPO(int num_loops, LoopInfo* loops,
BasicBlockVector* order) {
DCHECK(order->size() > 0);
DCHECK((*order)[0]->id().ToInt() == 0); // entry should be first.
for (int i = 0; i < num_loops; i++) {
LoopInfo* loop = &loops[i];
BasicBlock* header = loop->header;
DCHECK(header != NULL);
DCHECK(header->rpo_number() >= 0);
DCHECK(header->rpo_number() < static_cast<int>(order->size()));
DCHECK(header->loop_end() >= 0);
DCHECK(header->loop_end() <= static_cast<int>(order->size()));
DCHECK(header->loop_end() > header->rpo_number());
// Verify the start ... end list relationship.
int links = 0;
BlockList* l = loop->start;
DCHECK(l != NULL && l->block == header);
bool end_found;
while (true) {
if (l == NULL || l == loop->end) {
end_found = (loop->end == l);
break;
}
// The list should be in same order as the final result.
DCHECK(l->block->rpo_number() == links + loop->header->rpo_number());
links++;
l = l->next;
DCHECK(links < static_cast<int>(2 * order->size())); // cycle?
}
DCHECK(links > 0);
DCHECK(links == (header->loop_end() - header->rpo_number()));
DCHECK(end_found);
// Check the contiguousness of loops.
int count = 0;
for (int j = 0; j < static_cast<int>(order->size()); j++) {
BasicBlock* block = order->at(j);
DCHECK(block->rpo_number() == j);
if (j < header->rpo_number() || j >= header->loop_end()) {
DCHECK(!loop->members->Contains(block->id().ToInt()));
} else {
if (block == header) {
DCHECK(!loop->members->Contains(block->id().ToInt()));
} else {
DCHECK(loop->members->Contains(block->id().ToInt()));
}
count++;
}
}
DCHECK(links == count);
}
}
#endif // DEBUG
Zone* zone_;
Schedule* schedule_;
};
BasicBlockVector* Scheduler::ComputeSpecialRPO(ZonePool* zone_pool,
Schedule* schedule) {
ZonePool::Scope zone_scope(zone_pool);
Zone* zone = zone_scope.zone();
SpecialRPONumberer numberer(zone, schedule);
numberer.ComputeSpecialRPO();
return schedule->rpo_order();
}
void Scheduler::ComputeSpecialRPONumbering() {
Trace("--- COMPUTING SPECIAL RPO ----------------------------------\n");
SpecialRPONumberer numberer(zone_, schedule_);
numberer.ComputeSpecialRPO();
}
void Scheduler::GenerateImmediateDominatorTree() { void Scheduler::GenerateImmediateDominatorTree() {
// Build the dominator graph. TODO(danno): consider using Lengauer & Tarjan's
// if this becomes really slow.
Trace("--- IMMEDIATE BLOCK DOMINATORS -----------------------------\n"); Trace("--- IMMEDIATE BLOCK DOMINATORS -----------------------------\n");
// Build the dominator graph.
// TODO(danno): consider using Lengauer & Tarjan's if this becomes too slow.
for (size_t i = 0; i < schedule_->rpo_order_.size(); i++) { for (size_t i = 0; i < schedule_->rpo_order_.size(); i++) {
BasicBlock* current_rpo = schedule_->rpo_order_[i]; BasicBlock* current_rpo = schedule_->rpo_order_[i];
if (current_rpo != schedule_->start()) { if (current_rpo != schedule_->start()) {
@ -428,7 +874,7 @@ void Scheduler::GenerateImmediateDominatorTree() {
// ----------------------------------------------------------------------------- // -----------------------------------------------------------------------------
// Phase 2: Prepare use counts for nodes. // Phase 3: Prepare use counts for nodes.
class PrepareUsesVisitor : public NullNodeVisitor { class PrepareUsesVisitor : public NullNodeVisitor {
@ -490,7 +936,7 @@ void Scheduler::PrepareUses() {
// ----------------------------------------------------------------------------- // -----------------------------------------------------------------------------
// Phase 3: Schedule nodes early. // Phase 4: Schedule nodes early.
class ScheduleEarlyNodeVisitor : public NullNodeVisitor { class ScheduleEarlyNodeVisitor : public NullNodeVisitor {
@ -567,7 +1013,7 @@ void Scheduler::ScheduleEarly() {
// ----------------------------------------------------------------------------- // -----------------------------------------------------------------------------
// Phase 4: Schedule nodes late. // Phase 5: Schedule nodes late.
class ScheduleLateNodeVisitor { class ScheduleLateNodeVisitor {
@ -835,425 +1281,6 @@ void Scheduler::ConnectFloatingControlSubgraph(BasicBlock* block, Node* end) {
block_start->op()->mnemonic()); block_start->op()->mnemonic());
} }
// Numbering for BasicBlockData.rpo_number_ for this block traversal:
static const int kBlockOnStack = -2;
static const int kBlockVisited1 = -3;
static const int kBlockVisited2 = -4;
static const int kBlockUnvisited1 = -1;
static const int kBlockUnvisited2 = kBlockVisited1;
struct SpecialRPOStackFrame {
BasicBlock* block;
size_t index;
};
struct BlockList {
BasicBlock* block;
BlockList* next;
BlockList* Add(Zone* zone, BasicBlock* b) {
BlockList* list = static_cast<BlockList*>(zone->New(sizeof(BlockList)));
list->block = b;
list->next = this;
return list;
}
void Serialize(BasicBlockVector* final_order) {
for (BlockList* l = this; l != NULL; l = l->next) {
l->block->set_rpo_number(static_cast<int>(final_order->size()));
final_order->push_back(l->block);
}
}
};
struct LoopInfo {
BasicBlock* header;
ZoneList<BasicBlock*>* outgoing;
BitVector* members;
LoopInfo* prev;
BlockList* end;
BlockList* start;
void AddOutgoing(Zone* zone, BasicBlock* block) {
if (outgoing == NULL) outgoing = new (zone) ZoneList<BasicBlock*>(2, zone);
outgoing->Add(block, zone);
}
};
static int Push(SpecialRPOStackFrame* stack, int depth, BasicBlock* child,
int unvisited) {
if (child->rpo_number() == unvisited) {
stack[depth].block = child;
stack[depth].index = 0;
child->set_rpo_number(kBlockOnStack);
return depth + 1;
}
return depth;
}
// Computes loop membership from the backedges of the control flow graph.
static LoopInfo* ComputeLoopInfo(
Zone* zone, SpecialRPOStackFrame* queue, int num_loops, size_t num_blocks,
ZoneList<std::pair<BasicBlock*, size_t> >* backedges) {
LoopInfo* loops = zone->NewArray<LoopInfo>(num_loops);
memset(loops, 0, num_loops * sizeof(LoopInfo));
// Compute loop membership starting from backedges.
// O(max(loop_depth) * max(|loop|)
for (int i = 0; i < backedges->length(); i++) {
BasicBlock* member = backedges->at(i).first;
BasicBlock* header = member->SuccessorAt(backedges->at(i).second);
int loop_num = header->loop_end();
if (loops[loop_num].header == NULL) {
loops[loop_num].header = header;
loops[loop_num].members =
new (zone) BitVector(static_cast<int>(num_blocks), zone);
}
int queue_length = 0;
if (member != header) {
// As long as the header doesn't have a backedge to itself,
// Push the member onto the queue and process its predecessors.
if (!loops[loop_num].members->Contains(member->id().ToInt())) {
loops[loop_num].members->Add(member->id().ToInt());
}
queue[queue_length++].block = member;
}
// Propagate loop membership backwards. All predecessors of M up to the
// loop header H are members of the loop too. O(|blocks between M and H|).
while (queue_length > 0) {
BasicBlock* block = queue[--queue_length].block;
for (size_t i = 0; i < block->PredecessorCount(); i++) {
BasicBlock* pred = block->PredecessorAt(i);
if (pred != header) {
if (!loops[loop_num].members->Contains(pred->id().ToInt())) {
loops[loop_num].members->Add(pred->id().ToInt());
queue[queue_length++].block = pred;
}
}
}
}
}
return loops;
}
#if DEBUG
static void PrintRPO(int num_loops, LoopInfo* loops, BasicBlockVector* order) {
OFStream os(stdout);
os << "-- RPO with " << num_loops << " loops ";
if (num_loops > 0) {
os << "(";
for (int i = 0; i < num_loops; i++) {
if (i > 0) os << " ";
os << "B" << loops[i].header->id();
}
os << ") ";
}
os << "-- \n";
for (size_t i = 0; i < order->size(); i++) {
BasicBlock* block = (*order)[i];
BasicBlock::Id bid = block->id();
// TODO(jarin,svenpanne): Add formatting here once we have support for that
// in streams (we want an equivalent of PrintF("%5d:", i) here).
os << i << ":";
for (int j = 0; j < num_loops; j++) {
bool membership = loops[j].members->Contains(bid.ToInt());
bool range = loops[j].header->LoopContains(block);
os << (membership ? " |" : " ");
os << (range ? "x" : " ");
}
os << " B" << bid << ": ";
if (block->loop_end() >= 0) {
os << " range: [" << block->rpo_number() << ", " << block->loop_end()
<< ")";
}
os << "\n";
}
}
static void VerifySpecialRPO(int num_loops, LoopInfo* loops,
BasicBlockVector* order) {
DCHECK(order->size() > 0);
DCHECK((*order)[0]->id().ToInt() == 0); // entry should be first.
for (int i = 0; i < num_loops; i++) {
LoopInfo* loop = &loops[i];
BasicBlock* header = loop->header;
DCHECK(header != NULL);
DCHECK(header->rpo_number() >= 0);
DCHECK(header->rpo_number() < static_cast<int>(order->size()));
DCHECK(header->loop_end() >= 0);
DCHECK(header->loop_end() <= static_cast<int>(order->size()));
DCHECK(header->loop_end() > header->rpo_number());
// Verify the start ... end list relationship.
int links = 0;
BlockList* l = loop->start;
DCHECK(l != NULL && l->block == header);
bool end_found;
while (true) {
if (l == NULL || l == loop->end) {
end_found = (loop->end == l);
break;
}
// The list should be in same order as the final result.
DCHECK(l->block->rpo_number() == links + loop->header->rpo_number());
links++;
l = l->next;
DCHECK(links < static_cast<int>(2 * order->size())); // cycle?
}
DCHECK(links > 0);
DCHECK(links == (header->loop_end() - header->rpo_number()));
DCHECK(end_found);
// Check the contiguousness of loops.
int count = 0;
for (int j = 0; j < static_cast<int>(order->size()); j++) {
BasicBlock* block = order->at(j);
DCHECK(block->rpo_number() == j);
if (j < header->rpo_number() || j >= header->loop_end()) {
DCHECK(!loop->members->Contains(block->id().ToInt()));
} else {
if (block == header) {
DCHECK(!loop->members->Contains(block->id().ToInt()));
} else {
DCHECK(loop->members->Contains(block->id().ToInt()));
}
count++;
}
}
DCHECK(links == count);
}
}
#endif // DEBUG
// Compute the special reverse-post-order block ordering, which is essentially
// a RPO of the graph where loop bodies are contiguous. Properties:
// 1. If block A is a predecessor of B, then A appears before B in the order,
// unless B is a loop header and A is in the loop headed at B
// (i.e. A -> B is a backedge).
// => If block A dominates block B, then A appears before B in the order.
// => If block A is a loop header, A appears before all blocks in the loop
// headed at A.
// 2. All loops are contiguous in the order (i.e. no intervening blocks that
// do not belong to the loop.)
// Note a simple RPO traversal satisfies (1) but not (3).
BasicBlockVector* Scheduler::ComputeSpecialRPO(ZonePool* zone_pool,
Schedule* schedule) {
ZonePool::Scope zone_scope(zone_pool);
Zone* zone = zone_scope.zone();
Trace("--- COMPUTING SPECIAL RPO ----------------------------------\n");
// RPO should not have been computed for this schedule yet.
CHECK_EQ(kBlockUnvisited1, schedule->start()->rpo_number());
CHECK_EQ(0, static_cast<int>(schedule->rpo_order_.size()));
// Perform an iterative RPO traversal using an explicit stack,
// recording backedges that form cycles. O(|B|).
ZoneList<std::pair<BasicBlock*, size_t> > backedges(1, zone);
SpecialRPOStackFrame* stack = zone->NewArray<SpecialRPOStackFrame>(
static_cast<int>(schedule->BasicBlockCount()));
BasicBlock* entry = schedule->start();
BlockList* order = NULL;
int stack_depth = Push(stack, 0, entry, kBlockUnvisited1);
int num_loops = 0;
while (stack_depth > 0) {
int current = stack_depth - 1;
SpecialRPOStackFrame* frame = stack + current;
if (frame->index < frame->block->SuccessorCount()) {
// Process the next successor.
BasicBlock* succ = frame->block->SuccessorAt(frame->index++);
if (succ->rpo_number() == kBlockVisited1) continue;
if (succ->rpo_number() == kBlockOnStack) {
// The successor is on the stack, so this is a backedge (cycle).
backedges.Add(
std::pair<BasicBlock*, size_t>(frame->block, frame->index - 1),
zone);
if (succ->loop_end() < 0) {
// Assign a new loop number to the header if it doesn't have one.
succ->set_loop_end(num_loops++);
}
} else {
// Push the successor onto the stack.
DCHECK(succ->rpo_number() == kBlockUnvisited1);
stack_depth = Push(stack, stack_depth, succ, kBlockUnvisited1);
}
} else {
// Finished with all successors; pop the stack and add the block.
order = order->Add(zone, frame->block);
frame->block->set_rpo_number(kBlockVisited1);
stack_depth--;
}
}
// If no loops were encountered, then the order we computed was correct.
LoopInfo* loops = NULL;
if (num_loops != 0) {
// Otherwise, compute the loop information from the backedges in order
// to perform a traversal that groups loop bodies together.
loops = ComputeLoopInfo(zone, stack, num_loops, schedule->BasicBlockCount(),
&backedges);
// Initialize the "loop stack". Note the entry could be a loop header.
LoopInfo* loop = entry->IsLoopHeader() ? &loops[entry->loop_end()] : NULL;
order = NULL;
// Perform an iterative post-order traversal, visiting loop bodies before
// edges that lead out of loops. Visits each block once, but linking loop
// sections together is linear in the loop size, so overall is
// O(|B| + max(loop_depth) * max(|loop|))
stack_depth = Push(stack, 0, entry, kBlockUnvisited2);
while (stack_depth > 0) {
SpecialRPOStackFrame* frame = stack + (stack_depth - 1);
BasicBlock* block = frame->block;
BasicBlock* succ = NULL;
if (frame->index < block->SuccessorCount()) {
// Process the next normal successor.
succ = block->SuccessorAt(frame->index++);
} else if (block->IsLoopHeader()) {
// Process additional outgoing edges from the loop header.
if (block->rpo_number() == kBlockOnStack) {
// Finish the loop body the first time the header is left on the
// stack.
DCHECK(loop != NULL && loop->header == block);
loop->start = order->Add(zone, block);
order = loop->end;
block->set_rpo_number(kBlockVisited2);
// Pop the loop stack and continue visiting outgoing edges within the
// the context of the outer loop, if any.
loop = loop->prev;
// We leave the loop header on the stack; the rest of this iteration
// and later iterations will go through its outgoing edges list.
}
// Use the next outgoing edge if there are any.
int outgoing_index =
static_cast<int>(frame->index - block->SuccessorCount());
LoopInfo* info = &loops[block->loop_end()];
DCHECK(loop != info);
if (info->outgoing != NULL &&
outgoing_index < info->outgoing->length()) {
succ = info->outgoing->at(outgoing_index);
frame->index++;
}
}
if (succ != NULL) {
// Process the next successor.
if (succ->rpo_number() == kBlockOnStack) continue;
if (succ->rpo_number() == kBlockVisited2) continue;
DCHECK(succ->rpo_number() == kBlockUnvisited2);
if (loop != NULL && !loop->members->Contains(succ->id().ToInt())) {
// The successor is not in the current loop or any nested loop.
// Add it to the outgoing edges of this loop and visit it later.
loop->AddOutgoing(zone, succ);
} else {
// Push the successor onto the stack.
stack_depth = Push(stack, stack_depth, succ, kBlockUnvisited2);
if (succ->IsLoopHeader()) {
// Push the inner loop onto the loop stack.
DCHECK(succ->loop_end() >= 0 && succ->loop_end() < num_loops);
LoopInfo* next = &loops[succ->loop_end()];
next->end = order;
next->prev = loop;
loop = next;
}
}
} else {
// Finished with all successors of the current block.
if (block->IsLoopHeader()) {
// If we are going to pop a loop header, then add its entire body.
LoopInfo* info = &loops[block->loop_end()];
for (BlockList* l = info->start; true; l = l->next) {
if (l->next == info->end) {
l->next = order;
info->end = order;
break;
}
}
order = info->start;
} else {
// Pop a single node off the stack and add it to the order.
order = order->Add(zone, block);
block->set_rpo_number(kBlockVisited2);
}
stack_depth--;
}
}
}
// Construct the final order from the list.
BasicBlockVector* final_order = &schedule->rpo_order_;
order->Serialize(final_order);
// Compute the correct loop header for every block and set the correct loop
// ends.
LoopInfo* current_loop = NULL;
BasicBlock* current_header = NULL;
int loop_depth = 0;
for (BasicBlockVectorIter i = final_order->begin(); i != final_order->end();
++i) {
BasicBlock* current = *i;
current->set_loop_header(current_header);
if (current->IsLoopHeader()) {
loop_depth++;
current_loop = &loops[current->loop_end()];
BlockList* end = current_loop->end;
current->set_loop_end(end == NULL ? static_cast<int>(final_order->size())
: end->block->rpo_number());
current_header = current_loop->header;
Trace("B%d is a loop header, increment loop depth to %d\n",
current->id().ToInt(), loop_depth);
} else {
while (current_header != NULL &&
current->rpo_number() >= current_header->loop_end()) {
DCHECK(current_header->IsLoopHeader());
DCHECK(current_loop != NULL);
current_loop = current_loop->prev;
current_header = current_loop == NULL ? NULL : current_loop->header;
--loop_depth;
}
}
current->set_loop_depth(loop_depth);
if (current->loop_header() == NULL) {
Trace("B%d is not in a loop (depth == %d)\n", current->id().ToInt(),
current->loop_depth());
} else {
Trace("B%d has loop header B%d, (depth == %d)\n", current->id().ToInt(),
current->loop_header()->id().ToInt(), current->loop_depth());
}
}
// Compute the assembly order (non-deferred code first, deferred code
// afterwards).
int32_t number = 0;
for (auto block : *final_order) {
if (block->deferred()) continue;
block->set_ao_number(number++);
}
for (auto block : *final_order) {
if (!block->deferred()) continue;
block->set_ao_number(number++);
}
#if DEBUG
if (FLAG_trace_turbo_scheduler) PrintRPO(num_loops, loops, final_order);
VerifySpecialRPO(num_loops, loops, final_order);
#endif
return final_order;
}
} // namespace compiler } // namespace compiler
} // namespace internal } // namespace internal
} // namespace v8 } // namespace v8

20
src/compiler/scheduler.h
View File

@ -45,10 +45,10 @@ class Scheduler {
Zone* zone_; Zone* zone_;
Graph* graph_; Graph* graph_;
Schedule* schedule_; Schedule* schedule_;
NodeVectorVector scheduled_nodes_; NodeVectorVector scheduled_nodes_; // Per-block list of nodes in reverse.
NodeVector schedule_root_nodes_; NodeVector schedule_root_nodes_; // Fixed root nodes seed the worklist.
ZoneQueue<Node*> schedule_queue_; ZoneQueue<Node*> schedule_queue_; // Worklist of schedulable nodes.
ZoneVector<SchedulerData> node_data_; ZoneVector<SchedulerData> node_data_; // Per-node data for all nodes.
bool has_floating_control_; bool has_floating_control_;
Scheduler(Zone* zone, Graph* graph, Schedule* schedule); Scheduler(Zone* zone, Graph* graph, Schedule* schedule);
@ -64,20 +64,24 @@ class Scheduler {
inline int GetRPONumber(BasicBlock* block); inline int GetRPONumber(BasicBlock* block);
BasicBlock* GetCommonDominator(BasicBlock* b1, BasicBlock* b2); BasicBlock* GetCommonDominator(BasicBlock* b1, BasicBlock* b2);
// Phase 1: Build control-flow graph and dominator tree. // Phase 1: Build control-flow graph.
friend class CFGBuilder; friend class CFGBuilder;
void BuildCFG(); void BuildCFG();
// Phase 2: Compute special RPO and dominator tree.
friend class SpecialRPONumberer;
void ComputeSpecialRPONumbering();
void GenerateImmediateDominatorTree(); void GenerateImmediateDominatorTree();
// Phase 2: Prepare use counts for nodes. // Phase 3: Prepare use counts for nodes.
friend class PrepareUsesVisitor; friend class PrepareUsesVisitor;
void PrepareUses(); void PrepareUses();
// Phase 3: Schedule nodes early. // Phase 4: Schedule nodes early.
friend class ScheduleEarlyNodeVisitor; friend class ScheduleEarlyNodeVisitor;
void ScheduleEarly(); void ScheduleEarly();
// Phase 4: Schedule nodes late. // Phase 5: Schedule nodes late.
friend class ScheduleLateNodeVisitor; friend class ScheduleLateNodeVisitor;
void ScheduleLate(); void ScheduleLate();