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Reland "More aggressive reuse of spill slots in the register allocator."

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This relands r23532 (https://codereview.chromium.org/310003003). Flakes seem unrelated.

TBR=titzer@chromium.org

Review URL: https://codereview.chromium.org/522173003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23536 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
jarin@chromium.org 2014-08-31 07:27:38 +00:00
parent 616572535b
commit d8414c57fe
3 changed files with 312 additions and 44 deletions
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15
src/hydrogen.cc
View File

@ -12359,12 +12359,17 @@ void HTracer::TraceLiveRange(LiveRange* range, const char* type,
trace_.Add(" \"%s\"", Register::AllocationIndexToString(assigned_reg));
}
} else if (range->IsSpilled()) {
LOperand* op = range->TopLevel()->GetSpillOperand();
if (op->IsDoubleStackSlot()) {
trace_.Add(" \"double_stack:%d\"", op->index());
int index = -1;
if (range->TopLevel()->GetSpillRange()->id() != -1) {
index = range->TopLevel()->GetSpillRange()->id();
} else {
DCHECK(op->IsStackSlot());
trace_.Add(" \"stack:%d\"", op->index());
index = range->TopLevel()->GetSpillOperand()->index();
}
if (range->TopLevel()->Kind() == DOUBLE_REGISTERS) {
trace_.Add(" \"double_stack:%d\"", index);
} else {
DCHECK(range->TopLevel()->Kind() == GENERAL_REGISTERS);
trace_.Add(" \"stack:%d\"", index);
}
}
int parent_index = -1;

301
src/lithium-allocator.cc
View File

@ -109,7 +109,8 @@ LiveRange::LiveRange(int id, Zone* zone)
last_processed_use_(NULL),
current_hint_operand_(NULL),
spill_operand_(new (zone) LOperand()),
spill_start_index_(kMaxInt) {}
spill_start_index_(kMaxInt),
spill_range_(NULL) {}
void LiveRange::set_assigned_register(int reg, Zone* zone) {
@ -124,13 +125,15 @@ void LiveRange::MakeSpilled(Zone* zone) {
DCHECK(TopLevel()->HasAllocatedSpillOperand());
spilled_ = true;
assigned_register_ = kInvalidAssignment;
ConvertOperands(zone);
if (spill_range_ == NULL) {
ConvertOperands(zone);
}
}
bool LiveRange::HasAllocatedSpillOperand() const {
DCHECK(spill_operand_ != NULL);
return !spill_operand_->IsIgnored();
return !spill_operand_->IsIgnored() || spill_range_ != NULL;
}
@ -142,6 +145,19 @@ void LiveRange::SetSpillOperand(LOperand* operand) {
}
void LiveRange::CommitSpillOperand(LOperand* operand) {
DCHECK(spill_range_ != NULL);
DCHECK(!IsChild());
spill_range_ = NULL;
SetSpillOperand(operand);
for (LiveRange* range = this; range != NULL; range = range->next()) {
if (range->IsSpilled()) {
range->ConvertUsesToOperand(operand);
}
}
}
UsePosition* LiveRange::NextUsePosition(LifetimePosition start) {
UsePosition* use_pos = last_processed_use_;
if (use_pos == NULL) use_pos = first_pos();
@ -446,8 +462,7 @@ void LiveRange::AddUsePosition(LifetimePosition pos,
}
void LiveRange::ConvertOperands(Zone* zone) {
LOperand* op = CreateAssignedOperand(zone);
void LiveRange::ConvertUsesToOperand(LOperand* op) {
UsePosition* use_pos = first_pos();
while (use_pos != NULL) {
DCHECK(Start().Value() <= use_pos->pos().Value() &&
@ -463,6 +478,12 @@ void LiveRange::ConvertOperands(Zone* zone) {
}
void LiveRange::ConvertOperands(Zone* zone) {
LOperand* op = CreateAssignedOperand(zone);
ConvertUsesToOperand(op);
}
bool LiveRange::CanCover(LifetimePosition position) const {
if (IsEmpty()) return false;
return Start().Value() <= position.Value() &&
@ -521,6 +542,7 @@ LAllocator::LAllocator(int num_values, HGraph* graph)
active_live_ranges_(8, zone()),
inactive_live_ranges_(8, zone()),
reusable_slots_(8, zone()),
spill_ranges_(8, zone()),
next_virtual_register_(num_values),
first_artificial_register_(num_values),
mode_(UNALLOCATED_REGISTERS),
@ -1016,7 +1038,7 @@ void LAllocator::ResolvePhis(HBasicBlock* block) {
for (int i = 0; i < phis->length(); ++i) {
HPhi* phi = phis->at(i);
LUnallocated* phi_operand =
new (chunk()->zone()) LUnallocated(LUnallocated::NONE);
new (chunk()->zone()) LUnallocated(LUnallocated::ANY);
phi_operand->set_virtual_register(phi->id());
for (int j = 0; j < phi->OperandCount(); ++j) {
HValue* op = phi->OperandAt(j);
@ -1083,6 +1105,7 @@ bool LAllocator::Allocate(LChunk* chunk) {
if (!AllocationOk()) return false;
AllocateDoubleRegisters();
if (!AllocationOk()) return false;
ReuseSpillSlots();
PopulatePointerMaps();
ConnectRanges();
ResolveControlFlow();
@ -1090,6 +1113,139 @@ bool LAllocator::Allocate(LChunk* chunk) {
}
static bool AreUseIntervalsIntersecting(UseInterval* interval1,
UseInterval* interval2) {
while (interval1 != NULL && interval2 != NULL) {
if (interval1->start().Value() < interval2->start().Value()) {
if (interval1->end().Value() > interval2->start().Value()) {
return true;
}
interval1 = interval1->next();
} else {
if (interval2->end().Value() > interval1->start().Value()) {
return true;
}
interval2 = interval2->next();
}
}
return false;
}
SpillRange::SpillRange(LiveRange* range, int id, Zone* zone)
: id_(id), live_ranges_(1, zone), end_position_(range->End()) {
UseInterval* src = range->first_interval();
UseInterval* result = NULL;
UseInterval* node = NULL;
// Copy the nodes
while (src != NULL) {
UseInterval* new_node = new (zone) UseInterval(src->start(), src->end());
if (result == NULL) {
result = new_node;
} else {
node->set_next(new_node);
}
node = new_node;
src = src->next();
}
use_interval_ = result;
live_ranges_.Add(range, zone);
DCHECK(range->GetSpillRange() == NULL);
range->SetSpillRange(this);
}
bool SpillRange::IsIntersectingWith(SpillRange* other) {
if (End().Value() <= other->use_interval_->start().Value() ||
other->End().Value() <= use_interval_->start().Value()) {
return false;
}
return AreUseIntervalsIntersecting(use_interval_, other->use_interval_);
}
bool SpillRange::TryMerge(SpillRange* other, Zone* zone) {
if (Kind() == other->Kind() &&
!AreUseIntervalsIntersecting(use_interval_, other->use_interval_)) {
if (End().Value() < other->End().Value()) {
end_position_ = other->End();
}
MergeDisjointIntervals(other->use_interval_, zone);
other->use_interval_ = NULL;
for (int i = 0; i < other->live_ranges_.length(); i++) {
DCHECK(other->live_ranges_.at(i)->GetSpillRange() == other);
other->live_ranges_.at(i)->SetSpillRange(this);
}
live_ranges_.AddAll(other->live_ranges_, zone);
other->live_ranges_.Clear();
return true;
}
return false;
}
void SpillRange::SetOperand(LOperand* op) {
for (int i = 0; i < live_ranges_.length(); i++) {
DCHECK(live_ranges_.at(i)->GetSpillRange() == this);
live_ranges_.at(i)->CommitSpillOperand(op);
}
}
void SpillRange::MergeDisjointIntervals(UseInterval* other, Zone* zone) {
UseInterval* tail = NULL;
UseInterval* current = use_interval_;
while (other != NULL) {
// Make sure the 'current' list starts first
if (current == NULL || current->start().Value() > other->start().Value()) {
std::swap(current, other);
}
// Check disjointness
DCHECK(other == NULL || current->end().Value() <= other->start().Value());
// Append the 'current' node to the result accumulator and move forward
if (tail == NULL) {
use_interval_ = current;
} else {
tail->set_next(current);
}
tail = current;
current = current->next();
}
// Other list is empty => we are done
}
void LAllocator::ReuseSpillSlots() {
// Merge disjoint spill ranges
for (int i = 0; i < spill_ranges_.length(); i++) {
SpillRange* range = spill_ranges_.at(i);
if (!range->IsEmpty()) {
for (int j = i + 1; j < spill_ranges_.length(); j++) {
SpillRange* other = spill_ranges_.at(j);
if (!other->IsEmpty()) {
range->TryMerge(spill_ranges_.at(j), zone());
}
}
}
}
// Allocate slots for the merged spill ranges.
for (int i = 0; i < spill_ranges_.length(); i++) {
SpillRange* range = spill_ranges_.at(i);
if (!range->IsEmpty()) {
LOperand* op = chunk_->GetNextSpillSlot(range->Kind());
range->SetOperand(op);
}
}
}
void LAllocator::MeetRegisterConstraints() {
LAllocatorPhase phase("L_Register constraints", this);
const ZoneList<HBasicBlock*>* blocks = graph_->blocks();
@ -1480,6 +1636,102 @@ void LAllocator::AllocateDoubleRegisters() {
}
bool LAllocator::TryReuseSpillForPhi(LiveRange* range) {
DCHECK(!range->HasAllocatedSpillOperand());
if (range->IsChild()) {
return false;
}
HValue* instr = graph_->LookupValue(range->id());
if (instr == NULL || !instr->IsPhi()) {
return false;
}
// Count the number of spilled operands.
HPhi* phi = HPhi::cast(instr);
int spilled_count = 0;
LiveRange* first_op = NULL;
for (int i = 0; i < phi->OperandCount(); i++) {
HValue* op = phi->OperandAt(i);
LiveRange* op_range = LiveRangeFor(op->id());
if (op_range->GetSpillRange() != NULL) {
HBasicBlock* pred = instr->block()->predecessors()->at(i);
LifetimePosition pred_end = LifetimePosition::FromInstructionIndex(
pred->last_instruction_index());
while (op_range != NULL && !op_range->CanCover(pred_end)) {
op_range = op_range->next();
}
if (op_range != NULL && op_range->IsSpilled()) {
spilled_count++;
if (first_op == NULL) {
first_op = op_range->TopLevel();
}
}
}
}
// Only continue if more than half of the operands are spilled.
if (spilled_count * 2 <= phi->OperandCount()) {
return false;
}
// Try to merge the spilled operands and count the number of merged spilled
// operands.
DCHECK(first_op != NULL);
SpillRange* first_op_spill = first_op->GetSpillRange();
int num_merged = 1;
for (int i = 1; i < phi->OperandCount(); i++) {
HValue* op = phi->OperandAt(i);
LiveRange* op_range = LiveRangeFor(op->id());
SpillRange* op_spill = op_range->GetSpillRange();
if (op_spill != NULL) {
if (op_spill->id() == first_op_spill->id() ||
first_op_spill->TryMerge(op_spill, zone())) {
num_merged++;
}
}
}
// Only continue if enough operands could be merged to the
// same spill slot.
if (num_merged * 2 <= phi->OperandCount() ||
AreUseIntervalsIntersecting(first_op_spill->interval(),
range->first_interval())) {
return false;
}
// If the range does not need register soon, spill it to the merged
// spill range.
LifetimePosition next_pos = range->Start();
if (IsGapAt(next_pos.InstructionIndex())) {
next_pos = next_pos.NextInstruction();
}
UsePosition* pos = range->NextUsePositionRegisterIsBeneficial(next_pos);
if (pos == NULL) {
SpillRange* spill_range = AssignSpillRangeToLiveRange(range->TopLevel());
CHECK(first_op_spill->TryMerge(spill_range, zone()));
Spill(range);
return true;
} else if (pos->pos().Value() > range->Start().NextInstruction().Value()) {
SpillRange* spill_range = AssignSpillRangeToLiveRange(range->TopLevel());
CHECK(first_op_spill->TryMerge(spill_range, zone()));
SpillBetween(range, range->Start(), pos->pos());
if (!AllocationOk()) return false;
DCHECK(UnhandledIsSorted());
return true;
}
return false;
}
SpillRange* LAllocator::AssignSpillRangeToLiveRange(LiveRange* range) {
int spill_id = spill_ranges_.length();
SpillRange* spill_range = new (zone()) SpillRange(range, spill_id, zone());
spill_ranges_.Add(spill_range, zone());
return spill_range;
}
void LAllocator::AllocateRegisters() {
DCHECK(unhandled_live_ranges_.is_empty());
@ -1549,6 +1801,11 @@ void LAllocator::AllocateRegisters() {
}
}
if (TryReuseSpillForPhi(current)) {
continue;
}
if (!AllocationOk()) return;
for (int i = 0; i < active_live_ranges_.length(); ++i) {
LiveRange* cur_active = active_live_ranges_.at(i);
if (cur_active->End().Value() <= position.Value()) {
@ -1699,36 +1956,10 @@ bool LAllocator::UnhandledIsSorted() {
}
void LAllocator::FreeSpillSlot(LiveRange* range) {
// Check that we are the last range.
if (range->next() != NULL) return;
if (!range->TopLevel()->HasAllocatedSpillOperand()) return;
int index = range->TopLevel()->GetSpillOperand()->index();
if (index >= 0) {
reusable_slots_.Add(range, zone());
}
}
LOperand* LAllocator::TryReuseSpillSlot(LiveRange* range) {
if (reusable_slots_.is_empty()) return NULL;
if (reusable_slots_.first()->End().Value() >
range->TopLevel()->Start().Value()) {
return NULL;
}
LOperand* result = reusable_slots_.first()->TopLevel()->GetSpillOperand();
reusable_slots_.Remove(0);
return result;
}
void LAllocator::ActiveToHandled(LiveRange* range) {
DCHECK(active_live_ranges_.Contains(range));
active_live_ranges_.RemoveElement(range);
TraceAlloc("Moving live range %d from active to handled\n", range->id());
FreeSpillSlot(range);
}
@ -1744,7 +1975,6 @@ void LAllocator::InactiveToHandled(LiveRange* range) {
DCHECK(inactive_live_ranges_.Contains(range));
inactive_live_ranges_.RemoveElement(range);
TraceAlloc("Moving live range %d from inactive to handled\n", range->id());
FreeSpillSlot(range);
}
@ -1828,7 +2058,6 @@ bool LAllocator::TryAllocateFreeReg(LiveRange* current) {
AddToUnhandledSorted(tail);
}
// Register reg is available at the range start and is free until
// the range end.
DCHECK(pos.Value() >= current->End().Value());
@ -2136,9 +2365,7 @@ void LAllocator::Spill(LiveRange* range) {
LiveRange* first = range->TopLevel();
if (!first->HasAllocatedSpillOperand()) {
LOperand* op = TryReuseSpillSlot(range);
if (op == NULL) op = chunk_->GetNextSpillSlot(range->Kind());
first->SetSpillOperand(op);
AssignSpillRangeToLiveRange(first);
}
range->MakeSpilled(chunk()->zone());
}

40
src/lithium-allocator.h
View File

@ -153,6 +153,8 @@ class UseInterval: public ZoneObject {
LifetimePosition end_;
UseInterval* next_;
friend class LAllocator; // Assigns to next_.
friend class SpillRange; // Assigns to next_.
friend class LiveRange; // Assigns to start_.
};
@ -185,6 +187,8 @@ class UsePosition: public ZoneObject {
friend class LiveRange;
};
class SpillRange;
// Representation of SSA values' live ranges as a collection of (continuous)
// intervals over the instruction ordering.
class LiveRange: public ZoneObject {
@ -267,6 +271,10 @@ class LiveRange: public ZoneObject {
LOperand* GetSpillOperand() const { return spill_operand_; }
void SetSpillOperand(LOperand* operand);
void SetSpillRange(SpillRange* spill_range) { spill_range_ = spill_range; }
SpillRange* GetSpillRange() const { return spill_range_; }
void CommitSpillOperand(LOperand* operand);
void SetSpillStartIndex(int start) {
spill_start_index_ = Min(start, spill_start_index_);
}
@ -299,6 +307,7 @@ class LiveRange: public ZoneObject {
private:
void ConvertOperands(Zone* zone);
void ConvertUsesToOperand(LOperand* op);
UseInterval* FirstSearchIntervalForPosition(LifetimePosition position) const;
void AdvanceLastProcessedMarker(UseInterval* to_start_of,
LifetimePosition but_not_past) const;
@ -319,11 +328,36 @@ class LiveRange: public ZoneObject {
LOperand* current_hint_operand_;
LOperand* spill_operand_;
int spill_start_index_;
SpillRange* spill_range_;
friend class LAllocator; // Assigns to kind_.
};
class SpillRange : public ZoneObject {
public:
SpillRange(LiveRange* range, int id, Zone* zone);
bool TryMerge(SpillRange* other, Zone* zone);
void SetOperand(LOperand* op);
bool IsEmpty() { return live_ranges_.length() == 0; }
int id() const { return id_; }
UseInterval* interval() { return use_interval_; }
RegisterKind Kind() const { return live_ranges_.at(0)->Kind(); }
LifetimePosition End() const { return end_position_; }
bool IsIntersectingWith(SpillRange* other);
private:
int id_;
ZoneList<LiveRange*> live_ranges_;
UseInterval* use_interval_;
LifetimePosition end_position_;
// Merge intervals, making sure the use intervals are sorted
void MergeDisjointIntervals(UseInterval* other, Zone* zone);
};
class LAllocator BASE_EMBEDDED {
public:
LAllocator(int first_virtual_register, HGraph* graph);
@ -390,6 +424,7 @@ class LAllocator BASE_EMBEDDED {
void ResolveControlFlow();
void PopulatePointerMaps();
void AllocateRegisters();
void ReuseSpillSlots();
bool CanEagerlyResolveControlFlow(HBasicBlock* block) const;
inline bool SafePointsAreInOrder() const;
@ -425,12 +460,12 @@ class LAllocator BASE_EMBEDDED {
void ActiveToInactive(LiveRange* range);
void InactiveToHandled(LiveRange* range);
void InactiveToActive(LiveRange* range);
void FreeSpillSlot(LiveRange* range);
LOperand* TryReuseSpillSlot(LiveRange* range);
SpillRange* AssignSpillRangeToLiveRange(LiveRange* range);
// Helper methods for allocating registers.
bool TryAllocateFreeReg(LiveRange* range);
void AllocateBlockedReg(LiveRange* range);
bool TryReuseSpillForPhi(LiveRange* range);
// Live range splitting helpers.
@ -530,6 +565,7 @@ class LAllocator BASE_EMBEDDED {
ZoneList<LiveRange*> active_live_ranges_;
ZoneList<LiveRange*> inactive_live_ranges_;
ZoneList<LiveRange*> reusable_slots_;
ZoneList<SpillRange*> spill_ranges_;
// Next virtual register number to be assigned to temporaries.
int next_virtual_register_;