// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/compiler/register-allocator.h"
#include "src/compiler/linkage.h"
#include "src/hydrogen.h"
#include "src/string-stream.h"
namespace v8 {
namespace internal {
namespace compiler {
static inline LifetimePosition Min(LifetimePosition a, LifetimePosition b) {
return a.Value() < b.Value() ? a : b;
}
static inline LifetimePosition Max(LifetimePosition a, LifetimePosition b) {
return a.Value() > b.Value() ? a : b;
}
UsePosition::UsePosition(LifetimePosition pos, InstructionOperand* operand,
InstructionOperand* hint)
: operand_(operand),
hint_(hint),
pos_(pos),
next_(NULL),
requires_reg_(false),
register_beneficial_(true) {
if (operand_ != NULL && operand_->IsUnallocated()) {
const UnallocatedOperand* unalloc = UnallocatedOperand::cast(operand_);
requires_reg_ = unalloc->HasRegisterPolicy();
register_beneficial_ = !unalloc->HasAnyPolicy();
}
DCHECK(pos_.IsValid());
}
bool UsePosition::HasHint() const {
return hint_ != NULL && !hint_->IsUnallocated();
}
bool UsePosition::RequiresRegister() const { return requires_reg_; }
bool UsePosition::RegisterIsBeneficial() const { return register_beneficial_; }
void UseInterval::SplitAt(LifetimePosition pos, Zone* zone) {
DCHECK(Contains(pos) && pos.Value() != start().Value());
UseInterval* after = new (zone) UseInterval(pos, end_);
after->next_ = next_;
next_ = after;
end_ = pos;
}
#ifdef DEBUG
void LiveRange::Verify() const {
UsePosition* cur = first_pos_;
while (cur != NULL) {
DCHECK(Start().Value() <= cur->pos().Value() &&
cur->pos().Value() <= End().Value());
cur = cur->next();
}
}
bool LiveRange::HasOverlap(UseInterval* target) const {
UseInterval* current_interval = first_interval_;
while (current_interval != NULL) {
// Intervals overlap if the start of one is contained in the other.
if (current_interval->Contains(target->start()) ||
target->Contains(current_interval->start())) {
return true;
}
current_interval = current_interval->next();
}
return false;
}
#endif
LiveRange::LiveRange(int id, Zone* zone)
: id_(id),
spilled_(false),
is_phi_(false),
is_non_loop_phi_(false),
kind_(UNALLOCATED_REGISTERS),
assigned_register_(kInvalidAssignment),
last_interval_(NULL),
first_interval_(NULL),
first_pos_(NULL),
parent_(NULL),
next_(NULL),
current_interval_(NULL),
last_processed_use_(NULL),
current_hint_operand_(NULL),
spill_operand_(new (zone) InstructionOperand()),
spill_start_index_(kMaxInt) {}
void LiveRange::set_assigned_register(int reg, Zone* zone) {
DCHECK(!HasRegisterAssigned() && !IsSpilled());
assigned_register_ = reg;
ConvertOperands(zone);
}
void LiveRange::MakeSpilled(Zone* zone) {
DCHECK(!IsSpilled());
DCHECK(TopLevel()->HasAllocatedSpillOperand());
spilled_ = true;
assigned_register_ = kInvalidAssignment;
ConvertOperands(zone);
}
bool LiveRange::HasAllocatedSpillOperand() const {
DCHECK(spill_operand_ != NULL);
return !spill_operand_->IsIgnored();
}
void LiveRange::SetSpillOperand(InstructionOperand* operand) {
DCHECK(!operand->IsUnallocated());
DCHECK(spill_operand_ != NULL);
DCHECK(spill_operand_->IsIgnored());
spill_operand_->ConvertTo(operand->kind(), operand->index());
}
UsePosition* LiveRange::NextUsePosition(LifetimePosition start) {
UsePosition* use_pos = last_processed_use_;
if (use_pos == NULL) use_pos = first_pos();
while (use_pos != NULL && use_pos->pos().Value() < start.Value()) {
use_pos = use_pos->next();
}
last_processed_use_ = use_pos;
return use_pos;
}
UsePosition* LiveRange::NextUsePositionRegisterIsBeneficial(
LifetimePosition start) {
UsePosition* pos = NextUsePosition(start);
while (pos != NULL && !pos->RegisterIsBeneficial()) {
pos = pos->next();
}
return pos;
}
UsePosition* LiveRange::PreviousUsePositionRegisterIsBeneficial(
LifetimePosition start) {
UsePosition* pos = first_pos();
UsePosition* prev = NULL;
while (pos != NULL && pos->pos().Value() < start.Value()) {
if (pos->RegisterIsBeneficial()) prev = pos;
pos = pos->next();
}
return prev;
}
UsePosition* LiveRange::NextRegisterPosition(LifetimePosition start) {
UsePosition* pos = NextUsePosition(start);
while (pos != NULL && !pos->RequiresRegister()) {
pos = pos->next();
}
return pos;
}
bool LiveRange::CanBeSpilled(LifetimePosition pos) {
// We cannot spill a live range that has a use requiring a register
// at the current or the immediate next position.
UsePosition* use_pos = NextRegisterPosition(pos);
if (use_pos == NULL) return true;
return use_pos->pos().Value() >
pos.NextInstruction().InstructionEnd().Value();
}
InstructionOperand* LiveRange::CreateAssignedOperand(Zone* zone) {
InstructionOperand* op = NULL;
if (HasRegisterAssigned()) {
DCHECK(!IsSpilled());
switch (Kind()) {
case GENERAL_REGISTERS:
op = RegisterOperand::Create(assigned_register(), zone);
break;
case DOUBLE_REGISTERS:
op = DoubleRegisterOperand::Create(assigned_register(), zone);
break;
default:
UNREACHABLE();
}
} else if (IsSpilled()) {
DCHECK(!HasRegisterAssigned());
op = TopLevel()->GetSpillOperand();
DCHECK(!op->IsUnallocated());
} else {
UnallocatedOperand* unalloc =
new (zone) UnallocatedOperand(UnallocatedOperand::NONE);
unalloc->set_virtual_register(id_);
op = unalloc;
}
return op;
}
UseInterval* LiveRange::FirstSearchIntervalForPosition(
LifetimePosition position) const {
if (current_interval_ == NULL) return first_interval_;
if (current_interval_->start().Value() > position.Value()) {
current_interval_ = NULL;
return first_interval_;
}
return current_interval_;
}
void LiveRange::AdvanceLastProcessedMarker(
UseInterval* to_start_of, LifetimePosition but_not_past) const {
if (to_start_of == NULL) return;
if (to_start_of->start().Value() > but_not_past.Value()) return;
LifetimePosition start = current_interval_ == NULL
? LifetimePosition::Invalid()
: current_interval_->start();
if (to_start_of->start().Value() > start.Value()) {
current_interval_ = to_start_of;
}
}
void LiveRange::SplitAt(LifetimePosition position, LiveRange* result,
Zone* zone) {
DCHECK(Start().Value() < position.Value());
DCHECK(result->IsEmpty());
// Find the last interval that ends before the position. If the
// position is contained in one of the intervals in the chain, we
// split that interval and use the first part.
UseInterval* current = FirstSearchIntervalForPosition(position);
// If the split position coincides with the beginning of a use interval
// we need to split use positons in a special way.
bool split_at_start = false;
if (current->start().Value() == position.Value()) {
// When splitting at start we need to locate the previous use interval.
current = first_interval_;
}
while (current != NULL) {
if (current->Contains(position)) {
current->SplitAt(position, zone);
break;
}
UseInterval* next = current->next();
if (next->start().Value() >= position.Value()) {
split_at_start = (next->start().Value() == position.Value());
break;
}
current = next;
}
// Partition original use intervals to the two live ranges.
UseInterval* before = current;
UseInterval* after = before->next();
result->last_interval_ =
(last_interval_ == before)
? after // Only interval in the range after split.
: last_interval_; // Last interval of the original range.
result->first_interval_ = after;
last_interval_ = before;
// Find the last use position before the split and the first use
// position after it.
UsePosition* use_after = first_pos_;
UsePosition* use_before = NULL;
if (split_at_start) {
// The split position coincides with the beginning of a use interval (the
// end of a lifetime hole). Use at this position should be attributed to
// the split child because split child owns use interval covering it.
while (use_after != NULL && use_after->pos().Value() < position.Value()) {
use_before = use_after;
use_after = use_after->next();
}
} else {
while (use_after != NULL && use_after->pos().Value() <= position.Value()) {
use_before = use_after;
use_after = use_after->next();
}
}
// Partition original use positions to the two live ranges.
if (use_before != NULL) {
use_before->next_ = NULL;
} else {
first_pos_ = NULL;
}
result->first_pos_ = use_after;
// Discard cached iteration state. It might be pointing
// to the use that no longer belongs to this live range.
last_processed_use_ = NULL;
current_interval_ = NULL;
// Link the new live range in the chain before any of the other
// ranges linked from the range before the split.
result->parent_ = (parent_ == NULL) ? this : parent_;
result->kind_ = result->parent_->kind_;
result->next_ = next_;
next_ = result;
#ifdef DEBUG
Verify();
result->Verify();
#endif
}
// This implements an ordering on live ranges so that they are ordered by their
// start positions. This is needed for the correctness of the register
// allocation algorithm. If two live ranges start at the same offset then there
// is a tie breaker based on where the value is first used. This part of the
// ordering is merely a heuristic.
bool LiveRange::ShouldBeAllocatedBefore(const LiveRange* other) const {
LifetimePosition start = Start();
LifetimePosition other_start = other->Start();
if (start.Value() == other_start.Value()) {
UsePosition* pos = first_pos();
if (pos == NULL) return false;
UsePosition* other_pos = other->first_pos();
if (other_pos == NULL) return true;
return pos->pos().Value() < other_pos->pos().Value();
}
return start.Value() < other_start.Value();
}
void LiveRange::ShortenTo(LifetimePosition start) {
RegisterAllocator::TraceAlloc("Shorten live range %d to [%d\n", id_,
start.Value());
DCHECK(first_interval_ != NULL);
DCHECK(first_interval_->start().Value() <= start.Value());
DCHECK(start.Value() < first_interval_->end().Value());
first_interval_->set_start(start);
}
void LiveRange::EnsureInterval(LifetimePosition start, LifetimePosition end,
Zone* zone) {
RegisterAllocator::TraceAlloc("Ensure live range %d in interval [%d %d[\n",
id_, start.Value(), end.Value());
LifetimePosition new_end = end;
while (first_interval_ != NULL &&
first_interval_->start().Value() <= end.Value()) {
if (first_interval_->end().Value() > end.Value()) {
new_end = first_interval_->end();
}
first_interval_ = first_interval_->next();
}
UseInterval* new_interval = new (zone) UseInterval(start, new_end);
new_interval->next_ = first_interval_;
first_interval_ = new_interval;
if (new_interval->next() == NULL) {
last_interval_ = new_interval;
}
}
void LiveRange::AddUseInterval(LifetimePosition start, LifetimePosition end,
Zone* zone) {
RegisterAllocator::TraceAlloc("Add to live range %d interval [%d %d[\n", id_,
start.Value(), end.Value());
if (first_interval_ == NULL) {
UseInterval* interval = new (zone) UseInterval(start, end);
first_interval_ = interval;
last_interval_ = interval;
} else {
if (end.Value() == first_interval_->start().Value()) {
first_interval_->set_start(start);
} else if (end.Value() < first_interval_->start().Value()) {
UseInterval* interval = new (zone) UseInterval(start, end);
interval->set_next(first_interval_);
first_interval_ = interval;
} else {
// Order of instruction's processing (see ProcessInstructions) guarantees
// that each new use interval either precedes or intersects with
// last added interval.
DCHECK(start.Value() < first_interval_->end().Value());
first_interval_->start_ = Min(start, first_interval_->start_);
first_interval_->end_ = Max(end, first_interval_->end_);
}
}
}
void LiveRange::AddUsePosition(LifetimePosition pos,
InstructionOperand* operand,
InstructionOperand* hint, Zone* zone) {
RegisterAllocator::TraceAlloc("Add to live range %d use position %d\n", id_,
pos.Value());
UsePosition* use_pos = new (zone) UsePosition(pos, operand, hint);
UsePosition* prev_hint = NULL;
UsePosition* prev = NULL;
UsePosition* current = first_pos_;
while (current != NULL && current->pos().Value() < pos.Value()) {
prev_hint = current->HasHint() ? current : prev_hint;
prev = current;
current = current->next();
}
if (prev == NULL) {
use_pos->set_next(first_pos_);
first_pos_ = use_pos;
} else {
use_pos->next_ = prev->next_;
prev->next_ = use_pos;
}
if (prev_hint == NULL && use_pos->HasHint()) {
current_hint_operand_ = hint;
}
}
void LiveRange::ConvertOperands(Zone* zone) {
InstructionOperand* op = CreateAssignedOperand(zone);
UsePosition* use_pos = first_pos();
while (use_pos != NULL) {
DCHECK(Start().Value() <= use_pos->pos().Value() &&
use_pos->pos().Value() <= End().Value());
if (use_pos->HasOperand()) {
DCHECK(op->IsRegister() || op->IsDoubleRegister() ||
!use_pos->RequiresRegister());
use_pos->operand()->ConvertTo(op->kind(), op->index());
}
use_pos = use_pos->next();
}
}
bool LiveRange::CanCover(LifetimePosition position) const {
if (IsEmpty()) return false;
return Start().Value() <= position.Value() &&
position.Value() < End().Value();
}
bool LiveRange::Covers(LifetimePosition position) {
if (!CanCover(position)) return false;
UseInterval* start_search = FirstSearchIntervalForPosition(position);
for (UseInterval* interval = start_search; interval != NULL;
interval = interval->next()) {
DCHECK(interval->next() == NULL ||
interval->next()->start().Value() >= interval->start().Value());
AdvanceLastProcessedMarker(interval, position);
if (interval->Contains(position)) return true;
if (interval->start().Value() > position.Value()) return false;
}
return false;
}
LifetimePosition LiveRange::FirstIntersection(LiveRange* other) {
UseInterval* b = other->first_interval();
if (b == NULL) return LifetimePosition::Invalid();
LifetimePosition advance_last_processed_up_to = b->start();
UseInterval* a = FirstSearchIntervalForPosition(b->start());
while (a != NULL && b != NULL) {
if (a->start().Value() > other->End().Value()) break;
if (b->start().Value() > End().Value()) break;
LifetimePosition cur_intersection = a->Intersect(b);
if (cur_intersection.IsValid()) {
return cur_intersection;
}
if (a->start().Value() < b->start().Value()) {
a = a->next();
if (a == NULL || a->start().Value() > other->End().Value()) break;
AdvanceLastProcessedMarker(a, advance_last_processed_up_to);
} else {
b = b->next();
}
}
return LifetimePosition::Invalid();
}
RegisterAllocator::RegisterAllocator(InstructionSequence* code)
: zone_(code->isolate()),
code_(code),
live_in_sets_(code->BasicBlockCount(), zone()),
live_ranges_(code->VirtualRegisterCount() * 2, zone()),
fixed_live_ranges_(NULL),
fixed_double_live_ranges_(NULL),
unhandled_live_ranges_(code->VirtualRegisterCount() * 2, zone()),
active_live_ranges_(8, zone()),
inactive_live_ranges_(8, zone()),
reusable_slots_(8, zone()),
mode_(UNALLOCATED_REGISTERS),
num_registers_(-1),
allocation_ok_(true) {}
void RegisterAllocator::InitializeLivenessAnalysis() {
// Initialize the live_in sets for each block to NULL.
int block_count = code()->BasicBlockCount();
live_in_sets_.Initialize(block_count, zone());
live_in_sets_.AddBlock(NULL, block_count, zone());
}
BitVector* RegisterAllocator::ComputeLiveOut(BasicBlock* block) {
// Compute live out for the given block, except not including backward
// successor edges.
BitVector* live_out =
new (zone()) BitVector(code()->VirtualRegisterCount(), zone());
// Process all successor blocks.
BasicBlock::Successors successors = block->successors();
for (BasicBlock::Successors::iterator i = successors.begin();
i != successors.end(); ++i) {
// Add values live on entry to the successor. Note the successor's
// live_in will not be computed yet for backwards edges.
BasicBlock* successor = *i;
BitVector* live_in = live_in_sets_[successor->rpo_number_];
if (live_in != NULL) live_out->Union(*live_in);
// All phi input operands corresponding to this successor edge are live
// out from this block.
int index = successor->PredecessorIndexOf(block);
DCHECK(index >= 0);
DCHECK(index < static_cast<int>(successor->PredecessorCount()));
for (BasicBlock::const_iterator j = successor->begin();
j != successor->end(); ++j) {
Node* phi = *j;
if (phi->opcode() != IrOpcode::kPhi) continue;
Node* input = phi->InputAt(index);
live_out->Add(input->id());
}
}
return live_out;
}
void RegisterAllocator::AddInitialIntervals(BasicBlock* block,
BitVector* live_out) {
// Add an interval that includes the entire block to the live range for
// each live_out value.
LifetimePosition start =
LifetimePosition::FromInstructionIndex(block->first_instruction_index());
LifetimePosition end = LifetimePosition::FromInstructionIndex(
block->last_instruction_index()).NextInstruction();
BitVector::Iterator iterator(live_out);
while (!iterator.Done()) {
int operand_index = iterator.Current();
LiveRange* range = LiveRangeFor(operand_index);
range->AddUseInterval(start, end, zone());
iterator.Advance();
}
}
int RegisterAllocator::FixedDoubleLiveRangeID(int index) {
return -index - 1 - Register::kMaxNumAllocatableRegisters;
}
InstructionOperand* RegisterAllocator::AllocateFixed(
UnallocatedOperand* operand, int pos, bool is_tagged) {
TraceAlloc("Allocating fixed reg for op %d\n", operand->virtual_register());
DCHECK(operand->HasFixedPolicy());
if (operand->HasFixedSlotPolicy()) {
operand->ConvertTo(InstructionOperand::STACK_SLOT,
operand->fixed_slot_index());
} else if (operand->HasFixedRegisterPolicy()) {
int reg_index = operand->fixed_register_index();
operand->ConvertTo(InstructionOperand::REGISTER, reg_index);
} else if (operand->HasFixedDoubleRegisterPolicy()) {
int reg_index = operand->fixed_register_index();
operand->ConvertTo(InstructionOperand::DOUBLE_REGISTER, reg_index);
} else {
UNREACHABLE();
}
if (is_tagged) {
TraceAlloc("Fixed reg is tagged at %d\n", pos);
Instruction* instr = InstructionAt(pos);
if (instr->HasPointerMap()) {
instr->pointer_map()->RecordPointer(operand, code_zone());
}
}
return operand;
}
LiveRange* RegisterAllocator::FixedLiveRangeFor(int index) {
DCHECK(index < Register::kMaxNumAllocatableRegisters);
LiveRange* result = fixed_live_ranges_[index];
if (result == NULL) {
// TODO(titzer): add a utility method to allocate a new LiveRange:
// The LiveRange object itself can go in this zone, but the
// InstructionOperand needs
// to go in the code zone, since it may survive register allocation.
result = new (zone()) LiveRange(FixedLiveRangeID(index), code_zone());
DCHECK(result->IsFixed());
result->kind_ = GENERAL_REGISTERS;
SetLiveRangeAssignedRegister(result, index);
fixed_live_ranges_[index] = result;
}
return result;
}
LiveRange* RegisterAllocator::FixedDoubleLiveRangeFor(int index) {
DCHECK(index < DoubleRegister::NumAllocatableRegisters());
LiveRange* result = fixed_double_live_ranges_[index];
if (result == NULL) {
result = new (zone()) LiveRange(FixedDoubleLiveRangeID(index), code_zone());
DCHECK(result->IsFixed());
result->kind_ = DOUBLE_REGISTERS;
SetLiveRangeAssignedRegister(result, index);
fixed_double_live_ranges_[index] = result;
}
return result;
}
LiveRange* RegisterAllocator::LiveRangeFor(int index) {
if (index >= live_ranges_.length()) {
live_ranges_.AddBlock(NULL, index - live_ranges_.length() + 1, zone());
}
LiveRange* result = live_ranges_[index];
if (result == NULL) {
result = new (zone()) LiveRange(index, code_zone());
live_ranges_[index] = result;
}
return result;
}
GapInstruction* RegisterAllocator::GetLastGap(BasicBlock* block) {
int last_instruction = block->last_instruction_index();
return code()->GapAt(last_instruction - 1);
}
LiveRange* RegisterAllocator::LiveRangeFor(InstructionOperand* operand) {
if (operand->IsUnallocated()) {
return LiveRangeFor(UnallocatedOperand::cast(operand)->virtual_register());
} else if (operand->IsRegister()) {
return FixedLiveRangeFor(operand->index());
} else if (operand->IsDoubleRegister()) {
return FixedDoubleLiveRangeFor(operand->index());
} else {
return NULL;
}
}
void RegisterAllocator::Define(LifetimePosition position,
InstructionOperand* operand,
InstructionOperand* hint) {
LiveRange* range = LiveRangeFor(operand);
if (range == NULL) return;
if (range->IsEmpty() || range->Start().Value() > position.Value()) {
// Can happen if there is a definition without use.
range->AddUseInterval(position, position.NextInstruction(), zone());
range->AddUsePosition(position.NextInstruction(), NULL, NULL, zone());
} else {
range->ShortenTo(position);
}
if (operand->IsUnallocated()) {
UnallocatedOperand* unalloc_operand = UnallocatedOperand::cast(operand);
range->AddUsePosition(position, unalloc_operand, hint, zone());
}
}
void RegisterAllocator::Use(LifetimePosition block_start,
LifetimePosition position,
InstructionOperand* operand,
InstructionOperand* hint) {
LiveRange* range = LiveRangeFor(operand);
if (range == NULL) return;
if (operand->IsUnallocated()) {
UnallocatedOperand* unalloc_operand = UnallocatedOperand::cast(operand);
range->AddUsePosition(position, unalloc_operand, hint, zone());
}
range->AddUseInterval(block_start, position, zone());
}
void RegisterAllocator::AddConstraintsGapMove(int index,
InstructionOperand* from,
InstructionOperand* to) {
GapInstruction* gap = code()->GapAt(index);
ParallelMove* move =
gap->GetOrCreateParallelMove(GapInstruction::START, code_zone());
if (from->IsUnallocated()) {
const ZoneList<MoveOperands>* move_operands = move->move_operands();
for (int i = 0; i < move_operands->length(); ++i) {
MoveOperands cur = move_operands->at(i);
InstructionOperand* cur_to = cur.destination();
if (cur_to->IsUnallocated()) {
if (UnallocatedOperand::cast(cur_to)->virtual_register() ==
UnallocatedOperand::cast(from)->virtual_register()) {
move->AddMove(cur.source(), to, code_zone());
return;
}
}
}
}
move->AddMove(from, to, code_zone());
}
void RegisterAllocator::MeetRegisterConstraints(BasicBlock* block) {
int start = block->first_instruction_index();
int end = block->last_instruction_index();
DCHECK_NE(-1, start);
for (int i = start; i <= end; ++i) {
if (code()->IsGapAt(i)) {
Instruction* instr = NULL;
Instruction* prev_instr = NULL;
if (i < end) instr = InstructionAt(i + 1);
if (i > start) prev_instr = InstructionAt(i - 1);
MeetConstraintsBetween(prev_instr, instr, i);
if (!AllocationOk()) return;
}
}
// Meet register constraints for the instruction in the end.
if (!code()->IsGapAt(end)) {
MeetRegisterConstraintsForLastInstructionInBlock(block);
}
}
void RegisterAllocator::MeetRegisterConstraintsForLastInstructionInBlock(
BasicBlock* block) {
int end = block->last_instruction_index();
Instruction* last_instruction = InstructionAt(end);
for (size_t i = 0; i < last_instruction->OutputCount(); i++) {
InstructionOperand* output_operand = last_instruction->OutputAt(i);
DCHECK(!output_operand->IsConstant());
UnallocatedOperand* output = UnallocatedOperand::cast(output_operand);
int output_vreg = output->virtual_register();
LiveRange* range = LiveRangeFor(output_vreg);
bool assigned = false;
if (output->HasFixedPolicy()) {
AllocateFixed(output, -1, false);
// This value is produced on the stack, we never need to spill it.
if (output->IsStackSlot()) {
range->SetSpillOperand(output);
range->SetSpillStartIndex(end);
assigned = true;
}
BasicBlock::Successors successors = block->successors();
for (BasicBlock::Successors::iterator succ = successors.begin();
succ != successors.end(); ++succ) {
DCHECK((*succ)->PredecessorCount() == 1);
int gap_index = (*succ)->first_instruction_index() + 1;
DCHECK(code()->IsGapAt(gap_index));
// Create an unconstrained operand for the same virtual register
// and insert a gap move from the fixed output to the operand.
UnallocatedOperand* output_copy =
new (code_zone()) UnallocatedOperand(UnallocatedOperand::ANY);
output_copy->set_virtual_register(output_vreg);
code()->AddGapMove(gap_index, output, output_copy);
}
}
if (!assigned) {
BasicBlock::Successors successors = block->successors();
for (BasicBlock::Successors::iterator succ = successors.begin();
succ != successors.end(); ++succ) {
DCHECK((*succ)->PredecessorCount() == 1);
int gap_index = (*succ)->first_instruction_index() + 1;
range->SetSpillStartIndex(gap_index);
// This move to spill operand is not a real use. Liveness analysis
// and splitting of live ranges do not account for it.
// Thus it should be inserted to a lifetime position corresponding to
// the instruction end.
GapInstruction* gap = code()->GapAt(gap_index);
ParallelMove* move =
gap->GetOrCreateParallelMove(GapInstruction::BEFORE, code_zone());
move->AddMove(output, range->GetSpillOperand(), code_zone());
}
}
}
}
void RegisterAllocator::MeetConstraintsBetween(Instruction* first,
Instruction* second,
int gap_index) {
if (first != NULL) {
// Handle fixed temporaries.
for (size_t i = 0; i < first->TempCount(); i++) {
UnallocatedOperand* temp = UnallocatedOperand::cast(first->TempAt(i));
if (temp->HasFixedPolicy()) {
AllocateFixed(temp, gap_index - 1, false);
}
}
// Handle constant/fixed output operands.
for (size_t i = 0; i < first->OutputCount(); i++) {
InstructionOperand* output = first->OutputAt(i);
if (output->IsConstant()) {
int output_vreg = output->index();
LiveRange* range = LiveRangeFor(output_vreg);
range->SetSpillStartIndex(gap_index - 1);
range->SetSpillOperand(output);
} else {
UnallocatedOperand* first_output = UnallocatedOperand::cast(output);
LiveRange* range = LiveRangeFor(first_output->virtual_register());
bool assigned = false;
if (first_output->HasFixedPolicy()) {
UnallocatedOperand* output_copy =
first_output->CopyUnconstrained(code_zone());
bool is_tagged = HasTaggedValue(first_output->virtual_register());
AllocateFixed(first_output, gap_index, is_tagged);
// This value is produced on the stack, we never need to spill it.
if (first_output->IsStackSlot()) {
range->SetSpillOperand(first_output);
range->SetSpillStartIndex(gap_index - 1);
assigned = true;
}
code()->AddGapMove(gap_index, first_output, output_copy);
}
// Make sure we add a gap move for spilling (if we have not done
// so already).
if (!assigned) {
range->SetSpillStartIndex(gap_index);
// This move to spill operand is not a real use. Liveness analysis
// and splitting of live ranges do not account for it.
// Thus it should be inserted to a lifetime position corresponding to
// the instruction end.
GapInstruction* gap = code()->GapAt(gap_index);
ParallelMove* move =
gap->GetOrCreateParallelMove(GapInstruction::BEFORE, code_zone());
move->AddMove(first_output, range->GetSpillOperand(), code_zone());
}
}
}
}
if (second != NULL) {
// Handle fixed input operands of second instruction.
for (size_t i = 0; i < second->InputCount(); i++) {
InstructionOperand* input = second->InputAt(i);
if (input->IsImmediate()) continue; // Ignore immediates.
UnallocatedOperand* cur_input = UnallocatedOperand::cast(input);
if (cur_input->HasFixedPolicy()) {
UnallocatedOperand* input_copy =
cur_input->CopyUnconstrained(code_zone());
bool is_tagged = HasTaggedValue(cur_input->virtual_register());
AllocateFixed(cur_input, gap_index + 1, is_tagged);
AddConstraintsGapMove(gap_index, input_copy, cur_input);
}
}
// Handle "output same as input" for second instruction.
for (size_t i = 0; i < second->OutputCount(); i++) {
InstructionOperand* output = second->OutputAt(i);
if (!output->IsUnallocated()) continue;
UnallocatedOperand* second_output = UnallocatedOperand::cast(output);
if (second_output->HasSameAsInputPolicy()) {
DCHECK(i == 0); // Only valid for first output.
UnallocatedOperand* cur_input =
UnallocatedOperand::cast(second->InputAt(0));
int output_vreg = second_output->virtual_register();
int input_vreg = cur_input->virtual_register();
UnallocatedOperand* input_copy =
cur_input->CopyUnconstrained(code_zone());
cur_input->set_virtual_register(second_output->virtual_register());
AddConstraintsGapMove(gap_index, input_copy, cur_input);
if (HasTaggedValue(input_vreg) && !HasTaggedValue(output_vreg)) {
int index = gap_index + 1;
Instruction* instr = InstructionAt(index);
if (instr->HasPointerMap()) {
instr->pointer_map()->RecordPointer(input_copy, code_zone());
}
} else if (!HasTaggedValue(input_vreg) && HasTaggedValue(output_vreg)) {
// The input is assumed to immediately have a tagged representation,
// before the pointer map can be used. I.e. the pointer map at the
// instruction will include the output operand (whose value at the
// beginning of the instruction is equal to the input operand). If
// this is not desired, then the pointer map at this instruction needs
// to be adjusted manually.
}
}
}
}
}
bool RegisterAllocator::IsOutputRegisterOf(Instruction* instr, int index) {
for (size_t i = 0; i < instr->OutputCount(); i++) {
InstructionOperand* output = instr->OutputAt(i);
if (output->IsRegister() && output->index() == index) return true;
}
return false;
}
bool RegisterAllocator::IsOutputDoubleRegisterOf(Instruction* instr,
int index) {
for (size_t i = 0; i < instr->OutputCount(); i++) {
InstructionOperand* output = instr->OutputAt(i);
if (output->IsDoubleRegister() && output->index() == index) return true;
}
return false;
}
void RegisterAllocator::ProcessInstructions(BasicBlock* block,
BitVector* live) {
int block_start = block->first_instruction_index();
LifetimePosition block_start_position =
LifetimePosition::FromInstructionIndex(block_start);
for (int index = block->last_instruction_index(); index >= block_start;
index--) {
LifetimePosition curr_position =
LifetimePosition::FromInstructionIndex(index);
Instruction* instr = InstructionAt(index);
DCHECK(instr != NULL);
if (instr->IsGapMoves()) {
// Process the moves of the gap instruction, making their sources live.
GapInstruction* gap = code()->GapAt(index);
// TODO(titzer): no need to create the parallel move if it doesn't exist.
ParallelMove* move =
gap->GetOrCreateParallelMove(GapInstruction::START, code_zone());
const ZoneList<MoveOperands>* move_operands = move->move_operands();
for (int i = 0; i < move_operands->length(); ++i) {
MoveOperands* cur = &move_operands->at(i);
if (cur->IsIgnored()) continue;
InstructionOperand* from = cur->source();
InstructionOperand* to = cur->destination();
InstructionOperand* hint = to;
if (to->IsUnallocated()) {
int to_vreg = UnallocatedOperand::cast(to)->virtual_register();
LiveRange* to_range = LiveRangeFor(to_vreg);
if (to_range->is_phi()) {
if (to_range->is_non_loop_phi()) {
hint = to_range->current_hint_operand();
}
} else {
if (live->Contains(to_vreg)) {
Define(curr_position, to, from);
live->Remove(to_vreg);
} else {
cur->Eliminate();
continue;
}
}
} else {
Define(curr_position, to, from);
}
Use(block_start_position, curr_position, from, hint);
if (from->IsUnallocated()) {
live->Add(UnallocatedOperand::cast(from)->virtual_register());
}
}
} else {
// Process output, inputs, and temps of this non-gap instruction.
for (size_t i = 0; i < instr->OutputCount(); i++) {
InstructionOperand* output = instr->OutputAt(i);
if (output->IsUnallocated()) {
int out_vreg = UnallocatedOperand::cast(output)->virtual_register();
live->Remove(out_vreg);
} else if (output->IsConstant()) {
int out_vreg = output->index();
live->Remove(out_vreg);
}
Define(curr_position, output, NULL);
}
if (instr->ClobbersRegisters()) {
for (int i = 0; i < Register::kMaxNumAllocatableRegisters; ++i) {
if (!IsOutputRegisterOf(instr, i)) {
LiveRange* range = FixedLiveRangeFor(i);
range->AddUseInterval(curr_position, curr_position.InstructionEnd(),
zone());
}
}
}
if (instr->ClobbersDoubleRegisters()) {
for (int i = 0; i < DoubleRegister::NumAllocatableRegisters(); ++i) {
if (!IsOutputDoubleRegisterOf(instr, i)) {
LiveRange* range = FixedDoubleLiveRangeFor(i);
range->AddUseInterval(curr_position, curr_position.InstructionEnd(),
zone());
}
}
}
for (size_t i = 0; i < instr->InputCount(); i++) {
InstructionOperand* input = instr->InputAt(i);
if (input->IsImmediate()) continue; // Ignore immediates.
LifetimePosition use_pos;
if (input->IsUnallocated() &&
UnallocatedOperand::cast(input)->IsUsedAtStart()) {
use_pos = curr_position;
} else {
use_pos = curr_position.InstructionEnd();
}
Use(block_start_position, use_pos, input, NULL);
if (input->IsUnallocated()) {
live->Add(UnallocatedOperand::cast(input)->virtual_register());
}
}
for (size_t i = 0; i < instr->TempCount(); i++) {
InstructionOperand* temp = instr->TempAt(i);
if (instr->ClobbersTemps()) {
if (temp->IsRegister()) continue;
if (temp->IsUnallocated()) {
UnallocatedOperand* temp_unalloc = UnallocatedOperand::cast(temp);
if (temp_unalloc->HasFixedPolicy()) {
continue;
}
}
}
Use(block_start_position, curr_position.InstructionEnd(), temp, NULL);
Define(curr_position, temp, NULL);
}
}
}
}
void RegisterAllocator::ResolvePhis(BasicBlock* block) {
for (BasicBlock::const_iterator i = block->begin(); i != block->end(); ++i) {
Node* phi = *i;
if (phi->opcode() != IrOpcode::kPhi) continue;
UnallocatedOperand* phi_operand =
new (code_zone()) UnallocatedOperand(UnallocatedOperand::NONE);
phi_operand->set_virtual_register(phi->id());
int j = 0;
Node::Inputs inputs = phi->inputs();
for (Node::Inputs::iterator iter(inputs.begin()); iter != inputs.end();
++iter, ++j) {
Node* op = *iter;
// TODO(mstarzinger): Use a ValueInputIterator instead.
if (j >= block->PredecessorCount()) continue;
UnallocatedOperand* operand =
new (code_zone()) UnallocatedOperand(UnallocatedOperand::ANY);
operand->set_virtual_register(op->id());
BasicBlock* cur_block = block->PredecessorAt(j);
// The gap move must be added without any special processing as in
// the AddConstraintsGapMove.
code()->AddGapMove(cur_block->last_instruction_index() - 1, operand,
phi_operand);
Instruction* branch = InstructionAt(cur_block->last_instruction_index());
DCHECK(!branch->HasPointerMap());
USE(branch);
}
LiveRange* live_range = LiveRangeFor(phi->id());
BlockStartInstruction* block_start = code()->GetBlockStart(block);
block_start->GetOrCreateParallelMove(GapInstruction::START, code_zone())
->AddMove(phi_operand, live_range->GetSpillOperand(), code_zone());
live_range->SetSpillStartIndex(block->first_instruction_index());
// We use the phi-ness of some nodes in some later heuristics.
live_range->set_is_phi(true);
if (!block->IsLoopHeader()) {
live_range->set_is_non_loop_phi(true);
}
}
}
bool RegisterAllocator::Allocate() {
assigned_registers_ = new (code_zone())
BitVector(Register::NumAllocatableRegisters(), code_zone());
assigned_double_registers_ = new (code_zone())
BitVector(DoubleRegister::NumAllocatableRegisters(), code_zone());
MeetRegisterConstraints();
if (!AllocationOk()) return false;
ResolvePhis();
BuildLiveRanges();
AllocateGeneralRegisters();
if (!AllocationOk()) return false;
AllocateDoubleRegisters();
if (!AllocationOk()) return false;
PopulatePointerMaps();
ConnectRanges();
ResolveControlFlow();
code()->frame()->SetAllocatedRegisters(assigned_registers_);
code()->frame()->SetAllocatedDoubleRegisters(assigned_double_registers_);
return true;
}
void RegisterAllocator::MeetRegisterConstraints() {
RegisterAllocatorPhase phase("L_Register constraints", this);
for (int i = 0; i < code()->BasicBlockCount(); ++i) {
MeetRegisterConstraints(code()->BlockAt(i));
if (!AllocationOk()) return;
}
}
void RegisterAllocator::ResolvePhis() {
RegisterAllocatorPhase phase("L_Resolve phis", this);
// Process the blocks in reverse order.
for (int i = code()->BasicBlockCount() - 1; i >= 0; --i) {
ResolvePhis(code()->BlockAt(i));
}
}
void RegisterAllocator::ResolveControlFlow(LiveRange* range, BasicBlock* block,
BasicBlock* pred) {
LifetimePosition pred_end =
LifetimePosition::FromInstructionIndex(pred->last_instruction_index());
LifetimePosition cur_start =
LifetimePosition::FromInstructionIndex(block->first_instruction_index());
LiveRange* pred_cover = NULL;
LiveRange* cur_cover = NULL;
LiveRange* cur_range = range;
while (cur_range != NULL && (cur_cover == NULL || pred_cover == NULL)) {
if (cur_range->CanCover(cur_start)) {
DCHECK(cur_cover == NULL);
cur_cover = cur_range;
}
if (cur_range->CanCover(pred_end)) {
DCHECK(pred_cover == NULL);
pred_cover = cur_range;
}
cur_range = cur_range->next();
}
if (cur_cover->IsSpilled()) return;
DCHECK(pred_cover != NULL && cur_cover != NULL);
if (pred_cover != cur_cover) {
InstructionOperand* pred_op =
pred_cover->CreateAssignedOperand(code_zone());
InstructionOperand* cur_op = cur_cover->CreateAssignedOperand(code_zone());
if (!pred_op->Equals(cur_op)) {
GapInstruction* gap = NULL;
if (block->PredecessorCount() == 1) {
gap = code()->GapAt(block->first_instruction_index());
} else {
DCHECK(pred->SuccessorCount() == 1);
gap = GetLastGap(pred);
Instruction* branch = InstructionAt(pred->last_instruction_index());
DCHECK(!branch->HasPointerMap());
USE(branch);
}
gap->GetOrCreateParallelMove(GapInstruction::START, code_zone())
->AddMove(pred_op, cur_op, code_zone());
}
}
}
ParallelMove* RegisterAllocator::GetConnectingParallelMove(
LifetimePosition pos) {
int index = pos.InstructionIndex();
if (code()->IsGapAt(index)) {
GapInstruction* gap = code()->GapAt(index);
return gap->GetOrCreateParallelMove(
pos.IsInstructionStart() ? GapInstruction::START : GapInstruction::END,
code_zone());
}
int gap_pos = pos.IsInstructionStart() ? (index - 1) : (index + 1);
return code()->GapAt(gap_pos)->GetOrCreateParallelMove(
(gap_pos < index) ? GapInstruction::AFTER : GapInstruction::BEFORE,
code_zone());
}
BasicBlock* RegisterAllocator::GetBlock(LifetimePosition pos) {
return code()->GetBasicBlock(pos.InstructionIndex());
}
void RegisterAllocator::ConnectRanges() {
RegisterAllocatorPhase phase("L_Connect ranges", this);
for (int i = 0; i < live_ranges()->length(); ++i) {
LiveRange* first_range = live_ranges()->at(i);
if (first_range == NULL || first_range->parent() != NULL) continue;
LiveRange* second_range = first_range->next();
while (second_range != NULL) {
LifetimePosition pos = second_range->Start();
if (!second_range->IsSpilled()) {
// Add gap move if the two live ranges touch and there is no block
// boundary.
if (first_range->End().Value() == pos.Value()) {
bool should_insert = true;
if (IsBlockBoundary(pos)) {
should_insert = CanEagerlyResolveControlFlow(GetBlock(pos));
}
if (should_insert) {
ParallelMove* move = GetConnectingParallelMove(pos);
InstructionOperand* prev_operand =
first_range->CreateAssignedOperand(code_zone());
InstructionOperand* cur_operand =
second_range->CreateAssignedOperand(code_zone());
move->AddMove(prev_operand, cur_operand, code_zone());
}
}
}
first_range = second_range;
second_range = second_range->next();
}
}
}
bool RegisterAllocator::CanEagerlyResolveControlFlow(BasicBlock* block) const {
if (block->PredecessorCount() != 1) return false;
return block->PredecessorAt(0)->rpo_number_ == block->rpo_number_ - 1;
}
void RegisterAllocator::ResolveControlFlow() {
RegisterAllocatorPhase phase("L_Resolve control flow", this);
for (int block_id = 1; block_id < code()->BasicBlockCount(); ++block_id) {
BasicBlock* block = code()->BlockAt(block_id);
if (CanEagerlyResolveControlFlow(block)) continue;
BitVector* live = live_in_sets_[block->rpo_number_];
BitVector::Iterator iterator(live);
while (!iterator.Done()) {
int operand_index = iterator.Current();
BasicBlock::Predecessors predecessors = block->predecessors();
for (BasicBlock::Predecessors::iterator i = predecessors.begin();
i != predecessors.end(); ++i) {
BasicBlock* cur = *i;
LiveRange* cur_range = LiveRangeFor(operand_index);
ResolveControlFlow(cur_range, block, cur);
}
iterator.Advance();
}
}
}
void RegisterAllocator::BuildLiveRanges() {
RegisterAllocatorPhase phase("L_Build live ranges", this);
InitializeLivenessAnalysis();
// Process the blocks in reverse order.
for (int block_id = code()->BasicBlockCount() - 1; block_id >= 0;
--block_id) {
BasicBlock* block = code()->BlockAt(block_id);
BitVector* live = ComputeLiveOut(block);
// Initially consider all live_out values live for the entire block. We
// will shorten these intervals if necessary.
AddInitialIntervals(block, live);
// Process the instructions in reverse order, generating and killing
// live values.
ProcessInstructions(block, live);
// All phi output operands are killed by this block.
for (BasicBlock::const_iterator i = block->begin(); i != block->end();
++i) {
Node* phi = *i;
if (phi->opcode() != IrOpcode::kPhi) continue;
// The live range interval already ends at the first instruction of the
// block.
live->Remove(phi->id());
InstructionOperand* hint = NULL;
InstructionOperand* phi_operand = NULL;
GapInstruction* gap = GetLastGap(block->PredecessorAt(0));
// TODO(titzer): no need to create the parallel move if it doesn't exit.
ParallelMove* move =
gap->GetOrCreateParallelMove(GapInstruction::START, code_zone());
for (int j = 0; j < move->move_operands()->length(); ++j) {
InstructionOperand* to = move->move_operands()->at(j).destination();
if (to->IsUnallocated() &&
UnallocatedOperand::cast(to)->virtual_register() == phi->id()) {
hint = move->move_operands()->at(j).source();
phi_operand = to;
break;
}
}
DCHECK(hint != NULL);
LifetimePosition block_start = LifetimePosition::FromInstructionIndex(
block->first_instruction_index());
Define(block_start, phi_operand, hint);
}
// Now live is live_in for this block except not including values live
// out on backward successor edges.
live_in_sets_[block_id] = live;
if (block->IsLoopHeader()) {
// Add a live range stretching from the first loop instruction to the last
// for each value live on entry to the header.
BitVector::Iterator iterator(live);
LifetimePosition start = LifetimePosition::FromInstructionIndex(
block->first_instruction_index());
int end_index =
code()->BlockAt(block->loop_end_)->last_instruction_index();
LifetimePosition end =
LifetimePosition::FromInstructionIndex(end_index).NextInstruction();
while (!iterator.Done()) {
int operand_index = iterator.Current();
LiveRange* range = LiveRangeFor(operand_index);
range->EnsureInterval(start, end, zone());
iterator.Advance();
}
// Insert all values into the live in sets of all blocks in the loop.
for (int i = block->rpo_number_ + 1; i < block->loop_end_; ++i) {
live_in_sets_[i]->Union(*live);
}
}
#ifdef DEBUG
if (block_id == 0) {
BitVector::Iterator iterator(live);
bool found = false;
while (!iterator.Done()) {
found = true;
int operand_index = iterator.Current();
PrintF("Register allocator error: live v%d reached first block.\n",
operand_index);
LiveRange* range = LiveRangeFor(operand_index);
PrintF(" (first use is at %d)\n", range->first_pos()->pos().Value());
CompilationInfo* info = code()->linkage()->info();
if (info->IsStub()) {
if (info->code_stub() == NULL) {
PrintF("\n");
} else {
CodeStub::Major major_key = info->code_stub()->MajorKey();
PrintF(" (function: %s)\n", CodeStub::MajorName(major_key, false));
}
} else {
DCHECK(info->IsOptimizing());
AllowHandleDereference allow_deref;
PrintF(" (function: %s)\n",
info->function()->debug_name()->ToCString().get());
}
iterator.Advance();
}
DCHECK(!found);
}
#endif
}
for (int i = 0; i < live_ranges_.length(); ++i) {
if (live_ranges_[i] != NULL) {
live_ranges_[i]->kind_ = RequiredRegisterKind(live_ranges_[i]->id());
// TODO(bmeurer): This is a horrible hack to make sure that for constant
// live ranges, every use requires the constant to be in a register.
// Without this hack, all uses with "any" policy would get the constant
// operand assigned.
LiveRange* range = live_ranges_[i];
if (range->HasAllocatedSpillOperand() &&
range->GetSpillOperand()->IsConstant()) {
for (UsePosition* pos = range->first_pos(); pos != NULL;
pos = pos->next_) {
pos->register_beneficial_ = true;
pos->requires_reg_ = true;
}
}
}
}
}
bool RegisterAllocator::SafePointsAreInOrder() const {
int safe_point = 0;
const PointerMapDeque* pointer_maps = code()->pointer_maps();
for (PointerMapDeque::const_iterator it = pointer_maps->begin();
it != pointer_maps->end(); ++it) {
PointerMap* map = *it;
if (safe_point > map->instruction_position()) return false;
safe_point = map->instruction_position();
}
return true;
}
void RegisterAllocator::PopulatePointerMaps() {
RegisterAllocatorPhase phase("L_Populate pointer maps", this);
DCHECK(SafePointsAreInOrder());
// Iterate over all safe point positions and record a pointer
// for all spilled live ranges at this point.
int last_range_start = 0;
const PointerMapDeque* pointer_maps = code()->pointer_maps();
PointerMapDeque::const_iterator first_it = pointer_maps->begin();
for (int range_idx = 0; range_idx < live_ranges()->length(); ++range_idx) {
LiveRange* range = live_ranges()->at(range_idx);
if (range == NULL) continue;
// Iterate over the first parts of multi-part live ranges.
if (range->parent() != NULL) continue;
// Skip non-reference values.
if (!HasTaggedValue(range->id())) continue;
// Skip empty live ranges.
if (range->IsEmpty()) continue;
// Find the extent of the range and its children.
int start = range->Start().InstructionIndex();
int end = 0;
for (LiveRange* cur = range; cur != NULL; cur = cur->next()) {
LifetimePosition this_end = cur->End();
if (this_end.InstructionIndex() > end) end = this_end.InstructionIndex();
DCHECK(cur->Start().InstructionIndex() >= start);
}
// Most of the ranges are in order, but not all. Keep an eye on when they
// step backwards and reset the first_it so we don't miss any safe points.
if (start < last_range_start) first_it = pointer_maps->begin();
last_range_start = start;
// Step across all the safe points that are before the start of this range,
// recording how far we step in order to save doing this for the next range.
for (; first_it != pointer_maps->end(); ++first_it) {
PointerMap* map = *first_it;
if (map->instruction_position() >= start) break;
}
// Step through the safe points to see whether they are in the range.
for (PointerMapDeque::const_iterator it = first_it;
it != pointer_maps->end(); ++it) {
PointerMap* map = *it;
int safe_point = map->instruction_position();
// The safe points are sorted so we can stop searching here.
if (safe_point - 1 > end) break;
// Advance to the next active range that covers the current
// safe point position.
LifetimePosition safe_point_pos =
LifetimePosition::FromInstructionIndex(safe_point);
LiveRange* cur = range;
while (cur != NULL && !cur->Covers(safe_point_pos)) {
cur = cur->next();
}
if (cur == NULL) continue;
// Check if the live range is spilled and the safe point is after
// the spill position.
if (range->HasAllocatedSpillOperand() &&
safe_point >= range->spill_start_index() &&
!range->GetSpillOperand()->IsConstant()) {
TraceAlloc("Pointer for range %d (spilled at %d) at safe point %d\n",
range->id(), range->spill_start_index(), safe_point);
map->RecordPointer(range->GetSpillOperand(), code_zone());
}
if (!cur->IsSpilled()) {
TraceAlloc(
"Pointer in register for range %d (start at %d) "
"at safe point %d\n",
cur->id(), cur->Start().Value(), safe_point);
InstructionOperand* operand = cur->CreateAssignedOperand(code_zone());
DCHECK(!operand->IsStackSlot());
map->RecordPointer(operand, code_zone());
}
}
}
}
void RegisterAllocator::AllocateGeneralRegisters() {
RegisterAllocatorPhase phase("L_Allocate general registers", this);
num_registers_ = Register::NumAllocatableRegisters();
mode_ = GENERAL_REGISTERS;
AllocateRegisters();
}
void RegisterAllocator::AllocateDoubleRegisters() {
RegisterAllocatorPhase phase("L_Allocate double registers", this);
num_registers_ = DoubleRegister::NumAllocatableRegisters();
mode_ = DOUBLE_REGISTERS;
AllocateRegisters();
}
void RegisterAllocator::AllocateRegisters() {
DCHECK(unhandled_live_ranges_.is_empty());
for (int i = 0; i < live_ranges_.length(); ++i) {
if (live_ranges_[i] != NULL) {
if (live_ranges_[i]->Kind() == mode_) {
AddToUnhandledUnsorted(live_ranges_[i]);
}
}
}
SortUnhandled();
DCHECK(UnhandledIsSorted());
DCHECK(reusable_slots_.is_empty());
DCHECK(active_live_ranges_.is_empty());
DCHECK(inactive_live_ranges_.is_empty());
if (mode_ == DOUBLE_REGISTERS) {
for (int i = 0; i < DoubleRegister::NumAllocatableRegisters(); ++i) {
LiveRange* current = fixed_double_live_ranges_.at(i);
if (current != NULL) {
AddToInactive(current);
}
}
} else {
DCHECK(mode_ == GENERAL_REGISTERS);
for (int i = 0; i < fixed_live_ranges_.length(); ++i) {
LiveRange* current = fixed_live_ranges_.at(i);
if (current != NULL) {
AddToInactive(current);
}
}
}
while (!unhandled_live_ranges_.is_empty()) {
DCHECK(UnhandledIsSorted());
LiveRange* current = unhandled_live_ranges_.RemoveLast();
DCHECK(UnhandledIsSorted());
LifetimePosition position = current->Start();
#ifdef DEBUG
allocation_finger_ = position;
#endif
TraceAlloc("Processing interval %d start=%d\n", current->id(),
position.Value());
if (current->HasAllocatedSpillOperand()) {
TraceAlloc("Live range %d already has a spill operand\n", current->id());
LifetimePosition next_pos = position;
if (code()->IsGapAt(next_pos.InstructionIndex())) {
next_pos = next_pos.NextInstruction();
}
UsePosition* pos = current->NextUsePositionRegisterIsBeneficial(next_pos);
// If the range already has a spill operand and it doesn't need a
// register immediately, split it and spill the first part of the range.
if (pos == NULL) {
Spill(current);
continue;
} else if (pos->pos().Value() >
current->Start().NextInstruction().Value()) {
// Do not spill live range eagerly if use position that can benefit from
// the register is too close to the start of live range.
SpillBetween(current, current->Start(), pos->pos());
if (!AllocationOk()) return;
DCHECK(UnhandledIsSorted());
continue;
}
}
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()) {
ActiveToHandled(cur_active);
--i; // The live range was removed from the list of active live ranges.
} else if (!cur_active->Covers(position)) {
ActiveToInactive(cur_active);
--i; // The live range was removed from the list of active live ranges.
}
}
for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
LiveRange* cur_inactive = inactive_live_ranges_.at(i);
if (cur_inactive->End().Value() <= position.Value()) {
InactiveToHandled(cur_inactive);
--i; // Live range was removed from the list of inactive live ranges.
} else if (cur_inactive->Covers(position)) {
InactiveToActive(cur_inactive);
--i; // Live range was removed from the list of inactive live ranges.
}
}
DCHECK(!current->HasRegisterAssigned() && !current->IsSpilled());
bool result = TryAllocateFreeReg(current);
if (!AllocationOk()) return;
if (!result) AllocateBlockedReg(current);
if (!AllocationOk()) return;
if (current->HasRegisterAssigned()) {
AddToActive(current);
}
}
reusable_slots_.Rewind(0);
active_live_ranges_.Rewind(0);
inactive_live_ranges_.Rewind(0);
}
const char* RegisterAllocator::RegisterName(int allocation_index) {
if (mode_ == GENERAL_REGISTERS) {
return Register::AllocationIndexToString(allocation_index);
} else {
return DoubleRegister::AllocationIndexToString(allocation_index);
}
}
void RegisterAllocator::TraceAlloc(const char* msg, ...) {
if (FLAG_trace_alloc) {
va_list arguments;
va_start(arguments, msg);
base::OS::VPrint(msg, arguments);
va_end(arguments);
}
}
bool RegisterAllocator::HasTaggedValue(int virtual_register) const {
return code()->IsReference(virtual_register);
}
RegisterKind RegisterAllocator::RequiredRegisterKind(
int virtual_register) const {
return (code()->IsDouble(virtual_register)) ? DOUBLE_REGISTERS
: GENERAL_REGISTERS;
}
void RegisterAllocator::AddToActive(LiveRange* range) {
TraceAlloc("Add live range %d to active\n", range->id());
active_live_ranges_.Add(range, zone());
}
void RegisterAllocator::AddToInactive(LiveRange* range) {
TraceAlloc("Add live range %d to inactive\n", range->id());
inactive_live_ranges_.Add(range, zone());
}
void RegisterAllocator::AddToUnhandledSorted(LiveRange* range) {
if (range == NULL || range->IsEmpty()) return;
DCHECK(!range->HasRegisterAssigned() && !range->IsSpilled());
DCHECK(allocation_finger_.Value() <= range->Start().Value());
for (int i = unhandled_live_ranges_.length() - 1; i >= 0; --i) {
LiveRange* cur_range = unhandled_live_ranges_.at(i);
if (range->ShouldBeAllocatedBefore(cur_range)) {
TraceAlloc("Add live range %d to unhandled at %d\n", range->id(), i + 1);
unhandled_live_ranges_.InsertAt(i + 1, range, zone());
DCHECK(UnhandledIsSorted());
return;
}
}
TraceAlloc("Add live range %d to unhandled at start\n", range->id());
unhandled_live_ranges_.InsertAt(0, range, zone());
DCHECK(UnhandledIsSorted());
}
void RegisterAllocator::AddToUnhandledUnsorted(LiveRange* range) {
if (range == NULL || range->IsEmpty()) return;
DCHECK(!range->HasRegisterAssigned() && !range->IsSpilled());
TraceAlloc("Add live range %d to unhandled unsorted at end\n", range->id());
unhandled_live_ranges_.Add(range, zone());
}
static int UnhandledSortHelper(LiveRange* const* a, LiveRange* const* b) {
DCHECK(!(*a)->ShouldBeAllocatedBefore(*b) ||
!(*b)->ShouldBeAllocatedBefore(*a));
if ((*a)->ShouldBeAllocatedBefore(*b)) return 1;
if ((*b)->ShouldBeAllocatedBefore(*a)) return -1;
return (*a)->id() - (*b)->id();
}
// Sort the unhandled live ranges so that the ranges to be processed first are
// at the end of the array list. This is convenient for the register allocation
// algorithm because it is efficient to remove elements from the end.
void RegisterAllocator::SortUnhandled() {
TraceAlloc("Sort unhandled\n");
unhandled_live_ranges_.Sort(&UnhandledSortHelper);
}
bool RegisterAllocator::UnhandledIsSorted() {
int len = unhandled_live_ranges_.length();
for (int i = 1; i < len; i++) {
LiveRange* a = unhandled_live_ranges_.at(i - 1);
LiveRange* b = unhandled_live_ranges_.at(i);
if (a->Start().Value() < b->Start().Value()) return false;
}
return true;
}
void RegisterAllocator::FreeSpillSlot(LiveRange* range) {
// Check that we are the last range.
if (range->next() != NULL) return;
if (!range->TopLevel()->HasAllocatedSpillOperand()) return;
InstructionOperand* spill_operand = range->TopLevel()->GetSpillOperand();
if (spill_operand->IsConstant()) return;
if (spill_operand->index() >= 0) {
reusable_slots_.Add(range, zone());
}
}
InstructionOperand* RegisterAllocator::TryReuseSpillSlot(LiveRange* range) {
if (reusable_slots_.is_empty()) return NULL;
if (reusable_slots_.first()->End().Value() >
range->TopLevel()->Start().Value()) {
return NULL;
}
InstructionOperand* result =
reusable_slots_.first()->TopLevel()->GetSpillOperand();
reusable_slots_.Remove(0);
return result;
}
void RegisterAllocator::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);
}
void RegisterAllocator::ActiveToInactive(LiveRange* range) {
DCHECK(active_live_ranges_.Contains(range));
active_live_ranges_.RemoveElement(range);
inactive_live_ranges_.Add(range, zone());
TraceAlloc("Moving live range %d from active to inactive\n", range->id());
}
void RegisterAllocator::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);
}
void RegisterAllocator::InactiveToActive(LiveRange* range) {
DCHECK(inactive_live_ranges_.Contains(range));
inactive_live_ranges_.RemoveElement(range);
active_live_ranges_.Add(range, zone());
TraceAlloc("Moving live range %d from inactive to active\n", range->id());
}
// TryAllocateFreeReg and AllocateBlockedReg assume this
// when allocating local arrays.
STATIC_ASSERT(DoubleRegister::kMaxNumAllocatableRegisters >=
Register::kMaxNumAllocatableRegisters);
bool RegisterAllocator::TryAllocateFreeReg(LiveRange* current) {
LifetimePosition free_until_pos[DoubleRegister::kMaxNumAllocatableRegisters];
for (int i = 0; i < num_registers_; i++) {
free_until_pos[i] = LifetimePosition::MaxPosition();
}
for (int i = 0; i < active_live_ranges_.length(); ++i) {
LiveRange* cur_active = active_live_ranges_.at(i);
free_until_pos[cur_active->assigned_register()] =
LifetimePosition::FromInstructionIndex(0);
}
for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
LiveRange* cur_inactive = inactive_live_ranges_.at(i);
DCHECK(cur_inactive->End().Value() > current->Start().Value());
LifetimePosition next_intersection =
cur_inactive->FirstIntersection(current);
if (!next_intersection.IsValid()) continue;
int cur_reg = cur_inactive->assigned_register();
free_until_pos[cur_reg] = Min(free_until_pos[cur_reg], next_intersection);
}
InstructionOperand* hint = current->FirstHint();
if (hint != NULL && (hint->IsRegister() || hint->IsDoubleRegister())) {
int register_index = hint->index();
TraceAlloc(
"Found reg hint %s (free until [%d) for live range %d (end %d[).\n",
RegisterName(register_index), free_until_pos[register_index].Value(),
current->id(), current->End().Value());
// The desired register is free until the end of the current live range.
if (free_until_pos[register_index].Value() >= current->End().Value()) {
TraceAlloc("Assigning preferred reg %s to live range %d\n",
RegisterName(register_index), current->id());
SetLiveRangeAssignedRegister(current, register_index);
return true;
}
}
// Find the register which stays free for the longest time.
int reg = 0;
for (int i = 1; i < RegisterCount(); ++i) {
if (free_until_pos[i].Value() > free_until_pos[reg].Value()) {
reg = i;
}
}
LifetimePosition pos = free_until_pos[reg];
if (pos.Value() <= current->Start().Value()) {
// All registers are blocked.
return false;
}
if (pos.Value() < current->End().Value()) {
// Register reg is available at the range start but becomes blocked before
// the range end. Split current at position where it becomes blocked.
LiveRange* tail = SplitRangeAt(current, pos);
if (!AllocationOk()) return false;
AddToUnhandledSorted(tail);
}
// Register reg is available at the range start and is free until
// the range end.
DCHECK(pos.Value() >= current->End().Value());
TraceAlloc("Assigning free reg %s to live range %d\n", RegisterName(reg),
current->id());
SetLiveRangeAssignedRegister(current, reg);
return true;
}
void RegisterAllocator::AllocateBlockedReg(LiveRange* current) {
UsePosition* register_use = current->NextRegisterPosition(current->Start());
if (register_use == NULL) {
// There is no use in the current live range that requires a register.
// We can just spill it.
Spill(current);
return;
}
LifetimePosition use_pos[DoubleRegister::kMaxNumAllocatableRegisters];
LifetimePosition block_pos[DoubleRegister::kMaxNumAllocatableRegisters];
for (int i = 0; i < num_registers_; i++) {
use_pos[i] = block_pos[i] = LifetimePosition::MaxPosition();
}
for (int i = 0; i < active_live_ranges_.length(); ++i) {
LiveRange* range = active_live_ranges_[i];
int cur_reg = range->assigned_register();
if (range->IsFixed() || !range->CanBeSpilled(current->Start())) {
block_pos[cur_reg] = use_pos[cur_reg] =
LifetimePosition::FromInstructionIndex(0);
} else {
UsePosition* next_use =
range->NextUsePositionRegisterIsBeneficial(current->Start());
if (next_use == NULL) {
use_pos[cur_reg] = range->End();
} else {
use_pos[cur_reg] = next_use->pos();
}
}
}
for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
LiveRange* range = inactive_live_ranges_.at(i);
DCHECK(range->End().Value() > current->Start().Value());
LifetimePosition next_intersection = range->FirstIntersection(current);
if (!next_intersection.IsValid()) continue;
int cur_reg = range->assigned_register();
if (range->IsFixed()) {
block_pos[cur_reg] = Min(block_pos[cur_reg], next_intersection);
use_pos[cur_reg] = Min(block_pos[cur_reg], use_pos[cur_reg]);
} else {
use_pos[cur_reg] = Min(use_pos[cur_reg], next_intersection);
}
}
int reg = 0;
for (int i = 1; i < RegisterCount(); ++i) {
if (use_pos[i].Value() > use_pos[reg].Value()) {
reg = i;
}
}
LifetimePosition pos = use_pos[reg];
if (pos.Value() < register_use->pos().Value()) {
// All registers are blocked before the first use that requires a register.
// Spill starting part of live range up to that use.
SpillBetween(current, current->Start(), register_use->pos());
return;
}
if (block_pos[reg].Value() < current->End().Value()) {
// Register becomes blocked before the current range end. Split before that
// position.
LiveRange* tail = SplitBetween(current, current->Start(),
block_pos[reg].InstructionStart());
if (!AllocationOk()) return;
AddToUnhandledSorted(tail);
}
// Register reg is not blocked for the whole range.
DCHECK(block_pos[reg].Value() >= current->End().Value());
TraceAlloc("Assigning blocked reg %s to live range %d\n", RegisterName(reg),
current->id());
SetLiveRangeAssignedRegister(current, reg);
// This register was not free. Thus we need to find and spill
// parts of active and inactive live regions that use the same register
// at the same lifetime positions as current.
SplitAndSpillIntersecting(current);
}
LifetimePosition RegisterAllocator::FindOptimalSpillingPos(
LiveRange* range, LifetimePosition pos) {
BasicBlock* block = GetBlock(pos.InstructionStart());
BasicBlock* loop_header =
block->IsLoopHeader() ? block : code()->GetContainingLoop(block);
if (loop_header == NULL) return pos;
UsePosition* prev_use = range->PreviousUsePositionRegisterIsBeneficial(pos);
while (loop_header != NULL) {
// We are going to spill live range inside the loop.
// If possible try to move spilling position backwards to loop header.
// This will reduce number of memory moves on the back edge.
LifetimePosition loop_start = LifetimePosition::FromInstructionIndex(
loop_header->first_instruction_index());
if (range->Covers(loop_start)) {
if (prev_use == NULL || prev_use->pos().Value() < loop_start.Value()) {
// No register beneficial use inside the loop before the pos.
pos = loop_start;
}
}
// Try hoisting out to an outer loop.
loop_header = code()->GetContainingLoop(loop_header);
}
return pos;
}
void RegisterAllocator::SplitAndSpillIntersecting(LiveRange* current) {
DCHECK(current->HasRegisterAssigned());
int reg = current->assigned_register();
LifetimePosition split_pos = current->Start();
for (int i = 0; i < active_live_ranges_.length(); ++i) {
LiveRange* range = active_live_ranges_[i];
if (range->assigned_register() == reg) {
UsePosition* next_pos = range->NextRegisterPosition(current->Start());
LifetimePosition spill_pos = FindOptimalSpillingPos(range, split_pos);
if (next_pos == NULL) {
SpillAfter(range, spill_pos);
} else {
// When spilling between spill_pos and next_pos ensure that the range
// remains spilled at least until the start of the current live range.
// This guarantees that we will not introduce new unhandled ranges that
// start before the current range as this violates allocation invariant
// and will lead to an inconsistent state of active and inactive
// live-ranges: ranges are allocated in order of their start positions,
// ranges are retired from active/inactive when the start of the
// current live-range is larger than their end.
SpillBetweenUntil(range, spill_pos, current->Start(), next_pos->pos());
}
if (!AllocationOk()) return;
ActiveToHandled(range);
--i;
}
}
for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
LiveRange* range = inactive_live_ranges_[i];
DCHECK(range->End().Value() > current->Start().Value());
if (range->assigned_register() == reg && !range->IsFixed()) {
LifetimePosition next_intersection = range->FirstIntersection(current);
if (next_intersection.IsValid()) {
UsePosition* next_pos = range->NextRegisterPosition(current->Start());
if (next_pos == NULL) {
SpillAfter(range, split_pos);
} else {
next_intersection = Min(next_intersection, next_pos->pos());
SpillBetween(range, split_pos, next_intersection);
}
if (!AllocationOk()) return;
InactiveToHandled(range);
--i;
}
}
}
}
bool RegisterAllocator::IsBlockBoundary(LifetimePosition pos) {
return pos.IsInstructionStart() &&
InstructionAt(pos.InstructionIndex())->IsBlockStart();
}
LiveRange* RegisterAllocator::SplitRangeAt(LiveRange* range,
LifetimePosition pos) {
DCHECK(!range->IsFixed());
TraceAlloc("Splitting live range %d at %d\n", range->id(), pos.Value());
if (pos.Value() <= range->Start().Value()) return range;
// We can't properly connect liveranges if split occured at the end
// of control instruction.
DCHECK(pos.IsInstructionStart() ||
!InstructionAt(pos.InstructionIndex())->IsControl());
int vreg = GetVirtualRegister();
if (!AllocationOk()) return NULL;
LiveRange* result = LiveRangeFor(vreg);
range->SplitAt(pos, result, zone());
return result;
}
LiveRange* RegisterAllocator::SplitBetween(LiveRange* range,
LifetimePosition start,
LifetimePosition end) {
DCHECK(!range->IsFixed());
TraceAlloc("Splitting live range %d in position between [%d, %d]\n",
range->id(), start.Value(), end.Value());
LifetimePosition split_pos = FindOptimalSplitPos(start, end);
DCHECK(split_pos.Value() >= start.Value());
return SplitRangeAt(range, split_pos);
}
LifetimePosition RegisterAllocator::FindOptimalSplitPos(LifetimePosition start,
LifetimePosition end) {
int start_instr = start.InstructionIndex();
int end_instr = end.InstructionIndex();
DCHECK(start_instr <= end_instr);
// We have no choice
if (start_instr == end_instr) return end;
BasicBlock* start_block = GetBlock(start);
BasicBlock* end_block = GetBlock(end);
if (end_block == start_block) {
// The interval is split in the same basic block. Split at the latest
// possible position.
return end;
}
BasicBlock* block = end_block;
// Find header of outermost loop.
// TODO(titzer): fix redundancy below.
while (code()->GetContainingLoop(block) != NULL &&
code()->GetContainingLoop(block)->rpo_number_ >
start_block->rpo_number_) {
block = code()->GetContainingLoop(block);
}
// We did not find any suitable outer loop. Split at the latest possible
// position unless end_block is a loop header itself.
if (block == end_block && !end_block->IsLoopHeader()) return end;
return LifetimePosition::FromInstructionIndex(
block->first_instruction_index());
}
void RegisterAllocator::SpillAfter(LiveRange* range, LifetimePosition pos) {
LiveRange* second_part = SplitRangeAt(range, pos);
if (!AllocationOk()) return;
Spill(second_part);
}
void RegisterAllocator::SpillBetween(LiveRange* range, LifetimePosition start,
LifetimePosition end) {
SpillBetweenUntil(range, start, start, end);
}
void RegisterAllocator::SpillBetweenUntil(LiveRange* range,
LifetimePosition start,
LifetimePosition until,
LifetimePosition end) {
CHECK(start.Value() < end.Value());
LiveRange* second_part = SplitRangeAt(range, start);
if (!AllocationOk()) return;
if (second_part->Start().Value() < end.Value()) {
// The split result intersects with [start, end[.
// Split it at position between ]start+1, end[, spill the middle part
// and put the rest to unhandled.
LiveRange* third_part = SplitBetween(
second_part, Max(second_part->Start().InstructionEnd(), until),
end.PrevInstruction().InstructionEnd());
if (!AllocationOk()) return;
DCHECK(third_part != second_part);
Spill(second_part);
AddToUnhandledSorted(third_part);
} else {
// The split result does not intersect with [start, end[.
// Nothing to spill. Just put it to unhandled as whole.
AddToUnhandledSorted(second_part);
}
}
void RegisterAllocator::Spill(LiveRange* range) {
DCHECK(!range->IsSpilled());
TraceAlloc("Spilling live range %d\n", range->id());
LiveRange* first = range->TopLevel();
if (!first->HasAllocatedSpillOperand()) {
InstructionOperand* op = TryReuseSpillSlot(range);
if (op == NULL) {
// Allocate a new operand referring to the spill slot.
RegisterKind kind = range->Kind();
int index = code()->frame()->AllocateSpillSlot(kind == DOUBLE_REGISTERS);
if (kind == DOUBLE_REGISTERS) {
op = DoubleStackSlotOperand::Create(index, zone());
} else {
DCHECK(kind == GENERAL_REGISTERS);
op = StackSlotOperand::Create(index, zone());
}
}
first->SetSpillOperand(op);
}
range->MakeSpilled(code_zone());
}
int RegisterAllocator::RegisterCount() const { return num_registers_; }
#ifdef DEBUG
void RegisterAllocator::Verify() const {
for (int i = 0; i < live_ranges()->length(); ++i) {
LiveRange* current = live_ranges()->at(i);
if (current != NULL) current->Verify();
}
}
#endif
void RegisterAllocator::SetLiveRangeAssignedRegister(LiveRange* range,
int reg) {
if (range->Kind() == DOUBLE_REGISTERS) {
assigned_double_registers_->Add(reg);
} else {
DCHECK(range->Kind() == GENERAL_REGISTERS);
assigned_registers_->Add(reg);
}
range->set_assigned_register(reg, code_zone());
}
RegisterAllocatorPhase::RegisterAllocatorPhase(const char* name,
RegisterAllocator* allocator)
: CompilationPhase(name, allocator->code()->linkage()->info()),
allocator_(allocator) {
if (FLAG_turbo_stats) {
allocator_zone_start_allocation_size_ =
allocator->zone()->allocation_size();
}
}
RegisterAllocatorPhase::~RegisterAllocatorPhase() {
if (FLAG_turbo_stats) {
unsigned size = allocator_->zone()->allocation_size() -
allocator_zone_start_allocation_size_;
isolate()->GetTStatistics()->SaveTiming(name(), base::TimeDelta(), size);
}
#ifdef DEBUG
if (allocator_ != NULL) allocator_->Verify();
#endif
}
}
}
} // namespace v8::internal::compiler