// Copyright 2011 the V8 project authors. All rights reserved. // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions are // met: // // * Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // * Redistributions in binary form must reproduce the above // copyright notice, this list of conditions and the following // disclaimer in the documentation and/or other materials provided // with the distribution. // * Neither the name of Google Inc. nor the names of its // contributors may be used to endorse or promote products derived // from this software without specific prior written permission. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. #include "v8.h" #include "lithium-allocator-inl.h" #include "hydrogen.h" #include "string-stream.h" #if V8_TARGET_ARCH_IA32 #include "ia32/lithium-ia32.h" #elif V8_TARGET_ARCH_X64 #include "x64/lithium-x64.h" #elif V8_TARGET_ARCH_ARM #include "arm/lithium-arm.h" #elif V8_TARGET_ARCH_MIPS #include "mips/lithium-mips.h" #else #error "Unknown architecture." #endif namespace v8 { namespace internal { #define DEFINE_OPERAND_CACHE(name, type) \ name name::cache[name::kNumCachedOperands]; \ void name::SetupCache() { \ for (int i = 0; i < kNumCachedOperands; i++) { \ cache[i].ConvertTo(type, i); \ } \ } \ static bool name##_initialize() { \ name::SetupCache(); \ return true; \ } \ static bool name##_cache_initialized = name##_initialize(); DEFINE_OPERAND_CACHE(LConstantOperand, CONSTANT_OPERAND) DEFINE_OPERAND_CACHE(LStackSlot, STACK_SLOT) DEFINE_OPERAND_CACHE(LDoubleStackSlot, DOUBLE_STACK_SLOT) DEFINE_OPERAND_CACHE(LRegister, REGISTER) DEFINE_OPERAND_CACHE(LDoubleRegister, DOUBLE_REGISTER) #undef DEFINE_OPERAND_CACHE 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, LOperand* operand) : operand_(operand), hint_(NULL), pos_(pos), next_(NULL), requires_reg_(false), register_beneficial_(true) { if (operand_ != NULL && operand_->IsUnallocated()) { LUnallocated* unalloc = LUnallocated::cast(operand_); requires_reg_ = unalloc->HasRegisterPolicy(); register_beneficial_ = !unalloc->HasAnyPolicy(); } ASSERT(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) { ASSERT(Contains(pos) && pos.Value() != start().Value()); UseInterval* after = new UseInterval(pos, end_); after->next_ = next_; next_ = after; end_ = pos; } #ifdef DEBUG void LiveRange::Verify() const { UsePosition* cur = first_pos_; while (cur != NULL) { ASSERT(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) : id_(id), spilled_(false), assigned_register_(kInvalidAssignment), assigned_register_kind_(NONE), last_interval_(NULL), first_interval_(NULL), first_pos_(NULL), parent_(NULL), next_(NULL), current_interval_(NULL), last_processed_use_(NULL), spill_start_index_(kMaxInt) { spill_operand_ = new LUnallocated(LUnallocated::IGNORE); } void LiveRange::set_assigned_register(int reg, RegisterKind register_kind) { ASSERT(!HasRegisterAssigned() && !IsSpilled()); assigned_register_ = reg; assigned_register_kind_ = register_kind; ConvertOperands(); } void LiveRange::MakeSpilled() { ASSERT(!IsSpilled()); ASSERT(TopLevel()->HasAllocatedSpillOperand()); spilled_ = true; assigned_register_ = kInvalidAssignment; ConvertOperands(); } bool LiveRange::HasAllocatedSpillOperand() const { return spill_operand_ != NULL && !spill_operand_->IsUnallocated(); } void LiveRange::SetSpillOperand(LOperand* operand) { ASSERT(!operand->IsUnallocated()); ASSERT(spill_operand_ != NULL); ASSERT(spill_operand_->IsUnallocated()); 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::NextRegisterPosition(LifetimePosition start) { UsePosition* pos = NextUsePosition(start); while (pos != NULL && !pos->RequiresRegister()) { pos = pos->next(); } return pos; } bool LiveRange::CanBeSpilled(LifetimePosition pos) { // TODO(kmillikin): Comment. Now. if (pos.Value() <= Start().Value() && HasRegisterAssigned()) return false; // 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().Value(); } UsePosition* LiveRange::FirstPosWithHint() const { UsePosition* pos = first_pos_; while (pos != NULL && !pos->HasHint()) pos = pos->next(); return pos; } LOperand* LiveRange::CreateAssignedOperand() { LOperand* op = NULL; if (HasRegisterAssigned()) { ASSERT(!IsSpilled()); if (IsDouble()) { op = LDoubleRegister::Create(assigned_register()); } else { op = LRegister::Create(assigned_register()); } } else if (IsSpilled()) { ASSERT(!HasRegisterAssigned()); op = TopLevel()->GetSpillOperand(); ASSERT(!op->IsUnallocated()); } else { LUnallocated* unalloc = new LUnallocated(LUnallocated::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) { ASSERT(Start().Value() < position.Value()); ASSERT(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); 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->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 = FirstPosWithHint(); 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) { LAllocator::TraceAlloc("Shorten live range %d to [%d\n", id_, start.Value()); ASSERT(first_interval_ != NULL); ASSERT(first_interval_->start().Value() <= start.Value()); ASSERT(start.Value() < first_interval_->end().Value()); first_interval_->set_start(start); } void LiveRange::EnsureInterval(LifetimePosition start, LifetimePosition end) { LAllocator::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 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) { LAllocator::TraceAlloc("Add to live range %d interval [%d %d[\n", id_, start.Value(), end.Value()); if (first_interval_ == NULL) { UseInterval* interval = new 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 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. ASSERT(start.Value() < first_interval_->end().Value()); first_interval_->start_ = Min(start, first_interval_->start_); first_interval_->end_ = Max(end, first_interval_->end_); } } } UsePosition* LiveRange::AddUsePosition(LifetimePosition pos, LOperand* operand) { LAllocator::TraceAlloc("Add to live range %d use position %d\n", id_, pos.Value()); UsePosition* use_pos = new UsePosition(pos, operand); UsePosition* prev = NULL; UsePosition* current = first_pos_; while (current != NULL && current->pos().Value() < pos.Value()) { 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; } return use_pos; } void LiveRange::ConvertOperands() { LOperand* op = CreateAssignedOperand(); UsePosition* use_pos = first_pos(); while (use_pos != NULL) { ASSERT(Start().Value() <= use_pos->pos().Value() && use_pos->pos().Value() <= End().Value()); if (use_pos->HasOperand()) { ASSERT(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()) { ASSERT(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(); } LAllocator::LAllocator(int num_values, HGraph* graph) : chunk_(NULL), live_in_sets_(graph->blocks()->length()), live_ranges_(num_values * 2), fixed_live_ranges_(NULL), fixed_double_live_ranges_(NULL), unhandled_live_ranges_(num_values * 2), active_live_ranges_(8), inactive_live_ranges_(8), reusable_slots_(8), next_virtual_register_(num_values), first_artificial_register_(num_values), mode_(NONE), num_registers_(-1), graph_(graph), has_osr_entry_(false) {} void LAllocator::InitializeLivenessAnalysis() { // Initialize the live_in sets for each block to NULL. int block_count = graph_->blocks()->length(); live_in_sets_.Initialize(block_count); live_in_sets_.AddBlock(NULL, block_count); } BitVector* LAllocator::ComputeLiveOut(HBasicBlock* block) { // Compute live out for the given block, except not including backward // successor edges. BitVector* live_out = new BitVector(next_virtual_register_); // Process all successor blocks. for (HSuccessorIterator it(block->end()); !it.Done(); it.Advance()) { // Add values live on entry to the successor. Note the successor's // live_in will not be computed yet for backwards edges. HBasicBlock* successor = it.Current(); BitVector* live_in = live_in_sets_[successor->block_id()]; 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); const ZoneList<HPhi*>* phis = successor->phis(); for (int i = 0; i < phis->length(); ++i) { HPhi* phi = phis->at(i); if (!phi->OperandAt(index)->IsConstant()) { live_out->Add(phi->OperandAt(index)->id()); } } } return live_out; } void LAllocator::AddInitialIntervals(HBasicBlock* 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); iterator.Advance(); } } int LAllocator::FixedDoubleLiveRangeID(int index) { return -index - 1 - Register::kNumAllocatableRegisters; } LOperand* LAllocator::AllocateFixed(LUnallocated* operand, int pos, bool is_tagged) { TraceAlloc("Allocating fixed reg for op %d\n", operand->virtual_register()); ASSERT(operand->HasFixedPolicy()); if (operand->policy() == LUnallocated::FIXED_SLOT) { operand->ConvertTo(LOperand::STACK_SLOT, operand->fixed_index()); } else if (operand->policy() == LUnallocated::FIXED_REGISTER) { int reg_index = operand->fixed_index(); operand->ConvertTo(LOperand::REGISTER, reg_index); } else if (operand->policy() == LUnallocated::FIXED_DOUBLE_REGISTER) { int reg_index = operand->fixed_index(); operand->ConvertTo(LOperand::DOUBLE_REGISTER, reg_index); } else { UNREACHABLE(); } if (is_tagged) { TraceAlloc("Fixed reg is tagged at %d\n", pos); LInstruction* instr = InstructionAt(pos); if (instr->HasPointerMap()) { instr->pointer_map()->RecordPointer(operand); } } return operand; } LiveRange* LAllocator::FixedLiveRangeFor(int index) { ASSERT(index < Register::kNumAllocatableRegisters); LiveRange* result = fixed_live_ranges_[index]; if (result == NULL) { result = new LiveRange(FixedLiveRangeID(index)); ASSERT(result->IsFixed()); result->set_assigned_register(index, GENERAL_REGISTERS); fixed_live_ranges_[index] = result; } return result; } LiveRange* LAllocator::FixedDoubleLiveRangeFor(int index) { ASSERT(index < DoubleRegister::kNumAllocatableRegisters); LiveRange* result = fixed_double_live_ranges_[index]; if (result == NULL) { result = new LiveRange(FixedDoubleLiveRangeID(index)); ASSERT(result->IsFixed()); result->set_assigned_register(index, DOUBLE_REGISTERS); fixed_double_live_ranges_[index] = result; } return result; } LiveRange* LAllocator::LiveRangeFor(int index) { if (index >= live_ranges_.length()) { live_ranges_.AddBlock(NULL, index - live_ranges_.length() + 1); } LiveRange* result = live_ranges_[index]; if (result == NULL) { result = new LiveRange(index); live_ranges_[index] = result; } return result; } LGap* LAllocator::GetLastGap(HBasicBlock* block) { int last_instruction = block->last_instruction_index(); int index = chunk_->NearestGapPos(last_instruction); return GapAt(index); } HPhi* LAllocator::LookupPhi(LOperand* operand) const { if (!operand->IsUnallocated()) return NULL; int index = operand->VirtualRegister(); HValue* instr = graph_->LookupValue(index); if (instr != NULL && instr->IsPhi()) { return HPhi::cast(instr); } return NULL; } LiveRange* LAllocator::LiveRangeFor(LOperand* operand) { if (operand->IsUnallocated()) { return LiveRangeFor(LUnallocated::cast(operand)->virtual_register()); } else if (operand->IsRegister()) { return FixedLiveRangeFor(operand->index()); } else if (operand->IsDoubleRegister()) { return FixedDoubleLiveRangeFor(operand->index()); } else { return NULL; } } void LAllocator::Define(LifetimePosition position, LOperand* operand, LOperand* 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()); range->AddUsePosition(position.NextInstruction(), NULL); } else { range->ShortenTo(position); } if (operand->IsUnallocated()) { LUnallocated* unalloc_operand = LUnallocated::cast(operand); range->AddUsePosition(position, unalloc_operand)->set_hint(hint); } } void LAllocator::Use(LifetimePosition block_start, LifetimePosition position, LOperand* operand, LOperand* hint) { LiveRange* range = LiveRangeFor(operand); if (range == NULL) return; if (operand->IsUnallocated()) { LUnallocated* unalloc_operand = LUnallocated::cast(operand); range->AddUsePosition(position, unalloc_operand)->set_hint(hint); } range->AddUseInterval(block_start, position); } void LAllocator::AddConstraintsGapMove(int index, LOperand* from, LOperand* to) { LGap* gap = GapAt(index); LParallelMove* move = gap->GetOrCreateParallelMove(LGap::START); if (from->IsUnallocated()) { const ZoneList<LMoveOperands>* move_operands = move->move_operands(); for (int i = 0; i < move_operands->length(); ++i) { LMoveOperands cur = move_operands->at(i); LOperand* cur_to = cur.destination(); if (cur_to->IsUnallocated()) { if (cur_to->VirtualRegister() == from->VirtualRegister()) { move->AddMove(cur.source(), to); return; } } } } move->AddMove(from, to); } void LAllocator::MeetRegisterConstraints(HBasicBlock* block) { int start = block->first_instruction_index(); int end = block->last_instruction_index(); for (int i = start; i <= end; ++i) { if (IsGapAt(i)) { LInstruction* instr = NULL; LInstruction* prev_instr = NULL; if (i < end) instr = InstructionAt(i + 1); if (i > start) prev_instr = InstructionAt(i - 1); MeetConstraintsBetween(prev_instr, instr, i); } } } void LAllocator::MeetConstraintsBetween(LInstruction* first, LInstruction* second, int gap_index) { // Handle fixed temporaries. if (first != NULL) { for (TempIterator it(first); !it.Done(); it.Advance()) { LUnallocated* temp = LUnallocated::cast(it.Current()); if (temp->HasFixedPolicy()) { AllocateFixed(temp, gap_index - 1, false); } } } // Handle fixed output operand. if (first != NULL && first->Output() != NULL) { LUnallocated* first_output = LUnallocated::cast(first->Output()); LiveRange* range = LiveRangeFor(first_output->VirtualRegister()); bool assigned = false; if (first_output->HasFixedPolicy()) { LUnallocated* output_copy = first_output->CopyUnconstrained(); bool is_tagged = HasTaggedValue(first_output->VirtualRegister()); 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; } chunk_->AddGapMove(gap_index, first_output, output_copy); } 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. LGap* gap = GapAt(gap_index); LParallelMove* move = gap->GetOrCreateParallelMove(LGap::BEFORE); move->AddMove(first_output, range->GetSpillOperand()); } } // Handle fixed input operands of second instruction. if (second != NULL) { for (UseIterator it(second); !it.Done(); it.Advance()) { LUnallocated* cur_input = LUnallocated::cast(it.Current()); if (cur_input->HasFixedPolicy()) { LUnallocated* input_copy = cur_input->CopyUnconstrained(); bool is_tagged = HasTaggedValue(cur_input->VirtualRegister()); AllocateFixed(cur_input, gap_index + 1, is_tagged); AddConstraintsGapMove(gap_index, input_copy, cur_input); } else if (cur_input->policy() == LUnallocated::WRITABLE_REGISTER) { // The live range of writable input registers always goes until the end // of the instruction. ASSERT(!cur_input->IsUsedAtStart()); LUnallocated* input_copy = cur_input->CopyUnconstrained(); cur_input->set_virtual_register(next_virtual_register_++); if (RequiredRegisterKind(input_copy->virtual_register()) == DOUBLE_REGISTERS) { double_artificial_registers_.Add( cur_input->virtual_register() - first_artificial_register_); } AddConstraintsGapMove(gap_index, input_copy, cur_input); } } } // Handle "output same as input" for second instruction. if (second != NULL && second->Output() != NULL) { LUnallocated* second_output = LUnallocated::cast(second->Output()); if (second_output->HasSameAsInputPolicy()) { LUnallocated* cur_input = LUnallocated::cast(second->FirstInput()); int output_vreg = second_output->VirtualRegister(); int input_vreg = cur_input->VirtualRegister(); LUnallocated* input_copy = cur_input->CopyUnconstrained(); 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; LInstruction* instr = InstructionAt(index); if (instr->HasPointerMap()) { instr->pointer_map()->RecordPointer(input_copy); } } 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. } } } } void LAllocator::ProcessInstructions(HBasicBlock* block, BitVector* live) { int block_start = block->first_instruction_index(); int index = block->last_instruction_index(); LifetimePosition block_start_position = LifetimePosition::FromInstructionIndex(block_start); while (index >= block_start) { LifetimePosition curr_position = LifetimePosition::FromInstructionIndex(index); if (IsGapAt(index)) { // We have a gap at this position. LGap* gap = GapAt(index); LParallelMove* move = gap->GetOrCreateParallelMove(LGap::START); const ZoneList<LMoveOperands>* move_operands = move->move_operands(); for (int i = 0; i < move_operands->length(); ++i) { LMoveOperands* cur = &move_operands->at(i); if (cur->IsIgnored()) continue; LOperand* from = cur->source(); LOperand* to = cur->destination(); HPhi* phi = LookupPhi(to); LOperand* hint = to; if (phi != NULL) { // This is a phi resolving move. if (!phi->block()->IsLoopHeader()) { hint = LiveRangeFor(phi->id())->FirstHint(); } } else { if (to->IsUnallocated()) { if (live->Contains(to->VirtualRegister())) { Define(curr_position, to, from); live->Remove(to->VirtualRegister()); } else { cur->Eliminate(); continue; } } else { Define(curr_position, to, from); } } Use(block_start_position, curr_position, from, hint); if (from->IsUnallocated()) { live->Add(from->VirtualRegister()); } } } else { ASSERT(!IsGapAt(index)); LInstruction* instr = InstructionAt(index); if (instr != NULL) { LOperand* output = instr->Output(); if (output != NULL) { if (output->IsUnallocated()) live->Remove(output->VirtualRegister()); Define(curr_position, output, NULL); } if (instr->IsMarkedAsCall()) { for (int i = 0; i < Register::kNumAllocatableRegisters; ++i) { if (output == NULL || !output->IsRegister() || output->index() != i) { LiveRange* range = FixedLiveRangeFor(i); range->AddUseInterval(curr_position, curr_position.InstructionEnd()); } } } if (instr->IsMarkedAsCall() || instr->IsMarkedAsSaveDoubles()) { for (int i = 0; i < DoubleRegister::kNumAllocatableRegisters; ++i) { if (output == NULL || !output->IsDoubleRegister() || output->index() != i) { LiveRange* range = FixedDoubleLiveRangeFor(i); range->AddUseInterval(curr_position, curr_position.InstructionEnd()); } } } for (UseIterator it(instr); !it.Done(); it.Advance()) { LOperand* input = it.Current(); LifetimePosition use_pos; if (input->IsUnallocated() && LUnallocated::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(input->VirtualRegister()); } for (TempIterator it(instr); !it.Done(); it.Advance()) { LOperand* temp = it.Current(); if (instr->IsMarkedAsCall()) { if (temp->IsRegister()) continue; if (temp->IsUnallocated()) { LUnallocated* temp_unalloc = LUnallocated::cast(temp); if (temp_unalloc->HasFixedPolicy()) { continue; } } } Use(block_start_position, curr_position.InstructionEnd(), temp, NULL); Define(curr_position, temp, NULL); } } } index = index - 1; } } void LAllocator::ResolvePhis(HBasicBlock* block) { const ZoneList<HPhi*>* phis = block->phis(); for (int i = 0; i < phis->length(); ++i) { HPhi* phi = phis->at(i); LUnallocated* phi_operand = new LUnallocated(LUnallocated::NONE); phi_operand->set_virtual_register(phi->id()); for (int j = 0; j < phi->OperandCount(); ++j) { HValue* op = phi->OperandAt(j); LOperand* operand = NULL; if (op->IsConstant() && op->EmitAtUses()) { HConstant* constant = HConstant::cast(op); operand = chunk_->DefineConstantOperand(constant); } else { ASSERT(!op->EmitAtUses()); LUnallocated* unalloc = new LUnallocated(LUnallocated::ANY); unalloc->set_virtual_register(op->id()); operand = unalloc; } HBasicBlock* cur_block = block->predecessors()->at(j); // The gap move must be added without any special processing as in // the AddConstraintsGapMove. chunk_->AddGapMove(cur_block->last_instruction_index() - 1, operand, phi_operand); // We are going to insert a move before the branch instruction. // Some branch instructions (e.g. loops' back edges) // can potentially cause a GC so they have a pointer map. // By inserting a move we essentially create a copy of a // value which is invisible to PopulatePointerMaps(), because we store // it into a location different from the operand of a live range // covering a branch instruction. // Thus we need to manually record a pointer. if (phi->representation().IsTagged()) { LInstruction* branch = InstructionAt(cur_block->last_instruction_index()); if (branch->HasPointerMap()) { branch->pointer_map()->RecordPointer(phi_operand); } } } LiveRange* live_range = LiveRangeFor(phi->id()); LLabel* label = chunk_->GetLabel(phi->block()->block_id()); label->GetOrCreateParallelMove(LGap::START)-> AddMove(phi_operand, live_range->GetSpillOperand()); live_range->SetSpillStartIndex(phi->block()->first_instruction_index()); } } void LAllocator::Allocate(LChunk* chunk) { ASSERT(chunk_ == NULL); chunk_ = chunk; MeetRegisterConstraints(); ResolvePhis(); BuildLiveRanges(); AllocateGeneralRegisters(); AllocateDoubleRegisters(); PopulatePointerMaps(); if (has_osr_entry_) ProcessOsrEntry(); ConnectRanges(); ResolveControlFlow(); } void LAllocator::MeetRegisterConstraints() { HPhase phase("Register constraints", chunk_); first_artificial_register_ = next_virtual_register_; const ZoneList<HBasicBlock*>* blocks = graph_->blocks(); for (int i = 0; i < blocks->length(); ++i) { HBasicBlock* block = blocks->at(i); MeetRegisterConstraints(block); } } void LAllocator::ResolvePhis() { HPhase phase("Resolve phis", chunk_); // Process the blocks in reverse order. const ZoneList<HBasicBlock*>* blocks = graph_->blocks(); for (int block_id = blocks->length() - 1; block_id >= 0; --block_id) { HBasicBlock* block = blocks->at(block_id); ResolvePhis(block); } } void LAllocator::ResolveControlFlow(LiveRange* range, HBasicBlock* block, HBasicBlock* 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)) { ASSERT(cur_cover == NULL); cur_cover = cur_range; } if (cur_range->CanCover(pred_end)) { ASSERT(pred_cover == NULL); pred_cover = cur_range; } cur_range = cur_range->next(); } if (cur_cover->IsSpilled()) return; ASSERT(pred_cover != NULL && cur_cover != NULL); if (pred_cover != cur_cover) { LOperand* pred_op = pred_cover->CreateAssignedOperand(); LOperand* cur_op = cur_cover->CreateAssignedOperand(); if (!pred_op->Equals(cur_op)) { LGap* gap = NULL; if (block->predecessors()->length() == 1) { gap = GapAt(block->first_instruction_index()); } else { ASSERT(pred->end()->SecondSuccessor() == NULL); gap = GetLastGap(pred); // We are going to insert a move before the branch instruction. // Some branch instructions (e.g. loops' back edges) // can potentially cause a GC so they have a pointer map. // By inserting a move we essentially create a copy of a // value which is invisible to PopulatePointerMaps(), because we store // it into a location different from the operand of a live range // covering a branch instruction. // Thus we need to manually record a pointer. if (HasTaggedValue(range->id())) { LInstruction* branch = InstructionAt(pred->last_instruction_index()); if (branch->HasPointerMap()) { branch->pointer_map()->RecordPointer(cur_op); } } } gap->GetOrCreateParallelMove(LGap::START)->AddMove(pred_op, cur_op); } } } LParallelMove* LAllocator::GetConnectingParallelMove(LifetimePosition pos) { int index = pos.InstructionIndex(); if (IsGapAt(index)) { LGap* gap = GapAt(index); return gap->GetOrCreateParallelMove( pos.IsInstructionStart() ? LGap::START : LGap::END); } int gap_pos = pos.IsInstructionStart() ? (index - 1) : (index + 1); return GapAt(gap_pos)->GetOrCreateParallelMove( (gap_pos < index) ? LGap::AFTER : LGap::BEFORE); } HBasicBlock* LAllocator::GetBlock(LifetimePosition pos) { LGap* gap = GapAt(chunk_->NearestGapPos(pos.InstructionIndex())); return gap->block(); } void LAllocator::ConnectRanges() { HPhase phase("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) { LParallelMove* move = GetConnectingParallelMove(pos); LOperand* prev_operand = first_range->CreateAssignedOperand(); LOperand* cur_operand = second_range->CreateAssignedOperand(); move->AddMove(prev_operand, cur_operand); } } } first_range = second_range; second_range = second_range->next(); } } } bool LAllocator::CanEagerlyResolveControlFlow(HBasicBlock* block) const { if (block->predecessors()->length() != 1) return false; return block->predecessors()->first()->block_id() == block->block_id() - 1; } void LAllocator::ResolveControlFlow() { HPhase phase("Resolve control flow", this); const ZoneList<HBasicBlock*>* blocks = graph_->blocks(); for (int block_id = 1; block_id < blocks->length(); ++block_id) { HBasicBlock* block = blocks->at(block_id); if (CanEagerlyResolveControlFlow(block)) continue; BitVector* live = live_in_sets_[block->block_id()]; BitVector::Iterator iterator(live); while (!iterator.Done()) { int operand_index = iterator.Current(); for (int i = 0; i < block->predecessors()->length(); ++i) { HBasicBlock* cur = block->predecessors()->at(i); LiveRange* cur_range = LiveRangeFor(operand_index); ResolveControlFlow(cur_range, block, cur); } iterator.Advance(); } } } void LAllocator::BuildLiveRanges() { HPhase phase("Build live ranges", this); InitializeLivenessAnalysis(); // Process the blocks in reverse order. const ZoneList<HBasicBlock*>* blocks = graph_->blocks(); for (int block_id = blocks->length() - 1; block_id >= 0; --block_id) { HBasicBlock* block = blocks->at(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. const ZoneList<HPhi*>* phis = block->phis(); for (int i = 0; i < phis->length(); ++i) { // The live range interval already ends at the first instruction of the // block. HPhi* phi = phis->at(i); live->Remove(phi->id()); LOperand* hint = NULL; LOperand* phi_operand = NULL; LGap* gap = GetLastGap(phi->block()->predecessors()->at(0)); LParallelMove* move = gap->GetOrCreateParallelMove(LGap::START); for (int j = 0; j < move->move_operands()->length(); ++j) { LOperand* to = move->move_operands()->at(j).destination(); if (to->IsUnallocated() && to->VirtualRegister() == phi->id()) { hint = move->move_operands()->at(j).source(); phi_operand = to; break; } } ASSERT(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 this block is a loop header go back and patch up the necessary // predecessor blocks. if (block->IsLoopHeader()) { // TODO(kmillikin): Need to be able to get the last block of the loop // in the loop information. Add a live range stretching from the first // loop instruction to the last for each value live on entry to the // header. HBasicBlock* back_edge = block->loop_information()->GetLastBackEdge(); BitVector::Iterator iterator(live); LifetimePosition start = LifetimePosition::FromInstructionIndex( block->first_instruction_index()); LifetimePosition end = LifetimePosition::FromInstructionIndex( back_edge->last_instruction_index()).NextInstruction(); while (!iterator.Done()) { int operand_index = iterator.Current(); LiveRange* range = LiveRangeFor(operand_index); range->EnsureInterval(start, end); iterator.Advance(); } for (int i = block->block_id() + 1; i <= back_edge->block_id(); ++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("Function: %s\n", *chunk_->info()->function()->debug_name()->ToCString()); PrintF("Value %d used before first definition!\n", operand_index); LiveRange* range = LiveRangeFor(operand_index); PrintF("First use is at %d\n", range->first_pos()->pos().Value()); iterator.Advance(); } ASSERT(!found); } #endif } } bool LAllocator::SafePointsAreInOrder() const { const ZoneList<LPointerMap*>* pointer_maps = chunk_->pointer_maps(); int safe_point = 0; for (int i = 0; i < pointer_maps->length(); ++i) { LPointerMap* map = pointer_maps->at(i); if (safe_point > map->lithium_position()) return false; safe_point = map->lithium_position(); } return true; } void LAllocator::PopulatePointerMaps() { HPhase phase("Populate pointer maps", this); const ZoneList<LPointerMap*>* pointer_maps = chunk_->pointer_maps(); ASSERT(SafePointsAreInOrder()); // Iterate over all safe point positions and record a pointer // for all spilled live ranges at this point. int first_safe_point_index = 0; int last_range_start = 0; 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-pointer 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(); ASSERT(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_safe_point_index so we don't // miss any safe points. if (start < last_range_start) { first_safe_point_index = 0; } 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. while (first_safe_point_index < pointer_maps->length()) { LPointerMap* map = pointer_maps->at(first_safe_point_index); int safe_point = map->lithium_position(); if (safe_point >= start) break; first_safe_point_index++; } // Step through the safe points to see whether they are in the range. for (int safe_point_index = first_safe_point_index; safe_point_index < pointer_maps->length(); ++safe_point_index) { LPointerMap* map = pointer_maps->at(safe_point_index); int safe_point = map->lithium_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.PrevInstruction())) { 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()) { 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()); } 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); LOperand* operand = cur->CreateAssignedOperand(); ASSERT(!operand->IsStackSlot()); map->RecordPointer(operand); } } } } void LAllocator::ProcessOsrEntry() { const ZoneList<LInstruction*>* instrs = chunk_->instructions(); // Linear search for the OSR entry instruction in the chunk. int index = -1; while (++index < instrs->length() && !instrs->at(index)->IsOsrEntry()) { } ASSERT(index < instrs->length()); LOsrEntry* instruction = LOsrEntry::cast(instrs->at(index)); LifetimePosition position = LifetimePosition::FromInstructionIndex(index); for (int i = 0; i < live_ranges()->length(); ++i) { LiveRange* range = live_ranges()->at(i); if (range != NULL) { if (range->Covers(position) && range->HasRegisterAssigned() && range->TopLevel()->HasAllocatedSpillOperand()) { int reg_index = range->assigned_register(); LOperand* spill_operand = range->TopLevel()->GetSpillOperand(); if (range->IsDouble()) { instruction->MarkSpilledDoubleRegister(reg_index, spill_operand); } else { instruction->MarkSpilledRegister(reg_index, spill_operand); } } } } } void LAllocator::AllocateGeneralRegisters() { HPhase phase("Allocate general registers", this); num_registers_ = Register::kNumAllocatableRegisters; mode_ = GENERAL_REGISTERS; AllocateRegisters(); } void LAllocator::AllocateDoubleRegisters() { HPhase phase("Allocate double registers", this); num_registers_ = DoubleRegister::kNumAllocatableRegisters; mode_ = DOUBLE_REGISTERS; AllocateRegisters(); } void LAllocator::AllocateRegisters() { ASSERT(mode_ != NONE); ASSERT(unhandled_live_ranges_.is_empty()); for (int i = 0; i < live_ranges_.length(); ++i) { if (live_ranges_[i] != NULL) { if (RequiredRegisterKind(live_ranges_[i]->id()) == mode_) { AddToUnhandledUnsorted(live_ranges_[i]); } } } SortUnhandled(); ASSERT(UnhandledIsSorted()); ASSERT(reusable_slots_.is_empty()); ASSERT(active_live_ranges_.is_empty()); ASSERT(inactive_live_ranges_.is_empty()); if (mode_ == DOUBLE_REGISTERS) { for (int i = 0; i < fixed_double_live_ranges_.length(); ++i) { LiveRange* current = fixed_double_live_ranges_.at(i); if (current != NULL) { AddToInactive(current); } } } else { 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()) { ASSERT(UnhandledIsSorted()); LiveRange* current = unhandled_live_ranges_.RemoveLast(); ASSERT(UnhandledIsSorted()); LifetimePosition position = current->Start(); 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 (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()); ASSERT(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. } } ASSERT(!current->HasRegisterAssigned() && !current->IsSpilled()); bool result = TryAllocateFreeReg(current); if (!result) { AllocateBlockedReg(current); } if (current->HasRegisterAssigned()) { AddToActive(current); } } reusable_slots_.Rewind(0); active_live_ranges_.Rewind(0); inactive_live_ranges_.Rewind(0); } const char* LAllocator::RegisterName(int allocation_index) { ASSERT(mode_ != NONE); if (mode_ == GENERAL_REGISTERS) { return Register::AllocationIndexToString(allocation_index); } else { return DoubleRegister::AllocationIndexToString(allocation_index); } } void LAllocator::TraceAlloc(const char* msg, ...) { if (FLAG_trace_alloc) { va_list arguments; va_start(arguments, msg); OS::VPrint(msg, arguments); va_end(arguments); } } bool LAllocator::HasTaggedValue(int virtual_register) const { HValue* value = graph_->LookupValue(virtual_register); if (value == NULL) return false; return value->representation().IsTagged(); } RegisterKind LAllocator::RequiredRegisterKind(int virtual_register) const { if (virtual_register < first_artificial_register_) { HValue* value = graph_->LookupValue(virtual_register); if (value != NULL && value->representation().IsDouble()) { return DOUBLE_REGISTERS; } } else if (double_artificial_registers_.Contains( virtual_register - first_artificial_register_)) { return DOUBLE_REGISTERS; } return GENERAL_REGISTERS; } void LAllocator::RecordDefinition(HInstruction* instr, LUnallocated* operand) { operand->set_virtual_register(instr->id()); } void LAllocator::RecordTemporary(LUnallocated* operand) { ASSERT(next_virtual_register_ < LUnallocated::kMaxVirtualRegisters); if (!operand->HasFixedPolicy()) { operand->set_virtual_register(next_virtual_register_++); } } void LAllocator::RecordUse(HValue* value, LUnallocated* operand) { operand->set_virtual_register(value->id()); } int LAllocator::max_initial_value_ids() { return LUnallocated::kMaxVirtualRegisters / 32; } void LAllocator::AddToActive(LiveRange* range) { TraceAlloc("Add live range %d to active\n", range->id()); active_live_ranges_.Add(range); } void LAllocator::AddToInactive(LiveRange* range) { TraceAlloc("Add live range %d to inactive\n", range->id()); inactive_live_ranges_.Add(range); } void LAllocator::AddToUnhandledSorted(LiveRange* range) { if (range == NULL || range->IsEmpty()) return; ASSERT(!range->HasRegisterAssigned() && !range->IsSpilled()); 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); ASSERT(UnhandledIsSorted()); return; } } TraceAlloc("Add live range %d to unhandled at start\n", range->id()); unhandled_live_ranges_.InsertAt(0, range); ASSERT(UnhandledIsSorted()); } void LAllocator::AddToUnhandledUnsorted(LiveRange* range) { if (range == NULL || range->IsEmpty()) return; ASSERT(!range->HasRegisterAssigned() && !range->IsSpilled()); TraceAlloc("Add live range %d to unhandled unsorted at end\n", range->id()); unhandled_live_ranges_.Add(range); } static int UnhandledSortHelper(LiveRange* const* a, LiveRange* const* b) { ASSERT(!(*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 LAllocator::SortUnhandled() { TraceAlloc("Sort unhandled\n"); unhandled_live_ranges_.Sort(&UnhandledSortHelper); } bool LAllocator::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 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); } } 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) { ASSERT(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 LAllocator::ActiveToInactive(LiveRange* range) { ASSERT(active_live_ranges_.Contains(range)); active_live_ranges_.RemoveElement(range); inactive_live_ranges_.Add(range); TraceAlloc("Moving live range %d from active to inactive\n", range->id()); } void LAllocator::InactiveToHandled(LiveRange* range) { ASSERT(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 LAllocator::InactiveToActive(LiveRange* range) { ASSERT(inactive_live_ranges_.Contains(range)); inactive_live_ranges_.RemoveElement(range); active_live_ranges_.Add(range); TraceAlloc("Moving live range %d from inactive to active\n", range->id()); } // TryAllocateFreeReg and AllocateBlockedReg assume this // when allocating local arrays. STATIC_ASSERT(DoubleRegister::kNumAllocatableRegisters >= Register::kNumAllocatableRegisters); bool LAllocator::TryAllocateFreeReg(LiveRange* current) { LifetimePosition free_until_pos[DoubleRegister::kNumAllocatableRegisters]; for (int i = 0; i < DoubleRegister::kNumAllocatableRegisters; 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); ASSERT(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); } UsePosition* hinted_use = current->FirstPosWithHint(); if (hinted_use != NULL) { LOperand* hint = hinted_use->hint(); if (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()); current->set_assigned_register(register_index, mode_); 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 = SplitAt(current, pos); AddToUnhandledSorted(tail); } // Register reg is available at the range start and is free until // the range end. ASSERT(pos.Value() >= current->End().Value()); TraceAlloc("Assigning free reg %s to live range %d\n", RegisterName(reg), current->id()); current->set_assigned_register(reg, mode_); return true; } void LAllocator::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::kNumAllocatableRegisters]; LifetimePosition block_pos[DoubleRegister::kNumAllocatableRegisters]; for (int i = 0; i < DoubleRegister::kNumAllocatableRegisters; 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); ASSERT(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. // // Corner case: the first use position is equal to the start of the range. // In this case we have nothing to spill and SpillBetween will just return // this range to the list of unhandled ones. This will lead to the infinite // loop. ASSERT(current->Start().Value() < register_use->pos().Value()); 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()); AddToUnhandledSorted(tail); } // Register reg is not blocked for the whole range. ASSERT(block_pos[reg].Value() >= current->End().Value()); TraceAlloc("Assigning blocked reg %s to live range %d\n", RegisterName(reg), current->id()); current->set_assigned_register(reg, mode_); // 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); } void LAllocator::SplitAndSpillIntersecting(LiveRange* current) { ASSERT(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()); if (next_pos == NULL) { SpillAfter(range, split_pos); } else { SpillBetween(range, split_pos, next_pos->pos()); } ActiveToHandled(range); --i; } } for (int i = 0; i < inactive_live_ranges_.length(); ++i) { LiveRange* range = inactive_live_ranges_[i]; ASSERT(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); } InactiveToHandled(range); --i; } } } } bool LAllocator::IsBlockBoundary(LifetimePosition pos) { return pos.IsInstructionStart() && InstructionAt(pos.InstructionIndex())->IsLabel(); } LiveRange* LAllocator::SplitAt(LiveRange* range, LifetimePosition pos) { ASSERT(!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. ASSERT(pos.IsInstructionStart() || !chunk_->instructions()->at(pos.InstructionIndex())->IsControl()); LiveRange* result = LiveRangeFor(next_virtual_register_++); range->SplitAt(pos, result); return result; } LiveRange* LAllocator::SplitBetween(LiveRange* range, LifetimePosition start, LifetimePosition end) { ASSERT(!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); ASSERT(split_pos.Value() >= start.Value()); return SplitAt(range, split_pos); } LifetimePosition LAllocator::FindOptimalSplitPos(LifetimePosition start, LifetimePosition end) { int start_instr = start.InstructionIndex(); int end_instr = end.InstructionIndex(); ASSERT(start_instr <= end_instr); // We have no choice if (start_instr == end_instr) return end; HBasicBlock* start_block = GetBlock(start); HBasicBlock* 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; } HBasicBlock* block = end_block; // Find header of outermost loop. while (block->parent_loop_header() != NULL && block->parent_loop_header()->block_id() > start_block->block_id()) { block = block->parent_loop_header(); } // 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 LAllocator::SpillAfter(LiveRange* range, LifetimePosition pos) { LiveRange* second_part = SplitAt(range, pos); Spill(second_part); } void LAllocator::SpillBetween(LiveRange* range, LifetimePosition start, LifetimePosition end) { ASSERT(start.Value() < end.Value()); LiveRange* second_part = SplitAt(range, start); 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, second_part->Start().InstructionEnd(), end.PrevInstruction().InstructionEnd()); ASSERT(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 LAllocator::Spill(LiveRange* range) { ASSERT(!range->IsSpilled()); TraceAlloc("Spilling live range %d\n", range->id()); LiveRange* first = range->TopLevel(); if (!first->HasAllocatedSpillOperand()) { LOperand* op = TryReuseSpillSlot(range); if (op == NULL) op = chunk_->GetNextSpillSlot(mode_ == DOUBLE_REGISTERS); first->SetSpillOperand(op); } range->MakeSpilled(); } int LAllocator::RegisterCount() const { return num_registers_; } #ifdef DEBUG void LAllocator::Verify() const { for (int i = 0; i < live_ranges()->length(); ++i) { LiveRange* current = live_ranges()->at(i); if (current != NULL) current->Verify(); } } #endif } } // namespace v8::internal