| // Copyright 2016 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/memory-optimizer.h" |
| |
| #include "src/compiler/js-graph.h" |
| #include "src/compiler/linkage.h" |
| #include "src/compiler/node-matchers.h" |
| #include "src/compiler/node-properties.h" |
| #include "src/compiler/node.h" |
| #include "src/compiler/simplified-operator.h" |
| |
| namespace v8 { |
| namespace internal { |
| namespace compiler { |
| |
| MemoryOptimizer::MemoryOptimizer(JSGraph* jsgraph, Zone* zone) |
| : jsgraph_(jsgraph), |
| empty_state_(AllocationState::Empty(zone)), |
| pending_(zone), |
| tokens_(zone), |
| zone_(zone) {} |
| |
| void MemoryOptimizer::Optimize() { |
| EnqueueUses(graph()->start(), empty_state()); |
| while (!tokens_.empty()) { |
| Token const token = tokens_.front(); |
| tokens_.pop(); |
| VisitNode(token.node, token.state); |
| } |
| DCHECK(pending_.empty()); |
| DCHECK(tokens_.empty()); |
| } |
| |
| MemoryOptimizer::AllocationGroup::AllocationGroup(Node* node, |
| PretenureFlag pretenure, |
| Zone* zone) |
| : node_ids_(zone), pretenure_(pretenure), size_(nullptr) { |
| node_ids_.insert(node->id()); |
| } |
| |
| MemoryOptimizer::AllocationGroup::AllocationGroup(Node* node, |
| PretenureFlag pretenure, |
| Node* size, Zone* zone) |
| : node_ids_(zone), pretenure_(pretenure), size_(size) { |
| node_ids_.insert(node->id()); |
| } |
| |
| void MemoryOptimizer::AllocationGroup::Add(Node* node) { |
| node_ids_.insert(node->id()); |
| } |
| |
| bool MemoryOptimizer::AllocationGroup::Contains(Node* node) const { |
| return node_ids_.find(node->id()) != node_ids_.end(); |
| } |
| |
| MemoryOptimizer::AllocationState::AllocationState() |
| : group_(nullptr), size_(std::numeric_limits<int>::max()), top_(nullptr) {} |
| |
| MemoryOptimizer::AllocationState::AllocationState(AllocationGroup* group) |
| : group_(group), size_(std::numeric_limits<int>::max()), top_(nullptr) {} |
| |
| MemoryOptimizer::AllocationState::AllocationState(AllocationGroup* group, |
| int size, Node* top) |
| : group_(group), size_(size), top_(top) {} |
| |
| bool MemoryOptimizer::AllocationState::IsNewSpaceAllocation() const { |
| return group() && group()->IsNewSpaceAllocation(); |
| } |
| |
| void MemoryOptimizer::VisitNode(Node* node, AllocationState const* state) { |
| DCHECK(!node->IsDead()); |
| DCHECK_LT(0, node->op()->EffectInputCount()); |
| switch (node->opcode()) { |
| case IrOpcode::kAllocate: |
| return VisitAllocate(node, state); |
| case IrOpcode::kCall: |
| return VisitCall(node, state); |
| case IrOpcode::kLoadElement: |
| return VisitLoadElement(node, state); |
| case IrOpcode::kLoadField: |
| return VisitLoadField(node, state); |
| case IrOpcode::kStoreElement: |
| return VisitStoreElement(node, state); |
| case IrOpcode::kStoreField: |
| return VisitStoreField(node, state); |
| case IrOpcode::kCheckedLoad: |
| case IrOpcode::kCheckedStore: |
| case IrOpcode::kDeoptimizeIf: |
| case IrOpcode::kDeoptimizeUnless: |
| case IrOpcode::kIfException: |
| case IrOpcode::kLoad: |
| case IrOpcode::kStore: |
| return VisitOtherEffect(node, state); |
| default: |
| break; |
| } |
| DCHECK_EQ(0, node->op()->EffectOutputCount()); |
| } |
| |
| void MemoryOptimizer::VisitAllocate(Node* node, AllocationState const* state) { |
| DCHECK_EQ(IrOpcode::kAllocate, node->opcode()); |
| Node* value; |
| Node* size = node->InputAt(0); |
| Node* effect = node->InputAt(1); |
| Node* control = node->InputAt(2); |
| PretenureFlag pretenure = OpParameter<PretenureFlag>(node->op()); |
| |
| // Determine the top/limit addresses. |
| Node* top_address = jsgraph()->ExternalConstant( |
| pretenure == NOT_TENURED |
| ? ExternalReference::new_space_allocation_top_address(isolate()) |
| : ExternalReference::old_space_allocation_top_address(isolate())); |
| Node* limit_address = jsgraph()->ExternalConstant( |
| pretenure == NOT_TENURED |
| ? ExternalReference::new_space_allocation_limit_address(isolate()) |
| : ExternalReference::old_space_allocation_limit_address(isolate())); |
| |
| // Check if we can fold this allocation into a previous allocation represented |
| // by the incoming {state}. |
| Int32Matcher m(size); |
| if (m.HasValue() && m.Value() < Page::kMaxRegularHeapObjectSize) { |
| int32_t const object_size = m.Value(); |
| if (state->size() <= Page::kMaxRegularHeapObjectSize - object_size && |
| state->group()->pretenure() == pretenure) { |
| // We can fold this Allocate {node} into the allocation {group} |
| // represented by the given {state}. Compute the upper bound for |
| // the new {state}. |
| int32_t const state_size = state->size() + object_size; |
| |
| // Update the reservation check to the actual maximum upper bound. |
| AllocationGroup* const group = state->group(); |
| if (OpParameter<int32_t>(group->size()) < state_size) { |
| NodeProperties::ChangeOp(group->size(), |
| common()->Int32Constant(state_size)); |
| } |
| |
| // Update the allocation top with the new object allocation. |
| // TODO(bmeurer): Defer writing back top as much as possible. |
| Node* top = graph()->NewNode(machine()->IntAdd(), state->top(), |
| jsgraph()->IntPtrConstant(object_size)); |
| effect = graph()->NewNode( |
| machine()->Store(StoreRepresentation( |
| MachineType::PointerRepresentation(), kNoWriteBarrier)), |
| top_address, jsgraph()->IntPtrConstant(0), top, effect, control); |
| |
| // Compute the effective inner allocated address. |
| value = graph()->NewNode( |
| machine()->BitcastWordToTagged(), |
| graph()->NewNode(machine()->IntAdd(), state->top(), |
| jsgraph()->IntPtrConstant(kHeapObjectTag))); |
| |
| // Extend the allocation {group}. |
| group->Add(value); |
| state = AllocationState::Open(group, state_size, top, zone()); |
| } else { |
| // Setup a mutable reservation size node; will be patched as we fold |
| // additional allocations into this new group. |
| Node* size = graph()->NewNode(common()->Int32Constant(object_size)); |
| |
| // Load allocation top and limit. |
| Node* top = effect = |
| graph()->NewNode(machine()->Load(MachineType::Pointer()), top_address, |
| jsgraph()->IntPtrConstant(0), effect, control); |
| Node* limit = effect = graph()->NewNode( |
| machine()->Load(MachineType::Pointer()), limit_address, |
| jsgraph()->IntPtrConstant(0), effect, control); |
| |
| // Check if we need to collect garbage before we can start bump pointer |
| // allocation (always done for folded allocations). |
| Node* check = graph()->NewNode( |
| machine()->UintLessThan(), |
| graph()->NewNode( |
| machine()->IntAdd(), top, |
| machine()->Is64() |
| ? graph()->NewNode(machine()->ChangeInt32ToInt64(), size) |
| : size), |
| limit); |
| Node* branch = |
| graph()->NewNode(common()->Branch(BranchHint::kTrue), check, control); |
| |
| Node* if_true = graph()->NewNode(common()->IfTrue(), branch); |
| Node* etrue = effect; |
| Node* vtrue = top; |
| |
| Node* if_false = graph()->NewNode(common()->IfFalse(), branch); |
| Node* efalse = effect; |
| Node* vfalse; |
| { |
| Node* target = pretenure == NOT_TENURED |
| ? jsgraph()->AllocateInNewSpaceStubConstant() |
| : jsgraph()->AllocateInOldSpaceStubConstant(); |
| if (!allocate_operator_.is_set()) { |
| CallDescriptor* descriptor = |
| Linkage::GetAllocateCallDescriptor(graph()->zone()); |
| allocate_operator_.set(common()->Call(descriptor)); |
| } |
| vfalse = efalse = graph()->NewNode(allocate_operator_.get(), target, |
| size, efalse, if_false); |
| vfalse = graph()->NewNode(machine()->IntSub(), vfalse, |
| jsgraph()->IntPtrConstant(kHeapObjectTag)); |
| } |
| |
| control = graph()->NewNode(common()->Merge(2), if_true, if_false); |
| effect = graph()->NewNode(common()->EffectPhi(2), etrue, efalse, control); |
| value = graph()->NewNode( |
| common()->Phi(MachineType::PointerRepresentation(), 2), vtrue, vfalse, |
| control); |
| |
| // Compute the new top and write it back. |
| top = graph()->NewNode(machine()->IntAdd(), value, |
| jsgraph()->IntPtrConstant(object_size)); |
| effect = graph()->NewNode( |
| machine()->Store(StoreRepresentation( |
| MachineType::PointerRepresentation(), kNoWriteBarrier)), |
| top_address, jsgraph()->IntPtrConstant(0), top, effect, control); |
| |
| // Compute the initial object address. |
| value = graph()->NewNode( |
| machine()->BitcastWordToTagged(), |
| graph()->NewNode(machine()->IntAdd(), value, |
| jsgraph()->IntPtrConstant(kHeapObjectTag))); |
| |
| // Start a new allocation group. |
| AllocationGroup* group = |
| new (zone()) AllocationGroup(value, pretenure, size, zone()); |
| state = AllocationState::Open(group, object_size, top, zone()); |
| } |
| } else { |
| // Load allocation top and limit. |
| Node* top = effect = |
| graph()->NewNode(machine()->Load(MachineType::Pointer()), top_address, |
| jsgraph()->IntPtrConstant(0), effect, control); |
| Node* limit = effect = |
| graph()->NewNode(machine()->Load(MachineType::Pointer()), limit_address, |
| jsgraph()->IntPtrConstant(0), effect, control); |
| |
| // Compute the new top. |
| Node* new_top = graph()->NewNode( |
| machine()->IntAdd(), top, |
| machine()->Is64() |
| ? graph()->NewNode(machine()->ChangeInt32ToInt64(), size) |
| : size); |
| |
| // Check if we can do bump pointer allocation here. |
| Node* check = graph()->NewNode(machine()->UintLessThan(), new_top, limit); |
| Node* branch = |
| graph()->NewNode(common()->Branch(BranchHint::kTrue), check, control); |
| |
| Node* if_true = graph()->NewNode(common()->IfTrue(), branch); |
| Node* etrue = effect; |
| Node* vtrue; |
| { |
| etrue = graph()->NewNode( |
| machine()->Store(StoreRepresentation( |
| MachineType::PointerRepresentation(), kNoWriteBarrier)), |
| top_address, jsgraph()->IntPtrConstant(0), new_top, etrue, if_true); |
| vtrue = graph()->NewNode( |
| machine()->BitcastWordToTagged(), |
| graph()->NewNode(machine()->IntAdd(), top, |
| jsgraph()->IntPtrConstant(kHeapObjectTag))); |
| } |
| |
| Node* if_false = graph()->NewNode(common()->IfFalse(), branch); |
| Node* efalse = effect; |
| Node* vfalse; |
| { |
| Node* target = pretenure == NOT_TENURED |
| ? jsgraph()->AllocateInNewSpaceStubConstant() |
| : jsgraph()->AllocateInOldSpaceStubConstant(); |
| if (!allocate_operator_.is_set()) { |
| CallDescriptor* descriptor = |
| Linkage::GetAllocateCallDescriptor(graph()->zone()); |
| allocate_operator_.set(common()->Call(descriptor)); |
| } |
| vfalse = efalse = graph()->NewNode(allocate_operator_.get(), target, size, |
| efalse, if_false); |
| } |
| |
| control = graph()->NewNode(common()->Merge(2), if_true, if_false); |
| effect = graph()->NewNode(common()->EffectPhi(2), etrue, efalse, control); |
| value = graph()->NewNode(common()->Phi(MachineRepresentation::kTagged, 2), |
| vtrue, vfalse, control); |
| |
| // Create an unfoldable allocation group. |
| AllocationGroup* group = |
| new (zone()) AllocationGroup(value, pretenure, zone()); |
| state = AllocationState::Closed(group, zone()); |
| } |
| |
| // Replace all effect uses of {node} with the {effect}, enqueue the |
| // effect uses for further processing, and replace all value uses of |
| // {node} with the {value}. |
| for (Edge edge : node->use_edges()) { |
| if (NodeProperties::IsEffectEdge(edge)) { |
| EnqueueUse(edge.from(), edge.index(), state); |
| edge.UpdateTo(effect); |
| } else { |
| DCHECK(NodeProperties::IsValueEdge(edge)); |
| edge.UpdateTo(value); |
| } |
| } |
| |
| // Kill the {node} to make sure we don't leave dangling dead uses. |
| node->Kill(); |
| } |
| |
| void MemoryOptimizer::VisitCall(Node* node, AllocationState const* state) { |
| DCHECK_EQ(IrOpcode::kCall, node->opcode()); |
| // If the call can allocate, we start with a fresh state. |
| if (!(CallDescriptorOf(node->op())->flags() & CallDescriptor::kNoAllocate)) { |
| state = empty_state(); |
| } |
| EnqueueUses(node, state); |
| } |
| |
| void MemoryOptimizer::VisitLoadElement(Node* node, |
| AllocationState const* state) { |
| DCHECK_EQ(IrOpcode::kLoadElement, node->opcode()); |
| ElementAccess const& access = ElementAccessOf(node->op()); |
| Node* index = node->InputAt(1); |
| node->ReplaceInput(1, ComputeIndex(access, index)); |
| NodeProperties::ChangeOp(node, machine()->Load(access.machine_type)); |
| EnqueueUses(node, state); |
| } |
| |
| void MemoryOptimizer::VisitLoadField(Node* node, AllocationState const* state) { |
| DCHECK_EQ(IrOpcode::kLoadField, node->opcode()); |
| FieldAccess const& access = FieldAccessOf(node->op()); |
| Node* offset = jsgraph()->IntPtrConstant(access.offset - access.tag()); |
| node->InsertInput(graph()->zone(), 1, offset); |
| NodeProperties::ChangeOp(node, machine()->Load(access.machine_type)); |
| EnqueueUses(node, state); |
| } |
| |
| void MemoryOptimizer::VisitStoreElement(Node* node, |
| AllocationState const* state) { |
| DCHECK_EQ(IrOpcode::kStoreElement, node->opcode()); |
| ElementAccess const& access = ElementAccessOf(node->op()); |
| Node* object = node->InputAt(0); |
| Node* index = node->InputAt(1); |
| WriteBarrierKind write_barrier_kind = |
| ComputeWriteBarrierKind(object, state, access.write_barrier_kind); |
| node->ReplaceInput(1, ComputeIndex(access, index)); |
| NodeProperties::ChangeOp( |
| node, machine()->Store(StoreRepresentation( |
| access.machine_type.representation(), write_barrier_kind))); |
| EnqueueUses(node, state); |
| } |
| |
| void MemoryOptimizer::VisitStoreField(Node* node, |
| AllocationState const* state) { |
| DCHECK_EQ(IrOpcode::kStoreField, node->opcode()); |
| FieldAccess const& access = FieldAccessOf(node->op()); |
| Node* object = node->InputAt(0); |
| WriteBarrierKind write_barrier_kind = |
| ComputeWriteBarrierKind(object, state, access.write_barrier_kind); |
| Node* offset = jsgraph()->IntPtrConstant(access.offset - access.tag()); |
| node->InsertInput(graph()->zone(), 1, offset); |
| NodeProperties::ChangeOp( |
| node, machine()->Store(StoreRepresentation( |
| access.machine_type.representation(), write_barrier_kind))); |
| EnqueueUses(node, state); |
| } |
| |
| void MemoryOptimizer::VisitOtherEffect(Node* node, |
| AllocationState const* state) { |
| EnqueueUses(node, state); |
| } |
| |
| Node* MemoryOptimizer::ComputeIndex(ElementAccess const& access, Node* key) { |
| Node* index = key; |
| int element_size_shift = |
| ElementSizeLog2Of(access.machine_type.representation()); |
| if (element_size_shift) { |
| index = graph()->NewNode(machine()->Word32Shl(), index, |
| jsgraph()->Int32Constant(element_size_shift)); |
| } |
| const int fixed_offset = access.header_size - access.tag(); |
| if (fixed_offset) { |
| index = graph()->NewNode(machine()->Int32Add(), index, |
| jsgraph()->Int32Constant(fixed_offset)); |
| } |
| if (machine()->Is64()) { |
| // TODO(turbofan): This is probably only correct for typed arrays, and only |
| // if the typed arrays are at most 2GiB in size, which happens to match |
| // exactly our current situation. |
| index = graph()->NewNode(machine()->ChangeUint32ToUint64(), index); |
| } |
| return index; |
| } |
| |
| WriteBarrierKind MemoryOptimizer::ComputeWriteBarrierKind( |
| Node* object, AllocationState const* state, |
| WriteBarrierKind write_barrier_kind) { |
| if (state->IsNewSpaceAllocation() && state->group()->Contains(object)) { |
| write_barrier_kind = kNoWriteBarrier; |
| } |
| return write_barrier_kind; |
| } |
| |
| MemoryOptimizer::AllocationState const* MemoryOptimizer::MergeStates( |
| AllocationStates const& states) { |
| // Check if all states are the same; or at least if all allocation |
| // states belong to the same allocation group. |
| AllocationState const* state = states.front(); |
| AllocationGroup* group = state->group(); |
| for (size_t i = 1; i < states.size(); ++i) { |
| if (states[i] != state) state = nullptr; |
| if (states[i]->group() != group) group = nullptr; |
| } |
| if (state == nullptr) { |
| if (group != nullptr) { |
| // We cannot fold any more allocations into this group, but we can still |
| // eliminate write barriers on stores to this group. |
| // TODO(bmeurer): We could potentially just create a Phi here to merge |
| // the various tops; but we need to pay special attention not to create |
| // an unschedulable graph. |
| state = AllocationState::Closed(group, zone()); |
| } else { |
| // The states are from different allocation groups. |
| state = empty_state(); |
| } |
| } |
| return state; |
| } |
| |
| void MemoryOptimizer::EnqueueMerge(Node* node, int index, |
| AllocationState const* state) { |
| DCHECK_EQ(IrOpcode::kEffectPhi, node->opcode()); |
| int const input_count = node->InputCount() - 1; |
| DCHECK_LT(0, input_count); |
| Node* const control = node->InputAt(input_count); |
| if (control->opcode() == IrOpcode::kLoop) { |
| // For loops we always start with an empty state at the beginning. |
| if (index == 0) EnqueueUses(node, empty_state()); |
| } else { |
| DCHECK_EQ(IrOpcode::kMerge, control->opcode()); |
| // Check if we already know about this pending merge. |
| NodeId const id = node->id(); |
| auto it = pending_.find(id); |
| if (it == pending_.end()) { |
| // Insert a new pending merge. |
| it = pending_.insert(std::make_pair(id, AllocationStates(zone()))).first; |
| } |
| // Add the next input state. |
| it->second.push_back(state); |
| // Check if states for all inputs are available by now. |
| if (it->second.size() == static_cast<size_t>(input_count)) { |
| // All inputs to this effect merge are done, merge the states given all |
| // input constraints, drop the pending merge and enqueue uses of the |
| // EffectPhi {node}. |
| state = MergeStates(it->second); |
| EnqueueUses(node, state); |
| pending_.erase(it); |
| } |
| } |
| } |
| |
| void MemoryOptimizer::EnqueueUses(Node* node, AllocationState const* state) { |
| for (Edge const edge : node->use_edges()) { |
| if (NodeProperties::IsEffectEdge(edge)) { |
| EnqueueUse(edge.from(), edge.index(), state); |
| } |
| } |
| } |
| |
| void MemoryOptimizer::EnqueueUse(Node* node, int index, |
| AllocationState const* state) { |
| if (node->opcode() == IrOpcode::kEffectPhi) { |
| // An EffectPhi represents a merge of different effect chains, which |
| // needs special handling depending on whether the merge is part of a |
| // loop or just a normal control join. |
| EnqueueMerge(node, index, state); |
| } else { |
| Token token = {node, state}; |
| tokens_.push(token); |
| } |
| } |
| |
| Graph* MemoryOptimizer::graph() const { return jsgraph()->graph(); } |
| |
| Isolate* MemoryOptimizer::isolate() const { return jsgraph()->isolate(); } |
| |
| CommonOperatorBuilder* MemoryOptimizer::common() const { |
| return jsgraph()->common(); |
| } |
| |
| MachineOperatorBuilder* MemoryOptimizer::machine() const { |
| return jsgraph()->machine(); |
| } |
| |
| } // namespace compiler |
| } // namespace internal |
| } // namespace v8 |