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// 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/codegen/interface-descriptors.h"
#include "src/codegen/tick-counter.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/roots/roots-inl.h"
namespace v8 {
namespace internal {
namespace compiler {
namespace {
bool CanAllocate(const Node* node) {
switch (node->opcode()) {
case IrOpcode::kAbortCSAAssert:
case IrOpcode::kBitcastTaggedToWord:
case IrOpcode::kBitcastWordToTagged:
case IrOpcode::kComment:
case IrOpcode::kDebugBreak:
case IrOpcode::kDeoptimizeIf:
case IrOpcode::kDeoptimizeUnless:
case IrOpcode::kEffectPhi:
case IrOpcode::kIfException:
case IrOpcode::kLoad:
case IrOpcode::kLoadElement:
case IrOpcode::kLoadField:
case IrOpcode::kLoadFromObject:
case IrOpcode::kPoisonedLoad:
case IrOpcode::kProtectedLoad:
case IrOpcode::kProtectedStore:
case IrOpcode::kRetain:
case IrOpcode::kStackPointerGreaterThan:
case IrOpcode::kStaticAssert:
// TODO(tebbi): Store nodes might do a bump-pointer allocation.
// We should introduce a special bump-pointer store node to
// differentiate that.
case IrOpcode::kStore:
case IrOpcode::kStoreElement:
case IrOpcode::kStoreField:
case IrOpcode::kStoreToObject:
case IrOpcode::kTaggedPoisonOnSpeculation:
case IrOpcode::kUnalignedLoad:
case IrOpcode::kUnalignedStore:
case IrOpcode::kUnreachable:
case IrOpcode::kUnsafePointerAdd:
case IrOpcode::kWord32AtomicAdd:
case IrOpcode::kWord32AtomicAnd:
case IrOpcode::kWord32AtomicCompareExchange:
case IrOpcode::kWord32AtomicExchange:
case IrOpcode::kWord32AtomicLoad:
case IrOpcode::kWord32AtomicOr:
case IrOpcode::kWord32AtomicPairAdd:
case IrOpcode::kWord32AtomicPairAnd:
case IrOpcode::kWord32AtomicPairCompareExchange:
case IrOpcode::kWord32AtomicPairExchange:
case IrOpcode::kWord32AtomicPairLoad:
case IrOpcode::kWord32AtomicPairOr:
case IrOpcode::kWord32AtomicPairStore:
case IrOpcode::kWord32AtomicPairSub:
case IrOpcode::kWord32AtomicPairXor:
case IrOpcode::kWord32AtomicStore:
case IrOpcode::kWord32AtomicSub:
case IrOpcode::kWord32AtomicXor:
case IrOpcode::kWord32PoisonOnSpeculation:
case IrOpcode::kWord64AtomicAdd:
case IrOpcode::kWord64AtomicAnd:
case IrOpcode::kWord64AtomicCompareExchange:
case IrOpcode::kWord64AtomicExchange:
case IrOpcode::kWord64AtomicLoad:
case IrOpcode::kWord64AtomicOr:
case IrOpcode::kWord64AtomicStore:
case IrOpcode::kWord64AtomicSub:
case IrOpcode::kWord64AtomicXor:
case IrOpcode::kWord64PoisonOnSpeculation:
return false;
case IrOpcode::kCall:
return !(CallDescriptorOf(node->op())->flags() &
CallDescriptor::kNoAllocate);
default:
break;
}
return true;
}
Node* SearchAllocatingNode(Node* start, Node* limit, Zone* temp_zone) {
ZoneQueue<Node*> queue(temp_zone);
ZoneSet<Node*> visited(temp_zone);
visited.insert(limit);
queue.push(start);
while (!queue.empty()) {
Node* const current = queue.front();
queue.pop();
if (visited.find(current) == visited.end()) {
visited.insert(current);
if (CanAllocate(current)) {
return current;
}
for (int i = 0; i < current->op()->EffectInputCount(); ++i) {
queue.push(NodeProperties::GetEffectInput(current, i));
}
}
}
return nullptr;
}
bool CanLoopAllocate(Node* loop_effect_phi, Zone* temp_zone) {
Node* const control = NodeProperties::GetControlInput(loop_effect_phi);
// Start the effect chain walk from the loop back edges.
for (int i = 1; i < control->InputCount(); ++i) {
if (SearchAllocatingNode(loop_effect_phi->InputAt(i), loop_effect_phi,
temp_zone) != nullptr) {
return true;
}
}
return false;
}
Node* EffectPhiForPhi(Node* phi) {
Node* control = NodeProperties::GetControlInput(phi);
for (Node* use : control->uses()) {
if (use->opcode() == IrOpcode::kEffectPhi) {
return use;
}
}
return nullptr;
}
void WriteBarrierAssertFailed(Node* node, Node* object, const char* name,
Zone* temp_zone) {
std::stringstream str;
str << "MemoryOptimizer could not remove write barrier for node #"
<< node->id() << "\n";
str << " Run mksnapshot with --csa-trap-on-node=" << name << ","
<< node->id() << " to break in CSA code.\n";
Node* object_position = object;
if (object_position->opcode() == IrOpcode::kPhi) {
object_position = EffectPhiForPhi(object_position);
}
Node* allocating_node = nullptr;
if (object_position && object_position->op()->EffectOutputCount() > 0) {
allocating_node = SearchAllocatingNode(node, object_position, temp_zone);
}
if (allocating_node) {
str << "\n There is a potentially allocating node in between:\n";
str << " " << *allocating_node << "\n";
str << " Run mksnapshot with --csa-trap-on-node=" << name << ","
<< allocating_node->id() << " to break there.\n";
if (allocating_node->opcode() == IrOpcode::kCall) {
str << " If this is a never-allocating runtime call, you can add an "
"exception to Runtime::MayAllocate.\n";
}
} else {
str << "\n It seems the store happened to something different than a "
"direct "
"allocation:\n";
str << " " << *object << "\n";
str << " Run mksnapshot with --csa-trap-on-node=" << name << ","
<< object->id() << " to break there.\n";
}
FATAL("%s", str.str().c_str());
}
} // namespace
MemoryOptimizer::MemoryOptimizer(
JSGraph* jsgraph, Zone* zone, PoisoningMitigationLevel poisoning_level,
MemoryLowering::AllocationFolding allocation_folding,
const char* function_debug_name, TickCounter* tick_counter)
: graph_assembler_(jsgraph, zone),
memory_lowering_(jsgraph, zone, &graph_assembler_, poisoning_level,
allocation_folding, WriteBarrierAssertFailed,
function_debug_name),
jsgraph_(jsgraph),
empty_state_(AllocationState::Empty(zone)),
pending_(zone),
tokens_(zone),
zone_(zone),
tick_counter_(tick_counter) {}
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());
}
void MemoryOptimizer::VisitNode(Node* node, AllocationState const* state) {
tick_counter_->DoTick();
DCHECK(!node->IsDead());
DCHECK_LT(0, node->op()->EffectInputCount());
switch (node->opcode()) {
case IrOpcode::kAllocate:
// Allocate nodes were purged from the graph in effect-control
// linearization.
UNREACHABLE();
case IrOpcode::kAllocateRaw:
return VisitAllocateRaw(node, state);
case IrOpcode::kCall:
return VisitCall(node, state);
case IrOpcode::kLoadFromObject:
return VisitLoadFromObject(node, state);
case IrOpcode::kLoadElement:
return VisitLoadElement(node, state);
case IrOpcode::kLoadField:
return VisitLoadField(node, state);
case IrOpcode::kStoreToObject:
return VisitStoreToObject(node, state);
case IrOpcode::kStoreElement:
return VisitStoreElement(node, state);
case IrOpcode::kStoreField:
return VisitStoreField(node, state);
case IrOpcode::kStore:
return VisitStore(node, state);
default:
if (!CanAllocate(node)) {
// These operations cannot trigger GC.
return VisitOtherEffect(node, state);
}
}
DCHECK_EQ(0, node->op()->EffectOutputCount());
}
bool MemoryOptimizer::AllocationTypeNeedsUpdateToOld(Node* const node,
const Edge edge) {
// Test to see if we need to update the AllocationType.
if (node->opcode() == IrOpcode::kStoreField && edge.index() == 1) {
Node* parent = node->InputAt(0);
if (parent->opcode() == IrOpcode::kAllocateRaw &&
AllocationTypeOf(parent->op()) == AllocationType::kOld) {
return true;
}
}
return false;
}
void MemoryOptimizer::VisitAllocateRaw(Node* node,
AllocationState const* state) {
DCHECK_EQ(IrOpcode::kAllocateRaw, node->opcode());
const AllocateParameters& allocation = AllocateParametersOf(node->op());
AllocationType allocation_type = allocation.allocation_type();
// Propagate tenuring from outer allocations to inner allocations, i.e.
// when we allocate an object in old space and store a newly allocated
// child object into the pretenured object, then the newly allocated
// child object also should get pretenured to old space.
if (allocation_type == AllocationType::kOld) {
for (Edge const edge : node->use_edges()) {
Node* const user = edge.from();
if (user->opcode() == IrOpcode::kStoreField && edge.index() == 0) {
Node* child = user->InputAt(1);
if (child->opcode() == IrOpcode::kAllocateRaw &&
AllocationTypeOf(child->op()) == AllocationType::kYoung) {
NodeProperties::ChangeOp(child, node->op());
break;
}
}
}
} else {
DCHECK_EQ(AllocationType::kYoung, allocation_type);
for (Edge const edge : node->use_edges()) {
Node* const user = edge.from();
if (AllocationTypeNeedsUpdateToOld(user, edge)) {
allocation_type = AllocationType::kOld;
break;
}
}
}
Reduction reduction = memory_lowering()->ReduceAllocateRaw(
node, allocation_type, allocation.allow_large_objects(), &state);
CHECK(reduction.Changed() && reduction.replacement() != node);
// Replace all uses of node and kill the node to make sure we don't leave
// dangling dead uses.
NodeProperties::ReplaceUses(node, reduction.replacement(),
graph_assembler_.effect(),
graph_assembler_.control());
node->Kill();
EnqueueUses(state->effect(), state);
}
void MemoryOptimizer::VisitLoadFromObject(Node* node,
AllocationState const* state) {
DCHECK_EQ(IrOpcode::kLoadFromObject, node->opcode());
memory_lowering()->ReduceLoadFromObject(node);
EnqueueUses(node, state);
}
void MemoryOptimizer::VisitStoreToObject(Node* node,
AllocationState const* state) {
DCHECK_EQ(IrOpcode::kStoreToObject, node->opcode());
memory_lowering()->ReduceStoreToObject(node, state);
EnqueueUses(node, state);
}
void MemoryOptimizer::VisitLoadElement(Node* node,
AllocationState const* state) {
DCHECK_EQ(IrOpcode::kLoadElement, node->opcode());
memory_lowering()->ReduceLoadElement(node);
EnqueueUses(node, state);
}
void MemoryOptimizer::VisitLoadField(Node* node, AllocationState const* state) {
DCHECK_EQ(IrOpcode::kLoadField, node->opcode());
memory_lowering()->ReduceLoadField(node);
EnqueueUses(node, state);
}
void MemoryOptimizer::VisitStoreElement(Node* node,
AllocationState const* state) {
DCHECK_EQ(IrOpcode::kStoreElement, node->opcode());
memory_lowering()->ReduceStoreElement(node, state);
EnqueueUses(node, state);
}
void MemoryOptimizer::VisitStoreField(Node* node,
AllocationState const* state) {
DCHECK_EQ(IrOpcode::kStoreField, node->opcode());
memory_lowering()->ReduceStoreField(node, state);
EnqueueUses(node, state);
}
void MemoryOptimizer::VisitStore(Node* node, AllocationState const* state) {
DCHECK_EQ(IrOpcode::kStore, node->opcode());
memory_lowering()->ReduceStore(node, state);
EnqueueUses(node, state);
}
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::VisitOtherEffect(Node* node,
AllocationState const* state) {
EnqueueUses(node, state);
}
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();
MemoryLowering::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, nullptr, 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) {
if (index == 0) {
if (CanLoopAllocate(node, zone())) {
// If the loop can allocate, we start with an empty state at the
// beginning.
EnqueueUses(node, empty_state());
} else {
// If the loop cannot allocate, we can just propagate the state from
// before the loop.
EnqueueUses(node, state);
}
} else {
// Do not revisit backedges.
}
} 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(); }
} // namespace compiler
} // namespace internal
} // namespace v8
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