blob: f722cf91a70714e339f6a47dc707216bec628d96 [file] [log] [blame]
/*
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <string>
#include "scheduler.h"
#include "base/scoped_arena_allocator.h"
#include "base/scoped_arena_containers.h"
#include "data_type-inl.h"
#include "prepare_for_register_allocation.h"
#ifdef ART_ENABLE_CODEGEN_arm64
#include "scheduler_arm64.h"
#endif
#ifdef ART_ENABLE_CODEGEN_arm
#include "scheduler_arm.h"
#endif
namespace art {
void SchedulingGraph::AddDependency(SchedulingNode* node,
SchedulingNode* dependency,
bool is_data_dependency) {
if (node == nullptr || dependency == nullptr) {
// A `nullptr` node indicates an instruction out of scheduling range (eg. in
// an other block), so we do not need to add a dependency edge to the graph.
return;
}
if (is_data_dependency) {
node->AddDataPredecessor(dependency);
} else {
node->AddOtherPredecessor(dependency);
}
}
bool SideEffectDependencyAnalysis::HasReorderingDependency(const HInstruction* instr1,
const HInstruction* instr2) {
SideEffects instr1_side_effects = instr1->GetSideEffects();
SideEffects instr2_side_effects = instr2->GetSideEffects();
// Read after write.
if (instr1_side_effects.MayDependOn(instr2_side_effects)) {
return true;
}
// Write after read.
if (instr2_side_effects.MayDependOn(instr1_side_effects)) {
return true;
}
// Memory write after write.
if (instr1_side_effects.DoesAnyWrite() && instr2_side_effects.DoesAnyWrite()) {
return true;
}
return false;
}
size_t SideEffectDependencyAnalysis::MemoryDependencyAnalysis::ArrayAccessHeapLocation(
HInstruction* instruction) const {
DCHECK(heap_location_collector_ != nullptr);
size_t heap_loc = heap_location_collector_->GetArrayHeapLocation(instruction);
// This array access should be analyzed and added to HeapLocationCollector before.
DCHECK(heap_loc != HeapLocationCollector::kHeapLocationNotFound);
return heap_loc;
}
bool SideEffectDependencyAnalysis::MemoryDependencyAnalysis::ArrayAccessMayAlias(
HInstruction* instr1, HInstruction* instr2) const {
DCHECK(heap_location_collector_ != nullptr);
size_t instr1_heap_loc = ArrayAccessHeapLocation(instr1);
size_t instr2_heap_loc = ArrayAccessHeapLocation(instr2);
// For example: arr[0] and arr[0]
if (instr1_heap_loc == instr2_heap_loc) {
return true;
}
// For example: arr[0] and arr[i]
if (heap_location_collector_->MayAlias(instr1_heap_loc, instr2_heap_loc)) {
return true;
}
return false;
}
static bool IsArrayAccess(const HInstruction* instruction) {
return instruction->IsArrayGet() || instruction->IsArraySet();
}
static bool IsInstanceFieldAccess(const HInstruction* instruction) {
return instruction->IsInstanceFieldGet() ||
instruction->IsInstanceFieldSet() ||
instruction->IsUnresolvedInstanceFieldGet() ||
instruction->IsUnresolvedInstanceFieldSet();
}
static bool IsStaticFieldAccess(const HInstruction* instruction) {
return instruction->IsStaticFieldGet() ||
instruction->IsStaticFieldSet() ||
instruction->IsUnresolvedStaticFieldGet() ||
instruction->IsUnresolvedStaticFieldSet();
}
static bool IsResolvedFieldAccess(const HInstruction* instruction) {
return instruction->IsInstanceFieldGet() ||
instruction->IsInstanceFieldSet() ||
instruction->IsStaticFieldGet() ||
instruction->IsStaticFieldSet();
}
static bool IsUnresolvedFieldAccess(const HInstruction* instruction) {
return instruction->IsUnresolvedInstanceFieldGet() ||
instruction->IsUnresolvedInstanceFieldSet() ||
instruction->IsUnresolvedStaticFieldGet() ||
instruction->IsUnresolvedStaticFieldSet();
}
static bool IsFieldAccess(const HInstruction* instruction) {
return IsResolvedFieldAccess(instruction) || IsUnresolvedFieldAccess(instruction);
}
static const FieldInfo* GetFieldInfo(const HInstruction* instruction) {
if (instruction->IsInstanceFieldGet()) {
return &instruction->AsInstanceFieldGet()->GetFieldInfo();
} else if (instruction->IsInstanceFieldSet()) {
return &instruction->AsInstanceFieldSet()->GetFieldInfo();
} else if (instruction->IsStaticFieldGet()) {
return &instruction->AsStaticFieldGet()->GetFieldInfo();
} else if (instruction->IsStaticFieldSet()) {
return &instruction->AsStaticFieldSet()->GetFieldInfo();
} else {
LOG(FATAL) << "Unexpected field access type";
UNREACHABLE();
}
}
size_t SideEffectDependencyAnalysis::MemoryDependencyAnalysis::FieldAccessHeapLocation(
const HInstruction* instr) const {
DCHECK(instr != nullptr);
DCHECK(GetFieldInfo(instr) != nullptr);
DCHECK(heap_location_collector_ != nullptr);
size_t heap_loc = heap_location_collector_->GetFieldHeapLocation(instr->InputAt(0),
GetFieldInfo(instr));
// This field access should be analyzed and added to HeapLocationCollector before.
DCHECK(heap_loc != HeapLocationCollector::kHeapLocationNotFound);
return heap_loc;
}
bool SideEffectDependencyAnalysis::MemoryDependencyAnalysis::FieldAccessMayAlias(
const HInstruction* instr1, const HInstruction* instr2) const {
DCHECK(heap_location_collector_ != nullptr);
// Static and instance field accesses should not alias.
if ((IsInstanceFieldAccess(instr1) && IsStaticFieldAccess(instr2)) ||
(IsStaticFieldAccess(instr1) && IsInstanceFieldAccess(instr2))) {
return false;
}
// If either of the field accesses is unresolved.
if (IsUnresolvedFieldAccess(instr1) || IsUnresolvedFieldAccess(instr2)) {
// Conservatively treat these two accesses may alias.
return true;
}
// If both fields accesses are resolved.
size_t instr1_field_access_heap_loc = FieldAccessHeapLocation(instr1);
size_t instr2_field_access_heap_loc = FieldAccessHeapLocation(instr2);
if (instr1_field_access_heap_loc == instr2_field_access_heap_loc) {
return true;
}
if (!heap_location_collector_->MayAlias(instr1_field_access_heap_loc,
instr2_field_access_heap_loc)) {
return false;
}
return true;
}
bool SideEffectDependencyAnalysis::MemoryDependencyAnalysis::HasMemoryDependency(
HInstruction* instr1, HInstruction* instr2) const {
if (!HasReorderingDependency(instr1, instr2)) {
return false;
}
if (heap_location_collector_ == nullptr ||
heap_location_collector_->GetNumberOfHeapLocations() == 0) {
// Without HeapLocation information from load store analysis,
// we cannot do further disambiguation analysis on these two instructions.
// Just simply say that those two instructions have memory dependency.
return true;
}
if (IsArrayAccess(instr1) && IsArrayAccess(instr2)) {
return ArrayAccessMayAlias(instr1, instr2);
}
if (IsFieldAccess(instr1) && IsFieldAccess(instr2)) {
return FieldAccessMayAlias(instr1, instr2);
}
// TODO(xueliang): LSA to support alias analysis among HVecLoad, HVecStore and ArrayAccess
if (instr1->IsVecMemoryOperation() && instr2->IsVecMemoryOperation()) {
return true;
}
if (instr1->IsVecMemoryOperation() && IsArrayAccess(instr2)) {
return true;
}
if (IsArrayAccess(instr1) && instr2->IsVecMemoryOperation()) {
return true;
}
// Heap accesses of different kinds should not alias.
if (IsArrayAccess(instr1) && IsFieldAccess(instr2)) {
return false;
}
if (IsFieldAccess(instr1) && IsArrayAccess(instr2)) {
return false;
}
if (instr1->IsVecMemoryOperation() && IsFieldAccess(instr2)) {
return false;
}
if (IsFieldAccess(instr1) && instr2->IsVecMemoryOperation()) {
return false;
}
// We conservatively treat all other cases having dependency,
// for example, Invoke and ArrayGet.
return true;
}
bool SideEffectDependencyAnalysis::HasExceptionDependency(const HInstruction* instr1,
const HInstruction* instr2) {
if (instr2->CanThrow() && instr1->GetSideEffects().DoesAnyWrite()) {
return true;
}
if (instr2->GetSideEffects().DoesAnyWrite() && instr1->CanThrow()) {
return true;
}
if (instr2->CanThrow() && instr1->CanThrow()) {
return true;
}
// Above checks should cover all cases where we cannot reorder two
// instructions which may throw exception.
return false;
}
// Check if the specified instruction is a better candidate which more likely will
// have other instructions depending on it.
static bool IsBetterCandidateWithMoreLikelyDependencies(HInstruction* new_candidate,
HInstruction* old_candidate) {
if (!new_candidate->GetSideEffects().Includes(old_candidate->GetSideEffects())) {
// Weaker side effects.
return false;
}
if (old_candidate->GetSideEffects().Includes(new_candidate->GetSideEffects())) {
// Same side effects, check if `new_candidate` has stronger `CanThrow()`.
return new_candidate->CanThrow() && !old_candidate->CanThrow();
} else {
// Stronger side effects, check if `new_candidate` has at least as strong `CanThrow()`.
return new_candidate->CanThrow() || !old_candidate->CanThrow();
}
}
void SchedulingGraph::AddCrossIterationDependencies(SchedulingNode* node) {
for (HInstruction* instruction : node->GetInstruction()->GetInputs()) {
// Having a phi-function from a loop header as an input means the current node of the
// scheduling graph has a cross-iteration dependency because such phi-functions bring values
// from the previous iteration to the current iteration.
if (!instruction->IsLoopHeaderPhi()) {
continue;
}
for (HInstruction* phi_input : instruction->GetInputs()) {
// As a scheduling graph of the current basic block is built by
// processing instructions bottom-up, nullptr returned by GetNode means
// an instruction defining a value for the phi is either before the
// instruction represented by node or it is in a different basic block.
SchedulingNode* def_node = GetNode(phi_input);
// We don't create a dependency if there are uses besides the use in phi.
// In such cases a register to hold phi_input is usually allocated and
// a MOV instruction is generated. In cases with multiple uses and no MOV
// instruction, reordering creating a MOV instruction can improve
// performance more than an attempt to avoid a MOV instruction.
if (def_node != nullptr && def_node != node && phi_input->GetUses().HasExactlyOneElement()) {
// We have an implicit data dependency between node and def_node.
// AddAddDataDependency cannot be used because it is for explicit data dependencies.
// So AddOtherDependency is used.
AddOtherDependency(def_node, node);
}
}
}
}
void SchedulingGraph::AddDependencies(SchedulingNode* instruction_node,
bool is_scheduling_barrier) {
HInstruction* instruction = instruction_node->GetInstruction();
// Define-use dependencies.
for (const HUseListNode<HInstruction*>& use : instruction->GetUses()) {
AddDataDependency(GetNode(use.GetUser()), instruction_node);
}
// Scheduling barrier dependencies.
DCHECK(!is_scheduling_barrier || contains_scheduling_barrier_);
if (contains_scheduling_barrier_) {
// A barrier depends on instructions after it. And instructions before the
// barrier depend on it.
for (HInstruction* other = instruction->GetNext(); other != nullptr; other = other->GetNext()) {
SchedulingNode* other_node = GetNode(other);
CHECK(other_node != nullptr)
<< other->DebugName()
<< " is in block " << other->GetBlock()->GetBlockId()
<< ", and expected in block " << instruction->GetBlock()->GetBlockId();
bool other_is_barrier = other_node->IsSchedulingBarrier();
if (is_scheduling_barrier || other_is_barrier) {
AddOtherDependency(other_node, instruction_node);
}
if (other_is_barrier) {
// This other scheduling barrier guarantees ordering of instructions after
// it, so avoid creating additional useless dependencies in the graph.
// For example if we have
// instr_1
// barrier_2
// instr_3
// barrier_4
// instr_5
// we only create the following non-data dependencies
// 1 -> 2
// 2 -> 3
// 2 -> 4
// 3 -> 4
// 4 -> 5
// and do not create
// 1 -> 4
// 2 -> 5
// Note that in this example we could also avoid creating the dependency
// `2 -> 4`. But if we remove `instr_3` that dependency is required to
// order the barriers. So we generate it to avoid a special case.
break;
}
}
}
// Side effect dependencies.
if (!instruction->GetSideEffects().DoesNothing() || instruction->CanThrow()) {
HInstruction* dep_chain_candidate = nullptr;
for (HInstruction* other = instruction->GetNext(); other != nullptr; other = other->GetNext()) {
SchedulingNode* other_node = GetNode(other);
if (other_node->IsSchedulingBarrier()) {
// We have reached a scheduling barrier so we can stop further
// processing.
//
// As a "other" dependency is not set up if a data dependency exists, we need to check that
// one of them must exist.
DCHECK(other_node->HasOtherDependency(instruction_node)
|| other_node->HasDataDependency(instruction_node));
break;
}
if (side_effect_dependency_analysis_.HasSideEffectDependency(other, instruction)) {
if (dep_chain_candidate != nullptr &&
side_effect_dependency_analysis_.HasSideEffectDependency(other, dep_chain_candidate)) {
// Skip an explicit dependency to reduce memory usage, rely on the transitive dependency.
} else {
AddOtherDependency(other_node, instruction_node);
}
// Check if `other` is a better candidate which more likely will have other instructions
// depending on it.
if (dep_chain_candidate == nullptr ||
IsBetterCandidateWithMoreLikelyDependencies(other, dep_chain_candidate)) {
dep_chain_candidate = other;
}
}
}
}
// Environment dependencies.
// We do not need to process those if the instruction is a scheduling barrier,
// since the barrier already has non-data dependencies on all following
// instructions.
if (!is_scheduling_barrier) {
for (const HUseListNode<HEnvironment*>& use : instruction->GetEnvUses()) {
// Note that here we could stop processing if the environment holder is
// across a scheduling barrier. But checking this would likely require
// more work than simply iterating through environment uses.
AddOtherDependency(GetNode(use.GetUser()->GetHolder()), instruction_node);
}
}
AddCrossIterationDependencies(instruction_node);
}
static const std::string InstructionTypeId(const HInstruction* instruction) {
return DataType::TypeId(instruction->GetType()) + std::to_string(instruction->GetId());
}
// Ideally we would reuse the graph visualizer code, but it is not available
// from here and it is not worth moving all that code only for our use.
static void DumpAsDotNode(std::ostream& output, const SchedulingNode* node) {
const HInstruction* instruction = node->GetInstruction();
// Use the instruction typed id as the node identifier.
std::string instruction_id = InstructionTypeId(instruction);
output << instruction_id << "[shape=record, label=\""
<< instruction_id << ' ' << instruction->DebugName() << " [";
// List the instruction's inputs in its description. When visualizing the
// graph this helps differentiating data inputs from other dependencies.
const char* seperator = "";
for (const HInstruction* input : instruction->GetInputs()) {
output << seperator << InstructionTypeId(input);
seperator = ",";
}
output << "]";
// Other properties of the node.
output << "\\ninternal_latency: " << node->GetInternalLatency();
output << "\\ncritical_path: " << node->GetCriticalPath();
if (node->IsSchedulingBarrier()) {
output << "\\n(barrier)";
}
output << "\"];\n";
// We want program order to go from top to bottom in the graph output, so we
// reverse the edges and specify `dir=back`.
for (const SchedulingNode* predecessor : node->GetDataPredecessors()) {
const HInstruction* predecessor_instruction = predecessor->GetInstruction();
output << InstructionTypeId(predecessor_instruction) << ":s -> " << instruction_id << ":n "
<< "[label=\"" << predecessor->GetLatency() << "\",dir=back]\n";
}
for (const SchedulingNode* predecessor : node->GetOtherPredecessors()) {
const HInstruction* predecessor_instruction = predecessor->GetInstruction();
output << InstructionTypeId(predecessor_instruction) << ":s -> " << instruction_id << ":n "
<< "[dir=back,color=blue]\n";
}
}
void SchedulingGraph::DumpAsDotGraph(const std::string& description,
const ScopedArenaVector<SchedulingNode*>& initial_candidates) {
// TODO(xueliang): ideally we should move scheduling information into HInstruction, after that
// we should move this dotty graph dump feature to visualizer, and have a compiler option for it.
std::ofstream output("scheduling_graphs.dot", std::ofstream::out | std::ofstream::app);
// Description of this graph, as a comment.
output << "// " << description << "\n";
// Start the dot graph. Use an increasing index for easier differentiation.
output << "digraph G {\n";
for (const auto& entry : nodes_map_) {
SchedulingNode* node = entry.second.get();
DumpAsDotNode(output, node);
}
// Create a fake 'end_of_scheduling' node to help visualization of critical_paths.
for (SchedulingNode* node : initial_candidates) {
const HInstruction* instruction = node->GetInstruction();
output << InstructionTypeId(instruction) << ":s -> end_of_scheduling:n "
<< "[label=\"" << node->GetLatency() << "\",dir=back]\n";
}
// End of the dot graph.
output << "}\n";
output.close();
}
SchedulingNode* CriticalPathSchedulingNodeSelector::SelectMaterializedCondition(
ScopedArenaVector<SchedulingNode*>* nodes, const SchedulingGraph& graph) const {
// Schedule condition inputs that can be materialized immediately before their use.
// In following example, after we've scheduled HSelect, we want LessThan to be scheduled
// immediately, because it is a materialized condition, and will be emitted right before HSelect
// in codegen phase.
//
// i20 HLessThan [...] HLessThan HAdd HAdd
// i21 HAdd [...] ===> | | |
// i22 HAdd [...] +----------+---------+
// i23 HSelect [i21, i22, i20] HSelect
if (prev_select_ == nullptr) {
return nullptr;
}
const HInstruction* instruction = prev_select_->GetInstruction();
const HCondition* condition = nullptr;
DCHECK(instruction != nullptr);
if (instruction->IsIf()) {
condition = instruction->AsIf()->InputAt(0)->AsCondition();
} else if (instruction->IsSelect()) {
condition = instruction->AsSelect()->GetCondition()->AsCondition();
}
SchedulingNode* condition_node = (condition != nullptr) ? graph.GetNode(condition) : nullptr;
if ((condition_node != nullptr) &&
condition->HasOnlyOneNonEnvironmentUse() &&
ContainsElement(*nodes, condition_node)) {
DCHECK(!condition_node->HasUnscheduledSuccessors());
// Remove the condition from the list of candidates and schedule it.
RemoveElement(*nodes, condition_node);
return condition_node;
}
return nullptr;
}
SchedulingNode* CriticalPathSchedulingNodeSelector::PopHighestPriorityNode(
ScopedArenaVector<SchedulingNode*>* nodes, const SchedulingGraph& graph) {
DCHECK(!nodes->empty());
SchedulingNode* select_node = nullptr;
// Optimize for materialized condition and its emit before use scenario.
select_node = SelectMaterializedCondition(nodes, graph);
if (select_node == nullptr) {
// Get highest priority node based on critical path information.
select_node = (*nodes)[0];
size_t select = 0;
for (size_t i = 1, e = nodes->size(); i < e; i++) {
SchedulingNode* check = (*nodes)[i];
SchedulingNode* candidate = (*nodes)[select];
select_node = GetHigherPrioritySchedulingNode(candidate, check);
if (select_node == check) {
select = i;
}
}
DeleteNodeAtIndex(nodes, select);
}
prev_select_ = select_node;
return select_node;
}
SchedulingNode* CriticalPathSchedulingNodeSelector::GetHigherPrioritySchedulingNode(
SchedulingNode* candidate, SchedulingNode* check) const {
uint32_t candidate_path = candidate->GetCriticalPath();
uint32_t check_path = check->GetCriticalPath();
// First look at the critical_path.
if (check_path != candidate_path) {
return check_path < candidate_path ? check : candidate;
}
// If both critical paths are equal, schedule instructions with a higher latency
// first in program order.
return check->GetLatency() < candidate->GetLatency() ? check : candidate;
}
void HScheduler::Schedule(HGraph* graph) {
// We run lsa here instead of in a separate pass to better control whether we
// should run the analysis or not.
const HeapLocationCollector* heap_location_collector = nullptr;
LoadStoreAnalysis lsa(graph);
if (!only_optimize_loop_blocks_ || graph->HasLoops()) {
lsa.Run();
heap_location_collector = &lsa.GetHeapLocationCollector();
}
for (HBasicBlock* block : graph->GetReversePostOrder()) {
if (IsSchedulable(block)) {
Schedule(block, heap_location_collector);
}
}
}
void HScheduler::Schedule(HBasicBlock* block,
const HeapLocationCollector* heap_location_collector) {
ScopedArenaAllocator allocator(block->GetGraph()->GetArenaStack());
ScopedArenaVector<SchedulingNode*> scheduling_nodes(allocator.Adapter(kArenaAllocScheduler));
// Build the scheduling graph.
SchedulingGraph scheduling_graph(&allocator, heap_location_collector);
for (HBackwardInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) {
HInstruction* instruction = it.Current();
CHECK_EQ(instruction->GetBlock(), block)
<< instruction->DebugName()
<< " is in block " << instruction->GetBlock()->GetBlockId()
<< ", and expected in block " << block->GetBlockId();
SchedulingNode* node = scheduling_graph.AddNode(instruction, IsSchedulingBarrier(instruction));
CalculateLatency(node);
scheduling_nodes.push_back(node);
}
if (scheduling_graph.Size() <= 1) {
return;
}
cursor_ = block->GetLastInstruction();
// The list of candidates for scheduling. A node becomes a candidate when all
// its predecessors have been scheduled.
ScopedArenaVector<SchedulingNode*> candidates(allocator.Adapter(kArenaAllocScheduler));
// Find the initial candidates for scheduling.
for (SchedulingNode* node : scheduling_nodes) {
if (!node->HasUnscheduledSuccessors()) {
node->MaybeUpdateCriticalPath(node->GetLatency());
candidates.push_back(node);
}
}
ScopedArenaVector<SchedulingNode*> initial_candidates(allocator.Adapter(kArenaAllocScheduler));
if (kDumpDotSchedulingGraphs) {
// Remember the list of initial candidates for debug output purposes.
initial_candidates.assign(candidates.begin(), candidates.end());
}
// Schedule all nodes.
selector_->Reset();
while (!candidates.empty()) {
SchedulingNode* node = selector_->PopHighestPriorityNode(&candidates, scheduling_graph);
Schedule(node, &candidates);
}
if (kDumpDotSchedulingGraphs) {
// Dump the graph in `dot` format.
HGraph* graph = block->GetGraph();
std::stringstream description;
description << graph->GetDexFile().PrettyMethod(graph->GetMethodIdx())
<< " B" << block->GetBlockId();
scheduling_graph.DumpAsDotGraph(description.str(), initial_candidates);
}
}
void HScheduler::Schedule(SchedulingNode* scheduling_node,
/*inout*/ ScopedArenaVector<SchedulingNode*>* candidates) {
// Check whether any of the node's predecessors will be valid candidates after
// this node is scheduled.
uint32_t path_to_node = scheduling_node->GetCriticalPath();
for (SchedulingNode* predecessor : scheduling_node->GetDataPredecessors()) {
predecessor->MaybeUpdateCriticalPath(
path_to_node + predecessor->GetInternalLatency() + predecessor->GetLatency());
predecessor->DecrementNumberOfUnscheduledSuccessors();
if (!predecessor->HasUnscheduledSuccessors()) {
candidates->push_back(predecessor);
}
}
for (SchedulingNode* predecessor : scheduling_node->GetOtherPredecessors()) {
// Do not update the critical path.
// The 'other' (so 'non-data') dependencies (usually) do not represent a
// 'material' dependency of nodes on others. They exist for program
// correctness. So we do not use them to compute the critical path.
predecessor->DecrementNumberOfUnscheduledSuccessors();
if (!predecessor->HasUnscheduledSuccessors()) {
candidates->push_back(predecessor);
}
}
Schedule(scheduling_node->GetInstruction());
}
// Move an instruction after cursor instruction inside one basic block.
static void MoveAfterInBlock(HInstruction* instruction, HInstruction* cursor) {
DCHECK_EQ(instruction->GetBlock(), cursor->GetBlock());
DCHECK_NE(cursor, cursor->GetBlock()->GetLastInstruction());
DCHECK(!instruction->IsControlFlow());
DCHECK(!cursor->IsControlFlow());
instruction->MoveBefore(cursor->GetNext(), /* do_checks= */ false);
}
void HScheduler::Schedule(HInstruction* instruction) {
if (instruction == cursor_) {
cursor_ = cursor_->GetPrevious();
} else {
MoveAfterInBlock(instruction, cursor_);
}
}
bool HScheduler::IsSchedulable(const HInstruction* instruction) const {
// We want to avoid exhaustively listing all instructions, so we first check
// for instruction categories that we know are safe.
if (instruction->IsControlFlow() ||
instruction->IsConstant()) {
return true;
}
// Currently all unary and binary operations are safe to schedule, so avoid
// checking for each of them individually.
// Since nothing prevents a new scheduling-unsafe HInstruction to subclass
// HUnaryOperation (or HBinaryOperation), check in debug mode that we have
// the exhaustive lists here.
if (instruction->IsUnaryOperation()) {
DCHECK(instruction->IsAbs() ||
instruction->IsBooleanNot() ||
instruction->IsNot() ||
instruction->IsNeg()) << "unexpected instruction " << instruction->DebugName();
return true;
}
if (instruction->IsBinaryOperation()) {
DCHECK(instruction->IsAdd() ||
instruction->IsAnd() ||
instruction->IsCompare() ||
instruction->IsCondition() ||
instruction->IsDiv() ||
instruction->IsMin() ||
instruction->IsMax() ||
instruction->IsMul() ||
instruction->IsOr() ||
instruction->IsRem() ||
instruction->IsRor() ||
instruction->IsShl() ||
instruction->IsShr() ||
instruction->IsSub() ||
instruction->IsUShr() ||
instruction->IsXor()) << "unexpected instruction " << instruction->DebugName();
return true;
}
// The scheduler should not see any of these.
DCHECK(!instruction->IsParallelMove()) << "unexpected instruction " << instruction->DebugName();
// List of instructions explicitly excluded:
// HClearException
// HClinitCheck
// HDeoptimize
// HLoadClass
// HLoadException
// HMemoryBarrier
// HMonitorOperation
// HNativeDebugInfo
// HThrow
// HTryBoundary
// TODO: Some of the instructions above may be safe to schedule (maybe as
// scheduling barriers).
return instruction->IsArrayGet() ||
instruction->IsArraySet() ||
instruction->IsArrayLength() ||
instruction->IsBoundType() ||
instruction->IsBoundsCheck() ||
instruction->IsCheckCast() ||
instruction->IsClassTableGet() ||
instruction->IsCurrentMethod() ||
instruction->IsDivZeroCheck() ||
(instruction->IsInstanceFieldGet() && !instruction->AsInstanceFieldGet()->IsVolatile()) ||
(instruction->IsInstanceFieldSet() && !instruction->AsInstanceFieldSet()->IsVolatile()) ||
instruction->IsInstanceOf() ||
instruction->IsInvokeInterface() ||
instruction->IsInvokeStaticOrDirect() ||
instruction->IsInvokeUnresolved() ||
instruction->IsInvokeVirtual() ||
instruction->IsLoadString() ||
instruction->IsNewArray() ||
instruction->IsNewInstance() ||
instruction->IsNullCheck() ||
instruction->IsPackedSwitch() ||
instruction->IsParameterValue() ||
instruction->IsPhi() ||
instruction->IsReturn() ||
instruction->IsReturnVoid() ||
instruction->IsSelect() ||
(instruction->IsStaticFieldGet() && !instruction->AsStaticFieldGet()->IsVolatile()) ||
(instruction->IsStaticFieldSet() && !instruction->AsStaticFieldSet()->IsVolatile()) ||
instruction->IsSuspendCheck() ||
instruction->IsTypeConversion();
}
bool HScheduler::IsSchedulable(const HBasicBlock* block) const {
// We may be only interested in loop blocks.
if (only_optimize_loop_blocks_ && !block->IsInLoop()) {
return false;
}
if (block->GetTryCatchInformation() != nullptr) {
// Do not schedule blocks that are part of try-catch.
// Because scheduler cannot see if catch block has assumptions on the instruction order in
// the try block. In following example, if we enable scheduler for the try block,
// MulitiplyAccumulate may be scheduled before DivZeroCheck,
// which can result in an incorrect value in the catch block.
// try {
// a = a/b; // DivZeroCheck
// // Div
// c = c*d+e; // MulitiplyAccumulate
// } catch {System.out.print(c); }
return false;
}
// Check whether all instructions in this block are schedulable.
for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) {
if (!IsSchedulable(it.Current())) {
return false;
}
}
return true;
}
bool HScheduler::IsSchedulingBarrier(const HInstruction* instr) const {
return instr->IsControlFlow() ||
// Don't break calling convention.
instr->IsParameterValue() ||
// Code generation of goto relies on SuspendCheck's position.
instr->IsSuspendCheck();
}
bool HInstructionScheduling::Run(bool only_optimize_loop_blocks,
bool schedule_randomly) {
#if defined(ART_ENABLE_CODEGEN_arm64) || defined(ART_ENABLE_CODEGEN_arm)
// Phase-local allocator that allocates scheduler internal data structures like
// scheduling nodes, internel nodes map, dependencies, etc.
CriticalPathSchedulingNodeSelector critical_path_selector;
RandomSchedulingNodeSelector random_selector;
SchedulingNodeSelector* selector = schedule_randomly
? static_cast<SchedulingNodeSelector*>(&random_selector)
: static_cast<SchedulingNodeSelector*>(&critical_path_selector);
#else
// Avoid compilation error when compiling for unsupported instruction set.
UNUSED(only_optimize_loop_blocks);
UNUSED(schedule_randomly);
UNUSED(codegen_);
#endif
switch (instruction_set_) {
#ifdef ART_ENABLE_CODEGEN_arm64
case InstructionSet::kArm64: {
arm64::HSchedulerARM64 scheduler(selector);
scheduler.SetOnlyOptimizeLoopBlocks(only_optimize_loop_blocks);
scheduler.Schedule(graph_);
break;
}
#endif
#if defined(ART_ENABLE_CODEGEN_arm)
case InstructionSet::kThumb2:
case InstructionSet::kArm: {
arm::SchedulingLatencyVisitorARM arm_latency_visitor(codegen_);
arm::HSchedulerARM scheduler(selector, &arm_latency_visitor);
scheduler.SetOnlyOptimizeLoopBlocks(only_optimize_loop_blocks);
scheduler.Schedule(graph_);
break;
}
#endif
default:
break;
}
return true;
}
} // namespace art