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/*
* Copyright (C) 2015 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 "reference_type_propagation.h"
#include "art_field-inl.h"
#include "art_method-inl.h"
#include "base/scoped_arena_allocator.h"
#include "base/scoped_arena_containers.h"
#include "base/enums.h"
#include "class_linker-inl.h"
#include "class_root.h"
#include "handle_scope-inl.h"
#include "mirror/class-inl.h"
#include "mirror/dex_cache.h"
#include "scoped_thread_state_change-inl.h"
namespace art {
static inline ObjPtr<mirror::DexCache> FindDexCacheWithHint(
Thread* self, const DexFile& dex_file, Handle<mirror::DexCache> hint_dex_cache)
REQUIRES_SHARED(Locks::mutator_lock_) {
if (LIKELY(hint_dex_cache->GetDexFile() == &dex_file)) {
return hint_dex_cache.Get();
} else {
return Runtime::Current()->GetClassLinker()->FindDexCache(self, dex_file);
}
}
static inline ReferenceTypeInfo::TypeHandle GetRootHandle(VariableSizedHandleScope* handles,
ClassRoot class_root,
ReferenceTypeInfo::TypeHandle* cache) {
if (!ReferenceTypeInfo::IsValidHandle(*cache)) {
// Mutator lock is required for NewHandle.
ScopedObjectAccess soa(Thread::Current());
*cache = handles->NewHandle(GetClassRoot(class_root));
}
return *cache;
}
ReferenceTypeInfo::TypeHandle ReferenceTypePropagation::HandleCache::GetObjectClassHandle() {
return GetRootHandle(handles_, ClassRoot::kJavaLangObject, &object_class_handle_);
}
ReferenceTypeInfo::TypeHandle ReferenceTypePropagation::HandleCache::GetClassClassHandle() {
return GetRootHandle(handles_, ClassRoot::kJavaLangClass, &class_class_handle_);
}
ReferenceTypeInfo::TypeHandle ReferenceTypePropagation::HandleCache::GetMethodHandleClassHandle() {
return GetRootHandle(handles_,
ClassRoot::kJavaLangInvokeMethodHandleImpl,
&method_handle_class_handle_);
}
ReferenceTypeInfo::TypeHandle ReferenceTypePropagation::HandleCache::GetMethodTypeClassHandle() {
return GetRootHandle(handles_, ClassRoot::kJavaLangInvokeMethodType, &method_type_class_handle_);
}
ReferenceTypeInfo::TypeHandle ReferenceTypePropagation::HandleCache::GetStringClassHandle() {
return GetRootHandle(handles_, ClassRoot::kJavaLangString, &string_class_handle_);
}
ReferenceTypeInfo::TypeHandle ReferenceTypePropagation::HandleCache::GetThrowableClassHandle() {
return GetRootHandle(handles_, ClassRoot::kJavaLangThrowable, &throwable_class_handle_);
}
class ReferenceTypePropagation::RTPVisitor : public HGraphDelegateVisitor {
public:
RTPVisitor(HGraph* graph,
Handle<mirror::ClassLoader> class_loader,
Handle<mirror::DexCache> hint_dex_cache,
HandleCache* handle_cache,
bool is_first_run)
: HGraphDelegateVisitor(graph),
class_loader_(class_loader),
hint_dex_cache_(hint_dex_cache),
handle_cache_(handle_cache),
allocator_(graph->GetArenaStack()),
worklist_(allocator_.Adapter(kArenaAllocReferenceTypePropagation)),
is_first_run_(is_first_run) {
worklist_.reserve(kDefaultWorklistSize);
}
void VisitDeoptimize(HDeoptimize* deopt) override;
void VisitNewInstance(HNewInstance* new_instance) override;
void VisitLoadClass(HLoadClass* load_class) override;
void VisitInstanceOf(HInstanceOf* load_class) override;
void VisitClinitCheck(HClinitCheck* clinit_check) override;
void VisitLoadMethodHandle(HLoadMethodHandle* instr) override;
void VisitLoadMethodType(HLoadMethodType* instr) override;
void VisitLoadString(HLoadString* instr) override;
void VisitLoadException(HLoadException* instr) override;
void VisitNewArray(HNewArray* instr) override;
void VisitParameterValue(HParameterValue* instr) override;
void VisitInstanceFieldGet(HInstanceFieldGet* instr) override;
void VisitStaticFieldGet(HStaticFieldGet* instr) override;
void VisitUnresolvedInstanceFieldGet(HUnresolvedInstanceFieldGet* instr) override;
void VisitUnresolvedStaticFieldGet(HUnresolvedStaticFieldGet* instr) override;
void VisitInvoke(HInvoke* instr) override;
void VisitArrayGet(HArrayGet* instr) override;
void VisitCheckCast(HCheckCast* instr) override;
void VisitBoundType(HBoundType* instr) override;
void VisitNullCheck(HNullCheck* instr) override;
void VisitPhi(HPhi* phi) override;
void VisitBasicBlock(HBasicBlock* block) override;
void ProcessWorklist();
private:
void UpdateFieldAccessTypeInfo(HInstruction* instr, const FieldInfo& info);
void SetClassAsTypeInfo(HInstruction* instr, ObjPtr<mirror::Class> klass, bool is_exact)
REQUIRES_SHARED(Locks::mutator_lock_);
void BoundTypeForIfNotNull(HBasicBlock* block);
static void BoundTypeForIfInstanceOf(HBasicBlock* block);
static bool UpdateNullability(HInstruction* instr);
static void UpdateBoundType(HBoundType* bound_type) REQUIRES_SHARED(Locks::mutator_lock_);
void UpdateArrayGet(HArrayGet* instr) REQUIRES_SHARED(Locks::mutator_lock_);
void UpdatePhi(HPhi* phi) REQUIRES_SHARED(Locks::mutator_lock_);
bool UpdateReferenceTypeInfo(HInstruction* instr);
void UpdateReferenceTypeInfo(HInstruction* instr,
dex::TypeIndex type_idx,
const DexFile& dex_file,
bool is_exact);
void AddToWorklist(HInstruction* instruction);
void AddDependentInstructionsToWorklist(HInstruction* instruction);
static constexpr size_t kDefaultWorklistSize = 8;
Handle<mirror::ClassLoader> class_loader_;
Handle<mirror::DexCache> hint_dex_cache_;
HandleCache* const handle_cache_;
// Use local allocator for allocating memory.
ScopedArenaAllocator allocator_;
ScopedArenaVector<HInstruction*> worklist_;
const bool is_first_run_;
};
ReferenceTypePropagation::ReferenceTypePropagation(HGraph* graph,
Handle<mirror::ClassLoader> class_loader,
Handle<mirror::DexCache> hint_dex_cache,
VariableSizedHandleScope* handles,
bool is_first_run,
const char* name)
: HOptimization(graph, name),
class_loader_(class_loader),
hint_dex_cache_(hint_dex_cache),
handle_cache_(handles),
is_first_run_(is_first_run) {
}
void ReferenceTypePropagation::ValidateTypes() {
// TODO: move this to the graph checker.
if (kIsDebugBuild) {
ScopedObjectAccess soa(Thread::Current());
for (HBasicBlock* block : graph_->GetReversePostOrder()) {
for (HInstructionIterator iti(block->GetInstructions()); !iti.Done(); iti.Advance()) {
HInstruction* instr = iti.Current();
if (instr->GetType() == DataType::Type::kReference) {
DCHECK(instr->GetReferenceTypeInfo().IsValid())
<< "Invalid RTI for instruction: " << instr->DebugName();
if (instr->IsBoundType()) {
DCHECK(instr->AsBoundType()->GetUpperBound().IsValid());
} else if (instr->IsLoadClass()) {
HLoadClass* cls = instr->AsLoadClass();
DCHECK(cls->GetReferenceTypeInfo().IsExact());
DCHECK(!cls->GetLoadedClassRTI().IsValid() || cls->GetLoadedClassRTI().IsExact());
} else if (instr->IsNullCheck()) {
DCHECK(instr->GetReferenceTypeInfo().IsEqual(instr->InputAt(0)->GetReferenceTypeInfo()))
<< "NullCheck " << instr->GetReferenceTypeInfo()
<< "Input(0) " << instr->InputAt(0)->GetReferenceTypeInfo();
}
} else if (instr->IsInstanceOf()) {
HInstanceOf* iof = instr->AsInstanceOf();
DCHECK(!iof->GetTargetClassRTI().IsValid() || iof->GetTargetClassRTI().IsExact());
} else if (instr->IsCheckCast()) {
HCheckCast* check = instr->AsCheckCast();
DCHECK(!check->GetTargetClassRTI().IsValid() || check->GetTargetClassRTI().IsExact());
}
}
}
}
}
void ReferenceTypePropagation::Visit(HInstruction* instruction) {
RTPVisitor visitor(graph_,
class_loader_,
hint_dex_cache_,
&handle_cache_,
is_first_run_);
instruction->Accept(&visitor);
}
// Check if we should create a bound type for the given object at the specified
// position. Because of inlining and the fact we run RTP more than once and we
// might have a HBoundType already. If we do, we should not create a new one.
// In this case we also assert that there are no other uses of the object (except
// the bound type) dominated by the specified dominator_instr or dominator_block.
static bool ShouldCreateBoundType(HInstruction* position,
HInstruction* obj,
ReferenceTypeInfo upper_bound,
HInstruction* dominator_instr,
HBasicBlock* dominator_block)
REQUIRES_SHARED(Locks::mutator_lock_) {
// If the position where we should insert the bound type is not already a
// a bound type then we need to create one.
if (position == nullptr || !position->IsBoundType()) {
return true;
}
HBoundType* existing_bound_type = position->AsBoundType();
if (existing_bound_type->GetUpperBound().IsSupertypeOf(upper_bound)) {
if (kIsDebugBuild) {
// Check that the existing HBoundType dominates all the uses.
for (const HUseListNode<HInstruction*>& use : obj->GetUses()) {
HInstruction* user = use.GetUser();
if (dominator_instr != nullptr) {
DCHECK(!dominator_instr->StrictlyDominates(user)
|| user == existing_bound_type
|| existing_bound_type->StrictlyDominates(user));
} else if (dominator_block != nullptr) {
DCHECK(!dominator_block->Dominates(user->GetBlock())
|| user == existing_bound_type
|| existing_bound_type->StrictlyDominates(user));
}
}
}
} else {
// TODO: if the current bound type is a refinement we could update the
// existing_bound_type with the a new upper limit. However, we also need to
// update its users and have access to the work list.
}
return false;
}
// Helper method to bound the type of `receiver` for all instructions dominated
// by `start_block`, or `start_instruction` if `start_block` is null. The new
// bound type will have its upper bound be `class_rti`.
static void BoundTypeIn(HInstruction* receiver,
HBasicBlock* start_block,
HInstruction* start_instruction,
const ReferenceTypeInfo& class_rti) {
// We only need to bound the type if we have uses in the relevant block.
// So start with null and create the HBoundType lazily, only if it's needed.
HBoundType* bound_type = nullptr;
DCHECK(!receiver->IsLoadClass()) << "We should not replace HLoadClass instructions";
const HUseList<HInstruction*>& uses = receiver->GetUses();
for (auto it = uses.begin(), end = uses.end(); it != end; /* ++it below */) {
HInstruction* user = it->GetUser();
size_t index = it->GetIndex();
// Increment `it` now because `*it` may disappear thanks to user->ReplaceInput().
++it;
bool dominates = (start_instruction != nullptr)
? start_instruction->StrictlyDominates(user)
: start_block->Dominates(user->GetBlock());
if (!dominates) {
continue;
}
if (bound_type == nullptr) {
ScopedObjectAccess soa(Thread::Current());
HInstruction* insert_point = (start_instruction != nullptr)
? start_instruction->GetNext()
: start_block->GetFirstInstruction();
if (ShouldCreateBoundType(
insert_point, receiver, class_rti, start_instruction, start_block)) {
bound_type = new (receiver->GetBlock()->GetGraph()->GetAllocator()) HBoundType(receiver);
bound_type->SetUpperBound(class_rti, /* can_be_null= */ false);
start_block->InsertInstructionBefore(bound_type, insert_point);
// To comply with the RTP algorithm, don't type the bound type just yet, it will
// be handled in RTPVisitor::VisitBoundType.
} else {
// We already have a bound type on the position we would need to insert
// the new one. The existing bound type should dominate all the users
// (dchecked) so there's no need to continue.
break;
}
}
user->ReplaceInput(bound_type, index);
}
// If the receiver is a null check, also bound the type of the actual
// receiver.
if (receiver->IsNullCheck()) {
BoundTypeIn(receiver->InputAt(0), start_block, start_instruction, class_rti);
}
}
// Recognize the patterns:
// if (obj.shadow$_klass_ == Foo.class) ...
// deoptimize if (obj.shadow$_klass_ == Foo.class)
static void BoundTypeForClassCheck(HInstruction* check) {
if (!check->IsIf() && !check->IsDeoptimize()) {
return;
}
HInstruction* compare = check->InputAt(0);
if (!compare->IsEqual() && !compare->IsNotEqual()) {
return;
}
HInstruction* input_one = compare->InputAt(0);
HInstruction* input_two = compare->InputAt(1);
HLoadClass* load_class = input_one->IsLoadClass()
? input_one->AsLoadClass()
: input_two->AsLoadClass();
if (load_class == nullptr) {
return;
}
ReferenceTypeInfo class_rti = load_class->GetLoadedClassRTI();
if (!class_rti.IsValid()) {
// We have loaded an unresolved class. Don't bother bounding the type.
return;
}
HInstanceFieldGet* field_get = (load_class == input_one)
? input_two->AsInstanceFieldGet()
: input_one->AsInstanceFieldGet();
if (field_get == nullptr) {
return;
}
HInstruction* receiver = field_get->InputAt(0);
ReferenceTypeInfo receiver_type = receiver->GetReferenceTypeInfo();
if (receiver_type.IsExact()) {
// If we already know the receiver type, don't bother updating its users.
return;
}
{
ScopedObjectAccess soa(Thread::Current());
ArtField* field = GetClassRoot<mirror::Object>()->GetInstanceField(0);
DCHECK_EQ(std::string(field->GetName()), "shadow$_klass_");
if (field_get->GetFieldInfo().GetField() != field) {
return;
}
}
if (check->IsIf()) {
HBasicBlock* trueBlock = compare->IsEqual()
? check->AsIf()->IfTrueSuccessor()
: check->AsIf()->IfFalseSuccessor();
BoundTypeIn(receiver, trueBlock, /* start_instruction= */ nullptr, class_rti);
} else {
DCHECK(check->IsDeoptimize());
if (compare->IsEqual() && check->AsDeoptimize()->GuardsAnInput()) {
check->SetReferenceTypeInfo(class_rti);
}
}
}
bool ReferenceTypePropagation::Run() {
RTPVisitor visitor(graph_, class_loader_, hint_dex_cache_, &handle_cache_, is_first_run_);
// To properly propagate type info we need to visit in the dominator-based order.
// Reverse post order guarantees a node's dominators are visited first.
// We take advantage of this order in `VisitBasicBlock`.
for (HBasicBlock* block : graph_->GetReversePostOrder()) {
visitor.VisitBasicBlock(block);
}
visitor.ProcessWorklist();
ValidateTypes();
return true;
}
void ReferenceTypePropagation::RTPVisitor::VisitBasicBlock(HBasicBlock* block) {
// Handle Phis first as there might be instructions in the same block who depend on them.
for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) {
VisitPhi(it.Current()->AsPhi());
}
// Handle instructions. Since RTP may add HBoundType instructions just after the
// last visited instruction, use `HInstructionIteratorHandleChanges` iterator.
for (HInstructionIteratorHandleChanges it(block->GetInstructions()); !it.Done(); it.Advance()) {
HInstruction* instr = it.Current();
instr->Accept(this);
}
// Add extra nodes to bound types.
BoundTypeForIfNotNull(block);
BoundTypeForIfInstanceOf(block);
BoundTypeForClassCheck(block->GetLastInstruction());
}
void ReferenceTypePropagation::RTPVisitor::BoundTypeForIfNotNull(HBasicBlock* block) {
HIf* ifInstruction = block->GetLastInstruction()->AsIf();
if (ifInstruction == nullptr) {
return;
}
HInstruction* ifInput = ifInstruction->InputAt(0);
if (!ifInput->IsNotEqual() && !ifInput->IsEqual()) {
return;
}
HInstruction* input0 = ifInput->InputAt(0);
HInstruction* input1 = ifInput->InputAt(1);
HInstruction* obj = nullptr;
if (input1->IsNullConstant()) {
obj = input0;
} else if (input0->IsNullConstant()) {
obj = input1;
} else {
return;
}
if (!obj->CanBeNull() || obj->IsNullConstant()) {
// Null check is dead code and will be removed by DCE.
return;
}
DCHECK(!obj->IsLoadClass()) << "We should not replace HLoadClass instructions";
// We only need to bound the type if we have uses in the relevant block.
// So start with null and create the HBoundType lazily, only if it's needed.
HBasicBlock* notNullBlock = ifInput->IsNotEqual()
? ifInstruction->IfTrueSuccessor()
: ifInstruction->IfFalseSuccessor();
ReferenceTypeInfo object_rti = ReferenceTypeInfo::Create(
handle_cache_->GetObjectClassHandle(), /* is_exact= */ false);
BoundTypeIn(obj, notNullBlock, /* start_instruction= */ nullptr, object_rti);
}
// Returns true if one of the patterns below has been recognized. If so, the
// InstanceOf instruction together with the true branch of `ifInstruction` will
// be returned using the out parameters.
// Recognized patterns:
// (1) patterns equivalent to `if (obj instanceof X)`
// (a) InstanceOf -> Equal to 1 -> If
// (b) InstanceOf -> NotEqual to 0 -> If
// (c) InstanceOf -> If
// (2) patterns equivalent to `if (!(obj instanceof X))`
// (a) InstanceOf -> Equal to 0 -> If
// (b) InstanceOf -> NotEqual to 1 -> If
// (c) InstanceOf -> BooleanNot -> If
static bool MatchIfInstanceOf(HIf* ifInstruction,
/* out */ HInstanceOf** instanceOf,
/* out */ HBasicBlock** trueBranch) {
HInstruction* input = ifInstruction->InputAt(0);
if (input->IsEqual()) {
HInstruction* rhs = input->AsEqual()->GetConstantRight();
if (rhs != nullptr) {
HInstruction* lhs = input->AsEqual()->GetLeastConstantLeft();
if (lhs->IsInstanceOf() && rhs->IsIntConstant()) {
if (rhs->AsIntConstant()->IsTrue()) {
// Case (1a)
*trueBranch = ifInstruction->IfTrueSuccessor();
} else {
// Case (2a)
DCHECK(rhs->AsIntConstant()->IsFalse()) << rhs->AsIntConstant()->GetValue();
*trueBranch = ifInstruction->IfFalseSuccessor();
}
*instanceOf = lhs->AsInstanceOf();
return true;
}
}
} else if (input->IsNotEqual()) {
HInstruction* rhs = input->AsNotEqual()->GetConstantRight();
if (rhs != nullptr) {
HInstruction* lhs = input->AsNotEqual()->GetLeastConstantLeft();
if (lhs->IsInstanceOf() && rhs->IsIntConstant()) {
if (rhs->AsIntConstant()->IsFalse()) {
// Case (1b)
*trueBranch = ifInstruction->IfTrueSuccessor();
} else {
// Case (2b)
DCHECK(rhs->AsIntConstant()->IsTrue()) << rhs->AsIntConstant()->GetValue();
*trueBranch = ifInstruction->IfFalseSuccessor();
}
*instanceOf = lhs->AsInstanceOf();
return true;
}
}
} else if (input->IsInstanceOf()) {
// Case (1c)
*instanceOf = input->AsInstanceOf();
*trueBranch = ifInstruction->IfTrueSuccessor();
return true;
} else if (input->IsBooleanNot()) {
HInstruction* not_input = input->InputAt(0);
if (not_input->IsInstanceOf()) {
// Case (2c)
*instanceOf = not_input->AsInstanceOf();
*trueBranch = ifInstruction->IfFalseSuccessor();
return true;
}
}
return false;
}
// Detects if `block` is the True block for the pattern
// `if (x instanceof ClassX) { }`
// If that's the case insert an HBoundType instruction to bound the type of `x`
// to `ClassX` in the scope of the dominated blocks.
void ReferenceTypePropagation::RTPVisitor::BoundTypeForIfInstanceOf(HBasicBlock* block) {
HIf* ifInstruction = block->GetLastInstruction()->AsIf();
if (ifInstruction == nullptr) {
return;
}
// Try to recognize common `if (instanceof)` and `if (!instanceof)` patterns.
HInstanceOf* instanceOf = nullptr;
HBasicBlock* instanceOfTrueBlock = nullptr;
if (!MatchIfInstanceOf(ifInstruction, &instanceOf, &instanceOfTrueBlock)) {
return;
}
ReferenceTypeInfo class_rti = instanceOf->GetTargetClassRTI();
if (!class_rti.IsValid()) {
// He have loaded an unresolved class. Don't bother bounding the type.
return;
}
HInstruction* obj = instanceOf->InputAt(0);
if (obj->GetReferenceTypeInfo().IsExact() && !obj->IsPhi()) {
// This method is being called while doing a fixed-point calculation
// over phis. Non-phis instruction whose type is already known do
// not need to be bound to another type.
// Not that this also prevents replacing `HLoadClass` with a `HBoundType`.
// `HCheckCast` and `HInstanceOf` expect a `HLoadClass` as a second
// input.
return;
}
{
ScopedObjectAccess soa(Thread::Current());
if (!class_rti.GetTypeHandle()->CannotBeAssignedFromOtherTypes()) {
class_rti = ReferenceTypeInfo::Create(class_rti.GetTypeHandle(), /* is_exact= */ false);
}
}
BoundTypeIn(obj, instanceOfTrueBlock, /* start_instruction= */ nullptr, class_rti);
}
void ReferenceTypePropagation::RTPVisitor::SetClassAsTypeInfo(HInstruction* instr,
ObjPtr<mirror::Class> klass,
bool is_exact) {
if (instr->IsInvokeStaticOrDirect() && instr->AsInvokeStaticOrDirect()->IsStringInit()) {
// Calls to String.<init> are replaced with a StringFactory.
if (kIsDebugBuild) {
HInvokeStaticOrDirect* invoke = instr->AsInvokeStaticOrDirect();
ClassLinker* cl = Runtime::Current()->GetClassLinker();
Thread* self = Thread::Current();
StackHandleScope<2> hs(self);
const DexFile& dex_file = *invoke->GetTargetMethod().dex_file;
uint32_t dex_method_index = invoke->GetTargetMethod().index;
Handle<mirror::DexCache> dex_cache(
hs.NewHandle(FindDexCacheWithHint(self, dex_file, hint_dex_cache_)));
// Use a null loader, the target method is in a boot classpath dex file.
Handle<mirror::ClassLoader> loader(hs.NewHandle<mirror::ClassLoader>(nullptr));
ArtMethod* method = cl->ResolveMethod<ClassLinker::ResolveMode::kNoChecks>(
dex_method_index, dex_cache, loader, /* referrer= */ nullptr, kDirect);
DCHECK(method != nullptr);
ObjPtr<mirror::Class> declaring_class = method->GetDeclaringClass();
DCHECK(declaring_class != nullptr);
DCHECK(declaring_class->IsStringClass())
<< "Expected String class: " << declaring_class->PrettyDescriptor();
DCHECK(method->IsConstructor())
<< "Expected String.<init>: " << method->PrettyMethod();
}
instr->SetReferenceTypeInfo(
ReferenceTypeInfo::Create(handle_cache_->GetStringClassHandle(), /* is_exact= */ true));
} else if (IsAdmissible(klass)) {
ReferenceTypeInfo::TypeHandle handle = handle_cache_->NewHandle(klass);
is_exact = is_exact || handle->CannotBeAssignedFromOtherTypes();
instr->SetReferenceTypeInfo(ReferenceTypeInfo::Create(handle, is_exact));
} else {
instr->SetReferenceTypeInfo(instr->GetBlock()->GetGraph()->GetInexactObjectRti());
}
}
void ReferenceTypePropagation::RTPVisitor::VisitDeoptimize(HDeoptimize* instr) {
BoundTypeForClassCheck(instr);
}
void ReferenceTypePropagation::RTPVisitor::UpdateReferenceTypeInfo(HInstruction* instr,
dex::TypeIndex type_idx,
const DexFile& dex_file,
bool is_exact) {
DCHECK_EQ(instr->GetType(), DataType::Type::kReference);
ScopedObjectAccess soa(Thread::Current());
ObjPtr<mirror::DexCache> dex_cache = FindDexCacheWithHint(soa.Self(), dex_file, hint_dex_cache_);
ObjPtr<mirror::Class> klass = Runtime::Current()->GetClassLinker()->LookupResolvedType(
type_idx, dex_cache, class_loader_.Get());
SetClassAsTypeInfo(instr, klass, is_exact);
}
void ReferenceTypePropagation::RTPVisitor::VisitNewInstance(HNewInstance* instr) {
ScopedObjectAccess soa(Thread::Current());
SetClassAsTypeInfo(instr, instr->GetLoadClass()->GetClass().Get(), /* is_exact= */ true);
}
void ReferenceTypePropagation::RTPVisitor::VisitNewArray(HNewArray* instr) {
ScopedObjectAccess soa(Thread::Current());
SetClassAsTypeInfo(instr, instr->GetLoadClass()->GetClass().Get(), /* is_exact= */ true);
}
void ReferenceTypePropagation::RTPVisitor::VisitParameterValue(HParameterValue* instr) {
// We check if the existing type is valid: the inliner may have set it.
if (instr->GetType() == DataType::Type::kReference && !instr->GetReferenceTypeInfo().IsValid()) {
UpdateReferenceTypeInfo(instr,
instr->GetTypeIndex(),
instr->GetDexFile(),
/* is_exact= */ false);
}
}
void ReferenceTypePropagation::RTPVisitor::UpdateFieldAccessTypeInfo(HInstruction* instr,
const FieldInfo& info) {
if (instr->GetType() != DataType::Type::kReference) {
return;
}
ScopedObjectAccess soa(Thread::Current());
ObjPtr<mirror::Class> klass;
// The field is unknown only during tests.
if (info.GetField() != nullptr) {
klass = info.GetField()->LookupResolvedType();
}
SetClassAsTypeInfo(instr, klass, /* is_exact= */ false);
}
void ReferenceTypePropagation::RTPVisitor::VisitInstanceFieldGet(HInstanceFieldGet* instr) {
UpdateFieldAccessTypeInfo(instr, instr->GetFieldInfo());
}
void ReferenceTypePropagation::RTPVisitor::VisitStaticFieldGet(HStaticFieldGet* instr) {
UpdateFieldAccessTypeInfo(instr, instr->GetFieldInfo());
}
void ReferenceTypePropagation::RTPVisitor::VisitUnresolvedInstanceFieldGet(
HUnresolvedInstanceFieldGet* instr) {
// TODO: Use descriptor to get the actual type.
if (instr->GetFieldType() == DataType::Type::kReference) {
instr->SetReferenceTypeInfo(instr->GetBlock()->GetGraph()->GetInexactObjectRti());
}
}
void ReferenceTypePropagation::RTPVisitor::VisitUnresolvedStaticFieldGet(
HUnresolvedStaticFieldGet* instr) {
// TODO: Use descriptor to get the actual type.
if (instr->GetFieldType() == DataType::Type::kReference) {
instr->SetReferenceTypeInfo(instr->GetBlock()->GetGraph()->GetInexactObjectRti());
}
}
void ReferenceTypePropagation::RTPVisitor::VisitLoadClass(HLoadClass* instr) {
ScopedObjectAccess soa(Thread::Current());
if (IsAdmissible(instr->GetClass().Get())) {
instr->SetValidLoadedClassRTI();
}
instr->SetReferenceTypeInfo(
ReferenceTypeInfo::Create(handle_cache_->GetClassClassHandle(), /* is_exact= */ true));
}
void ReferenceTypePropagation::RTPVisitor::VisitInstanceOf(HInstanceOf* instr) {
ScopedObjectAccess soa(Thread::Current());
if (IsAdmissible(instr->GetClass().Get())) {
instr->SetValidTargetClassRTI();
}
}
void ReferenceTypePropagation::RTPVisitor::VisitClinitCheck(HClinitCheck* instr) {
instr->SetReferenceTypeInfo(instr->InputAt(0)->GetReferenceTypeInfo());
}
void ReferenceTypePropagation::RTPVisitor::VisitLoadMethodHandle(HLoadMethodHandle* instr) {
instr->SetReferenceTypeInfo(ReferenceTypeInfo::Create(
handle_cache_->GetMethodHandleClassHandle(),
/* is_exact= */ true));
}
void ReferenceTypePropagation::RTPVisitor::VisitLoadMethodType(HLoadMethodType* instr) {
instr->SetReferenceTypeInfo(
ReferenceTypeInfo::Create(handle_cache_->GetMethodTypeClassHandle(), /* is_exact= */ true));
}
void ReferenceTypePropagation::RTPVisitor::VisitLoadString(HLoadString* instr) {
instr->SetReferenceTypeInfo(
ReferenceTypeInfo::Create(handle_cache_->GetStringClassHandle(), /* is_exact= */ true));
}
void ReferenceTypePropagation::RTPVisitor::VisitLoadException(HLoadException* instr) {
DCHECK(instr->GetBlock()->IsCatchBlock());
TryCatchInformation* catch_info = instr->GetBlock()->GetTryCatchInformation();
if (catch_info->IsValidTypeIndex()) {
UpdateReferenceTypeInfo(instr,
catch_info->GetCatchTypeIndex(),
catch_info->GetCatchDexFile(),
/* is_exact= */ false);
} else {
instr->SetReferenceTypeInfo(
ReferenceTypeInfo::Create(handle_cache_->GetThrowableClassHandle(), /* is_exact= */ false));
}
}
void ReferenceTypePropagation::RTPVisitor::VisitNullCheck(HNullCheck* instr) {
ReferenceTypeInfo parent_rti = instr->InputAt(0)->GetReferenceTypeInfo();
if (parent_rti.IsValid()) {
instr->SetReferenceTypeInfo(parent_rti);
}
}
void ReferenceTypePropagation::RTPVisitor::VisitBoundType(HBoundType* instr) {
ReferenceTypeInfo class_rti = instr->GetUpperBound();
if (class_rti.IsValid()) {
ScopedObjectAccess soa(Thread::Current());
// Narrow the type as much as possible.
HInstruction* obj = instr->InputAt(0);
ReferenceTypeInfo obj_rti = obj->GetReferenceTypeInfo();
if (class_rti.IsExact()) {
instr->SetReferenceTypeInfo(class_rti);
} else if (obj_rti.IsValid()) {
if (class_rti.IsSupertypeOf(obj_rti)) {
// Object type is more specific.
instr->SetReferenceTypeInfo(obj_rti);
} else {
// Upper bound is more specific, or unrelated to the object's type.
// Note that the object might then be exact, and we know the code dominated by this
// bound type is dead. To not confuse potential other optimizations, we mark
// the bound as non-exact.
instr->SetReferenceTypeInfo(
ReferenceTypeInfo::Create(class_rti.GetTypeHandle(), /* is_exact= */ false));
}
} else {
// Object not typed yet. Leave BoundType untyped for now rather than
// assign the type conservatively.
}
instr->SetCanBeNull(obj->CanBeNull() && instr->GetUpperCanBeNull());
} else {
// The owner of the BoundType was already visited. If the class is unresolved,
// the BoundType should have been removed from the data flow and this method
// should remove it from the graph.
DCHECK(!instr->HasUses());
instr->GetBlock()->RemoveInstruction(instr);
}
}
void ReferenceTypePropagation::RTPVisitor::VisitCheckCast(HCheckCast* check_cast) {
HBoundType* bound_type = check_cast->GetNext()->AsBoundType();
if (bound_type == nullptr || bound_type->GetUpperBound().IsValid()) {
// The next instruction is not an uninitialized BoundType. This must be
// an RTP pass after SsaBuilder and we do not need to do anything.
return;
}
DCHECK_EQ(bound_type->InputAt(0), check_cast->InputAt(0));
ScopedObjectAccess soa(Thread::Current());
Handle<mirror::Class> klass = check_cast->GetClass();
if (IsAdmissible(klass.Get())) {
DCHECK(is_first_run_);
check_cast->SetValidTargetClassRTI();
// This is the first run of RTP and class is resolved.
bool is_exact = klass->CannotBeAssignedFromOtherTypes();
bound_type->SetUpperBound(ReferenceTypeInfo::Create(klass, is_exact),
/* CheckCast succeeds for nulls. */ true);
} else {
// This is the first run of RTP and class is unresolved. Remove the binding.
// The instruction itself is removed in VisitBoundType so as to not
// invalidate HInstructionIterator.
bound_type->ReplaceWith(bound_type->InputAt(0));
}
}
void ReferenceTypePropagation::RTPVisitor::VisitPhi(HPhi* phi) {
if (phi->IsDead() || phi->GetType() != DataType::Type::kReference) {
return;
}
if (phi->GetBlock()->IsLoopHeader()) {
// Set the initial type for the phi. Use the non back edge input for reaching
// a fixed point faster.
HInstruction* first_input = phi->InputAt(0);
ReferenceTypeInfo first_input_rti = first_input->GetReferenceTypeInfo();
if (first_input_rti.IsValid() && !first_input->IsNullConstant()) {
phi->SetCanBeNull(first_input->CanBeNull());
phi->SetReferenceTypeInfo(first_input_rti);
}
AddToWorklist(phi);
} else {
// Eagerly compute the type of the phi, for quicker convergence. Note
// that we don't need to add users to the worklist because we are
// doing a reverse post-order visit, therefore either the phi users are
// non-loop phi and will be visited later in the visit, or are loop-phis,
// and they are already in the work list.
UpdateNullability(phi);
UpdateReferenceTypeInfo(phi);
}
}
void ReferenceTypePropagation::FixUpInstructionType(HInstruction* instruction,
VariableSizedHandleScope* handle_scope) {
if (instruction->IsSelect()) {
ScopedObjectAccess soa(Thread::Current());
HandleCache handle_cache(handle_scope);
HSelect* select = instruction->AsSelect();
ReferenceTypeInfo false_rti = select->GetFalseValue()->GetReferenceTypeInfo();
ReferenceTypeInfo true_rti = select->GetTrueValue()->GetReferenceTypeInfo();
select->SetReferenceTypeInfo(MergeTypes(false_rti, true_rti, &handle_cache));
} else {
LOG(FATAL) << "Invalid instruction in FixUpInstructionType";
}
}
ReferenceTypeInfo ReferenceTypePropagation::MergeTypes(const ReferenceTypeInfo& a,
const ReferenceTypeInfo& b,
HandleCache* handle_cache) {
if (!b.IsValid()) {
return a;
}
if (!a.IsValid()) {
return b;
}
bool is_exact = a.IsExact() && b.IsExact();
ReferenceTypeInfo::TypeHandle result_type_handle;
ReferenceTypeInfo::TypeHandle a_type_handle = a.GetTypeHandle();
ReferenceTypeInfo::TypeHandle b_type_handle = b.GetTypeHandle();
bool a_is_interface = a_type_handle->IsInterface();
bool b_is_interface = b_type_handle->IsInterface();
if (a.GetTypeHandle().Get() == b.GetTypeHandle().Get()) {
result_type_handle = a_type_handle;
} else if (a.IsSupertypeOf(b)) {
result_type_handle = a_type_handle;
is_exact = false;
} else if (b.IsSupertypeOf(a)) {
result_type_handle = b_type_handle;
is_exact = false;
} else if (!a_is_interface && !b_is_interface) {
result_type_handle =
handle_cache->NewHandle(a_type_handle->GetCommonSuperClass(b_type_handle));
is_exact = false;
} else {
// This can happen if:
// - both types are interfaces. TODO(calin): implement
// - one is an interface, the other a class, and the type does not implement the interface
// e.g:
// void foo(Interface i, boolean cond) {
// Object o = cond ? i : new Object();
// }
result_type_handle = handle_cache->GetObjectClassHandle();
is_exact = false;
}
return ReferenceTypeInfo::Create(result_type_handle, is_exact);
}
void ReferenceTypePropagation::RTPVisitor::UpdateArrayGet(HArrayGet* instr) {
DCHECK_EQ(DataType::Type::kReference, instr->GetType());
ReferenceTypeInfo parent_rti = instr->InputAt(0)->GetReferenceTypeInfo();
if (!parent_rti.IsValid()) {
return;
}
Handle<mirror::Class> handle = parent_rti.GetTypeHandle();
if (handle->IsObjectArrayClass() && IsAdmissible(handle->GetComponentType())) {
ReferenceTypeInfo::TypeHandle component_handle =
handle_cache_->NewHandle(handle->GetComponentType());
bool is_exact = component_handle->CannotBeAssignedFromOtherTypes();
instr->SetReferenceTypeInfo(ReferenceTypeInfo::Create(component_handle, is_exact));
} else {
// We don't know what the parent actually is, so we fallback to object.
instr->SetReferenceTypeInfo(instr->GetBlock()->GetGraph()->GetInexactObjectRti());
}
}
bool ReferenceTypePropagation::RTPVisitor::UpdateReferenceTypeInfo(HInstruction* instr) {
ScopedObjectAccess soa(Thread::Current());
ReferenceTypeInfo previous_rti = instr->GetReferenceTypeInfo();
if (instr->IsBoundType()) {
UpdateBoundType(instr->AsBoundType());
} else if (instr->IsPhi()) {
UpdatePhi(instr->AsPhi());
} else if (instr->IsNullCheck()) {
ReferenceTypeInfo parent_rti = instr->InputAt(0)->GetReferenceTypeInfo();
if (parent_rti.IsValid()) {
instr->SetReferenceTypeInfo(parent_rti);
}
} else if (instr->IsArrayGet()) {
// TODO: consider if it's worth "looking back" and binding the input object
// to an array type.
UpdateArrayGet(instr->AsArrayGet());
} else {
LOG(FATAL) << "Invalid instruction (should not get here)";
}
return !previous_rti.IsEqual(instr->GetReferenceTypeInfo());
}
void ReferenceTypePropagation::RTPVisitor::VisitInvoke(HInvoke* instr) {
if (instr->GetType() != DataType::Type::kReference) {
return;
}
ScopedObjectAccess soa(Thread::Current());
ArtMethod* method = instr->GetResolvedMethod();
ObjPtr<mirror::Class> klass = (method == nullptr) ? nullptr : method->LookupResolvedReturnType();
SetClassAsTypeInfo(instr, klass, /* is_exact= */ false);
}
void ReferenceTypePropagation::RTPVisitor::VisitArrayGet(HArrayGet* instr) {
if (instr->GetType() != DataType::Type::kReference) {
return;
}
ScopedObjectAccess soa(Thread::Current());
UpdateArrayGet(instr);
if (!instr->GetReferenceTypeInfo().IsValid()) {
worklist_.push_back(instr);
}
}
void ReferenceTypePropagation::RTPVisitor::UpdateBoundType(HBoundType* instr) {
ReferenceTypeInfo input_rti = instr->InputAt(0)->GetReferenceTypeInfo();
if (!input_rti.IsValid()) {
return; // No new info yet.
}
ReferenceTypeInfo upper_bound_rti = instr->GetUpperBound();
if (upper_bound_rti.IsExact()) {
instr->SetReferenceTypeInfo(upper_bound_rti);
} else if (upper_bound_rti.IsSupertypeOf(input_rti)) {
// input is more specific.
instr->SetReferenceTypeInfo(input_rti);
} else {
// upper_bound is more specific or unrelated.
// Note that the object might then be exact, and we know the code dominated by this
// bound type is dead. To not confuse potential other optimizations, we mark
// the bound as non-exact.
instr->SetReferenceTypeInfo(
ReferenceTypeInfo::Create(upper_bound_rti.GetTypeHandle(), /* is_exact= */ false));
}
}
// NullConstant inputs are ignored during merging as they do not provide any useful information.
// If all the inputs are NullConstants then the type of the phi will be set to Object.
void ReferenceTypePropagation::RTPVisitor::UpdatePhi(HPhi* instr) {
DCHECK(instr->IsLive());
HInputsRef inputs = instr->GetInputs();
size_t first_input_index_not_null = 0;
while (first_input_index_not_null < inputs.size() &&
inputs[first_input_index_not_null]->IsNullConstant()) {
first_input_index_not_null++;
}
if (first_input_index_not_null == inputs.size()) {
// All inputs are NullConstants, set the type to object.
// This may happen in the presence of inlining.
instr->SetReferenceTypeInfo(instr->GetBlock()->GetGraph()->GetInexactObjectRti());
return;
}
ReferenceTypeInfo new_rti = instr->InputAt(first_input_index_not_null)->GetReferenceTypeInfo();
if (new_rti.IsValid() && new_rti.IsObjectClass() && !new_rti.IsExact()) {
// Early return if we are Object and inexact.
instr->SetReferenceTypeInfo(new_rti);
return;
}
for (size_t i = first_input_index_not_null + 1; i < inputs.size(); i++) {
if (inputs[i]->IsNullConstant()) {
continue;
}
new_rti = MergeTypes(new_rti, inputs[i]->GetReferenceTypeInfo(), handle_cache_);
if (new_rti.IsValid() && new_rti.IsObjectClass()) {
if (!new_rti.IsExact()) {
break;
} else {
continue;
}
}
}
if (new_rti.IsValid()) {
instr->SetReferenceTypeInfo(new_rti);
}
}
// Re-computes and updates the nullability of the instruction. Returns whether or
// not the nullability was changed.
bool ReferenceTypePropagation::RTPVisitor::UpdateNullability(HInstruction* instr) {
DCHECK((instr->IsPhi() && instr->AsPhi()->IsLive())
|| instr->IsBoundType()
|| instr->IsNullCheck()
|| instr->IsArrayGet());
if (!instr->IsPhi() && !instr->IsBoundType()) {
return false;
}
bool existing_can_be_null = instr->CanBeNull();
if (instr->IsPhi()) {
HPhi* phi = instr->AsPhi();
bool new_can_be_null = false;
for (HInstruction* input : phi->GetInputs()) {
if (input->CanBeNull()) {
new_can_be_null = true;
break;
}
}
phi->SetCanBeNull(new_can_be_null);
} else if (instr->IsBoundType()) {
HBoundType* bound_type = instr->AsBoundType();
bound_type->SetCanBeNull(instr->InputAt(0)->CanBeNull() && bound_type->GetUpperCanBeNull());
}
return existing_can_be_null != instr->CanBeNull();
}
void ReferenceTypePropagation::RTPVisitor::ProcessWorklist() {
while (!worklist_.empty()) {
HInstruction* instruction = worklist_.back();
worklist_.pop_back();
bool updated_nullability = UpdateNullability(instruction);
bool updated_reference_type = UpdateReferenceTypeInfo(instruction);
if (updated_nullability || updated_reference_type) {
AddDependentInstructionsToWorklist(instruction);
}
}
}
void ReferenceTypePropagation::RTPVisitor::AddToWorklist(HInstruction* instruction) {
DCHECK_EQ(instruction->GetType(), DataType::Type::kReference)
<< instruction->DebugName() << ":" << instruction->GetType();
worklist_.push_back(instruction);
}
void ReferenceTypePropagation::RTPVisitor::AddDependentInstructionsToWorklist(
HInstruction* instruction) {
for (const HUseListNode<HInstruction*>& use : instruction->GetUses()) {
HInstruction* user = use.GetUser();
if ((user->IsPhi() && user->AsPhi()->IsLive())
|| user->IsBoundType()
|| user->IsNullCheck()
|| (user->IsArrayGet() && (user->GetType() == DataType::Type::kReference))) {
AddToWorklist(user);
}
}
}
} // namespace art