| /* |
| * 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 "class_linker.h" |
| #include "mirror/class-inl.h" |
| #include "mirror/dex_cache.h" |
| #include "scoped_thread_state_change.h" |
| |
| namespace art { |
| |
| void ReferenceTypePropagation::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 (HReversePostOrderIterator it(*graph_); !it.Done(); it.Advance()) { |
| VisitBasicBlock(it.Current()); |
| } |
| ProcessWorklist(); |
| } |
| |
| void ReferenceTypePropagation::VisitBasicBlock(HBasicBlock* block) { |
| // TODO: handle other instructions that give type info |
| // (NewArray/Call/Field accesses/array accesses) |
| |
| // Initialize exact types first for faster convergence. |
| for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) { |
| HInstruction* instr = it.Current(); |
| if (instr->IsNewInstance()) { |
| VisitNewInstance(instr->AsNewInstance()); |
| } else if (instr->IsLoadClass()) { |
| VisitLoadClass(instr->AsLoadClass()); |
| } |
| } |
| |
| // Handle Phis. |
| for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) { |
| VisitPhi(it.Current()->AsPhi()); |
| } |
| |
| // Add extra nodes to bound types. |
| BoundTypeForIfNotNull(block); |
| BoundTypeForIfInstanceOf(block); |
| } |
| |
| void ReferenceTypePropagation::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; |
| } |
| |
| // 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; |
| HBasicBlock* notNullBlock = ifInput->IsNotEqual() |
| ? ifInstruction->IfTrueSuccessor() |
| : ifInstruction->IfFalseSuccessor(); |
| |
| for (HUseIterator<HInstruction*> it(obj->GetUses()); !it.Done(); it.Advance()) { |
| HInstruction* user = it.Current()->GetUser(); |
| if (notNullBlock->Dominates(user->GetBlock())) { |
| if (bound_type == nullptr) { |
| bound_type = new (graph_->GetArena()) HBoundType(obj, ReferenceTypeInfo::CreateTop(false)); |
| notNullBlock->InsertInstructionBefore(bound_type, notNullBlock->GetFirstInstruction()); |
| } |
| user->ReplaceInput(bound_type, it.Current()->GetIndex()); |
| } |
| } |
| } |
| |
| // 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::BoundTypeForIfInstanceOf(HBasicBlock* block) { |
| HIf* ifInstruction = block->GetLastInstruction()->AsIf(); |
| if (ifInstruction == nullptr) { |
| return; |
| } |
| HInstruction* ifInput = ifInstruction->InputAt(0); |
| HInstruction* instanceOf = nullptr; |
| HBasicBlock* instanceOfTrueBlock = nullptr; |
| |
| // The instruction simplifier has transformed: |
| // - `if (a instanceof A)` into an HIf with an HInstanceOf input |
| // - `if (!(a instanceof A)` into an HIf with an HBooleanNot input (which in turn |
| // has an HInstanceOf input) |
| // So we should not see the usual HEqual here. |
| if (ifInput->IsInstanceOf()) { |
| instanceOf = ifInput; |
| instanceOfTrueBlock = ifInstruction->IfTrueSuccessor(); |
| } else if (ifInput->IsBooleanNot() && ifInput->InputAt(0)->IsInstanceOf()) { |
| instanceOf = ifInput->InputAt(0); |
| instanceOfTrueBlock = ifInstruction->IfFalseSuccessor(); |
| } else { |
| return; |
| } |
| |
| // 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; |
| |
| HInstruction* obj = instanceOf->InputAt(0); |
| for (HUseIterator<HInstruction*> it(obj->GetUses()); !it.Done(); it.Advance()) { |
| HInstruction* user = it.Current()->GetUser(); |
| if (instanceOfTrueBlock->Dominates(user->GetBlock())) { |
| if (bound_type == nullptr) { |
| HLoadClass* load_class = instanceOf->InputAt(1)->AsLoadClass(); |
| |
| ReferenceTypeInfo obj_rti = obj->GetReferenceTypeInfo(); |
| ReferenceTypeInfo class_rti = load_class->GetLoadedClassRTI(); |
| bound_type = new (graph_->GetArena()) HBoundType(obj, class_rti); |
| |
| // Narrow the type as much as possible. |
| { |
| ScopedObjectAccess soa(Thread::Current()); |
| if (!load_class->IsResolved() || class_rti.IsSupertypeOf(obj_rti)) { |
| bound_type->SetReferenceTypeInfo(obj_rti); |
| } else { |
| bound_type->SetReferenceTypeInfo( |
| ReferenceTypeInfo::Create(class_rti.GetTypeHandle(), /* is_exact */ false)); |
| } |
| } |
| |
| instanceOfTrueBlock->InsertInstructionBefore( |
| bound_type, instanceOfTrueBlock->GetFirstInstruction()); |
| } |
| user->ReplaceInput(bound_type, it.Current()->GetIndex()); |
| } |
| } |
| } |
| |
| void ReferenceTypePropagation::VisitNewInstance(HNewInstance* instr) { |
| ScopedObjectAccess soa(Thread::Current()); |
| mirror::DexCache* dex_cache = |
| Runtime::Current()->GetClassLinker()->FindDexCache(instr->GetDexFile()); |
| // Get type from dex cache assuming it was populated by the verifier. |
| mirror::Class* resolved_class = dex_cache->GetResolvedType(instr->GetTypeIndex()); |
| if (resolved_class != nullptr) { |
| MutableHandle<mirror::Class> handle = handles_->NewHandle(resolved_class); |
| instr->SetReferenceTypeInfo(ReferenceTypeInfo::Create(handle, true)); |
| } |
| } |
| |
| void ReferenceTypePropagation::VisitLoadClass(HLoadClass* instr) { |
| ScopedObjectAccess soa(Thread::Current()); |
| mirror::DexCache* dex_cache = |
| Runtime::Current()->GetClassLinker()->FindDexCache(instr->GetDexFile()); |
| // Get type from dex cache assuming it was populated by the verifier. |
| mirror::Class* resolved_class = dex_cache->GetResolvedType(instr->GetTypeIndex()); |
| if (resolved_class != nullptr) { |
| Handle<mirror::Class> handle = handles_->NewHandle(resolved_class); |
| instr->SetLoadedClassRTI(ReferenceTypeInfo::Create(handle, /* is_exact */ true)); |
| } |
| Handle<mirror::Class> class_handle = handles_->NewHandle(mirror::Class::GetJavaLangClass()); |
| instr->SetReferenceTypeInfo(ReferenceTypeInfo::Create(class_handle, /* is_exact */ true)); |
| } |
| |
| void ReferenceTypePropagation::VisitPhi(HPhi* phi) { |
| if (phi->GetType() != Primitive::kPrimNot) { |
| return; |
| } |
| |
| if (phi->GetBlock()->IsLoopHeader()) { |
| // Set the initial type for the phi. Use the non back edge input for reaching |
| // a fixed point faster. |
| AddToWorklist(phi); |
| phi->SetCanBeNull(phi->InputAt(0)->CanBeNull()); |
| phi->SetReferenceTypeInfo(phi->InputAt(0)->GetReferenceTypeInfo()); |
| } 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); |
| } |
| } |
| |
| ReferenceTypeInfo ReferenceTypePropagation::MergeTypes(const ReferenceTypeInfo& a, |
| const ReferenceTypeInfo& b) { |
| bool is_exact = a.IsExact() && b.IsExact(); |
| bool is_top = a.IsTop() || b.IsTop(); |
| Handle<mirror::Class> type_handle; |
| |
| if (!is_top) { |
| if (a.GetTypeHandle().Get() == b.GetTypeHandle().Get()) { |
| type_handle = a.GetTypeHandle(); |
| } else if (a.IsSupertypeOf(b)) { |
| type_handle = a.GetTypeHandle(); |
| is_exact = false; |
| } else if (b.IsSupertypeOf(a)) { |
| type_handle = b.GetTypeHandle(); |
| is_exact = false; |
| } else { |
| // TODO: Find a common super class. |
| is_top = true; |
| is_exact = false; |
| } |
| } |
| |
| return is_top |
| ? ReferenceTypeInfo::CreateTop(is_exact) |
| : ReferenceTypeInfo::Create(type_handle, is_exact); |
| } |
| |
| bool ReferenceTypePropagation::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 { |
| LOG(FATAL) << "Invalid instruction (should not get here)"; |
| } |
| |
| return !previous_rti.IsEqual(instr->GetReferenceTypeInfo()); |
| } |
| |
| void ReferenceTypePropagation::UpdateBoundType(HBoundType* instr) { |
| ReferenceTypeInfo new_rti = instr->InputAt(0)->GetReferenceTypeInfo(); |
| // Be sure that we don't go over the bounded type. |
| ReferenceTypeInfo bound_rti = instr->GetBoundType(); |
| if (!bound_rti.IsSupertypeOf(new_rti)) { |
| new_rti = bound_rti; |
| } |
| instr->SetReferenceTypeInfo(new_rti); |
| } |
| |
| void ReferenceTypePropagation::UpdatePhi(HPhi* instr) { |
| ReferenceTypeInfo new_rti = instr->InputAt(0)->GetReferenceTypeInfo(); |
| if (new_rti.IsTop() && !new_rti.IsExact()) { |
| // Early return if we are Top and inexact. |
| instr->SetReferenceTypeInfo(new_rti); |
| return; |
| } |
| for (size_t i = 1; i < instr->InputCount(); i++) { |
| new_rti = MergeTypes(new_rti, instr->InputAt(i)->GetReferenceTypeInfo()); |
| if (new_rti.IsTop()) { |
| if (!new_rti.IsExact()) { |
| break; |
| } else { |
| continue; |
| } |
| } |
| } |
| instr->SetReferenceTypeInfo(new_rti); |
| } |
| |
| // Re-computes and updates the nullability of the instruction. Returns whether or |
| // not the nullability was changed. |
| bool ReferenceTypePropagation::UpdateNullability(HInstruction* instr) { |
| DCHECK(instr->IsPhi() || instr->IsBoundType()); |
| |
| if (!instr->IsPhi()) { |
| return false; |
| } |
| |
| HPhi* phi = instr->AsPhi(); |
| bool existing_can_be_null = phi->CanBeNull(); |
| bool new_can_be_null = false; |
| for (size_t i = 0; i < phi->InputCount(); i++) { |
| new_can_be_null |= phi->InputAt(i)->CanBeNull(); |
| } |
| phi->SetCanBeNull(new_can_be_null); |
| |
| return existing_can_be_null != new_can_be_null; |
| } |
| |
| void ReferenceTypePropagation::ProcessWorklist() { |
| while (!worklist_.IsEmpty()) { |
| HInstruction* instruction = worklist_.Pop(); |
| if (UpdateNullability(instruction) || UpdateReferenceTypeInfo(instruction)) { |
| AddDependentInstructionsToWorklist(instruction); |
| } |
| } |
| } |
| |
| void ReferenceTypePropagation::AddToWorklist(HInstruction* instruction) { |
| DCHECK_EQ(instruction->GetType(), Primitive::kPrimNot) << instruction->GetType(); |
| worklist_.Add(instruction); |
| } |
| |
| void ReferenceTypePropagation::AddDependentInstructionsToWorklist(HInstruction* instruction) { |
| for (HUseIterator<HInstruction*> it(instruction->GetUses()); !it.Done(); it.Advance()) { |
| HInstruction* user = it.Current()->GetUser(); |
| if (user->IsPhi() || user->IsBoundType()) { |
| AddToWorklist(user); |
| } |
| } |
| } |
| } // namespace art |