Calin Juravle | 10e244f | 2015-01-26 18:54:32 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2015 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | #include "reference_type_propagation.h" |
| 18 | |
| 19 | namespace art { |
| 20 | |
Calin Juravle | 10e244f | 2015-01-26 18:54:32 +0000 | [diff] [blame] | 21 | void ReferenceTypePropagation::Run() { |
| 22 | // Compute null status for instructions. |
| 23 | |
| 24 | // To properly propagate not-null info we need to visit in the dominator-based order. |
| 25 | // Reverse post order guarantees a node's dominators are visited first. |
| 26 | // We take advantage of this order in `VisitBasicBlock`. |
| 27 | for (HReversePostOrderIterator it(*graph_); !it.Done(); it.Advance()) { |
| 28 | VisitBasicBlock(it.Current()); |
| 29 | } |
| 30 | ProcessWorklist(); |
| 31 | } |
| 32 | |
| 33 | // Re-computes and updates the nullability of the instruction. Returns whether or |
| 34 | // not the nullability was changed. |
| 35 | bool ReferenceTypePropagation::UpdateNullability(HPhi* phi) { |
| 36 | bool existing_can_be_null = phi->CanBeNull(); |
| 37 | bool new_can_be_null = false; |
| 38 | for (size_t i = 0; i < phi->InputCount(); i++) { |
| 39 | new_can_be_null |= phi->InputAt(i)->CanBeNull(); |
| 40 | } |
| 41 | phi->SetCanBeNull(new_can_be_null); |
| 42 | |
| 43 | return existing_can_be_null != new_can_be_null; |
| 44 | } |
| 45 | |
| 46 | |
| 47 | void ReferenceTypePropagation::VisitBasicBlock(HBasicBlock* block) { |
| 48 | if (block->IsLoopHeader()) { |
| 49 | for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) { |
| 50 | // Set the initial type for the phi. Use the non back edge input for reaching |
| 51 | // a fixed point faster. |
| 52 | HPhi* phi = it.Current()->AsPhi(); |
Nicolas Geoffray | d6138ef | 2015-02-18 14:48:53 +0000 | [diff] [blame^] | 53 | if (phi->GetType() == Primitive::kPrimNot) { |
| 54 | AddToWorklist(phi); |
| 55 | phi->SetCanBeNull(phi->InputAt(0)->CanBeNull()); |
| 56 | } |
Calin Juravle | 10e244f | 2015-01-26 18:54:32 +0000 | [diff] [blame] | 57 | } |
| 58 | } else { |
| 59 | for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) { |
| 60 | // Eagerly compute the type of the phi, for quicker convergence. Note |
| 61 | // that we don't need to add users to the worklist because we are |
| 62 | // doing a reverse post-order visit, therefore either the phi users are |
| 63 | // non-loop phi and will be visited later in the visit, or are loop-phis, |
| 64 | // and they are already in the work list. |
Nicolas Geoffray | d6138ef | 2015-02-18 14:48:53 +0000 | [diff] [blame^] | 65 | HPhi* phi = it.Current()->AsPhi(); |
| 66 | if (phi->GetType() == Primitive::kPrimNot) { |
| 67 | UpdateNullability(phi); |
| 68 | } |
Calin Juravle | 10e244f | 2015-01-26 18:54:32 +0000 | [diff] [blame] | 69 | } |
| 70 | } |
| 71 | } |
| 72 | |
| 73 | void ReferenceTypePropagation::ProcessWorklist() { |
| 74 | while (!worklist_.IsEmpty()) { |
| 75 | HPhi* instruction = worklist_.Pop(); |
| 76 | if (UpdateNullability(instruction)) { |
| 77 | AddDependentInstructionsToWorklist(instruction); |
| 78 | } |
| 79 | } |
| 80 | } |
| 81 | |
| 82 | void ReferenceTypePropagation::AddToWorklist(HPhi* instruction) { |
Nicolas Geoffray | d6138ef | 2015-02-18 14:48:53 +0000 | [diff] [blame^] | 83 | DCHECK_EQ(instruction->GetType(), Primitive::kPrimNot); |
Calin Juravle | 10e244f | 2015-01-26 18:54:32 +0000 | [diff] [blame] | 84 | worklist_.Add(instruction); |
| 85 | } |
| 86 | |
| 87 | void ReferenceTypePropagation::AddDependentInstructionsToWorklist(HPhi* instruction) { |
| 88 | for (HUseIterator<HInstruction*> it(instruction->GetUses()); !it.Done(); it.Advance()) { |
| 89 | HPhi* phi = it.Current()->GetUser()->AsPhi(); |
| 90 | if (phi != nullptr) { |
| 91 | AddToWorklist(phi); |
| 92 | } |
| 93 | } |
| 94 | } |
| 95 | |
| 96 | } // namespace art |