Ben Murdoch | 61f157c | 2016-09-16 13:49:30 +0100 | [diff] [blame] | 1 | // Copyright 2016 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #include "src/compiler/checkpoint-elimination.h" |
| 6 | |
| 7 | #include "src/compiler/node-properties.h" |
| 8 | |
| 9 | namespace v8 { |
| 10 | namespace internal { |
| 11 | namespace compiler { |
| 12 | |
| 13 | CheckpointElimination::CheckpointElimination(Editor* editor) |
| 14 | : AdvancedReducer(editor) {} |
| 15 | |
| 16 | namespace { |
| 17 | |
| 18 | // The given checkpoint is redundant if it is effect-wise dominated by another |
| 19 | // checkpoint and there is no observable write in between. For now we consider |
| 20 | // a linear effect chain only instead of true effect-wise dominance. |
| 21 | bool IsRedundantCheckpoint(Node* node) { |
| 22 | Node* effect = NodeProperties::GetEffectInput(node); |
| 23 | while (effect->op()->HasProperty(Operator::kNoWrite) && |
| 24 | effect->op()->EffectInputCount() == 1) { |
| 25 | if (effect->opcode() == IrOpcode::kCheckpoint) return true; |
| 26 | effect = NodeProperties::GetEffectInput(effect); |
| 27 | } |
| 28 | return false; |
| 29 | } |
| 30 | |
| 31 | } // namespace |
| 32 | |
| 33 | Reduction CheckpointElimination::Reduce(Node* node) { |
| 34 | if (node->opcode() != IrOpcode::kCheckpoint) return NoChange(); |
| 35 | if (IsRedundantCheckpoint(node)) { |
| 36 | return Replace(NodeProperties::GetEffectInput(node)); |
| 37 | } |
| 38 | return NoChange(); |
| 39 | } |
| 40 | |
| 41 | } // namespace compiler |
| 42 | } // namespace internal |
| 43 | } // namespace v8 |