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/interpreter/bytecode-dead-code-optimizer.h" |
| 6 | |
| 7 | namespace v8 { |
| 8 | namespace internal { |
| 9 | namespace interpreter { |
| 10 | |
| 11 | BytecodeDeadCodeOptimizer::BytecodeDeadCodeOptimizer( |
| 12 | BytecodePipelineStage* next_stage) |
| 13 | : next_stage_(next_stage), exit_seen_in_block_(false) {} |
| 14 | |
| 15 | // override |
| 16 | Handle<BytecodeArray> BytecodeDeadCodeOptimizer::ToBytecodeArray( |
| 17 | int fixed_register_count, int parameter_count, |
| 18 | Handle<FixedArray> handler_table) { |
| 19 | return next_stage_->ToBytecodeArray(fixed_register_count, parameter_count, |
| 20 | handler_table); |
| 21 | } |
| 22 | |
| 23 | // override |
| 24 | void BytecodeDeadCodeOptimizer::Write(BytecodeNode* node) { |
| 25 | // Don't emit dead code. |
| 26 | if (exit_seen_in_block_) return; |
| 27 | |
| 28 | switch (node->bytecode()) { |
| 29 | case Bytecode::kReturn: |
| 30 | case Bytecode::kThrow: |
| 31 | case Bytecode::kReThrow: |
| 32 | exit_seen_in_block_ = true; |
| 33 | break; |
| 34 | default: |
| 35 | break; |
| 36 | } |
| 37 | |
| 38 | next_stage_->Write(node); |
| 39 | } |
| 40 | |
| 41 | // override |
| 42 | void BytecodeDeadCodeOptimizer::WriteJump(BytecodeNode* node, |
| 43 | BytecodeLabel* label) { |
| 44 | // Don't emit dead code. |
| 45 | // TODO(rmcilroy): For forward jumps we could mark the label as dead, thereby |
| 46 | // avoiding emitting dead code when we bind the label. |
| 47 | if (exit_seen_in_block_) return; |
| 48 | |
| 49 | switch (node->bytecode()) { |
| 50 | case Bytecode::kJump: |
| 51 | case Bytecode::kJumpConstant: |
| 52 | exit_seen_in_block_ = true; |
| 53 | break; |
| 54 | default: |
| 55 | break; |
| 56 | } |
| 57 | |
| 58 | next_stage_->WriteJump(node, label); |
| 59 | } |
| 60 | |
| 61 | // override |
| 62 | void BytecodeDeadCodeOptimizer::BindLabel(BytecodeLabel* label) { |
| 63 | next_stage_->BindLabel(label); |
| 64 | exit_seen_in_block_ = false; |
| 65 | } |
| 66 | |
| 67 | // override |
| 68 | void BytecodeDeadCodeOptimizer::BindLabel(const BytecodeLabel& target, |
| 69 | BytecodeLabel* label) { |
| 70 | next_stage_->BindLabel(target, label); |
| 71 | // exit_seen_in_block_ was reset when target was bound, so shouldn't be |
| 72 | // changed here. |
| 73 | } |
| 74 | |
| 75 | } // namespace interpreter |
| 76 | } // namespace internal |
| 77 | } // namespace v8 |