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1 // Copyright 2015 the V8 project authors. All rights reserved. | 1 // Copyright 2015 the V8 project authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #include "src/compiler/bytecode-branch-analysis.h" | 5 #include "src/compiler/bytecode-branch-analysis.h" |
6 | 6 |
7 #include "src/interpreter/bytecode-array-iterator.h" | 7 #include "src/interpreter/bytecode-array-iterator.h" |
8 #include "src/objects-inl.h" | 8 #include "src/objects-inl.h" |
9 | 9 |
10 namespace v8 { | 10 namespace v8 { |
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42 } else { | 42 } else { |
43 back_edge_offsets_.push_back(source_offset); | 43 back_edge_offsets_.push_back(source_offset); |
44 } | 44 } |
45 } | 45 } |
46 | 46 |
47 | 47 |
48 BytecodeBranchAnalysis::BytecodeBranchAnalysis( | 48 BytecodeBranchAnalysis::BytecodeBranchAnalysis( |
49 Handle<BytecodeArray> bytecode_array, Zone* zone) | 49 Handle<BytecodeArray> bytecode_array, Zone* zone) |
50 : branch_infos_(zone), | 50 : branch_infos_(zone), |
51 bytecode_array_(bytecode_array), | 51 bytecode_array_(bytecode_array), |
52 reachable_(bytecode_array->length(), zone), | |
53 zone_(zone) {} | 52 zone_(zone) {} |
54 | 53 |
55 | 54 |
56 void BytecodeBranchAnalysis::Analyze() { | 55 void BytecodeBranchAnalysis::Analyze() { |
57 interpreter::BytecodeArrayIterator iterator(bytecode_array()); | 56 interpreter::BytecodeArrayIterator iterator(bytecode_array()); |
58 AnalyzeExceptionHandlers(); | |
59 bool reachable = true; | |
60 while (!iterator.done()) { | 57 while (!iterator.done()) { |
61 interpreter::Bytecode bytecode = iterator.current_bytecode(); | 58 interpreter::Bytecode bytecode = iterator.current_bytecode(); |
62 int current_offset = iterator.current_offset(); | 59 int current_offset = iterator.current_offset(); |
63 // All bytecode basic blocks are generated to be forward reachable | 60 if (interpreter::Bytecodes::IsJump(bytecode)) { |
64 // and may also be backward reachable. Hence if there's a forward | 61 AddBranch(current_offset, iterator.GetJumpTargetOffset()); |
65 // branch targetting here the code becomes reachable. | |
66 reachable = reachable || forward_branches_target(current_offset); | |
67 // Some bytecode basic blocks are reachable through a side-entry | |
68 // (e.g. exception handler), which has been represented in the | |
69 // bit-vector by a corresponding pre-pass. | |
70 reachable = reachable || reachable_.Contains(current_offset); | |
71 if (reachable) { | |
72 reachable_.Add(current_offset); | |
73 if (interpreter::Bytecodes::IsConditionalJump(bytecode)) { | |
74 // Only the branch is recorded, the forward path falls through | |
75 // and is handled as normal bytecode data flow. | |
76 AddBranch(current_offset, iterator.GetJumpTargetOffset()); | |
77 } else if (interpreter::Bytecodes::IsJump(bytecode)) { | |
78 // Unless the branch targets the next bytecode it's not | |
79 // reachable. If it targets the next bytecode the check at the | |
80 // start of the loop will set the reachable flag. | |
81 AddBranch(current_offset, iterator.GetJumpTargetOffset()); | |
82 reachable = false; | |
83 } else if (interpreter::Bytecodes::IsJumpOrReturn(bytecode)) { | |
84 DCHECK_EQ(bytecode, interpreter::Bytecode::kReturn); | |
85 reachable = false; | |
86 } | |
87 } | 62 } |
88 iterator.Advance(); | 63 iterator.Advance(); |
89 } | 64 } |
90 } | 65 } |
91 | 66 |
92 | 67 |
93 const ZoneVector<int>* BytecodeBranchAnalysis::BackwardBranchesTargetting( | 68 const ZoneVector<int>* BytecodeBranchAnalysis::BackwardBranchesTargetting( |
94 int offset) const { | 69 int offset) const { |
95 auto iterator = branch_infos_.find(offset); | 70 auto iterator = branch_infos_.find(offset); |
96 if (branch_infos_.end() != iterator) { | 71 if (branch_infos_.end() != iterator) { |
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116 auto iterator = branch_infos_.find(target_offset); | 91 auto iterator = branch_infos_.find(target_offset); |
117 if (branch_infos_.end() == iterator) { | 92 if (branch_infos_.end() == iterator) { |
118 branch_info = new (zone()) BytecodeBranchInfo(zone()); | 93 branch_info = new (zone()) BytecodeBranchInfo(zone()); |
119 branch_infos_.insert(std::make_pair(target_offset, branch_info)); | 94 branch_infos_.insert(std::make_pair(target_offset, branch_info)); |
120 } else { | 95 } else { |
121 branch_info = iterator->second; | 96 branch_info = iterator->second; |
122 } | 97 } |
123 branch_info->AddBranch(source_offset, target_offset); | 98 branch_info->AddBranch(source_offset, target_offset); |
124 } | 99 } |
125 | 100 |
126 void BytecodeBranchAnalysis::AnalyzeExceptionHandlers() { | |
127 HandlerTable* table = HandlerTable::cast(bytecode_array()->handler_table()); | |
128 for (int i = 0; i < table->NumberOfRangeEntries(); ++i) { | |
129 reachable_.Add(table->GetRangeHandler(i)); | |
130 } | |
131 } | |
132 | |
133 } // namespace compiler | 101 } // namespace compiler |
134 } // namespace internal | 102 } // namespace internal |
135 } // namespace v8 | 103 } // namespace v8 |
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