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| 1 // Copyright 2011 the V8 project authors. All rights reserved. |
| 2 // Redistribution and use in source and binary forms, with or without |
| 3 // modification, are permitted provided that the following conditions are |
| 4 // met: |
| 5 // |
| 6 // * Redistributions of source code must retain the above copyright |
| 7 // notice, this list of conditions and the following disclaimer. |
| 8 // * Redistributions in binary form must reproduce the above |
| 9 // copyright notice, this list of conditions and the following |
| 10 // disclaimer in the documentation and/or other materials provided |
| 11 // with the distribution. |
| 12 // * Neither the name of Google Inc. nor the names of its |
| 13 // contributors may be used to endorse or promote products derived |
| 14 // from this software without specific prior written permission. |
| 15 // |
| 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 27 |
| 28 #include "lithium.h" |
| 29 |
| 30 namespace v8 { |
| 31 namespace internal { |
| 32 |
| 33 |
| 34 class LGapNode: public ZoneObject { |
| 35 public: |
| 36 explicit LGapNode(LOperand* operand) |
| 37 : operand_(operand), resolved_(false), visited_id_(-1) { } |
| 38 |
| 39 LOperand* operand() const { return operand_; } |
| 40 bool IsResolved() const { return !IsAssigned() || resolved_; } |
| 41 void MarkResolved() { |
| 42 ASSERT(!IsResolved()); |
| 43 resolved_ = true; |
| 44 } |
| 45 int visited_id() const { return visited_id_; } |
| 46 void set_visited_id(int id) { |
| 47 ASSERT(id > visited_id_); |
| 48 visited_id_ = id; |
| 49 } |
| 50 |
| 51 bool IsAssigned() const { return assigned_from_.is_set(); } |
| 52 LGapNode* assigned_from() const { return assigned_from_.get(); } |
| 53 void set_assigned_from(LGapNode* n) { assigned_from_.set(n); } |
| 54 |
| 55 private: |
| 56 LOperand* operand_; |
| 57 SetOncePointer<LGapNode> assigned_from_; |
| 58 bool resolved_; |
| 59 int visited_id_; |
| 60 }; |
| 61 |
| 62 |
| 63 LGapResolver::LGapResolver(const ZoneList<LMoveOperands>* moves, |
| 64 LOperand* marker_operand) |
| 65 : nodes_(4), |
| 66 identified_cycles_(4), |
| 67 result_(4), |
| 68 marker_operand_(marker_operand), |
| 69 next_visited_id_(0) { |
| 70 for (int i = 0; i < moves->length(); ++i) { |
| 71 LMoveOperands move = moves->at(i); |
| 72 if (!move.IsRedundant()) RegisterMove(move); |
| 73 } |
| 74 } |
| 75 |
| 76 |
| 77 const ZoneList<LMoveOperands>* LGapResolver::ResolveInReverseOrder() { |
| 78 for (int i = 0; i < identified_cycles_.length(); ++i) { |
| 79 ResolveCycle(identified_cycles_[i]); |
| 80 } |
| 81 |
| 82 int unresolved_nodes; |
| 83 do { |
| 84 unresolved_nodes = 0; |
| 85 for (int j = 0; j < nodes_.length(); j++) { |
| 86 LGapNode* node = nodes_[j]; |
| 87 if (!node->IsResolved() && node->assigned_from()->IsResolved()) { |
| 88 AddResultMove(node->assigned_from(), node); |
| 89 node->MarkResolved(); |
| 90 } |
| 91 if (!node->IsResolved()) ++unresolved_nodes; |
| 92 } |
| 93 } while (unresolved_nodes > 0); |
| 94 return &result_; |
| 95 } |
| 96 |
| 97 |
| 98 void LGapResolver::AddResultMove(LGapNode* from, LGapNode* to) { |
| 99 AddResultMove(from->operand(), to->operand()); |
| 100 } |
| 101 |
| 102 |
| 103 void LGapResolver::AddResultMove(LOperand* from, LOperand* to) { |
| 104 result_.Add(LMoveOperands(from, to)); |
| 105 } |
| 106 |
| 107 |
| 108 void LGapResolver::ResolveCycle(LGapNode* start) { |
| 109 ZoneList<LOperand*> circle_operands(8); |
| 110 circle_operands.Add(marker_operand_); |
| 111 LGapNode* cur = start; |
| 112 do { |
| 113 cur->MarkResolved(); |
| 114 circle_operands.Add(cur->operand()); |
| 115 cur = cur->assigned_from(); |
| 116 } while (cur != start); |
| 117 circle_operands.Add(marker_operand_); |
| 118 |
| 119 for (int i = circle_operands.length() - 1; i > 0; --i) { |
| 120 LOperand* from = circle_operands[i]; |
| 121 LOperand* to = circle_operands[i - 1]; |
| 122 AddResultMove(from, to); |
| 123 } |
| 124 } |
| 125 |
| 126 |
| 127 bool LGapResolver::CanReach(LGapNode* a, LGapNode* b, int visited_id) { |
| 128 ASSERT(a != b); |
| 129 LGapNode* cur = a; |
| 130 while (cur != b && cur->visited_id() != visited_id && cur->IsAssigned()) { |
| 131 cur->set_visited_id(visited_id); |
| 132 cur = cur->assigned_from(); |
| 133 } |
| 134 |
| 135 return cur == b; |
| 136 } |
| 137 |
| 138 |
| 139 bool LGapResolver::CanReach(LGapNode* a, LGapNode* b) { |
| 140 ASSERT(a != b); |
| 141 return CanReach(a, b, next_visited_id_++); |
| 142 } |
| 143 |
| 144 |
| 145 void LGapResolver::RegisterMove(LMoveOperands move) { |
| 146 if (move.from()->IsConstantOperand()) { |
| 147 // Constant moves should be last in the machine code. Therefore add them |
| 148 // first to the result set. |
| 149 AddResultMove(move.from(), move.to()); |
| 150 } else { |
| 151 LGapNode* from = LookupNode(move.from()); |
| 152 LGapNode* to = LookupNode(move.to()); |
| 153 if (to->IsAssigned() && to->assigned_from() == from) { |
| 154 move.Eliminate(); |
| 155 return; |
| 156 } |
| 157 ASSERT(!to->IsAssigned()); |
| 158 if (CanReach(from, to)) { |
| 159 // This introduces a circle. Save. |
| 160 identified_cycles_.Add(from); |
| 161 } |
| 162 to->set_assigned_from(from); |
| 163 } |
| 164 } |
| 165 |
| 166 |
| 167 LGapNode* LGapResolver::LookupNode(LOperand* operand) { |
| 168 for (int i = 0; i < nodes_.length(); ++i) { |
| 169 if (nodes_[i]->operand()->Equals(operand)) return nodes_[i]; |
| 170 } |
| 171 |
| 172 // No node found => create a new one. |
| 173 LGapNode* result = new LGapNode(operand); |
| 174 nodes_.Add(result); |
| 175 return result; |
| 176 } |
| 177 |
| 178 |
| 179 } } // namespace v8::internal |
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