1 // Copyright 2013 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 #ifndef V8_COMPILER_SCHEDULE_H_
6 #define V8_COMPILER_SCHEDULE_H_
7
8 #include <iosfwd>
9
10 #include "src/base/compiler-specific.h"
11 #include "src/globals.h"
12 #include "src/zone/zone-containers.h"
13
14 namespace v8 {
15 namespace internal {
16 namespace compiler {
17
18 // Forward declarations.
19 class BasicBlock;
20 class BasicBlockInstrumentor;
21 class Node;
22
23 typedef ZoneVector<BasicBlock*> BasicBlockVector;
24 typedef ZoneVector<Node*> NodeVector;
25
26 // A basic block contains an ordered list of nodes and ends with a control
27 // node. Note that if a basic block has phis, then all phis must appear as the
28 // first nodes in the block.
29 class V8_EXPORT_PRIVATE BasicBlock final
NON_EXPORTED_BASE(ZoneObject)30 : public NON_EXPORTED_BASE(ZoneObject) {
31 public:
32 // Possible control nodes that can end a block.
33 enum Control {
34 kNone, // Control not initialized yet.
35 kGoto, // Goto a single successor block.
36 kCall, // Call with continuation as first successor, exception
37 // second.
38 kBranch, // Branch if true to first successor, otherwise second.
39 kSwitch, // Table dispatch to one of the successor blocks.
40 kDeoptimize, // Return a value from this method.
41 kTailCall, // Tail call another method from this method.
42 kReturn, // Return a value from this method.
43 kThrow // Throw an exception.
44 };
45
46 class Id {
47 public:
48 int ToInt() const { return static_cast<int>(index_); }
49 size_t ToSize() const { return index_; }
50 static Id FromSize(size_t index) { return Id(index); }
51 static Id FromInt(int index) { return Id(static_cast<size_t>(index)); }
52
53 private:
54 explicit Id(size_t index) : index_(index) {}
55 size_t index_;
56 };
57
58 BasicBlock(Zone* zone, Id id);
59
60 Id id() const { return id_; }
61 #if DEBUG
62 void set_debug_info(AssemblerDebugInfo debug_info) {
63 debug_info_ = debug_info;
64 }
65 AssemblerDebugInfo debug_info() const { return debug_info_; }
66 #endif // DEBUG
67
68 void Print();
69
70 // Predecessors.
71 BasicBlockVector& predecessors() { return predecessors_; }
72 const BasicBlockVector& predecessors() const { return predecessors_; }
73 size_t PredecessorCount() const { return predecessors_.size(); }
74 BasicBlock* PredecessorAt(size_t index) { return predecessors_[index]; }
75 void ClearPredecessors() { predecessors_.clear(); }
76 void AddPredecessor(BasicBlock* predecessor);
77
78 // Successors.
79 BasicBlockVector& successors() { return successors_; }
80 const BasicBlockVector& successors() const { return successors_; }
81 size_t SuccessorCount() const { return successors_.size(); }
82 BasicBlock* SuccessorAt(size_t index) { return successors_[index]; }
83 void ClearSuccessors() { successors_.clear(); }
84 void AddSuccessor(BasicBlock* successor);
85
86 // Nodes in the basic block.
87 typedef Node* value_type;
88 bool empty() const { return nodes_.empty(); }
89 size_t size() const { return nodes_.size(); }
90 Node* NodeAt(size_t index) { return nodes_[index]; }
91 size_t NodeCount() const { return nodes_.size(); }
92
93 value_type& front() { return nodes_.front(); }
94 value_type const& front() const { return nodes_.front(); }
95
96 typedef NodeVector::iterator iterator;
97 iterator begin() { return nodes_.begin(); }
98 iterator end() { return nodes_.end(); }
99
100 void RemoveNode(iterator it) { nodes_.erase(it); }
101
102 typedef NodeVector::const_iterator const_iterator;
103 const_iterator begin() const { return nodes_.begin(); }
104 const_iterator end() const { return nodes_.end(); }
105
106 typedef NodeVector::reverse_iterator reverse_iterator;
107 reverse_iterator rbegin() { return nodes_.rbegin(); }
108 reverse_iterator rend() { return nodes_.rend(); }
109
110 void AddNode(Node* node);
111 template <class InputIterator>
112 void InsertNodes(iterator insertion_point, InputIterator insertion_start,
113 InputIterator insertion_end) {
114 nodes_.insert(insertion_point, insertion_start, insertion_end);
115 }
116
117 // Accessors.
118 Control control() const { return control_; }
119 void set_control(Control control);
120
121 Node* control_input() const { return control_input_; }
122 void set_control_input(Node* control_input);
123
124 bool deferred() const { return deferred_; }
125 void set_deferred(bool deferred) { deferred_ = deferred; }
126
127 int32_t dominator_depth() const { return dominator_depth_; }
128 void set_dominator_depth(int32_t depth) { dominator_depth_ = depth; }
129
130 BasicBlock* dominator() const { return dominator_; }
131 void set_dominator(BasicBlock* dominator) { dominator_ = dominator; }
132
133 BasicBlock* rpo_next() const { return rpo_next_; }
134 void set_rpo_next(BasicBlock* rpo_next) { rpo_next_ = rpo_next; }
135
136 BasicBlock* loop_header() const { return loop_header_; }
137 void set_loop_header(BasicBlock* loop_header);
138
139 BasicBlock* loop_end() const { return loop_end_; }
140 void set_loop_end(BasicBlock* loop_end);
141
142 int32_t loop_depth() const { return loop_depth_; }
143 void set_loop_depth(int32_t loop_depth);
144
145 int32_t loop_number() const { return loop_number_; }
146 void set_loop_number(int32_t loop_number) { loop_number_ = loop_number; }
147
148 int32_t rpo_number() const { return rpo_number_; }
149 void set_rpo_number(int32_t rpo_number);
150
151 // Loop membership helpers.
152 inline bool IsLoopHeader() const { return loop_end_ != nullptr; }
153 bool LoopContains(BasicBlock* block) const;
154
155 // Computes the immediate common dominator of {b1} and {b2}. The worst time
156 // complexity is O(N) where N is the height of the dominator tree.
157 static BasicBlock* GetCommonDominator(BasicBlock* b1, BasicBlock* b2);
158
159 private:
160 int32_t loop_number_; // loop number of the block.
161 int32_t rpo_number_; // special RPO number of the block.
162 bool deferred_; // true if the block contains deferred code.
163 int32_t dominator_depth_; // Depth within the dominator tree.
164 BasicBlock* dominator_; // Immediate dominator of the block.
165 BasicBlock* rpo_next_; // Link to next block in special RPO order.
166 BasicBlock* loop_header_; // Pointer to dominating loop header basic block,
167 // nullptr if none. For loop headers, this points to
168 // enclosing loop header.
169 BasicBlock* loop_end_; // end of the loop, if this block is a loop header.
170 int32_t loop_depth_; // loop nesting, 0 is top-level
171
172 Control control_; // Control at the end of the block.
173 Node* control_input_; // Input value for control.
174 NodeVector nodes_; // nodes of this block in forward order.
175
176 BasicBlockVector successors_;
177 BasicBlockVector predecessors_;
178 #if DEBUG
179 AssemblerDebugInfo debug_info_;
180 #endif
181 Id id_;
182
183 DISALLOW_COPY_AND_ASSIGN(BasicBlock);
184 };
185
186 std::ostream& operator<<(std::ostream&, const BasicBlock&);
187 std::ostream& operator<<(std::ostream&, const BasicBlock::Control&);
188 std::ostream& operator<<(std::ostream&, const BasicBlock::Id&);
189
190
191 // A schedule represents the result of assigning nodes to basic blocks
192 // and ordering them within basic blocks. Prior to computing a schedule,
193 // a graph has no notion of control flow ordering other than that induced
194 // by the graph's dependencies. A schedule is required to generate code.
NON_EXPORTED_BASE(ZoneObject)195 class V8_EXPORT_PRIVATE Schedule final : public NON_EXPORTED_BASE(ZoneObject) {
196 public:
197 explicit Schedule(Zone* zone, size_t node_count_hint = 0);
198
199 // Return the block which contains {node}, if any.
200 BasicBlock* block(Node* node) const;
201
202 bool IsScheduled(Node* node);
203 BasicBlock* GetBlockById(BasicBlock::Id block_id);
204
205 size_t BasicBlockCount() const { return all_blocks_.size(); }
206 size_t RpoBlockCount() const { return rpo_order_.size(); }
207
208 // Check if nodes {a} and {b} are in the same block.
209 bool SameBasicBlock(Node* a, Node* b) const;
210
211 // BasicBlock building: create a new block.
212 BasicBlock* NewBasicBlock();
213
214 // BasicBlock building: records that a node will later be added to a block but
215 // doesn't actually add the node to the block.
216 void PlanNode(BasicBlock* block, Node* node);
217
218 // BasicBlock building: add a node to the end of the block.
219 void AddNode(BasicBlock* block, Node* node);
220
221 // BasicBlock building: add a goto to the end of {block}.
222 void AddGoto(BasicBlock* block, BasicBlock* succ);
223
224 // BasicBlock building: add a call at the end of {block}.
225 void AddCall(BasicBlock* block, Node* call, BasicBlock* success_block,
226 BasicBlock* exception_block);
227
228 // BasicBlock building: add a branch at the end of {block}.
229 void AddBranch(BasicBlock* block, Node* branch, BasicBlock* tblock,
230 BasicBlock* fblock);
231
232 // BasicBlock building: add a switch at the end of {block}.
233 void AddSwitch(BasicBlock* block, Node* sw, BasicBlock** succ_blocks,
234 size_t succ_count);
235
236 // BasicBlock building: add a deoptimize at the end of {block}.
237 void AddDeoptimize(BasicBlock* block, Node* input);
238
239 // BasicBlock building: add a tailcall at the end of {block}.
240 void AddTailCall(BasicBlock* block, Node* input);
241
242 // BasicBlock building: add a return at the end of {block}.
243 void AddReturn(BasicBlock* block, Node* input);
244
245 // BasicBlock building: add a throw at the end of {block}.
246 void AddThrow(BasicBlock* block, Node* input);
247
248 // BasicBlock mutation: insert a branch into the end of {block}.
249 void InsertBranch(BasicBlock* block, BasicBlock* end, Node* branch,
250 BasicBlock* tblock, BasicBlock* fblock);
251
252 // BasicBlock mutation: insert a switch into the end of {block}.
253 void InsertSwitch(BasicBlock* block, BasicBlock* end, Node* sw,
254 BasicBlock** succ_blocks, size_t succ_count);
255
256 // Exposed publicly for testing only.
257 void AddSuccessorForTesting(BasicBlock* block, BasicBlock* succ) {
258 return AddSuccessor(block, succ);
259 }
260
261 const BasicBlockVector* all_blocks() const { return &all_blocks_; }
262 BasicBlockVector* rpo_order() { return &rpo_order_; }
263 const BasicBlockVector* rpo_order() const { return &rpo_order_; }
264
265 BasicBlock* start() { return start_; }
266 BasicBlock* end() { return end_; }
267
268 Zone* zone() const { return zone_; }
269
270 private:
271 friend class Scheduler;
272 friend class BasicBlockInstrumentor;
273 friend class RawMachineAssembler;
274
275 // Ensure properties of the CFG assumed by further stages.
276 void EnsureCFGWellFormedness();
277 // Eliminates no-op phi nodes added for blocks that only have a single
278 // predecessor. This ensures the property required for SSA deconstruction that
279 // the target block of a control flow split has no phis.
280 void EliminateNoopPhiNodes(BasicBlock* block);
281 // Ensure split-edge form for a hand-assembled schedule.
282 void EnsureSplitEdgeForm(BasicBlock* block);
283 // Ensure entry into a deferred block happens from a single hot block.
284 void EnsureDeferredCodeSingleEntryPoint(BasicBlock* block);
285 // Move Phi operands to newly created merger blocks
286 void MovePhis(BasicBlock* from, BasicBlock* to);
287 // Copy deferred block markers down as far as possible
288 void PropagateDeferredMark();
289
290 void AddSuccessor(BasicBlock* block, BasicBlock* succ);
291 void MoveSuccessors(BasicBlock* from, BasicBlock* to);
292
293 void SetControlInput(BasicBlock* block, Node* node);
294 void SetBlockForNode(BasicBlock* block, Node* node);
295
296 Zone* zone_;
297 BasicBlockVector all_blocks_; // All basic blocks in the schedule.
298 BasicBlockVector nodeid_to_block_; // Map from node to containing block.
299 BasicBlockVector rpo_order_; // Reverse-post-order block list.
300 BasicBlock* start_;
301 BasicBlock* end_;
302
303 DISALLOW_COPY_AND_ASSIGN(Schedule);
304 };
305
306 V8_EXPORT_PRIVATE std::ostream& operator<<(std::ostream&, const Schedule&);
307
308 } // namespace compiler
309 } // namespace internal
310 } // namespace v8
311
312 #endif // V8_COMPILER_SCHEDULE_H_
313