1 | //===- CFG.h ----------------------------------------------------*- C++ -*-===// |
2 | // |
3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
4 | // See https://llvm.org/LICENSE.txt for license information. |
5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
6 | // |
7 | //===----------------------------------------------------------------------===// |
8 | /// \file |
9 | /// |
10 | /// This file provides various utilities for inspecting and working with the |
11 | /// control flow graph in LLVM IR. This includes generic facilities for |
12 | /// iterating successors and predecessors of basic blocks, the successors of |
13 | /// specific terminator instructions, etc. It also defines specializations of |
14 | /// GraphTraits that allow Function and BasicBlock graphs to be treated as |
15 | /// proper graphs for generic algorithms. |
16 | /// |
17 | //===----------------------------------------------------------------------===// |
18 | |
19 | #ifndef LLVM_IR_CFG_H |
20 | #define LLVM_IR_CFG_H |
21 | |
22 | #include "llvm/ADT/GraphTraits.h" |
23 | #include "llvm/ADT/iterator.h" |
24 | #include "llvm/ADT/iterator_range.h" |
25 | #include "llvm/IR/Function.h" |
26 | #include "llvm/IR/Value.h" |
27 | #include "llvm/Support/Casting.h" |
28 | #include <cassert> |
29 | #include <cstddef> |
30 | #include <iterator> |
31 | |
32 | namespace llvm { |
33 | |
34 | class BasicBlock; |
35 | class Instruction; |
36 | class Use; |
37 | |
38 | //===----------------------------------------------------------------------===// |
39 | // BasicBlock pred_iterator definition |
40 | //===----------------------------------------------------------------------===// |
41 | |
42 | template <class Ptr, class USE_iterator> // Predecessor Iterator |
43 | class PredIterator { |
44 | public: |
45 | using iterator_category = std::forward_iterator_tag; |
46 | using value_type = Ptr; |
47 | using difference_type = std::ptrdiff_t; |
48 | using pointer = Ptr *; |
49 | using reference = Ptr *; |
50 | |
51 | private: |
52 | using Self = PredIterator<Ptr, USE_iterator>; |
53 | USE_iterator It; |
54 | |
55 | inline void advancePastNonTerminators() { |
56 | // Loop to ignore non-terminator uses (for example BlockAddresses). |
57 | while (!It.atEnd()) { |
58 | if (auto *Inst = dyn_cast<Instruction>(*It)) |
59 | if (Inst->isTerminator()) |
60 | break; |
61 | |
62 | ++It; |
63 | } |
64 | } |
65 | |
66 | public: |
67 | PredIterator() = default; |
68 | explicit inline PredIterator(Ptr *bb) : It(bb->user_begin()) { |
69 | advancePastNonTerminators(); |
70 | } |
71 | inline PredIterator(Ptr *bb, bool) : It(bb->user_end()) {} |
72 | |
73 | inline bool operator==(const Self& x) const { return It == x.It; } |
74 | inline bool operator!=(const Self& x) const { return !operator==(x); } |
75 | |
76 | inline reference operator*() const { |
77 | assert(!It.atEnd() && "pred_iterator out of range!" ); |
78 | return cast<Instruction>(*It)->getParent(); |
79 | } |
80 | inline pointer *operator->() const { return &operator*(); } |
81 | |
82 | inline Self& operator++() { // Preincrement |
83 | assert(!It.atEnd() && "pred_iterator out of range!" ); |
84 | ++It; advancePastNonTerminators(); |
85 | return *this; |
86 | } |
87 | |
88 | inline Self operator++(int) { // Postincrement |
89 | Self tmp = *this; ++*this; return tmp; |
90 | } |
91 | |
92 | /// getOperandNo - Return the operand number in the predecessor's |
93 | /// terminator of the successor. |
94 | unsigned getOperandNo() const { |
95 | return It.getOperandNo(); |
96 | } |
97 | |
98 | /// getUse - Return the operand Use in the predecessor's terminator |
99 | /// of the successor. |
100 | Use &getUse() const { |
101 | return It.getUse(); |
102 | } |
103 | }; |
104 | |
105 | using pred_iterator = PredIterator<BasicBlock, Value::user_iterator>; |
106 | using const_pred_iterator = |
107 | PredIterator<const BasicBlock, Value::const_user_iterator>; |
108 | using pred_range = iterator_range<pred_iterator>; |
109 | using const_pred_range = iterator_range<const_pred_iterator>; |
110 | |
111 | inline pred_iterator pred_begin(BasicBlock *BB) { return pred_iterator(BB); } |
112 | inline const_pred_iterator pred_begin(const BasicBlock *BB) { |
113 | return const_pred_iterator(BB); |
114 | } |
115 | inline pred_iterator pred_end(BasicBlock *BB) { return pred_iterator(BB, true);} |
116 | inline const_pred_iterator pred_end(const BasicBlock *BB) { |
117 | return const_pred_iterator(BB, true); |
118 | } |
119 | inline bool pred_empty(const BasicBlock *BB) { |
120 | return pred_begin(BB) == pred_end(BB); |
121 | } |
122 | /// Get the number of predecessors of \p BB. This is a linear time operation. |
123 | /// Use \ref BasicBlock::hasNPredecessors() or hasNPredecessorsOrMore if able. |
124 | inline unsigned pred_size(const BasicBlock *BB) { |
125 | return std::distance(pred_begin(BB), pred_end(BB)); |
126 | } |
127 | inline pred_range predecessors(BasicBlock *BB) { |
128 | return pred_range(pred_begin(BB), pred_end(BB)); |
129 | } |
130 | inline const_pred_range predecessors(const BasicBlock *BB) { |
131 | return const_pred_range(pred_begin(BB), pred_end(BB)); |
132 | } |
133 | |
134 | //===----------------------------------------------------------------------===// |
135 | // Instruction and BasicBlock succ_iterator helpers |
136 | //===----------------------------------------------------------------------===// |
137 | |
138 | template <class InstructionT, class BlockT> |
139 | class SuccIterator |
140 | : public iterator_facade_base<SuccIterator<InstructionT, BlockT>, |
141 | std::random_access_iterator_tag, BlockT, int, |
142 | BlockT *, BlockT *> { |
143 | public: |
144 | using difference_type = int; |
145 | using pointer = BlockT *; |
146 | using reference = BlockT *; |
147 | |
148 | private: |
149 | InstructionT *Inst; |
150 | int Idx; |
151 | using Self = SuccIterator<InstructionT, BlockT>; |
152 | |
153 | inline bool index_is_valid(int Idx) { |
154 | // Note that we specially support the index of zero being valid even in the |
155 | // face of a null instruction. |
156 | return Idx >= 0 && (Idx == 0 || Idx <= (int)Inst->getNumSuccessors()); |
157 | } |
158 | |
159 | /// Proxy object to allow write access in operator[] |
160 | class SuccessorProxy { |
161 | Self It; |
162 | |
163 | public: |
164 | explicit SuccessorProxy(const Self &It) : It(It) {} |
165 | |
166 | SuccessorProxy(const SuccessorProxy &) = default; |
167 | |
168 | SuccessorProxy &operator=(SuccessorProxy RHS) { |
169 | *this = reference(RHS); |
170 | return *this; |
171 | } |
172 | |
173 | SuccessorProxy &operator=(reference RHS) { |
174 | It.Inst->setSuccessor(It.Idx, RHS); |
175 | return *this; |
176 | } |
177 | |
178 | operator reference() const { return *It; } |
179 | }; |
180 | |
181 | public: |
182 | // begin iterator |
183 | explicit inline SuccIterator(InstructionT *Inst) : Inst(Inst), Idx(0) {} |
184 | // end iterator |
185 | inline SuccIterator(InstructionT *Inst, bool) : Inst(Inst) { |
186 | if (Inst) |
187 | Idx = Inst->getNumSuccessors(); |
188 | else |
189 | // Inst == NULL happens, if a basic block is not fully constructed and |
190 | // consequently getTerminator() returns NULL. In this case we construct |
191 | // a SuccIterator which describes a basic block that has zero |
192 | // successors. |
193 | // Defining SuccIterator for incomplete and malformed CFGs is especially |
194 | // useful for debugging. |
195 | Idx = 0; |
196 | } |
197 | |
198 | /// This is used to interface between code that wants to |
199 | /// operate on terminator instructions directly. |
200 | int getSuccessorIndex() const { return Idx; } |
201 | |
202 | inline bool operator==(const Self &x) const { return Idx == x.Idx; } |
203 | |
204 | inline BlockT *operator*() const { return Inst->getSuccessor(Idx); } |
205 | |
206 | // We use the basic block pointer directly for operator->. |
207 | inline BlockT *operator->() const { return operator*(); } |
208 | |
209 | inline bool operator<(const Self &RHS) const { |
210 | assert(Inst == RHS.Inst && "Cannot compare iterators of different blocks!" ); |
211 | return Idx < RHS.Idx; |
212 | } |
213 | |
214 | int operator-(const Self &RHS) const { |
215 | assert(Inst == RHS.Inst && "Cannot compare iterators of different blocks!" ); |
216 | return Idx - RHS.Idx; |
217 | } |
218 | |
219 | inline Self &operator+=(int RHS) { |
220 | int NewIdx = Idx + RHS; |
221 | assert(index_is_valid(NewIdx) && "Iterator index out of bound" ); |
222 | Idx = NewIdx; |
223 | return *this; |
224 | } |
225 | |
226 | inline Self &operator-=(int RHS) { return operator+=(-RHS); } |
227 | |
228 | // Specially implement the [] operation using a proxy object to support |
229 | // assignment. |
230 | inline SuccessorProxy operator[](int Offset) { |
231 | Self TmpIt = *this; |
232 | TmpIt += Offset; |
233 | return SuccessorProxy(TmpIt); |
234 | } |
235 | |
236 | /// Get the source BlockT of this iterator. |
237 | inline BlockT *getSource() { |
238 | assert(Inst && "Source not available, if basic block was malformed" ); |
239 | return Inst->getParent(); |
240 | } |
241 | }; |
242 | |
243 | using succ_iterator = SuccIterator<Instruction, BasicBlock>; |
244 | using const_succ_iterator = SuccIterator<const Instruction, const BasicBlock>; |
245 | using succ_range = iterator_range<succ_iterator>; |
246 | using const_succ_range = iterator_range<const_succ_iterator>; |
247 | |
248 | inline succ_iterator succ_begin(Instruction *I) { return succ_iterator(I); } |
249 | inline const_succ_iterator succ_begin(const Instruction *I) { |
250 | return const_succ_iterator(I); |
251 | } |
252 | inline succ_iterator succ_end(Instruction *I) { return succ_iterator(I, true); } |
253 | inline const_succ_iterator succ_end(const Instruction *I) { |
254 | return const_succ_iterator(I, true); |
255 | } |
256 | inline bool succ_empty(const Instruction *I) { |
257 | return succ_begin(I) == succ_end(I); |
258 | } |
259 | inline unsigned succ_size(const Instruction *I) { |
260 | return std::distance(succ_begin(I), succ_end(I)); |
261 | } |
262 | inline succ_range successors(Instruction *I) { |
263 | return succ_range(succ_begin(I), succ_end(I)); |
264 | } |
265 | inline const_succ_range successors(const Instruction *I) { |
266 | return const_succ_range(succ_begin(I), succ_end(I)); |
267 | } |
268 | |
269 | inline succ_iterator succ_begin(BasicBlock *BB) { |
270 | return succ_iterator(BB->getTerminator()); |
271 | } |
272 | inline const_succ_iterator succ_begin(const BasicBlock *BB) { |
273 | return const_succ_iterator(BB->getTerminator()); |
274 | } |
275 | inline succ_iterator succ_end(BasicBlock *BB) { |
276 | return succ_iterator(BB->getTerminator(), true); |
277 | } |
278 | inline const_succ_iterator succ_end(const BasicBlock *BB) { |
279 | return const_succ_iterator(BB->getTerminator(), true); |
280 | } |
281 | inline bool succ_empty(const BasicBlock *BB) { |
282 | return succ_begin(BB) == succ_end(BB); |
283 | } |
284 | inline unsigned succ_size(const BasicBlock *BB) { |
285 | return std::distance(succ_begin(BB), succ_end(BB)); |
286 | } |
287 | inline succ_range successors(BasicBlock *BB) { |
288 | return succ_range(succ_begin(BB), succ_end(BB)); |
289 | } |
290 | inline const_succ_range successors(const BasicBlock *BB) { |
291 | return const_succ_range(succ_begin(BB), succ_end(BB)); |
292 | } |
293 | |
294 | //===--------------------------------------------------------------------===// |
295 | // GraphTraits specializations for basic block graphs (CFGs) |
296 | //===--------------------------------------------------------------------===// |
297 | |
298 | // Provide specializations of GraphTraits to be able to treat a function as a |
299 | // graph of basic blocks... |
300 | |
301 | template <> struct GraphTraits<BasicBlock*> { |
302 | using NodeRef = BasicBlock *; |
303 | using ChildIteratorType = succ_iterator; |
304 | |
305 | static NodeRef getEntryNode(BasicBlock *BB) { return BB; } |
306 | static ChildIteratorType child_begin(NodeRef N) { return succ_begin(N); } |
307 | static ChildIteratorType child_end(NodeRef N) { return succ_end(N); } |
308 | }; |
309 | |
310 | template <> struct GraphTraits<const BasicBlock*> { |
311 | using NodeRef = const BasicBlock *; |
312 | using ChildIteratorType = const_succ_iterator; |
313 | |
314 | static NodeRef getEntryNode(const BasicBlock *BB) { return BB; } |
315 | |
316 | static ChildIteratorType child_begin(NodeRef N) { return succ_begin(N); } |
317 | static ChildIteratorType child_end(NodeRef N) { return succ_end(N); } |
318 | }; |
319 | |
320 | // Provide specializations of GraphTraits to be able to treat a function as a |
321 | // graph of basic blocks... and to walk it in inverse order. Inverse order for |
322 | // a function is considered to be when traversing the predecessor edges of a BB |
323 | // instead of the successor edges. |
324 | // |
325 | template <> struct GraphTraits<Inverse<BasicBlock*>> { |
326 | using NodeRef = BasicBlock *; |
327 | using ChildIteratorType = pred_iterator; |
328 | |
329 | static NodeRef getEntryNode(Inverse<BasicBlock *> G) { return G.Graph; } |
330 | static ChildIteratorType child_begin(NodeRef N) { return pred_begin(N); } |
331 | static ChildIteratorType child_end(NodeRef N) { return pred_end(N); } |
332 | }; |
333 | |
334 | template <> struct GraphTraits<Inverse<const BasicBlock*>> { |
335 | using NodeRef = const BasicBlock *; |
336 | using ChildIteratorType = const_pred_iterator; |
337 | |
338 | static NodeRef getEntryNode(Inverse<const BasicBlock *> G) { return G.Graph; } |
339 | static ChildIteratorType child_begin(NodeRef N) { return pred_begin(N); } |
340 | static ChildIteratorType child_end(NodeRef N) { return pred_end(N); } |
341 | }; |
342 | |
343 | //===--------------------------------------------------------------------===// |
344 | // GraphTraits specializations for function basic block graphs (CFGs) |
345 | //===--------------------------------------------------------------------===// |
346 | |
347 | // Provide specializations of GraphTraits to be able to treat a function as a |
348 | // graph of basic blocks... these are the same as the basic block iterators, |
349 | // except that the root node is implicitly the first node of the function. |
350 | // |
351 | template <> struct GraphTraits<Function*> : public GraphTraits<BasicBlock*> { |
352 | static NodeRef getEntryNode(Function *F) { return &F->getEntryBlock(); } |
353 | |
354 | // nodes_iterator/begin/end - Allow iteration over all nodes in the graph |
355 | using nodes_iterator = pointer_iterator<Function::iterator>; |
356 | |
357 | static nodes_iterator nodes_begin(Function *F) { |
358 | return nodes_iterator(F->begin()); |
359 | } |
360 | |
361 | static nodes_iterator nodes_end(Function *F) { |
362 | return nodes_iterator(F->end()); |
363 | } |
364 | |
365 | static size_t size(Function *F) { return F->size(); } |
366 | }; |
367 | template <> struct GraphTraits<const Function*> : |
368 | public GraphTraits<const BasicBlock*> { |
369 | static NodeRef getEntryNode(const Function *F) { return &F->getEntryBlock(); } |
370 | |
371 | // nodes_iterator/begin/end - Allow iteration over all nodes in the graph |
372 | using nodes_iterator = pointer_iterator<Function::const_iterator>; |
373 | |
374 | static nodes_iterator nodes_begin(const Function *F) { |
375 | return nodes_iterator(F->begin()); |
376 | } |
377 | |
378 | static nodes_iterator nodes_end(const Function *F) { |
379 | return nodes_iterator(F->end()); |
380 | } |
381 | |
382 | static size_t size(const Function *F) { return F->size(); } |
383 | }; |
384 | |
385 | // Provide specializations of GraphTraits to be able to treat a function as a |
386 | // graph of basic blocks... and to walk it in inverse order. Inverse order for |
387 | // a function is considered to be when traversing the predecessor edges of a BB |
388 | // instead of the successor edges. |
389 | // |
390 | template <> struct GraphTraits<Inverse<Function*>> : |
391 | public GraphTraits<Inverse<BasicBlock*>> { |
392 | static NodeRef getEntryNode(Inverse<Function *> G) { |
393 | return &G.Graph->getEntryBlock(); |
394 | } |
395 | }; |
396 | template <> struct GraphTraits<Inverse<const Function*>> : |
397 | public GraphTraits<Inverse<const BasicBlock*>> { |
398 | static NodeRef getEntryNode(Inverse<const Function *> G) { |
399 | return &G.Graph->getEntryBlock(); |
400 | } |
401 | }; |
402 | |
403 | } // end namespace llvm |
404 | |
405 | #endif // LLVM_IR_CFG_H |
406 | |