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1 : //===- llvm/BasicBlock.h - Represent a basic block in the VM ----*- 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 : //
9 : // This file contains the declaration of the BasicBlock class.
10 : //
11 : //===----------------------------------------------------------------------===//
12 :
13 : #ifndef LLVM_IR_BASICBLOCK_H
14 : #define LLVM_IR_BASICBLOCK_H
15 :
16 : #include "llvm-c/Types.h"
17 : #include "llvm/ADT/DenseMap.h"
18 : #include "llvm/ADT/Twine.h"
19 : #include "llvm/ADT/ilist.h"
20 : #include "llvm/ADT/ilist_node.h"
21 : #include "llvm/ADT/iterator.h"
22 : #include "llvm/ADT/iterator_range.h"
23 : #include "llvm/IR/DebugProgramInstruction.h"
24 : #include "llvm/IR/Instruction.h"
25 : #include "llvm/IR/SymbolTableListTraits.h"
26 : #include "llvm/IR/Value.h"
27 : #include <cassert>
28 : #include <cstddef>
29 : #include <iterator>
30 :
31 : namespace llvm {
32 :
33 : class AssemblyAnnotationWriter;
34 : class CallInst;
35 : class DataLayout;
36 : class Function;
37 : class LandingPadInst;
38 : class LLVMContext;
39 : class Module;
40 : class PHINode;
41 : class ValueSymbolTable;
42 : class DbgVariableRecord;
43 : class DbgMarker;
44 :
45 : /// LLVM Basic Block Representation
46 : ///
47 : /// This represents a single basic block in LLVM. A basic block is simply a
48 : /// container of instructions that execute sequentially. Basic blocks are Values
49 : /// because they are referenced by instructions such as branches and switch
50 : /// tables. The type of a BasicBlock is "Type::LabelTy" because the basic block
51 : /// represents a label to which a branch can jump.
52 : ///
53 : /// A well formed basic block is formed of a list of non-terminating
54 : /// instructions followed by a single terminator instruction. Terminator
55 : /// instructions may not occur in the middle of basic blocks, and must terminate
56 : /// the blocks. The BasicBlock class allows malformed basic blocks to occur
57 : /// because it may be useful in the intermediate stage of constructing or
58 : /// modifying a program. However, the verifier will ensure that basic blocks are
59 : /// "well formed".
60 : class BasicBlock final : public Value, // Basic blocks are data objects also
61 : public ilist_node_with_parent<BasicBlock, Function> {
62 : public:
63 : using InstListType = SymbolTableList<Instruction, ilist_iterator_bits<true>,
64 : ilist_parent<BasicBlock>>;
65 : /// Flag recording whether or not this block stores debug-info in the form
66 : /// of intrinsic instructions (false) or non-instruction records (true).
67 : bool IsNewDbgInfoFormat;
68 :
69 : private:
70 : friend class BlockAddress;
71 : friend class SymbolTableListTraits<BasicBlock>;
72 :
73 : InstListType InstList;
74 : Function *Parent;
75 :
76 : public:
77 : /// Attach a DbgMarker to the given instruction. Enables the storage of any
78 : /// debug-info at this position in the program.
79 : DbgMarker *createMarker(Instruction *I);
80 : DbgMarker *createMarker(InstListType::iterator It);
81 :
82 : /// Convert variable location debugging information stored in dbg.value
83 : /// intrinsics into DbgMarkers / DbgRecords. Deletes all dbg.values in
84 : /// the process and sets IsNewDbgInfoFormat = true. Only takes effect if
85 : /// the UseNewDbgInfoFormat LLVM command line option is given.
86 : void convertToNewDbgValues();
87 :
88 : /// Convert variable location debugging information stored in DbgMarkers and
89 : /// DbgRecords into the dbg.value intrinsic representation. Sets
90 : /// IsNewDbgInfoFormat = false.
91 : void convertFromNewDbgValues();
92 :
93 : /// Ensure the block is in "old" dbg.value format (\p NewFlag == false) or
94 : /// in the new format (\p NewFlag == true), converting to the desired format
95 : /// if necessary.
96 : void setIsNewDbgInfoFormat(bool NewFlag);
97 : void setNewDbgInfoFormatFlag(bool NewFlag);
98 :
99 : /// Record that the collection of DbgRecords in \p M "trails" after the last
100 : /// instruction of this block. These are equivalent to dbg.value intrinsics
101 : /// that exist at the end of a basic block with no terminator (a transient
102 : /// state that occurs regularly).
103 : void setTrailingDbgRecords(DbgMarker *M);
104 :
105 : /// Fetch the collection of DbgRecords that "trail" after the last instruction
106 : /// of this block, see \ref setTrailingDbgRecords. If there are none, returns
107 : /// nullptr.
108 : DbgMarker *getTrailingDbgRecords();
109 :
110 : /// Delete any trailing DbgRecords at the end of this block, see
111 : /// \ref setTrailingDbgRecords.
112 : void deleteTrailingDbgRecords();
113 :
114 : void dumpDbgValues() const;
115 :
116 : /// Return the DbgMarker for the position given by \p It, so that DbgRecords
117 : /// can be inserted there. This will either be nullptr if not present, a
118 : /// DbgMarker, or TrailingDbgRecords if It is end().
119 : DbgMarker *getMarker(InstListType::iterator It);
120 :
121 : /// Return the DbgMarker for the position that comes after \p I. \see
122 : /// BasicBlock::getMarker, this can be nullptr, a DbgMarker, or
123 : /// TrailingDbgRecords if there is no next instruction.
124 : DbgMarker *getNextMarker(Instruction *I);
125 :
126 : /// Insert a DbgRecord into a block at the position given by \p I.
127 : void insertDbgRecordAfter(DbgRecord *DR, Instruction *I);
128 :
129 : /// Insert a DbgRecord into a block at the position given by \p Here.
130 : void insertDbgRecordBefore(DbgRecord *DR, InstListType::iterator Here);
131 :
132 : /// Eject any debug-info trailing at the end of a block. DbgRecords can
133 : /// transiently be located "off the end" of a block if the blocks terminator
134 : /// is temporarily removed. Once a terminator is re-inserted this method will
135 : /// move such DbgRecords back to the right place (ahead of the terminator).
136 : void flushTerminatorDbgRecords();
137 :
138 : /// In rare circumstances instructions can be speculatively removed from
139 : /// blocks, and then be re-inserted back into that position later. When this
140 : /// happens in RemoveDIs debug-info mode, some special patching-up needs to
141 : /// occur: inserting into the middle of a sequence of dbg.value intrinsics
142 : /// does not have an equivalent with DbgRecords.
143 : void reinsertInstInDbgRecords(Instruction *I,
144 : std::optional<DbgRecord::self_iterator> Pos);
145 :
146 : private:
147 : void setParent(Function *parent);
148 :
149 : /// Constructor.
150 : ///
151 : /// If the function parameter is specified, the basic block is automatically
152 : /// inserted at either the end of the function (if InsertBefore is null), or
153 : /// before the specified basic block.
154 : explicit BasicBlock(LLVMContext &C, const Twine &Name = "",
155 : Function *Parent = nullptr,
156 : BasicBlock *InsertBefore = nullptr);
157 :
158 : public:
159 : BasicBlock(const BasicBlock &) = delete;
160 : BasicBlock &operator=(const BasicBlock &) = delete;
161 : ~BasicBlock();
162 :
163 : /// Get the context in which this basic block lives.
164 : LLVMContext &getContext() const;
165 :
166 : /// Instruction iterators...
167 : using iterator = InstListType::iterator;
168 : using const_iterator = InstListType::const_iterator;
169 : using reverse_iterator = InstListType::reverse_iterator;
170 : using const_reverse_iterator = InstListType::const_reverse_iterator;
171 :
172 : // These functions and classes need access to the instruction list.
173 : friend void Instruction::removeFromParent();
174 : friend BasicBlock::iterator Instruction::eraseFromParent();
175 : friend BasicBlock::iterator Instruction::insertInto(BasicBlock *BB,
176 : BasicBlock::iterator It);
177 : friend class llvm::SymbolTableListTraits<
178 : llvm::Instruction, ilist_iterator_bits<true>, ilist_parent<BasicBlock>>;
179 : friend class llvm::ilist_node_with_parent<llvm::Instruction, llvm::BasicBlock,
180 : ilist_iterator_bits<true>,
181 : ilist_parent<BasicBlock>>;
182 :
183 : // Friendly methods that need to access us for the maintenence of
184 : // debug-info attachments.
185 : friend void Instruction::insertBefore(BasicBlock::iterator InsertPos);
186 : friend void Instruction::insertAfter(Instruction *InsertPos);
187 : friend void Instruction::insertBefore(BasicBlock &BB,
188 : InstListType::iterator InsertPos);
189 : friend void Instruction::moveBeforeImpl(BasicBlock &BB,
190 : InstListType::iterator I,
191 : bool Preserve);
192 : friend iterator_range<DbgRecord::self_iterator>
193 : Instruction::cloneDebugInfoFrom(
194 : const Instruction *From, std::optional<DbgRecord::self_iterator> FromHere,
195 : bool InsertAtHead);
196 :
197 : /// Creates a new BasicBlock.
198 : ///
199 : /// If the Parent parameter is specified, the basic block is automatically
200 : /// inserted at either the end of the function (if InsertBefore is 0), or
201 : /// before the specified basic block.
202 0 : static BasicBlock *Create(LLVMContext &Context, const Twine &Name = "",
203 : Function *Parent = nullptr,
204 : BasicBlock *InsertBefore = nullptr) {
205 0 : return new BasicBlock(Context, Name, Parent, InsertBefore);
206 : }
207 :
208 : /// Return the enclosing method, or null if none.
209 : const Function *getParent() const { return Parent; }
210 : Function *getParent() { return Parent; }
211 :
212 : /// Return the module owning the function this basic block belongs to, or
213 : /// nullptr if the function does not have a module.
214 : ///
215 : /// Note: this is undefined behavior if the block does not have a parent.
216 : const Module *getModule() const;
217 : Module *getModule() {
218 : return const_cast<Module *>(
219 : static_cast<const BasicBlock *>(this)->getModule());
220 : }
221 :
222 : /// Get the data layout of the module this basic block belongs to.
223 : ///
224 : /// Requires the basic block to have a parent module.
225 : const DataLayout &getDataLayout() const;
226 :
227 : /// Returns the terminator instruction if the block is well formed or null
228 : /// if the block is not well formed.
229 : const Instruction *getTerminator() const LLVM_READONLY {
230 : if (InstList.empty() || !InstList.back().isTerminator())
231 : return nullptr;
232 : return &InstList.back();
233 : }
234 : Instruction *getTerminator() {
235 : return const_cast<Instruction *>(
236 : static_cast<const BasicBlock *>(this)->getTerminator());
237 : }
238 :
239 : /// Returns the call instruction calling \@llvm.experimental.deoptimize
240 : /// prior to the terminating return instruction of this basic block, if such
241 : /// a call is present. Otherwise, returns null.
242 : const CallInst *getTerminatingDeoptimizeCall() const;
243 : CallInst *getTerminatingDeoptimizeCall() {
244 : return const_cast<CallInst *>(
245 : static_cast<const BasicBlock *>(this)->getTerminatingDeoptimizeCall());
246 : }
247 :
248 : /// Returns the call instruction calling \@llvm.experimental.deoptimize
249 : /// that is present either in current basic block or in block that is a unique
250 : /// successor to current block, if such call is present. Otherwise, returns null.
251 : const CallInst *getPostdominatingDeoptimizeCall() const;
252 : CallInst *getPostdominatingDeoptimizeCall() {
253 : return const_cast<CallInst *>(
254 : static_cast<const BasicBlock *>(this)->getPostdominatingDeoptimizeCall());
255 : }
256 :
257 : /// Returns the call instruction marked 'musttail' prior to the terminating
258 : /// return instruction of this basic block, if such a call is present.
259 : /// Otherwise, returns null.
260 : const CallInst *getTerminatingMustTailCall() const;
261 : CallInst *getTerminatingMustTailCall() {
262 : return const_cast<CallInst *>(
263 : static_cast<const BasicBlock *>(this)->getTerminatingMustTailCall());
264 : }
265 :
266 : /// Returns a pointer to the first instruction in this block that is not a
267 : /// PHINode instruction.
268 : ///
269 : /// When adding instructions to the beginning of the basic block, they should
270 : /// be added before the returned value, not before the first instruction,
271 : /// which might be PHI. Returns 0 is there's no non-PHI instruction.
272 : const Instruction* getFirstNonPHI() const;
273 : Instruction* getFirstNonPHI() {
274 : return const_cast<Instruction *>(
275 : static_cast<const BasicBlock *>(this)->getFirstNonPHI());
276 : }
277 :
278 : /// Iterator returning form of getFirstNonPHI. Installed as a placeholder for
279 : /// the RemoveDIs project that will eventually remove debug intrinsics.
280 : InstListType::const_iterator getFirstNonPHIIt() const;
281 : InstListType::iterator getFirstNonPHIIt() {
282 : BasicBlock::iterator It =
283 : static_cast<const BasicBlock *>(this)->getFirstNonPHIIt().getNonConst();
284 : It.setHeadBit(true);
285 : return It;
286 : }
287 :
288 : /// Returns a pointer to the first instruction in this block that is not a
289 : /// PHINode or a debug intrinsic, or any pseudo operation if \c SkipPseudoOp
290 : /// is true.
291 : const Instruction *getFirstNonPHIOrDbg(bool SkipPseudoOp = true) const;
292 : Instruction *getFirstNonPHIOrDbg(bool SkipPseudoOp = true) {
293 : return const_cast<Instruction *>(
294 : static_cast<const BasicBlock *>(this)->getFirstNonPHIOrDbg(
295 : SkipPseudoOp));
296 : }
297 :
298 : /// Returns a pointer to the first instruction in this block that is not a
299 : /// PHINode, a debug intrinsic, or a lifetime intrinsic, or any pseudo
300 : /// operation if \c SkipPseudoOp is true.
301 : const Instruction *
302 : getFirstNonPHIOrDbgOrLifetime(bool SkipPseudoOp = true) const;
303 : Instruction *getFirstNonPHIOrDbgOrLifetime(bool SkipPseudoOp = true) {
304 : return const_cast<Instruction *>(
305 : static_cast<const BasicBlock *>(this)->getFirstNonPHIOrDbgOrLifetime(
306 : SkipPseudoOp));
307 : }
308 :
309 : /// Returns an iterator to the first instruction in this block that is
310 : /// suitable for inserting a non-PHI instruction.
311 : ///
312 : /// In particular, it skips all PHIs and LandingPad instructions.
313 : const_iterator getFirstInsertionPt() const;
314 : iterator getFirstInsertionPt() {
315 : return static_cast<const BasicBlock *>(this)
316 : ->getFirstInsertionPt().getNonConst();
317 : }
318 :
319 : /// Returns an iterator to the first instruction in this block that is
320 : /// not a PHINode, a debug intrinsic, a static alloca or any pseudo operation.
321 : const_iterator getFirstNonPHIOrDbgOrAlloca() const;
322 : iterator getFirstNonPHIOrDbgOrAlloca() {
323 : return static_cast<const BasicBlock *>(this)
324 : ->getFirstNonPHIOrDbgOrAlloca()
325 : .getNonConst();
326 : }
327 :
328 : /// Returns the first potential AsynchEH faulty instruction
329 : /// currently it checks for loads/stores (which may dereference a null
330 : /// pointer) and calls/invokes (which may propagate exceptions)
331 : const Instruction* getFirstMayFaultInst() const;
332 : Instruction* getFirstMayFaultInst() {
333 : return const_cast<Instruction*>(
334 : static_cast<const BasicBlock*>(this)->getFirstMayFaultInst());
335 : }
336 :
337 : /// Return a const iterator range over the instructions in the block, skipping
338 : /// any debug instructions. Skip any pseudo operations as well if \c
339 : /// SkipPseudoOp is true.
340 : iterator_range<filter_iterator<BasicBlock::const_iterator,
341 : std::function<bool(const Instruction &)>>>
342 : instructionsWithoutDebug(bool SkipPseudoOp = true) const;
343 :
344 : /// Return an iterator range over the instructions in the block, skipping any
345 : /// debug instructions. Skip and any pseudo operations as well if \c
346 : /// SkipPseudoOp is true.
347 : iterator_range<
348 : filter_iterator<BasicBlock::iterator, std::function<bool(Instruction &)>>>
349 : instructionsWithoutDebug(bool SkipPseudoOp = true);
350 :
351 : /// Return the size of the basic block ignoring debug instructions
352 : filter_iterator<BasicBlock::const_iterator,
353 : std::function<bool(const Instruction &)>>::difference_type
354 : sizeWithoutDebug() const;
355 :
356 : /// Unlink 'this' from the containing function, but do not delete it.
357 : void removeFromParent();
358 :
359 : /// Unlink 'this' from the containing function and delete it.
360 : ///
361 : // \returns an iterator pointing to the element after the erased one.
362 : SymbolTableList<BasicBlock>::iterator eraseFromParent();
363 :
364 : /// Unlink this basic block from its current function and insert it into
365 : /// the function that \p MovePos lives in, right before \p MovePos.
366 : inline void moveBefore(BasicBlock *MovePos) {
367 : moveBefore(MovePos->getIterator());
368 : }
369 : void moveBefore(SymbolTableList<BasicBlock>::iterator MovePos);
370 :
371 : /// Unlink this basic block from its current function and insert it
372 : /// right after \p MovePos in the function \p MovePos lives in.
373 : void moveAfter(BasicBlock *MovePos);
374 :
375 : /// Insert unlinked basic block into a function.
376 : ///
377 : /// Inserts an unlinked basic block into \c Parent. If \c InsertBefore is
378 : /// provided, inserts before that basic block, otherwise inserts at the end.
379 : ///
380 : /// \pre \a getParent() is \c nullptr.
381 : void insertInto(Function *Parent, BasicBlock *InsertBefore = nullptr);
382 :
383 : /// Return the predecessor of this block if it has a single predecessor
384 : /// block. Otherwise return a null pointer.
385 : const BasicBlock *getSinglePredecessor() const;
386 : BasicBlock *getSinglePredecessor() {
387 : return const_cast<BasicBlock *>(
388 : static_cast<const BasicBlock *>(this)->getSinglePredecessor());
389 : }
390 :
391 : /// Return the predecessor of this block if it has a unique predecessor
392 : /// block. Otherwise return a null pointer.
393 : ///
394 : /// Note that unique predecessor doesn't mean single edge, there can be
395 : /// multiple edges from the unique predecessor to this block (for example a
396 : /// switch statement with multiple cases having the same destination).
397 : const BasicBlock *getUniquePredecessor() const;
398 : BasicBlock *getUniquePredecessor() {
399 : return const_cast<BasicBlock *>(
400 : static_cast<const BasicBlock *>(this)->getUniquePredecessor());
401 : }
402 :
403 : /// Return true if this block has exactly N predecessors.
404 : bool hasNPredecessors(unsigned N) const;
405 :
406 : /// Return true if this block has N predecessors or more.
407 : bool hasNPredecessorsOrMore(unsigned N) const;
408 :
409 : /// Return the successor of this block if it has a single successor.
410 : /// Otherwise return a null pointer.
411 : ///
412 : /// This method is analogous to getSinglePredecessor above.
413 : const BasicBlock *getSingleSuccessor() const;
414 : BasicBlock *getSingleSuccessor() {
415 : return const_cast<BasicBlock *>(
416 : static_cast<const BasicBlock *>(this)->getSingleSuccessor());
417 : }
418 :
419 : /// Return the successor of this block if it has a unique successor.
420 : /// Otherwise return a null pointer.
421 : ///
422 : /// This method is analogous to getUniquePredecessor above.
423 : const BasicBlock *getUniqueSuccessor() const;
424 : BasicBlock *getUniqueSuccessor() {
425 : return const_cast<BasicBlock *>(
426 : static_cast<const BasicBlock *>(this)->getUniqueSuccessor());
427 : }
428 :
429 : /// Print the basic block to an output stream with an optional
430 : /// AssemblyAnnotationWriter.
431 : void print(raw_ostream &OS, AssemblyAnnotationWriter *AAW = nullptr,
432 : bool ShouldPreserveUseListOrder = false,
433 : bool IsForDebug = false) const;
434 :
435 : //===--------------------------------------------------------------------===//
436 : /// Instruction iterator methods
437 : ///
438 58673 : inline iterator begin() {
439 58673 : iterator It = InstList.begin();
440 : // Set the head-inclusive bit to indicate that this iterator includes
441 : // any debug-info at the start of the block. This is a no-op unless the
442 : // appropriate CMake flag is set.
443 58673 : It.setHeadBit(true);
444 58673 : return It;
445 : }
446 : inline const_iterator begin() const {
447 : const_iterator It = InstList.begin();
448 : It.setHeadBit(true);
449 : return It;
450 : }
451 58673 : inline iterator end () { return InstList.end(); }
452 : inline const_iterator end () const { return InstList.end(); }
453 :
454 : inline reverse_iterator rbegin() { return InstList.rbegin(); }
455 : inline const_reverse_iterator rbegin() const { return InstList.rbegin(); }
456 : inline reverse_iterator rend () { return InstList.rend(); }
457 : inline const_reverse_iterator rend () const { return InstList.rend(); }
458 :
459 : inline size_t size() const { return InstList.size(); }
460 : inline bool empty() const { return InstList.empty(); }
461 : inline const Instruction &front() const { return InstList.front(); }
462 : inline Instruction &front() { return InstList.front(); }
463 : inline const Instruction &back() const { return InstList.back(); }
464 : inline Instruction &back() { return InstList.back(); }
465 :
466 : /// Iterator to walk just the phi nodes in the basic block.
467 : template <typename PHINodeT = PHINode, typename BBIteratorT = iterator>
468 : class phi_iterator_impl
469 : : public iterator_facade_base<phi_iterator_impl<PHINodeT, BBIteratorT>,
470 : std::forward_iterator_tag, PHINodeT> {
471 : friend BasicBlock;
472 :
473 : PHINodeT *PN;
474 :
475 : phi_iterator_impl(PHINodeT *PN) : PN(PN) {}
476 :
477 : public:
478 : // Allow default construction to build variables, but this doesn't build
479 : // a useful iterator.
480 : phi_iterator_impl() = default;
481 :
482 : // Allow conversion between instantiations where valid.
483 : template <typename PHINodeU, typename BBIteratorU,
484 : typename = std::enable_if_t<
485 : std::is_convertible<PHINodeU *, PHINodeT *>::value>>
486 : phi_iterator_impl(const phi_iterator_impl<PHINodeU, BBIteratorU> &Arg)
487 : : PN(Arg.PN) {}
488 :
489 : bool operator==(const phi_iterator_impl &Arg) const { return PN == Arg.PN; }
490 :
491 : PHINodeT &operator*() const { return *PN; }
492 :
493 : using phi_iterator_impl::iterator_facade_base::operator++;
494 : phi_iterator_impl &operator++() {
495 : assert(PN && "Cannot increment the end iterator!");
496 : PN = dyn_cast<PHINodeT>(std::next(BBIteratorT(PN)));
497 : return *this;
498 : }
499 : };
500 : using phi_iterator = phi_iterator_impl<>;
501 : using const_phi_iterator =
502 : phi_iterator_impl<const PHINode, BasicBlock::const_iterator>;
503 :
504 : /// Returns a range that iterates over the phis in the basic block.
505 : ///
506 : /// Note that this cannot be used with basic blocks that have no terminator.
507 : iterator_range<const_phi_iterator> phis() const {
508 : return const_cast<BasicBlock *>(this)->phis();
509 : }
510 : iterator_range<phi_iterator> phis();
511 :
512 : private:
513 : /// Return the underlying instruction list container.
514 : /// This is deliberately private because we have implemented an adequate set
515 : /// of functions to modify the list, including BasicBlock::splice(),
516 : /// BasicBlock::erase(), Instruction::insertInto() etc.
517 : const InstListType &getInstList() const { return InstList; }
518 : InstListType &getInstList() { return InstList; }
519 :
520 : /// Returns a pointer to a member of the instruction list.
521 : /// This is private on purpose, just like `getInstList()`.
522 : static InstListType BasicBlock::*getSublistAccess(Instruction *) {
523 : return &BasicBlock::InstList;
524 : }
525 :
526 : /// Dedicated function for splicing debug-info: when we have an empty
527 : /// splice (i.e. zero instructions), the caller may still intend any
528 : /// debug-info in between the two "positions" to be spliced.
529 : void spliceDebugInfoEmptyBlock(BasicBlock::iterator ToIt, BasicBlock *FromBB,
530 : BasicBlock::iterator FromBeginIt,
531 : BasicBlock::iterator FromEndIt);
532 :
533 : /// Perform any debug-info specific maintenence for the given splice
534 : /// activity. In the DbgRecord debug-info representation, debug-info is not
535 : /// in instructions, and so it does not automatically move from one block
536 : /// to another.
537 : void spliceDebugInfo(BasicBlock::iterator ToIt, BasicBlock *FromBB,
538 : BasicBlock::iterator FromBeginIt,
539 : BasicBlock::iterator FromEndIt);
540 : void spliceDebugInfoImpl(BasicBlock::iterator ToIt, BasicBlock *FromBB,
541 : BasicBlock::iterator FromBeginIt,
542 : BasicBlock::iterator FromEndIt);
543 :
544 : public:
545 : /// Returns a pointer to the symbol table if one exists.
546 : ValueSymbolTable *getValueSymbolTable();
547 :
548 : /// Methods for support type inquiry through isa, cast, and dyn_cast.
549 : static bool classof(const Value *V) {
550 : return V->getValueID() == Value::BasicBlockVal;
551 : }
552 :
553 : /// Cause all subinstructions to "let go" of all the references that said
554 : /// subinstructions are maintaining.
555 : ///
556 : /// This allows one to 'delete' a whole class at a time, even though there may
557 : /// be circular references... first all references are dropped, and all use
558 : /// counts go to zero. Then everything is delete'd for real. Note that no
559 : /// operations are valid on an object that has "dropped all references",
560 : /// except operator delete.
561 : void dropAllReferences();
562 :
563 : /// Update PHI nodes in this BasicBlock before removal of predecessor \p Pred.
564 : /// Note that this function does not actually remove the predecessor.
565 : ///
566 : /// If \p KeepOneInputPHIs is true then don't remove PHIs that are left with
567 : /// zero or one incoming values, and don't simplify PHIs with all incoming
568 : /// values the same.
569 : void removePredecessor(BasicBlock *Pred, bool KeepOneInputPHIs = false);
570 :
571 : bool canSplitPredecessors() const;
572 :
573 : /// Split the basic block into two basic blocks at the specified instruction.
574 : ///
575 : /// If \p Before is true, splitBasicBlockBefore handles the
576 : /// block splitting. Otherwise, execution proceeds as described below.
577 : ///
578 : /// Note that all instructions BEFORE the specified iterator
579 : /// stay as part of the original basic block, an unconditional branch is added
580 : /// to the original BB, and the rest of the instructions in the BB are moved
581 : /// to the new BB, including the old terminator. The newly formed basic block
582 : /// is returned. This function invalidates the specified iterator.
583 : ///
584 : /// Note that this only works on well formed basic blocks (must have a
585 : /// terminator), and \p 'I' must not be the end of instruction list (which
586 : /// would cause a degenerate basic block to be formed, having a terminator
587 : /// inside of the basic block).
588 : ///
589 : /// Also note that this doesn't preserve any passes. To split blocks while
590 : /// keeping loop information consistent, use the SplitBlock utility function.
591 : BasicBlock *splitBasicBlock(iterator I, const Twine &BBName = "",
592 : bool Before = false);
593 : BasicBlock *splitBasicBlock(Instruction *I, const Twine &BBName = "",
594 : bool Before = false) {
595 : return splitBasicBlock(I->getIterator(), BBName, Before);
596 : }
597 :
598 : /// Split the basic block into two basic blocks at the specified instruction
599 : /// and insert the new basic blocks as the predecessor of the current block.
600 : ///
601 : /// This function ensures all instructions AFTER and including the specified
602 : /// iterator \p I are part of the original basic block. All Instructions
603 : /// BEFORE the iterator \p I are moved to the new BB and an unconditional
604 : /// branch is added to the new BB. The new basic block is returned.
605 : ///
606 : /// Note that this only works on well formed basic blocks (must have a
607 : /// terminator), and \p 'I' must not be the end of instruction list (which
608 : /// would cause a degenerate basic block to be formed, having a terminator
609 : /// inside of the basic block). \p 'I' cannot be a iterator for a PHINode
610 : /// with multiple incoming blocks.
611 : ///
612 : /// Also note that this doesn't preserve any passes. To split blocks while
613 : /// keeping loop information consistent, use the SplitBlockBefore utility
614 : /// function.
615 : BasicBlock *splitBasicBlockBefore(iterator I, const Twine &BBName = "");
616 : BasicBlock *splitBasicBlockBefore(Instruction *I, const Twine &BBName = "") {
617 : return splitBasicBlockBefore(I->getIterator(), BBName);
618 : }
619 :
620 : /// Transfer all instructions from \p FromBB to this basic block at \p ToIt.
621 : void splice(BasicBlock::iterator ToIt, BasicBlock *FromBB) {
622 : splice(ToIt, FromBB, FromBB->begin(), FromBB->end());
623 : }
624 :
625 : /// Transfer one instruction from \p FromBB at \p FromIt to this basic block
626 : /// at \p ToIt.
627 : void splice(BasicBlock::iterator ToIt, BasicBlock *FromBB,
628 : BasicBlock::iterator FromIt) {
629 : auto FromItNext = std::next(FromIt);
630 : // Single-element splice is a noop if destination == source.
631 : if (ToIt == FromIt || ToIt == FromItNext)
632 : return;
633 : splice(ToIt, FromBB, FromIt, FromItNext);
634 : }
635 :
636 : /// Transfer a range of instructions that belong to \p FromBB from \p
637 : /// FromBeginIt to \p FromEndIt, to this basic block at \p ToIt.
638 : void splice(BasicBlock::iterator ToIt, BasicBlock *FromBB,
639 : BasicBlock::iterator FromBeginIt,
640 : BasicBlock::iterator FromEndIt);
641 :
642 : /// Erases a range of instructions from \p FromIt to (not including) \p ToIt.
643 : /// \Returns \p ToIt.
644 : BasicBlock::iterator erase(BasicBlock::iterator FromIt, BasicBlock::iterator ToIt);
645 :
646 : /// Returns true if there are any uses of this basic block other than
647 : /// direct branches, switches, etc. to it.
648 : bool hasAddressTaken() const {
649 : return getBasicBlockBits().BlockAddressRefCount != 0;
650 : }
651 :
652 : /// Update all phi nodes in this basic block to refer to basic block \p New
653 : /// instead of basic block \p Old.
654 : void replacePhiUsesWith(BasicBlock *Old, BasicBlock *New);
655 :
656 : /// Update all phi nodes in this basic block's successors to refer to basic
657 : /// block \p New instead of basic block \p Old.
658 : void replaceSuccessorsPhiUsesWith(BasicBlock *Old, BasicBlock *New);
659 :
660 : /// Update all phi nodes in this basic block's successors to refer to basic
661 : /// block \p New instead of to it.
662 : void replaceSuccessorsPhiUsesWith(BasicBlock *New);
663 :
664 : /// Return true if this basic block is an exception handling block.
665 : bool isEHPad() const { return getFirstNonPHI()->isEHPad(); }
666 :
667 : /// Return true if this basic block is a landing pad.
668 : ///
669 : /// Being a ``landing pad'' means that the basic block is the destination of
670 : /// the 'unwind' edge of an invoke instruction.
671 : bool isLandingPad() const;
672 :
673 : /// Return the landingpad instruction associated with the landing pad.
674 : const LandingPadInst *getLandingPadInst() const;
675 : LandingPadInst *getLandingPadInst() {
676 : return const_cast<LandingPadInst *>(
677 : static_cast<const BasicBlock *>(this)->getLandingPadInst());
678 : }
679 :
680 : /// Return true if it is legal to hoist instructions into this block.
681 : bool isLegalToHoistInto() const;
682 :
683 : /// Return true if this is the entry block of the containing function.
684 : /// This method can only be used on blocks that have a parent function.
685 : bool isEntryBlock() const;
686 :
687 : std::optional<uint64_t> getIrrLoopHeaderWeight() const;
688 :
689 : /// Returns true if the Order field of child Instructions is valid.
690 : bool isInstrOrderValid() const {
691 : return getBasicBlockBits().InstrOrderValid;
692 : }
693 :
694 : /// Mark instruction ordering invalid. Done on every instruction insert.
695 : void invalidateOrders() {
696 : validateInstrOrdering();
697 : BasicBlockBits Bits = getBasicBlockBits();
698 : Bits.InstrOrderValid = false;
699 : setBasicBlockBits(Bits);
700 : }
701 :
702 : /// Renumber instructions and mark the ordering as valid.
703 : void renumberInstructions();
704 :
705 : /// Asserts that instruction order numbers are marked invalid, or that they
706 : /// are in ascending order. This is constant time if the ordering is invalid,
707 : /// and linear in the number of instructions if the ordering is valid. Callers
708 : /// should be careful not to call this in ways that make common operations
709 : /// O(n^2). For example, it takes O(n) time to assign order numbers to
710 : /// instructions, so the order should be validated no more than once after
711 : /// each ordering to ensure that transforms have the same algorithmic
712 : /// complexity when asserts are enabled as when they are disabled.
713 : void validateInstrOrdering() const;
714 :
715 : private:
716 : #if defined(_AIX) && (!defined(__GNUC__) || defined(__clang__))
717 : // Except for GCC; by default, AIX compilers store bit-fields in 4-byte words
718 : // and give the `pack` pragma push semantics.
719 : #define BEGIN_TWO_BYTE_PACK() _Pragma("pack(2)")
720 : #define END_TWO_BYTE_PACK() _Pragma("pack(pop)")
721 : #else
722 : #define BEGIN_TWO_BYTE_PACK()
723 : #define END_TWO_BYTE_PACK()
724 : #endif
725 :
726 : BEGIN_TWO_BYTE_PACK()
727 : /// Bitfield to help interpret the bits in Value::SubclassData.
728 : struct BasicBlockBits {
729 : unsigned short BlockAddressRefCount : 15;
730 : unsigned short InstrOrderValid : 1;
731 : };
732 : END_TWO_BYTE_PACK()
733 :
734 : #undef BEGIN_TWO_BYTE_PACK
735 : #undef END_TWO_BYTE_PACK
736 :
737 : /// Safely reinterpret the subclass data bits to a more useful form.
738 : BasicBlockBits getBasicBlockBits() const {
739 : static_assert(sizeof(BasicBlockBits) == sizeof(unsigned short),
740 : "too many bits for Value::SubclassData");
741 : unsigned short ValueData = getSubclassDataFromValue();
742 : BasicBlockBits AsBits;
743 : memcpy(&AsBits, &ValueData, sizeof(AsBits));
744 : return AsBits;
745 : }
746 :
747 : /// Reinterpret our subclass bits and store them back into Value.
748 : void setBasicBlockBits(BasicBlockBits AsBits) {
749 : unsigned short D;
750 : memcpy(&D, &AsBits, sizeof(D));
751 : Value::setValueSubclassData(D);
752 : }
753 :
754 : /// Increment the internal refcount of the number of BlockAddresses
755 : /// referencing this BasicBlock by \p Amt.
756 : ///
757 : /// This is almost always 0, sometimes one possibly, but almost never 2, and
758 : /// inconceivably 3 or more.
759 : void AdjustBlockAddressRefCount(int Amt) {
760 : BasicBlockBits Bits = getBasicBlockBits();
761 : Bits.BlockAddressRefCount += Amt;
762 : setBasicBlockBits(Bits);
763 : assert(Bits.BlockAddressRefCount < 255 && "Refcount wrap-around");
764 : }
765 :
766 : /// Shadow Value::setValueSubclassData with a private forwarding method so
767 : /// that any future subclasses cannot accidentally use it.
768 : void setValueSubclassData(unsigned short D) {
769 : Value::setValueSubclassData(D);
770 : }
771 : };
772 :
773 : // Create wrappers for C Binding types (see CBindingWrapping.h).
774 : DEFINE_SIMPLE_CONVERSION_FUNCTIONS(BasicBlock, LLVMBasicBlockRef)
775 :
776 : /// Advance \p It while it points to a debug instruction and return the result.
777 : /// This assumes that \p It is not at the end of a block.
778 : BasicBlock::iterator skipDebugIntrinsics(BasicBlock::iterator It);
779 :
780 : #ifdef NDEBUG
781 : /// In release builds, this is a no-op. For !NDEBUG builds, the checks are
782 : /// implemented in the .cpp file to avoid circular header deps.
783 : inline void BasicBlock::validateInstrOrdering() const {}
784 : #endif
785 :
786 : // Specialize DenseMapInfo for iterators, so that ththey can be installed into
787 : // maps and sets. The iterator is made up of its node pointer, and the
788 : // debug-info "head" bit.
789 : template <> struct DenseMapInfo<BasicBlock::iterator> {
790 : static inline BasicBlock::iterator getEmptyKey() {
791 : return BasicBlock::iterator(nullptr);
792 : }
793 :
794 : static inline BasicBlock::iterator getTombstoneKey() {
795 : BasicBlock::iterator It(nullptr);
796 : It.setHeadBit(true);
797 : return It;
798 : }
799 :
800 : static unsigned getHashValue(const BasicBlock::iterator &It) {
801 : return DenseMapInfo<void *>::getHashValue(
802 : reinterpret_cast<void *>(It.getNodePtr())) ^
803 : (unsigned)It.getHeadBit();
804 : }
805 :
806 : static bool isEqual(const BasicBlock::iterator &LHS,
807 : const BasicBlock::iterator &RHS) {
808 : return LHS == RHS && LHS.getHeadBit() == RHS.getHeadBit();
809 : }
810 : };
811 :
812 : } // end namespace llvm
813 :
814 : #endif // LLVM_IR_BASICBLOCK_H
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