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/Twine.h" 18 #include "llvm/ADT/ilist.h" 19 #include "llvm/ADT/ilist_node.h" 20 #include "llvm/ADT/iterator.h" 21 #include "llvm/ADT/iterator_range.h" 22 #include "llvm/IR/Instruction.h" 23 #include "llvm/IR/SymbolTableListTraits.h" 24 #include "llvm/IR/Value.h" 25 #include "llvm/Support/CBindingWrapping.h" 26 #include "llvm/Support/Casting.h" 27 #include "llvm/Support/Compiler.h" 28 #include <cassert> 29 #include <cstddef> 30 #include <iterator> 31 32 namespace llvm { 33 34 class AssemblyAnnotationWriter; 35 class CallInst; 36 class Function; 37 class LandingPadInst; 38 class LLVMContext; 39 class Module; 40 class PHINode; 41 class ValueSymbolTable; 42 43 /// LLVM Basic Block Representation 44 /// 45 /// This represents a single basic block in LLVM. A basic block is simply a 46 /// container of instructions that execute sequentially. Basic blocks are Values 47 /// because they are referenced by instructions such as branches and switch 48 /// tables. The type of a BasicBlock is "Type::LabelTy" because the basic block 49 /// represents a label to which a branch can jump. 50 /// 51 /// A well formed basic block is formed of a list of non-terminating 52 /// instructions followed by a single terminator instruction. Terminator 53 /// instructions may not occur in the middle of basic blocks, and must terminate 54 /// the blocks. The BasicBlock class allows malformed basic blocks to occur 55 /// because it may be useful in the intermediate stage of constructing or 56 /// modifying a program. However, the verifier will ensure that basic blocks are 57 /// "well formed". 58 class BasicBlock final : public Value, // Basic blocks are data objects also 59 public ilist_node_with_parent<BasicBlock, Function> { 60 public: 61 using InstListType = SymbolTableList<Instruction>; 62 63 private: 64 friend class BlockAddress; 65 friend class SymbolTableListTraits<BasicBlock>; 66 67 InstListType InstList; 68 Function *Parent; 69 70 void setParent(Function *parent); 71 72 /// Constructor. 73 /// 74 /// If the function parameter is specified, the basic block is automatically 75 /// inserted at either the end of the function (if InsertBefore is null), or 76 /// before the specified basic block. 77 explicit BasicBlock(LLVMContext &C, const Twine &Name = "", 78 Function *Parent = nullptr, 79 BasicBlock *InsertBefore = nullptr); 80 81 public: 82 BasicBlock(const BasicBlock &) = delete; 83 BasicBlock &operator=(const BasicBlock &) = delete; 84 ~BasicBlock(); 85 86 /// Get the context in which this basic block lives. 87 LLVMContext &getContext() const; 88 89 /// Instruction iterators... 90 using iterator = InstListType::iterator; 91 using const_iterator = InstListType::const_iterator; 92 using reverse_iterator = InstListType::reverse_iterator; 93 using const_reverse_iterator = InstListType::const_reverse_iterator; 94 95 /// Creates a new BasicBlock. 96 /// 97 /// If the Parent parameter is specified, the basic block is automatically 98 /// inserted at either the end of the function (if InsertBefore is 0), or 99 /// before the specified basic block. 100 static BasicBlock *Create(LLVMContext &Context, const Twine &Name = "", 101 Function *Parent = nullptr, 102 BasicBlock *InsertBefore = nullptr) { 103 return new BasicBlock(Context, Name, Parent, InsertBefore); 104 } 105 106 /// Return the enclosing method, or null if none. 107 const Function *getParent() const { return Parent; } 108 Function *getParent() { return Parent; } 109 110 /// Return the module owning the function this basic block belongs to, or 111 /// nullptr if the function does not have a module. 112 /// 113 /// Note: this is undefined behavior if the block does not have a parent. 114 const Module *getModule() const; 115 Module *getModule() { 116 return const_cast<Module *>( 117 static_cast<const BasicBlock *>(this)->getModule()); 118 } 119 120 /// Returns the terminator instruction if the block is well formed or null 121 /// if the block is not well formed. 122 const Instruction *getTerminator() const LLVM_READONLY; 123 Instruction *getTerminator() { 124 return const_cast<Instruction *>( 125 static_cast<const BasicBlock *>(this)->getTerminator()); 126 } 127 128 /// Returns the call instruction calling \@llvm.experimental.deoptimize 129 /// prior to the terminating return instruction of this basic block, if such 130 /// a call is present. Otherwise, returns null. 131 const CallInst *getTerminatingDeoptimizeCall() const; 132 CallInst *getTerminatingDeoptimizeCall() { 133 return const_cast<CallInst *>( 134 static_cast<const BasicBlock *>(this)->getTerminatingDeoptimizeCall()); 135 } 136 137 /// Returns the call instruction calling \@llvm.experimental.deoptimize 138 /// that is present either in current basic block or in block that is a unique 139 /// successor to current block, if such call is present. Otherwise, returns null. 140 const CallInst *getPostdominatingDeoptimizeCall() const; 141 CallInst *getPostdominatingDeoptimizeCall() { 142 return const_cast<CallInst *>( 143 static_cast<const BasicBlock *>(this)->getPostdominatingDeoptimizeCall()); 144 } 145 146 /// Returns the call instruction marked 'musttail' prior to the terminating 147 /// return instruction of this basic block, if such a call is present. 148 /// Otherwise, returns null. 149 const CallInst *getTerminatingMustTailCall() const; 150 CallInst *getTerminatingMustTailCall() { 151 return const_cast<CallInst *>( 152 static_cast<const BasicBlock *>(this)->getTerminatingMustTailCall()); 153 } 154 155 /// Returns a pointer to the first instruction in this block that is not a 156 /// PHINode instruction. 157 /// 158 /// When adding instructions to the beginning of the basic block, they should 159 /// be added before the returned value, not before the first instruction, 160 /// which might be PHI. Returns 0 is there's no non-PHI instruction. 161 const Instruction* getFirstNonPHI() const; 162 Instruction* getFirstNonPHI() { 163 return const_cast<Instruction *>( 164 static_cast<const BasicBlock *>(this)->getFirstNonPHI()); 165 } 166 167 /// Returns a pointer to the first instruction in this block that is not a 168 /// PHINode or a debug intrinsic, or any pseudo operation if \c SkipPseudoOp 169 /// is true. 170 const Instruction *getFirstNonPHIOrDbg(bool SkipPseudoOp = false) const; 171 Instruction *getFirstNonPHIOrDbg(bool SkipPseudoOp = false) { 172 return const_cast<Instruction *>( 173 static_cast<const BasicBlock *>(this)->getFirstNonPHIOrDbg( 174 SkipPseudoOp)); 175 } 176 177 /// Returns a pointer to the first instruction in this block that is not a 178 /// PHINode, a debug intrinsic, or a lifetime intrinsic, or any pseudo 179 /// operation if \c SkipPseudoOp is true. 180 const Instruction * 181 getFirstNonPHIOrDbgOrLifetime(bool SkipPseudoOp = false) const; 182 Instruction *getFirstNonPHIOrDbgOrLifetime(bool SkipPseudoOp = false) { 183 return const_cast<Instruction *>( 184 static_cast<const BasicBlock *>(this)->getFirstNonPHIOrDbgOrLifetime( 185 SkipPseudoOp)); 186 } 187 188 /// Returns an iterator to the first instruction in this block that is 189 /// suitable for inserting a non-PHI instruction. 190 /// 191 /// In particular, it skips all PHIs and LandingPad instructions. 192 const_iterator getFirstInsertionPt() const; 193 iterator getFirstInsertionPt() { 194 return static_cast<const BasicBlock *>(this) 195 ->getFirstInsertionPt().getNonConst(); 196 } 197 198 /// Return a const iterator range over the instructions in the block, skipping 199 /// any debug instructions. Skip any pseudo operations as well if \c 200 /// SkipPseudoOp is true. 201 iterator_range<filter_iterator<BasicBlock::const_iterator, 202 std::function<bool(const Instruction &)>>> 203 instructionsWithoutDebug(bool SkipPseudoOp = false) const; 204 205 /// Return an iterator range over the instructions in the block, skipping any 206 /// debug instructions. Skip and any pseudo operations as well if \c 207 /// SkipPseudoOp is true. 208 iterator_range< 209 filter_iterator<BasicBlock::iterator, std::function<bool(Instruction &)>>> 210 instructionsWithoutDebug(bool SkipPseudoOp = false); 211 212 /// Return the size of the basic block ignoring debug instructions 213 filter_iterator<BasicBlock::const_iterator, 214 std::function<bool(const Instruction &)>>::difference_type 215 sizeWithoutDebug() const; 216 217 /// Unlink 'this' from the containing function, but do not delete it. 218 void removeFromParent(); 219 220 /// Unlink 'this' from the containing function and delete it. 221 /// 222 // \returns an iterator pointing to the element after the erased one. 223 SymbolTableList<BasicBlock>::iterator eraseFromParent(); 224 225 /// Unlink this basic block from its current function and insert it into 226 /// the function that \p MovePos lives in, right before \p MovePos. 227 void moveBefore(BasicBlock *MovePos); 228 229 /// Unlink this basic block from its current function and insert it 230 /// right after \p MovePos in the function \p MovePos lives in. 231 void moveAfter(BasicBlock *MovePos); 232 233 /// Insert unlinked basic block into a function. 234 /// 235 /// Inserts an unlinked basic block into \c Parent. If \c InsertBefore is 236 /// provided, inserts before that basic block, otherwise inserts at the end. 237 /// 238 /// \pre \a getParent() is \c nullptr. 239 void insertInto(Function *Parent, BasicBlock *InsertBefore = nullptr); 240 241 /// Return the predecessor of this block if it has a single predecessor 242 /// block. Otherwise return a null pointer. 243 const BasicBlock *getSinglePredecessor() const; 244 BasicBlock *getSinglePredecessor() { 245 return const_cast<BasicBlock *>( 246 static_cast<const BasicBlock *>(this)->getSinglePredecessor()); 247 } 248 249 /// Return the predecessor of this block if it has a unique predecessor 250 /// block. Otherwise return a null pointer. 251 /// 252 /// Note that unique predecessor doesn't mean single edge, there can be 253 /// multiple edges from the unique predecessor to this block (for example a 254 /// switch statement with multiple cases having the same destination). 255 const BasicBlock *getUniquePredecessor() const; 256 BasicBlock *getUniquePredecessor() { 257 return const_cast<BasicBlock *>( 258 static_cast<const BasicBlock *>(this)->getUniquePredecessor()); 259 } 260 261 /// Return true if this block has exactly N predecessors. 262 bool hasNPredecessors(unsigned N) const; 263 264 /// Return true if this block has N predecessors or more. 265 bool hasNPredecessorsOrMore(unsigned N) const; 266 267 /// Return the successor of this block if it has a single successor. 268 /// Otherwise return a null pointer. 269 /// 270 /// This method is analogous to getSinglePredecessor above. 271 const BasicBlock *getSingleSuccessor() const; 272 BasicBlock *getSingleSuccessor() { 273 return const_cast<BasicBlock *>( 274 static_cast<const BasicBlock *>(this)->getSingleSuccessor()); 275 } 276 277 /// Return the successor of this block if it has a unique successor. 278 /// Otherwise return a null pointer. 279 /// 280 /// This method is analogous to getUniquePredecessor above. 281 const BasicBlock *getUniqueSuccessor() const; 282 BasicBlock *getUniqueSuccessor() { 283 return const_cast<BasicBlock *>( 284 static_cast<const BasicBlock *>(this)->getUniqueSuccessor()); 285 } 286 287 /// Print the basic block to an output stream with an optional 288 /// AssemblyAnnotationWriter. 289 void print(raw_ostream &OS, AssemblyAnnotationWriter *AAW = nullptr, 290 bool ShouldPreserveUseListOrder = false, 291 bool IsForDebug = false) const; 292 293 //===--------------------------------------------------------------------===// 294 /// Instruction iterator methods 295 /// 296 inline iterator begin() { return InstList.begin(); } 297 inline const_iterator begin() const { return InstList.begin(); } 298 inline iterator end () { return InstList.end(); } 299 inline const_iterator end () const { return InstList.end(); } 300 301 inline reverse_iterator rbegin() { return InstList.rbegin(); } 302 inline const_reverse_iterator rbegin() const { return InstList.rbegin(); } 303 inline reverse_iterator rend () { return InstList.rend(); } 304 inline const_reverse_iterator rend () const { return InstList.rend(); } 305 306 inline size_t size() const { return InstList.size(); } 307 inline bool empty() const { return InstList.empty(); } 308 inline const Instruction &front() const { return InstList.front(); } 309 inline Instruction &front() { return InstList.front(); } 310 inline const Instruction &back() const { return InstList.back(); } 311 inline Instruction &back() { return InstList.back(); } 312 313 /// Iterator to walk just the phi nodes in the basic block. 314 template <typename PHINodeT = PHINode, typename BBIteratorT = iterator> 315 class phi_iterator_impl 316 : public iterator_facade_base<phi_iterator_impl<PHINodeT, BBIteratorT>, 317 std::forward_iterator_tag, PHINodeT> { 318 friend BasicBlock; 319 320 PHINodeT *PN; 321 322 phi_iterator_impl(PHINodeT *PN) : PN(PN) {} 323 324 public: 325 // Allow default construction to build variables, but this doesn't build 326 // a useful iterator. 327 phi_iterator_impl() = default; 328 329 // Allow conversion between instantiations where valid. 330 template <typename PHINodeU, typename BBIteratorU, 331 typename = std::enable_if_t< 332 std::is_convertible<PHINodeU *, PHINodeT *>::value>> 333 phi_iterator_impl(const phi_iterator_impl<PHINodeU, BBIteratorU> &Arg) 334 : PN(Arg.PN) {} 335 336 bool operator==(const phi_iterator_impl &Arg) const { return PN == Arg.PN; } 337 338 PHINodeT &operator*() const { return *PN; } 339 340 using phi_iterator_impl::iterator_facade_base::operator++; 341 phi_iterator_impl &operator++() { 342 assert(PN && "Cannot increment the end iterator!"); 343 PN = dyn_cast<PHINodeT>(std::next(BBIteratorT(PN))); 344 return *this; 345 } 346 }; 347 using phi_iterator = phi_iterator_impl<>; 348 using const_phi_iterator = 349 phi_iterator_impl<const PHINode, BasicBlock::const_iterator>; 350 351 /// Returns a range that iterates over the phis in the basic block. 352 /// 353 /// Note that this cannot be used with basic blocks that have no terminator. 354 iterator_range<const_phi_iterator> phis() const { 355 return const_cast<BasicBlock *>(this)->phis(); 356 } 357 iterator_range<phi_iterator> phis(); 358 359 /// Return the underlying instruction list container. 360 /// 361 /// Currently you need to access the underlying instruction list container 362 /// directly if you want to modify it. 363 const InstListType &getInstList() const { return InstList; } 364 InstListType &getInstList() { return InstList; } 365 366 /// Returns a pointer to a member of the instruction list. 367 static InstListType BasicBlock::*getSublistAccess(Instruction*) { 368 return &BasicBlock::InstList; 369 } 370 371 /// Returns a pointer to the symbol table if one exists. 372 ValueSymbolTable *getValueSymbolTable(); 373 374 /// Methods for support type inquiry through isa, cast, and dyn_cast. 375 static bool classof(const Value *V) { 376 return V->getValueID() == Value::BasicBlockVal; 377 } 378 379 /// Cause all subinstructions to "let go" of all the references that said 380 /// subinstructions are maintaining. 381 /// 382 /// This allows one to 'delete' a whole class at a time, even though there may 383 /// be circular references... first all references are dropped, and all use 384 /// counts go to zero. Then everything is delete'd for real. Note that no 385 /// operations are valid on an object that has "dropped all references", 386 /// except operator delete. 387 void dropAllReferences(); 388 389 /// Update PHI nodes in this BasicBlock before removal of predecessor \p Pred. 390 /// Note that this function does not actually remove the predecessor. 391 /// 392 /// If \p KeepOneInputPHIs is true then don't remove PHIs that are left with 393 /// zero or one incoming values, and don't simplify PHIs with all incoming 394 /// values the same. 395 void removePredecessor(BasicBlock *Pred, bool KeepOneInputPHIs = false); 396 397 bool canSplitPredecessors() const; 398 399 /// Split the basic block into two basic blocks at the specified instruction. 400 /// 401 /// If \p Before is true, splitBasicBlockBefore handles the 402 /// block splitting. Otherwise, execution proceeds as described below. 403 /// 404 /// Note that all instructions BEFORE the specified iterator 405 /// stay as part of the original basic block, an unconditional branch is added 406 /// to the original BB, and the rest of the instructions in the BB are moved 407 /// to the new BB, including the old terminator. The newly formed basic block 408 /// is returned. This function invalidates the specified iterator. 409 /// 410 /// Note that this only works on well formed basic blocks (must have a 411 /// terminator), and \p 'I' must not be the end of instruction list (which 412 /// would cause a degenerate basic block to be formed, having a terminator 413 /// inside of the basic block). 414 /// 415 /// Also note that this doesn't preserve any passes. To split blocks while 416 /// keeping loop information consistent, use the SplitBlock utility function. 417 BasicBlock *splitBasicBlock(iterator I, const Twine &BBName = "", 418 bool Before = false); 419 BasicBlock *splitBasicBlock(Instruction *I, const Twine &BBName = "", 420 bool Before = false) { 421 return splitBasicBlock(I->getIterator(), BBName, Before); 422 } 423 424 /// Split the basic block into two basic blocks at the specified instruction 425 /// and insert the new basic blocks as the predecessor of the current block. 426 /// 427 /// This function ensures all instructions AFTER and including the specified 428 /// iterator \p I are part of the original basic block. All Instructions 429 /// BEFORE the iterator \p I are moved to the new BB and an unconditional 430 /// branch is added to the new BB. The new basic block is returned. 431 /// 432 /// Note that this only works on well formed basic blocks (must have a 433 /// terminator), and \p 'I' must not be the end of instruction list (which 434 /// would cause a degenerate basic block to be formed, having a terminator 435 /// inside of the basic block). \p 'I' cannot be a iterator for a PHINode 436 /// with multiple incoming blocks. 437 /// 438 /// Also note that this doesn't preserve any passes. To split blocks while 439 /// keeping loop information consistent, use the SplitBlockBefore utility 440 /// function. 441 BasicBlock *splitBasicBlockBefore(iterator I, const Twine &BBName = ""); 442 BasicBlock *splitBasicBlockBefore(Instruction *I, const Twine &BBName = "") { 443 return splitBasicBlockBefore(I->getIterator(), BBName); 444 } 445 446 /// Returns true if there are any uses of this basic block other than 447 /// direct branches, switches, etc. to it. 448 bool hasAddressTaken() const { 449 return getBasicBlockBits().BlockAddressRefCount != 0; 450 } 451 452 /// Update all phi nodes in this basic block to refer to basic block \p New 453 /// instead of basic block \p Old. 454 void replacePhiUsesWith(BasicBlock *Old, BasicBlock *New); 455 456 /// Update all phi nodes in this basic block's successors to refer to basic 457 /// block \p New instead of basic block \p Old. 458 void replaceSuccessorsPhiUsesWith(BasicBlock *Old, BasicBlock *New); 459 460 /// Update all phi nodes in this basic block's successors to refer to basic 461 /// block \p New instead of to it. 462 void replaceSuccessorsPhiUsesWith(BasicBlock *New); 463 464 /// Return true if this basic block is an exception handling block. 465 bool isEHPad() const { return getFirstNonPHI()->isEHPad(); } 466 467 /// Return true if this basic block is a landing pad. 468 /// 469 /// Being a ``landing pad'' means that the basic block is the destination of 470 /// the 'unwind' edge of an invoke instruction. 471 bool isLandingPad() const; 472 473 /// Return the landingpad instruction associated with the landing pad. 474 const LandingPadInst *getLandingPadInst() const; 475 LandingPadInst *getLandingPadInst() { 476 return const_cast<LandingPadInst *>( 477 static_cast<const BasicBlock *>(this)->getLandingPadInst()); 478 } 479 480 /// Return true if it is legal to hoist instructions into this block. 481 bool isLegalToHoistInto() const; 482 483 Optional<uint64_t> getIrrLoopHeaderWeight() const; 484 485 /// Returns true if the Order field of child Instructions is valid. 486 bool isInstrOrderValid() const { 487 return getBasicBlockBits().InstrOrderValid; 488 } 489 490 /// Mark instruction ordering invalid. Done on every instruction insert. 491 void invalidateOrders() { 492 validateInstrOrdering(); 493 BasicBlockBits Bits = getBasicBlockBits(); 494 Bits.InstrOrderValid = false; 495 setBasicBlockBits(Bits); 496 } 497 498 /// Renumber instructions and mark the ordering as valid. 499 void renumberInstructions(); 500 501 /// Asserts that instruction order numbers are marked invalid, or that they 502 /// are in ascending order. This is constant time if the ordering is invalid, 503 /// and linear in the number of instructions if the ordering is valid. Callers 504 /// should be careful not to call this in ways that make common operations 505 /// O(n^2). For example, it takes O(n) time to assign order numbers to 506 /// instructions, so the order should be validated no more than once after 507 /// each ordering to ensure that transforms have the same algorithmic 508 /// complexity when asserts are enabled as when they are disabled. 509 void validateInstrOrdering() const; 510 511 private: 512 #if defined(_AIX) && (!defined(__GNUC__) || defined(__ibmxl__)) 513 // Except for GCC; by default, AIX compilers store bit-fields in 4-byte words 514 // and give the `pack` pragma push semantics. 515 #define BEGIN_TWO_BYTE_PACK() _Pragma("pack(2)") 516 #define END_TWO_BYTE_PACK() _Pragma("pack(pop)") 517 #else 518 #define BEGIN_TWO_BYTE_PACK() 519 #define END_TWO_BYTE_PACK() 520 #endif 521 522 BEGIN_TWO_BYTE_PACK() 523 /// Bitfield to help interpret the bits in Value::SubclassData. 524 struct BasicBlockBits { 525 unsigned short BlockAddressRefCount : 15; 526 unsigned short InstrOrderValid : 1; 527 }; 528 END_TWO_BYTE_PACK() 529 530 #undef BEGIN_TWO_BYTE_PACK 531 #undef END_TWO_BYTE_PACK 532 533 /// Safely reinterpret the subclass data bits to a more useful form. 534 BasicBlockBits getBasicBlockBits() const { 535 static_assert(sizeof(BasicBlockBits) == sizeof(unsigned short), 536 "too many bits for Value::SubclassData"); 537 unsigned short ValueData = getSubclassDataFromValue(); 538 BasicBlockBits AsBits; 539 memcpy(&AsBits, &ValueData, sizeof(AsBits)); 540 return AsBits; 541 } 542 543 /// Reinterpret our subclass bits and store them back into Value. 544 void setBasicBlockBits(BasicBlockBits AsBits) { 545 unsigned short D; 546 memcpy(&D, &AsBits, sizeof(D)); 547 Value::setValueSubclassData(D); 548 } 549 550 /// Increment the internal refcount of the number of BlockAddresses 551 /// referencing this BasicBlock by \p Amt. 552 /// 553 /// This is almost always 0, sometimes one possibly, but almost never 2, and 554 /// inconceivably 3 or more. 555 void AdjustBlockAddressRefCount(int Amt) { 556 BasicBlockBits Bits = getBasicBlockBits(); 557 Bits.BlockAddressRefCount += Amt; 558 setBasicBlockBits(Bits); 559 assert(Bits.BlockAddressRefCount < 255 && "Refcount wrap-around"); 560 } 561 562 /// Shadow Value::setValueSubclassData with a private forwarding method so 563 /// that any future subclasses cannot accidentally use it. 564 void setValueSubclassData(unsigned short D) { 565 Value::setValueSubclassData(D); 566 } 567 }; 568 569 // Create wrappers for C Binding types (see CBindingWrapping.h). 570 DEFINE_SIMPLE_CONVERSION_FUNCTIONS(BasicBlock, LLVMBasicBlockRef) 571 572 /// Advance \p It while it points to a debug instruction and return the result. 573 /// This assumes that \p It is not at the end of a block. 574 BasicBlock::iterator skipDebugIntrinsics(BasicBlock::iterator It); 575 576 #ifdef NDEBUG 577 /// In release builds, this is a no-op. For !NDEBUG builds, the checks are 578 /// implemented in the .cpp file to avoid circular header deps. 579 inline void BasicBlock::validateInstrOrdering() const {} 580 #endif 581 582 } // end namespace llvm 583 584 #endif // LLVM_IR_BASICBLOCK_H 585