MachineBasicBlock.h revision 360660
1//===- llvm/CodeGen/MachineBasicBlock.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// 9// Collect the sequence of machine instructions for a basic block. 10// 11//===----------------------------------------------------------------------===// 12 13#ifndef LLVM_CODEGEN_MACHINEBASICBLOCK_H 14#define LLVM_CODEGEN_MACHINEBASICBLOCK_H 15 16#include "llvm/ADT/GraphTraits.h" 17#include "llvm/ADT/ilist.h" 18#include "llvm/ADT/ilist_node.h" 19#include "llvm/ADT/iterator_range.h" 20#include "llvm/ADT/simple_ilist.h" 21#include "llvm/CodeGen/MachineInstr.h" 22#include "llvm/CodeGen/MachineInstrBundleIterator.h" 23#include "llvm/IR/DebugLoc.h" 24#include "llvm/MC/LaneBitmask.h" 25#include "llvm/MC/MCRegisterInfo.h" 26#include "llvm/Support/BranchProbability.h" 27#include "llvm/Support/Printable.h" 28#include <cassert> 29#include <cstdint> 30#include <functional> 31#include <iterator> 32#include <string> 33#include <vector> 34 35namespace llvm { 36 37class BasicBlock; 38class MachineFunction; 39class MCSymbol; 40class ModuleSlotTracker; 41class Pass; 42class SlotIndexes; 43class StringRef; 44class raw_ostream; 45class TargetRegisterClass; 46class TargetRegisterInfo; 47 48template <> struct ilist_traits<MachineInstr> { 49private: 50 friend class MachineBasicBlock; // Set by the owning MachineBasicBlock. 51 52 MachineBasicBlock *Parent; 53 54 using instr_iterator = 55 simple_ilist<MachineInstr, ilist_sentinel_tracking<true>>::iterator; 56 57public: 58 void addNodeToList(MachineInstr *N); 59 void removeNodeFromList(MachineInstr *N); 60 void transferNodesFromList(ilist_traits &FromList, instr_iterator First, 61 instr_iterator Last); 62 void deleteNode(MachineInstr *MI); 63}; 64 65class MachineBasicBlock 66 : public ilist_node_with_parent<MachineBasicBlock, MachineFunction> { 67public: 68 /// Pair of physical register and lane mask. 69 /// This is not simply a std::pair typedef because the members should be named 70 /// clearly as they both have an integer type. 71 struct RegisterMaskPair { 72 public: 73 MCPhysReg PhysReg; 74 LaneBitmask LaneMask; 75 76 RegisterMaskPair(MCPhysReg PhysReg, LaneBitmask LaneMask) 77 : PhysReg(PhysReg), LaneMask(LaneMask) {} 78 }; 79 80private: 81 using Instructions = ilist<MachineInstr, ilist_sentinel_tracking<true>>; 82 83 Instructions Insts; 84 const BasicBlock *BB; 85 int Number; 86 MachineFunction *xParent; 87 88 /// Keep track of the predecessor / successor basic blocks. 89 std::vector<MachineBasicBlock *> Predecessors; 90 std::vector<MachineBasicBlock *> Successors; 91 92 /// Keep track of the probabilities to the successors. This vector has the 93 /// same order as Successors, or it is empty if we don't use it (disable 94 /// optimization). 95 std::vector<BranchProbability> Probs; 96 using probability_iterator = std::vector<BranchProbability>::iterator; 97 using const_probability_iterator = 98 std::vector<BranchProbability>::const_iterator; 99 100 Optional<uint64_t> IrrLoopHeaderWeight; 101 102 /// Keep track of the physical registers that are livein of the basicblock. 103 using LiveInVector = std::vector<RegisterMaskPair>; 104 LiveInVector LiveIns; 105 106 /// Alignment of the basic block. Zero if the basic block does not need to be 107 /// aligned. The alignment is specified as log2(bytes). 108 unsigned Alignment = 0; 109 110 /// Indicate that this basic block is entered via an exception handler. 111 bool IsEHPad = false; 112 113 /// Indicate that this basic block is potentially the target of an indirect 114 /// branch. 115 bool AddressTaken = false; 116 117 /// Indicate that this basic block needs its symbol be emitted regardless of 118 /// whether the flow just falls-through to it. 119 bool LabelMustBeEmitted = false; 120 121 /// Indicate that this basic block is the entry block of an EH scope, i.e., 122 /// the block that used to have a catchpad or cleanuppad instruction in the 123 /// LLVM IR. 124 bool IsEHScopeEntry = false; 125 126 /// Indicate that this basic block is the entry block of an EH funclet. 127 bool IsEHFuncletEntry = false; 128 129 /// Indicate that this basic block is the entry block of a cleanup funclet. 130 bool IsCleanupFuncletEntry = false; 131 132 /// since getSymbol is a relatively heavy-weight operation, the symbol 133 /// is only computed once and is cached. 134 mutable MCSymbol *CachedMCSymbol = nullptr; 135 136 // Intrusive list support 137 MachineBasicBlock() = default; 138 139 explicit MachineBasicBlock(MachineFunction &MF, const BasicBlock *BB); 140 141 ~MachineBasicBlock(); 142 143 // MachineBasicBlocks are allocated and owned by MachineFunction. 144 friend class MachineFunction; 145 146public: 147 /// Return the LLVM basic block that this instance corresponded to originally. 148 /// Note that this may be NULL if this instance does not correspond directly 149 /// to an LLVM basic block. 150 const BasicBlock *getBasicBlock() const { return BB; } 151 152 /// Return the name of the corresponding LLVM basic block, or an empty string. 153 StringRef getName() const; 154 155 /// Return a formatted string to identify this block and its parent function. 156 std::string getFullName() const; 157 158 /// Test whether this block is potentially the target of an indirect branch. 159 bool hasAddressTaken() const { return AddressTaken; } 160 161 /// Set this block to reflect that it potentially is the target of an indirect 162 /// branch. 163 void setHasAddressTaken() { AddressTaken = true; } 164 165 /// Test whether this block must have its label emitted. 166 bool hasLabelMustBeEmitted() const { return LabelMustBeEmitted; } 167 168 /// Set this block to reflect that, regardless how we flow to it, we need 169 /// its label be emitted. 170 void setLabelMustBeEmitted() { LabelMustBeEmitted = true; } 171 172 /// Return the MachineFunction containing this basic block. 173 const MachineFunction *getParent() const { return xParent; } 174 MachineFunction *getParent() { return xParent; } 175 176 using instr_iterator = Instructions::iterator; 177 using const_instr_iterator = Instructions::const_iterator; 178 using reverse_instr_iterator = Instructions::reverse_iterator; 179 using const_reverse_instr_iterator = Instructions::const_reverse_iterator; 180 181 using iterator = MachineInstrBundleIterator<MachineInstr>; 182 using const_iterator = MachineInstrBundleIterator<const MachineInstr>; 183 using reverse_iterator = MachineInstrBundleIterator<MachineInstr, true>; 184 using const_reverse_iterator = 185 MachineInstrBundleIterator<const MachineInstr, true>; 186 187 unsigned size() const { return (unsigned)Insts.size(); } 188 bool empty() const { return Insts.empty(); } 189 190 MachineInstr &instr_front() { return Insts.front(); } 191 MachineInstr &instr_back() { return Insts.back(); } 192 const MachineInstr &instr_front() const { return Insts.front(); } 193 const MachineInstr &instr_back() const { return Insts.back(); } 194 195 MachineInstr &front() { return Insts.front(); } 196 MachineInstr &back() { return *--end(); } 197 const MachineInstr &front() const { return Insts.front(); } 198 const MachineInstr &back() const { return *--end(); } 199 200 instr_iterator instr_begin() { return Insts.begin(); } 201 const_instr_iterator instr_begin() const { return Insts.begin(); } 202 instr_iterator instr_end() { return Insts.end(); } 203 const_instr_iterator instr_end() const { return Insts.end(); } 204 reverse_instr_iterator instr_rbegin() { return Insts.rbegin(); } 205 const_reverse_instr_iterator instr_rbegin() const { return Insts.rbegin(); } 206 reverse_instr_iterator instr_rend () { return Insts.rend(); } 207 const_reverse_instr_iterator instr_rend () const { return Insts.rend(); } 208 209 using instr_range = iterator_range<instr_iterator>; 210 using const_instr_range = iterator_range<const_instr_iterator>; 211 instr_range instrs() { return instr_range(instr_begin(), instr_end()); } 212 const_instr_range instrs() const { 213 return const_instr_range(instr_begin(), instr_end()); 214 } 215 216 iterator begin() { return instr_begin(); } 217 const_iterator begin() const { return instr_begin(); } 218 iterator end () { return instr_end(); } 219 const_iterator end () const { return instr_end(); } 220 reverse_iterator rbegin() { 221 return reverse_iterator::getAtBundleBegin(instr_rbegin()); 222 } 223 const_reverse_iterator rbegin() const { 224 return const_reverse_iterator::getAtBundleBegin(instr_rbegin()); 225 } 226 reverse_iterator rend() { return reverse_iterator(instr_rend()); } 227 const_reverse_iterator rend() const { 228 return const_reverse_iterator(instr_rend()); 229 } 230 231 /// Support for MachineInstr::getNextNode(). 232 static Instructions MachineBasicBlock::*getSublistAccess(MachineInstr *) { 233 return &MachineBasicBlock::Insts; 234 } 235 236 inline iterator_range<iterator> terminators() { 237 return make_range(getFirstTerminator(), end()); 238 } 239 inline iterator_range<const_iterator> terminators() const { 240 return make_range(getFirstTerminator(), end()); 241 } 242 243 /// Returns a range that iterates over the phis in the basic block. 244 inline iterator_range<iterator> phis() { 245 return make_range(begin(), getFirstNonPHI()); 246 } 247 inline iterator_range<const_iterator> phis() const { 248 return const_cast<MachineBasicBlock *>(this)->phis(); 249 } 250 251 // Machine-CFG iterators 252 using pred_iterator = std::vector<MachineBasicBlock *>::iterator; 253 using const_pred_iterator = std::vector<MachineBasicBlock *>::const_iterator; 254 using succ_iterator = std::vector<MachineBasicBlock *>::iterator; 255 using const_succ_iterator = std::vector<MachineBasicBlock *>::const_iterator; 256 using pred_reverse_iterator = 257 std::vector<MachineBasicBlock *>::reverse_iterator; 258 using const_pred_reverse_iterator = 259 std::vector<MachineBasicBlock *>::const_reverse_iterator; 260 using succ_reverse_iterator = 261 std::vector<MachineBasicBlock *>::reverse_iterator; 262 using const_succ_reverse_iterator = 263 std::vector<MachineBasicBlock *>::const_reverse_iterator; 264 pred_iterator pred_begin() { return Predecessors.begin(); } 265 const_pred_iterator pred_begin() const { return Predecessors.begin(); } 266 pred_iterator pred_end() { return Predecessors.end(); } 267 const_pred_iterator pred_end() const { return Predecessors.end(); } 268 pred_reverse_iterator pred_rbegin() 269 { return Predecessors.rbegin();} 270 const_pred_reverse_iterator pred_rbegin() const 271 { return Predecessors.rbegin();} 272 pred_reverse_iterator pred_rend() 273 { return Predecessors.rend(); } 274 const_pred_reverse_iterator pred_rend() const 275 { return Predecessors.rend(); } 276 unsigned pred_size() const { 277 return (unsigned)Predecessors.size(); 278 } 279 bool pred_empty() const { return Predecessors.empty(); } 280 succ_iterator succ_begin() { return Successors.begin(); } 281 const_succ_iterator succ_begin() const { return Successors.begin(); } 282 succ_iterator succ_end() { return Successors.end(); } 283 const_succ_iterator succ_end() const { return Successors.end(); } 284 succ_reverse_iterator succ_rbegin() 285 { return Successors.rbegin(); } 286 const_succ_reverse_iterator succ_rbegin() const 287 { return Successors.rbegin(); } 288 succ_reverse_iterator succ_rend() 289 { return Successors.rend(); } 290 const_succ_reverse_iterator succ_rend() const 291 { return Successors.rend(); } 292 unsigned succ_size() const { 293 return (unsigned)Successors.size(); 294 } 295 bool succ_empty() const { return Successors.empty(); } 296 297 inline iterator_range<pred_iterator> predecessors() { 298 return make_range(pred_begin(), pred_end()); 299 } 300 inline iterator_range<const_pred_iterator> predecessors() const { 301 return make_range(pred_begin(), pred_end()); 302 } 303 inline iterator_range<succ_iterator> successors() { 304 return make_range(succ_begin(), succ_end()); 305 } 306 inline iterator_range<const_succ_iterator> successors() const { 307 return make_range(succ_begin(), succ_end()); 308 } 309 310 // LiveIn management methods. 311 312 /// Adds the specified register as a live in. Note that it is an error to add 313 /// the same register to the same set more than once unless the intention is 314 /// to call sortUniqueLiveIns after all registers are added. 315 void addLiveIn(MCPhysReg PhysReg, 316 LaneBitmask LaneMask = LaneBitmask::getAll()) { 317 LiveIns.push_back(RegisterMaskPair(PhysReg, LaneMask)); 318 } 319 void addLiveIn(const RegisterMaskPair &RegMaskPair) { 320 LiveIns.push_back(RegMaskPair); 321 } 322 323 /// Sorts and uniques the LiveIns vector. It can be significantly faster to do 324 /// this than repeatedly calling isLiveIn before calling addLiveIn for every 325 /// LiveIn insertion. 326 void sortUniqueLiveIns(); 327 328 /// Clear live in list. 329 void clearLiveIns(); 330 331 /// Add PhysReg as live in to this block, and ensure that there is a copy of 332 /// PhysReg to a virtual register of class RC. Return the virtual register 333 /// that is a copy of the live in PhysReg. 334 unsigned addLiveIn(MCPhysReg PhysReg, const TargetRegisterClass *RC); 335 336 /// Remove the specified register from the live in set. 337 void removeLiveIn(MCPhysReg Reg, 338 LaneBitmask LaneMask = LaneBitmask::getAll()); 339 340 /// Return true if the specified register is in the live in set. 341 bool isLiveIn(MCPhysReg Reg, 342 LaneBitmask LaneMask = LaneBitmask::getAll()) const; 343 344 // Iteration support for live in sets. These sets are kept in sorted 345 // order by their register number. 346 using livein_iterator = LiveInVector::const_iterator; 347#ifndef NDEBUG 348 /// Unlike livein_begin, this method does not check that the liveness 349 /// information is accurate. Still for debug purposes it may be useful 350 /// to have iterators that won't assert if the liveness information 351 /// is not current. 352 livein_iterator livein_begin_dbg() const { return LiveIns.begin(); } 353 iterator_range<livein_iterator> liveins_dbg() const { 354 return make_range(livein_begin_dbg(), livein_end()); 355 } 356#endif 357 livein_iterator livein_begin() const; 358 livein_iterator livein_end() const { return LiveIns.end(); } 359 bool livein_empty() const { return LiveIns.empty(); } 360 iterator_range<livein_iterator> liveins() const { 361 return make_range(livein_begin(), livein_end()); 362 } 363 364 /// Remove entry from the livein set and return iterator to the next. 365 livein_iterator removeLiveIn(livein_iterator I); 366 367 /// Get the clobber mask for the start of this basic block. Funclets use this 368 /// to prevent register allocation across funclet transitions. 369 const uint32_t *getBeginClobberMask(const TargetRegisterInfo *TRI) const; 370 371 /// Get the clobber mask for the end of the basic block. 372 /// \see getBeginClobberMask() 373 const uint32_t *getEndClobberMask(const TargetRegisterInfo *TRI) const; 374 375 /// Return alignment of the basic block. The alignment is specified as 376 /// log2(bytes). 377 unsigned getAlignment() const { return Alignment; } 378 379 /// Set alignment of the basic block. The alignment is specified as 380 /// log2(bytes). 381 void setAlignment(unsigned Align) { Alignment = Align; } 382 383 /// Returns true if the block is a landing pad. That is this basic block is 384 /// entered via an exception handler. 385 bool isEHPad() const { return IsEHPad; } 386 387 /// Indicates the block is a landing pad. That is this basic block is entered 388 /// via an exception handler. 389 void setIsEHPad(bool V = true) { IsEHPad = V; } 390 391 bool hasEHPadSuccessor() const; 392 393 /// Returns true if this is the entry block of an EH scope, i.e., the block 394 /// that used to have a catchpad or cleanuppad instruction in the LLVM IR. 395 bool isEHScopeEntry() const { return IsEHScopeEntry; } 396 397 /// Indicates if this is the entry block of an EH scope, i.e., the block that 398 /// that used to have a catchpad or cleanuppad instruction in the LLVM IR. 399 void setIsEHScopeEntry(bool V = true) { IsEHScopeEntry = V; } 400 401 /// Returns true if this is the entry block of an EH funclet. 402 bool isEHFuncletEntry() const { return IsEHFuncletEntry; } 403 404 /// Indicates if this is the entry block of an EH funclet. 405 void setIsEHFuncletEntry(bool V = true) { IsEHFuncletEntry = V; } 406 407 /// Returns true if this is the entry block of a cleanup funclet. 408 bool isCleanupFuncletEntry() const { return IsCleanupFuncletEntry; } 409 410 /// Indicates if this is the entry block of a cleanup funclet. 411 void setIsCleanupFuncletEntry(bool V = true) { IsCleanupFuncletEntry = V; } 412 413 /// Returns true if it is legal to hoist instructions into this block. 414 bool isLegalToHoistInto() const; 415 416 // Code Layout methods. 417 418 /// Move 'this' block before or after the specified block. This only moves 419 /// the block, it does not modify the CFG or adjust potential fall-throughs at 420 /// the end of the block. 421 void moveBefore(MachineBasicBlock *NewAfter); 422 void moveAfter(MachineBasicBlock *NewBefore); 423 424 /// Update the terminator instructions in block to account for changes to the 425 /// layout. If the block previously used a fallthrough, it may now need a 426 /// branch, and if it previously used branching it may now be able to use a 427 /// fallthrough. 428 void updateTerminator(); 429 430 // Machine-CFG mutators 431 432 /// Add Succ as a successor of this MachineBasicBlock. The Predecessors list 433 /// of Succ is automatically updated. PROB parameter is stored in 434 /// Probabilities list. The default probability is set as unknown. Mixing 435 /// known and unknown probabilities in successor list is not allowed. When all 436 /// successors have unknown probabilities, 1 / N is returned as the 437 /// probability for each successor, where N is the number of successors. 438 /// 439 /// Note that duplicate Machine CFG edges are not allowed. 440 void addSuccessor(MachineBasicBlock *Succ, 441 BranchProbability Prob = BranchProbability::getUnknown()); 442 443 /// Add Succ as a successor of this MachineBasicBlock. The Predecessors list 444 /// of Succ is automatically updated. The probability is not provided because 445 /// BPI is not available (e.g. -O0 is used), in which case edge probabilities 446 /// won't be used. Using this interface can save some space. 447 void addSuccessorWithoutProb(MachineBasicBlock *Succ); 448 449 /// Set successor probability of a given iterator. 450 void setSuccProbability(succ_iterator I, BranchProbability Prob); 451 452 /// Normalize probabilities of all successors so that the sum of them becomes 453 /// one. This is usually done when the current update on this MBB is done, and 454 /// the sum of its successors' probabilities is not guaranteed to be one. The 455 /// user is responsible for the correct use of this function. 456 /// MBB::removeSuccessor() has an option to do this automatically. 457 void normalizeSuccProbs() { 458 BranchProbability::normalizeProbabilities(Probs.begin(), Probs.end()); 459 } 460 461 /// Validate successors' probabilities and check if the sum of them is 462 /// approximate one. This only works in DEBUG mode. 463 void validateSuccProbs() const; 464 465 /// Remove successor from the successors list of this MachineBasicBlock. The 466 /// Predecessors list of Succ is automatically updated. 467 /// If NormalizeSuccProbs is true, then normalize successors' probabilities 468 /// after the successor is removed. 469 void removeSuccessor(MachineBasicBlock *Succ, 470 bool NormalizeSuccProbs = false); 471 472 /// Remove specified successor from the successors list of this 473 /// MachineBasicBlock. The Predecessors list of Succ is automatically updated. 474 /// If NormalizeSuccProbs is true, then normalize successors' probabilities 475 /// after the successor is removed. 476 /// Return the iterator to the element after the one removed. 477 succ_iterator removeSuccessor(succ_iterator I, 478 bool NormalizeSuccProbs = false); 479 480 /// Replace successor OLD with NEW and update probability info. 481 void replaceSuccessor(MachineBasicBlock *Old, MachineBasicBlock *New); 482 483 /// Copy a successor (and any probability info) from original block to this 484 /// block's. Uses an iterator into the original blocks successors. 485 /// 486 /// This is useful when doing a partial clone of successors. Afterward, the 487 /// probabilities may need to be normalized. 488 void copySuccessor(MachineBasicBlock *Orig, succ_iterator I); 489 490 /// Split the old successor into old plus new and updates the probability 491 /// info. 492 void splitSuccessor(MachineBasicBlock *Old, MachineBasicBlock *New, 493 bool NormalizeSuccProbs = false); 494 495 /// Transfers all the successors from MBB to this machine basic block (i.e., 496 /// copies all the successors FromMBB and remove all the successors from 497 /// FromMBB). 498 void transferSuccessors(MachineBasicBlock *FromMBB); 499 500 /// Transfers all the successors, as in transferSuccessors, and update PHI 501 /// operands in the successor blocks which refer to FromMBB to refer to this. 502 void transferSuccessorsAndUpdatePHIs(MachineBasicBlock *FromMBB); 503 504 /// Return true if any of the successors have probabilities attached to them. 505 bool hasSuccessorProbabilities() const { return !Probs.empty(); } 506 507 /// Return true if the specified MBB is a predecessor of this block. 508 bool isPredecessor(const MachineBasicBlock *MBB) const; 509 510 /// Return true if the specified MBB is a successor of this block. 511 bool isSuccessor(const MachineBasicBlock *MBB) const; 512 513 /// Return true if the specified MBB will be emitted immediately after this 514 /// block, such that if this block exits by falling through, control will 515 /// transfer to the specified MBB. Note that MBB need not be a successor at 516 /// all, for example if this block ends with an unconditional branch to some 517 /// other block. 518 bool isLayoutSuccessor(const MachineBasicBlock *MBB) const; 519 520 /// Return the fallthrough block if the block can implicitly 521 /// transfer control to the block after it by falling off the end of 522 /// it. This should return null if it can reach the block after 523 /// it, but it uses an explicit branch to do so (e.g., a table 524 /// jump). Non-null return is a conservative answer. 525 MachineBasicBlock *getFallThrough(); 526 527 /// Return true if the block can implicitly transfer control to the 528 /// block after it by falling off the end of it. This should return 529 /// false if it can reach the block after it, but it uses an 530 /// explicit branch to do so (e.g., a table jump). True is a 531 /// conservative answer. 532 bool canFallThrough(); 533 534 /// Returns a pointer to the first instruction in this block that is not a 535 /// PHINode instruction. When adding instructions to the beginning of the 536 /// basic block, they should be added before the returned value, not before 537 /// the first instruction, which might be PHI. 538 /// Returns end() is there's no non-PHI instruction. 539 iterator getFirstNonPHI(); 540 541 /// Return the first instruction in MBB after I that is not a PHI or a label. 542 /// This is the correct point to insert lowered copies at the beginning of a 543 /// basic block that must be before any debugging information. 544 iterator SkipPHIsAndLabels(iterator I); 545 546 /// Return the first instruction in MBB after I that is not a PHI, label or 547 /// debug. This is the correct point to insert copies at the beginning of a 548 /// basic block. 549 iterator SkipPHIsLabelsAndDebug(iterator I); 550 551 /// Returns an iterator to the first terminator instruction of this basic 552 /// block. If a terminator does not exist, it returns end(). 553 iterator getFirstTerminator(); 554 const_iterator getFirstTerminator() const { 555 return const_cast<MachineBasicBlock *>(this)->getFirstTerminator(); 556 } 557 558 /// Same getFirstTerminator but it ignores bundles and return an 559 /// instr_iterator instead. 560 instr_iterator getFirstInstrTerminator(); 561 562 /// Returns an iterator to the first non-debug instruction in the basic block, 563 /// or end(). 564 iterator getFirstNonDebugInstr(); 565 const_iterator getFirstNonDebugInstr() const { 566 return const_cast<MachineBasicBlock *>(this)->getFirstNonDebugInstr(); 567 } 568 569 /// Returns an iterator to the last non-debug instruction in the basic block, 570 /// or end(). 571 iterator getLastNonDebugInstr(); 572 const_iterator getLastNonDebugInstr() const { 573 return const_cast<MachineBasicBlock *>(this)->getLastNonDebugInstr(); 574 } 575 576 /// Convenience function that returns true if the block ends in a return 577 /// instruction. 578 bool isReturnBlock() const { 579 return !empty() && back().isReturn(); 580 } 581 582 /// Convenience function that returns true if the bock ends in a EH scope 583 /// return instruction. 584 bool isEHScopeReturnBlock() const { 585 return !empty() && back().isEHScopeReturn(); 586 } 587 588 /// Split the critical edge from this block to the given successor block, and 589 /// return the newly created block, or null if splitting is not possible. 590 /// 591 /// This function updates LiveVariables, MachineDominatorTree, and 592 /// MachineLoopInfo, as applicable. 593 MachineBasicBlock *SplitCriticalEdge(MachineBasicBlock *Succ, Pass &P); 594 595 /// Check if the edge between this block and the given successor \p 596 /// Succ, can be split. If this returns true a subsequent call to 597 /// SplitCriticalEdge is guaranteed to return a valid basic block if 598 /// no changes occurred in the meantime. 599 bool canSplitCriticalEdge(const MachineBasicBlock *Succ) const; 600 601 void pop_front() { Insts.pop_front(); } 602 void pop_back() { Insts.pop_back(); } 603 void push_back(MachineInstr *MI) { Insts.push_back(MI); } 604 605 /// Insert MI into the instruction list before I, possibly inside a bundle. 606 /// 607 /// If the insertion point is inside a bundle, MI will be added to the bundle, 608 /// otherwise MI will not be added to any bundle. That means this function 609 /// alone can't be used to prepend or append instructions to bundles. See 610 /// MIBundleBuilder::insert() for a more reliable way of doing that. 611 instr_iterator insert(instr_iterator I, MachineInstr *M); 612 613 /// Insert a range of instructions into the instruction list before I. 614 template<typename IT> 615 void insert(iterator I, IT S, IT E) { 616 assert((I == end() || I->getParent() == this) && 617 "iterator points outside of basic block"); 618 Insts.insert(I.getInstrIterator(), S, E); 619 } 620 621 /// Insert MI into the instruction list before I. 622 iterator insert(iterator I, MachineInstr *MI) { 623 assert((I == end() || I->getParent() == this) && 624 "iterator points outside of basic block"); 625 assert(!MI->isBundledWithPred() && !MI->isBundledWithSucc() && 626 "Cannot insert instruction with bundle flags"); 627 return Insts.insert(I.getInstrIterator(), MI); 628 } 629 630 /// Insert MI into the instruction list after I. 631 iterator insertAfter(iterator I, MachineInstr *MI) { 632 assert((I == end() || I->getParent() == this) && 633 "iterator points outside of basic block"); 634 assert(!MI->isBundledWithPred() && !MI->isBundledWithSucc() && 635 "Cannot insert instruction with bundle flags"); 636 return Insts.insertAfter(I.getInstrIterator(), MI); 637 } 638 639 /// Remove an instruction from the instruction list and delete it. 640 /// 641 /// If the instruction is part of a bundle, the other instructions in the 642 /// bundle will still be bundled after removing the single instruction. 643 instr_iterator erase(instr_iterator I); 644 645 /// Remove an instruction from the instruction list and delete it. 646 /// 647 /// If the instruction is part of a bundle, the other instructions in the 648 /// bundle will still be bundled after removing the single instruction. 649 instr_iterator erase_instr(MachineInstr *I) { 650 return erase(instr_iterator(I)); 651 } 652 653 /// Remove a range of instructions from the instruction list and delete them. 654 iterator erase(iterator I, iterator E) { 655 return Insts.erase(I.getInstrIterator(), E.getInstrIterator()); 656 } 657 658 /// Remove an instruction or bundle from the instruction list and delete it. 659 /// 660 /// If I points to a bundle of instructions, they are all erased. 661 iterator erase(iterator I) { 662 return erase(I, std::next(I)); 663 } 664 665 /// Remove an instruction from the instruction list and delete it. 666 /// 667 /// If I is the head of a bundle of instructions, the whole bundle will be 668 /// erased. 669 iterator erase(MachineInstr *I) { 670 return erase(iterator(I)); 671 } 672 673 /// Remove the unbundled instruction from the instruction list without 674 /// deleting it. 675 /// 676 /// This function can not be used to remove bundled instructions, use 677 /// remove_instr to remove individual instructions from a bundle. 678 MachineInstr *remove(MachineInstr *I) { 679 assert(!I->isBundled() && "Cannot remove bundled instructions"); 680 return Insts.remove(instr_iterator(I)); 681 } 682 683 /// Remove the possibly bundled instruction from the instruction list 684 /// without deleting it. 685 /// 686 /// If the instruction is part of a bundle, the other instructions in the 687 /// bundle will still be bundled after removing the single instruction. 688 MachineInstr *remove_instr(MachineInstr *I); 689 690 void clear() { 691 Insts.clear(); 692 } 693 694 /// Take an instruction from MBB 'Other' at the position From, and insert it 695 /// into this MBB right before 'Where'. 696 /// 697 /// If From points to a bundle of instructions, the whole bundle is moved. 698 void splice(iterator Where, MachineBasicBlock *Other, iterator From) { 699 // The range splice() doesn't allow noop moves, but this one does. 700 if (Where != From) 701 splice(Where, Other, From, std::next(From)); 702 } 703 704 /// Take a block of instructions from MBB 'Other' in the range [From, To), 705 /// and insert them into this MBB right before 'Where'. 706 /// 707 /// The instruction at 'Where' must not be included in the range of 708 /// instructions to move. 709 void splice(iterator Where, MachineBasicBlock *Other, 710 iterator From, iterator To) { 711 Insts.splice(Where.getInstrIterator(), Other->Insts, 712 From.getInstrIterator(), To.getInstrIterator()); 713 } 714 715 /// This method unlinks 'this' from the containing function, and returns it, 716 /// but does not delete it. 717 MachineBasicBlock *removeFromParent(); 718 719 /// This method unlinks 'this' from the containing function and deletes it. 720 void eraseFromParent(); 721 722 /// Given a machine basic block that branched to 'Old', change the code and 723 /// CFG so that it branches to 'New' instead. 724 void ReplaceUsesOfBlockWith(MachineBasicBlock *Old, MachineBasicBlock *New); 725 726 /// Various pieces of code can cause excess edges in the CFG to be inserted. 727 /// If we have proven that MBB can only branch to DestA and DestB, remove any 728 /// other MBB successors from the CFG. DestA and DestB can be null. Besides 729 /// DestA and DestB, retain other edges leading to LandingPads (currently 730 /// there can be only one; we don't check or require that here). Note it is 731 /// possible that DestA and/or DestB are LandingPads. 732 bool CorrectExtraCFGEdges(MachineBasicBlock *DestA, 733 MachineBasicBlock *DestB, 734 bool IsCond); 735 736 /// Find the next valid DebugLoc starting at MBBI, skipping any DBG_VALUE 737 /// and DBG_LABEL instructions. Return UnknownLoc if there is none. 738 DebugLoc findDebugLoc(instr_iterator MBBI); 739 DebugLoc findDebugLoc(iterator MBBI) { 740 return findDebugLoc(MBBI.getInstrIterator()); 741 } 742 743 /// Find the previous valid DebugLoc preceding MBBI, skipping and DBG_VALUE 744 /// instructions. Return UnknownLoc if there is none. 745 DebugLoc findPrevDebugLoc(instr_iterator MBBI); 746 DebugLoc findPrevDebugLoc(iterator MBBI) { 747 return findPrevDebugLoc(MBBI.getInstrIterator()); 748 } 749 750 /// Find and return the merged DebugLoc of the branch instructions of the 751 /// block. Return UnknownLoc if there is none. 752 DebugLoc findBranchDebugLoc(); 753 754 /// Possible outcome of a register liveness query to computeRegisterLiveness() 755 enum LivenessQueryResult { 756 LQR_Live, ///< Register is known to be (at least partially) live. 757 LQR_Dead, ///< Register is known to be fully dead. 758 LQR_Unknown ///< Register liveness not decidable from local neighborhood. 759 }; 760 761 /// Return whether (physical) register \p Reg has been defined and not 762 /// killed as of just before \p Before. 763 /// 764 /// Search is localised to a neighborhood of \p Neighborhood instructions 765 /// before (searching for defs or kills) and \p Neighborhood instructions 766 /// after (searching just for defs) \p Before. 767 /// 768 /// \p Reg must be a physical register. 769 LivenessQueryResult computeRegisterLiveness(const TargetRegisterInfo *TRI, 770 unsigned Reg, 771 const_iterator Before, 772 unsigned Neighborhood = 10) const; 773 774 // Debugging methods. 775 void dump() const; 776 void print(raw_ostream &OS, const SlotIndexes * = nullptr, 777 bool IsStandalone = true) const; 778 void print(raw_ostream &OS, ModuleSlotTracker &MST, 779 const SlotIndexes * = nullptr, bool IsStandalone = true) const; 780 781 // Printing method used by LoopInfo. 782 void printAsOperand(raw_ostream &OS, bool PrintType = true) const; 783 784 /// MachineBasicBlocks are uniquely numbered at the function level, unless 785 /// they're not in a MachineFunction yet, in which case this will return -1. 786 int getNumber() const { return Number; } 787 void setNumber(int N) { Number = N; } 788 789 /// Return the MCSymbol for this basic block. 790 MCSymbol *getSymbol() const; 791 792 Optional<uint64_t> getIrrLoopHeaderWeight() const { 793 return IrrLoopHeaderWeight; 794 } 795 796 void setIrrLoopHeaderWeight(uint64_t Weight) { 797 IrrLoopHeaderWeight = Weight; 798 } 799 800private: 801 /// Return probability iterator corresponding to the I successor iterator. 802 probability_iterator getProbabilityIterator(succ_iterator I); 803 const_probability_iterator 804 getProbabilityIterator(const_succ_iterator I) const; 805 806 friend class MachineBranchProbabilityInfo; 807 friend class MIPrinter; 808 809 /// Return probability of the edge from this block to MBB. This method should 810 /// NOT be called directly, but by using getEdgeProbability method from 811 /// MachineBranchProbabilityInfo class. 812 BranchProbability getSuccProbability(const_succ_iterator Succ) const; 813 814 // Methods used to maintain doubly linked list of blocks... 815 friend struct ilist_callback_traits<MachineBasicBlock>; 816 817 // Machine-CFG mutators 818 819 /// Add Pred as a predecessor of this MachineBasicBlock. Don't do this 820 /// unless you know what you're doing, because it doesn't update Pred's 821 /// successors list. Use Pred->addSuccessor instead. 822 void addPredecessor(MachineBasicBlock *Pred); 823 824 /// Remove Pred as a predecessor of this MachineBasicBlock. Don't do this 825 /// unless you know what you're doing, because it doesn't update Pred's 826 /// successors list. Use Pred->removeSuccessor instead. 827 void removePredecessor(MachineBasicBlock *Pred); 828}; 829 830raw_ostream& operator<<(raw_ostream &OS, const MachineBasicBlock &MBB); 831 832/// Prints a machine basic block reference. 833/// 834/// The format is: 835/// %bb.5 - a machine basic block with MBB.getNumber() == 5. 836/// 837/// Usage: OS << printMBBReference(MBB) << '\n'; 838Printable printMBBReference(const MachineBasicBlock &MBB); 839 840// This is useful when building IndexedMaps keyed on basic block pointers. 841struct MBB2NumberFunctor { 842 using argument_type = const MachineBasicBlock *; 843 unsigned operator()(const MachineBasicBlock *MBB) const { 844 return MBB->getNumber(); 845 } 846}; 847 848//===--------------------------------------------------------------------===// 849// GraphTraits specializations for machine basic block graphs (machine-CFGs) 850//===--------------------------------------------------------------------===// 851 852// Provide specializations of GraphTraits to be able to treat a 853// MachineFunction as a graph of MachineBasicBlocks. 854// 855 856template <> struct GraphTraits<MachineBasicBlock *> { 857 using NodeRef = MachineBasicBlock *; 858 using ChildIteratorType = MachineBasicBlock::succ_iterator; 859 860 static NodeRef getEntryNode(MachineBasicBlock *BB) { return BB; } 861 static ChildIteratorType child_begin(NodeRef N) { return N->succ_begin(); } 862 static ChildIteratorType child_end(NodeRef N) { return N->succ_end(); } 863}; 864 865template <> struct GraphTraits<const MachineBasicBlock *> { 866 using NodeRef = const MachineBasicBlock *; 867 using ChildIteratorType = MachineBasicBlock::const_succ_iterator; 868 869 static NodeRef getEntryNode(const MachineBasicBlock *BB) { return BB; } 870 static ChildIteratorType child_begin(NodeRef N) { return N->succ_begin(); } 871 static ChildIteratorType child_end(NodeRef N) { return N->succ_end(); } 872}; 873 874// Provide specializations of GraphTraits to be able to treat a 875// MachineFunction as a graph of MachineBasicBlocks and to walk it 876// in inverse order. Inverse order for a function is considered 877// to be when traversing the predecessor edges of a MBB 878// instead of the successor edges. 879// 880template <> struct GraphTraits<Inverse<MachineBasicBlock*>> { 881 using NodeRef = MachineBasicBlock *; 882 using ChildIteratorType = MachineBasicBlock::pred_iterator; 883 884 static NodeRef getEntryNode(Inverse<MachineBasicBlock *> G) { 885 return G.Graph; 886 } 887 888 static ChildIteratorType child_begin(NodeRef N) { return N->pred_begin(); } 889 static ChildIteratorType child_end(NodeRef N) { return N->pred_end(); } 890}; 891 892template <> struct GraphTraits<Inverse<const MachineBasicBlock*>> { 893 using NodeRef = const MachineBasicBlock *; 894 using ChildIteratorType = MachineBasicBlock::const_pred_iterator; 895 896 static NodeRef getEntryNode(Inverse<const MachineBasicBlock *> G) { 897 return G.Graph; 898 } 899 900 static ChildIteratorType child_begin(NodeRef N) { return N->pred_begin(); } 901 static ChildIteratorType child_end(NodeRef N) { return N->pred_end(); } 902}; 903 904/// MachineInstrSpan provides an interface to get an iteration range 905/// containing the instruction it was initialized with, along with all 906/// those instructions inserted prior to or following that instruction 907/// at some point after the MachineInstrSpan is constructed. 908class MachineInstrSpan { 909 MachineBasicBlock &MBB; 910 MachineBasicBlock::iterator I, B, E; 911 912public: 913 MachineInstrSpan(MachineBasicBlock::iterator I, MachineBasicBlock *BB) 914 : MBB(*BB), I(I), B(I == MBB.begin() ? MBB.end() : std::prev(I)), 915 E(std::next(I)) { 916 assert(I == BB->end() || I->getParent() == BB); 917 } 918 919 MachineBasicBlock::iterator begin() { 920 return B == MBB.end() ? MBB.begin() : std::next(B); 921 } 922 MachineBasicBlock::iterator end() { return E; } 923 bool empty() { return begin() == end(); } 924 925 MachineBasicBlock::iterator getInitial() { return I; } 926}; 927 928/// Increment \p It until it points to a non-debug instruction or to \p End 929/// and return the resulting iterator. This function should only be used 930/// MachineBasicBlock::{iterator, const_iterator, instr_iterator, 931/// const_instr_iterator} and the respective reverse iterators. 932template<typename IterT> 933inline IterT skipDebugInstructionsForward(IterT It, IterT End) { 934 while (It != End && It->isDebugInstr()) 935 It++; 936 return It; 937} 938 939/// Decrement \p It until it points to a non-debug instruction or to \p Begin 940/// and return the resulting iterator. This function should only be used 941/// MachineBasicBlock::{iterator, const_iterator, instr_iterator, 942/// const_instr_iterator} and the respective reverse iterators. 943template<class IterT> 944inline IterT skipDebugInstructionsBackward(IterT It, IterT Begin) { 945 while (It != Begin && It->isDebugInstr()) 946 It--; 947 return It; 948} 949 950} // end namespace llvm 951 952#endif // LLVM_CODEGEN_MACHINEBASICBLOCK_H 953