MachineBasicBlock.cpp revision 7707a0df5b00c8326a581205639d6b2871f182e9
1//===-- llvm/CodeGen/MachineBasicBlock.cpp ----------------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// Collect the sequence of machine instructions for a basic block. 11// 12//===----------------------------------------------------------------------===// 13 14#include "llvm/CodeGen/MachineBasicBlock.h" 15#include "llvm/BasicBlock.h" 16#include "llvm/CodeGen/MachineFunction.h" 17#include "llvm/Target/TargetRegisterInfo.h" 18#include "llvm/Target/TargetData.h" 19#include "llvm/Target/TargetInstrDesc.h" 20#include "llvm/Target/TargetInstrInfo.h" 21#include "llvm/Target/TargetMachine.h" 22#include "llvm/Support/LeakDetector.h" 23#include "llvm/Support/raw_ostream.h" 24#include "llvm/Assembly/Writer.h" 25#include <algorithm> 26using namespace llvm; 27 28MachineBasicBlock::MachineBasicBlock(MachineFunction &mf, const BasicBlock *bb) 29 : BB(bb), Number(-1), xParent(&mf), Alignment(0), IsLandingPad(false), 30 AddressTaken(false) { 31 Insts.Parent = this; 32} 33 34MachineBasicBlock::~MachineBasicBlock() { 35 LeakDetector::removeGarbageObject(this); 36} 37 38raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineBasicBlock &MBB) { 39 MBB.print(OS); 40 return OS; 41} 42 43/// addNodeToList (MBB) - When an MBB is added to an MF, we need to update the 44/// parent pointer of the MBB, the MBB numbering, and any instructions in the 45/// MBB to be on the right operand list for registers. 46/// 47/// MBBs start out as #-1. When a MBB is added to a MachineFunction, it 48/// gets the next available unique MBB number. If it is removed from a 49/// MachineFunction, it goes back to being #-1. 50void ilist_traits<MachineBasicBlock>::addNodeToList(MachineBasicBlock *N) { 51 MachineFunction &MF = *N->getParent(); 52 N->Number = MF.addToMBBNumbering(N); 53 54 // Make sure the instructions have their operands in the reginfo lists. 55 MachineRegisterInfo &RegInfo = MF.getRegInfo(); 56 for (MachineBasicBlock::iterator I = N->begin(), E = N->end(); I != E; ++I) 57 I->AddRegOperandsToUseLists(RegInfo); 58 59 LeakDetector::removeGarbageObject(N); 60} 61 62void ilist_traits<MachineBasicBlock>::removeNodeFromList(MachineBasicBlock *N) { 63 N->getParent()->removeFromMBBNumbering(N->Number); 64 N->Number = -1; 65 LeakDetector::addGarbageObject(N); 66} 67 68 69/// addNodeToList (MI) - When we add an instruction to a basic block 70/// list, we update its parent pointer and add its operands from reg use/def 71/// lists if appropriate. 72void ilist_traits<MachineInstr>::addNodeToList(MachineInstr *N) { 73 assert(N->getParent() == 0 && "machine instruction already in a basic block"); 74 N->setParent(Parent); 75 76 // Add the instruction's register operands to their corresponding 77 // use/def lists. 78 MachineFunction *MF = Parent->getParent(); 79 N->AddRegOperandsToUseLists(MF->getRegInfo()); 80 81 LeakDetector::removeGarbageObject(N); 82} 83 84/// removeNodeFromList (MI) - When we remove an instruction from a basic block 85/// list, we update its parent pointer and remove its operands from reg use/def 86/// lists if appropriate. 87void ilist_traits<MachineInstr>::removeNodeFromList(MachineInstr *N) { 88 assert(N->getParent() != 0 && "machine instruction not in a basic block"); 89 90 // Remove from the use/def lists. 91 N->RemoveRegOperandsFromUseLists(); 92 93 N->setParent(0); 94 95 LeakDetector::addGarbageObject(N); 96} 97 98/// transferNodesFromList (MI) - When moving a range of instructions from one 99/// MBB list to another, we need to update the parent pointers and the use/def 100/// lists. 101void ilist_traits<MachineInstr>:: 102transferNodesFromList(ilist_traits<MachineInstr> &fromList, 103 MachineBasicBlock::iterator first, 104 MachineBasicBlock::iterator last) { 105 assert(Parent->getParent() == fromList.Parent->getParent() && 106 "MachineInstr parent mismatch!"); 107 108 // Splice within the same MBB -> no change. 109 if (Parent == fromList.Parent) return; 110 111 // If splicing between two blocks within the same function, just update the 112 // parent pointers. 113 for (; first != last; ++first) 114 first->setParent(Parent); 115} 116 117void ilist_traits<MachineInstr>::deleteNode(MachineInstr* MI) { 118 assert(!MI->getParent() && "MI is still in a block!"); 119 Parent->getParent()->DeleteMachineInstr(MI); 120} 121 122MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() { 123 iterator I = end(); 124 while (I != begin() && (--I)->getDesc().isTerminator()) 125 ; /*noop */ 126 if (I != end() && !I->getDesc().isTerminator()) ++I; 127 return I; 128} 129 130/// isOnlyReachableViaFallthough - Return true if this basic block has 131/// exactly one predecessor and the control transfer mechanism between 132/// the predecessor and this block is a fall-through. 133bool MachineBasicBlock::isOnlyReachableByFallthrough() const { 134 // If this is a landing pad, it isn't a fall through. If it has no preds, 135 // then nothing falls through to it. 136 if (isLandingPad() || pred_empty()) 137 return false; 138 139 // If there isn't exactly one predecessor, it can't be a fall through. 140 const_pred_iterator PI = pred_begin(), PI2 = PI; 141 ++PI2; 142 if (PI2 != pred_end()) 143 return false; 144 145 // The predecessor has to be immediately before this block. 146 const MachineBasicBlock *Pred = *PI; 147 148 if (!Pred->isLayoutSuccessor(this)) 149 return false; 150 151 // If the block is completely empty, then it definitely does fall through. 152 if (Pred->empty()) 153 return true; 154 155 // Otherwise, check the last instruction. 156 const MachineInstr &LastInst = Pred->back(); 157 return !LastInst.getDesc().isBarrier(); 158} 159 160void MachineBasicBlock::dump() const { 161 print(errs()); 162} 163 164static inline void OutputReg(raw_ostream &os, unsigned RegNo, 165 const TargetRegisterInfo *TRI = 0) { 166 if (RegNo != 0 && TargetRegisterInfo::isPhysicalRegister(RegNo)) { 167 if (TRI) 168 os << " %" << TRI->get(RegNo).Name; 169 else 170 os << " %physreg" << RegNo; 171 } else 172 os << " %reg" << RegNo; 173} 174 175void MachineBasicBlock::print(raw_ostream &OS) const { 176 const MachineFunction *MF = getParent(); 177 if (!MF) { 178 OS << "Can't print out MachineBasicBlock because parent MachineFunction" 179 << " is null\n"; 180 return; 181 } 182 183 if (Alignment) { OS << "Alignment " << Alignment << "\n"; } 184 185 OS << "BB#" << getNumber() << ": "; 186 187 const char *Comma = ""; 188 if (const BasicBlock *LBB = getBasicBlock()) { 189 OS << Comma << "derived from LLVM BB "; 190 WriteAsOperand(OS, LBB, /*PrintType=*/false); 191 Comma = ", "; 192 } 193 if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; } 194 if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; } 195 OS << '\n'; 196 197 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo(); 198 if (!livein_empty()) { 199 OS << " Live Ins:"; 200 for (const_livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I) 201 OutputReg(OS, *I, TRI); 202 OS << '\n'; 203 } 204 // Print the preds of this block according to the CFG. 205 if (!pred_empty()) { 206 OS << " Predecessors according to CFG:"; 207 for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI) 208 OS << " BB#" << (*PI)->getNumber(); 209 OS << '\n'; 210 } 211 212 for (const_iterator I = begin(); I != end(); ++I) { 213 OS << '\t'; 214 I->print(OS, &getParent()->getTarget()); 215 } 216 217 // Print the successors of this block according to the CFG. 218 if (!succ_empty()) { 219 OS << " Successors according to CFG:"; 220 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI) 221 OS << " BB#" << (*SI)->getNumber(); 222 OS << '\n'; 223 } 224} 225 226void MachineBasicBlock::removeLiveIn(unsigned Reg) { 227 livein_iterator I = std::find(livein_begin(), livein_end(), Reg); 228 assert(I != livein_end() && "Not a live in!"); 229 LiveIns.erase(I); 230} 231 232bool MachineBasicBlock::isLiveIn(unsigned Reg) const { 233 const_livein_iterator I = std::find(livein_begin(), livein_end(), Reg); 234 return I != livein_end(); 235} 236 237void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) { 238 getParent()->splice(NewAfter, this); 239} 240 241void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) { 242 MachineFunction::iterator BBI = NewBefore; 243 getParent()->splice(++BBI, this); 244} 245 246void MachineBasicBlock::updateTerminator() { 247 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); 248 // A block with no successors has no concerns with fall-through edges. 249 if (this->succ_empty()) return; 250 251 MachineBasicBlock *TBB = 0, *FBB = 0; 252 SmallVector<MachineOperand, 4> Cond; 253 bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond); 254 (void) B; 255 assert(!B && "UpdateTerminators requires analyzable predecessors!"); 256 if (Cond.empty()) { 257 if (TBB) { 258 // The block has an unconditional branch. If its successor is now 259 // its layout successor, delete the branch. 260 if (isLayoutSuccessor(TBB)) 261 TII->RemoveBranch(*this); 262 } else { 263 // The block has an unconditional fallthrough. If its successor is not 264 // its layout successor, insert a branch. 265 TBB = *succ_begin(); 266 if (!isLayoutSuccessor(TBB)) 267 TII->InsertBranch(*this, TBB, 0, Cond); 268 } 269 } else { 270 if (FBB) { 271 // The block has a non-fallthrough conditional branch. If one of its 272 // successors is its layout successor, rewrite it to a fallthrough 273 // conditional branch. 274 if (isLayoutSuccessor(TBB)) { 275 TII->RemoveBranch(*this); 276 TII->ReverseBranchCondition(Cond); 277 TII->InsertBranch(*this, FBB, 0, Cond); 278 } else if (isLayoutSuccessor(FBB)) { 279 TII->RemoveBranch(*this); 280 TII->InsertBranch(*this, TBB, 0, Cond); 281 } 282 } else { 283 // The block has a fallthrough conditional branch. 284 MachineBasicBlock *MBBA = *succ_begin(); 285 MachineBasicBlock *MBBB = *next(succ_begin()); 286 if (MBBA == TBB) std::swap(MBBB, MBBA); 287 if (isLayoutSuccessor(TBB)) { 288 TII->RemoveBranch(*this); 289 TII->ReverseBranchCondition(Cond); 290 TII->InsertBranch(*this, MBBA, 0, Cond); 291 } else if (!isLayoutSuccessor(MBBA)) { 292 TII->RemoveBranch(*this); 293 TII->InsertBranch(*this, TBB, MBBA, Cond); 294 } 295 } 296 } 297} 298 299void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ) { 300 Successors.push_back(succ); 301 succ->addPredecessor(this); 302} 303 304void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) { 305 succ->removePredecessor(this); 306 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ); 307 assert(I != Successors.end() && "Not a current successor!"); 308 Successors.erase(I); 309} 310 311MachineBasicBlock::succ_iterator 312MachineBasicBlock::removeSuccessor(succ_iterator I) { 313 assert(I != Successors.end() && "Not a current successor!"); 314 (*I)->removePredecessor(this); 315 return Successors.erase(I); 316} 317 318void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) { 319 Predecessors.push_back(pred); 320} 321 322void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) { 323 std::vector<MachineBasicBlock *>::iterator I = 324 std::find(Predecessors.begin(), Predecessors.end(), pred); 325 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!"); 326 Predecessors.erase(I); 327} 328 329void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) { 330 if (this == fromMBB) 331 return; 332 333 for (MachineBasicBlock::succ_iterator I = fromMBB->succ_begin(), 334 E = fromMBB->succ_end(); I != E; ++I) 335 addSuccessor(*I); 336 337 while (!fromMBB->succ_empty()) 338 fromMBB->removeSuccessor(fromMBB->succ_begin()); 339} 340 341bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const { 342 std::vector<MachineBasicBlock *>::const_iterator I = 343 std::find(Successors.begin(), Successors.end(), MBB); 344 return I != Successors.end(); 345} 346 347bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const { 348 MachineFunction::const_iterator I(this); 349 return next(I) == MachineFunction::const_iterator(MBB); 350} 351 352/// removeFromParent - This method unlinks 'this' from the containing function, 353/// and returns it, but does not delete it. 354MachineBasicBlock *MachineBasicBlock::removeFromParent() { 355 assert(getParent() && "Not embedded in a function!"); 356 getParent()->remove(this); 357 return this; 358} 359 360 361/// eraseFromParent - This method unlinks 'this' from the containing function, 362/// and deletes it. 363void MachineBasicBlock::eraseFromParent() { 364 assert(getParent() && "Not embedded in a function!"); 365 getParent()->erase(this); 366} 367 368 369/// ReplaceUsesOfBlockWith - Given a machine basic block that branched to 370/// 'Old', change the code and CFG so that it branches to 'New' instead. 371void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old, 372 MachineBasicBlock *New) { 373 assert(Old != New && "Cannot replace self with self!"); 374 375 MachineBasicBlock::iterator I = end(); 376 while (I != begin()) { 377 --I; 378 if (!I->getDesc().isTerminator()) break; 379 380 // Scan the operands of this machine instruction, replacing any uses of Old 381 // with New. 382 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 383 if (I->getOperand(i).isMBB() && 384 I->getOperand(i).getMBB() == Old) 385 I->getOperand(i).setMBB(New); 386 } 387 388 // Update the successor information. 389 removeSuccessor(Old); 390 addSuccessor(New); 391} 392 393/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the 394/// CFG to be inserted. If we have proven that MBB can only branch to DestA and 395/// DestB, remove any other MBB successors from the CFG. DestA and DestB can 396/// be null. 397/// Besides DestA and DestB, retain other edges leading to LandingPads 398/// (currently there can be only one; we don't check or require that here). 399/// Note it is possible that DestA and/or DestB are LandingPads. 400bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA, 401 MachineBasicBlock *DestB, 402 bool isCond) { 403 bool MadeChange = false; 404 bool AddedFallThrough = false; 405 406 MachineFunction::iterator FallThru = next(MachineFunction::iterator(this)); 407 408 // If this block ends with a conditional branch that falls through to its 409 // successor, set DestB as the successor. 410 if (isCond) { 411 if (DestB == 0 && FallThru != getParent()->end()) { 412 DestB = FallThru; 413 AddedFallThrough = true; 414 } 415 } else { 416 // If this is an unconditional branch with no explicit dest, it must just be 417 // a fallthrough into DestB. 418 if (DestA == 0 && FallThru != getParent()->end()) { 419 DestA = FallThru; 420 AddedFallThrough = true; 421 } 422 } 423 424 MachineBasicBlock::succ_iterator SI = succ_begin(); 425 MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB; 426 while (SI != succ_end()) { 427 if (*SI == DestA) { 428 DestA = 0; 429 ++SI; 430 } else if (*SI == DestB) { 431 DestB = 0; 432 ++SI; 433 } else if ((*SI)->isLandingPad() && 434 *SI!=OrigDestA && *SI!=OrigDestB) { 435 ++SI; 436 } else { 437 // Otherwise, this is a superfluous edge, remove it. 438 SI = removeSuccessor(SI); 439 MadeChange = true; 440 } 441 } 442 if (!AddedFallThrough) { 443 assert(DestA == 0 && DestB == 0 && 444 "MachineCFG is missing edges!"); 445 } else if (isCond) { 446 assert(DestA == 0 && "MachineCFG is missing edges!"); 447 } 448 return MadeChange; 449} 450