MachineBasicBlock.cpp revision dfbbf6e0232315b79805f13baab06828de24e558
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/TargetMachine.h" 21#include "llvm/Support/LeakDetector.h" 22#include "llvm/Support/raw_ostream.h" 23#include <algorithm> 24using namespace llvm; 25 26MachineBasicBlock::MachineBasicBlock(MachineFunction &mf, const BasicBlock *bb) 27 : BB(bb), Number(-1), xParent(&mf), Alignment(0), IsLandingPad(false), 28 AddressTaken(false) { 29 Insts.Parent = this; 30} 31 32MachineBasicBlock::~MachineBasicBlock() { 33 LeakDetector::removeGarbageObject(this); 34} 35 36raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineBasicBlock &MBB) { 37 MBB.print(OS); 38 return OS; 39} 40 41/// addNodeToList (MBB) - When an MBB is added to an MF, we need to update the 42/// parent pointer of the MBB, the MBB numbering, and any instructions in the 43/// MBB to be on the right operand list for registers. 44/// 45/// MBBs start out as #-1. When a MBB is added to a MachineFunction, it 46/// gets the next available unique MBB number. If it is removed from a 47/// MachineFunction, it goes back to being #-1. 48void ilist_traits<MachineBasicBlock>::addNodeToList(MachineBasicBlock *N) { 49 MachineFunction &MF = *N->getParent(); 50 N->Number = MF.addToMBBNumbering(N); 51 52 // Make sure the instructions have their operands in the reginfo lists. 53 MachineRegisterInfo &RegInfo = MF.getRegInfo(); 54 for (MachineBasicBlock::iterator I = N->begin(), E = N->end(); I != E; ++I) 55 I->AddRegOperandsToUseLists(RegInfo); 56 57 LeakDetector::removeGarbageObject(N); 58} 59 60void ilist_traits<MachineBasicBlock>::removeNodeFromList(MachineBasicBlock *N) { 61 N->getParent()->removeFromMBBNumbering(N->Number); 62 N->Number = -1; 63 LeakDetector::addGarbageObject(N); 64} 65 66 67/// addNodeToList (MI) - When we add an instruction to a basic block 68/// list, we update its parent pointer and add its operands from reg use/def 69/// lists if appropriate. 70void ilist_traits<MachineInstr>::addNodeToList(MachineInstr *N) { 71 assert(N->getParent() == 0 && "machine instruction already in a basic block"); 72 N->setParent(Parent); 73 74 // Add the instruction's register operands to their corresponding 75 // use/def lists. 76 MachineFunction *MF = Parent->getParent(); 77 N->AddRegOperandsToUseLists(MF->getRegInfo()); 78 79 LeakDetector::removeGarbageObject(N); 80} 81 82/// removeNodeFromList (MI) - When we remove an instruction from a basic block 83/// list, we update its parent pointer and remove its operands from reg use/def 84/// lists if appropriate. 85void ilist_traits<MachineInstr>::removeNodeFromList(MachineInstr *N) { 86 assert(N->getParent() != 0 && "machine instruction not in a basic block"); 87 88 // Remove from the use/def lists. 89 N->RemoveRegOperandsFromUseLists(); 90 91 N->setParent(0); 92 93 LeakDetector::addGarbageObject(N); 94} 95 96/// transferNodesFromList (MI) - When moving a range of instructions from one 97/// MBB list to another, we need to update the parent pointers and the use/def 98/// lists. 99void ilist_traits<MachineInstr>:: 100transferNodesFromList(ilist_traits<MachineInstr> &fromList, 101 MachineBasicBlock::iterator first, 102 MachineBasicBlock::iterator last) { 103 assert(Parent->getParent() == fromList.Parent->getParent() && 104 "MachineInstr parent mismatch!"); 105 106 // Splice within the same MBB -> no change. 107 if (Parent == fromList.Parent) return; 108 109 // If splicing between two blocks within the same function, just update the 110 // parent pointers. 111 for (; first != last; ++first) 112 first->setParent(Parent); 113} 114 115void ilist_traits<MachineInstr>::deleteNode(MachineInstr* MI) { 116 assert(!MI->getParent() && "MI is still in a block!"); 117 Parent->getParent()->DeleteMachineInstr(MI); 118} 119 120MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() { 121 iterator I = end(); 122 while (I != begin() && (--I)->getDesc().isTerminator()) 123 ; /*noop */ 124 if (I != end() && !I->getDesc().isTerminator()) ++I; 125 return I; 126} 127 128/// isOnlyReachableViaFallthough - Return true if this basic block has 129/// exactly one predecessor and the control transfer mechanism between 130/// the predecessor and this block is a fall-through. 131bool MachineBasicBlock::isOnlyReachableByFallthrough() const { 132 // If this is a landing pad, it isn't a fall through. If it has no preds, 133 // then nothing falls through to it. 134 if (isLandingPad() || pred_empty()) 135 return false; 136 137 // If there isn't exactly one predecessor, it can't be a fall through. 138 const_pred_iterator PI = pred_begin(), PI2 = PI; 139 ++PI2; 140 if (PI2 != pred_end()) 141 return false; 142 143 // The predecessor has to be immediately before this block. 144 const MachineBasicBlock *Pred = *PI; 145 146 if (!Pred->isLayoutSuccessor(this)) 147 return false; 148 149 // If the block is completely empty, then it definitely does fall through. 150 if (Pred->empty()) 151 return true; 152 153 // Otherwise, check the last instruction. 154 const MachineInstr &LastInst = Pred->back(); 155 return !LastInst.getDesc().isBarrier(); 156} 157 158void MachineBasicBlock::dump() const { 159 print(errs()); 160} 161 162static inline void OutputReg(raw_ostream &os, unsigned RegNo, 163 const TargetRegisterInfo *TRI = 0) { 164 if (!RegNo || TargetRegisterInfo::isPhysicalRegister(RegNo)) { 165 if (TRI) 166 os << " %" << TRI->get(RegNo).Name; 167 else 168 os << " %mreg(" << RegNo << ")"; 169 } else 170 os << " %reg" << RegNo; 171} 172 173void MachineBasicBlock::print(raw_ostream &OS) const { 174 const MachineFunction *MF = getParent(); 175 if (!MF) { 176 OS << "Can't print out MachineBasicBlock because parent MachineFunction" 177 << " is null\n"; 178 return; 179 } 180 181 const BasicBlock *LBB = getBasicBlock(); 182 OS << '\n'; 183 if (LBB) OS << LBB->getName() << ": "; 184 OS << (const void*)this 185 << ", LLVM BB @" << (const void*) LBB << ", ID#" << getNumber(); 186 if (Alignment) OS << ", Alignment " << Alignment; 187 if (isLandingPad()) OS << ", EH LANDING PAD"; 188 if (hasAddressTaken()) OS << ", ADDRESS TAKEN"; 189 OS << ":\n"; 190 191 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo(); 192 if (!livein_empty()) { 193 OS << "Live Ins:"; 194 for (const_livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I) 195 OutputReg(OS, *I, TRI); 196 OS << '\n'; 197 } 198 // Print the preds of this block according to the CFG. 199 if (!pred_empty()) { 200 OS << " Predecessors according to CFG:"; 201 for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI) 202 OS << ' ' << *PI << " (#" << (*PI)->getNumber() << ')'; 203 OS << '\n'; 204 } 205 206 for (const_iterator I = begin(); I != end(); ++I) { 207 OS << '\t'; 208 I->print(OS, &getParent()->getTarget()); 209 } 210 211 // Print the successors of this block according to the CFG. 212 if (!succ_empty()) { 213 OS << " Successors according to CFG:"; 214 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI) 215 OS << ' ' << *SI << " (#" << (*SI)->getNumber() << ')'; 216 OS << '\n'; 217 } 218} 219 220void MachineBasicBlock::removeLiveIn(unsigned Reg) { 221 livein_iterator I = std::find(livein_begin(), livein_end(), Reg); 222 assert(I != livein_end() && "Not a live in!"); 223 LiveIns.erase(I); 224} 225 226bool MachineBasicBlock::isLiveIn(unsigned Reg) const { 227 const_livein_iterator I = std::find(livein_begin(), livein_end(), Reg); 228 return I != livein_end(); 229} 230 231void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) { 232 getParent()->splice(NewAfter, this); 233} 234 235void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) { 236 MachineFunction::iterator BBI = NewBefore; 237 getParent()->splice(++BBI, this); 238} 239 240 241void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ) { 242 Successors.push_back(succ); 243 succ->addPredecessor(this); 244} 245 246void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) { 247 succ->removePredecessor(this); 248 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ); 249 assert(I != Successors.end() && "Not a current successor!"); 250 Successors.erase(I); 251} 252 253MachineBasicBlock::succ_iterator 254MachineBasicBlock::removeSuccessor(succ_iterator I) { 255 assert(I != Successors.end() && "Not a current successor!"); 256 (*I)->removePredecessor(this); 257 return Successors.erase(I); 258} 259 260void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) { 261 Predecessors.push_back(pred); 262} 263 264void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) { 265 std::vector<MachineBasicBlock *>::iterator I = 266 std::find(Predecessors.begin(), Predecessors.end(), pred); 267 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!"); 268 Predecessors.erase(I); 269} 270 271void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) { 272 if (this == fromMBB) 273 return; 274 275 for (MachineBasicBlock::succ_iterator I = fromMBB->succ_begin(), 276 E = fromMBB->succ_end(); I != E; ++I) 277 addSuccessor(*I); 278 279 while (!fromMBB->succ_empty()) 280 fromMBB->removeSuccessor(fromMBB->succ_begin()); 281} 282 283bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const { 284 std::vector<MachineBasicBlock *>::const_iterator I = 285 std::find(Successors.begin(), Successors.end(), MBB); 286 return I != Successors.end(); 287} 288 289bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const { 290 MachineFunction::const_iterator I(this); 291 return next(I) == MachineFunction::const_iterator(MBB); 292} 293 294/// removeFromParent - This method unlinks 'this' from the containing function, 295/// and returns it, but does not delete it. 296MachineBasicBlock *MachineBasicBlock::removeFromParent() { 297 assert(getParent() && "Not embedded in a function!"); 298 getParent()->remove(this); 299 return this; 300} 301 302 303/// eraseFromParent - This method unlinks 'this' from the containing function, 304/// and deletes it. 305void MachineBasicBlock::eraseFromParent() { 306 assert(getParent() && "Not embedded in a function!"); 307 getParent()->erase(this); 308} 309 310 311/// ReplaceUsesOfBlockWith - Given a machine basic block that branched to 312/// 'Old', change the code and CFG so that it branches to 'New' instead. 313void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old, 314 MachineBasicBlock *New) { 315 assert(Old != New && "Cannot replace self with self!"); 316 317 MachineBasicBlock::iterator I = end(); 318 while (I != begin()) { 319 --I; 320 if (!I->getDesc().isTerminator()) break; 321 322 // Scan the operands of this machine instruction, replacing any uses of Old 323 // with New. 324 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 325 if (I->getOperand(i).isMBB() && 326 I->getOperand(i).getMBB() == Old) 327 I->getOperand(i).setMBB(New); 328 } 329 330 // Update the successor information. 331 removeSuccessor(Old); 332 addSuccessor(New); 333} 334 335/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the 336/// CFG to be inserted. If we have proven that MBB can only branch to DestA and 337/// DestB, remove any other MBB successors from the CFG. DestA and DestB can 338/// be null. 339/// Besides DestA and DestB, retain other edges leading to LandingPads 340/// (currently there can be only one; we don't check or require that here). 341/// Note it is possible that DestA and/or DestB are LandingPads. 342bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA, 343 MachineBasicBlock *DestB, 344 bool isCond) { 345 bool MadeChange = false; 346 bool AddedFallThrough = false; 347 348 MachineFunction::iterator FallThru = next(MachineFunction::iterator(this)); 349 350 // If this block ends with a conditional branch that falls through to its 351 // successor, set DestB as the successor. 352 if (isCond) { 353 if (DestB == 0 && FallThru != getParent()->end()) { 354 DestB = FallThru; 355 AddedFallThrough = true; 356 } 357 } else { 358 // If this is an unconditional branch with no explicit dest, it must just be 359 // a fallthrough into DestB. 360 if (DestA == 0 && FallThru != getParent()->end()) { 361 DestA = FallThru; 362 AddedFallThrough = true; 363 } 364 } 365 366 MachineBasicBlock::succ_iterator SI = succ_begin(); 367 MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB; 368 while (SI != succ_end()) { 369 if (*SI == DestA && DestA == DestB) { 370 DestA = DestB = 0; 371 ++SI; 372 } else if (*SI == DestA) { 373 DestA = 0; 374 ++SI; 375 } else if (*SI == DestB) { 376 DestB = 0; 377 ++SI; 378 } else if ((*SI)->isLandingPad() && 379 *SI!=OrigDestA && *SI!=OrigDestB) { 380 ++SI; 381 } else { 382 // Otherwise, this is a superfluous edge, remove it. 383 SI = removeSuccessor(SI); 384 MadeChange = true; 385 } 386 } 387 if (!AddedFallThrough) { 388 assert(DestA == 0 && DestB == 0 && 389 "MachineCFG is missing edges!"); 390 } else if (isCond) { 391 assert(DestA == 0 && "MachineCFG is missing edges!"); 392 } 393 return MadeChange; 394} 395