lib/CodeGen/MachineBasicBlock.cpp

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