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 <algorithm>
  23 using namespace llvm;
  24
  25 MachineBasicBlock::MachineBasicBlock(MachineFunction &mf, const BasicBlock *bb)
  26   : BB(bb), Number(-1), xParent(&mf), Alignment(0), IsLandingPad(false) {
  27   Insts.Parent = this;
  28 }
  29
  30 MachineBasicBlock::~MachineBasicBlock() {
  31   LeakDetector::removeGarbageObject(this);
  32 }
  33
  34 std::ostream& llvm::operator<<(std::ostream &OS, const MachineBasicBlock &MBB) {
  35   MBB.print(OS);
  36   return OS;
  37 }
  38
  39 /// addNodeToList (MBB) - When an MBB is added to an MF, we need to update the
  40 /// parent pointer of the MBB, the MBB numbering, and any instructions in the
  41 /// MBB to be on the right operand list for registers.
  42 ///
  43 /// MBBs start out as #-1. When a MBB is added to a MachineFunction, it
  44 /// gets the next available unique MBB number. If it is removed from a
  45 /// MachineFunction, it goes back to being #-1.
  46 void ilist_traits<MachineBasicBlock>::addNodeToList(MachineBasicBlock* N) {
  47   MachineFunction &MF = *N->getParent();
  48   N->Number = MF.addToMBBNumbering(N);
  49
  50   // Make sure the instructions have their operands in the reginfo lists.
  51   MachineRegisterInfo &RegInfo = MF.getRegInfo();
  52   for (MachineBasicBlock::iterator I = N->begin(), E = N->end(); I != E; ++I)
  53     I->AddRegOperandsToUseLists(RegInfo);
  54
  55   LeakDetector::removeGarbageObject(N);
  56 }
  57
  58 void ilist_traits<MachineBasicBlock>::removeNodeFromList(MachineBasicBlock* N) {
  59   N->getParent()->removeFromMBBNumbering(N->Number);
  60   N->Number = -1;
  61   LeakDetector::addGarbageObject(N);
  62 }
  63
  64
  65 /// addNodeToList (MI) - When we add an instruction to a basic block
  66 /// list, we update its parent pointer and add its operands from reg use/def
  67 /// lists if appropriate.
  68 void ilist_traits<MachineInstr>::addNodeToList(MachineInstr* N) {
  69   assert(N->getParent() == 0 && "machine instruction already in a basic block");
  70   N->setParent(Parent);
  71
  72   // Add the instruction's register operands to their corresponding
  73   // use/def lists.
  74   MachineFunction *MF = Parent->getParent();
  75   N->AddRegOperandsToUseLists(MF->getRegInfo());
  76
  77   LeakDetector::removeGarbageObject(N);
  78 }
  79
  80 /// removeNodeFromList (MI) - When we remove an instruction from a basic block
  81 /// list, we update its parent pointer and remove its operands from reg use/def
  82 /// lists if appropriate.
  83 void ilist_traits<MachineInstr>::removeNodeFromList(MachineInstr* N) {
  84   assert(N->getParent() != 0 && "machine instruction not in a basic block");
  85
  86   // Remove from the use/def lists.
  87   N->RemoveRegOperandsFromUseLists();
  88
  89   N->setParent(0);
  90
  91   LeakDetector::addGarbageObject(N);
  92 }
  93
  94 /// transferNodesFromList (MI) - When moving a range of instructions from one
  95 /// MBB list to another, we need to update the parent pointers and the use/def
  96 /// lists.
  97 void ilist_traits<MachineInstr>::transferNodesFromList(
  98       ilist_traits<MachineInstr>& fromList,
  99       MachineBasicBlock::iterator first,
 100       MachineBasicBlock::iterator last) {
 101   assert(Parent->getParent() == fromList.Parent->getParent() &&
 102         "MachineInstr parent mismatch!");
 103
 104   // Splice within the same MBB -> no change.
 105   if (Parent == fromList.Parent) return;
 106
 107   // If splicing between two blocks within the same function, just update the
 108   // parent pointers.
 109   for (; first != last; ++first)
 110     first->setParent(Parent);
 111 }
 112
 113 void ilist_traits<MachineInstr>::deleteNode(MachineInstr* MI) {
 114   assert(!MI->getParent() && "MI is still in a block!");
 115   Parent->getParent()->DeleteMachineInstr(MI);
 116 }
 117
 118 MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() {
 119   iterator I = end();
 120   while (I != begin() && (--I)->getDesc().isTerminator())
 121     ; /*noop */
 122   if (I != end() && !I->getDesc().isTerminator()) ++I;
 123   return I;
 124 }
 125
 126 bool
 127 MachineBasicBlock::isOnlyReachableByFallthrough() const {
 128   return !isLandingPad() &&
 129          !pred_empty() &&
 130          next(pred_begin()) == pred_end() &&
 131          (*pred_begin())->isLayoutSuccessor(this) &&
 132          ((*pred_begin())->empty() ||
 133           !(*pred_begin())->back().getDesc().isBarrier());
 134 }
 135
 136 void MachineBasicBlock::dump() const {
 137   print(*cerr.stream());
 138 }
 139
 140 static inline void OutputReg(std::ostream &os, unsigned RegNo,
 141                              const TargetRegisterInfo *TRI = 0) {
 142   if (!RegNo || TargetRegisterInfo::isPhysicalRegister(RegNo)) {
 143     if (TRI)
 144       os << " %" << TRI->get(RegNo).Name;
 145     else
 146       os << " %mreg(" << RegNo << ")";
 147   } else
 148     os << " %reg" << RegNo;
 149 }
 150
 151 void MachineBasicBlock::print(std::ostream &OS) const {
 152   const MachineFunction *MF = getParent();
 153   if(!MF) {
 154     OS << "Can't print out MachineBasicBlock because parent MachineFunction"
 155        << " is null\n";
 156     return;
 157   }
 158
 159   const BasicBlock *LBB = getBasicBlock();
 160   OS << "\n";
 161   if (LBB) OS << LBB->getName() << ": ";
 162   OS << (const void*)this
 163      << ", LLVM BB @" << (const void*) LBB << ", ID#" << getNumber();
 164   if (Alignment) OS << ", Alignment " << Alignment;
 165   if (isLandingPad()) OS << ", EH LANDING PAD";
 166   OS << ":\n";
 167
 168   const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
 169   if (!livein_empty()) {
 170     OS << "Live Ins:";
 171     for (const_livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
 172       OutputReg(OS, *I, TRI);
 173     OS << "\n";
 174   }
 175   // Print the preds of this block according to the CFG.
 176   if (!pred_empty()) {
 177     OS << "    Predecessors according to CFG:";
 178     for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI)
 179       OS << " " << *PI << " (#" << (*PI)->getNumber() << ")";
 180     OS << "\n";
 181   }
 182
 183   for (const_iterator I = begin(); I != end(); ++I) {
 184     OS << "\t";
 185     I->print(OS, &getParent()->getTarget());
 186   }
 187
 188   // Print the successors of this block according to the CFG.
 189   if (!succ_empty()) {
 190     OS << "    Successors according to CFG:";
 191     for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI)
 192       OS << " " << *SI << " (#" << (*SI)->getNumber() << ")";
 193     OS << "\n";
 194   }
 195 }
 196
 197 void MachineBasicBlock::removeLiveIn(unsigned Reg) {
 198   livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
 199   assert(I != livein_end() && "Not a live in!");
 200   LiveIns.erase(I);
 201 }
 202
 203 bool MachineBasicBlock::isLiveIn(unsigned Reg) const {
 204   const_livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
 205   return I != livein_end();
 206 }
 207
 208 void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
 209   getParent()->splice(NewAfter, this);
 210 }
 211
 212 void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) {
 213   MachineFunction::iterator BBI = NewBefore;
 214   getParent()->splice(++BBI, this);
 215 }
 216
 217
 218 void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ) {
 219   Successors.push_back(succ);
 220   succ->addPredecessor(this);
 221 }
 222
 223 void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
 224   succ->removePredecessor(this);
 225   succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
 226   assert(I != Successors.end() && "Not a current successor!");
 227   Successors.erase(I);
 228 }
 229
 230 MachineBasicBlock::succ_iterator
 231 MachineBasicBlock::removeSuccessor(succ_iterator I) {
 232   assert(I != Successors.end() && "Not a current successor!");
 233   (*I)->removePredecessor(this);
 234   return Successors.erase(I);
 235 }
 236
 237 void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
 238   Predecessors.push_back(pred);
 239 }
 240
 241 void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) {
 242   std::vector<MachineBasicBlock *>::iterator I =
 243     std::find(Predecessors.begin(), Predecessors.end(), pred);
 244   assert(I != Predecessors.end() && "Pred is not a predecessor of this block!");
 245   Predecessors.erase(I);
 246 }
 247
 248 void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB)
 249 {
 250   if (this == fromMBB)
 251     return;
 252
 253   for(MachineBasicBlock::succ_iterator iter = fromMBB->succ_begin(),
 254       end = fromMBB->succ_end(); iter != end; ++iter) {
 255       addSuccessor(*iter);
 256   }
 257   while(!fromMBB->succ_empty())
 258     fromMBB->removeSuccessor(fromMBB->succ_begin());
 259 }
 260
 261 bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const {
 262   std::vector<MachineBasicBlock *>::const_iterator I =
 263     std::find(Successors.begin(), Successors.end(), MBB);
 264   return I != Successors.end();
 265 }
 266
 267 bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
 268   MachineFunction::const_iterator I(this);
 269   return next(I) == MachineFunction::const_iterator(MBB);
 270 }
 271
 272 /// removeFromParent - This method unlinks 'this' from the containing function,
 273 /// and returns it, but does not delete it.
 274 MachineBasicBlock *MachineBasicBlock::removeFromParent() {
 275   assert(getParent() && "Not embedded in a function!");
 276   getParent()->remove(this);
 277   return this;
 278 }
 279
 280
 281 /// eraseFromParent - This method unlinks 'this' from the containing function,
 282 /// and deletes it.
 283 void MachineBasicBlock::eraseFromParent() {
 284   assert(getParent() && "Not embedded in a function!");
 285   getParent()->erase(this);
 286 }
 287
 288
 289 /// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
 290 /// 'Old', change the code and CFG so that it branches to 'New' instead.
 291 void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
 292                                                MachineBasicBlock *New) {
 293   assert(Old != New && "Cannot replace self with self!");
 294
 295   MachineBasicBlock::iterator I = end();
 296   while (I != begin()) {
 297     --I;
 298     if (!I->getDesc().isTerminator()) break;
 299
 300     // Scan the operands of this machine instruction, replacing any uses of Old
 301     // with New.
 302     for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
 303       if (I->getOperand(i).isMBB() &&
 304           I->getOperand(i).getMBB() == Old)
 305         I->getOperand(i).setMBB(New);
 306   }
 307
 308   // Update the successor information.  If New was already a successor, just
 309   // remove the link to Old instead of creating another one.  PR 1444.
 310   removeSuccessor(Old);
 311   if (!isSuccessor(New))
 312     addSuccessor(New);
 313 }
 314
 315 /// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
 316 /// CFG to be inserted.  If we have proven that MBB can only branch to DestA and
 317 /// DestB, remove any other MBB successors from the CFG.  DestA and DestB can
 318 /// be null.
 319 /// Besides DestA and DestB, retain other edges leading to LandingPads
 320 /// (currently there can be only one; we don't check or require that here).
 321 /// Note it is possible that DestA and/or DestB are LandingPads.
 322 bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
 323                                              MachineBasicBlock *DestB,
 324                                              bool isCond) {
 325   bool MadeChange = false;
 326   bool AddedFallThrough = false;
 327
 328   MachineFunction::iterator FallThru = next(MachineFunction::iterator(this));
 329
 330   // If this block ends with a conditional branch that falls through to its
 331   // successor, set DestB as the successor.
 332   if (isCond) {
 333     if (DestB == 0 && FallThru != getParent()->end()) {
 334       DestB = FallThru;
 335       AddedFallThrough = true;
 336     }
 337   } else {
 338     // If this is an unconditional branch with no explicit dest, it must just be
 339     // a fallthrough into DestB.
 340     if (DestA == 0 && FallThru != getParent()->end()) {
 341       DestA = FallThru;
 342       AddedFallThrough = true;
 343     }
 344   }
 345
 346   MachineBasicBlock::succ_iterator SI = succ_begin();
 347   MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB;
 348   while (SI != succ_end()) {
 349     if (*SI == DestA && DestA == DestB) {
 350       DestA = DestB = 0;
 351       ++SI;
 352     } else if (*SI == DestA) {
 353       DestA = 0;
 354       ++SI;
 355     } else if (*SI == DestB) {
 356       DestB = 0;
 357       ++SI;
 358     } else if ((*SI)->isLandingPad() &&
 359                *SI!=OrigDestA && *SI!=OrigDestB) {
 360       ++SI;
 361     } else {
 362       // Otherwise, this is a superfluous edge, remove it.
 363       SI = removeSuccessor(SI);
 364       MadeChange = true;
 365     }
 366   }
 367   if (!AddedFallThrough) {
 368     assert(DestA == 0 && DestB == 0 &&
 369            "MachineCFG is missing edges!");
 370   } else if (isCond) {
 371     assert(DestA == 0 && "MachineCFG is missing edges!");
 372   }
 373   return MadeChange;
 374 }