MachineBasicBlock.cpp revision cb406c25973b4e88a6c10ad839ef1beeb3664715 
1//===-- llvm/CodeGen/MachineBasicBlock.cpp ----------------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source 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/CodeGen/MachineInstr.h"
18#include "llvm/Target/MRegisterInfo.h"
19#include "llvm/Target/TargetData.h"
20#include "llvm/Target/TargetInstrInfo.h"
21#include "llvm/Target/TargetMachine.h"
22#include "llvm/Support/LeakDetector.h"
23#include <algorithm>
24using namespace llvm;
25
26MachineBasicBlock::~MachineBasicBlock() {
27  LeakDetector::removeGarbageObject(this);
28}
29
30std::ostream& llvm::operator<<(std::ostream &OS, const MachineBasicBlock &MBB) {
31  MBB.print(OS);
32  return OS;
33}
34
35// MBBs start out as #-1. When a MBB is added to a MachineFunction, it
36// gets the next available unique MBB number. If it is removed from a
37// MachineFunction, it goes back to being #-1.
38void ilist_traits<MachineBasicBlock>::addNodeToList(MachineBasicBlock* N) {
39  assert(N->Parent == 0 && "machine instruction already in a basic block");
40  N->Parent = Parent;
41  N->Number = Parent->addToMBBNumbering(N);
42  LeakDetector::removeGarbageObject(N);
43}
44
45void ilist_traits<MachineBasicBlock>::removeNodeFromList(MachineBasicBlock* N) {
46  assert(N->Parent != 0 && "machine instruction not in a basic block");
47  N->Parent->removeFromMBBNumbering(N->Number);
48  N->Number = -1;
49  N->Parent = 0;
50  LeakDetector::addGarbageObject(N);
51}
52
53
54MachineInstr* ilist_traits<MachineInstr>::createSentinel() {
55  MachineInstr* dummy = new MachineInstr();
56  LeakDetector::removeGarbageObject(dummy);
57  return dummy;
58}
59
60void ilist_traits<MachineInstr>::addNodeToList(MachineInstr* N) {
61  assert(N->parent == 0 && "machine instruction already in a basic block");
62  N->parent = parent;
63  LeakDetector::removeGarbageObject(N);
64}
65
66void ilist_traits<MachineInstr>::removeNodeFromList(MachineInstr* N) {
67  assert(N->parent != 0 && "machine instruction not in a basic block");
68  N->parent = 0;
69  LeakDetector::addGarbageObject(N);
70}
71
72void ilist_traits<MachineInstr>::transferNodesFromList(
73  iplist<MachineInstr, ilist_traits<MachineInstr> >& fromList,
74  ilist_iterator<MachineInstr> first,
75  ilist_iterator<MachineInstr> last) {
76  if (parent != fromList.parent)
77    for (; first != last; ++first)
78      first->parent = parent;
79}
80
81MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() {
82  const TargetInstrInfo& TII = *getParent()->getTarget().getInstrInfo();
83  iterator I = end();
84  while (I != begin() && TII.isTerminatorInstr((--I)->getOpcode()))
85    ; /*noop */
86  if (I != end() && !TII.isTerminatorInstr(I->getOpcode())) ++I;
87  return I;
88}
89
90void MachineBasicBlock::dump() const {
91  print(*cerr.stream());
92}
93
94static inline void OutputReg(std::ostream &os, unsigned RegNo,
95                             const MRegisterInfo *MRI = 0) {
96  if (!RegNo || MRegisterInfo::isPhysicalRegister(RegNo)) {
97    if (MRI)
98      os << " %" << MRI->get(RegNo).Name;
99    else
100      os << " %mreg(" << RegNo << ")";
101  } else
102    os << " %reg" << RegNo;
103}
104
105void MachineBasicBlock::print(std::ostream &OS) const {
106  const MachineFunction *MF = getParent();
107  if(!MF) {
108    OS << "Can't print out MachineBasicBlock because parent MachineFunction"
109       << " is null\n";
110    return;
111  }
112
113  const BasicBlock *LBB = getBasicBlock();
114  OS << "\n";
115  if (LBB) OS << LBB->getName() << ": ";
116  OS << (const void*)this
117     << ", LLVM BB @" << (const void*) LBB << ", ID#" << getNumber();
118  if (isLandingPad()) OS << ", EH LANDING PAD";
119  OS << ":\n";
120
121  const MRegisterInfo *MRI = MF->getTarget().getRegisterInfo();
122  if (!livein_empty()) {
123    OS << "Live Ins:";
124    for (const_livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
125      OutputReg(OS, *I, MRI);
126    OS << "\n";
127  }
128  // Print the preds of this block according to the CFG.
129  if (!pred_empty()) {
130    OS << "    Predecessors according to CFG:";
131    for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI)
132      OS << " " << *PI << " (#" << (*PI)->getNumber() << ")";
133    OS << "\n";
134  }
135
136  for (const_iterator I = begin(); I != end(); ++I) {
137    OS << "\t";
138    I->print(OS, &getParent()->getTarget());
139  }
140
141  // Print the successors of this block according to the CFG.
142  if (!succ_empty()) {
143    OS << "    Successors according to CFG:";
144    for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI)
145      OS << " " << *SI << " (#" << (*SI)->getNumber() << ")";
146    OS << "\n";
147  }
148}
149
150void MachineBasicBlock::removeLiveIn(unsigned Reg) {
151  livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
152  assert(I != livein_end() && "Not a live in!");
153  LiveIns.erase(I);
154}
155
156void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
157  MachineFunction::BasicBlockListType &BBList =getParent()->getBasicBlockList();
158  getParent()->getBasicBlockList().splice(NewAfter, BBList, this);
159}
160
161void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) {
162  MachineFunction::BasicBlockListType &BBList =getParent()->getBasicBlockList();
163  MachineFunction::iterator BBI = NewBefore;
164  getParent()->getBasicBlockList().splice(++BBI, BBList, this);
165}
166
167
168void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ) {
169  Successors.push_back(succ);
170  succ->addPredecessor(this);
171}
172
173void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
174  succ->removePredecessor(this);
175  succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
176  assert(I != Successors.end() && "Not a current successor!");
177  Successors.erase(I);
178}
179
180MachineBasicBlock::succ_iterator MachineBasicBlock::removeSuccessor(succ_iterator I) {
181  assert(I != Successors.end() && "Not a current successor!");
182  (*I)->removePredecessor(this);
183  return(Successors.erase(I));
184}
185
186void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
187  Predecessors.push_back(pred);
188}
189
190void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) {
191  std::vector<MachineBasicBlock *>::iterator I =
192    std::find(Predecessors.begin(), Predecessors.end(), pred);
193  assert(I != Predecessors.end() && "Pred is not a predecessor of this block!");
194  Predecessors.erase(I);
195}
196
197bool MachineBasicBlock::isSuccessor(MachineBasicBlock *MBB) const {
198  std::vector<MachineBasicBlock *>::const_iterator I =
199    std::find(Successors.begin(), Successors.end(), MBB);
200  return I != Successors.end();
201}
202
203/// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
204/// 'Old', change the code and CFG so that it branches to 'New' instead.
205void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
206                                               MachineBasicBlock *New) {
207  assert(Old != New && "Cannot replace self with self!");
208
209  MachineBasicBlock::iterator I = end();
210  while (I != begin()) {
211    --I;
212    if (!(I->getInstrDescriptor()->Flags & M_TERMINATOR_FLAG)) break;
213
214    // Scan the operands of this machine instruction, replacing any uses of Old
215    // with New.
216    for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
217      if (I->getOperand(i).isMachineBasicBlock() &&
218          I->getOperand(i).getMachineBasicBlock() == Old)
219        I->getOperand(i).setMachineBasicBlock(New);
220  }
221
222  // Update the successor information.  If New was already a successor, just
223  // remove the link to Old instead of creating another one.  PR 1444.
224  removeSuccessor(Old);
225  if (!isSuccessor(New))
226    addSuccessor(New);
227}
228
229/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
230/// CFG to be inserted.  If we have proven that MBB can only branch to DestA and
231/// DestB, remove any other MBB successors from the CFG.  DestA and DestB can
232/// be null.
233/// Besides DestA and DestB, retain other edges leading to LandingPads (currently
234/// there can be only one; we don't check or require that here).
235/// Note it is possible that DestA and/or DestB are LandingPads.
236bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
237                                             MachineBasicBlock *DestB,
238                                             bool isCond) {
239  bool MadeChange = false;
240  bool AddedFallThrough = false;
241
242  MachineBasicBlock *FallThru = getNext();
243
244  // If this block ends with a conditional branch that falls through to its
245  // successor, set DestB as the successor.
246  if (isCond) {
247    if (DestB == 0 && FallThru != getParent()->end()) {
248      DestB = FallThru;
249      AddedFallThrough = true;
250    }
251  } else {
252    // If this is an unconditional branch with no explicit dest, it must just be
253    // a fallthrough into DestB.
254    if (DestA == 0 && FallThru != getParent()->end()) {
255      DestA = FallThru;
256      AddedFallThrough = true;
257    }
258  }
259
260  MachineBasicBlock::succ_iterator SI = succ_begin();
261  MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB;
262  while (SI != succ_end()) {
263    if (*SI == DestA && DestA == DestB) {
264      DestA = DestB = 0;
265      ++SI;
266    } else if (*SI == DestA) {
267      DestA = 0;
268      ++SI;
269    } else if (*SI == DestB) {
270      DestB = 0;
271      ++SI;
272    } else if ((*SI)->isLandingPad() &&
273               *SI!=OrigDestA && *SI!=OrigDestB) {
274      ++SI;
275    } else {
276      // Otherwise, this is a superfluous edge, remove it.
277      SI = removeSuccessor(SI);
278      MadeChange = true;
279    }
280  }
281  if (!AddedFallThrough) {
282    assert(DestA == 0 && DestB == 0 &&
283           "MachineCFG is missing edges!");
284  } else if (isCond) {
285    assert(DestA == 0 && "MachineCFG is missing edges!");
286  }
287  return MadeChange;
288}
289