MachineBasicBlock.cpp revision 2bdb7d0cc88881857073b36f4a09ebe2f2008c24 
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  if (I != end() && !TII.isTerminatorInstr(I->getOpcode())) ++I;
86  return I;
87}
88
89void MachineBasicBlock::dump() const {
90  print(*cerr.stream());
91}
92
93static inline void OutputReg(std::ostream &os, unsigned RegNo,
94                             const MRegisterInfo *MRI = 0) {
95  if (!RegNo || MRegisterInfo::isPhysicalRegister(RegNo)) {
96    if (MRI)
97      os << " %" << MRI->get(RegNo).Name;
98    else
99      os << " %mreg(" << RegNo << ")";
100  } else
101    os << " %reg" << RegNo;
102}
103
104void MachineBasicBlock::print(std::ostream &OS) const {
105  const MachineFunction *MF = getParent();
106  if(!MF) {
107    OS << "Can't print out MachineBasicBlock because parent MachineFunction"
108       << " is null\n";
109    return;
110  }
111
112  const BasicBlock *LBB = getBasicBlock();
113  OS << "\n";
114  if (LBB) OS << LBB->getName() << ": ";
115  OS << (const void*)this
116     << ", LLVM BB @" << (const void*) LBB << ", ID#" << getNumber();
117  if (isLandingPad()) OS << ", EH LANDING PAD";
118  OS << ":\n";
119
120  const MRegisterInfo *MRI = MF->getTarget().getRegisterInfo();
121  if (livein_begin() != livein_end()) {
122    OS << "Live Ins:";
123    for (const_livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
124      OutputReg(OS, *I, MRI);
125    OS << "\n";
126  }
127  // Print the preds of this block according to the CFG.
128  if (!pred_empty()) {
129    OS << "    Predecessors according to CFG:";
130    for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI)
131      OS << " " << *PI << " (#" << (*PI)->getNumber() << ")";
132    OS << "\n";
133  }
134
135  for (const_iterator I = begin(); I != end(); ++I) {
136    OS << "\t";
137    I->print(OS, &getParent()->getTarget());
138  }
139
140  // Print the successors of this block according to the CFG.
141  if (!succ_empty()) {
142    OS << "    Successors according to CFG:";
143    for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI)
144      OS << " " << *SI << " (#" << (*SI)->getNumber() << ")";
145    OS << "\n";
146  }
147}
148
149void MachineBasicBlock::removeLiveIn(unsigned Reg) {
150  livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
151  assert(I != livein_end() && "Not a live in!");
152  LiveIns.erase(I);
153}
154
155void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
156  MachineFunction::BasicBlockListType &BBList =getParent()->getBasicBlockList();
157  getParent()->getBasicBlockList().splice(NewAfter, BBList, this);
158}
159
160void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) {
161  MachineFunction::BasicBlockListType &BBList =getParent()->getBasicBlockList();
162  MachineFunction::iterator BBI = NewBefore;
163  getParent()->getBasicBlockList().splice(++BBI, BBList, this);
164}
165
166
167void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ) {
168  Successors.push_back(succ);
169  succ->addPredecessor(this);
170}
171
172void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
173  succ->removePredecessor(this);
174  succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
175  assert(I != Successors.end() && "Not a current successor!");
176  Successors.erase(I);
177}
178
179void MachineBasicBlock::removeSuccessor(succ_iterator I) {
180  assert(I != Successors.end() && "Not a current successor!");
181  (*I)->removePredecessor(this);
182  Successors.erase(I);
183}
184
185void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
186  Predecessors.push_back(pred);
187}
188
189void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) {
190  std::vector<MachineBasicBlock *>::iterator I =
191    std::find(Predecessors.begin(), Predecessors.end(), pred);
192  assert(I != Predecessors.end() && "Pred is not a predecessor of this block!");
193  Predecessors.erase(I);
194}
195
196bool MachineBasicBlock::isSuccessor(MachineBasicBlock *MBB) const {
197  std::vector<MachineBasicBlock *>::const_iterator I =
198    std::find(Successors.begin(), Successors.end(), MBB);
199  return I != Successors.end();
200}
201
202/// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
203/// 'Old', change the code and CFG so that it branches to 'New' instead.
204void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
205                                               MachineBasicBlock *New) {
206  assert(Old != New && "Cannot replace self with self!");
207
208  MachineBasicBlock::iterator I = end();
209  while (I != begin()) {
210    --I;
211    if (!(I->getInstrDescriptor()->Flags & M_TERMINATOR_FLAG)) break;
212
213    // Scan the operands of this machine instruction, replacing any uses of Old
214    // with New.
215    for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
216      if (I->getOperand(i).isMachineBasicBlock() &&
217          I->getOperand(i).getMachineBasicBlock() == Old)
218        I->getOperand(i).setMachineBasicBlock(New);
219  }
220
221  // Update the successor information.  If New was already a successor, just
222  // remove the link to Old instead of creating another one.  PR 1444.
223  removeSuccessor(Old);
224  if (!isSuccessor(New))
225    addSuccessor(New);
226}
227
228/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
229/// CFG to be inserted.  If we have proven that MBB can only branch to DestA and
230/// DestB, remove any other MBB successors from the CFG.  DestA and DestB can
231/// be null.
232/// Besides DestA and DestB, retain other edges leading to LandingPads (currently
233/// there can be only one; we don't check or require that here).
234/// Note it is possible that DestA and/or DestB are LandingPads.
235bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
236                                             MachineBasicBlock *DestB,
237                                             bool isCond) {
238  bool MadeChange = false;
239  bool AddedFallThrough = false;
240
241  MachineBasicBlock *FallThru = getNext();
242
243  // If this block ends with a conditional branch that falls through to its
244  // successor, set DestB as the successor.
245  if (isCond) {
246    if (DestB == 0 && FallThru != getParent()->end()) {
247      DestB = FallThru;
248      AddedFallThrough = true;
249    }
250  } else {
251    // If this is an unconditional branch with no explicit dest, it must just be
252    // a fallthrough into DestB.
253    if (DestA == 0 && FallThru != getParent()->end()) {
254      DestA = FallThru;
255      AddedFallThrough = true;
256    }
257  }
258
259  MachineBasicBlock::succ_iterator SI = succ_begin();
260  MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB;
261  while (SI != succ_end()) {
262    if (*SI == DestA && DestA == DestB) {
263      DestA = DestB = 0;
264      ++SI;
265    } else if (*SI == DestA) {
266      DestA = 0;
267      ++SI;
268    } else if (*SI == DestB) {
269      DestB = 0;
270      ++SI;
271    } else if ((*SI)->isLandingPad() &&
272               *SI!=OrigDestA && *SI!=OrigDestB) {
273      ++SI;
274    } else {
275      // Otherwise, this is a superfluous edge, remove it.
276      removeSuccessor(SI);
277      MadeChange = true;
278    }
279  }
280  if (!AddedFallThrough) {
281    assert(DestA == 0 && DestB == 0 &&
282           "MachineCFG is missing edges!");
283  } else if (isCond) {
284    assert(DestA == 0 && "MachineCFG is missing edges!");
285  }
286  return MadeChange;
287}
288