1 //===-- llvm/CodeGen/MachineBasicBlock.cpp ----------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Collect the sequence of machine instructions for a basic block.
12 //===----------------------------------------------------------------------===//
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"
26 MachineBasicBlock::MachineBasicBlock(MachineFunction &mf, const BasicBlock *bb)
27 : BB(bb), Number(-1), xParent(&mf), Alignment(0), IsLandingPad(false) {
31 MachineBasicBlock::~MachineBasicBlock() {
32 LeakDetector::removeGarbageObject(this);
35 std::ostream &llvm::operator<<(std::ostream &OS, const MachineBasicBlock &MBB) {
39 raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineBasicBlock &MBB) {
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.
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);
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);
60 LeakDetector::removeGarbageObject(N);
63 void ilist_traits<MachineBasicBlock>::removeNodeFromList(MachineBasicBlock *N) {
64 N->getParent()->removeFromMBBNumbering(N->Number);
66 LeakDetector::addGarbageObject(N);
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");
77 // Add the instruction's register operands to their corresponding
79 MachineFunction *MF = Parent->getParent();
80 N->AddRegOperandsToUseLists(MF->getRegInfo());
82 LeakDetector::removeGarbageObject(N);
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");
91 // Remove from the use/def lists.
92 N->RemoveRegOperandsFromUseLists();
96 LeakDetector::addGarbageObject(N);
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
102 void ilist_traits<MachineInstr>::
103 transferNodesFromList(ilist_traits<MachineInstr> &fromList,
104 MachineBasicBlock::iterator first,
105 MachineBasicBlock::iterator last) {
106 assert(Parent->getParent() == fromList.Parent->getParent() &&
107 "MachineInstr parent mismatch!");
109 // Splice within the same MBB -> no change.
110 if (Parent == fromList.Parent) return;
112 // If splicing between two blocks within the same function, just update the
114 for (; first != last; ++first)
115 first->setParent(Parent);
118 void ilist_traits<MachineInstr>::deleteNode(MachineInstr* MI) {
119 assert(!MI->getParent() && "MI is still in a block!");
120 Parent->getParent()->DeleteMachineInstr(MI);
123 MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() {
125 while (I != begin() && (--I)->getDesc().isTerminator())
127 if (I != end() && !I->getDesc().isTerminator()) ++I;
131 /// isOnlyReachableViaFallthough - Return true if this basic block has
132 /// exactly one predecessor and the control transfer mechanism between
133 /// the predecessor and this block is a fall-through.
134 bool MachineBasicBlock::isOnlyReachableByFallthrough() const {
135 // If this is a landing pad, it isn't a fall through. If it has no preds,
136 // then nothing falls through to it.
137 if (isLandingPad() || pred_empty())
140 // If there isn't exactly one predecessor, it can't be a fall through.
141 const_pred_iterator PI = pred_begin(), PI2 = PI;
143 if (PI2 != pred_end())
146 // The predecessor has to be immediately before this block.
147 const MachineBasicBlock *Pred = *PI;
149 if (!Pred->isLayoutSuccessor(this))
152 // If the block is completely empty, then it definitely does fall through.
156 // Otherwise, check the last instruction.
157 const MachineInstr &LastInst = Pred->back();
158 return !LastInst.getDesc().isBarrier();
161 void MachineBasicBlock::dump() const {
162 print(*cerr.stream());
165 static inline void OutputReg(raw_ostream &os, unsigned RegNo,
166 const TargetRegisterInfo *TRI = 0) {
167 if (!RegNo || TargetRegisterInfo::isPhysicalRegister(RegNo)) {
169 os << " %" << TRI->get(RegNo).Name;
171 os << " %mreg(" << RegNo << ")";
173 os << " %reg" << RegNo;
176 void MachineBasicBlock::print(std::ostream &OS) const {
177 raw_os_ostream RawOS(OS);
181 void MachineBasicBlock::print(raw_ostream &OS) const {
182 const MachineFunction *MF = getParent();
184 OS << "Can't print out MachineBasicBlock because parent MachineFunction"
189 const BasicBlock *LBB = getBasicBlock();
191 if (LBB) OS << LBB->getName() << ": ";
192 OS << (const void*)this
193 << ", LLVM BB @" << (const void*) LBB << ", ID#" << getNumber();
194 if (Alignment) OS << ", Alignment " << Alignment;
195 if (isLandingPad()) OS << ", EH LANDING PAD";
198 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
199 if (!livein_empty()) {
201 for (const_livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
202 OutputReg(OS, *I, TRI);
205 // Print the preds of this block according to the CFG.
207 OS << " Predecessors according to CFG:";
208 for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI)
209 OS << ' ' << *PI << " (#" << (*PI)->getNumber() << ')';
213 for (const_iterator I = begin(); I != end(); ++I) {
215 I->print(OS, &getParent()->getTarget());
218 // Print the successors of this block according to the CFG.
220 OS << " Successors according to CFG:";
221 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI)
222 OS << ' ' << *SI << " (#" << (*SI)->getNumber() << ')';
227 void MachineBasicBlock::removeLiveIn(unsigned Reg) {
228 livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
229 assert(I != livein_end() && "Not a live in!");
233 bool MachineBasicBlock::isLiveIn(unsigned Reg) const {
234 const_livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
235 return I != livein_end();
238 void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
239 getParent()->splice(NewAfter, this);
242 void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) {
243 MachineFunction::iterator BBI = NewBefore;
244 getParent()->splice(++BBI, this);
248 void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ) {
249 Successors.push_back(succ);
250 succ->addPredecessor(this);
253 void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
254 succ->removePredecessor(this);
255 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
256 assert(I != Successors.end() && "Not a current successor!");
260 MachineBasicBlock::succ_iterator
261 MachineBasicBlock::removeSuccessor(succ_iterator I) {
262 assert(I != Successors.end() && "Not a current successor!");
263 (*I)->removePredecessor(this);
264 return Successors.erase(I);
267 void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
268 Predecessors.push_back(pred);
271 void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) {
272 std::vector<MachineBasicBlock *>::iterator I =
273 std::find(Predecessors.begin(), Predecessors.end(), pred);
274 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!");
275 Predecessors.erase(I);
278 void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) {
282 for (MachineBasicBlock::succ_iterator I = fromMBB->succ_begin(),
283 E = fromMBB->succ_end(); I != E; ++I)
286 while (!fromMBB->succ_empty())
287 fromMBB->removeSuccessor(fromMBB->succ_begin());
290 bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const {
291 std::vector<MachineBasicBlock *>::const_iterator I =
292 std::find(Successors.begin(), Successors.end(), MBB);
293 return I != Successors.end();
296 bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
297 MachineFunction::const_iterator I(this);
298 return next(I) == MachineFunction::const_iterator(MBB);
301 /// removeFromParent - This method unlinks 'this' from the containing function,
302 /// and returns it, but does not delete it.
303 MachineBasicBlock *MachineBasicBlock::removeFromParent() {
304 assert(getParent() && "Not embedded in a function!");
305 getParent()->remove(this);
310 /// eraseFromParent - This method unlinks 'this' from the containing function,
312 void MachineBasicBlock::eraseFromParent() {
313 assert(getParent() && "Not embedded in a function!");
314 getParent()->erase(this);
318 /// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
319 /// 'Old', change the code and CFG so that it branches to 'New' instead.
320 void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
321 MachineBasicBlock *New) {
322 assert(Old != New && "Cannot replace self with self!");
324 MachineBasicBlock::iterator I = end();
325 while (I != begin()) {
327 if (!I->getDesc().isTerminator()) break;
329 // Scan the operands of this machine instruction, replacing any uses of Old
331 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
332 if (I->getOperand(i).isMBB() &&
333 I->getOperand(i).getMBB() == Old)
334 I->getOperand(i).setMBB(New);
337 // Update the successor information.
338 removeSuccessor(Old);
342 /// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
343 /// CFG to be inserted. If we have proven that MBB can only branch to DestA and
344 /// DestB, remove any other MBB successors from the CFG. DestA and DestB can
346 /// Besides DestA and DestB, retain other edges leading to LandingPads
347 /// (currently there can be only one; we don't check or require that here).
348 /// Note it is possible that DestA and/or DestB are LandingPads.
349 bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
350 MachineBasicBlock *DestB,
352 bool MadeChange = false;
353 bool AddedFallThrough = false;
355 MachineFunction::iterator FallThru = next(MachineFunction::iterator(this));
357 // If this block ends with a conditional branch that falls through to its
358 // successor, set DestB as the successor.
360 if (DestB == 0 && FallThru != getParent()->end()) {
362 AddedFallThrough = true;
365 // If this is an unconditional branch with no explicit dest, it must just be
366 // a fallthrough into DestB.
367 if (DestA == 0 && FallThru != getParent()->end()) {
369 AddedFallThrough = true;
373 MachineBasicBlock::succ_iterator SI = succ_begin();
374 MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB;
375 while (SI != succ_end()) {
376 if (*SI == DestA && DestA == DestB) {
379 } else if (*SI == DestA) {
382 } else if (*SI == DestB) {
385 } else if ((*SI)->isLandingPad() &&
386 *SI!=OrigDestA && *SI!=OrigDestB) {
389 // Otherwise, this is a superfluous edge, remove it.
390 SI = removeSuccessor(SI);
394 if (!AddedFallThrough) {
395 assert(DestA == 0 && DestB == 0 &&
396 "MachineCFG is missing edges!");
398 assert(DestA == 0 && "MachineCFG is missing edges!");