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"
23 #include "llvm/Assembly/Writer.h"
27 MachineBasicBlock::MachineBasicBlock(MachineFunction &mf, const BasicBlock *bb)
28 : BB(bb), Number(-1), xParent(&mf), Alignment(0), IsLandingPad(false),
33 MachineBasicBlock::~MachineBasicBlock() {
34 LeakDetector::removeGarbageObject(this);
37 raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineBasicBlock &MBB) {
42 /// addNodeToList (MBB) - When an MBB is added to an MF, we need to update the
43 /// parent pointer of the MBB, the MBB numbering, and any instructions in the
44 /// MBB to be on the right operand list for registers.
46 /// MBBs start out as #-1. When a MBB is added to a MachineFunction, it
47 /// gets the next available unique MBB number. If it is removed from a
48 /// MachineFunction, it goes back to being #-1.
49 void ilist_traits<MachineBasicBlock>::addNodeToList(MachineBasicBlock *N) {
50 MachineFunction &MF = *N->getParent();
51 N->Number = MF.addToMBBNumbering(N);
53 // Make sure the instructions have their operands in the reginfo lists.
54 MachineRegisterInfo &RegInfo = MF.getRegInfo();
55 for (MachineBasicBlock::iterator I = N->begin(), E = N->end(); I != E; ++I)
56 I->AddRegOperandsToUseLists(RegInfo);
58 LeakDetector::removeGarbageObject(N);
61 void ilist_traits<MachineBasicBlock>::removeNodeFromList(MachineBasicBlock *N) {
62 N->getParent()->removeFromMBBNumbering(N->Number);
64 LeakDetector::addGarbageObject(N);
68 /// addNodeToList (MI) - When we add an instruction to a basic block
69 /// list, we update its parent pointer and add its operands from reg use/def
70 /// lists if appropriate.
71 void ilist_traits<MachineInstr>::addNodeToList(MachineInstr *N) {
72 assert(N->getParent() == 0 && "machine instruction already in a basic block");
75 // Add the instruction's register operands to their corresponding
77 MachineFunction *MF = Parent->getParent();
78 N->AddRegOperandsToUseLists(MF->getRegInfo());
80 LeakDetector::removeGarbageObject(N);
83 /// removeNodeFromList (MI) - When we remove an instruction from a basic block
84 /// list, we update its parent pointer and remove its operands from reg use/def
85 /// lists if appropriate.
86 void ilist_traits<MachineInstr>::removeNodeFromList(MachineInstr *N) {
87 assert(N->getParent() != 0 && "machine instruction not in a basic block");
89 // Remove from the use/def lists.
90 N->RemoveRegOperandsFromUseLists();
94 LeakDetector::addGarbageObject(N);
97 /// transferNodesFromList (MI) - When moving a range of instructions from one
98 /// MBB list to another, we need to update the parent pointers and the use/def
100 void ilist_traits<MachineInstr>::
101 transferNodesFromList(ilist_traits<MachineInstr> &fromList,
102 MachineBasicBlock::iterator first,
103 MachineBasicBlock::iterator last) {
104 assert(Parent->getParent() == fromList.Parent->getParent() &&
105 "MachineInstr parent mismatch!");
107 // Splice within the same MBB -> no change.
108 if (Parent == fromList.Parent) return;
110 // If splicing between two blocks within the same function, just update the
112 for (; first != last; ++first)
113 first->setParent(Parent);
116 void ilist_traits<MachineInstr>::deleteNode(MachineInstr* MI) {
117 assert(!MI->getParent() && "MI is still in a block!");
118 Parent->getParent()->DeleteMachineInstr(MI);
121 MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() {
123 while (I != begin() && (--I)->getDesc().isTerminator())
125 if (I != end() && !I->getDesc().isTerminator()) ++I;
129 /// isOnlyReachableViaFallthough - Return true if this basic block has
130 /// exactly one predecessor and the control transfer mechanism between
131 /// the predecessor and this block is a fall-through.
132 bool MachineBasicBlock::isOnlyReachableByFallthrough() const {
133 // If this is a landing pad, it isn't a fall through. If it has no preds,
134 // then nothing falls through to it.
135 if (isLandingPad() || pred_empty())
138 // If there isn't exactly one predecessor, it can't be a fall through.
139 const_pred_iterator PI = pred_begin(), PI2 = PI;
141 if (PI2 != pred_end())
144 // The predecessor has to be immediately before this block.
145 const MachineBasicBlock *Pred = *PI;
147 if (!Pred->isLayoutSuccessor(this))
150 // If the block is completely empty, then it definitely does fall through.
154 // Otherwise, check the last instruction.
155 const MachineInstr &LastInst = Pred->back();
156 return !LastInst.getDesc().isBarrier();
159 void MachineBasicBlock::dump() const {
163 static inline void OutputReg(raw_ostream &os, unsigned RegNo,
164 const TargetRegisterInfo *TRI = 0) {
165 if (RegNo != 0 && TargetRegisterInfo::isPhysicalRegister(RegNo)) {
167 os << " %" << TRI->get(RegNo).Name;
169 os << " %physreg" << RegNo;
171 os << " %reg" << RegNo;
174 void MachineBasicBlock::print(raw_ostream &OS) const {
175 const MachineFunction *MF = getParent();
177 OS << "Can't print out MachineBasicBlock because parent MachineFunction"
182 if (Alignment) { OS << "Alignment " << Alignment << "\n"; }
184 OS << "BB#" << getNumber() << ": ";
186 const char *Comma = "";
187 if (const BasicBlock *LBB = getBasicBlock()) {
188 OS << Comma << "derived from LLVM BB ";
189 WriteAsOperand(OS, LBB, /*PrintType=*/false);
192 if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; }
193 if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; }
196 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
197 if (!livein_empty()) {
199 for (const_livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
200 OutputReg(OS, *I, TRI);
203 // Print the preds of this block according to the CFG.
205 OS << " Predecessors according to CFG:";
206 for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI)
207 OS << " BB#" << (*PI)->getNumber();
211 for (const_iterator I = begin(); I != end(); ++I) {
213 I->print(OS, &getParent()->getTarget());
216 // Print the successors of this block according to the CFG.
218 OS << " Successors according to CFG:";
219 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI)
220 OS << " BB#" << (*SI)->getNumber();
225 void MachineBasicBlock::removeLiveIn(unsigned Reg) {
226 livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
227 assert(I != livein_end() && "Not a live in!");
231 bool MachineBasicBlock::isLiveIn(unsigned Reg) const {
232 const_livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
233 return I != livein_end();
236 void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
237 getParent()->splice(NewAfter, this);
240 void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) {
241 MachineFunction::iterator BBI = NewBefore;
242 getParent()->splice(++BBI, this);
246 void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ) {
247 Successors.push_back(succ);
248 succ->addPredecessor(this);
251 void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
252 succ->removePredecessor(this);
253 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
254 assert(I != Successors.end() && "Not a current successor!");
258 MachineBasicBlock::succ_iterator
259 MachineBasicBlock::removeSuccessor(succ_iterator I) {
260 assert(I != Successors.end() && "Not a current successor!");
261 (*I)->removePredecessor(this);
262 return Successors.erase(I);
265 void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
266 Predecessors.push_back(pred);
269 void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) {
270 std::vector<MachineBasicBlock *>::iterator I =
271 std::find(Predecessors.begin(), Predecessors.end(), pred);
272 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!");
273 Predecessors.erase(I);
276 void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) {
280 for (MachineBasicBlock::succ_iterator I = fromMBB->succ_begin(),
281 E = fromMBB->succ_end(); I != E; ++I)
284 while (!fromMBB->succ_empty())
285 fromMBB->removeSuccessor(fromMBB->succ_begin());
288 bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const {
289 std::vector<MachineBasicBlock *>::const_iterator I =
290 std::find(Successors.begin(), Successors.end(), MBB);
291 return I != Successors.end();
294 bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
295 MachineFunction::const_iterator I(this);
296 return next(I) == MachineFunction::const_iterator(MBB);
299 /// removeFromParent - This method unlinks 'this' from the containing function,
300 /// and returns it, but does not delete it.
301 MachineBasicBlock *MachineBasicBlock::removeFromParent() {
302 assert(getParent() && "Not embedded in a function!");
303 getParent()->remove(this);
308 /// eraseFromParent - This method unlinks 'this' from the containing function,
310 void MachineBasicBlock::eraseFromParent() {
311 assert(getParent() && "Not embedded in a function!");
312 getParent()->erase(this);
316 /// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
317 /// 'Old', change the code and CFG so that it branches to 'New' instead.
318 void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
319 MachineBasicBlock *New) {
320 assert(Old != New && "Cannot replace self with self!");
322 MachineBasicBlock::iterator I = end();
323 while (I != begin()) {
325 if (!I->getDesc().isTerminator()) break;
327 // Scan the operands of this machine instruction, replacing any uses of Old
329 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
330 if (I->getOperand(i).isMBB() &&
331 I->getOperand(i).getMBB() == Old)
332 I->getOperand(i).setMBB(New);
335 // Update the successor information.
336 removeSuccessor(Old);
340 /// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
341 /// CFG to be inserted. If we have proven that MBB can only branch to DestA and
342 /// DestB, remove any other MBB successors from the CFG. DestA and DestB can
344 /// Besides DestA and DestB, retain other edges leading to LandingPads
345 /// (currently there can be only one; we don't check or require that here).
346 /// Note it is possible that DestA and/or DestB are LandingPads.
347 bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
348 MachineBasicBlock *DestB,
350 bool MadeChange = false;
351 bool AddedFallThrough = false;
353 MachineFunction::iterator FallThru = next(MachineFunction::iterator(this));
355 // If this block ends with a conditional branch that falls through to its
356 // successor, set DestB as the successor.
358 if (DestB == 0 && FallThru != getParent()->end()) {
360 AddedFallThrough = true;
363 // If this is an unconditional branch with no explicit dest, it must just be
364 // a fallthrough into DestB.
365 if (DestA == 0 && FallThru != getParent()->end()) {
367 AddedFallThrough = true;
371 MachineBasicBlock::succ_iterator SI = succ_begin();
372 MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB;
373 while (SI != succ_end()) {
374 if (*SI == DestA && DestA == DestB) {
377 } else if (*SI == DestA) {
380 } else if (*SI == DestB) {
383 } else if ((*SI)->isLandingPad() &&
384 *SI!=OrigDestA && *SI!=OrigDestB) {
387 // Otherwise, this is a superfluous edge, remove it.
388 SI = removeSuccessor(SI);
392 if (!AddedFallThrough) {
393 assert(DestA == 0 && DestB == 0 &&
394 "MachineCFG is missing edges!");
396 assert(DestA == 0 && "MachineCFG is missing edges!");