LLVM API Documentation
00001 //===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by the LLVM research group and is distributed under 00006 // the University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // This file defines the LoopInfo class that is used to identify natural loops 00011 // and determine the loop depth of various nodes of the CFG. Note that the 00012 // loops identified may actually be several natural loops that share the same 00013 // header node... not just a single natural loop. 00014 // 00015 //===----------------------------------------------------------------------===// 00016 00017 #include "llvm/Analysis/LoopInfo.h" 00018 #include "llvm/Constants.h" 00019 #include "llvm/Instructions.h" 00020 #include "llvm/Analysis/Dominators.h" 00021 #include "llvm/Assembly/Writer.h" 00022 #include "llvm/Support/CFG.h" 00023 #include "llvm/ADT/DepthFirstIterator.h" 00024 #include <algorithm> 00025 #include <iostream> 00026 using namespace llvm; 00027 00028 static RegisterAnalysis<LoopInfo> 00029 X("loops", "Natural Loop Construction", true); 00030 00031 //===----------------------------------------------------------------------===// 00032 // Loop implementation 00033 // 00034 bool Loop::contains(const BasicBlock *BB) const { 00035 return std::find(Blocks.begin(), Blocks.end(), BB) != Blocks.end(); 00036 } 00037 00038 bool Loop::isLoopExit(const BasicBlock *BB) const { 00039 for (succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB); 00040 SI != SE; ++SI) { 00041 if (!contains(*SI)) 00042 return true; 00043 } 00044 return false; 00045 } 00046 00047 /// getNumBackEdges - Calculate the number of back edges to the loop header. 00048 /// 00049 unsigned Loop::getNumBackEdges() const { 00050 unsigned NumBackEdges = 0; 00051 BasicBlock *H = getHeader(); 00052 00053 for (pred_iterator I = pred_begin(H), E = pred_end(H); I != E; ++I) 00054 if (contains(*I)) 00055 ++NumBackEdges; 00056 00057 return NumBackEdges; 00058 } 00059 00060 /// isLoopInvariant - Return true if the specified value is loop invariant 00061 /// 00062 bool Loop::isLoopInvariant(Value *V) const { 00063 if (Instruction *I = dyn_cast<Instruction>(V)) 00064 return !contains(I->getParent()); 00065 return true; // All non-instructions are loop invariant 00066 } 00067 00068 void Loop::print(std::ostream &OS, unsigned Depth) const { 00069 OS << std::string(Depth*2, ' ') << "Loop Containing: "; 00070 00071 for (unsigned i = 0; i < getBlocks().size(); ++i) { 00072 if (i) OS << ","; 00073 WriteAsOperand(OS, getBlocks()[i], false); 00074 } 00075 OS << "\n"; 00076 00077 for (iterator I = begin(), E = end(); I != E; ++I) 00078 (*I)->print(OS, Depth+2); 00079 } 00080 00081 void Loop::dump() const { 00082 print(std::cerr); 00083 } 00084 00085 00086 //===----------------------------------------------------------------------===// 00087 // LoopInfo implementation 00088 // 00089 void LoopInfo::stub() {} 00090 00091 bool LoopInfo::runOnFunction(Function &) { 00092 releaseMemory(); 00093 Calculate(getAnalysis<ETForest>()); // Update 00094 return false; 00095 } 00096 00097 void LoopInfo::releaseMemory() { 00098 for (std::vector<Loop*>::iterator I = TopLevelLoops.begin(), 00099 E = TopLevelLoops.end(); I != E; ++I) 00100 delete *I; // Delete all of the loops... 00101 00102 BBMap.clear(); // Reset internal state of analysis 00103 TopLevelLoops.clear(); 00104 } 00105 00106 00107 void LoopInfo::Calculate(ETForest &EF) { 00108 BasicBlock *RootNode = EF.getRoot(); 00109 00110 for (df_iterator<BasicBlock*> NI = df_begin(RootNode), 00111 NE = df_end(RootNode); NI != NE; ++NI) 00112 if (Loop *L = ConsiderForLoop(*NI, EF)) 00113 TopLevelLoops.push_back(L); 00114 } 00115 00116 void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const { 00117 AU.setPreservesAll(); 00118 AU.addRequired<ETForest>(); 00119 } 00120 00121 void LoopInfo::print(std::ostream &OS, const Module* ) const { 00122 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 00123 TopLevelLoops[i]->print(OS); 00124 #if 0 00125 for (std::map<BasicBlock*, Loop*>::const_iterator I = BBMap.begin(), 00126 E = BBMap.end(); I != E; ++I) 00127 OS << "BB '" << I->first->getName() << "' level = " 00128 << I->second->getLoopDepth() << "\n"; 00129 #endif 00130 } 00131 00132 static bool isNotAlreadyContainedIn(Loop *SubLoop, Loop *ParentLoop) { 00133 if (SubLoop == 0) return true; 00134 if (SubLoop == ParentLoop) return false; 00135 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 00136 } 00137 00138 Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, ETForest &EF) { 00139 if (BBMap.find(BB) != BBMap.end()) return 0; // Haven't processed this node? 00140 00141 std::vector<BasicBlock *> TodoStack; 00142 00143 // Scan the predecessors of BB, checking to see if BB dominates any of 00144 // them. This identifies backedges which target this node... 00145 for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I) 00146 if (EF.dominates(BB, *I)) // If BB dominates it's predecessor... 00147 TodoStack.push_back(*I); 00148 00149 if (TodoStack.empty()) return 0; // No backedges to this block... 00150 00151 // Create a new loop to represent this basic block... 00152 Loop *L = new Loop(BB); 00153 BBMap[BB] = L; 00154 00155 BasicBlock *EntryBlock = &BB->getParent()->getEntryBlock(); 00156 00157 while (!TodoStack.empty()) { // Process all the nodes in the loop 00158 BasicBlock *X = TodoStack.back(); 00159 TodoStack.pop_back(); 00160 00161 if (!L->contains(X) && // As of yet unprocessed?? 00162 EF.dominates(EntryBlock, X)) { // X is reachable from entry block? 00163 // Check to see if this block already belongs to a loop. If this occurs 00164 // then we have a case where a loop that is supposed to be a child of the 00165 // current loop was processed before the current loop. When this occurs, 00166 // this child loop gets added to a part of the current loop, making it a 00167 // sibling to the current loop. We have to reparent this loop. 00168 if (Loop *SubLoop = const_cast<Loop*>(getLoopFor(X))) 00169 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)) { 00170 // Remove the subloop from it's current parent... 00171 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 00172 Loop *SLP = SubLoop->ParentLoop; // SubLoopParent 00173 std::vector<Loop*>::iterator I = 00174 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 00175 assert(I != SLP->SubLoops.end() && "SubLoop not a child of parent?"); 00176 SLP->SubLoops.erase(I); // Remove from parent... 00177 00178 // Add the subloop to THIS loop... 00179 SubLoop->ParentLoop = L; 00180 L->SubLoops.push_back(SubLoop); 00181 } 00182 00183 // Normal case, add the block to our loop... 00184 L->Blocks.push_back(X); 00185 00186 // Add all of the predecessors of X to the end of the work stack... 00187 TodoStack.insert(TodoStack.end(), pred_begin(X), pred_end(X)); 00188 } 00189 } 00190 00191 // If there are any loops nested within this loop, create them now! 00192 for (std::vector<BasicBlock*>::iterator I = L->Blocks.begin(), 00193 E = L->Blocks.end(); I != E; ++I) 00194 if (Loop *NewLoop = ConsiderForLoop(*I, EF)) { 00195 L->SubLoops.push_back(NewLoop); 00196 NewLoop->ParentLoop = L; 00197 } 00198 00199 // Add the basic blocks that comprise this loop to the BBMap so that this 00200 // loop can be found for them. 00201 // 00202 for (std::vector<BasicBlock*>::iterator I = L->Blocks.begin(), 00203 E = L->Blocks.end(); I != E; ++I) { 00204 std::map<BasicBlock*, Loop*>::iterator BBMI = BBMap.lower_bound(*I); 00205 if (BBMI == BBMap.end() || BBMI->first != *I) // Not in map yet... 00206 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level 00207 } 00208 00209 // Now that we have a list of all of the child loops of this loop, check to 00210 // see if any of them should actually be nested inside of each other. We can 00211 // accidentally pull loops our of their parents, so we must make sure to 00212 // organize the loop nests correctly now. 00213 { 00214 std::map<BasicBlock*, Loop*> ContainingLoops; 00215 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 00216 Loop *Child = L->SubLoops[i]; 00217 assert(Child->getParentLoop() == L && "Not proper child loop?"); 00218 00219 if (Loop *ContainingLoop = ContainingLoops[Child->getHeader()]) { 00220 // If there is already a loop which contains this loop, move this loop 00221 // into the containing loop. 00222 MoveSiblingLoopInto(Child, ContainingLoop); 00223 --i; // The loop got removed from the SubLoops list. 00224 } else { 00225 // This is currently considered to be a top-level loop. Check to see if 00226 // any of the contained blocks are loop headers for subloops we have 00227 // already processed. 00228 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 00229 Loop *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 00230 if (BlockLoop == 0) { // Child block not processed yet... 00231 BlockLoop = Child; 00232 } else if (BlockLoop != Child) { 00233 Loop *SubLoop = BlockLoop; 00234 // Reparent all of the blocks which used to belong to BlockLoops 00235 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 00236 ContainingLoops[SubLoop->Blocks[j]] = Child; 00237 00238 // There is already a loop which contains this block, that means 00239 // that we should reparent the loop which the block is currently 00240 // considered to belong to to be a child of this loop. 00241 MoveSiblingLoopInto(SubLoop, Child); 00242 --i; // We just shrunk the SubLoops list. 00243 } 00244 } 00245 } 00246 } 00247 } 00248 00249 return L; 00250 } 00251 00252 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside of 00253 /// the NewParent Loop, instead of being a sibling of it. 00254 void LoopInfo::MoveSiblingLoopInto(Loop *NewChild, Loop *NewParent) { 00255 Loop *OldParent = NewChild->getParentLoop(); 00256 assert(OldParent && OldParent == NewParent->getParentLoop() && 00257 NewChild != NewParent && "Not sibling loops!"); 00258 00259 // Remove NewChild from being a child of OldParent 00260 std::vector<Loop*>::iterator I = 00261 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), NewChild); 00262 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 00263 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 00264 NewChild->ParentLoop = 0; 00265 00266 InsertLoopInto(NewChild, NewParent); 00267 } 00268 00269 /// InsertLoopInto - This inserts loop L into the specified parent loop. If the 00270 /// parent loop contains a loop which should contain L, the loop gets inserted 00271 /// into L instead. 00272 void LoopInfo::InsertLoopInto(Loop *L, Loop *Parent) { 00273 BasicBlock *LHeader = L->getHeader(); 00274 assert(Parent->contains(LHeader) && "This loop should not be inserted here!"); 00275 00276 // Check to see if it belongs in a child loop... 00277 for (unsigned i = 0, e = Parent->SubLoops.size(); i != e; ++i) 00278 if (Parent->SubLoops[i]->contains(LHeader)) { 00279 InsertLoopInto(L, Parent->SubLoops[i]); 00280 return; 00281 } 00282 00283 // If not, insert it here! 00284 Parent->SubLoops.push_back(L); 00285 L->ParentLoop = Parent; 00286 } 00287 00288 /// changeLoopFor - Change the top-level loop that contains BB to the 00289 /// specified loop. This should be used by transformations that restructure 00290 /// the loop hierarchy tree. 00291 void LoopInfo::changeLoopFor(BasicBlock *BB, Loop *L) { 00292 Loop *&OldLoop = BBMap[BB]; 00293 assert(OldLoop && "Block not in a loop yet!"); 00294 OldLoop = L; 00295 } 00296 00297 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 00298 /// list with the indicated loop. 00299 void LoopInfo::changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 00300 std::vector<Loop*>::iterator I = std::find(TopLevelLoops.begin(), 00301 TopLevelLoops.end(), OldLoop); 00302 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 00303 *I = NewLoop; 00304 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 00305 "Loops already embedded into a subloop!"); 00306 } 00307 00308 /// removeLoop - This removes the specified top-level loop from this loop info 00309 /// object. The loop is not deleted, as it will presumably be inserted into 00310 /// another loop. 00311 Loop *LoopInfo::removeLoop(iterator I) { 00312 assert(I != end() && "Cannot remove end iterator!"); 00313 Loop *L = *I; 00314 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 00315 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 00316 return L; 00317 } 00318 00319 /// removeBlock - This method completely removes BB from all data structures, 00320 /// including all of the Loop objects it is nested in and our mapping from 00321 /// BasicBlocks to loops. 00322 void LoopInfo::removeBlock(BasicBlock *BB) { 00323 std::map<BasicBlock *, Loop*>::iterator I = BBMap.find(BB); 00324 if (I != BBMap.end()) { 00325 for (Loop *L = I->second; L; L = L->getParentLoop()) 00326 L->removeBlockFromLoop(BB); 00327 00328 BBMap.erase(I); 00329 } 00330 } 00331 00332 00333 //===----------------------------------------------------------------------===// 00334 // APIs for simple analysis of the loop. 00335 // 00336 00337 /// getExitBlocks - Return all of the successor blocks of this loop. These 00338 /// are the blocks _outside of the current loop_ which are branched to. 00339 /// 00340 void Loop::getExitBlocks(std::vector<BasicBlock*> &ExitBlocks) const { 00341 for (std::vector<BasicBlock*>::const_iterator BI = Blocks.begin(), 00342 BE = Blocks.end(); BI != BE; ++BI) 00343 for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I) 00344 if (!contains(*I)) // Not in current loop? 00345 ExitBlocks.push_back(*I); // It must be an exit block... 00346 } 00347 00348 00349 /// getLoopPreheader - If there is a preheader for this loop, return it. A 00350 /// loop has a preheader if there is only one edge to the header of the loop 00351 /// from outside of the loop. If this is the case, the block branching to the 00352 /// header of the loop is the preheader node. 00353 /// 00354 /// This method returns null if there is no preheader for the loop. 00355 /// 00356 BasicBlock *Loop::getLoopPreheader() const { 00357 // Keep track of nodes outside the loop branching to the header... 00358 BasicBlock *Out = 0; 00359 00360 // Loop over the predecessors of the header node... 00361 BasicBlock *Header = getHeader(); 00362 for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header); 00363 PI != PE; ++PI) 00364 if (!contains(*PI)) { // If the block is not in the loop... 00365 if (Out && Out != *PI) 00366 return 0; // Multiple predecessors outside the loop 00367 Out = *PI; 00368 } 00369 00370 // Make sure there is only one exit out of the preheader. 00371 assert(Out && "Header of loop has no predecessors from outside loop?"); 00372 succ_iterator SI = succ_begin(Out); 00373 ++SI; 00374 if (SI != succ_end(Out)) 00375 return 0; // Multiple exits from the block, must not be a preheader. 00376 00377 // If there is exactly one preheader, return it. If there was zero, then Out 00378 // is still null. 00379 return Out; 00380 } 00381 00382 /// getLoopLatch - If there is a latch block for this loop, return it. A 00383 /// latch block is the canonical backedge for a loop. A loop header in normal 00384 /// form has two edges into it: one from a preheader and one from a latch 00385 /// block. 00386 BasicBlock *Loop::getLoopLatch() const { 00387 BasicBlock *Header = getHeader(); 00388 pred_iterator PI = pred_begin(Header), PE = pred_end(Header); 00389 if (PI == PE) return 0; // no preds? 00390 00391 BasicBlock *Latch = 0; 00392 if (contains(*PI)) 00393 Latch = *PI; 00394 ++PI; 00395 if (PI == PE) return 0; // only one pred? 00396 00397 if (contains(*PI)) { 00398 if (Latch) return 0; // multiple backedges 00399 Latch = *PI; 00400 } 00401 ++PI; 00402 if (PI != PE) return 0; // more than two preds 00403 00404 return Latch; 00405 } 00406 00407 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 00408 /// induction variable: an integer recurrence that starts at 0 and increments by 00409 /// one each time through the loop. If so, return the phi node that corresponds 00410 /// to it. 00411 /// 00412 PHINode *Loop::getCanonicalInductionVariable() const { 00413 BasicBlock *H = getHeader(); 00414 00415 BasicBlock *Incoming = 0, *Backedge = 0; 00416 pred_iterator PI = pred_begin(H); 00417 assert(PI != pred_end(H) && "Loop must have at least one backedge!"); 00418 Backedge = *PI++; 00419 if (PI == pred_end(H)) return 0; // dead loop 00420 Incoming = *PI++; 00421 if (PI != pred_end(H)) return 0; // multiple backedges? 00422 00423 if (contains(Incoming)) { 00424 if (contains(Backedge)) 00425 return 0; 00426 std::swap(Incoming, Backedge); 00427 } else if (!contains(Backedge)) 00428 return 0; 00429 00430 // Loop over all of the PHI nodes, looking for a canonical indvar. 00431 for (BasicBlock::iterator I = H->begin(); isa<PHINode>(I); ++I) { 00432 PHINode *PN = cast<PHINode>(I); 00433 if (Instruction *Inc = 00434 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge))) 00435 if (Inc->getOpcode() == Instruction::Add && Inc->getOperand(0) == PN) 00436 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1))) 00437 if (CI->equalsInt(1)) 00438 return PN; 00439 } 00440 return 0; 00441 } 00442 00443 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 00444 /// the canonical induction variable value for the "next" iteration of the loop. 00445 /// This always succeeds if getCanonicalInductionVariable succeeds. 00446 /// 00447 Instruction *Loop::getCanonicalInductionVariableIncrement() const { 00448 if (PHINode *PN = getCanonicalInductionVariable()) { 00449 bool P1InLoop = contains(PN->getIncomingBlock(1)); 00450 return cast<Instruction>(PN->getIncomingValue(P1InLoop)); 00451 } 00452 return 0; 00453 } 00454 00455 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 00456 /// times the loop will be executed. Note that this means that the backedge of 00457 /// the loop executes N-1 times. If the trip-count cannot be determined, this 00458 /// returns null. 00459 /// 00460 Value *Loop::getTripCount() const { 00461 // Canonical loops will end with a 'setne I, V', where I is the incremented 00462 // canonical induction variable and V is the trip count of the loop. 00463 Instruction *Inc = getCanonicalInductionVariableIncrement(); 00464 if (Inc == 0) return 0; 00465 PHINode *IV = cast<PHINode>(Inc->getOperand(0)); 00466 00467 BasicBlock *BackedgeBlock = 00468 IV->getIncomingBlock(contains(IV->getIncomingBlock(1))); 00469 00470 if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator())) 00471 if (BI->isConditional()) 00472 if (SetCondInst *SCI = dyn_cast<SetCondInst>(BI->getCondition())) 00473 if (SCI->getOperand(0) == Inc) 00474 if (BI->getSuccessor(0) == getHeader()) { 00475 if (SCI->getOpcode() == Instruction::SetNE) 00476 return SCI->getOperand(1); 00477 } else if (SCI->getOpcode() == Instruction::SetEQ) { 00478 return SCI->getOperand(1); 00479 } 00480 00481 return 0; 00482 } 00483 00484 00485 //===-------------------------------------------------------------------===// 00486 // APIs for updating loop information after changing the CFG 00487 // 00488 00489 /// addBasicBlockToLoop - This function is used by other analyses to update loop 00490 /// information. NewBB is set to be a new member of the current loop. Because 00491 /// of this, it is added as a member of all parent loops, and is added to the 00492 /// specified LoopInfo object as being in the current basic block. It is not 00493 /// valid to replace the loop header with this method. 00494 /// 00495 void Loop::addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI) { 00496 assert((Blocks.empty() || LI[getHeader()] == this) && 00497 "Incorrect LI specified for this loop!"); 00498 assert(NewBB && "Cannot add a null basic block to the loop!"); 00499 assert(LI[NewBB] == 0 && "BasicBlock already in the loop!"); 00500 00501 // Add the loop mapping to the LoopInfo object... 00502 LI.BBMap[NewBB] = this; 00503 00504 // Add the basic block to this loop and all parent loops... 00505 Loop *L = this; 00506 while (L) { 00507 L->Blocks.push_back(NewBB); 00508 L = L->getParentLoop(); 00509 } 00510 } 00511 00512 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 00513 /// the OldChild entry in our children list with NewChild, and updates the 00514 /// parent pointers of the two loops as appropriate. 00515 void Loop::replaceChildLoopWith(Loop *OldChild, Loop *NewChild) { 00516 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 00517 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 00518 std::vector<Loop*>::iterator I = std::find(SubLoops.begin(), SubLoops.end(), 00519 OldChild); 00520 assert(I != SubLoops.end() && "OldChild not in loop!"); 00521 *I = NewChild; 00522 OldChild->ParentLoop = 0; 00523 NewChild->ParentLoop = this; 00524 } 00525 00526 /// addChildLoop - Add the specified loop to be a child of this loop. 00527 /// 00528 void Loop::addChildLoop(Loop *NewChild) { 00529 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 00530 NewChild->ParentLoop = this; 00531 SubLoops.push_back(NewChild); 00532 } 00533 00534 template<typename T> 00535 static void RemoveFromVector(std::vector<T*> &V, T *N) { 00536 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); 00537 assert(I != V.end() && "N is not in this list!"); 00538 V.erase(I); 00539 } 00540 00541 /// removeChildLoop - This removes the specified child from being a subloop of 00542 /// this loop. The loop is not deleted, as it will presumably be inserted 00543 /// into another loop. 00544 Loop *Loop::removeChildLoop(iterator I) { 00545 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 00546 Loop *Child = *I; 00547 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 00548 SubLoops.erase(SubLoops.begin()+(I-begin())); 00549 Child->ParentLoop = 0; 00550 return Child; 00551 } 00552 00553 00554 /// removeBlockFromLoop - This removes the specified basic block from the 00555 /// current loop, updating the Blocks and ExitBlocks lists as appropriate. This 00556 /// does not update the mapping in the LoopInfo class. 00557 void Loop::removeBlockFromLoop(BasicBlock *BB) { 00558 RemoveFromVector(Blocks, BB); 00559 }