X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FLoopInfo.cpp;h=131d02a32b8c10633eeb5739413b681f40da68a1;hb=0e872cb4707cbfc260279132e290ed595e47d2cd;hp=497732b9586eec1565fee35b87a82009b3efe070;hpb=420df9bc781eb4d37e95f6394ccebf5952b15878;p=oota-llvm.git diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp index 497732b9586..131d02a32b8 100644 --- a/lib/Analysis/LoopInfo.cpp +++ b/lib/Analysis/LoopInfo.cpp @@ -1,4 +1,11 @@ -//===- LoopInfo.cpp - Natural Loop Calculator -------------------------------=// +//===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file was developed by the LLVM research group and is distributed under +// the University of Illinois Open Source License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// // // This file defines the LoopInfo class that is used to identify natural loops // and determine the loop depth of various nodes of the CFG. Note that the @@ -8,11 +15,16 @@ //===----------------------------------------------------------------------===// #include "llvm/Analysis/LoopInfo.h" +#include "llvm/Constants.h" +#include "llvm/Instructions.h" #include "llvm/Analysis/Dominators.h" -#include "llvm/Support/CFG.h" #include "llvm/Assembly/Writer.h" +#include "llvm/Support/CFG.h" #include "Support/DepthFirstIterator.h" #include +#include + +using namespace llvm; static RegisterAnalysis X("loops", "Natural Loop Construction", true); @@ -25,39 +37,50 @@ bool Loop::contains(const BasicBlock *BB) const { } bool Loop::isLoopExit(const BasicBlock *BB) const { - for (BasicBlock::succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB); + for (succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI) { - if (! contains(*SI)) + if (!contains(*SI)) return true; } return false; } +/// getNumBackEdges - Calculate the number of back edges to the loop header. +/// unsigned Loop::getNumBackEdges() const { - unsigned numBackEdges = 0; - BasicBlock *header = Blocks.front(); - - for (std::vector::const_iterator I = Blocks.begin(), - E = Blocks.end(); I != E; ++I) { - for (BasicBlock::succ_iterator SI = succ_begin(*I), SE = succ_end(*I); - SI != SE; ++SI) - if (header == *SI) - ++numBackEdges; - } - return numBackEdges; + unsigned NumBackEdges = 0; + BasicBlock *H = getHeader(); + + for (pred_iterator I = pred_begin(H), E = pred_end(H); I != E; ++I) + if (contains(*I)) + ++NumBackEdges; + + return NumBackEdges; } -void Loop::print(std::ostream &OS) const { - OS << std::string(getLoopDepth()*2, ' ') << "Loop Containing: "; +/// isLoopInvariant - Return true if the specified value is loop invariant +/// +bool Loop::isLoopInvariant(Value *V) const { + if (Instruction *I = dyn_cast(V)) + return !contains(I->getParent()); + return true; // All non-instructions are loop invariant +} + +void Loop::print(std::ostream &OS, unsigned Depth) const { + OS << std::string(Depth*2, ' ') << "Loop Containing: "; for (unsigned i = 0; i < getBlocks().size(); ++i) { if (i) OS << ","; - WriteAsOperand(OS, (const Value*)getBlocks()[i]); + WriteAsOperand(OS, getBlocks()[i], false); } OS << "\n"; - for (unsigned i = 0, e = getSubLoops().size(); i != e; ++i) - getSubLoops()[i]->print(OS); + for (iterator I = begin(), E = end(); I != E; ++I) + (*I)->print(OS, Depth+2); +} + +void Loop::dump() const { + print(std::cerr); } @@ -89,9 +112,6 @@ void LoopInfo::Calculate(const DominatorSet &DS) { NE = df_end(RootNode); NI != NE; ++NI) if (Loop *L = ConsiderForLoop(*NI, DS)) TopLevelLoops.push_back(L); - - for (unsigned i = 0; i < TopLevelLoops.size(); ++i) - TopLevelLoops[i]->setLoopDepth(1); } void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const { @@ -106,34 +126,64 @@ void LoopInfo::print(std::ostream &OS) const { for (std::map::const_iterator I = BBMap.begin(), E = BBMap.end(); I != E; ++I) OS << "BB '" << I->first->getName() << "' level = " - << I->second->LoopDepth << "\n"; + << I->second->getLoopDepth() << "\n"; #endif } +static bool isNotAlreadyContainedIn(Loop *SubLoop, Loop *ParentLoop) { + if (SubLoop == 0) return true; + if (SubLoop == ParentLoop) return false; + return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); +} + Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) { if (BBMap.find(BB) != BBMap.end()) return 0; // Haven't processed this node? std::vector TodoStack; // Scan the predecessors of BB, checking to see if BB dominates any of - // them. + // them. This identifies backedges which target this node... for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I) if (DS.dominates(BB, *I)) // If BB dominates it's predecessor... TodoStack.push_back(*I); - if (TodoStack.empty()) return 0; // Doesn't dominate any predecessors... + if (TodoStack.empty()) return 0; // No backedges to this block... // Create a new loop to represent this basic block... Loop *L = new Loop(BB); BBMap[BB] = L; + BasicBlock *EntryBlock = &BB->getParent()->getEntryBlock(); + while (!TodoStack.empty()) { // Process all the nodes in the loop BasicBlock *X = TodoStack.back(); TodoStack.pop_back(); - if (!L->contains(X)) { // As of yet unprocessed?? + if (!L->contains(X) && // As of yet unprocessed?? + DS.dominates(EntryBlock, X)) { // X is reachable from entry block? + // Check to see if this block already belongs to a loop. If this occurs + // then we have a case where a loop that is supposed to be a child of the + // current loop was processed before the current loop. When this occurs, + // this child loop gets added to a part of the current loop, making it a + // sibling to the current loop. We have to reparent this loop. + if (Loop *SubLoop = const_cast(getLoopFor(X))) + if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)) { + // Remove the subloop from it's current parent... + assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); + Loop *SLP = SubLoop->ParentLoop; // SubLoopParent + std::vector::iterator I = + std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); + assert(I != SLP->SubLoops.end() && "SubLoop not a child of parent?"); + SLP->SubLoops.erase(I); // Remove from parent... + + // Add the subloop to THIS loop... + SubLoop->ParentLoop = L; + L->SubLoops.push_back(SubLoop); + } + + // Normal case, add the block to our loop... L->Blocks.push_back(X); - + // Add all of the predecessors of X to the end of the work stack... TodoStack.insert(TodoStack.end(), pred_begin(X), pred_end(X)); } @@ -147,7 +197,6 @@ Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) { NewLoop->ParentLoop = L; } - // Add the basic blocks that comprise this loop to the BBMap so that this // loop can be found for them. // @@ -158,18 +207,152 @@ Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) { BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level } + // Now that we have a list of all of the child loops of this loop, check to + // see if any of them should actually be nested inside of each other. We can + // accidentally pull loops our of their parents, so we must make sure to + // organize the loop nests correctly now. + { + std::map ContainingLoops; + for (unsigned i = 0; i != L->SubLoops.size(); ++i) { + Loop *Child = L->SubLoops[i]; + assert(Child->getParentLoop() == L && "Not proper child loop?"); + + if (Loop *ContainingLoop = ContainingLoops[Child->getHeader()]) { + // If there is already a loop which contains this loop, move this loop + // into the containing loop. + MoveSiblingLoopInto(Child, ContainingLoop); + --i; // The loop got removed from the SubLoops list. + } else { + // This is currently considered to be a top-level loop. Check to see if + // any of the contained blocks are loop headers for subloops we have + // already processed. + for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { + Loop *&BlockLoop = ContainingLoops[Child->Blocks[b]]; + if (BlockLoop == 0) { // Child block not processed yet... + BlockLoop = Child; + } else if (BlockLoop != Child) { + Loop *SubLoop = BlockLoop; + // Reparent all of the blocks which used to belong to BlockLoops + for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) + ContainingLoops[SubLoop->Blocks[j]] = Child; + + // There is already a loop which contains this block, that means + // that we should reparent the loop which the block is currently + // considered to belong to to be a child of this loop. + MoveSiblingLoopInto(SubLoop, Child); + --i; // We just shrunk the SubLoops list. + } + } + } + } + } + + return L; +} + +/// MoveSiblingLoopInto - This method moves the NewChild loop to live inside of +/// the NewParent Loop, instead of being a sibling of it. +void LoopInfo::MoveSiblingLoopInto(Loop *NewChild, Loop *NewParent) { + Loop *OldParent = NewChild->getParentLoop(); + assert(OldParent && OldParent == NewParent->getParentLoop() && + NewChild != NewParent && "Not sibling loops!"); + + // Remove NewChild from being a child of OldParent + std::vector::iterator I = + std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), NewChild); + assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); + OldParent->SubLoops.erase(I); // Remove from parent's subloops list + NewChild->ParentLoop = 0; + + InsertLoopInto(NewChild, NewParent); +} + +/// InsertLoopInto - This inserts loop L into the specified parent loop. If the +/// parent loop contains a loop which should contain L, the loop gets inserted +/// into L instead. +void LoopInfo::InsertLoopInto(Loop *L, Loop *Parent) { + BasicBlock *LHeader = L->getHeader(); + assert(Parent->contains(LHeader) && "This loop should not be inserted here!"); + + // Check to see if it belongs in a child loop... + for (unsigned i = 0, e = Parent->SubLoops.size(); i != e; ++i) + if (Parent->SubLoops[i]->contains(LHeader)) { + InsertLoopInto(L, Parent->SubLoops[i]); + return; + } + + // If not, insert it here! + Parent->SubLoops.push_back(L); + L->ParentLoop = Parent; +} + +/// changeLoopFor - Change the top-level loop that contains BB to the +/// specified loop. This should be used by transformations that restructure +/// the loop hierarchy tree. +void LoopInfo::changeLoopFor(BasicBlock *BB, Loop *L) { + Loop *&OldLoop = BBMap[BB]; + assert(OldLoop && "Block not in a loop yet!"); + OldLoop = L; +} + +/// changeTopLevelLoop - Replace the specified loop in the top-level loops +/// list with the indicated loop. +void LoopInfo::changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { + std::vector::iterator I = std::find(TopLevelLoops.begin(), + TopLevelLoops.end(), OldLoop); + assert(I != TopLevelLoops.end() && "Old loop not at top level!"); + *I = NewLoop; + assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && + "Loops already embedded into a subloop!"); +} + +/// removeLoop - This removes the specified top-level loop from this loop info +/// object. The loop is not deleted, as it will presumably be inserted into +/// another loop. +Loop *LoopInfo::removeLoop(iterator I) { + assert(I != end() && "Cannot remove end iterator!"); + Loop *L = *I; + assert(L->getParentLoop() == 0 && "Not a top-level loop!"); + TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); return L; } +/// removeBlock - This method completely removes BB from all data structures, +/// including all of the Loop objects it is nested in and our mapping from +/// BasicBlocks to loops. +void LoopInfo::removeBlock(BasicBlock *BB) { + std::map::iterator I = BBMap.find(BB); + if (I != BBMap.end()) { + for (Loop *L = I->second; L; L = L->getParentLoop()) + L->removeBlockFromLoop(BB); + + BBMap.erase(I); + } +} + + +//===----------------------------------------------------------------------===// +// APIs for simple analysis of the loop. +// + +/// getExitBlocks - Return all of the successor blocks of this loop. These +/// are the blocks _outside of the current loop_ which are branched to. +/// +void Loop::getExitBlocks(std::vector &ExitBlocks) const { + for (std::vector::const_iterator BI = Blocks.begin(), + BE = Blocks.end(); BI != BE; ++BI) + for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I) + if (!contains(*I)) // Not in current loop? + ExitBlocks.push_back(*I); // It must be an exit block... +} + + /// getLoopPreheader - If there is a preheader for this loop, return it. A /// loop has a preheader if there is only one edge to the header of the loop /// from outside of the loop. If this is the case, the block branching to the -/// header of the loop is the preheader node. The "preheaders" pass can be -/// "Required" to ensure that there is always a preheader node for every loop. +/// header of the loop is the preheader node. /// -/// This method returns null if there is no preheader for the loop (either -/// because the loop is dead or because multiple blocks branch to the header -/// node of this loop). +/// This method returns null if there is no preheader for the loop. /// BasicBlock *Loop::getLoopPreheader() const { // Keep track of nodes outside the loop branching to the header... @@ -184,12 +367,101 @@ BasicBlock *Loop::getLoopPreheader() const { return 0; // Multiple predecessors outside the loop Out = *PI; } + + // Make sure there is only one exit out of the preheader... + succ_iterator SI = succ_begin(Out); + ++SI; + if (SI != succ_end(Out)) + return 0; // Multiple exits from the block, must not be a preheader. + // If there is exactly one preheader, return it. If there was zero, then Out // is still null. return Out; } +/// getCanonicalInductionVariable - Check to see if the loop has a canonical +/// induction variable: an integer recurrence that starts at 0 and increments by +/// one each time through the loop. If so, return the phi node that corresponds +/// to it. +/// +PHINode *Loop::getCanonicalInductionVariable() const { + BasicBlock *H = getHeader(); + + BasicBlock *Incoming = 0, *Backedge = 0; + pred_iterator PI = pred_begin(H); + assert(PI != pred_end(H) && "Loop must have at least one backedge!"); + Backedge = *PI++; + if (PI == pred_end(H)) return 0; // dead loop + Incoming = *PI++; + if (PI != pred_end(H)) return 0; // multiple backedges? + + if (contains(Incoming)) { + if (contains(Backedge)) + return 0; + std::swap(Incoming, Backedge); + } else if (!contains(Backedge)) + return 0; + + // Loop over all of the PHI nodes, looking for a canonical indvar. + for (BasicBlock::iterator I = H->begin(); + PHINode *PN = dyn_cast(I); ++I) + if (Instruction *Inc = + dyn_cast(PN->getIncomingValueForBlock(Backedge))) + if (Inc->getOpcode() == Instruction::Add && Inc->getOperand(0) == PN) + if (ConstantInt *CI = dyn_cast(Inc->getOperand(1))) + if (CI->equalsInt(1)) + return PN; + + return 0; +} + +/// getCanonicalInductionVariableIncrement - Return the LLVM value that holds +/// the canonical induction variable value for the "next" iteration of the loop. +/// This always succeeds if getCanonicalInductionVariable succeeds. +/// +Instruction *Loop::getCanonicalInductionVariableIncrement() const { + if (PHINode *PN = getCanonicalInductionVariable()) { + bool P1InLoop = contains(PN->getIncomingBlock(1)); + return cast(PN->getIncomingValue(P1InLoop)); + } + return 0; +} + +/// getTripCount - Return a loop-invariant LLVM value indicating the number of +/// times the loop will be executed. Note that this means that the backedge of +/// the loop executes N-1 times. If the trip-count cannot be determined, this +/// returns null. +/// +Value *Loop::getTripCount() const { + // Canonical loops will end with a 'setne I, V', where I is the incremented + // canonical induction variable and V is the trip count of the loop. + Instruction *Inc = getCanonicalInductionVariableIncrement(); + if (Inc == 0) return 0; + PHINode *IV = cast(Inc->getOperand(0)); + + BasicBlock *BackedgeBlock = + IV->getIncomingBlock(contains(IV->getIncomingBlock(1))); + + if (BranchInst *BI = dyn_cast(BackedgeBlock->getTerminator())) + if (BI->isConditional()) + if (SetCondInst *SCI = dyn_cast(BI->getCondition())) + if (SCI->getOperand(0) == Inc) + if (BI->getSuccessor(0) == getHeader()) { + if (SCI->getOpcode() == Instruction::SetNE) + return SCI->getOperand(1); + } else if (SCI->getOpcode() == Instruction::SetEQ) { + return SCI->getOperand(1); + } + + return 0; +} + + +//===-------------------------------------------------------------------===// +// APIs for updating loop information after changing the CFG +// + /// addBasicBlockToLoop - This function is used by other analyses to update loop /// information. NewBB is set to be a new member of the current loop. Because /// of this, it is added as a member of all parent loops, and is added to the @@ -197,7 +469,8 @@ BasicBlock *Loop::getLoopPreheader() const { /// valid to replace the loop header with this method. /// void Loop::addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI) { - assert(LI[getHeader()] == this && "Incorrect LI specified for this loop!"); + assert((Blocks.empty() || LI[getHeader()] == this) && + "Incorrect LI specified for this loop!"); assert(NewBB && "Cannot add a null basic block to the loop!"); assert(LI[NewBB] == 0 && "BasicBlock already in the loop!"); @@ -211,3 +484,52 @@ void Loop::addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI) { L = L->getParentLoop(); } } + +/// replaceChildLoopWith - This is used when splitting loops up. It replaces +/// the OldChild entry in our children list with NewChild, and updates the +/// parent pointers of the two loops as appropriate. +void Loop::replaceChildLoopWith(Loop *OldChild, Loop *NewChild) { + assert(OldChild->ParentLoop == this && "This loop is already broken!"); + assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); + std::vector::iterator I = std::find(SubLoops.begin(), SubLoops.end(), + OldChild); + assert(I != SubLoops.end() && "OldChild not in loop!"); + *I = NewChild; + OldChild->ParentLoop = 0; + NewChild->ParentLoop = this; +} + +/// addChildLoop - Add the specified loop to be a child of this loop. +/// +void Loop::addChildLoop(Loop *NewChild) { + assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); + NewChild->ParentLoop = this; + SubLoops.push_back(NewChild); +} + +template +static void RemoveFromVector(std::vector &V, T *N) { + typename std::vector::iterator I = std::find(V.begin(), V.end(), N); + assert(I != V.end() && "N is not in this list!"); + V.erase(I); +} + +/// removeChildLoop - This removes the specified child from being a subloop of +/// this loop. The loop is not deleted, as it will presumably be inserted +/// into another loop. +Loop *Loop::removeChildLoop(iterator I) { + assert(I != SubLoops.end() && "Cannot remove end iterator!"); + Loop *Child = *I; + assert(Child->ParentLoop == this && "Child is not a child of this loop!"); + SubLoops.erase(SubLoops.begin()+(I-begin())); + Child->ParentLoop = 0; + return Child; +} + + +/// removeBlockFromLoop - This removes the specified basic block from the +/// current loop, updating the Blocks and ExitBlocks lists as appropriate. This +/// does not update the mapping in the LoopInfo class. +void Loop::removeBlockFromLoop(BasicBlock *BB) { + RemoveFromVector(Blocks, BB); +}