X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FLoopInfo.cpp;h=7a1daa089e28361ebe3cc7ada275b876f6a64d5a;hb=c53544af06acf3fba1788613a364f1f40317869e;hp=cd7768f1823428036964e083c8aae29425f35344;hpb=b7653df0853f06112b741be09f1b7ae5a6aa6fde;p=oota-llvm.git diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp index cd7768f1823..7a1daa089e2 100644 --- a/lib/Analysis/LoopInfo.cpp +++ b/lib/Analysis/LoopInfo.cpp @@ -10,33 +10,94 @@ #include "llvm/Analysis/LoopInfo.h" #include "llvm/Analysis/Dominators.h" #include "llvm/Support/CFG.h" +#include "llvm/Assembly/Writer.h" #include "Support/DepthFirstIterator.h" #include -AnalysisID cfg::LoopInfo::ID(AnalysisID::create()); +static RegisterAnalysis +X("loops", "Natural Loop Construction", true); //===----------------------------------------------------------------------===// -// cfg::Loop implementation +// Loop implementation // -bool cfg::Loop::contains(const BasicBlock *BB) const { +bool Loop::contains(const BasicBlock *BB) const { return find(Blocks.begin(), Blocks.end(), BB) != Blocks.end(); } +bool Loop::isLoopExit(const BasicBlock *BB) const { + for (BasicBlock::succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB); + SI != SE; ++SI) { + if (!contains(*SI)) + return true; + } + return false; +} + +unsigned Loop::getNumBackEdges() const { + unsigned NumBackEdges = 0; + BasicBlock *H = getHeader(); + + 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 (*SI == H) + ++NumBackEdges; + + return NumBackEdges; +} + +void Loop::print(std::ostream &OS) const { + OS << std::string(getLoopDepth()*2, ' ') << "Loop Containing: "; + + for (unsigned i = 0; i < getBlocks().size(); ++i) { + if (i) OS << ","; + WriteAsOperand(OS, getBlocks()[i], false); + } + if (!ExitBlocks.empty()) { + OS << "\tExitBlocks: "; + for (unsigned i = 0; i < getExitBlocks().size(); ++i) { + if (i) OS << ","; + WriteAsOperand(OS, getExitBlocks()[i], false); + } + } + + OS << "\n"; + + for (unsigned i = 0, e = getSubLoops().size(); i != e; ++i) + getSubLoops()[i]->print(OS); +} + +void Loop::dump() const { + print(std::cerr); +} + //===----------------------------------------------------------------------===// -// cfg::LoopInfo implementation +// LoopInfo implementation // -bool cfg::LoopInfo::runOnMethod(Function *F) { - BBMap.clear(); // Reset internal state of analysis - TopLevelLoops.clear(); +void LoopInfo::stub() {} + +bool LoopInfo::runOnFunction(Function &) { + releaseMemory(); Calculate(getAnalysis()); // Update return false; } -void cfg::LoopInfo::Calculate(const DominatorSet &DS) { - const BasicBlock *RootNode = DS.getRoot(); +void LoopInfo::releaseMemory() { + for (std::vector::iterator I = TopLevelLoops.begin(), + E = TopLevelLoops.end(); I != E; ++I) + delete *I; // Delete all of the loops... - for (df_iterator NI = df_begin(RootNode), + BBMap.clear(); // Reset internal state of analysis + TopLevelLoops.clear(); +} + + +void LoopInfo::Calculate(const DominatorSet &DS) { + BasicBlock *RootNode = DS.getRoot(); + + for (df_iterator NI = df_begin(RootNode), NE = df_end(RootNode); NI != NE; ++NI) if (Loop *L = ConsiderForLoop(*NI, DS)) TopLevelLoops.push_back(L); @@ -45,60 +106,172 @@ void cfg::LoopInfo::Calculate(const DominatorSet &DS) { TopLevelLoops[i]->setLoopDepth(1); } -void cfg::LoopInfo::getAnalysisUsageInfo(Pass::AnalysisSet &Required, - Pass::AnalysisSet &Destroyed, - Pass::AnalysisSet &Provided) { - Required.push_back(DominatorSet::ID); - Provided.push_back(ID); +void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const { + AU.setPreservesAll(); + AU.addRequired(); } +void LoopInfo::print(std::ostream &OS) const { + for (unsigned i = 0; i < TopLevelLoops.size(); ++i) + TopLevelLoops[i]->print(OS); +#if 0 + for (std::map::const_iterator I = BBMap.begin(), + E = BBMap.end(); I != E; ++I) + OS << "BB '" << I->first->getName() << "' level = " + << I->second->LoopDepth << "\n"; +#endif +} -cfg::Loop *cfg::LoopInfo::ConsiderForLoop(const BasicBlock *BB, - const DominatorSet &DS) { - if (BBMap.find(BB) != BBMap.end()) return 0; // Havn't processed this node? +Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) { + if (BBMap.find(BB) != BBMap.end()) return 0; // Haven't processed this node? - std::vector TodoStack; + std::vector TodoStack; // Scan the predecessors of BB, checking to see if BB dominates any of - // them. - for (pred_const_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I) + // 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; while (!TodoStack.empty()) { // Process all the nodes in the loop - const BasicBlock *X = TodoStack.back(); + BasicBlock *X = TodoStack.back(); TodoStack.pop_back(); - if (!L->contains(X)) { // As of yet unprocessed?? - L->Blocks.push_back(X); + if (!L->contains(X)) { // As of yet unprocessed?? + // 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 && X != BB) { + // 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)); } } - // Add the basic blocks that comprise this loop to the BBMap so that this - // loop can be found for them. Also check subsidary basic blocks to see if - // they start subloops of their own. - // - for (std::vector::reverse_iterator I = L->Blocks.rbegin(), - E = L->Blocks.rend(); I != E; ++I) { - - // Check to see if this block starts a new loop + // If there are any loops nested within this loop, create them now! + for (std::vector::iterator I = L->Blocks.begin(), + E = L->Blocks.end(); I != E; ++I) if (Loop *NewLoop = ConsiderForLoop(*I, DS)) { L->SubLoops.push_back(NewLoop); NewLoop->ParentLoop = L; } - - if (BBMap.find(*I) == BBMap.end()) - BBMap.insert(std::make_pair(*I, L)); + + + // Add the basic blocks that comprise this loop to the BBMap so that this + // loop can be found for them. + // + for (std::vector::iterator I = L->Blocks.begin(), + E = L->Blocks.end(); I != E; ++I) { + std::map::iterator BBMI = BBMap.lower_bound(*I); + if (BBMI == BBMap.end() || BBMI->first != *I) // Not in map yet... + BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level } + // Now that we know all of the blocks that make up this loop, see if there are + // any branches to outside of the loop... building the ExitBlocks list. + for (std::vector::iterator BI = L->Blocks.begin(), + BE = L->Blocks.end(); BI != BE; ++BI) + for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I) + if (!L->contains(*I)) // Not in current loop? + L->ExitBlocks.push_back(*I); // It must be an exit block... + return L; } + +/// 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. +/// +/// 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). +/// +BasicBlock *Loop::getLoopPreheader() const { + // Keep track of nodes outside the loop branching to the header... + BasicBlock *Out = 0; + + // Loop over the predecessors of the header node... + BasicBlock *Header = getHeader(); + for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header); + PI != PE; ++PI) + if (!contains(*PI)) { // If the block is not in the loop... + if (Out && Out != *PI) + 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; +} + +/// 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 +/// specified LoopInfo object as being in the current basic block. It is not +/// 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(NewBB && "Cannot add a null basic block to the loop!"); + assert(LI[NewBB] == 0 && "BasicBlock already in the loop!"); + + // Add the loop mapping to the LoopInfo object... + LI.BBMap[NewBB] = this; + + // Add the basic block to this loop and all parent loops... + Loop *L = this; + while (L) { + L->Blocks.push_back(NewBB); + L = L->getParentLoop(); + } +} + +/// changeExitBlock - This method is used to update loop information. All +/// instances of the specified Old basic block are removed from the exit list +/// and replaced with New. +/// +void Loop::changeExitBlock(BasicBlock *Old, BasicBlock *New) { + assert(Old != New && "Cannot changeExitBlock to the same thing!"); + assert(Old && New && "Cannot changeExitBlock to or from a null node!"); + assert(hasExitBlock(Old) && "Old exit block not found!"); + std::vector::iterator + I = std::find(ExitBlocks.begin(), ExitBlocks.end(), Old); + while (I != ExitBlocks.end()) { + *I = New; + I = std::find(I+1, ExitBlocks.end(), Old); + } +}