2001-11-26 18:41:20 +00:00
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//===- LoopInfo.cpp - Natural Loop Calculator -------------------------------=//
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//
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// This file defines the LoopInfo class that is used to identify natural loops
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// and determine the loop depth of various nodes of the CFG. Note that the
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// loops identified may actually be several natural loops that share the same
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// header node... not just a single natural loop.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/Dominators.h"
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2002-02-12 21:07:25 +00:00
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#include "llvm/Support/CFG.h"
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2002-07-27 01:12:17 +00:00
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#include "llvm/Assembly/Writer.h"
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2001-11-27 00:03:19 +00:00
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#include "Support/DepthFirstIterator.h"
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2001-11-26 18:41:20 +00:00
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#include <algorithm>
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2002-07-26 21:12:44 +00:00
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static RegisterAnalysis<LoopInfo>
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2002-07-30 16:27:52 +00:00
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X("loops", "Natural Loop Construction", true);
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2002-01-31 00:42:27 +00:00
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//===----------------------------------------------------------------------===//
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2002-04-28 16:21:30 +00:00
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// Loop implementation
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2002-01-31 00:42:27 +00:00
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//
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2002-06-03 22:10:52 +00:00
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bool Loop::contains(const BasicBlock *BB) const {
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2001-11-26 18:41:20 +00:00
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return find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
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}
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2002-10-11 05:31:10 +00:00
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bool Loop::isLoopExit(const BasicBlock *BB) const {
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for (BasicBlock::succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB);
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SI != SE; ++SI) {
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if (! contains(*SI))
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return true;
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}
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return false;
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}
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unsigned Loop::getNumBackEdges() const {
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unsigned numBackEdges = 0;
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BasicBlock *header = Blocks.front();
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for (std::vector<BasicBlock*>::const_iterator i = Blocks.begin(), e = Blocks.end();
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i != e; ++i) {
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for (BasicBlock::succ_iterator Successor = succ_begin(*i), SEnd = succ_end(*i);
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Successor != SEnd; ++Successor) {
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if (header == *Successor)
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++numBackEdges;
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}
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}
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return numBackEdges;
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}
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2002-07-27 01:12:17 +00:00
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void Loop::print(std::ostream &OS) const {
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OS << std::string(getLoopDepth()*2, ' ') << "Loop Containing: ";
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2002-04-09 05:43:19 +00:00
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2002-07-27 01:12:17 +00:00
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for (unsigned i = 0; i < getBlocks().size(); ++i) {
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if (i) OS << ",";
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WriteAsOperand(OS, (const Value*)getBlocks()[i]);
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}
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OS << "\n";
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2002-04-09 05:43:19 +00:00
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2002-09-29 21:43:04 +00:00
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for (unsigned i = 0, e = getSubLoops().size(); i != e; ++i)
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getSubLoops()[i]->print(OS);
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2002-07-27 01:12:17 +00:00
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}
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2002-01-31 00:42:27 +00:00
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//===----------------------------------------------------------------------===//
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2002-04-28 16:21:30 +00:00
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// LoopInfo implementation
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2002-01-31 00:42:27 +00:00
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//
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2002-08-26 16:45:19 +00:00
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void LoopInfo::stub() {}
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2002-07-27 01:12:17 +00:00
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2002-06-25 16:13:24 +00:00
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bool LoopInfo::runOnFunction(Function &) {
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2002-04-09 05:43:19 +00:00
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releaseMemory();
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2002-01-31 00:42:27 +00:00
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Calculate(getAnalysis<DominatorSet>()); // Update
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return false;
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}
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2002-07-27 01:12:17 +00:00
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void LoopInfo::releaseMemory() {
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for (std::vector<Loop*>::iterator I = TopLevelLoops.begin(),
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E = TopLevelLoops.end(); I != E; ++I)
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delete *I; // Delete all of the loops...
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BBMap.clear(); // Reset internal state of analysis
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TopLevelLoops.clear();
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}
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2002-04-28 16:21:30 +00:00
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void LoopInfo::Calculate(const DominatorSet &DS) {
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2002-04-28 00:15:57 +00:00
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BasicBlock *RootNode = DS.getRoot();
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2001-11-26 18:41:20 +00:00
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2002-04-28 00:15:57 +00:00
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for (df_iterator<BasicBlock*> NI = df_begin(RootNode),
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2001-11-26 18:41:20 +00:00
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NE = df_end(RootNode); NI != NE; ++NI)
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if (Loop *L = ConsiderForLoop(*NI, DS))
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TopLevelLoops.push_back(L);
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for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
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TopLevelLoops[i]->setLoopDepth(1);
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}
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2002-04-28 16:21:30 +00:00
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void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
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2002-04-27 06:56:12 +00:00
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AU.setPreservesAll();
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2002-08-08 19:01:28 +00:00
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AU.addRequired<DominatorSet>();
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2002-01-31 00:42:27 +00:00
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}
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2002-07-27 01:12:17 +00:00
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void LoopInfo::print(std::ostream &OS) const {
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2002-09-26 16:15:54 +00:00
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for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
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TopLevelLoops[i]->print(OS);
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2002-07-27 01:12:17 +00:00
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}
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2002-01-31 00:42:27 +00:00
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2002-04-28 16:21:30 +00:00
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Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) {
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2002-09-26 05:32:50 +00:00
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if (BBMap.find(BB) != BBMap.end()) return 0; // Haven't processed this node?
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2001-11-26 18:41:20 +00:00
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2002-04-28 00:15:57 +00:00
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std::vector<BasicBlock *> TodoStack;
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2001-11-26 18:41:20 +00:00
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// Scan the predecessors of BB, checking to see if BB dominates any of
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// them.
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2002-04-28 00:15:57 +00:00
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for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I)
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2001-11-26 18:41:20 +00:00
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if (DS.dominates(BB, *I)) // If BB dominates it's predecessor...
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TodoStack.push_back(*I);
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if (TodoStack.empty()) return 0; // Doesn't dominate any predecessors...
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// Create a new loop to represent this basic block...
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Loop *L = new Loop(BB);
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BBMap[BB] = L;
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while (!TodoStack.empty()) { // Process all the nodes in the loop
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BasicBlock *X = TodoStack.back();
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2001-11-26 18:41:20 +00:00
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TodoStack.pop_back();
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if (!L->contains(X)) { // As of yet unprocessed??
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L->Blocks.push_back(X);
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// Add all of the predecessors of X to the end of the work stack...
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2002-02-12 22:39:50 +00:00
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TodoStack.insert(TodoStack.end(), pred_begin(X), pred_end(X));
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2001-11-26 18:41:20 +00:00
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}
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}
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// Add the basic blocks that comprise this loop to the BBMap so that this
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// loop can be found for them. Also check subsidary basic blocks to see if
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// they start subloops of their own.
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//
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2002-04-28 00:15:57 +00:00
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for (std::vector<BasicBlock*>::reverse_iterator I = L->Blocks.rbegin(),
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2001-11-26 18:41:20 +00:00
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E = L->Blocks.rend(); I != E; ++I) {
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// Check to see if this block starts a new loop
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if (Loop *NewLoop = ConsiderForLoop(*I, DS)) {
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L->SubLoops.push_back(NewLoop);
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NewLoop->ParentLoop = L;
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}
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if (BBMap.find(*I) == BBMap.end())
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2002-01-20 22:54:45 +00:00
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BBMap.insert(std::make_pair(*I, L));
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2001-11-26 18:41:20 +00:00
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}
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return L;
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}
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2002-09-26 05:32:50 +00:00
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/// getLoopPreheader - If there is a preheader for this loop, return it. A
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/// loop has a preheader if there is only one edge to the header of the loop
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/// from outside of the loop. If this is the case, the block branching to the
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/// header of the loop is the preheader node. The "preheaders" pass can be
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/// "Required" to ensure that there is always a preheader node for every loop.
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///
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/// This method returns null if there is no preheader for the loop (either
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/// because the loop is dead or because multiple blocks branch to the header
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/// node of this loop).
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///
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BasicBlock *Loop::getLoopPreheader() const {
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// Keep track of nodes outside the loop branching to the header...
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BasicBlock *Out = 0;
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// Loop over the predecessors of the header node...
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BasicBlock *Header = getHeader();
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for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
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PI != PE; ++PI)
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2002-09-29 22:59:29 +00:00
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if (!contains(*PI)) { // If the block is not in the loop...
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if (Out && Out != *PI)
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return 0; // Multiple predecessors outside the loop
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Out = *PI;
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}
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// If there is exactly one preheader, return it. If there was zero, then Out
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// is still null.
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return Out;
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}
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/// addBasicBlockToLoop - This function is used by other analyses to update loop
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/// information. NewBB is set to be a new member of the current loop. Because
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/// of this, it is added as a member of all parent loops, and is added to the
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/// specified LoopInfo object as being in the current basic block. It is not
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/// valid to replace the loop header with this method.
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///
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void Loop::addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI) {
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assert(LI[getHeader()] == this && "Incorrect LI specified for this loop!");
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assert(NewBB && "Cannot add a null basic block to the loop!");
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assert(LI[NewBB] == 0 && "BasicBlock already in the loop!");
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// Add the loop mapping to the LoopInfo object...
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LI.BBMap[NewBB] = this;
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// Add the basic block to this loop and all parent loops...
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Loop *L = this;
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while (L) {
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L->Blocks.push_back(NewBB);
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L = L->getParentLoop();
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}
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}
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