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106 lines
3.5 KiB
C++
106 lines
3.5 KiB
C++
//===- 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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#include "llvm/BasicBlock.h"
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#include "Support/DepthFirstIterator.h"
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#include <algorithm>
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AnalysisID cfg::LoopInfo::ID(AnalysisID::create<cfg::LoopInfo>());
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//===----------------------------------------------------------------------===//
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// cfg::Loop implementation
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//
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bool cfg::Loop::contains(const BasicBlock *BB) const {
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return find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
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}
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//===----------------------------------------------------------------------===//
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// cfg::LoopInfo implementation
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//
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bool cfg::LoopInfo::runOnMethod(Method *M) {
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BBMap.clear(); // Reset internal state of analysis
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TopLevelLoops.clear();
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Calculate(getAnalysis<DominatorSet>()); // Update
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return false;
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}
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void cfg::LoopInfo::Calculate(const DominatorSet &DS) {
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const BasicBlock *RootNode = DS.getRoot();
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for (df_iterator<const BasicBlock*> NI = df_begin(RootNode),
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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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void cfg::LoopInfo::getAnalysisUsageInfo(Pass::AnalysisSet &Required,
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Pass::AnalysisSet &Destroyed,
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Pass::AnalysisSet &Provided) {
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Required.push_back(DominatorSet::ID);
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Provided.push_back(ID);
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}
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cfg::Loop *cfg::LoopInfo::ConsiderForLoop(const BasicBlock *BB,
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const DominatorSet &DS) {
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if (BBMap.find(BB) != BBMap.end()) return 0; // Havn't processed this node?
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std::vector<const BasicBlock *> TodoStack;
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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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for (BasicBlock::pred_const_iterator I = BB->pred_begin(),
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E = BB->pred_end(); I != E; ++I)
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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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const BasicBlock *X = TodoStack.back();
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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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TodoStack.insert(TodoStack.end(), X->pred_begin(), X->pred_end());
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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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for (std::vector<const BasicBlock*>::reverse_iterator I = L->Blocks.rbegin(),
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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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BBMap.insert(std::make_pair(*I, L));
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}
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return L;
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}
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