forked from OSchip/llvm-project
Fix massive LiveVariables regression (due to LiveVariables rewrite) by addressing two performance problems:
- Speed of "merge()", which merged data flow facts. This was doing a set canonicalization on every insertion, which was super slow. To fix this, we use ImmutableSetRef. - Visit CFGBlocks in reverse postorder. This is a huge speedup, as on some test cases the algorithm would take many iterations to converge. This contains a bunch of copy-paste from UninitializedValues.cpp and ThreadSafety.cpp. The idea was to get something working first, and then refactor the common logic for all three files into a separate analysis/library entry point. llvm-svn: 139968
This commit is contained in:
Ted Kremenek
parent
502848ceda
commit
459597a6eb
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@ -4,6 +4,9 @@
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#include "clang/Analysis/AnalysisContext.h"
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#include "clang/AST/StmtVisitor.h"
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/ADT/DenseMap.h"
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#include <deque>
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#include <algorithm>
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#include <vector>
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@ -11,31 +14,199 @@
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using namespace clang;
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namespace {
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class LiveVariablesImpl {
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public:
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AnalysisContext &analysisContext;
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std::vector<LiveVariables::LivenessValues> cfgBlockValues;
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llvm::ImmutableSet<const Stmt *>::Factory SSetFact;
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llvm::ImmutableSet<const VarDecl *>::Factory DSetFact;
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llvm::DenseMap<const CFGBlock *, LiveVariables::LivenessValues> blocksEndToLiveness;
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llvm::DenseMap<const CFGBlock *, LiveVariables::LivenessValues> blocksBeginToLiveness;
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llvm::DenseMap<const Stmt *, LiveVariables::LivenessValues> stmtsToLiveness;
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llvm::DenseMap<const DeclRefExpr *, unsigned> inAssignment;
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const bool killAtAssign;
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LiveVariables::LivenessValues
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merge(LiveVariables::LivenessValues valsA,
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LiveVariables::LivenessValues valsB);
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LiveVariables::LivenessValues runOnBlock(const CFGBlock *block,
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LiveVariables::LivenessValues val,
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LiveVariables::Observer *obs = 0);
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void dumpBlockLiveness(const SourceManager& M);
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LiveVariablesImpl(AnalysisContext &ac, bool KillAtAssign)
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: analysisContext(ac), killAtAssign(KillAtAssign) {}
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// FIXME: This is copy-pasted from ThreadSafety.c. I wanted a patch that
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// contained working code before refactoring the implementation of both
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// files.
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class CFGBlockSet {
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llvm::BitVector VisitedBlockIDs;
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public:
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// po_iterator requires this iterator, but the only interface needed is the
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// value_type typedef.
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struct iterator {
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typedef const CFGBlock *value_type;
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};
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CFGBlockSet() {}
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CFGBlockSet(const CFG *G) : VisitedBlockIDs(G->getNumBlockIDs(), false) {}
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/// \brief Set the bit associated with a particular CFGBlock.
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/// This is the important method for the SetType template parameter.
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bool insert(const CFGBlock *Block) {
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// Note that insert() is called by po_iterator, which doesn't check to make
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// sure that Block is non-null. Moreover, the CFGBlock iterator will
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// occasionally hand out null pointers for pruned edges, so we catch those
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// here.
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if (Block == 0)
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return false; // if an edge is trivially false.
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if (VisitedBlockIDs.test(Block->getBlockID()))
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return false;
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VisitedBlockIDs.set(Block->getBlockID());
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return true;
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}
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/// \brief Check if the bit for a CFGBlock has been already set.
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/// This method is for tracking visited blocks in the main threadsafety loop.
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/// Block must not be null.
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bool alreadySet(const CFGBlock *Block) {
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return VisitedBlockIDs.test(Block->getBlockID());
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}
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};
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/// \brief We create a helper class which we use to iterate through CFGBlocks in
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/// the topological order.
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class TopologicallySortedCFG {
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typedef llvm::po_iterator<const CFG*, CFGBlockSet, true> po_iterator;
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std::vector<const CFGBlock*> Blocks;
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typedef llvm::DenseMap<const CFGBlock *, unsigned> BlockOrderTy;
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BlockOrderTy BlockOrder;
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public:
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typedef std::vector<const CFGBlock*>::reverse_iterator iterator;
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TopologicallySortedCFG(const CFG *CFGraph) {
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Blocks.reserve(CFGraph->getNumBlockIDs());
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CFGBlockSet BSet(CFGraph);
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for (po_iterator I = po_iterator::begin(CFGraph, BSet),
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E = po_iterator::end(CFGraph, BSet); I != E; ++I) {
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BlockOrder[*I] = Blocks.size() + 1;
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Blocks.push_back(*I);
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}
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}
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iterator begin() {
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return Blocks.rbegin();
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}
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iterator end() {
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return Blocks.rend();
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}
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bool empty() {
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return begin() == end();
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}
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struct BlockOrderCompare;
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friend struct BlockOrderCompare;
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struct BlockOrderCompare {
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const TopologicallySortedCFG &TSC;
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public:
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BlockOrderCompare(const TopologicallySortedCFG &tsc) : TSC(tsc) {}
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bool operator()(const CFGBlock *b1, const CFGBlock *b2) const {
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TopologicallySortedCFG::BlockOrderTy::const_iterator b1It = TSC.BlockOrder.find(b1);
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TopologicallySortedCFG::BlockOrderTy::const_iterator b2It = TSC.BlockOrder.find(b2);
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unsigned b1V = (b1It == TSC.BlockOrder.end()) ? 0 : b1It->second;
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unsigned b2V = (b2It == TSC.BlockOrder.end()) ? 0 : b2It->second;
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return b1V > b2V;
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}
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};
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BlockOrderCompare getComparator() const {
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return BlockOrderCompare(*this);
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}
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};
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class DataflowWorklist {
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SmallVector<const CFGBlock *, 20> worklist;
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llvm::BitVector enqueuedBlocks;
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TopologicallySortedCFG TSC;
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public:
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DataflowWorklist(const CFG &cfg)
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: enqueuedBlocks(cfg.getNumBlockIDs()),
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TSC(&cfg) {}
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void enqueueBlock(const CFGBlock *block);
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void enqueueSuccessors(const CFGBlock *block);
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void enqueuePredecessors(const CFGBlock *block);
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const CFGBlock *dequeue();
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void sortWorklist();
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};
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}
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void DataflowWorklist::enqueueBlock(const clang::CFGBlock *block) {
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if (block && !enqueuedBlocks[block->getBlockID()]) {
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enqueuedBlocks[block->getBlockID()] = true;
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worklist.push_back(block);
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}
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}
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void DataflowWorklist::enqueueSuccessors(const clang::CFGBlock *block) {
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const unsigned OldWorklistSize = worklist.size();
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for (CFGBlock::const_succ_iterator I = block->succ_begin(),
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E = block->succ_end(); I != E; ++I) {
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enqueueBlock(*I);
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}
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if (OldWorklistSize == 0 || OldWorklistSize == worklist.size())
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return;
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sortWorklist();
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}
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void DataflowWorklist::enqueuePredecessors(const clang::CFGBlock *block) {
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const unsigned OldWorklistSize = worklist.size();
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for (CFGBlock::const_pred_iterator I = block->pred_begin(),
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E = block->pred_end(); I != E; ++I) {
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enqueueBlock(*I);
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}
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if (OldWorklistSize == 0 || OldWorklistSize == worklist.size())
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return;
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sortWorklist();
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}
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void DataflowWorklist::sortWorklist() {
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std::sort(worklist.begin(), worklist.end(), TSC.getComparator());
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}
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const CFGBlock *DataflowWorklist::dequeue() {
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if (worklist.empty())
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return 0;
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const CFGBlock *b = worklist.back();
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worklist.pop_back();
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enqueuedBlocks[b->getBlockID()] = false;
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return b;
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}
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namespace {
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class LiveVariablesImpl {
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public:
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AnalysisContext &analysisContext;
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std::vector<LiveVariables::LivenessValues> cfgBlockValues;
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llvm::ImmutableSet<const Stmt *>::Factory SSetFact;
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llvm::ImmutableSet<const VarDecl *>::Factory DSetFact;
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llvm::DenseMap<const CFGBlock *, LiveVariables::LivenessValues> blocksEndToLiveness;
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llvm::DenseMap<const CFGBlock *, LiveVariables::LivenessValues> blocksBeginToLiveness;
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llvm::DenseMap<const Stmt *, LiveVariables::LivenessValues> stmtsToLiveness;
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llvm::DenseMap<const DeclRefExpr *, unsigned> inAssignment;
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const bool killAtAssign;
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LiveVariables::LivenessValues
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merge(LiveVariables::LivenessValues valsA,
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LiveVariables::LivenessValues valsB);
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LiveVariables::LivenessValues runOnBlock(const CFGBlock *block,
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LiveVariables::LivenessValues val,
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LiveVariables::Observer *obs = 0);
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void dumpBlockLiveness(const SourceManager& M);
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LiveVariablesImpl(AnalysisContext &ac, bool KillAtAssign)
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: analysisContext(ac), killAtAssign(KillAtAssign) {}
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};
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}
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static LiveVariablesImpl &getImpl(void *x) {
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@ -56,9 +227,12 @@ bool LiveVariables::LivenessValues::isLive(const VarDecl *D) const {
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namespace {
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template <typename SET>
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SET mergeSets(typename SET::Factory &F, SET A, SET B) {
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SET mergeSets(SET A, SET B) {
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if (A.isEmpty())
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return B;
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for (typename SET::iterator it = B.begin(), ei = B.end(); it != ei; ++it) {
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A = F.add(A, *it);
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A = A.add(*it);
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}
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return A;
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}
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@ -67,8 +241,22 @@ namespace {
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LiveVariables::LivenessValues
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LiveVariablesImpl::merge(LiveVariables::LivenessValues valsA,
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LiveVariables::LivenessValues valsB) {
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return LiveVariables::LivenessValues(mergeSets(SSetFact, valsA.liveStmts, valsB.liveStmts),
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mergeSets(DSetFact, valsA.liveDecls, valsB.liveDecls));
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llvm::ImmutableSetRef<const Stmt *>
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SSetRefA(valsA.liveStmts.getRootWithoutRetain(), SSetFact.getTreeFactory()),
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SSetRefB(valsB.liveStmts.getRootWithoutRetain(), SSetFact.getTreeFactory());
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llvm::ImmutableSetRef<const VarDecl *>
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DSetRefA(valsA.liveDecls.getRootWithoutRetain(), DSetFact.getTreeFactory()),
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DSetRefB(valsB.liveDecls.getRootWithoutRetain(), DSetFact.getTreeFactory());
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SSetRefA = mergeSets(SSetRefA, SSetRefB);
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DSetRefA = mergeSets(DSetRefA, DSetRefB);
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return LiveVariables::LivenessValues(SSetRefA.asImmutableSet(),
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DSetRefA.asImmutableSet());
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}
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bool LiveVariables::LivenessValues::equals(const LivenessValues &V) const {
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@ -100,29 +288,6 @@ bool LiveVariables::isLive(const Stmt *Loc, const Stmt *S) {
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//===----------------------------------------------------------------------===//
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namespace {
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class Worklist {
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llvm::BitVector isBlockEnqueued;
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std::deque<const CFGBlock *> workListContents;
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public:
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Worklist(CFG &cfg) : isBlockEnqueued(cfg.getNumBlockIDs()) {}
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bool empty() const { return workListContents.empty(); }
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const CFGBlock *getNextItem() {
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const CFGBlock *block = workListContents.front();
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workListContents.pop_front();
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isBlockEnqueued[block->getBlockID()] = false;
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return block;
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}
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void enqueueBlock(const CFGBlock *block) {
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if (!isBlockEnqueued[block->getBlockID()]) {
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isBlockEnqueued[block->getBlockID()] = true;
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workListContents.push_back(block);
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}
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}
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};
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class TransferFunctions : public StmtVisitor<TransferFunctions> {
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LiveVariablesImpl &LV;
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LiveVariables::LivenessValues &val;
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@ -390,7 +555,7 @@ LiveVariables::computeLiveness(AnalysisContext &AC,
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// Construct the dataflow worklist. Enqueue the exit block as the
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// start of the analysis.
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Worklist worklist(*cfg);
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DataflowWorklist worklist(*cfg);
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llvm::BitVector everAnalyzedBlock(cfg->getNumBlockIDs());
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// FIXME: we should enqueue using post order.
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@ -418,10 +583,9 @@ LiveVariables::computeLiveness(AnalysisContext &AC,
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}
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}
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while (!worklist.empty()) {
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// Dequeue blocks in FIFO order.
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const CFGBlock *block = worklist.getNextItem();
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worklist.sortWorklist();
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while (const CFGBlock *block = worklist.dequeue()) {
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// Determine if the block's end value has changed. If not, we
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// have nothing left to do for this block.
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LivenessValues &prevVal = LV->blocksEndToLiveness[block];
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@ -430,8 +594,9 @@ LiveVariables::computeLiveness(AnalysisContext &AC,
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LivenessValues val;
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for (CFGBlock::const_succ_iterator it = block->succ_begin(),
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ei = block->succ_end(); it != ei; ++it) {
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if (const CFGBlock *succ = *it)
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if (const CFGBlock *succ = *it) {
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val = LV->merge(val, LV->blocksBeginToLiveness[succ]);
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}
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}
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if (!everAnalyzedBlock[block->getBlockID()])
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@ -445,12 +610,7 @@ LiveVariables::computeLiveness(AnalysisContext &AC,
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LV->blocksBeginToLiveness[block] = LV->runOnBlock(block, val);
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// Enqueue the value to the predecessors.
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for (CFGBlock::const_pred_iterator it = block->pred_begin(),
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ei = block->pred_end(); it != ei; ++it)
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{
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if (const CFGBlock *pred = *it)
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worklist.enqueueBlock(pred);
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}
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worklist.enqueuePredecessors(block);
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}
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return new LiveVariables(LV);
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