path: root/lib/Analysis/LiveVariables.cpp

#include "clang/Analysis/Analyses/LiveVariables.h"
#include "clang/AST/Stmt.h"
#include "clang/Analysis/CFG.h"
#include "clang/Analysis/AnalysisContext.h"
#include "clang/AST/StmtVisitor.h"

#include <deque>
#include <algorithm>
#include <vector>

using namespace clang;

namespace {
  class LiveVariablesImpl {
  public:  
    AnalysisContext &analysisContext;
    std::vector<LiveVariables::LivenessValues> cfgBlockValues;
    llvm::ImmutableSet<const Stmt *>::Factory SSetFact;
    llvm::ImmutableSet<const VarDecl *>::Factory DSetFact;
    llvm::DenseMap<const CFGBlock *, LiveVariables::LivenessValues> blocksEndToLiveness;
    llvm::DenseMap<const CFGBlock *, LiveVariables::LivenessValues> blocksBeginToLiveness;
    llvm::DenseMap<const Stmt *, LiveVariables::LivenessValues> stmtsToLiveness;
    llvm::DenseMap<const DeclRefExpr *, unsigned> inAssignment;
    const bool killAtAssign;
    
    LiveVariables::LivenessValues
    merge(LiveVariables::LivenessValues valsA,
          LiveVariables::LivenessValues valsB);
        
    LiveVariables::LivenessValues runOnBlock(const CFGBlock *block,
                                             LiveVariables::LivenessValues val,
                                             LiveVariables::Observer *obs = 0);

    void dumpBlockLiveness(const SourceManager& M);

    LiveVariablesImpl(AnalysisContext &ac, bool KillAtAssign)
      : analysisContext(ac), killAtAssign(KillAtAssign) {}
  };
}

static LiveVariablesImpl &getImpl(void* x) {
  return *((LiveVariablesImpl *) x);
}

//===----------------------------------------------------------------------===//
// Operations and queries on LivenessValues.
//===----------------------------------------------------------------------===//

bool LiveVariables::LivenessValues::isLive(const Stmt *S) const {
  return liveStmts.contains(S);
}

bool LiveVariables::LivenessValues::isLive(const VarDecl *D) const {
  return liveDecls.contains(D);
}

namespace {
  template <typename SET>
  SET mergeSets(typename SET::Factory &F, SET A, SET B) {
    for (typename SET::iterator it = B.begin(), ei = B.end(); it != ei; ++it) {
      A = F.add(A, *it);
    }
    return A;
  }
}

LiveVariables::LivenessValues
LiveVariablesImpl::merge(LiveVariables::LivenessValues valsA,
                         LiveVariables::LivenessValues valsB) {  
  return LiveVariables::LivenessValues(mergeSets(SSetFact, valsA.liveStmts, valsB.liveStmts),
                        mergeSets(DSetFact, valsA.liveDecls, valsB.liveDecls));
}

bool LiveVariables::LivenessValues::equals(const LivenessValues &V) const {
  return liveStmts == V.liveStmts && liveDecls == V.liveDecls;
}

//===----------------------------------------------------------------------===//
// Query methods.
//===----------------------------------------------------------------------===//

static bool isAlwaysAlive(const VarDecl *D) {
  return D->hasGlobalStorage();
}

bool LiveVariables::isLive(const CFGBlock *B, const VarDecl *D) {
  return isAlwaysAlive(D) || getImpl(impl).blocksEndToLiveness[B].isLive(D);
}

bool LiveVariables::isLive(const Stmt *S, const VarDecl *D) {
  return isAlwaysAlive(D) || getImpl(impl).stmtsToLiveness[S].isLive(D);
}

bool LiveVariables::isLive(const Stmt *Loc, const Stmt *S) {
  return getImpl(impl).stmtsToLiveness[Loc].isLive(S);
}

//===----------------------------------------------------------------------===//
// Dataflow computation.
//===----------------------------------------------------------------------===//

namespace {
class Worklist {
  llvm::BitVector isBlockEnqueued;
  std::deque<const CFGBlock *> workListContents;
public:
  Worklist(CFG &cfg) : isBlockEnqueued(cfg.getNumBlockIDs()) {}
  
  bool empty() const { return workListContents.empty(); }
  
  const CFGBlock *getNextItem() {
    const CFGBlock *block = workListContents.front();
    workListContents.pop_front();
    isBlockEnqueued[block->getBlockID()] = false;
    return block;
  }
  
  void enqueueBlock(const CFGBlock *block) {
    if (!isBlockEnqueued[block->getBlockID()]) {
      isBlockEnqueued[block->getBlockID()] = true;
      workListContents.push_back(block);
    }
  }
};
  
class TransferFunctions : public StmtVisitor<TransferFunctions> {
  LiveVariablesImpl &LV;
  LiveVariables::LivenessValues &val;
  LiveVariables::Observer *observer;
  const CFGBlock *currentBlock;
public:
  TransferFunctions(LiveVariablesImpl &im,
                    LiveVariables::LivenessValues &Val,
                    LiveVariables::Observer *Observer,
                    const CFGBlock *CurrentBlock)
  : LV(im), val(Val), observer(Observer), currentBlock(CurrentBlock) {}

  void VisitBinaryOperator(BinaryOperator *BO);
  void VisitBlockExpr(BlockExpr *BE);
  void VisitDeclRefExpr(DeclRefExpr *DR);  
  void VisitDeclStmt(DeclStmt *DS);
  void VisitObjCForCollectionStmt(ObjCForCollectionStmt *OS);
  void VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *UE);
  void VisitUnaryOperator(UnaryOperator *UO);
  void Visit(Stmt *S);
};
}

void TransferFunctions::Visit(Stmt *S) {
  if (observer)
    observer->observeStmt(S, currentBlock, val);
  
  StmtVisitor<TransferFunctions>::Visit(S);
  
  if (isa<Expr>(S)) {
    val.liveStmts = LV.SSetFact.remove(val.liveStmts, S);
  }

  // Mark all children expressions live.
  
  switch (S->getStmtClass()) {
    default:
      break;
    case Stmt::StmtExprClass: {
      // For statement expressions, look through the compound statement.
      S = cast<StmtExpr>(S)->getSubStmt();
      break;
    }
    case Stmt::CXXMemberCallExprClass: {
      // Include the implicit "this" pointer as being live.
      CXXMemberCallExpr *CE = cast<CXXMemberCallExpr>(S);
      val.liveStmts =
        LV.SSetFact.add(val.liveStmts,
                        CE->getImplicitObjectArgument()->IgnoreParens());
      break;
    }
    // FIXME: These cases eventually shouldn't be needed.
    case Stmt::ExprWithCleanupsClass: {
      S = cast<ExprWithCleanups>(S)->getSubExpr();
      break;
    }
    case Stmt::CXXBindTemporaryExprClass: {
      S = cast<CXXBindTemporaryExpr>(S)->getSubExpr();
      break;
    }
    case Stmt::MaterializeTemporaryExprClass: {
      S = cast<MaterializeTemporaryExpr>(S)->GetTemporaryExpr();
      break;
    }
  }
  
  for (Stmt::child_iterator it = S->child_begin(), ei = S->child_end();
       it != ei; ++it) {
    if (Stmt *child = *it) {
      if (Expr *Ex = dyn_cast<Expr>(child))
        child = Ex->IgnoreParens();
               
      val.liveStmts = LV.SSetFact.add(val.liveStmts, child);
    }
  }
}

void TransferFunctions::VisitBinaryOperator