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//===- PostOrderCFGView.h - Post order view of CFG blocks ---------*- C++ --*-//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file implements post order view of the blocks in a CFG.
#include <vector>
//#include <algorithm>
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/BitVector.h"
#include "clang/Analysis/AnalysisContext.h"
#include "clang/Analysis/CFG.h"
namespace clang {
class PostOrderCFGView : public ManagedAnalysis {
virtual void anchor();
/// \brief Implements a set of CFGBlocks using a BitVector.
/// This class contains a minimal interface, primarily dictated by the SetType
/// template parameter of the llvm::po_iterator template, as used with
/// external storage. We also use this set to keep track of which CFGBlocks we
/// visit during the analysis.
class CFGBlockSet {
llvm::BitVector VisitedBlockIDs;
// po_iterator requires this iterator, but the only interface needed is the
// value_type typedef.
struct iterator { typedef const CFGBlock *value_type; };
CFGBlockSet() {}
CFGBlockSet(const CFG *G) : VisitedBlockIDs(G->getNumBlockIDs(), false) {}
/// \brief Set the bit associated with a particular CFGBlock.
/// This is the important method for the SetType template parameter.
bool insert(const CFGBlock *Block) {
// Note that insert() is called by po_iterator, which doesn't check to
// make sure that Block is non-null. Moreover, the CFGBlock iterator will
// occasionally hand out null pointers for pruned edges, so we catch those
// here.
if (Block == 0)
return false; // if an edge is trivially false.
if (VisitedBlockIDs.test(Block->getBlockID()))
return false;
return true;
/// \brief Check if the bit for a CFGBlock has been already set.
/// This method is for tracking visited blocks in the main threadsafety
/// loop. Block must not be null.
bool alreadySet(const CFGBlock *Block) {
return VisitedBlockIDs.test(Block->getBlockID());
typedef llvm::po_iterator<const CFG*, CFGBlockSet, true> po_iterator;
std::vector<const CFGBlock*> Blocks;
typedef llvm::DenseMap<const CFGBlock *, unsigned> BlockOrderTy;
BlockOrderTy BlockOrder;
typedef std::vector<const CFGBlock*>::reverse_iterator iterator;
PostOrderCFGView(const CFG *cfg);
iterator begin() { return Blocks.rbegin(); }
iterator end() { return Blocks.rend(); }
bool empty() { return begin() == end(); }
struct BlockOrderCompare;
friend struct BlockOrderCompare;
struct BlockOrderCompare {
const PostOrderCFGView &POV;
BlockOrderCompare(const PostOrderCFGView &pov) : POV(pov) {}
bool operator()(const CFGBlock *b1, const CFGBlock *b2) const;
BlockOrderCompare getComparator() const {
return BlockOrderCompare(*this);
// Used by AnalyisContext to construct this object.
static const void *getTag();
static PostOrderCFGView *create(AnalysisDeclContext &analysisContext);
} // end clang namespace