1 //==- CFGReachabilityAnalysis.cpp - Basic reachability analysis --*- C++ -*-==//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines a flow-sensitive, (mostly) path-insensitive reachability
11 // analysis based on Clang's CFGs. Clients can query if a given basic block
12 // is reachable within the CFG.
14 //===----------------------------------------------------------------------===//
16 #include "llvm/ADT/SmallVector.h"
17 #include "clang/Analysis/Analyses/CFGReachabilityAnalysis.h"
18 #include "clang/Analysis/CFG.h"
20 using namespace clang;
22 CFGReverseBlockReachabilityAnalysis::CFGReverseBlockReachabilityAnalysis(const CFG &cfg)
23 : analyzed(cfg.getNumBlockIDs(), false) {}
25 bool CFGReverseBlockReachabilityAnalysis::isReachable(const CFGBlock *Src,
26 const CFGBlock *Dst) {
28 const unsigned DstBlockID = Dst->getBlockID();
30 // If we haven't analyzed the destination node, run the analysis now
31 if (!analyzed[DstBlockID]) {
33 analyzed[DstBlockID] = true;
36 // Return the cached result
37 return reachable[DstBlockID][Src->getBlockID()];
40 // Maps reachability to a common node by walking the predecessors of the
42 void CFGReverseBlockReachabilityAnalysis::mapReachability(const CFGBlock *Dst) {
43 SmallVector<const CFGBlock *, 11> worklist;
44 llvm::BitVector visited(analyzed.size());
46 ReachableSet &DstReachability = reachable[Dst->getBlockID()];
47 DstReachability.resize(analyzed.size(), false);
49 // Start searching from the destination node, since we commonly will perform
50 // multiple queries relating to a destination node.
51 worklist.push_back(Dst);
54 while (!worklist.empty()) {
55 const CFGBlock *block = worklist.pop_back_val();
57 if (visited[block->getBlockID()])
59 visited[block->getBlockID()] = true;
61 // Update reachability information for this node -> Dst
63 // Don't insert Dst -> Dst unless it was a predecessor of itself
64 DstReachability[block->getBlockID()] = true;
69 // Add the predecessors to the worklist.
70 for (CFGBlock::const_pred_iterator i = block->pred_begin(),
71 e = block->pred_end(); i != e; ++i) {
72 worklist.push_back(*i);