| //==- CFGReachabilityAnalysis.cpp - Basic reachability analysis --*- C++ -*-==// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines a flow-sensitive, (mostly) path-insensitive reachability |
| // analysis based on Clang's CFGs. Clients can query if a given basic block |
| // is reachable within the CFG. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/ADT/SmallVector.h" |
| #include "clang/Analysis/Analyses/CFGReachabilityAnalysis.h" |
| #include "clang/Analysis/CFG.h" |
| |
| using namespace clang; |
| |
| CFGReverseBlockReachabilityAnalysis::CFGReverseBlockReachabilityAnalysis(const CFG &cfg) |
| : analyzed(cfg.getNumBlockIDs(), false) {} |
| |
| bool CFGReverseBlockReachabilityAnalysis::isReachable(const CFGBlock *Src, |
| const CFGBlock *Dst) { |
| |
| const unsigned DstBlockID = Dst->getBlockID(); |
| |
| // If we haven't analyzed the destination node, run the analysis now |
| if (!analyzed[DstBlockID]) { |
| mapReachability(Dst); |
| analyzed[DstBlockID] = true; |
| } |
| |
| // Return the cached result |
| return reachable[DstBlockID][Src->getBlockID()]; |
| } |
| |
| // Maps reachability to a common node by walking the predecessors of the |
| // destination node. |
| void CFGReverseBlockReachabilityAnalysis::mapReachability(const CFGBlock *Dst) { |
| SmallVector<const CFGBlock *, 11> worklist; |
| llvm::BitVector visited(analyzed.size()); |
| |
| ReachableSet &DstReachability = reachable[Dst->getBlockID()]; |
| DstReachability.resize(analyzed.size(), false); |
| |
| // Start searching from the destination node, since we commonly will perform |
| // multiple queries relating to a destination node. |
| worklist.push_back(Dst); |
| bool firstRun = true; |
| |
| while (!worklist.empty()) { |
| const CFGBlock *block = worklist.pop_back_val(); |
| |
| if (visited[block->getBlockID()]) |
| continue; |
| visited[block->getBlockID()] = true; |
| |
| // Update reachability information for this node -> Dst |
| if (!firstRun) { |
| // Don't insert Dst -> Dst unless it was a predecessor of itself |
| DstReachability[block->getBlockID()] = true; |
| } |
| else |
| firstRun = false; |
| |
| // Add the predecessors to the worklist. |
| for (CFGBlock::const_pred_iterator i = block->pred_begin(), |
| e = block->pred_end(); i != e; ++i) { |
| if (*i) |
| worklist.push_back(*i); |
| } |
| } |
| } |