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-rw-r--r--clang/lib/Analysis/CFGReachabilityAnalysis.cpp76
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+//==- 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.back();
+ worklist.pop_back();
+
+ 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) {
+ worklist.push_back(*i);
+ }
+ }
+}