416 lines
13 KiB
C++
416 lines
13 KiB
C++
//=-- ExplodedGraph.cpp - Local, Path-Sens. "Exploded Graph" -*- C++ -*------=//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the template classes ExplodedNode and ExplodedGraph,
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// which represent a path-sensitive, intra-procedural "exploded graph."
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//
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//===----------------------------------------------------------------------===//
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#include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
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#include "clang/AST/Stmt.h"
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#include "clang/AST/ParentMap.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include <vector>
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using namespace clang;
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using namespace ento;
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//===----------------------------------------------------------------------===//
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// Node auditing.
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//===----------------------------------------------------------------------===//
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// An out of line virtual method to provide a home for the class vtable.
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ExplodedNode::Auditor::~Auditor() {}
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#ifndef NDEBUG
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static ExplodedNode::Auditor* NodeAuditor = 0;
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#endif
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void ExplodedNode::SetAuditor(ExplodedNode::Auditor* A) {
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#ifndef NDEBUG
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NodeAuditor = A;
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#endif
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}
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//===----------------------------------------------------------------------===//
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// Cleanup.
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//===----------------------------------------------------------------------===//
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static const unsigned CounterTop = 1000;
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ExplodedGraph::ExplodedGraph()
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: NumNodes(0), reclaimNodes(false), reclaimCounter(CounterTop) {}
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ExplodedGraph::~ExplodedGraph() {}
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//===----------------------------------------------------------------------===//
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// Node reclamation.
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//===----------------------------------------------------------------------===//
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bool ExplodedGraph::shouldCollect(const ExplodedNode *node) {
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// Reclaim all nodes that match *all* the following criteria:
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//
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// (1) 1 predecessor (that has one successor)
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// (2) 1 successor (that has one predecessor)
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// (3) The ProgramPoint is for a PostStmt.
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// (4) There is no 'tag' for the ProgramPoint.
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// (5) The 'store' is the same as the predecessor.
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// (6) The 'GDM' is the same as the predecessor.
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// (7) The LocationContext is the same as the predecessor.
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// (8) The PostStmt is for a non-consumed Stmt or Expr.
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// (9) The successor is not a CallExpr StmtPoint (so that we would be able to
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// find it when retrying a call with no inlining).
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// FIXME: It may be safe to reclaim PreCall and PostCall nodes as well.
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// Conditions 1 and 2.
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if (node->pred_size() != 1 || node->succ_size() != 1)
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return false;
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const ExplodedNode *pred = *(node->pred_begin());
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if (pred->succ_size() != 1)
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return false;
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const ExplodedNode *succ = *(node->succ_begin());
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if (succ->pred_size() != 1)
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return false;
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// Condition 3.
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ProgramPoint progPoint = node->getLocation();
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if (!isa<PostStmt>(progPoint))
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return false;
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// Condition 4.
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PostStmt ps = cast<PostStmt>(progPoint);
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if (ps.getTag())
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return false;
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if (isa<BinaryOperator>(ps.getStmt()))
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return false;
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// Conditions 5, 6, and 7.
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ProgramStateRef state = node->getState();
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ProgramStateRef pred_state = pred->getState();
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if (state->store != pred_state->store || state->GDM != pred_state->GDM ||
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progPoint.getLocationContext() != pred->getLocationContext())
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return false;
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// Condition 8.
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if (const Expr *Ex = dyn_cast<Expr>(ps.getStmt())) {
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ParentMap &PM = progPoint.getLocationContext()->getParentMap();
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if (!PM.isConsumedExpr(Ex))
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return false;
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}
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// Condition 9.
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const ProgramPoint SuccLoc = succ->getLocation();
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if (const StmtPoint *SP = dyn_cast<StmtPoint>(&SuccLoc))
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if (CallEvent::mayBeInlined(SP->getStmt()))
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return false;
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return true;
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}
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void ExplodedGraph::collectNode(ExplodedNode *node) {
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// Removing a node means:
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// (a) changing the predecessors successor to the successor of this node
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// (b) changing the successors predecessor to the predecessor of this node
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// (c) Putting 'node' onto freeNodes.
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assert(node->pred_size() == 1 || node->succ_size() == 1);
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ExplodedNode *pred = *(node->pred_begin());
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ExplodedNode *succ = *(node->succ_begin());
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pred->replaceSuccessor(succ);
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succ->replacePredecessor(pred);
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FreeNodes.push_back(node);
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Nodes.RemoveNode(node);
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--NumNodes;
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node->~ExplodedNode();
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}
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void ExplodedGraph::reclaimRecentlyAllocatedNodes() {
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if (ChangedNodes.empty())
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return;
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// Only periodically relcaim nodes so that we can build up a set of
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// nodes that meet the reclamation criteria. Freshly created nodes
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// by definition have no successor, and thus cannot be reclaimed (see below).
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assert(reclaimCounter > 0);
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if (--reclaimCounter != 0)
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return;
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reclaimCounter = CounterTop;
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for (NodeVector::iterator it = ChangedNodes.begin(), et = ChangedNodes.end();
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it != et; ++it) {
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ExplodedNode *node = *it;
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if (shouldCollect(node))
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collectNode(node);
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}
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ChangedNodes.clear();
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}
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//===----------------------------------------------------------------------===//
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// ExplodedNode.
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//===----------------------------------------------------------------------===//
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static inline BumpVector<ExplodedNode*>& getVector(void *P) {
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return *reinterpret_cast<BumpVector<ExplodedNode*>*>(P);
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}
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void ExplodedNode::addPredecessor(ExplodedNode *V, ExplodedGraph &G) {
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assert (!V->isSink());
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Preds.addNode(V, G);
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V->Succs.addNode(this, G);
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#ifndef NDEBUG
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if (NodeAuditor) NodeAuditor->AddEdge(V, this);
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#endif
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}
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void ExplodedNode::NodeGroup::replaceNode(ExplodedNode *node) {
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assert(getKind() == Size1);
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P = reinterpret_cast<uintptr_t>(node);
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assert(getKind() == Size1);
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}
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void ExplodedNode::NodeGroup::addNode(ExplodedNode *N, ExplodedGraph &G) {
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assert((reinterpret_cast<uintptr_t>(N) & Mask) == 0x0);
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assert(!getFlag());
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if (getKind() == Size1) {
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if (ExplodedNode *NOld = getNode()) {
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BumpVectorContext &Ctx = G.getNodeAllocator();
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BumpVector<ExplodedNode*> *V =
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G.getAllocator().Allocate<BumpVector<ExplodedNode*> >();
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new (V) BumpVector<ExplodedNode*>(Ctx, 4);
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assert((reinterpret_cast<uintptr_t>(V) & Mask) == 0x0);
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V->push_back(NOld, Ctx);
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V->push_back(N, Ctx);
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P = reinterpret_cast<uintptr_t>(V) | SizeOther;
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assert(getPtr() == (void*) V);
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assert(getKind() == SizeOther);
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}
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else {
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P = reinterpret_cast<uintptr_t>(N);
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assert(getKind() == Size1);
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}
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}
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else {
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assert(getKind() == SizeOther);
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getVector(getPtr()).push_back(N, G.getNodeAllocator());
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}
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}
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unsigned ExplodedNode::NodeGroup::size() const {
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if (getFlag())
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return 0;
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if (getKind() == Size1)
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return getNode() ? 1 : 0;
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else
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return getVector(getPtr()).size();
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}
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ExplodedNode **ExplodedNode::NodeGroup::begin() const {
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if (getFlag())
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return NULL;
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if (getKind() == Size1)
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return (ExplodedNode**) (getPtr() ? &P : NULL);
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else
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return const_cast<ExplodedNode**>(&*(getVector(getPtr()).begin()));
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}
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ExplodedNode** ExplodedNode::NodeGroup::end() const {
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if (getFlag())
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return NULL;
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if (getKind() == Size1)
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return (ExplodedNode**) (getPtr() ? &P+1 : NULL);
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else {
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// Dereferencing end() is undefined behaviour. The vector is not empty, so
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// we can dereference the last elem and then add 1 to the result.
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return const_cast<ExplodedNode**>(getVector(getPtr()).end());
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}
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}
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ExplodedNode *ExplodedGraph::getNode(const ProgramPoint &L,
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ProgramStateRef State,
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bool IsSink,
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bool* IsNew) {
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// Profile 'State' to determine if we already have an existing node.
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llvm::FoldingSetNodeID profile;
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void *InsertPos = 0;
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NodeTy::Profile(profile, L, State, IsSink);
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NodeTy* V = Nodes.FindNodeOrInsertPos(profile, InsertPos);
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if (!V) {
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if (!FreeNodes.empty()) {
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V = FreeNodes.back();
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FreeNodes.pop_back();
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}
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else {
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// Allocate a new node.
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V = (NodeTy*) getAllocator().Allocate<NodeTy>();
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}
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new (V) NodeTy(L, State, IsSink);
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if (reclaimNodes)
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ChangedNodes.push_back(V);
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// Insert the node into the node set and return it.
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Nodes.InsertNode(V, InsertPos);
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++NumNodes;
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if (IsNew) *IsNew = true;
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}
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else
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if (IsNew) *IsNew = false;
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return V;
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}
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std::pair<ExplodedGraph*, InterExplodedGraphMap*>
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ExplodedGraph::Trim(const NodeTy* const* NBeg, const NodeTy* const* NEnd,
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llvm::DenseMap<const void*, const void*> *InverseMap) const {
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if (NBeg == NEnd)
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return std::make_pair((ExplodedGraph*) 0,
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(InterExplodedGraphMap*) 0);
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assert (NBeg < NEnd);
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OwningPtr<InterExplodedGraphMap> M(new InterExplodedGraphMap());
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ExplodedGraph* G = TrimInternal(NBeg, NEnd, M.get(), InverseMap);
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return std::make_pair(static_cast<ExplodedGraph*>(G), M.take());
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}
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ExplodedGraph*
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ExplodedGraph::TrimInternal(const ExplodedNode* const* BeginSources,
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const ExplodedNode* const* EndSources,
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InterExplodedGraphMap* M,
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llvm::DenseMap<const void*, const void*> *InverseMap) const {
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typedef llvm::DenseSet<const ExplodedNode*> Pass1Ty;
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Pass1Ty Pass1;
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typedef llvm::DenseMap<const ExplodedNode*, ExplodedNode*> Pass2Ty;
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Pass2Ty& Pass2 = M->M;
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SmallVector<const ExplodedNode*, 10> WL1, WL2;
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// ===- Pass 1 (reverse DFS) -===
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for (const ExplodedNode* const* I = BeginSources; I != EndSources; ++I) {
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assert(*I);
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WL1.push_back(*I);
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}
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// Process the first worklist until it is empty. Because it is a std::list
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// it acts like a FIFO queue.
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while (!WL1.empty()) {
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const ExplodedNode *N = WL1.back();
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WL1.pop_back();
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// Have we already visited this node? If so, continue to the next one.
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if (Pass1.count(N))
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continue;
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// Otherwise, mark this node as visited.
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Pass1.insert(N);
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// If this is a root enqueue it to the second worklist.
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if (N->Preds.empty()) {
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WL2.push_back(N);
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continue;
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}
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// Visit our predecessors and enqueue them.
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for (ExplodedNode** I=N->Preds.begin(), **E=N->Preds.end(); I!=E; ++I)
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WL1.push_back(*I);
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}
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// We didn't hit a root? Return with a null pointer for the new graph.
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if (WL2.empty())
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return 0;
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// Create an empty graph.
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ExplodedGraph* G = MakeEmptyGraph();
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// ===- Pass 2 (forward DFS to construct the new graph) -===
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while (!WL2.empty()) {
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const ExplodedNode *N = WL2.back();
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WL2.pop_back();
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// Skip this node if we have already processed it.
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if (Pass2.find(N) != Pass2.end())
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continue;
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// Create the corresponding node in the new graph and record the mapping
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// from the old node to the new node.
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ExplodedNode *NewN = G->getNode(N->getLocation(), N->State, N->isSink(), 0);
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Pass2[N] = NewN;
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// Also record the reverse mapping from the new node to the old node.
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if (InverseMap) (*InverseMap)[NewN] = N;
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// If this node is a root, designate it as such in the graph.
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if (N->Preds.empty())
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G->addRoot(NewN);
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// In the case that some of the intended predecessors of NewN have already
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// been created, we should hook them up as predecessors.
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// Walk through the predecessors of 'N' and hook up their corresponding
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// nodes in the new graph (if any) to the freshly created node.
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for (ExplodedNode **I=N->Preds.begin(), **E=N->Preds.end(); I!=E; ++I) {
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Pass2Ty::iterator PI = Pass2.find(*I);
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if (PI == Pass2.end())
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continue;
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NewN->addPredecessor(PI->second, *G);
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}
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// In the case that some of the intended successors of NewN have already
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// been created, we should hook them up as successors. Otherwise, enqueue
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// the new nodes from the original graph that should have nodes created
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// in the new graph.
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for (ExplodedNode **I=N->Succs.begin(), **E=N->Succs.end(); I!=E; ++I) {
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Pass2Ty::iterator PI = Pass2.find(*I);
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if (PI != Pass2.end()) {
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PI->second->addPredecessor(NewN, *G);
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continue;
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}
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// Enqueue nodes to the worklist that were marked during pass 1.
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if (Pass1.count(*I))
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WL2.push_back(*I);
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}
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}
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return G;
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}
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void InterExplodedGraphMap::anchor() { }
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ExplodedNode*
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InterExplodedGraphMap::getMappedNode(const ExplodedNode *N) const {
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llvm::DenseMap<const ExplodedNode*, ExplodedNode*>::const_iterator I =
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M.find(N);
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return I == M.end() ? 0 : I->second;
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}
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