550 lines
16 KiB
C++
550 lines
16 KiB
C++
//==- GRCoreEngine.cpp - Path-Sensitive Dataflow Engine ------------*- 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 a generic engine for intraprocedural, path-sensitive,
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// dataflow analysis via graph reachability engine.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/Analysis/PathSensitive/GRCoreEngine.h"
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#include "clang/AST/Expr.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/ADT/DenseMap.h"
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#include <vector>
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#include <queue>
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using llvm::cast;
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using llvm::isa;
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using namespace clang;
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//===----------------------------------------------------------------------===//
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// Worklist classes for exploration of reachable states.
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//===----------------------------------------------------------------------===//
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namespace {
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class VISIBILITY_HIDDEN DFS : public GRWorkList {
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llvm::SmallVector<GRWorkListUnit,20> Stack;
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public:
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virtual bool hasWork() const {
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return !Stack.empty();
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}
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virtual void Enqueue(const GRWorkListUnit& U) {
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Stack.push_back(U);
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}
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virtual GRWorkListUnit Dequeue() {
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assert (!Stack.empty());
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const GRWorkListUnit& U = Stack.back();
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Stack.pop_back(); // This technically "invalidates" U, but we are fine.
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return U;
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}
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};
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} // end anonymous namespace
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// Place the dstor for GRWorkList here because it contains virtual member
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// functions, and we the code for the dstor generated in one compilation unit.
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GRWorkList::~GRWorkList() {}
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GRWorkList* GRWorkList::MakeDFS() { return new DFS(); }
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namespace {
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class VISIBILITY_HIDDEN BFSBlockDFSContents : public GRWorkList {
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std::queue<GRWorkListUnit> Queue;
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llvm::SmallVector<GRWorkListUnit,20> Stack;
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public:
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virtual bool hasWork() const {
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return !Queue.empty() || !Stack.empty();
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}
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virtual void Enqueue(const GRWorkListUnit& U) {
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if (isa<BlockEntrance>(U.getNode()->getLocation()))
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Queue.push(U);
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else
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Stack.push_back(U);
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}
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virtual GRWorkListUnit Dequeue() {
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// Process all basic blocks to completion.
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if (!Stack.empty()) {
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const GRWorkListUnit& U = Stack.back();
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Stack.pop_back(); // This technically "invalidates" U, but we are fine.
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return U;
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}
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assert(!Queue.empty());
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// Don't use const reference. The subsequent pop_back() might make it
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// unsafe.
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GRWorkListUnit U = Queue.front();
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Queue.pop();
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return U;
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}
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};
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} // end anonymous namespace
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GRWorkList* GRWorkList::MakeBFSBlockDFSContents() {
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return new BFSBlockDFSContents();
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}
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//===----------------------------------------------------------------------===//
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// Core analysis engine.
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//===----------------------------------------------------------------------===//
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/// ExecuteWorkList - Run the worklist algorithm for a maximum number of steps.
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bool GRCoreEngineImpl::ExecuteWorkList(unsigned Steps) {
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if (G->num_roots() == 0) { // Initialize the analysis by constructing
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// the root if none exists.
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CFGBlock* Entry = &getCFG().getEntry();
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assert (Entry->empty() &&
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"Entry block must be empty.");
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assert (Entry->succ_size() == 1 &&
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"Entry block must have 1 successor.");
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// Get the solitary successor.
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CFGBlock* Succ = *(Entry->succ_begin());
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// Construct an edge representing the
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// starting location in the function.
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BlockEdge StartLoc(Entry, Succ);
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// Set the current block counter to being empty.
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WList->setBlockCounter(BCounterFactory.GetEmptyCounter());
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// Generate the root.
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GenerateNode(StartLoc, getInitialState(), 0);
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}
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while (Steps && WList->hasWork()) {
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--Steps;
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const GRWorkListUnit& WU = WList->Dequeue();
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// Set the current block counter.
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WList->setBlockCounter(WU.getBlockCounter());
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// Retrieve the node.
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ExplodedNodeImpl* Node = WU.getNode();
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// Dispatch on the location type.
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switch (Node->getLocation().getKind()) {
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case ProgramPoint::BlockEdgeKind:
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HandleBlockEdge(cast<BlockEdge>(Node->getLocation()), Node);
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break;
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case ProgramPoint::BlockEntranceKind:
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HandleBlockEntrance(cast<BlockEntrance>(Node->getLocation()), Node);
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break;
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case ProgramPoint::BlockExitKind:
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assert (false && "BlockExit location never occur in forward analysis.");
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break;
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default:
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assert(isa<PostStmt>(Node->getLocation()));
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HandlePostStmt(cast<PostStmt>(Node->getLocation()), WU.getBlock(),
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WU.getIndex(), Node);
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break;
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}
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}
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return WList->hasWork();
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}
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void GRCoreEngineImpl::HandleBlockEdge(const BlockEdge& L,
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ExplodedNodeImpl* Pred) {
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CFGBlock* Blk = L.getDst();
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// Check if we are entering the EXIT block.
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if (Blk == &getCFG().getExit()) {
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assert (getCFG().getExit().size() == 0
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&& "EXIT block cannot contain Stmts.");
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// Process the final state transition.
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GREndPathNodeBuilderImpl Builder(Blk, Pred, this);
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ProcessEndPath(Builder);
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// This path is done. Don't enqueue any more nodes.
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return;
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}
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// FIXME: Should we allow ProcessBlockEntrance to also manipulate state?
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if (ProcessBlockEntrance(Blk, Pred->State, WList->getBlockCounter()))
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GenerateNode(BlockEntrance(Blk), Pred->State, Pred);
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}
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void GRCoreEngineImpl::HandleBlockEntrance(const BlockEntrance& L,
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ExplodedNodeImpl* Pred) {
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// Increment the block counter.
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GRBlockCounter Counter = WList->getBlockCounter();
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Counter = BCounterFactory.IncrementCount(Counter, L.getBlock()->getBlockID());
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WList->setBlockCounter(Counter);
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// Process the entrance of the block.
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if (Stmt* S = L.getFirstStmt()) {
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GRStmtNodeBuilderImpl Builder(L.getBlock(), 0, Pred, this);
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ProcessStmt(S, Builder);
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}
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else
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HandleBlockExit(L.getBlock(), Pred);
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}
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GRCoreEngineImpl::~GRCoreEngineImpl() {
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delete WList;
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}
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void GRCoreEngineImpl::HandleBlockExit(CFGBlock * B, ExplodedNodeImpl* Pred) {
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if (Stmt* Term = B->getTerminator()) {
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switch (Term->getStmtClass()) {
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default:
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assert(false && "Analysis for this terminator not implemented.");
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break;
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case Stmt::BinaryOperatorClass: // '&&' and '||'
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HandleBranch(cast<BinaryOperator>(Term)->getLHS(), Term, B, Pred);
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return;
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case Stmt::ConditionalOperatorClass:
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HandleBranch(cast<ConditionalOperator>(Term)->getCond(), Term, B, Pred);
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return;
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// FIXME: Use constant-folding in CFG construction to simplify this
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// case.
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case Stmt::ChooseExprClass:
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HandleBranch(cast<ChooseExpr>(Term)->getCond(), Term, B, Pred);
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return;
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case Stmt::DoStmtClass:
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HandleBranch(cast<DoStmt>(Term)->getCond(), Term, B, Pred);
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return;
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case Stmt::ForStmtClass:
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HandleBranch(cast<ForStmt>(Term)->getCond(), Term, B, Pred);
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return;
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case Stmt::ContinueStmtClass:
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case Stmt::BreakStmtClass:
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case Stmt::GotoStmtClass:
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break;
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case Stmt::IfStmtClass:
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HandleBranch(cast<IfStmt>(Term)->getCond(), Term, B, Pred);
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return;
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case Stmt::IndirectGotoStmtClass: {
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// Only 1 successor: the indirect goto dispatch block.
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assert (B->succ_size() == 1);
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GRIndirectGotoNodeBuilderImpl
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builder(Pred, B, cast<IndirectGotoStmt>(Term)->getTarget(),
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*(B->succ_begin()), this);
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ProcessIndirectGoto(builder);
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return;
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}
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case Stmt::ObjCForCollectionStmtClass: {
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// In the case of ObjCForCollectionStmt, it appears twice in a CFG:
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//
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// (1) inside a basic block, which represents the binding of the
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// 'element' variable to a value.
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// (2) in a terminator, which represents the branch.
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//
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// For (1), subengines will bind a value (i.e., 0 or 1) indicating
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// whether or not collection contains any more elements. We cannot
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// just test to see if the element is nil because a container can
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// contain nil elements.
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HandleBranch(Term, Term, B, Pred);
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return;
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}
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case Stmt::SwitchStmtClass: {
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GRSwitchNodeBuilderImpl builder(Pred, B,
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cast<SwitchStmt>(Term)->getCond(),
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this);
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ProcessSwitch(builder);
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return;
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}
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case Stmt::WhileStmtClass:
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HandleBranch(cast<WhileStmt>(Term)->getCond(), Term, B, Pred);
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return;
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}
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}
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assert (B->succ_size() == 1 &&
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"Blocks with no terminator should have at most 1 successor.");
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GenerateNode(BlockEdge(B, *(B->succ_begin())), Pred->State, Pred);
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}
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void GRCoreEngineImpl::HandleBranch(Stmt* Cond, Stmt* Term, CFGBlock * B,
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ExplodedNodeImpl* Pred) {
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assert (B->succ_size() == 2);
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GRBranchNodeBuilderImpl Builder(B, *(B->succ_begin()), *(B->succ_begin()+1),
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Pred, this);
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ProcessBranch(Cond, Term, Builder);
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}
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void GRCoreEngineImpl::HandlePostStmt(const PostStmt& L, CFGBlock* B,
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unsigned StmtIdx, ExplodedNodeImpl* Pred) {
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assert (!B->empty());
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if (StmtIdx == B->size())
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HandleBlockExit(B, Pred);
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else {
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GRStmtNodeBuilderImpl Builder(B, StmtIdx, Pred, this);
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ProcessStmt((*B)[StmtIdx], Builder);
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}
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}
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/// GenerateNode - Utility method to generate nodes, hook up successors,
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/// and add nodes to the worklist.
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void GRCoreEngineImpl::GenerateNode(const ProgramPoint& Loc, const void* State,
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ExplodedNodeImpl* Pred) {
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bool IsNew;
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ExplodedNodeImpl* Node = G->getNodeImpl(Loc, State, &IsNew);
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if (Pred)
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Node->addPredecessor(Pred); // Link 'Node' with its predecessor.
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else {
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assert (IsNew);
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G->addRoot(Node); // 'Node' has no predecessor. Make it a root.
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}
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// Only add 'Node' to the worklist if it was freshly generated.
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if (IsNew) WList->Enqueue(Node);
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}
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GRStmtNodeBuilderImpl::GRStmtNodeBuilderImpl(CFGBlock* b, unsigned idx,
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ExplodedNodeImpl* N, GRCoreEngineImpl* e)
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: Eng(*e), B(*b), Idx(idx), Pred(N), LastNode(N) {
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Deferred.insert(N);
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}
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GRStmtNodeBuilderImpl::~GRStmtNodeBuilderImpl() {
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for (DeferredTy::iterator I=Deferred.begin(), E=Deferred.end(); I!=E; ++I)
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if (!(*I)->isSink())
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GenerateAutoTransition(*I);
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}
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void GRStmtNodeBuilderImpl::GenerateAutoTransition(ExplodedNodeImpl* N) {
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assert (!N->isSink());
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PostStmt Loc(getStmt());
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if (Loc == N->getLocation()) {
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// Note: 'N' should be a fresh node because otherwise it shouldn't be
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// a member of Deferred.
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Eng.WList->Enqueue(N, B, Idx+1);
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return;
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}
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bool IsNew;
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ExplodedNodeImpl* Succ = Eng.G->getNodeImpl(Loc, N->State, &IsNew);
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Succ->addPredecessor(N);
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if (IsNew)
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Eng.WList->Enqueue(Succ, B, Idx+1);
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}
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static inline PostStmt GetPostLoc(Stmt* S, ProgramPoint::Kind K) {
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switch (K) {
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default:
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assert(false && "Invalid PostXXXKind.");
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case ProgramPoint::PostStmtKind:
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return PostStmt(S);
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case ProgramPoint::PostLoadKind:
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return PostLoad(S);
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case ProgramPoint::PostUndefLocationCheckFailedKind:
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return PostUndefLocationCheckFailed(S);
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case ProgramPoint::PostLocationChecksSucceedKind:
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return PostLocationChecksSucceed(S);
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case ProgramPoint::PostOutOfBoundsCheckFailedKind:
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return PostOutOfBoundsCheckFailed(S);
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case ProgramPoint::PostNullCheckFailedKind:
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return PostNullCheckFailed(S);
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case ProgramPoint::PostStoreKind:
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return PostStore(S);
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case ProgramPoint::PostPurgeDeadSymbolsKind:
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return PostPurgeDeadSymbols(S);
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}
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}
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ExplodedNodeImpl*
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GRStmtNodeBuilderImpl::generateNodeImpl(Stmt* S, const void* State,
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ExplodedNodeImpl* Pred,
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ProgramPoint::Kind K) {
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return generateNodeImpl(GetPostLoc(S, K), State, Pred);
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}
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ExplodedNodeImpl*
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GRStmtNodeBuilderImpl::generateNodeImpl(PostStmt Loc, const void* State,
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ExplodedNodeImpl* Pred) {
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bool IsNew;
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ExplodedNodeImpl* N = Eng.G->getNodeImpl(Loc, State, &IsNew);
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N->addPredecessor(Pred);
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Deferred.erase(Pred);
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if (IsNew) {
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Deferred.insert(N);
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LastNode = N;
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return N;
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}
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LastNode = NULL;
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return NULL;
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}
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ExplodedNodeImpl* GRBranchNodeBuilderImpl::generateNodeImpl(const void* State,
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bool branch) {
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bool IsNew;
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ExplodedNodeImpl* Succ =
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Eng.G->getNodeImpl(BlockEdge(Src, branch ? DstT : DstF), State, &IsNew);
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Succ->addPredecessor(Pred);
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if (branch) GeneratedTrue = true;
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else GeneratedFalse = true;
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if (IsNew) {
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Deferred.push_back(Succ);
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return Succ;
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}
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return NULL;
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}
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GRBranchNodeBuilderImpl::~GRBranchNodeBuilderImpl() {
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if (!GeneratedTrue) generateNodeImpl(Pred->State, true);
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if (!GeneratedFalse) generateNodeImpl(Pred->State, false);
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for (DeferredTy::iterator I=Deferred.begin(), E=Deferred.end(); I!=E; ++I)
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if (!(*I)->isSink()) Eng.WList->Enqueue(*I);
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}
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ExplodedNodeImpl*
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GRIndirectGotoNodeBuilderImpl::generateNodeImpl(const Iterator& I,
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const void* St,
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bool isSink) {
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bool IsNew;
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ExplodedNodeImpl* Succ =
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Eng.G->getNodeImpl(BlockEdge(Src, I.getBlock()), St, &IsNew);
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Succ->addPredecessor(Pred);
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if (IsNew) {
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if (isSink)
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Succ->markAsSink();
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else
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Eng.WList->Enqueue(Succ);
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return Succ;
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}
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return NULL;
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}
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ExplodedNodeImpl*
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GRSwitchNodeBuilderImpl::generateCaseStmtNodeImpl(const Iterator& I,
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const void* St) {
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bool IsNew;
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ExplodedNodeImpl* Succ = Eng.G->getNodeImpl(BlockEdge(Src, I.getBlock()),
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St, &IsNew);
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Succ->addPredecessor(Pred);
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if (IsNew) {
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Eng.WList->Enqueue(Succ);
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return Succ;
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}
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return NULL;
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}
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ExplodedNodeImpl*
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GRSwitchNodeBuilderImpl::generateDefaultCaseNodeImpl(const void* St,
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bool isSink) {
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// Get the block for the default case.
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assert (Src->succ_rbegin() != Src->succ_rend());
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CFGBlock* DefaultBlock = *Src->succ_rbegin();
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bool IsNew;
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ExplodedNodeImpl* Succ = Eng.G->getNodeImpl(BlockEdge(Src, DefaultBlock),
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St, &IsNew);
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Succ->addPredecessor(Pred);
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if (IsNew) {
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if (isSink)
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Succ->markAsSink();
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else
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Eng.WList->Enqueue(Succ);
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return Succ;
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}
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return NULL;
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}
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GREndPathNodeBuilderImpl::~GREndPathNodeBuilderImpl() {
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// Auto-generate an EOP node if one has not been generated.
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if (!HasGeneratedNode) generateNodeImpl(Pred->State);
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}
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ExplodedNodeImpl* GREndPathNodeBuilderImpl::generateNodeImpl(const void* State){
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HasGeneratedNode = true;
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bool IsNew;
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ExplodedNodeImpl* Node =
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Eng.G->getNodeImpl(BlockEntrance(&B), State, &IsNew);
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Node->addPredecessor(Pred);
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if (IsNew) {
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Node->markAsSink();
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Eng.G->addEndOfPath(Node);
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return Node;
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}
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return NULL;
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}
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