102 lines
4.0 KiB
C++
102 lines
4.0 KiB
C++
//===--- LoopWidening.cpp - Widen loops -------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// This file contains functions which are used to widen loops. A loop may be
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/// widened to approximate the exit state(s), without analyzing every
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/// iteration. The widening is done by invalidating anything which might be
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/// modified by the body of the loop.
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///
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//===----------------------------------------------------------------------===//
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#include "clang/AST/AST.h"
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#include "clang/ASTMatchers/ASTMatchFinder.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/LoopWidening.h"
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using namespace clang;
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using namespace ento;
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using namespace clang::ast_matchers;
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const auto MatchRef = "matchref";
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/// Return the loops condition Stmt or NULL if LoopStmt is not a loop
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static const Expr *getLoopCondition(const Stmt *LoopStmt) {
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switch (LoopStmt->getStmtClass()) {
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default:
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return nullptr;
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case Stmt::ForStmtClass:
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return cast<ForStmt>(LoopStmt)->getCond();
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case Stmt::WhileStmtClass:
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return cast<WhileStmt>(LoopStmt)->getCond();
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case Stmt::DoStmtClass:
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return cast<DoStmt>(LoopStmt)->getCond();
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}
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}
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namespace clang {
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namespace ento {
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ProgramStateRef getWidenedLoopState(ProgramStateRef PrevState,
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const LocationContext *LCtx,
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unsigned BlockCount, const Stmt *LoopStmt) {
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assert(isa<ForStmt>(LoopStmt) || isa<WhileStmt>(LoopStmt) ||
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isa<DoStmt>(LoopStmt));
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// Invalidate values in the current state.
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// TODO Make this more conservative by only invalidating values that might
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// be modified by the body of the loop.
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// TODO Nested loops are currently widened as a result of the invalidation
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// being so inprecise. When the invalidation is improved, the handling
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// of nested loops will also need to be improved.
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ASTContext &ASTCtx = LCtx->getAnalysisDeclContext()->getASTContext();
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const StackFrameContext *STC = LCtx->getStackFrame();
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MemRegionManager &MRMgr = PrevState->getStateManager().getRegionManager();
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const MemRegion *Regions[] = {MRMgr.getStackLocalsRegion(STC),
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MRMgr.getStackArgumentsRegion(STC),
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MRMgr.getGlobalsRegion()};
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RegionAndSymbolInvalidationTraits ITraits;
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for (auto *Region : Regions) {
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ITraits.setTrait(Region,
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RegionAndSymbolInvalidationTraits::TK_EntireMemSpace);
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}
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// References should not be invalidated.
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auto Matches = match(
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findAll(stmt(hasDescendant(
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varDecl(hasType(hasCanonicalType(referenceType()))).bind(MatchRef)))),
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*LCtx->getDecl()->getBody(), ASTCtx);
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for (BoundNodes Match : Matches) {
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const VarDecl *VD = Match.getNodeAs<VarDecl>(MatchRef);
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assert(VD);
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const VarRegion *VarMem = MRMgr.getVarRegion(VD, LCtx);
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ITraits.setTrait(VarMem,
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RegionAndSymbolInvalidationTraits::TK_PreserveContents);
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}
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// 'this' pointer is not an lvalue, we should not invalidate it. If the loop
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// is located in a method, constructor or destructor, the value of 'this'
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// pointer should remain unchanged. Ignore static methods, since they do not
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// have 'this' pointers.
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const CXXMethodDecl *CXXMD = dyn_cast<CXXMethodDecl>(STC->getDecl());
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if (CXXMD && !CXXMD->isStatic()) {
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const CXXThisRegion *ThisR =
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MRMgr.getCXXThisRegion(CXXMD->getThisType(), STC);
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ITraits.setTrait(ThisR,
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RegionAndSymbolInvalidationTraits::TK_PreserveContents);
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}
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return PrevState->invalidateRegions(Regions, getLoopCondition(LoopStmt),
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BlockCount, LCtx, true, nullptr, nullptr,
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&ITraits);
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}
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} // end namespace ento
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} // end namespace clang
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