1 //===--- LoopWidening.cpp - Widen loops -------------------------*- C++ -*-===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 /// This file contains functions which are used to widen loops. A loop may be
10 /// widened to approximate the exit state(s), without analyzing every
11 /// iteration. The widening is done by invalidating anything which might be
12 /// modified by the body of the loop.
14 //===----------------------------------------------------------------------===//
16 #include "clang/AST/AST.h"
17 #include "clang/ASTMatchers/ASTMatchFinder.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/LoopWidening.h"
21 using namespace clang;
23 using namespace clang::ast_matchers;
25 const auto MatchRef = "matchref";
27 /// Return the loops condition Stmt or NULL if LoopStmt is not a loop
28 static const Expr *getLoopCondition(const Stmt *LoopStmt) {
29 switch (LoopStmt->getStmtClass()) {
32 case Stmt::ForStmtClass:
33 return cast<ForStmt>(LoopStmt)->getCond();
34 case Stmt::WhileStmtClass:
35 return cast<WhileStmt>(LoopStmt)->getCond();
36 case Stmt::DoStmtClass:
37 return cast<DoStmt>(LoopStmt)->getCond();
44 ProgramStateRef getWidenedLoopState(ProgramStateRef PrevState,
45 const LocationContext *LCtx,
46 unsigned BlockCount, const Stmt *LoopStmt) {
48 assert(isa<ForStmt>(LoopStmt) || isa<WhileStmt>(LoopStmt) ||
49 isa<DoStmt>(LoopStmt));
51 // Invalidate values in the current state.
52 // TODO Make this more conservative by only invalidating values that might
53 // be modified by the body of the loop.
54 // TODO Nested loops are currently widened as a result of the invalidation
55 // being so inprecise. When the invalidation is improved, the handling
56 // of nested loops will also need to be improved.
57 ASTContext &ASTCtx = LCtx->getAnalysisDeclContext()->getASTContext();
58 const StackFrameContext *STC = LCtx->getStackFrame();
59 MemRegionManager &MRMgr = PrevState->getStateManager().getRegionManager();
60 const MemRegion *Regions[] = {MRMgr.getStackLocalsRegion(STC),
61 MRMgr.getStackArgumentsRegion(STC),
62 MRMgr.getGlobalsRegion()};
63 RegionAndSymbolInvalidationTraits ITraits;
64 for (auto *Region : Regions) {
65 ITraits.setTrait(Region,
66 RegionAndSymbolInvalidationTraits::TK_EntireMemSpace);
69 // References should not be invalidated.
70 auto Matches = match(findAll(stmt(hasDescendant(varDecl(hasType(referenceType())).bind(MatchRef)))),
71 *LCtx->getDecl()->getBody(), ASTCtx);
72 for (BoundNodes Match : Matches) {
73 const VarDecl *VD = Match.getNodeAs<VarDecl>(MatchRef);
75 const VarRegion *VarMem = MRMgr.getVarRegion(VD, LCtx);
76 ITraits.setTrait(VarMem,
77 RegionAndSymbolInvalidationTraits::TK_PreserveContents);
81 // 'this' pointer is not an lvalue, we should not invalidate it. If the loop
82 // is located in a method, constructor or destructor, the value of 'this'
83 // pointer should remain unchanged. Ignore static methods, since they do not
84 // have 'this' pointers.
85 const CXXMethodDecl *CXXMD = dyn_cast<CXXMethodDecl>(STC->getDecl());
86 if (CXXMD && !CXXMD->isStatic()) {
87 const CXXThisRegion *ThisR =
88 MRMgr.getCXXThisRegion(CXXMD->getThisType(), STC);
89 ITraits.setTrait(ThisR,
90 RegionAndSymbolInvalidationTraits::TK_PreserveContents);
93 return PrevState->invalidateRegions(Regions, getLoopCondition(LoopStmt),
94 BlockCount, LCtx, true, nullptr, nullptr,
98 } // end namespace ento
99 } // end namespace clang