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