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//===--- CFG.cpp - Classes for representing and building CFGs----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the CFG and CFGBuilder classes for representing and
// building Control-Flow Graphs (CFGs) from ASTs.
//
//===----------------------------------------------------------------------===//
#include "clang/Analysis/CFG.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Attr.h"
#include "clang/AST/CharUnits.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/PrettyPrinter.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/Basic/Builtins.h"
#include "llvm/ADT/DenseMap.h"
#include <memory>
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/GraphWriter.h"
#include "llvm/Support/SaveAndRestore.h"
using namespace clang;
namespace {
static SourceLocation GetEndLoc(Decl *D) {
if (VarDecl *VD = dyn_cast<VarDecl>(D))
if (Expr *Ex = VD->getInit())
return Ex->getSourceRange().getEnd();
return D->getLocation();
}
/// Helper for tryNormalizeBinaryOperator. Attempts to extract an IntegerLiteral
/// or EnumConstantDecl from the given Expr. If it fails, returns nullptr.
const Expr *tryTransformToIntOrEnumConstant(const Expr *E) {
E = E->IgnoreParens();
if (isa<IntegerLiteral>(E))
return E;
if (auto *DR = dyn_cast<DeclRefExpr>(E->IgnoreParenImpCasts()))
return isa<EnumConstantDecl>(DR->getDecl()) ? DR : nullptr;
return nullptr;
}
/// Tries to interpret a binary operator into `Decl Op Expr` form, if Expr is
/// an integer literal or an enum constant.
///
/// If this fails, at least one of the returned DeclRefExpr or Expr will be
/// null.
static std::tuple<const DeclRefExpr *, BinaryOperatorKind, const Expr *>
tryNormalizeBinaryOperator(const BinaryOperator *B) {
BinaryOperatorKind Op = B->getOpcode();
const Expr *MaybeDecl = B->getLHS();
const Expr *Constant = tryTransformToIntOrEnumConstant(B->getRHS());
// Expr looked like `0 == Foo` instead of `Foo == 0`
if (Constant == nullptr) {
// Flip the operator
if (Op == BO_GT)
Op = BO_LT;
else if (Op == BO_GE)
Op = BO_LE;
else if (Op == BO_LT)
Op = BO_GT;
else if (Op == BO_LE)
Op = BO_GE;
MaybeDecl = B->getRHS();
Constant = tryTransformToIntOrEnumConstant(B->getLHS());
}
auto *D = dyn_cast<DeclRefExpr>(MaybeDecl->IgnoreParenImpCasts());
return std::make_tuple(D, Op, Constant);
}
/// For an expression `x == Foo && x == Bar`, this determines whether the
/// `Foo` and `Bar` are either of the same enumeration type, or both integer
/// literals.
///
/// It's an error to pass this arguments that are not either IntegerLiterals
/// or DeclRefExprs (that have decls of type EnumConstantDecl)
static bool areExprTypesCompatible(const Expr *E1, const Expr *E2) {
// User intent isn't clear if they're mixing int literals with enum
// constants.
if (isa<IntegerLiteral>(E1) != isa<IntegerLiteral>(E2))
return false;
// Integer literal comparisons, regardless of literal type, are acceptable.
if (isa<IntegerLiteral>(E1))
return true;
// IntegerLiterals are handled above and only EnumConstantDecls are expected
// beyond this point
assert(isa<DeclRefExpr>(E1) && isa<DeclRefExpr>(E2));
auto *Decl1 = cast<DeclRefExpr>(E1)->getDecl();
auto *Decl2 = cast<DeclRefExpr>(E2)->getDecl();
assert(isa<EnumConstantDecl>(Decl1) && isa<EnumConstantDecl>(Decl2));
const DeclContext *DC1 = Decl1->getDeclContext();
const DeclContext *DC2 = Decl2->getDeclContext();
assert(isa<EnumDecl>(DC1) && isa<EnumDecl>(DC2));
return DC1 == DC2;
}
class CFGBuilder;
/// The CFG builder uses a recursive algorithm to build the CFG. When
/// we process an expression, sometimes we know that we must add the
/// subexpressions as block-level expressions. For example:
///
/// exp1 || exp2
///
/// When processing the '||' expression, we know that exp1 and exp2
/// need to be added as block-level expressions, even though they
/// might not normally need to be. AddStmtChoice records this
/// contextual information. If AddStmtChoice is 'NotAlwaysAdd', then
/// the builder has an option not to add a subexpression as a
/// block-level expression.
///
class AddStmtChoice {
public:
enum Kind { NotAlwaysAdd = 0, AlwaysAdd = 1 };
AddStmtChoice(Kind a_kind = NotAlwaysAdd) : kind(a_kind) {}
bool alwaysAdd(CFGBuilder &builder,
const Stmt *stmt) const;
/// Return a copy of this object, except with the 'always-add' bit
/// set as specified.
AddStmtChoice withAlwaysAdd(bool alwaysAdd) const {
return AddStmtChoice(alwaysAdd ? AlwaysAdd : NotAlwaysAdd);
}
private:
Kind kind;
};
/// LocalScope - Node in tree of local scopes created for C++ implicit
/// destructor calls generation. It contains list of automatic variables
/// declared in the scope and link to position in previous scope this scope
/// began in.
///
/// The process of creating local scopes is as follows:
/// - Init CFGBuilder::ScopePos with invalid position (equivalent for null),
/// - Before processing statements in scope (e.g. CompoundStmt) create
/// LocalScope object using CFGBuilder::ScopePos as link to previous scope
/// and set CFGBuilder::ScopePos to the end of new scope,
/// - On every occurrence of VarDecl increase CFGBuilder::ScopePos if it points
/// at this VarDecl,
/// - For every normal (without jump) end of scope add to CFGBlock destructors
/// for objects in the current scope,
/// - For every jump add to CFGBlock destructors for objects
/// between CFGBuilder::ScopePos and local scope position saved for jump
/// target. Thanks to C++ restrictions on goto jumps we can be sure that
/// jump target position will be on the path to root from CFGBuilder::ScopePos
/// (adding any variable that doesn't need constructor to be called to
/// LocalScope can break this assumption),
///
class LocalScope {
public:
typedef BumpVector<VarDecl*> AutomaticVarsTy;
/// const_iterator - Iterates local scope backwards and jumps to previous
/// scope on reaching the beginning of currently iterated scope.
class const_iterator {
const LocalScope* Scope;
/// VarIter is guaranteed to be greater then 0 for every valid iterator.
/// Invalid iterator (with null Scope) has VarIter equal to 0.
unsigned VarIter;
public:
/// Create invalid iterator. Dereferencing invalid iterator is not allowed.
/// Incrementing invalid iterator is allowed and will result in invalid
/// iterator.
const_iterator()
: Scope(nullptr), VarIter(0) {}
/// Create valid iterator. In case when S.Prev is an invalid iterator and
/// I is equal to 0, this will create invalid iterator.
const_iterator(const LocalScope& S, unsigned I)
: Scope(&S), VarIter(I) {
// Iterator to "end" of scope is not allowed. Handle it by going up
// in scopes tree possibly up to invalid iterator in the root.
if (VarIter == 0 && Scope)
*this = Scope->Prev;
}
VarDecl *const* operator->() const {
assert (Scope && "Dereferencing invalid iterator is not allowed");
assert (VarIter != 0 && "Iterator has invalid value of VarIter member");
return &Scope->Vars[VarIter - 1];
}
VarDecl *operator*() const {
return *this->operator->();
}
const_iterator &operator++() {
if (!Scope)
return *this;
assert (VarIter != 0 && "Iterator has invalid value of VarIter member");
--VarIter;
if (VarIter == 0)
*this = Scope->Prev;
return *this;
}
const_iterator operator++(int) {
const_iterator P = *this;
++*this;
return P;
}
bool operator==(const const_iterator &rhs) const {
return Scope == rhs.Scope && VarIter == rhs.VarIter;
}
bool operator!=(const const_iterator &rhs) const {
return !(*this == rhs);
}
explicit operator bool() const {
return *this != const_iterator();
}
int distance(const_iterator L);
};
friend class const_iterator;
private:
BumpVectorContext ctx;
/// Automatic variables in order of declaration.
AutomaticVarsTy Vars;
/// Iterator to variable in previous scope that was declared just before
/// begin of this scope.
const_iterator Prev;
public:
/// Constructs empty scope linked to previous scope in specified place.
LocalScope(BumpVectorContext ctx, const_iterator P)
: ctx(std::move(ctx)), Vars(this->ctx, 4), Prev(P) {}
/// Begin of scope in direction of CFG building (backwards).
const_iterator begin() const { return const_iterator(*this, Vars.size()); }
void addVar(VarDecl *VD) {
Vars.push_back(VD, ctx);
}
};
/// distance - Calculates distance from this to L. L must be reachable from this
/// (with use of ++ operator). Cost of calculating the distance is linear w.r.t.
/// number of scopes between this and L.
int LocalScope::const_iterator::distance(LocalScope::const_iterator L) {
int D = 0;
const_iterator F = *this;
while (F.Scope != L.Scope) {
assert (F != const_iterator()
&& "L iterator is not reachable from F iterator.");
D += F.VarIter;
F = F.Scope->Prev;
}
D += F.VarIter - L.VarIter;
return D;
}
/// Structure for specifying position in CFG during its build process. It
/// consists of CFGBlock that specifies position in CFG and
/// LocalScope::const_iterator that specifies position in LocalScope graph.
struct BlockScopePosPair {
BlockScopePosPair() : block(nullptr) {}
BlockScopePosPair(CFGBlock *b, LocalScope::const_iterator scopePos)
: block(b), scopePosition(scopePos) {}
CFGBlock *block;
LocalScope::const_iterator scopePosition;
};
/// TryResult - a class representing a variant over the values
/// 'true', 'false', or 'unknown'. This is returned by tryEvaluateBool,
/// and is used by the CFGBuilder to decide if a branch condition
/// can be decided up front during CFG construction.
class TryResult {
int X;
public:
TryResult(bool b) : X(b ? 1 : 0) {}
TryResult() : X(-1) {}
bool isTrue() const { return X == 1; }
bool isFalse() const { return X == 0; }
bool isKnown() const { return X >= 0; }
void negate() {
assert(isKnown());
X ^= 0x1;
}
};
TryResult bothKnownTrue(TryResult R1, TryResult R2) {
if (!R1.isKnown() || !R2.isKnown())
return TryResult();
return TryResult(R1.isTrue() && R2.isTrue());
}
class reverse_children {
llvm::SmallVector<Stmt *, 12> childrenBuf;
ArrayRef<Stmt*> children;
public:
reverse_children(Stmt *S);
typedef ArrayRef<Stmt*>::reverse_iterator iterator;
iterator begin() const { return children.rbegin(); }
iterator end() const { return children.rend(); }
};
reverse_children::reverse_children(Stmt *S) {
if (CallExpr *CE = dyn_cast<CallExpr>(S)) {
children = CE->getRawSubExprs();
return;
}
switch (S->getStmtClass()) {
// Note: Fill in this switch with more cases we want to optimize.
case Stmt::InitListExprClass: {
InitListExpr *IE = cast<InitListExpr>(S);
children = llvm::makeArrayRef(reinterpret_cast<Stmt**>(IE->getInits()),
IE->getNumInits());
return;
}
default:
break;
}
// Default case for all other statements.
for (Stmt *SubStmt : S->children())
childrenBuf.push_back(SubStmt);
// This needs to be done *after* childrenBuf has been populated.
children = childrenBuf;
}
/// CFGBuilder - This class implements CFG construction from an AST.
/// The builder is stateful: an instance of the builder should be used to only
/// construct a single CFG.
///
/// Example usage:
///
/// CFGBuilder builder;
/// std::unique_ptr<CFG> cfg = builder.buildCFG(decl, stmt1);
///
/// CFG construction is done via a recursive walk of an AST. We actually parse
/// the AST in reverse order so that the successor of a basic block is
/// constructed prior to its predecessor. This allows us to nicely capture
/// implicit fall-throughs without extra basic blocks.
///
class CFGBuilder {
typedef BlockScopePosPair JumpTarget;
typedef BlockScopePosPair JumpSource;
ASTContext *Context;
std::unique_ptr<CFG> cfg;
CFGBlock *Block;
CFGBlock *Succ;
JumpTarget ContinueJumpTarget;
JumpTarget BreakJumpTarget;
CFGBlock *SwitchTerminatedBlock;
CFGBlock *DefaultCaseBlock;
CFGBlock *TryTerminatedBlock;
// Current position in local scope.
LocalScope::const_iterator ScopePos;
// LabelMap records the mapping from Label expressions to their jump targets.
typedef llvm::DenseMap<LabelDecl*, JumpTarget> LabelMapTy;
LabelMapTy LabelMap;
// A list of blocks that end with a "goto" that must be backpatched to their
// resolved targets upon completion of CFG construction.
typedef std::vector<JumpSource> BackpatchBlocksTy;
BackpatchBlocksTy BackpatchBlocks;
// A list of labels whose address has been taken (for indirect gotos).
typedef llvm::SmallPtrSet<LabelDecl*, 5> LabelSetTy;
LabelSetTy AddressTakenLabels;
bool badCFG;
const CFG::BuildOptions &BuildOpts;
// State to track for building switch statements.
bool switchExclusivelyCovered;
Expr::EvalResult *switchCond;
CFG::BuildOptions::ForcedBlkExprs::value_type *cachedEntry;
const Stmt *lastLookup;
// Caches boolean evaluations of expressions to avoid multiple re-evaluations
// during construction of branches for chained logical operators.
typedef llvm::DenseMap<Expr *, TryResult> CachedBoolEvalsTy;
CachedBoolEvalsTy CachedBoolEvals;
public:
explicit CFGBuilder(ASTContext *astContext,
const CFG::BuildOptions &buildOpts)
: Context(astContext), cfg(new CFG()), // crew a new CFG
Block(nullptr), Succ(nullptr),
SwitchTerminatedBlock(nullptr), DefaultCaseBlock(nullptr),
TryTerminatedBlock(nullptr), badCFG(false), BuildOpts(buildOpts),
switchExclusivelyCovered(false), switchCond(nullptr),
cachedEntry(nullptr), lastLookup(nullptr) {}
// buildCFG - Used by external clients to construct the CFG.
std::unique_ptr<CFG> buildCFG(const Decl *D, Stmt *Statement);
bool alwaysAdd(const Stmt *stmt);
private:
// Visitors to walk an AST and construct the CFG.
CFGBlock *VisitAddrLabelExpr(AddrLabelExpr *A, AddStmtChoice asc);
CFGBlock *VisitBinaryOperator(BinaryOperator *B, AddStmtChoice asc);
CFGBlock *VisitBreakStmt(BreakStmt *B);
CFGBlock *VisitCallExpr(CallExpr *C, AddStmtChoice asc);
CFGBlock *VisitCaseStmt(CaseStmt *C);
CFGBlock *VisitChooseExpr(ChooseExpr *C, AddStmtChoice asc);
CFGBlock *VisitCompoundStmt(CompoundStmt *C);
CFGBlock *VisitConditionalOperator(AbstractConditionalOperator *C,
AddStmtChoice asc);
CFGBlock *VisitContinueStmt(ContinueStmt *C);
CFGBlock *VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E,
AddStmtChoice asc);
CFGBlock *VisitCXXCatchStmt(CXXCatchStmt *S);
CFGBlock *VisitCXXConstructExpr(CXXConstructExpr *C, AddStmtChoice asc);
CFGBlock *VisitCXXNewExpr(CXXNewExpr *DE, AddStmtChoice asc);
CFGBlock *VisitCXXDeleteExpr(CXXDeleteExpr *DE, AddStmtChoice asc);
CFGBlock *VisitCXXForRangeStmt(CXXForRangeStmt *S);
CFGBlock *VisitCXXFunctionalCastExpr(CXXFunctionalCastExpr *E,
AddStmtChoice asc);
CFGBlock *VisitCXXTemporaryObjectExpr(CXXTemporaryObjectExpr *C,
AddStmtChoice asc);
CFGBlock *VisitCXXThrowExpr(CXXThrowExpr *T);
CFGBlock *VisitCXXTryStmt(CXXTryStmt *S);
CFGBlock *VisitDeclStmt(DeclStmt *DS);
CFGBlock *VisitDeclSubExpr(DeclStmt *DS);
CFGBlock *VisitDefaultStmt(DefaultStmt *D);
CFGBlock *VisitDoStmt(DoStmt *D);
CFGBlock *VisitExprWithCleanups(ExprWithCleanups *E, AddStmtChoice asc);
CFGBlock *VisitForStmt(ForStmt *F);
CFGBlock *VisitGotoStmt(GotoStmt *G);
CFGBlock *VisitIfStmt(IfStmt *I);
CFGBlock *VisitImplicitCastExpr(ImplicitCastExpr *E, AddStmtChoice asc);
CFGBlock *VisitIndirectGotoStmt(IndirectGotoStmt *I);
CFGBlock *VisitLabelStmt(LabelStmt *L);
CFGBlock *VisitBlockExpr(BlockExpr *E, AddStmtChoice asc);
CFGBlock *VisitLambdaExpr(LambdaExpr *E, AddStmtChoice asc);
CFGBlock *VisitLogicalOperator(BinaryOperator *B);
std::pair<CFGBlock *, CFGBlock *> VisitLogicalOperator(BinaryOperator *B,
Stmt *Term,
CFGBlock *TrueBlock,
CFGBlock *FalseBlock);
CFGBlock *VisitMemberExpr(MemberExpr *M, AddStmtChoice asc);
CFGBlock *VisitObjCAtCatchStmt(ObjCAtCatchStmt *S);
CFGBlock *VisitObjCAtSynchronizedStmt(ObjCAtSynchronizedStmt *S);
CFGBlock *VisitObjCAtThrowStmt(ObjCAtThrowStmt *S);
CFGBlock *VisitObjCAtTryStmt(ObjCAtTryStmt *S);
CFGBlock *VisitObjCAutoreleasePoolStmt(ObjCAutoreleasePoolStmt *S);
CFGBlock *VisitObjCForCollectionStmt(ObjCForCollectionStmt *S);
CFGBlock *VisitPseudoObjectExpr(PseudoObjectExpr *E);
CFGBlock *VisitReturnStmt(ReturnStmt *R);
CFGBlock *VisitStmtExpr(StmtExpr *S, AddStmtChoice asc);
CFGBlock *VisitSwitchStmt(SwitchStmt *S);
CFGBlock *VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *E,
AddStmtChoice asc);
CFGBlock *VisitUnaryOperator(UnaryOperator *U, AddStmtChoice asc);
CFGBlock *VisitWhileStmt(WhileStmt *W);
CFGBlock *Visit(Stmt *S, AddStmtChoice asc = AddStmtChoice::NotAlwaysAdd);
CFGBlock *VisitStmt(Stmt *S, AddStmtChoice asc);
CFGBlock *VisitChildren(Stmt *S);
CFGBlock *VisitNoRecurse(Expr *E, AddStmtChoice asc);
/// When creating the CFG for temporary destructors, we want to mirror the
/// branch structure of the corresponding constructor calls.
/// Thus, while visiting a statement for temporary destructors, we keep a
/// context to keep track of the following information:
/// - whether a subexpression is executed unconditionally
/// - if a subexpression is executed conditionally, the first
/// CXXBindTemporaryExpr we encounter in that subexpression (which
/// corresponds to the last temporary destructor we have to call for this
/// subexpression) and the CFG block at that point (which will become the
/// successor block when inserting the decision point).
///
/// That way, we can build the branch structure for temporary destructors as
/// follows:
/// 1. If a subexpression is executed unconditionally, we add the temporary
/// destructor calls to the current block.
/// 2. If a subexpression is executed conditionally, when we encounter a
/// CXXBindTemporaryExpr:
/// a) If it is the first temporary destructor call in the subexpression,
/// we remember the CXXBindTemporaryExpr and the current block in the
/// TempDtorContext; we start a new block, and insert the temporary
/// destructor call.
/// b) Otherwise, add the temporary destructor call to the current block.
/// 3. When we finished visiting a conditionally executed subexpression,
/// and we found at least one temporary constructor during the visitation
/// (2.a has executed), we insert a decision block that uses the
/// CXXBindTemporaryExpr as terminator, and branches to the current block
/// if the CXXBindTemporaryExpr was marked executed, and otherwise
/// branches to the stored successor.
struct TempDtorContext {
TempDtorContext()
: IsConditional(false), KnownExecuted(true), Succ(nullptr),
TerminatorExpr(nullptr) {}
TempDtorContext(TryResult KnownExecuted)
: IsConditional(true), KnownExecuted(KnownExecuted), Succ(nullptr),
TerminatorExpr(nullptr) {}
/// Returns whether we need to start a new branch for a temporary destructor
/// call. This is the case when the temporary destructor is
/// conditionally executed, and it is the first one we encounter while
/// visiting a subexpression - other temporary destructors at the same level
/// will be added to the same block and are executed under the same
/// condition.
bool needsTempDtorBranch() const {
return IsConditional && !TerminatorExpr;
}
/// Remember the successor S of a temporary destructor decision branch for
/// the corresponding CXXBindTemporaryExpr E.
void setDecisionPoint(CFGBlock *S, CXXBindTemporaryExpr *E) {
Succ = S;
TerminatorExpr = E;
}
const bool IsConditional;
const TryResult KnownExecuted;
CFGBlock *Succ;
CXXBindTemporaryExpr *TerminatorExpr;
};
// Visitors to walk an AST and generate destructors of temporaries in
// full expression.
CFGBlock *VisitForTemporaryDtors(Stmt *E, bool BindToTemporary,
TempDtorContext &Context);
CFGBlock *VisitChildrenForTemporaryDtors(Stmt *E, TempDtorContext &Context);
CFGBlock *VisitBinaryOperatorForTemporaryDtors(BinaryOperator *E,
TempDtorContext &Context);
CFGBlock *VisitCXXBindTemporaryExprForTemporaryDtors(
CXXBindTemporaryExpr *E, bool BindToTemporary, TempDtorContext &Context);
CFGBlock *VisitConditionalOperatorForTemporaryDtors(
AbstractConditionalOperator *E, bool BindToTemporary,
TempDtorContext &Context);
void InsertTempDtorDecisionBlock(const TempDtorContext &Context,
CFGBlock *FalseSucc = nullptr);
// NYS == Not Yet Supported
CFGBlock *NYS() {
badCFG = true;
return Block;
}
void autoCreateBlock() { if (!Block) Block = createBlock(); }
CFGBlock *createBlock(bool add_successor = true);
CFGBlock *createNoReturnBlock();
CFGBlock *addStmt(Stmt *S) {
return Visit(S, AddStmtChoice::AlwaysAdd);
}
CFGBlock *addInitializer(CXXCtorInitializer *I);
void addAutomaticObjDtors(LocalScope::const_iterator B,
LocalScope::const_iterator E, Stmt *S);
void addImplicitDtorsForDestructor(const CXXDestructorDecl *DD);
// Local scopes creation.
LocalScope* createOrReuseLocalScope(LocalScope* Scope);
void addLocalScopeForStmt(Stmt *S);
LocalScope* addLocalScopeForDeclStmt(DeclStmt *DS,
LocalScope* Scope = nullptr);
LocalScope* addLocalScopeForVarDecl(VarDecl *VD, LocalScope* Scope = nullptr);
void addLocalScopeAndDtors(Stmt *S);
// Interface to CFGBlock - adding CFGElements.
void appendStmt(CFGBlock *B, const Stmt *S) {
if (alwaysAdd(S) && cachedEntry)
cachedEntry->second = B;
// All block-level expressions should have already been IgnoreParens()ed.
assert(!isa<Expr>(S) || cast<Expr>(S)->IgnoreParens() == S);
B->appendStmt(const_cast<Stmt*>(S), cfg->getBumpVectorContext());
}
void appendInitializer(CFGBlock *B, CXXCtorInitializer *I) {
B->appendInitializer(I, cfg->getBumpVectorContext());
}
void appendNewAllocator(CFGBlock *B, CXXNewExpr *NE) {
B->appendNewAllocator(NE, cfg->getBumpVectorContext());
}
void appendBaseDtor(CFGBlock *B, const CXXBaseSpecifier *BS) {
B->appendBaseDtor(BS, cfg->getBumpVectorContext());
}
void appendMemberDtor(CFGBlock *B, FieldDecl *FD) {
B->appendMemberDtor(FD, cfg->getBumpVectorContext());
}
void appendTemporaryDtor(CFGBlock *B, CXXBindTemporaryExpr *E) {
B->appendTemporaryDtor(E, cfg->getBumpVectorContext());
}
void appendAutomaticObjDtor(CFGBlock *B, VarDecl *VD, Stmt *S) {
B->appendAutomaticObjDtor(VD, S, cfg->getBumpVectorContext());
}
void appendDeleteDtor(CFGBlock *B, CXXRecordDecl *RD, CXXDeleteExpr *DE) {
B->appendDeleteDtor(RD, DE, cfg->getBumpVectorContext());
}
void prependAutomaticObjDtorsWithTerminator(CFGBlock *Blk,
LocalScope::const_iterator B, LocalScope::const_iterator E);
void addSuccessor(CFGBlock *B, CFGBlock *S, bool IsReachable = true) {
B->addSuccessor(CFGBlock::AdjacentBlock(S, IsReachable),
cfg->getBumpVectorContext());
}
/// Add a reachable successor to a block, with the alternate variant that is
/// unreachable.
void addSuccessor(CFGBlock *B, CFGBlock *ReachableBlock, CFGBlock *AltBlock) {
B->addSuccessor(CFGBlock::AdjacentBlock(ReachableBlock, AltBlock),
cfg->getBumpVectorContext());
}
/// \brief Find a relational comparison with an expression evaluating to a
/// boolean and a constant other than 0 and 1.
/// e.g. if ((x < y) == 10)
TryResult checkIncorrectRelationalOperator(const BinaryOperator *B) {
const Expr *LHSExpr = B->getLHS()->IgnoreParens();
const Expr *RHSExpr = B->getRHS()->IgnoreParens();
const IntegerLiteral *IntLiteral = dyn_cast<IntegerLiteral>(LHSExpr);
const Expr *BoolExpr = RHSExpr;
bool IntFirst = true;
if (!IntLiteral) {
IntLiteral = dyn_cast<IntegerLiteral>(RHSExpr);
BoolExpr = LHSExpr;
IntFirst = false;
}
if (!IntLiteral || !BoolExpr->isKnownToHaveBooleanValue())
return TryResult();
llvm::APInt IntValue = IntLiteral->getValue();
if ((IntValue == 1) || (IntValue == 0))
return TryResult();
bool IntLarger = IntLiteral->getType()->isUnsignedIntegerType() ||
!IntValue.isNegative();
BinaryOperatorKind Bok = B->getOpcode();
if (Bok == BO_GT || Bok == BO_GE) {
// Always true for 10 > bool and bool > -1
// Always false for -1 > bool and bool > 10
return TryResult(IntFirst == IntLarger);
} else {
// Always true for -1 < bool and bool < 10
// Always false for 10 < bool and bool < -1
return TryResult(IntFirst != IntLarger);
}
}
/// Find an incorrect equality comparison. Either with an expression
/// evaluating to a boolean and a constant other than 0 and 1.
/// e.g. if (!x == 10) or a bitwise and/or operation that always evaluates to
/// true/false e.q. (x & 8) == 4.
TryResult checkIncorrectEqualityOperator(const BinaryOperator *B) {
const Expr *LHSExpr = B->getLHS()->IgnoreParens();
const Expr *RHSExpr = B->getRHS()->IgnoreParens();
const IntegerLiteral *IntLiteral = dyn_cast<IntegerLiteral>(LHSExpr);
const Expr *BoolExpr = RHSExpr;
if (!IntLiteral) {
IntLiteral = dyn_cast<IntegerLiteral>(RHSExpr);
BoolExpr = LHSExpr;
}
if (!IntLiteral)
return TryResult();
const BinaryOperator *BitOp = dyn_cast<BinaryOperator>(BoolExpr);
if (BitOp && (BitOp->getOpcode() == BO_And ||
BitOp->getOpcode() == BO_Or)) {
const Expr *LHSExpr2 = BitOp->getLHS()->IgnoreParens();
const Expr *RHSExpr2 = BitOp->getRHS()->IgnoreParens();
const IntegerLiteral *IntLiteral2 = dyn_cast<IntegerLiteral>(LHSExpr2);
if (!IntLiteral2)
IntLiteral2 = dyn_cast<IntegerLiteral>(RHSExpr2);
if (!IntLiteral2)
return TryResult();
llvm::APInt L1 = IntLiteral->getValue();
llvm::APInt L2 = IntLiteral2->getValue();
if ((BitOp->getOpcode() == BO_And && (L2 & L1) != L1) ||
(BitOp->getOpcode() == BO_Or && (L2 | L1) != L1)) {
if (BuildOpts.Observer)
BuildOpts.Observer->compareBitwiseEquality(B,
B->getOpcode() != BO_EQ);
TryResult(B->getOpcode() != BO_EQ);
}
} else if (BoolExpr->isKnownToHaveBooleanValue()) {
llvm::APInt IntValue = IntLiteral->getValue();
if ((IntValue == 1) || (IntValue == 0)) {
return TryResult();
}
return TryResult(B->getOpcode() != BO_EQ);
}
return TryResult();
}
TryResult analyzeLogicOperatorCondition(BinaryOperatorKind Relation,
const llvm::APSInt &Value1,
const llvm::APSInt &Value2) {
assert(Value1.isSigned() == Value2.isSigned());
switch (Relation) {
default:
return TryResult();
case BO_EQ:
return TryResult(Value1 == Value2);
case BO_NE:
return TryResult(Value1 != Value2);
case BO_LT:
return TryResult(Value1 < Value2);
case BO_LE:
return TryResult(Value1 <= Value2);
case BO_GT:
return TryResult(Value1 > Value2);
case BO_GE:
return TryResult(Value1 >= Value2);
}
}
/// \brief Find a pair of comparison expressions with or without parentheses
/// with a shared variable and constants and a logical operator between them
/// that always evaluates to either true or false.
/// e.g. if (x != 3 || x != 4)
TryResult checkIncorrectLogicOperator(const BinaryOperator *B) {
assert(B->isLogicalOp());
const BinaryOperator *LHS =
dyn_cast<BinaryOperator>(B->getLHS()->IgnoreParens());
const BinaryOperator *RHS =
dyn_cast<BinaryOperator>(B->getRHS()->IgnoreParens());
if (!LHS || !RHS)
return TryResult();
if (!LHS->isComparisonOp() || !RHS->isComparisonOp())
return TryResult();
const DeclRefExpr *Decl1;
const Expr *Expr1;
BinaryOperatorKind BO1;
std::tie(Decl1, BO1, Expr1) = tryNormalizeBinaryOperator(LHS);
if (!Decl1 || !Expr1)
return TryResult();
const DeclRefExpr *Decl2;
const Expr *Expr2;
BinaryOperatorKind BO2;
std::tie(Decl2, BO2, Expr2) = tryNormalizeBinaryOperator(RHS);
if (!Decl2 || !Expr2)
return TryResult();
// Check that it is the same variable on both sides.
if (Decl1->getDecl() != Decl2->getDecl())
return TryResult();
// Make sure the user's intent is clear (e.g. they're comparing against two
// int literals, or two things from the same enum)
if (!areExprTypesCompatible(Expr1, Expr2))
return TryResult();
llvm::APSInt L1, L2;
if (!Expr1->EvaluateAsInt(L1, *Context) ||
!Expr2->EvaluateAsInt(L2, *Context))
return TryResult();
// Can't compare signed with unsigned or with different bit width.
if (L1.isSigned() != L2.isSigned() || L1.getBitWidth() != L2.getBitWidth())
return TryResult();
// Values that will be used to determine if result of logical
// operator is always true/false
const llvm::APSInt Values[] = {
// Value less than both Value1 and Value2
llvm::APSInt::getMinValue(L1.getBitWidth(), L1.isUnsigned()),
// L1
L1,
// Value between Value1 and Value2
((L1 < L2) ? L1 : L2) + llvm::APSInt(llvm::APInt(L1.getBitWidth(), 1),
L1.isUnsigned()),
// L2
L2,
// Value greater than both Value1 and Value2
llvm::APSInt::getMaxValue(L1.getBitWidth(), L1.isUnsigned()),
};
// Check whether expression is always true/false by evaluating the following
// * variable x is less than the smallest literal.
// * variable x is equal to the smallest literal.
// * Variable x is between smallest and largest literal.
// * Variable x is equal to the largest literal.
// * Variable x is greater than largest literal.
bool AlwaysTrue = true, AlwaysFalse = true;
for (const llvm::APSInt &Value : Values) {
TryResult Res1, Res2;
Res1 = analyzeLogicOperatorCondition(BO1, Value, L1);
Res2 = analyzeLogicOperatorCondition(BO2, Value, L2);
if (!Res1.isKnown() || !Res2.isKnown())
return TryResult();
if (B->getOpcode() == BO_LAnd) {
AlwaysTrue &= (Res1.isTrue() && Res2.isTrue());
AlwaysFalse &= !(Res1.isTrue() && Res2.isTrue());
} else {
AlwaysTrue &= (Res1.isTrue() || Res2.isTrue());
AlwaysFalse &= !(Res1.isTrue() || Res2.isTrue());
}
}
if (AlwaysTrue || AlwaysFalse) {
if (BuildOpts.Observer)
BuildOpts.Observer->compareAlwaysTrue(B, AlwaysTrue);
return TryResult(AlwaysTrue);
}
return TryResult();
}
/// Try and evaluate an expression to an integer constant.
bool tryEvaluate(Expr *S, Expr::EvalResult &outResult) {
if (!BuildOpts.PruneTriviallyFalseEdges)
return false;
return !S->isTypeDependent() &&
!S->isValueDependent() &&
S->EvaluateAsRValue(outResult, *Context);
}
/// tryEvaluateBool - Try and evaluate the Stmt and return 0 or 1
/// if we can evaluate to a known value, otherwise return -1.
TryResult tryEvaluateBool(Expr *S) {
if (!BuildOpts.PruneTriviallyFalseEdges ||
S->isTypeDependent() || S->isValueDependent())
return TryResult();
if (BinaryOperator *Bop = dyn_cast<BinaryOperator>(S)) {
if (Bop->isLogicalOp()) {
// Check the cache first.
CachedBoolEvalsTy::iterator I = CachedBoolEvals.find(S);
if (I != CachedBoolEvals.end())
return I->second; // already in map;
// Retrieve result at first, or the map might be updated.
TryResult Result = evaluateAsBooleanConditionNoCache(S);
CachedBoolEvals[S] = Result; // update or insert
return Result;
}
else {
switch (Bop->getOpcode()) {
default: break;
// For 'x & 0' and 'x * 0', we can determine that
// the value is always false.
case BO_Mul:
case BO_And: {
// If either operand is zero, we know the value
// must be false.
llvm::APSInt IntVal;
if (Bop->getLHS()->EvaluateAsInt(IntVal, *Context)) {
if (!IntVal.getBoolValue()) {
return TryResult(false);
}
}
if (Bop->getRHS()->EvaluateAsInt(IntVal, *Context)) {
if (!IntVal.getBoolValue()) {
return TryResult(false);
}
}
}
break;
}
}
}
return evaluateAsBooleanConditionNoCache(S);
}
/// \brief Evaluate as boolean \param E without using the cache.
TryResult evaluateAsBooleanConditionNoCache(Expr *E) {
if (BinaryOperator *Bop = dyn_cast<BinaryOperator>(E)) {
if (Bop->isLogicalOp()) {
TryResult LHS = tryEvaluateBool(Bop->getLHS());
if (LHS.isKnown()) {
// We were able to evaluate the LHS, see if we can get away with not
// evaluating the RHS: 0 && X -> 0, 1 || X -> 1
if (LHS.isTrue() == (Bop->getOpcode() == BO_LOr))
return LHS.isTrue();
TryResult RHS = tryEvaluateBool(Bop->getRHS());
if (RHS.isKnown()) {
if (Bop->getOpcode() == BO_LOr)
return LHS.isTrue() || RHS.isTrue();
else
return LHS.isTrue() && RHS.isTrue();
}
} else {
TryResult RHS = tryEvaluateBool(Bop->getRHS());
if (RHS.isKnown()) {
// We can't evaluate the LHS; however, sometimes the result
// is determined by the RHS: X && 0 -> 0, X || 1 -> 1.
if (RHS.isTrue() == (Bop->getOpcode() == BO_LOr))
return RHS.isTrue();
} else {
TryResult BopRes = checkIncorrectLogicOperator(Bop);
if (BopRes.isKnown())
return BopRes.isTrue();
}
}
return TryResult();
} else if (Bop->isEqualityOp()) {
TryResult BopRes = checkIncorrectEqualityOperator(Bop);
if (BopRes.isKnown())
return BopRes.isTrue();
} else if (Bop->isRelationalOp()) {
TryResult BopRes = checkIncorrectRelationalOperator(Bop);
if (BopRes.isKnown())
return BopRes.isTrue();
}
}
bool Result;
if (E->EvaluateAsBooleanCondition(Result, *Context))
return Result;
return TryResult();
}
};
inline bool AddStmtChoice::alwaysAdd(CFGBuilder &builder,
const Stmt *stmt) const {
return builder.alwaysAdd(stmt) || kind == AlwaysAdd;
}
bool CFGBuilder::alwaysAdd(const Stmt *stmt) {
bool shouldAdd = BuildOpts.alwaysAdd(stmt);
if (!BuildOpts.forcedBlkExprs)
return shouldAdd;
if (lastLookup == stmt) {
if (cachedEntry) {
assert(cachedEntry->first == stmt);
return true;
}
return shouldAdd;
}
lastLookup = stmt;
// Perform the lookup!
CFG::BuildOptions::ForcedBlkExprs *fb = *BuildOpts.forcedBlkExprs;
if (!fb) {
// No need to update 'cachedEntry', since it will always be null.
assert(!cachedEntry);
return shouldAdd;
}
CFG::BuildOptions::ForcedBlkExprs::iterator itr = fb->find(stmt);
if (itr == fb->end()) {
cachedEntry = nullptr;
return shouldAdd;
}
cachedEntry = &*itr;
return true;
}
// FIXME: Add support for dependent-sized array types in C++?
// Does it even make sense to build a CFG for an uninstantiated template?
static const VariableArrayType *FindVA(const Type *t) {
while (const ArrayType *vt = dyn_cast<ArrayType>(t)) {
if (const VariableArrayType *vat = dyn_cast<VariableArrayType>(vt))
if (vat->getSizeExpr())
return vat;
t = vt->getElementType().getTypePtr();
}
return nullptr;
}
/// BuildCFG - Constructs a CFG from an AST (a Stmt*). The AST can represent an
/// arbitrary statement. Examples include a single expression or a function
/// body (compound statement). The ownership of the returned CFG is
/// transferred to the caller. If CFG construction fails, this method returns
/// NULL.
std::unique_ptr<CFG> CFGBuilder::buildCFG(const Decl *D, Stmt *Statement) {
assert(cfg.get());
if (!Statement)
return nullptr;
// Create an empty block that will serve as the exit block for the CFG. Since
// this is the first block added to the CFG, it will be implicitly registered
// as the exit block.
Succ = createBlock();
assert(Succ == &cfg->getExit());
Block = nullptr; // the EXIT block is empty. Create all other blocks lazily.
if (BuildOpts.AddImplicitDtors)
if (const CXXDestructorDecl *DD = dyn_cast_or_null<CXXDestructorDecl>(D))
addImplicitDtorsForDestructor(DD);
// Visit the statements and create the CFG.
CFGBlock *B = addStmt(Statement);
if (badCFG)
return nullptr;
// For C++ constructor add initializers to CFG.
if (const CXXConstructorDecl *CD = dyn_cast_or_null<CXXConstructorDecl>(D)) {
for (auto *I : llvm::reverse(CD->inits())) {
B = addInitializer(I);
if (badCFG)
return nullptr;
}
}
if (B)
Succ = B;
// Backpatch the gotos whose label -> block mappings we didn't know when we
// encountered them.
for (BackpatchBlocksTy::iterator I = BackpatchBlocks.begin(),
E = BackpatchBlocks.end(); I != E; ++I ) {
CFGBlock *B = I->block;
const GotoStmt *G = cast<GotoStmt>(B->getTerminator());
LabelMapTy::iterator LI = LabelMap.find(G->getLabel());
// If there is no target for the goto, then we are looking at an
// incomplete AST. Handle this by not registering a successor.
if (LI == LabelMap.end()) continue;
JumpTarget JT = LI->second;
prependAutomaticObjDtorsWithTerminator(B, I->scopePosition,
JT.scopePosition);
addSuccessor(B, JT.block);
}
// Add successors to the Indirect Goto Dispatch block (if we have one).
if (CFGBlock *B = cfg->getIndirectGotoBlock())
for (LabelSetTy::iterator I = AddressTakenLabels.begin(),
E = AddressTakenLabels.end(); I != E; ++I ) {
// Lookup the target block.
LabelMapTy::iterator LI = LabelMap.find(*I);
// If there is no target block that contains label, then we are looking
// at an incomplete AST. Handle this by not registering a successor.
if (LI == LabelMap.end()) continue;
addSuccessor(B, LI->second.block);
}
// Create an empty entry block that has no predecessors.
cfg->setEntry(createBlock());
return std::move(cfg);
}
/// createBlock - Used to lazily create blocks that are connected
/// to the current (global) succcessor.
CFGBlock *CFGBuilder::createBlock(bool add_successor) {
CFGBlock *B = cfg->createBlock();
if (add_successor && Succ)
addSuccessor(B, Succ);
return B;
}
/// createNoReturnBlock - Used to create a block is a 'noreturn' point in the
/// CFG. It is *not* connected to the current (global) successor, and instead
/// directly tied to the exit block in order to be reachable.
CFGBlock *CFGBuilder::createNoReturnBlock() {
CFGBlock *B = createBlock(false);
B->setHasNoReturnElement();
addSuccessor(B, &cfg->getExit(), Succ);
return B;
}
/// addInitializer - Add C++ base or member initializer element to CFG.
CFGBlock *CFGBuilder::addInitializer(CXXCtorInitializer *I) {
if (!BuildOpts.AddInitializers)
return Block;
bool HasTemporaries = false;
// Destructors of temporaries in initialization expression should be called
// after initialization finishes.
Expr *Init = I->getInit();
if (Init) {
HasTemporaries = isa<ExprWithCleanups>(Init);
if (BuildOpts.AddTemporaryDtors && HasTemporaries) {
// Generate destructors for temporaries in initialization expression.
TempDtorContext Context;
VisitForTemporaryDtors(cast<ExprWithCleanups>(Init)->getSubExpr(),
/*BindToTemporary=*/false, Context);
}
}
autoCreateBlock();
appendInitializer(Block, I);
if (Init) {
if (HasTemporaries) {
// For expression with temporaries go directly to subexpression to omit
// generating destructors for the second time.
return Visit(cast<ExprWithCleanups>(Init)->getSubExpr());
}
if (BuildOpts.AddCXXDefaultInitExprInCtors) {
if (CXXDefaultInitExpr *Default = dyn_cast<CXXDefaultInitExpr>(Init)) {
// In general, appending the expression wrapped by a CXXDefaultInitExpr
// may cause the same Expr to appear more than once in the CFG. Doing it
// here is safe because there's only one initializer per field.
autoCreateBlock();
appendStmt(Block, Default);
if (Stmt *Child = Default->getExpr())
if (CFGBlock *R = Visit(Child))
Block = R;
return Block;
}
}
return Visit(Init);
}
return Block;
}
/// \brief Retrieve the type of the temporary object whose lifetime was
/// extended by a local reference with the given initializer.
static QualType getReferenceInitTemporaryType(ASTContext &Context,
const Expr *Init,
bool *FoundMTE = nullptr) {
while (true) {
// Skip parentheses.
Init = Init->IgnoreParens();
// Skip through cleanups.
if (const ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(Init)) {
Init = EWC->getSubExpr();
continue;
}
// Skip through the temporary-materialization expression.
if (const MaterializeTemporaryExpr *MTE
= dyn_cast<MaterializeTemporaryExpr>(Init)) {
Init = MTE->GetTemporaryExpr();
if (FoundMTE)
*FoundMTE = true;
continue;
}
// Skip derived-to-base and no-op casts.
if (const CastExpr *CE = dyn_cast<CastExpr>(Init)) {
if ((CE->getCastKind() == CK_DerivedToBase ||
CE->getCastKind() == CK_UncheckedDerivedToBase ||
CE->getCastKind() == CK_NoOp) &&
Init->getType()->isRecordType()) {
Init = CE->getSubExpr();
continue;
}
}
// Skip member accesses into rvalues.
if (const MemberExpr *ME = dyn_cast<MemberExpr>(Init)) {
if (!ME->isArrow() && ME->getBase()->isRValue()) {
Init = ME->getBase();
continue;
}
}
break;
}
return Init->getType();
}
/// addAutomaticObjDtors - Add to current block automatic objects destructors
/// for objects in range of local scope positions. Use S as trigger statement
/// for destructors.
void CFGBuilder::addAutomaticObjDtors(LocalScope::const_iterator B,
LocalScope::const_iterator E, Stmt *S) {
if (!BuildOpts.AddImplicitDtors)
return;
if (B == E)
return;
// We need to append the destructors in reverse order, but any one of them
// may be a no-return destructor which changes the CFG. As a result, buffer
// this sequence up and replay them in reverse order when appending onto the
// CFGBlock(s).
SmallVector<VarDecl*, 10> Decls;
Decls.reserve(B.distance(E));
for (LocalScope::const_iterator I = B; I != E; ++I)
Decls.push_back(*I);
for (SmallVectorImpl<VarDecl*>::reverse_iterator I = Decls.rbegin(),
E = Decls.rend();
I != E; ++I) {
// If this destructor is marked as a no-return destructor, we need to
// create a new block for the destructor which does not have as a successor
// anything built thus far: control won't flow out of this block.
QualType Ty = (*I)->getType();
if (Ty->isReferenceType()) {
Ty = getReferenceInitTemporaryType(*Context, (*I)->getInit());
}
Ty = Context->getBaseElementType(Ty);
if (Ty->getAsCXXRecordDecl()->isAnyDestructorNoReturn())
Block = createNoReturnBlock();
else
autoCreateBlock();
appendAutomaticObjDtor(Block, *I, S);
}
}
/// addImplicitDtorsForDestructor - Add implicit destructors generated for
/// base and member objects in destructor.
void CFGBuilder::addImplicitDtorsForDestructor(const CXXDestructorDecl *DD) {
assert (BuildOpts.AddImplicitDtors
&& "Can be called only when dtors should be added");
const CXXRecordDecl *RD = DD->getParent();
// At the end destroy virtual base objects.
for (const auto &VI : RD->vbases()) {
const CXXRecordDecl *CD = VI.getType()->getAsCXXRecordDecl();
if (!CD->hasTrivialDestructor()) {
autoCreateBlock();
appendBaseDtor(Block, &VI);
}
}
// Before virtual bases destroy direct base objects.
for (const auto &BI : RD->bases()) {
if (!BI.isVirtual()) {
const CXXRecordDecl *CD = BI.getType()->getAsCXXRecordDecl();
if (!CD->hasTrivialDestructor()) {
autoCreateBlock();
appendBaseDtor(Block, &BI);
}
}
}
// First destroy member objects.
for (auto *FI : RD->fields()) {
// Check for constant size array. Set type to array element type.
QualType QT = FI->getType();
if (const ConstantArrayType *AT = Context->getAsConstantArrayType(QT)) {
if (AT->getSize() == 0)
continue;
QT = AT->getElementType();
}
if (const CXXRecordDecl *CD = QT->getAsCXXRecordDecl())
if (!CD->hasTrivialDestructor()) {
autoCreateBlock();
appendMemberDtor(Block, FI);
}
}
}
/// createOrReuseLocalScope - If Scope is NULL create new LocalScope. Either
/// way return valid LocalScope object.
LocalScope* CFGBuilder::createOrReuseLocalScope(LocalScope* Scope) {
if (Scope)
return Scope;
llvm::BumpPtrAllocator &alloc = cfg->getAllocator();
return new (alloc.Allocate<LocalScope>())
LocalScope(BumpVectorContext(alloc), ScopePos);
}
/// addLocalScopeForStmt - Add LocalScope to local scopes tree for statement
/// that should create implicit scope (e.g. if/else substatements).
void CFGBuilder::addLocalScopeForStmt(Stmt *S) {
if (!BuildOpts.AddImplicitDtors)
return;
LocalScope *Scope = nullptr;
// For compound statement we will be creating explicit scope.
if (CompoundStmt *CS = dyn_cast<CompoundStmt>(S)) {
for (auto *BI : CS->body()) {
Stmt *SI = BI->stripLabelLikeStatements();
if (DeclStmt *DS = dyn_cast<DeclStmt>(SI))
Scope = addLocalScopeForDeclStmt(DS, Scope);
}
return;
}
// For any other statement scope will be implicit and as such will be
// interesting only for DeclStmt.
if (DeclStmt *DS = dyn_cast<DeclStmt>(S->stripLabelLikeStatements()))
addLocalScopeForDeclStmt(DS);
}
/// addLocalScopeForDeclStmt - Add LocalScope for declaration statement. Will
/// reuse Scope if not NULL.
LocalScope* CFGBuilder::addLocalScopeForDeclStmt(DeclStmt *DS,
LocalScope* Scope) {
if (!BuildOpts.AddImplicitDtors)
return Scope;
for (auto *DI : DS->decls())
if (VarDecl *VD = dyn_cast<VarDecl>(DI))
Scope = addLocalScopeForVarDecl(VD, Scope);
return Scope;
}
/// addLocalScopeForVarDecl - Add LocalScope for variable declaration. It will
/// create add scope for automatic objects and temporary objects bound to
/// const reference. Will reuse Scope if not NULL.
LocalScope* CFGBuilder::addLocalScopeForVarDecl(VarDecl *VD,
LocalScope* Scope) {
if (!BuildOpts.AddImplicitDtors)
return Scope;
// Check if variable is local.
switch (VD->getStorageClass()) {
case SC_None:
case SC_Auto:
case SC_Register:
break;
default: return Scope;
}
// Check for const references bound to temporary. Set type to pointee.
QualType QT = VD->getType();
if (QT.getTypePtr()->isReferenceType()) {
// Attempt to determine whether this declaration lifetime-extends a
// temporary.
//
// FIXME: This is incorrect. Non-reference declarations can lifetime-extend
// temporaries, and a single declaration can extend multiple temporaries.
// We should look at the storage duration on each nested
// MaterializeTemporaryExpr instead.
const Expr *Init = VD->getInit();
if (!Init)
return Scope;
// Lifetime-extending a temporary.
bool FoundMTE = false;
QT = getReferenceInitTemporaryType(*Context, Init, &FoundMTE);
if (!FoundMTE)
return Scope;
}
// Check for constant size array. Set type to array element type.
while (const ConstantArrayType *AT = Context->getAsConstantArrayType(QT)) {
if (AT->getSize() == 0)
return Scope;
QT = AT->getElementType();
}
// Check if type is a C++ class with non-trivial destructor.
if (const CXXRecordDecl *CD = QT->getAsCXXRecordDecl())
if (CD->hasDefinition() && !CD->hasTrivialDestructor()) {
// Add the variable to scope
Scope = createOrReuseLocalScope(Scope);
Scope->addVar(VD);
ScopePos = Scope->begin();
}
return Scope;
}
/// addLocalScopeAndDtors - For given statement add local scope for it and
/// add destructors that will cleanup the scope. Will reuse Scope if not NULL.
void CFGBuilder::addLocalScopeAndDtors(Stmt *S) {
if (!BuildOpts.AddImplicitDtors)
return;
LocalScope::const_iterator scopeBeginPos = ScopePos;
addLocalScopeForStmt(S);
addAutomaticObjDtors(ScopePos, scopeBeginPos, S);
}
/// prependAutomaticObjDtorsWithTerminator - Prepend destructor CFGElements for
/// variables with automatic storage duration to CFGBlock's elements vector.
/// Elements will be prepended to physical beginning of the vector which
/// happens to be logical end. Use blocks terminator as statement that specifies
/// destructors call site.
/// FIXME: This mechanism for adding automatic destructors doesn't handle
/// no-return destructors properly.
void CFGBuilder::prependAutomaticObjDtorsWithTerminator(CFGBlock *Blk,
LocalScope::const_iterator B, LocalScope::const_iterator E) {
BumpVectorContext &C = cfg->getBumpVectorContext();
CFGBlock::iterator InsertPos
= Blk->beginAutomaticObjDtorsInsert(Blk->end(), B.distance(E), C);
for (LocalScope::const_iterator I = B; I != E; ++I)
InsertPos = Blk->insertAutomaticObjDtor(InsertPos, *I,
Blk->getTerminator());
}
/// Visit - Walk the subtree of a statement and add extra
/// blocks for ternary operators, &&, and ||. We also process "," and
/// DeclStmts (which may contain nested control-flow).
CFGBlock *CFGBuilder::Visit(Stmt * S, AddStmtChoice asc) {
if (!S) {
badCFG = true;
return nullptr;
}
if (Expr *E = dyn_cast<Expr>(S))
S = E->IgnoreParens();
switch (S->getStmtClass()) {
default:
return VisitStmt(S, asc);
case Stmt::AddrLabelExprClass:
return VisitAddrLabelExpr(cast<AddrLabelExpr>(S), asc);
case Stmt::BinaryConditionalOperatorClass:
return VisitConditionalOperator(cast<BinaryConditionalOperator>(S), asc);
case Stmt::BinaryOperatorClass:
return VisitBinaryOperator(cast<BinaryOperator>(S), asc);
case Stmt::BlockExprClass:
return VisitBlockExpr(cast<BlockExpr>(S), asc);
case Stmt::BreakStmtClass:
return VisitBreakStmt(cast<BreakStmt>(S));
case Stmt::CallExprClass:
case Stmt::CXXOperatorCallExprClass:
case Stmt::CXXMemberCallExprClass:
case Stmt::UserDefinedLiteralClass:
return VisitCallExpr(cast<CallExpr>(S), asc);
case Stmt::CaseStmtClass:
return VisitCaseStmt(cast<CaseStmt>(S));
case Stmt::ChooseExprClass:
return VisitChooseExpr(cast<ChooseExpr>(S), asc);
case Stmt::CompoundStmtClass:
return VisitCompoundStmt(cast<CompoundStmt>(S));
case Stmt::ConditionalOperatorClass:
return VisitConditionalOperator(cast<ConditionalOperator>(S), asc);
case Stmt::ContinueStmtClass:
return VisitContinueStmt(cast<ContinueStmt>(S));
case Stmt::CXXCatchStmtClass:
return VisitCXXCatchStmt(cast<CXXCatchStmt>(S));
case Stmt::ExprWithCleanupsClass:
return VisitExprWithCleanups(cast<ExprWithCleanups>(S), asc);
case Stmt::CXXDefaultArgExprClass:
case Stmt::CXXDefaultInitExprClass:
// FIXME: The expression inside a CXXDefaultArgExpr is owned by the
// called function's declaration, not by the caller. If we simply add
// this expression to the CFG, we could end up with the same Expr
// appearing multiple times.
// PR13385 / <rdar://problem/12156507>
//
// It's likewise possible for multiple CXXDefaultInitExprs for the same
// expression to be used in the same function (through aggregate
// initialization).
return VisitStmt(S, asc);
case Stmt::CXXBindTemporaryExprClass:
return VisitCXXBindTemporaryExpr(cast<CXXBindTemporaryExpr>(S), asc);
case Stmt::CXXConstructExprClass:
return VisitCXXConstructExpr(cast<CXXConstructExpr>(S), asc);
case Stmt::CXXNewExprClass:
return VisitCXXNewExpr(cast<CXXNewExpr>(S), asc);
case Stmt::CXXDeleteExprClass:
return VisitCXXDeleteExpr(cast<CXXDeleteExpr>(S), asc);
case Stmt::CXXFunctionalCastExprClass:
return VisitCXXFunctionalCastExpr(cast<CXXFunctionalCastExpr>(S), asc);
case Stmt::CXXTemporaryObjectExprClass:
return VisitCXXTemporaryObjectExpr(cast<CXXTemporaryObjectExpr>(S), asc);
case Stmt::CXXThrowExprClass:
return VisitCXXThrowExpr(cast<CXXThrowExpr>(S));
case Stmt::CXXTryStmtClass:
return VisitCXXTryStmt(cast<CXXTryStmt>(S));
case Stmt::CXXForRangeStmtClass:
return VisitCXXForRangeStmt(cast<CXXForRangeStmt>(S));
case Stmt::DeclStmtClass:
return VisitDeclStmt(cast<DeclStmt>(S));
case Stmt::DefaultStmtClass:
return VisitDefaultStmt(cast<DefaultStmt>(S));
case Stmt::DoStmtClass:
return VisitDoStmt(cast<DoStmt>(S));
case Stmt::ForStmtClass:
return VisitForStmt(cast<ForStmt>(S));
case Stmt::GotoStmtClass:
return VisitGotoStmt(cast<GotoStmt>(S));
case Stmt::IfStmtClass:
return VisitIfStmt(cast<IfStmt>(S));
case Stmt::ImplicitCastExprClass:
return VisitImplicitCastExpr(cast<ImplicitCastExpr>(S), asc);
case Stmt::IndirectGotoStmtClass:
return VisitIndirectGotoStmt(cast<IndirectGotoStmt>(S));
case Stmt::LabelStmtClass:
return VisitLabelStmt(cast<LabelStmt>(S));
case Stmt::LambdaExprClass:
return VisitLambdaExpr(cast<LambdaExpr>(S), asc);
case Stmt::MemberExprClass:
return VisitMemberExpr(cast<MemberExpr>(S), asc);
case Stmt::NullStmtClass:
return Block;
case Stmt::ObjCAtCatchStmtClass:
return VisitObjCAtCatchStmt(cast<ObjCAtCatchStmt>(S));
case Stmt::ObjCAutoreleasePoolStmtClass:
return VisitObjCAutoreleasePoolStmt(cast<ObjCAutoreleasePoolStmt>(S));
case Stmt::ObjCAtSynchronizedStmtClass:
return VisitObjCAtSynchronizedStmt(cast<ObjCAtSynchronizedStmt>(S));
case Stmt::ObjCAtThrowStmtClass:
return VisitObjCAtThrowStmt(cast<ObjCAtThrowStmt>(S));
case Stmt::ObjCAtTryStmtClass:
return VisitObjCAtTryStmt(cast<ObjCAtTryStmt>(S));
case Stmt::ObjCForCollectionStmtClass:
return VisitObjCForCollectionStmt(cast<ObjCForCollectionStmt>(S));
case Stmt::OpaqueValueExprClass:
return Block;
case Stmt::PseudoObjectExprClass:
return VisitPseudoObjectExpr(cast<PseudoObjectExpr>(S));
case Stmt::ReturnStmtClass:
return VisitReturnStmt(cast<ReturnStmt>(S));
case Stmt::UnaryExprOrTypeTraitExprClass:
return VisitUnaryExprOrTypeTraitExpr(cast<UnaryExprOrTypeTraitExpr>(S),
asc);
case Stmt::StmtExprClass:
return VisitStmtExpr(cast<StmtExpr>(S), asc);
case Stmt::SwitchStmtClass:
return VisitSwitchStmt(cast<SwitchStmt>(S));
case Stmt::UnaryOperatorClass:
return VisitUnaryOperator(cast<UnaryOperator>(S), asc);
case Stmt::WhileStmtClass:
return VisitWhileStmt(cast<WhileStmt>(S));
}
}
CFGBlock *CFGBuilder::VisitStmt(Stmt *S, AddStmtChoice asc) {
if (asc.alwaysAdd(*this, S)) {
autoCreateBlock();
appendStmt(Block, S);
}
return VisitChildren(S);
}
/// VisitChildren - Visit the children of a Stmt.
CFGBlock *CFGBuilder::VisitChildren(Stmt *S) {
CFGBlock *B = Block;
// Visit the children in their reverse order so that they appear in
// left-to-right (natural) order in the CFG.
reverse_children RChildren(S);
for (reverse_children::iterator I = RChildren.begin(), E = RChildren.end();
I != E; ++I) {
if (Stmt *Child = *I)
if (CFGBlock *R = Visit(Child))
B = R;
}
return B;
}
CFGBlock *CFGBuilder::VisitAddrLabelExpr(AddrLabelExpr *A,
AddStmtChoice asc) {
AddressTakenLabels.insert(A->getLabel());
if (asc.alwaysAdd(*this, A)) {
autoCreateBlock();
appendStmt(Block, A);
}
return Block;
}
CFGBlock *CFGBuilder::VisitUnaryOperator(UnaryOperator *U,
AddStmtChoice asc) {
if (asc.alwaysAdd(*this, U)) {
autoCreateBlock();
appendStmt(Block, U);
}
return Visit(U->getSubExpr(), AddStmtChoice());
}
CFGBlock *CFGBuilder::VisitLogicalOperator(BinaryOperator *B) {
CFGBlock *ConfluenceBlock = Block ? Block : createBlock();
appendStmt(ConfluenceBlock, B);
if (badCFG)
return nullptr;
return VisitLogicalOperator(B, nullptr, ConfluenceBlock,
ConfluenceBlock).first;
}
std::pair<CFGBlock*, CFGBlock*>
CFGBuilder::VisitLogicalOperator(BinaryOperator *B,
Stmt *Term,
CFGBlock *TrueBlock,
CFGBlock *FalseBlock) {
// Introspect the RHS. If it is a nested logical operation, we recursively
// build the CFG using this function. Otherwise, resort to default
// CFG construction behavior.
Expr *RHS = B->getRHS()->IgnoreParens();
CFGBlock *RHSBlock, *ExitBlock;
do {
if (BinaryOperator *B_RHS = dyn_cast<BinaryOperator>(RHS))
if (B_RHS->isLogicalOp()) {
std::tie(RHSBlock, ExitBlock) =
VisitLogicalOperator(B_RHS, Term, TrueBlock, FalseBlock);
break;
}
// The RHS is not a nested logical operation. Don't push the terminator
// down further, but instead visit RHS and construct the respective
// pieces of the CFG, and link up the RHSBlock with the terminator
// we have been provided.
ExitBlock = RHSBlock = createBlock(false);
// Even though KnownVal is only used in the else branch of the next
// conditional, tryEvaluateBool performs additional checking on the
// Expr, so it should be called unconditionally.
TryResult KnownVal = tryEvaluateBool(RHS);
if (!KnownVal.isKnown())
KnownVal = tryEvaluateBool(B);
if (!Term) {
assert(TrueBlock == FalseBlock);
addSuccessor(RHSBlock, TrueBlock);
}
else {
RHSBlock->setTerminator(Term);
addSuccessor(RHSBlock, TrueBlock, !KnownVal.isFalse());
addSuccessor(RHSBlock, FalseBlock, !KnownVal.isTrue());
}
Block = RHSBlock;
RHSBlock = addStmt(RHS);
}
while (false);
if (badCFG)
return std::make_pair(nullptr, nullptr);
// Generate the blocks for evaluating the LHS.
Expr *LHS = B->getLHS()->IgnoreParens();
if (BinaryOperator *B_LHS = dyn_cast<BinaryOperator>(LHS))
if (B_LHS->isLogicalOp()) {
if (B->getOpcode() == BO_LOr)
FalseBlock = RHSBlock;
else
TrueBlock = RHSBlock;
// For the LHS, treat 'B' as the terminator that we want to sink
// into the nested branch. The RHS always gets the top-most
// terminator.
return VisitLogicalOperator(B_LHS, B, TrueBlock, FalseBlock);
}
// Create the block evaluating the LHS.
// This contains the '&&' or '||' as the terminator.
CFGBlock *LHSBlock = createBlock(false);
LHSBlock->setTerminator(B);
Block = LHSBlock;
CFGBlock *EntryLHSBlock = addStmt(LHS);
if (badCFG)
return std::make_pair(nullptr, nullptr);
// See if this is a known constant.
TryResult KnownVal = tryEvaluateBool(LHS);
// Now link the LHSBlock with RHSBlock.
if (B->getOpcode() == BO_LOr) {
addSuccessor(LHSBlock, TrueBlock, !KnownVal.isFalse());
addSuccessor(LHSBlock, RHSBlock, !KnownVal.isTrue());
} else {
assert(B->getOpcode() == BO_LAnd);
addSuccessor(LHSBlock, RHSBlock, !KnownVal.isFalse());
addSuccessor(LHSBlock, FalseBlock, !KnownVal.isTrue());
}
return std::make_pair(EntryLHSBlock, ExitBlock);
}
CFGBlock *CFGBuilder::VisitBinaryOperator(BinaryOperator *B,
AddStmtChoice asc) {
// && or ||
if (B->isLogicalOp())
return VisitLogicalOperator(B);
if (B->getOpcode() == BO_Comma) { // ,
autoCreateBlock();
appendStmt(Block, B);
addStmt(B->getRHS());
return addStmt(B->getLHS());
}
if (B->isAssignmentOp()) {
if (asc.alwaysAdd(*this, B)) {
autoCreateBlock();
appendStmt(Block, B);
}
Visit(B->getLHS());
return Visit(B->getRHS());
}
if (asc.alwaysAdd(*this, B)) {
autoCreateBlock();
appendStmt(Block, B);
}
CFGBlock *RBlock = Visit(B->getRHS());
CFGBlock *LBlock = Visit(B->getLHS());
// If visiting RHS causes us to finish 'Block', e.g. the RHS is a StmtExpr
// containing a DoStmt, and the LHS doesn't create a new block, then we should
// return RBlock. Otherwise we'll incorrectly return NULL.
return (LBlock ? LBlock : RBlock);
}
CFGBlock *CFGBuilder::VisitNoRecurse(Expr *E, AddStmtChoice asc) {
if (asc.alwaysAdd(*this, E)) {
autoCreateBlock();
appendStmt(Block, E);
}
return Block;
}
CFGBlock *CFGBuilder::VisitBreakStmt(BreakStmt *B) {
// "break" is a control-flow statement. Thus we stop processing the current
// block.
if (badCFG)
return nullptr;
// Now create a new block that ends with the break statement.
Block = createBlock(false);
Block->setTerminator(B);
// If there is no target for the break, then we are looking at an incomplete
// AST. This means that the CFG cannot be constructed.
if (BreakJumpTarget.block) {
addAutomaticObjDtors(ScopePos, BreakJumpTarget.scopePosition, B);
addSuccessor(Block, BreakJumpTarget.block);
} else
badCFG = true;
return Block;
}
static bool CanThrow(Expr *E, ASTContext &Ctx) {
QualType Ty = E->getType();
if (Ty->isFunctionPointerType())
Ty = Ty->getAs<PointerType>()->getPointeeType();
else if (Ty->isBlockPointerType())
Ty = Ty->getAs<BlockPointerType>()->getPointeeType();
const FunctionType *FT = Ty->getAs<FunctionType>();
if (FT) {
if (const FunctionProtoType *Proto = dyn_cast<FunctionProtoType>(FT))
if (!isUnresolvedExceptionSpec(Proto->getExceptionSpecType()) &&
Proto->isNothrow(Ctx))
return false;
}
return true;
}
CFGBlock *CFGBuilder::VisitCallExpr(CallExpr *C, AddStmtChoice asc) {
// Compute the callee type.
QualType calleeType = C->getCallee()->getType();
if (calleeType == Context->BoundMemberTy) {
QualType boundType = Expr::findBoundMemberType(C->getCallee());
// We should only get a null bound type if processing a dependent
// CFG. Recover by assuming nothing.
if (!boundType.isNull()) calleeType = boundType;
}
// If this is a call to a no-return function, this stops the block here.
bool NoReturn = getFunctionExtInfo(*calleeType).getNoReturn();
bool AddEHEdge = false;
// Languages without exceptions are assumed to not throw.
if (Context->getLangOpts().Exceptions) {
if (BuildOpts.AddEHEdges)
AddEHEdge = true;
}
// If this is a call to a builtin function, it might not actually evaluate
// its arguments. Don't add them to the CFG if this is the case.
bool OmitArguments = false;
if (FunctionDecl *FD = C->getDirectCallee()) {
if (FD->isNoReturn())
NoReturn = true;
if (FD->hasAttr<NoThrowAttr>())
AddEHEdge = false;
if (FD->getBuiltinID() == Builtin::BI__builtin_object_size)
OmitArguments = true;
}
if (!CanThrow(C->getCallee(), *Context))
AddEHEdge = false;
if (OmitArguments) {
assert(!NoReturn && "noreturn calls with unevaluated args not implemented");
assert(!AddEHEdge && "EH calls with unevaluated args not implemented");
autoCreateBlock();
appendStmt(Block, C);
return Visit(C->getCallee());
}
if (!NoReturn && !AddEHEdge) {
return VisitStmt(C, asc.withAlwaysAdd(true));
}
if (Block) {
Succ = Block;
if (badCFG)
return nullptr;
}
if (NoReturn)
Block = createNoReturnBlock();
else
Block = createBlock();
appendStmt(Block, C);
if (AddEHEdge) {
// Add exceptional edges.
if (TryTerminatedBlock)
addSuccessor(Block, TryTerminatedBlock);
else
addSuccessor(Block, &cfg->getExit());
}
return VisitChildren(C);
}
CFGBlock *CFGBuilder::VisitChooseExpr(ChooseExpr *C,
AddStmtChoice asc) {
CFGBlock *ConfluenceBlock = Block ? Block : createBlock();
appendStmt(ConfluenceBlock, C);
if (badCFG)
return nullptr;
AddStmtChoice alwaysAdd = asc.withAlwaysAdd(true);
Succ = ConfluenceBlock;
Block = nullptr;
CFGBlock *LHSBlock = Visit(C->getLHS(), alwaysAdd);
if (badCFG)
return nullptr;
Succ = ConfluenceBlock;
Block = nullptr;
CFGBlock *RHSBlock = Visit(C->getRHS(), alwaysAdd);
if (badCFG)
return nullptr;
Block = createBlock(false);
// See if this is a known constant.
const TryResult& KnownVal = tryEvaluateBool(C->getCond());
addSuccessor(Block, KnownVal.isFalse() ? nullptr : LHSBlock);
addSuccessor(Block, KnownVal.isTrue() ? nullptr : RHSBlock);
Block->setTerminator(C);
return addStmt(C->getCond());
}
CFGBlock *CFGBuilder::VisitCompoundStmt(CompoundStmt *C) {
LocalScope::const_iterator scopeBeginPos = ScopePos;
if (BuildOpts.AddImplicitDtors) {
addLocalScopeForStmt(C);
}
if (!C->body_empty() && !isa<ReturnStmt>(*C->body_rbegin())) {
// If the body ends with a ReturnStmt, the dtors will be added in
// VisitReturnStmt.
addAutomaticObjDtors(ScopePos, scopeBeginPos, C);
}
CFGBlock *LastBlock = Block;
for (CompoundStmt::reverse_body_iterator I=C->body_rbegin(), E=C->body_rend();
I != E; ++I ) {
// If we hit a segment of code just containing ';' (NullStmts), we can
// get a null block back. In such cases, just use the LastBlock
if (CFGBlock *newBlock = addStmt(*I))
LastBlock = newBlock;
if (badCFG)
return nullptr;
}
return LastBlock;
}
CFGBlock *CFGBuilder::VisitConditionalOperator(AbstractConditionalOperator *C,
AddStmtChoice asc) {
const BinaryConditionalOperator *BCO = dyn_cast<BinaryConditionalOperator>(C);
const OpaqueValueExpr *opaqueValue = (BCO ? BCO->getOpaqueValue() : nullptr);
// Create the confluence block that will "merge" the results of the ternary
// expression.
CFGBlock *ConfluenceBlock = Block ? Block : createBlock();
appendStmt(ConfluenceBlock, C);
if (badCFG)
return nullptr;
AddStmtChoice alwaysAdd = asc.withAlwaysAdd(true);
// Create a block for the LHS expression if there is an LHS expression. A
// GCC extension allows LHS to be NULL, causing the condition to be the
// value that is returned instead.
// e.g: x ?: y is shorthand for: x ? x : y;
Succ = ConfluenceBlock;
Block = nullptr;
CFGBlock *LHSBlock = nullptr;
const Expr *trueExpr = C->getTrueExpr();
if (trueExpr != opaqueValue) {
LHSBlock = Visit(C->getTrueExpr(), alwaysAdd);
if (badCFG)
return nullptr;
Block = nullptr;
}
else
LHSBlock = ConfluenceBlock;
// Create the block for the RHS expression.
Succ = ConfluenceBlock;
CFGBlock *RHSBlock = Visit(C->getFalseExpr(), alwaysAdd);
if (badCFG)
return nullptr;
// If the condition is a logical '&&' or '||', build a more accurate CFG.
if (BinaryOperator *Cond =
dyn_cast<BinaryOperator>(C->getCond()->IgnoreParens()))
if (Cond->isLogicalOp())
return VisitLogicalOperator(Cond, C, LHSBlock, RHSBlock).first;
// Create the block that will contain the condition.
Block = createBlock(false);
// See if this is a known constant.
const TryResult& KnownVal = tryEvaluateBool(C->getCond());
addSuccessor(Block, LHSBlock, !KnownVal.isFalse());
addSuccessor(Block, RHSBlock, !KnownVal.isTrue());
Block->setTerminator(C);
Expr *condExpr = C->getCond();
if (opaqueValue) {
// Run the condition expression if it's not trivially expressed in
// terms of the opaque value (or if there is no opaque value).
if (condExpr != opaqueValue)
addStmt(condExpr);
// Before that, run the common subexpression if there was one.
// At least one of this or the above will be run.
return addStmt(BCO->getCommon());
}
return addStmt(condExpr);
}
CFGBlock *CFGBuilder::VisitDeclStmt(DeclStmt *DS) {
// Check if the Decl is for an __label__. If so, elide it from the
// CFG entirely.
if (isa<LabelDecl>(*DS->decl_begin()))
return Block;
// This case also handles static_asserts.
if (DS->isSingleDecl())
return VisitDeclSubExpr(DS);
CFGBlock *B = nullptr;
// Build an individual DeclStmt for each decl.
for (DeclStmt::reverse_decl_iterator I = DS->decl_rbegin(),
E = DS->decl_rend();
I != E; ++I) {
// Get the alignment of the new DeclStmt, padding out to >=8 bytes.
unsigned A = alignof(DeclStmt) < 8 ? 8 : alignof(DeclStmt);
// Allocate the DeclStmt using the BumpPtrAllocator. It will get
// automatically freed with the CFG.
DeclGroupRef DG(*I);
Decl *D = *I;
void *Mem = cfg->getAllocator().Allocate(sizeof(DeclStmt), A);
DeclStmt *DSNew = new (Mem) DeclStmt(DG, D->getLocation(), GetEndLoc(D));
cfg->addSyntheticDeclStmt(DSNew, DS);
// Append the fake DeclStmt to block.
B = VisitDeclSubExpr(DSNew);
}
return B;
}
/// VisitDeclSubExpr - Utility method to add block-level expressions for
/// DeclStmts and initializers in them.
CFGBlock *CFGBuilder::VisitDeclSubExpr(DeclStmt *DS) {
assert(DS->isSingleDecl() && "Can handle single declarations only.");
VarDecl *VD = dyn_cast<VarDecl>(DS->getSingleDecl());
if (!VD) {
// Of everything that can be declared in a DeclStmt, only VarDecls impact
// runtime semantics.
return Block;
}
bool HasTemporaries = false;
// Guard static initializers under a branch.
CFGBlock *blockAfterStaticInit = nullptr;
if (BuildOpts.AddStaticInitBranches && VD->isStaticLocal()) {
// For static variables, we need to create a branch to track
// whether or not they are initialized.
if (Block) {
Succ = Block;
Block = nullptr;
if (badCFG)
return nullptr;
}
blockAfterStaticInit = Succ;
}
// Destructors of temporaries in initialization expression should be called
// after initialization finishes.
Expr *Init = VD->getInit();
if (Init) {
HasTemporaries = isa<ExprWithCleanups>(Init);
if (BuildOpts.AddTemporaryDtors && HasTemporaries) {
// Generate destructors for temporaries in initialization expression.
TempDtorContext Context;
VisitForTemporaryDtors(cast<ExprWithCleanups>(Init)->getSubExpr(),
/*BindToTemporary=*/false, Context);
}
}
autoCreateBlock();
appendStmt(Block, DS);
// Keep track of the last non-null block, as 'Block' can be nulled out
// if the initializer expression is something like a 'while' in a
// statement-expression.
CFGBlock *LastBlock = Block;
if (Init) {
if (HasTemporaries) {
// For expression with temporaries go directly to subexpression to omit
// generating destructors for the second time.
ExprWithCleanups *EC = cast<ExprWithCleanups>(Init);
if (CFGBlock *newBlock = Visit(EC->getSubExpr()))
LastBlock = newBlock;
}
else {
if (CFGBlock *newBlock = Visit(Init))
LastBlock = newBlock;
}
}
// If the type of VD is a VLA, then we must process its size expressions.
for (const VariableArrayType* VA = FindVA(VD->getType().getTypePtr());
VA != nullptr; VA = FindVA(VA->getElementType().getTypePtr())) {
if (CFGBlock *newBlock = addStmt(VA->getSizeExpr()))
LastBlock = newBlock;
}
// Remove variable from local scope.
if (ScopePos && VD == *ScopePos)
++ScopePos;
CFGBlock *B = LastBlock;
if (blockAfterStaticInit) {
Succ = B;
Block = createBlock(false);
Block->setTerminator(DS);
addSuccessor(Block, blockAfterStaticInit);
addSuccessor(Block, B);
B = Block;
}
return B;
}
CFGBlock *CFGBuilder::VisitIfStmt(IfStmt *I) {
// We may see an if statement in the middle of a basic block, or it may be the
// first statement we are processing. In either case, we create a new basic
// block. First, we create the blocks for the then...else statements, and
// then we create the block containing the if statement. If we were in the
// middle of a block, we stop processing that block. That block is then the
// implicit successor for the "then" and "else" clauses.
// Save local scope position because in case of condition variable ScopePos
// won't be restored when traversing AST.
SaveAndRestore<LocalScope::const_iterator> save_scope_pos(ScopePos);
// Create local scope for C++17 if init-stmt if one exists.
if (Stmt *Init = I->getInit())
addLocalScopeForStmt(Init);
// Create local scope for possible condition variable.
// Store scope position. Add implicit destructor.
if (VarDecl *VD = I->getConditionVariable())
addLocalScopeForVarDecl(VD);
addAutomaticObjDtors(ScopePos, save_scope_pos.get(), I);
// The block we were processing is now finished. Make it the successor
// block.
if (Block) {
Succ = Block;
if (badCFG)
return nullptr;
}
// Process the false branch.
CFGBlock *ElseBlock = Succ;
if (Stmt *Else = I->getElse()) {
SaveAndRestore<CFGBlock*> sv(Succ);
// NULL out Block so that the recursive call to Visit will
// create a new basic block.
Block = nullptr;
// If branch is not a compound statement create implicit scope
// and add destructors.
if (!isa<CompoundStmt>(Else))
addLocalScopeAndDtors(Else);
ElseBlock = addStmt(Else);
if (!ElseBlock) // Can occur when the Else body has all NullStmts.
ElseBlock = sv.get();
else if (Block) {
if (badCFG)
return nullptr;
}
}
// Process the true branch.
CFGBlock *ThenBlock;
{
Stmt *Then = I->getThen();
assert(Then);
SaveAndRestore<CFGBlock*> sv(Succ);
Block = nullptr;
// If branch is not a compound statement create implicit scope
// and add destructors.
if (!isa<CompoundStmt>(Then))
addLocalScopeAndDtors(Then);
ThenBlock = addStmt(Then);
if (!ThenBlock) {
// We can reach here if the "then" body has all NullStmts.
// Create an empty block so we can distinguish between true and false
// branches in path-sensitive analyses.
ThenBlock = createBlock(false);
addSuccessor(ThenBlock, sv.get());
} else if (Block) {
if (badCFG)
return nullptr;
}
}
// Specially handle "if (expr1 || ...)" and "if (expr1 && ...)" by
// having these handle the actual control-flow jump. Note that
// if we introduce a condition variable, e.g. "if (int x = exp1 || exp2)"
// we resort to the old control-flow behavior. This special handling
// removes infeasible paths from the control-flow graph by having the
// control-flow transfer of '&&' or '||' go directly into the then/else
// blocks directly.
BinaryOperator *Cond =
I->getConditionVariable()
? nullptr
: dyn_cast<BinaryOperator>(I->getCond()->IgnoreParens());
CFGBlock *LastBlock;
if (Cond && Cond->isLogicalOp())
LastBlock = VisitLogicalOperator(Cond, I, ThenBlock, ElseBlock).first;
else {
// Now create a new block containing the if statement.
Block = createBlock(false);
// Set the terminator of the new block to the If statement.
Block->setTerminator(I);
// See if this is a known constant.
const TryResult &KnownVal = tryEvaluateBool(I->getCond());
// Add the successors. If we know that specific branches are
// unreachable, inform addSuccessor() of that knowledge.
addSuccessor(Block, ThenBlock, /* isReachable = */ !KnownVal.isFalse());
addSuccessor(Block, ElseBlock, /* isReachable = */ !KnownVal.isTrue());
// Add the condition as the last statement in the new block. This may
// create new blocks as the condition may contain control-flow. Any newly
// created blocks will be pointed to be "Block".
LastBlock = addStmt(I->getCond());
// If the IfStmt contains a condition variable, add it and its
// initializer to the CFG.
if (const DeclStmt* DS = I->getConditionVariableDeclStmt()) {
autoCreateBlock();
LastBlock = addStmt(const_cast<DeclStmt *>(DS));
}
}
// Finally, if the IfStmt contains a C++17 init-stmt, add it to the CFG.
if (Stmt *Init = I->getInit()) {
autoCreateBlock();
LastBlock = addStmt(Init);
}
return LastBlock;
}
CFGBlock *CFGBuilder::VisitReturnStmt(ReturnStmt *R) {
// If we were in the middle of a block we stop processing that block.
//
// NOTE: If a "return" appears in the middle of a block, this means that the
// code afterwards is DEAD (unreachable). We still keep a basic block
// for that code; a simple "mark-and-sweep" from the entry block will be
// able to report such dead blocks.
// Create the new block.
Block = createBlock(false);
addAutomaticObjDtors(ScopePos, LocalScope::const_iterator(), R);
// If the one of the destructors does not return, we already have the Exit
// block as a successor.
if (!Block->hasNoReturnElement())
addSuccessor(Block, &cfg->getExit());
// Add the return statement to the block. This may create new blocks if R
// contains control-flow (short-circuit operations).
return VisitStmt(R, AddStmtChoice::AlwaysAdd);
}
CFGBlock *CFGBuilder::VisitLabelStmt(LabelStmt *L) {
// Get the block of the labeled statement. Add it to our map.
addStmt(L->getSubStmt());
CFGBlock *LabelBlock = Block;
if (!LabelBlock) // This can happen when the body is empty, i.e.
LabelBlock = createBlock(); // scopes that only contains NullStmts.
assert(LabelMap.find(L->getDecl()) == LabelMap.end() &&
"label already in map");
LabelMap[L->getDecl()] = JumpTarget(LabelBlock, ScopePos);
// Labels partition blocks, so this is the end of the basic block we were
// processing (L is the block's label). Because this is label (and we have
// already processed the substatement) there is no extra control-flow to worry
// about.
LabelBlock->setLabel(L);
if (badCFG)
return nullptr;
// We set Block to NULL to allow lazy creation of a new block (if necessary);
Block = nullptr;
// This block is now the implicit successor of other blocks.
Succ = LabelBlock;
return LabelBlock;
}
CFGBlock *CFGBuilder::VisitBlockExpr(BlockExpr *E, AddStmtChoice asc) {
CFGBlock *LastBlock = VisitNoRecurse(E, asc);
for (const BlockDecl::Capture &CI : E->getBlockDecl()->captures()) {
if (Expr *CopyExpr = CI.getCopyExpr()) {
CFGBlock *Tmp = Visit(CopyExpr);
if (Tmp)
LastBlock = Tmp;
}
}
return LastBlock;
}
CFGBlock *CFGBuilder::VisitLambdaExpr(LambdaExpr *E, AddStmtChoice asc) {
CFGBlock *LastBlock = VisitNoRecurse(E, asc);
for (LambdaExpr::capture_init_iterator it = E->capture_init_begin(),
et = E->capture_init_end(); it != et; ++it) {
if (Expr *Init = *it) {
CFGBlock *Tmp = Visit(Init);
if (Tmp)
LastBlock = Tmp;
}
}
return LastBlock;
}
CFGBlock *CFGBuilder::VisitGotoStmt(GotoStmt *G) {
// Goto is a control-flow statement. Thus we stop processing the current
// block and create a new one.
Block = createBlock(false);
Block->setTerminator(G);
// If we already know the mapping to the label block add the successor now.
LabelMapTy::iterator I = LabelMap.find(G->getLabel());
if (I == LabelMap.end())
// We will need to backpatch this block later.
BackpatchBlocks.push_back(JumpSource(Block, ScopePos));
else {
JumpTarget JT = I->second;
addAutomaticObjDtors(ScopePos, JT.scopePosition, G);
addSuccessor(Block, JT.block);
}
return Block;
}
CFGBlock *CFGBuilder::VisitForStmt(ForStmt *F) {
CFGBlock *LoopSuccessor = nullptr;
// Save local scope position because in case of condition variable ScopePos
// won't be restored when traversing AST.
SaveAndRestore<LocalScope::const_iterator> save_scope_pos(ScopePos);
// Create local scope for init statement and possible condition variable.
// Add destructor for init statement and condition variable.
// Store scope position for continue statement.
if (Stmt *Init = F->getInit())
addLocalScopeForStmt(Init);
LocalScope::const_iterator LoopBeginScopePos = ScopePos;
if (VarDecl *VD = F->getConditionVariable())
addLocalScopeForVarDecl(VD);
LocalScope::const_iterator ContinueScopePos = ScopePos;
addAutomaticObjDtors(ScopePos, save_scope_pos.get(), F);
// "for" is a control-flow statement. Thus we stop processing the current
// block.
if (Block) {
if (badCFG)
return nullptr;
LoopSuccessor = Block;
} else
LoopSuccessor = Succ;
// Save the current value for the break targets.
// All breaks should go to the code following the loop.
SaveAndRestore<JumpTarget> save_break(BreakJumpTarget);
BreakJumpTarget = JumpTarget(LoopSuccessor, ScopePos);
CFGBlock *BodyBlock = nullptr, *TransitionBlock = nullptr;
// Now create the loop body.
{
assert(F->getBody());
// Save the current values for Block, Succ, continue and break targets.
SaveAndRestore<CFGBlock*> save_Block(Block), save_Succ(Succ);
SaveAndRestore<JumpTarget> save_continue(ContinueJumpTarget);
// Create an empty block to represent the transition block for looping back
// to the head of the loop. If we have increment code, it will
// go in this block as well.
Block = Succ = TransitionBlock = createBlock(false);
TransitionBlock->setLoopTarget(F);
if (Stmt *I = F->getInc()) {
// Generate increment code in its own basic block. This is the target of
// continue statements.
Succ = addStmt(I);
}
// Finish up the increment (or empty) block if it hasn't been already.
if (Block) {
assert(Block == Succ);
if (badCFG)
return nullptr;
Block = nullptr;
}
// The starting block for the loop increment is the block that should
// represent the 'loop target' for looping back to the start of the loop.
ContinueJumpTarget = JumpTarget(Succ, ContinueScopePos);
ContinueJumpTarget.block->setLoopTarget(F);
// Loop body should end with destructor of Condition variable (if any).
addAutomaticObjDtors(ScopePos, LoopBeginScopePos, F);
// If body is not a compound statement create implicit scope
// and add destructors.
if (!isa<CompoundStmt>(F->getBody()))
addLocalScopeAndDtors(F->getBody());
// Now populate the body block, and in the process create new blocks as we
// walk the body of the loop.
BodyBlock = addStmt(F->getBody());
if (!BodyBlock) {
// In the case of "for (...;...;...);" we can have a null BodyBlock.
// Use the continue jump target as the proxy for the body.
BodyBlock = ContinueJumpTarget.block;
}
else if (badCFG)
return nullptr;
}
// Because of short-circuit evaluation, the condition of the loop can span
// multiple basic blocks. Thus we need the "Entry" and "Exit" blocks that
// evaluate the condition.
CFGBlock *EntryConditionBlock = nullptr, *ExitConditionBlock = nullptr;
do {
Expr *C = F->getCond();
// Specially handle logical operators, which have a slightly
// more optimal CFG representation.
if (BinaryOperator *Cond =
dyn_cast_or_null<BinaryOperator>(C ? C->IgnoreParens() : nullptr))
if (Cond->isLogicalOp()) {
std::tie(EntryConditionBlock, ExitConditionBlock) =
VisitLogicalOperator(Cond, F, BodyBlock, LoopSuccessor);
break;
}
// The default case when not handling logical operators.
EntryConditionBlock = ExitConditionBlock = createBlock(false);
ExitConditionBlock->setTerminator(F);
// See if this is a known constant.
TryResult KnownVal(true);
if (C) {
// Now add the actual condition to the condition block.
// Because the condition itself may contain control-flow, new blocks may
// be created. Thus we update "Succ" after adding the condition.
Block = ExitConditionBlock;
EntryConditionBlock = addStmt(C);
// If this block contains a condition variable, add both the condition
// variable and initializer to the CFG.
if (VarDecl *VD = F->getConditionVariable()) {
if (Expr *Init = VD->getInit()) {
autoCreateBlock();
appendStmt(Block, F->getConditionVariableDeclStmt());
EntryConditionBlock = addStmt(Init);
assert(Block == EntryConditionBlock);
}
}
if (Block && badCFG)
return nullptr;
KnownVal = tryEvaluateBool(C);
}
// Add the loop body entry as a successor to the condition.
addSuccessor(ExitConditionBlock, KnownVal.isFalse() ? nullptr : BodyBlock);
// Link up the condition block with the code that follows the loop. (the
// false branch).
addSuccessor(ExitConditionBlock,
KnownVal.isTrue() ? nullptr : LoopSuccessor);
} while (false);
// Link up the loop-back block to the entry condition block.
addSuccessor(TransitionBlock, EntryConditionBlock);
// The condition block is the implicit successor for any code above the loop.
Succ = EntryConditionBlock;
// If the loop contains initialization, create a new block for those
// statements. This block can also contain statements that precede the loop.
if (Stmt *I = F->getInit()) {
Block = createBlock();
return addStmt(I);
}
// There is no loop initialization. We are thus basically a while loop.
// NULL out Block to force lazy block construction.
Block = nullptr;
Succ = EntryConditionBlock;
return EntryConditionBlock;
}
CFGBlock *CFGBuilder::VisitMemberExpr(MemberExpr *M, AddStmtChoice asc) {
if (asc.alwaysAdd(*this, M)) {
autoCreateBlock();
appendStmt(Block, M);
}
return Visit(M->getBase());
}
CFGBlock *CFGBuilder::VisitObjCForCollectionStmt(ObjCForCollectionStmt *S) {
// Objective-C fast enumeration 'for' statements:
// http://developer.apple.com/documentation/Cocoa/Conceptual/ObjectiveC
//
// for ( Type newVariable in collection_expression ) { statements }
//
// becomes:
//
// prologue:
// 1. collection_expression