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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 "llvm/Support/SaveAndRestore.h"
#include "clang/Analysis/CFG.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/AST/PrettyPrinter.h"
#include "clang/AST/CharUnits.h"
#include "clang/Basic/AttrKinds.h"
#include "llvm/Support/GraphWriter.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Format.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/OwningPtr.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();
}
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(NULL), 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);
}
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(ctx), Vars(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;
}
/// BlockScopePosPair - Structure for specifying position in CFG during its
/// build process. It consists of CFGBlock that specifies position in CFG graph
/// and LocalScope::const_iterator that specifies position in LocalScope graph.
struct BlockScopePosPair {
BlockScopePosPair() : block(0) {}
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;
}
};
/// 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;
/// CFG* cfg = builder.BuildAST(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;
OwningPtr<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(NULL), Succ(NULL),
SwitchTerminatedBlock(NULL), DefaultCaseBlock(NULL),
TryTerminatedBlock(NULL), badCFG(false), BuildOpts(buildOpts),
switchExclusivelyCovered(false), switchCond(0),
cachedEntry(0), lastLookup(0) {}
// buildCFG - Used by external clients to construct the CFG.
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 *VisitCXXCatchStmt(CXXCatchStmt *S);
CFGBlock *VisitExprWithCleanups(ExprWithCleanups *E,
AddStmtChoice asc);
CFGBlock *VisitCXXThrowExpr(CXXThrowExpr *T);
CFGBlock *VisitCXXTryStmt(CXXTryStmt *S);
CFGBlock *VisitCXXForRangeStmt(CXXForRangeStmt *S);
CFGBlock *VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E,
AddStmtChoice asc);
CFGBlock *VisitCXXConstructExpr(CXXConstructExpr *C, AddStmtChoice asc);
CFGBlock *VisitCXXFunctionalCastExpr(CXXFunctionalCastExpr *E,
AddStmtChoice asc);
CFGBlock *VisitCXXTemporaryObjectExpr(CXXTemporaryObjectExpr *C,
AddStmtChoice asc);
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 *VisitDeclStmt(DeclStmt *DS);
CFGBlock *VisitDeclSubExpr(DeclStmt *DS);
CFGBlock *VisitDefaultStmt(DefaultStmt *D);
CFGBlock *VisitDoStmt(DoStmt *D);
CFGBlock *VisitLambdaExpr(LambdaExpr *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 *VisitLambdaExpr(LambdaExpr *L);
CFGBlock *VisitMemberExpr(MemberExpr *M, AddStmtChoice asc);
CFGBlock *VisitObjCAtCatchStmt(ObjCAtCatchStmt *S);
CFGBlock *VisitObjCAutoreleasePoolStmt(ObjCAutoreleasePoolStmt *S);
CFGBlock *VisitObjCAtSynchronizedStmt(ObjCAtSynchronizedStmt *S);
CFGBlock *VisitObjCAtThrowStmt(ObjCAtThrowStmt *S);
CFGBlock *VisitObjCAtTryStmt(ObjCAtTryStmt *S);
CFGBlock *VisitObjCForCollectionStmt(ObjCForCollectionStmt *S);
CFGBlock *VisitReturnStmt(ReturnStmt *R);
CFGBlock *VisitPseudoObjectExpr(PseudoObjectExpr *E);
CFGBlock *VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *E,
AddStmtChoice asc);
CFGBlock *VisitStmtExpr(StmtExpr *S, AddStmtChoice asc);
CFGBlock *VisitSwitchStmt(SwitchStmt *S);
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);
// Visitors to walk an AST and generate destructors of temporaries in
// full expression.
CFGBlock *VisitForTemporaryDtors(Stmt *E, bool BindToTemporary = false);
CFGBlock *VisitChildrenForTemporaryDtors(Stmt *E);
CFGBlock *VisitBinaryOperatorForTemporaryDtors(BinaryOperator *E);
CFGBlock *VisitCXXBindTemporaryExprForTemporaryDtors(CXXBindTemporaryExpr *E,
bool BindToTemporary);
CFGBlock *
VisitConditionalOperatorForTemporaryDtors(AbstractConditionalOperator *E,
bool BindToTemporary);
// 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 = NULL);
LocalScope* addLocalScopeForVarDecl(VarDecl *VD, LocalScope* Scope = NULL);
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 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 prependAutomaticObjDtorsWithTerminator(CFGBlock *Blk,
LocalScope::const_iterator B, LocalScope::const_iterator E);
void addSuccessor(CFGBlock *B, CFGBlock *S) {
B->addSuccessor(S, cfg->getBumpVectorContext());
}
/// 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;
}
}
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();
}
}
return TryResult();
}
}
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 == 0);
return shouldAdd;
}
CFG::BuildOptions::ForcedBlkExprs::iterator itr = fb->find(stmt);
if (itr == fb->end()) {
cachedEntry = 0;
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 0;
}
/// 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.
CFG* CFGBuilder::buildCFG(const Decl *D, Stmt *Statement) {
assert(cfg.get());
if (!Statement)
return NULL;
// 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 = NULL; // 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 NULL;
// For C++ constructor add initializers to CFG.
if (const CXXConstructorDecl *CD = dyn_cast_or_null<CXXConstructorDecl>(D)) {
for (CXXConstructorDecl::init_const_reverse_iterator I = CD->init_rbegin(),
E = CD->init_rend(); I != E; ++I) {
B = addInitializer(*I);
if (badCFG)
return NULL;
}
}
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;
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 cfg.take();
}
/// 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());
return B;
}
/// addInitializer - Add C++ base or member initializer element to CFG.
CFGBlock *CFGBuilder::addInitializer(CXXCtorInitializer *I) {
if (!BuildOpts.AddInitializers)
return Block;
bool IsReference = false;
bool HasTemporaries = false;
// Destructors of temporaries in initialization expression should be called
// after initialization finishes.
Expr *Init = I->getInit();
if (Init) {
if (FieldDecl *FD = I->getAnyMember())
IsReference = FD->getType()->isReferenceType();
HasTemporaries = isa<ExprWithCleanups>(Init);
if (BuildOpts.AddImplicitDtors && HasTemporaries) {
// Generate destructors for temporaries in initialization expression.
VisitForTemporaryDtors(cast<ExprWithCleanups>(Init)->getSubExpr(),
IsReference);
}
}
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());
}
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) {
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();
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;
if ((*I)->getType()->isReferenceType()) {
Ty = getReferenceInitTemporaryType(*Context, (*I)->getInit());
} else {
Ty = Context->getBaseElementType((*I)->getType());
}
const CXXDestructorDecl *Dtor = Ty->getAsCXXRecordDecl()->getDestructor();
if (cast<FunctionType>(Dtor->getType())->getNoReturnAttr())
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 (CXXRecordDecl::base_class_const_iterator VI = RD->vbases_begin(),
VE = RD->vbases_end(); VI != VE; ++VI) {
const CXXRecordDecl *CD = VI->getType()->getAsCXXRecordDecl();
if (!CD->hasTrivialDestructor()) {
autoCreateBlock();
appendBaseDtor(Block, VI);
}
}
// Before virtual bases destroy direct base objects.
for (CXXRecordDecl::base_class_const_iterator BI = RD->bases_begin(),
BE = RD->bases_end(); BI != BE; ++BI) {
if (!BI->isVirtual()) {
const CXXRecordDecl *CD = BI->getType()->getAsCXXRecordDecl();
if (!CD->hasTrivialDestructor()) {
autoCreateBlock();
appendBaseDtor(Block, BI);
}
}
}
// First destroy member objects.
for (CXXRecordDecl::field_iterator FI = RD->field_begin(),
FE = RD->field_end(); FI != FE; ++FI) {
// 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) {
llvm::BumpPtrAllocator &alloc = cfg->getAllocator();
Scope = alloc.Allocate<LocalScope>();
BumpVectorContext ctx(alloc);
new (Scope) LocalScope(ctx, ScopePos);
}
return Scope;
}
/// 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 = 0;
// For compound statement we will be creating explicit scope.
if (CompoundStmt *CS = dyn_cast<CompoundStmt>(S)) {
for (CompoundStmt::body_iterator BI = CS->body_begin(), BE = CS->body_end()
; BI != BE; ++BI) {
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 (DeclStmt::decl_iterator DI = DS->decl_begin(), DE = DS->decl_end()
; DI != DE; ++DI) {
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()) {
if (!VD->extendsLifetimeOfTemporary())
return Scope;
QT = getReferenceInitTemporaryType(*Context, VD->getInit());
}
// 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->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 0;
}
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 VisitNoRecurse(cast<Expr>(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::CXXBindTemporaryExprClass:
return VisitCXXBindTemporaryExpr(cast<CXXBindTemporaryExpr>(S), asc);
case Stmt::CXXConstructExprClass:
return VisitCXXConstructExpr(cast<CXXConstructExpr>(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 *Terminator) {
CFGBlock *lastBlock = Block;
for (Stmt::child_range I = Terminator->children(); I; ++I)
if (Stmt *child = *I)
if (CFGBlock *b = Visit(child))
lastBlock = b;
return lastBlock;
}
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::VisitBinaryOperator(BinaryOperator *B,
AddStmtChoice asc) {
if (B->isLogicalOp()) { // && or ||
CFGBlock *ConfluenceBlock = Block ? Block : createBlock();
appendStmt(ConfluenceBlock, B);
if (badCFG)
return 0;
// create the block evaluating the LHS
CFGBlock *LHSBlock = createBlock(false);
LHSBlock->setTerminator(B);
// create the block evaluating the RHS
Succ = ConfluenceBlock;
Block = NULL;
CFGBlock *RHSBlock = addStmt(B->getRHS());
if (RHSBlock) {
if (badCFG)
return 0;
} else {
// Create an empty block for cases where the RHS doesn't require
// any explicit statements in the CFG.
RHSBlock = createBlock();
}
// Generate the blocks for evaluating the LHS.
Block = LHSBlock;
CFGBlock *EntryLHSBlock = addStmt(B->getLHS());
// See if this is a known constant.
TryResult KnownVal = tryEvaluateBool(B->getLHS());
if (KnownVal.isKnown() && (B->getOpcode() == BO_LOr))
KnownVal.negate();
// Now link the LHSBlock with RHSBlock.
if (B->getOpcode() == BO_LOr) {
addSuccessor(LHSBlock, KnownVal.isTrue() ? NULL : ConfluenceBlock);
addSuccessor(LHSBlock, KnownVal.isFalse() ? NULL : RHSBlock);
} else {
assert(B->getOpcode() == BO_LAnd);
addSuccessor(LHSBlock, KnownVal.isFalse() ? NULL : RHSBlock);
addSuccessor(LHSBlock, KnownVal.isTrue() ? NULL : ConfluenceBlock);
}
return EntryLHSBlock;
}
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 0;
// 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 (Proto->getExceptionSpecType() != EST_Uninstantiated &&
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 (FunctionDecl *FD = C->getDirectCallee()) {
if (FD->hasAttr<NoReturnAttr>())
NoReturn = true;
if (FD->hasAttr<NoThrowAttr>())
AddEHEdge = false;
}
if (!CanThrow(C->getCallee(), *Context))
AddEHEdge = false;
if (!NoReturn && !AddEHEdge)
return VisitStmt(C, asc.withAlwaysAdd(true));
if (Block) {
Succ = Block;
if (badCFG)
return 0;
}
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 0;
AddStmtChoice alwaysAdd = asc.withAlwaysAdd(true);
Succ = ConfluenceBlock;
Block = NULL;
CFGBlock *LHSBlock = Visit(C->getLHS(), alwaysAdd);
if (badCFG)
return 0;
Succ = ConfluenceBlock;
Block = NULL;
CFGBlock *RHSBlock = Visit(C->getRHS(), alwaysAdd);
if (badCFG)
return 0;
Block = createBlock(false);
// See if this is a known constant.
const TryResult& KnownVal = tryEvaluateBool(C->getCond());
addSuccessor(Block, KnownVal.isFalse() ? NULL : LHSBlock);
addSuccessor(Block, KnownVal.isTrue() ? NULL : RHSBlock);
Block->setTerminator(C);
return addStmt(C->getCond());
}
CFGBlock *CFGBuilder::VisitCompoundStmt(CompoundStmt *C) {
addLocalScopeAndDtors(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 NULL;
}
return LastBlock;
}
CFGBlock *CFGBuilder::VisitConditionalOperator(AbstractConditionalOperator *C,
AddStmtChoice asc) {
const BinaryConditionalOperator *BCO = dyn_cast<BinaryConditionalOperator>(C);
const OpaqueValueExpr *opaqueValue = (BCO ? BCO->getOpaqueValue() : NULL);
// Create the confluence block that will "merge" the results of the ternary
// expression.
CFGBlock *ConfluenceBlock = Block ? Block : createBlock();
appendStmt(ConfluenceBlock, C);
if (badCFG)
return 0;
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 = NULL;
CFGBlock *LHSBlock = 0;
const Expr *trueExpr = C->getTrueExpr();
if (trueExpr != opaqueValue) {
LHSBlock = Visit(C->getTrueExpr(), alwaysAdd);
if (badCFG)
return 0;
Block = NULL;
}
else
LHSBlock = ConfluenceBlock;
// Create the block for the RHS expression.
Succ = ConfluenceBlock;
CFGBlock *RHSBlock = Visit(C->getFalseExpr(), alwaysAdd);
if (badCFG)
return 0;
// 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, KnownVal.isFalse() ? NULL : LHSBlock);
addSuccessor(Block, KnownVal.isTrue() ? NULL : RHSBlock);
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 = 0;
// FIXME: Add a reverse iterator for DeclStmt to avoid this extra copy.
typedef SmallVector<Decl*,10> BufTy;
BufTy Buf(DS->decl_begin(), DS->decl_end());
for (BufTy::reverse_iterator I = Buf.rbegin(), E = Buf.rend(); I != E; ++I) {
// Get the alignment of the new DeclStmt, padding out to >=8 bytes.
unsigned A = llvm::AlignOf<DeclStmt>::Alignment < 8
? 8 : llvm::AlignOf<DeclStmt>::Alignment;
// 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));
// 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.");
Decl *D = DS->getSingleDecl();
if (isa<StaticAssertDecl>(D)) {
// static_asserts aren't added to the CFG because they do not impact
// runtime semantics.
return Block;
}
VarDecl *VD = dyn_cast<VarDecl>(DS->getSingleDecl());
if (!VD) {
autoCreateBlock();
appendStmt(Block, DS);
return Block;
}
bool IsReference = false;
bool HasTemporaries = false;
// Destructors of temporaries in initialization expression should be called
// after initialization finishes.
Expr *Init = VD->getInit();
if (Init) {
IsReference = VD->getType()->isReferenceType();
HasTemporaries = isa<ExprWithCleanups>(Init);
if (BuildOpts.AddImplicitDtors && HasTemporaries) {
// Generate destructors for temporaries in initialization expression.
VisitForTemporaryDtors(cast<ExprWithCleanups>(Init)->getSubExpr(),
IsReference);
}
}
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 != 0; VA = FindVA(VA->getElementType().getTypePtr()))
Block = addStmt(VA->getSizeExpr());
// Remove variable from local scope.
if (ScopePos && VD == *ScopePos)
++ScopePos;
return Block ? Block : LastBlock;
}
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 possible condition variable.
// Store scope position. Add implicit destructor.
if (VarDecl *VD = I->getConditionVariable()) {
LocalScope::const_iterator BeginScopePos = ScopePos;
addLocalScopeForVarDecl(VD);
addAutomaticObjDtors(ScopePos, BeginScopePos, I);
}
// The block we were processing is now finished. Make it the successor
// block.
if (Block) {
Succ = Block;
if (badCFG)
return 0;
}
// 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 = NULL;
// 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 0;
}
}
// Process the true branch.
CFGBlock *ThenBlock;
{
Stmt *Then = I->getThen();
assert(Then);
SaveAndRestore<CFGBlock*> sv(Succ);
Block = NULL;
// 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 0;
}
}
// 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());
// Now add the successors.
addSuccessor(Block, KnownVal.isFalse() ? NULL : ThenBlock);
addSuccessor(Block, KnownVal.isTrue()? NULL : ElseBlock);
// 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".
Block = addStmt(I->getCond());
// Finally, if the IfStmt contains a condition variable, add both the IfStmt
// and the condition variable initialization to the CFG.
if (VarDecl *VD = I->getConditionVariable()) {
if (Expr *Init = VD->getInit()) {
autoCreateBlock();
appendStmt(Block, I->getConditionVariableDeclStmt());
addStmt(Init);
}
}
return Block;
}
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);
// The Exit block is the only successor.
addAutomaticObjDtors(ScopePos, LocalScope::const_iterator(), R);
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 0;
// We set Block to NULL to allow lazy creation of a new block (if necessary);
Block = NULL;
// This block is now the implicit successor of other blocks.
Succ = LabelBlock;
return LabelBlock;
}
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 != 0)
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 = NULL;
// 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 0;
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);
// 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 *ExitConditionBlock = createBlock(false);
CFGBlock *EntryConditionBlock = ExitConditionBlock;
// Set the terminator for the "exit" condition block.
ExitConditionBlock->setTerminator(F);
// Now add the actual condition to the condition block. Because the condition
// itself may contain control-flow, new blocks may be created.
if (Stmt *C = F->getCond()) {
Block = ExitConditionBlock;
EntryConditionBlock = addStmt(C);
if (badCFG)
return 0;
assert(Block == EntryConditionBlock ||
(Block == 0 && EntryConditionBlock == Succ));
// 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) {
if (badCFG)
return 0;
}
}
// The condition block is the implicit successor for the loop body as well as
// any code above the loop.
Succ = EntryConditionBlock;
// See if this is a known constant.
TryResult KnownVal(true);
if (F->getCond())
KnownVal = tryEvaluateBool(F->getCond());
// Now create the loop body.
{
assert(F->getBody());
// Save the current values for Block, Succ, and continue targets.
SaveAndRestore<CFGBlock*> save_Block(Block), save_Succ(Succ);
SaveAndRestore<JumpTarget> save_continue(ContinueJumpTarget);
// Create a new block to contain the (bottom) of the loop body.
Block = NULL;
// Loop body should end with destructor of Condition variable (if any).
addAutomaticObjDtors(ScopePos, LoopBeginScopePos, F);
if (Stmt *I = F->getInc()) {
// Generate increment code in its own basic block. This is the target of
// continue statements.
Succ = addStmt(I);
} else {
// No increment code. Create a special, empty, block that is used as the
// target block for "looping back" to the start of the loop.
assert(Succ == EntryConditionBlock);
Succ = Block ? Block : createBlock();
}
// Finish up the increment (or empty) block if it hasn't been already.
if (Block) {
assert(Block == Succ);
if (badCFG)
return 0;
Block = 0;
}
ContinueJumpTarget = JumpTarget(Succ, ContinueScopePos);
// 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.block->setLoopTarget(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.
CFGBlock *BodyBlock = addStmt(F->getBody());
if (!BodyBlock)
BodyBlock = ContinueJumpTarget.block;//can happen for "for (...;...;...);"
else if (badCFG)
return 0;
// This new body block is a successor to our "exit" condition block.
addSuccessor(ExitConditionBlock, KnownVal.isFalse() ? NULL : BodyBlock);
}
// Link up the condition block with the code that follows the loop. (the
// false branch).
addSuccessor(ExitConditionBlock, KnownVal.isTrue() ? NULL : LoopSuccessor);
// 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 = NULL;
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
// T. jump to loop_entry
// loop_entry:
// 1. side-effects of element expression
// 1. ObjCForCollectionStmt [performs binding to newVariable]
// T. ObjCForCollectionStmt TB, FB [jumps to TB if newVariable != nil]
// TB:
// statements
// T. jump to loop_entry
// FB:
// what comes after
//
// and
//
// Type existingItem;
// for ( existingItem in expression ) { statements }
//
// becomes:
//
// the same with newVariable replaced with existingItem; the binding works
// the same except that for one ObjCForCollectionStmt::getElement() returns
// a DeclStmt and the other returns a DeclRefExpr.
//
CFGBlock *LoopSuccessor = 0;
if (Block) {
if (badCFG)
return 0;
LoopSuccessor = Block;
Block = 0;
} else
LoopSuccessor = Succ;
// Build the condition blocks.
CFGBlock *ExitConditionBlock = createBlock(false);
// Set the terminator for the "exit" condition block.
ExitConditionBlock->setTerminator(S);
// The last statement in the block should be the ObjCForCollectionStmt, which
// performs the actual binding to 'element' and determines if there are any
// more items in the collection.
appendStmt(ExitConditionBlock, S);
Block = ExitConditionBlock;
// Walk the 'element' expression to see if there are any side-effects. We
// generate new blocks as necessary. We DON'T add the statement by default to
// the CFG unless it contains control-flow.
CFGBlock *EntryConditionBlock = Visit(S->getElement(),
AddStmtChoice::NotAlwaysAdd);
if (Block) {
if (badCFG)
return 0;
Block = 0;
}
// The condition block is the implicit successor for the loop body as well as
// any code above the loop.
Succ = EntryConditionBlock;
// Now create the true branch.
{
// Save the current values for Succ, continue and break targets.
SaveAndRestore<CFGBlock*> save_Succ(Succ);
SaveAndRestore<JumpTarget> save_continue(ContinueJumpTarget),
save_break(BreakJumpTarget);
BreakJumpTarget = JumpTarget(LoopSuccessor, ScopePos);
ContinueJumpTarget = JumpTarget(EntryConditionBlock, ScopePos);
CFGBlock *BodyBlock = addStmt(S->getBody());
if (!BodyBlock)
BodyBlock = EntryConditionBlock; // can happen for "for (X in Y) ;"
else if (Block) {
if (badCFG)
return 0;
}
// This new body block is a successor to our "exit" condition block.
addSuccessor(ExitConditionBlock, BodyBlock);
}
// Link up the condition block with the code that follows the loop.
// (the false branch).
addSuccessor(ExitConditionBlock, LoopSuccessor);
// Now create a prologue block to contain the collection expression.
Block = createBlock();
return addStmt(S->getCollection());
}
CFGBlock *CFGBuilder::VisitObjCAutoreleasePoolStmt(ObjCAutoreleasePoolStmt *S) {
// Inline the body.
return addStmt(S->getSubStmt());
// TODO: consider adding cleanups for the end of @autoreleasepool scope.
}
CFGBlock *CFGBuilder::VisitObjCAtSynchronizedStmt(ObjCAtSynchronizedStmt *S) {
// FIXME: Add locking 'primitives' to CFG for @synchronized.
// Inline the body.
CFGBlock *SyncBlock = addStmt(S->getSynchBody());
// The sync body starts its own basic block. This makes it a little easier
// for diagnostic clients.
if (SyncBlock) {
if (badCFG)
return 0;
Block = 0;
Succ = SyncBlock;
}
// Add the @synchronized to the CFG.
autoCreateBlock();
appendStmt(Block, S);
// Inline the sync expression.
return addStmt(S->getSynchExpr());
}
CFGBlock *CFGBuilder::VisitObjCAtTryStmt(ObjCAtTryStmt *S) {
// FIXME
return NYS();
}
CFGBlock *CFGBuilder::VisitPseudoObjectExpr(PseudoObjectExpr *E) {
autoCreateBlock();
// Add the PseudoObject as the last thing.
appendStmt(Block, E);
CFGBlock *lastBlock = Block;
// Before that, evaluate all of the semantics in order. In
// CFG-land, that means appending them in reverse order.
for (unsigned i = E->getNumSemanticExprs(); i != 0; ) {
Expr *Semantic = E->getSemanticExpr(--i);
// If the semantic is an opaque value, we're being asked to bind
// it to its source expression.
if (OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(Semantic))
Semantic = OVE->getSourceExpr();
if (CFGBlock *B = Visit(Semantic))
lastBlock = B;
}
return lastBlock;
}
CFGBlock *CFGBuilder::VisitWhileStmt(WhileStmt *W) {
CFGBlock *LoopSuccessor = NULL;
// 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 possible condition variable.
// Store scope position for continue statement.
LocalScope::const_iterator LoopBeginScopePos = ScopePos;
if (VarDecl *VD = W->getConditionVariable()) {
addLocalScopeForVarDecl(VD);
addAutomaticObjDtors(ScopePos, LoopBeginScopePos, W);
}
// "while" is a control-flow statement. Thus we stop processing the current
// block.
if (Block) {
if (badCFG)
return 0;
LoopSuccessor = Block;
Block = 0;
} else
LoopSuccessor = Succ;
// 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 *ExitConditionBlock = createBlock(false);
CFGBlock *EntryConditionBlock = ExitConditionBlock;
// Set the terminator for the "exit" condition block.
ExitConditionBlock->setTerminator(W);
// 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.
if (Stmt *C = W->getCond()) {
Block = ExitConditionBlock;
EntryConditionBlock = addStmt(C);
// The condition might finish the current 'Block'.
Block = EntryConditionBlock;
// If this block contains a condition variable, add both the condition
// variable and initializer to the CFG.
if (VarDecl *VD = W->getConditionVariable()) {
if (Expr *Init = VD->getInit()) {
autoCreateBlock();
appendStmt(Block, W->getConditionVariableDeclStmt());
EntryConditionBlock = addStmt(Init);
assert(Block == EntryConditionBlock);
}
}
if (Block) {
if (badCFG)
return 0;
}
}
// The condition block is the implicit successor for the loop body as well as
// any code above the loop.
Succ = EntryConditionBlock;
// See if this is a known constant.
const TryResult& KnownVal = tryEvaluateBool(W->getCond());
// Process the loop body.
{
assert(W->getBody());
// Save the current values for Block, Succ, and continue and break targets
SaveAndRestore<CFGBlock*> save_Block(Block), save_Succ(Succ);
SaveAndRestore<JumpTarget> save_continue(ContinueJumpTarget),
save_break(BreakJumpTarget);
// Create an empty block to represent the transition block for looping back
// to the head of the loop.
Block = 0;
assert(Succ == EntryConditionBlock);
Succ = createBlock();
Succ->setLoopTarget(W);
ContinueJumpTarget = JumpTarget(Succ, LoopBeginScopePos);
// All breaks should go to the code following the loop.
BreakJumpTarget = JumpTarget(LoopSuccessor, ScopePos);
// NULL out Block to force lazy instantiation of blocks for the body.
Block = NULL;
// Loop body should end with destructor of Condition variable (if any).
addAutomaticObjDtors(ScopePos, LoopBeginScopePos, W);
// If body is not a compound statement create implicit scope
// and add destructors.
if (!isa<CompoundStmt>(W->getBody()))
addLocalScopeAndDtors(W->getBody());
// Create the body. The returned block is the entry to the loop body.
CFGBlock *BodyBlock = addStmt(W->getBody());
if (!BodyBlock)
BodyBlock = ContinueJumpTarget.block; // can happen for "while(...) ;"
else if (Block) {
if (badCFG)
return 0;
}
// Add the loop body entry as a successor to the condition.
addSuccessor(ExitConditionBlock, KnownVal.isFalse() ? NULL : BodyBlock);
}
// Link up the condition block with the code that follows the loop. (the
// false branch).
addSuccessor(ExitConditionBlock, KnownVal.isTrue() ? NULL : LoopSuccessor);
// There can be no more statements in the condition block since we loop back
// to this block. NULL out Block to force lazy creation of another block.
Block = NULL;
// Return the condition block, which is the dominating block for the loop.
Succ = EntryConditionBlock;
return EntryConditionBlock;
}
CFGBlock *CFGBuilder::VisitObjCAtCatchStmt(ObjCAtCatchStmt *S) {
// FIXME: For now we pretend that @catch and the code it contains does not
// exit.
return Block;
}
CFGBlock *CFGBuilder::VisitObjCAtThrowStmt(ObjCAtThrowStmt *S) {
// FIXME: This isn't complete. We basically treat @throw like a return
// statement.
// If we were in the middle of a block we stop processing that block.
if (badCFG)
return 0;
// Create the new block.
Block = createBlock(false);
// The Exit block is the only successor.
addSuccessor(Block, &cfg->getExit());
// Add the statement to the block. This may create new blocks if S contains
// control-flow (short-circuit operations).
return VisitStmt(S, AddStmtChoice::AlwaysAdd);
}
CFGBlock *CFGBuilder::VisitCXXThrowExpr(CXXThrowExpr *T) {
// If we were in the middle of a block we stop processing that block.
if (badCFG)
return 0;
// Create the new block.
Block = createBlock(false);
if (TryTerminatedBlock)
// The current try statement is the only successor.
addSuccessor(Block, TryTerminatedBlock);
else
// otherwise the Exit block is the only successor.
addSuccessor(Block, &cfg->getExit());
// Add the statement to the block. This may create new blocks if S contains
// control-flow (short-circuit operations).
return VisitStmt(T, AddStmtChoice::AlwaysAdd);
}
CFGBlock *CFGBuilder::VisitDoStmt(DoStmt *D) {
CFGBlock *LoopSuccessor = NULL;
// "do...while" is a control-flow statement. Thus we stop processing the
// current block.
if (Block) {
if (badCFG)
return 0;
LoopSuccessor = Block;
} else
LoopSuccessor = Succ;
// 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 *ExitConditionBlock = createBlock(false);
CFGBlock *EntryConditionBlock = ExitConditionBlock;
// Set the terminator for the "exit" condition block.
ExitConditionBlock->setTerminator(D);
// Now add the actual condition to the condition block. Because the condition
// itself may contain control-flow, new blocks may be created.
if (Stmt *C = D->getCond()) {
Block = ExitConditionBlock;
EntryConditionBlock = addStmt(C);
if (Block) {
if (badCFG)
return 0;
}
}
// The condition block is the implicit successor for the loop body.
Succ = EntryConditionBlock;
// See if this is a known constant.
const TryResult &KnownVal = tryEvaluateBool(D->getCond());
// Process the loop body.
CFGBlock *BodyBlock = NULL;
{
assert(D->getBody());
// Save the current values for Block, Succ, and continue and break targets
SaveAndRestore<CFGBlock*> save_Block(Block), save_Succ(Succ);
SaveAndRestore<JumpTarget> save_continue(ContinueJumpTarget),
save_break(BreakJumpTarget);
// All continues within this loop should go to the condition block
ContinueJumpTarget = JumpTarget(EntryConditionBlock, ScopePos);
// All breaks should go to the code following the loop.
BreakJumpTarget = JumpTarget(LoopSuccessor, ScopePos);
// NULL out Block to force lazy instantiation of blocks for the body.
Block = NULL;
// If body is not a compound statement create implicit scope
// and add destructors.
if (!isa<CompoundStmt>(D->getBody()))
addLocalScopeAndDtors(D->getBody());
// Create the body. The returned block is the entry to the loop body.
BodyBlock = addStmt(D->getBody());
if (!BodyBlock)
BodyBlock = EntryConditionBlock; // can happen for "do ; while(...)"
else if (Block) {
if (badCFG)
return 0;
}
if (!KnownVal.isFalse()) {
// Add an intermediate block between the BodyBlock and the
// ExitConditionBlock to represent the "loop back" transition. Create an
// empty block to represent the transition block for looping back to the
// head of the loop.
// FIXME: Can we do this more efficiently without adding another block?
Block = NULL;
Succ = BodyBlock;
CFGBlock *LoopBackBlock = createBlock();
LoopBackBlock->setLoopTarget(D);
// Add the loop body entry as a successor to the condition.
addSuccessor(ExitConditionBlock, LoopBackBlock);
}
else
addSuccessor(ExitConditionBlock, NULL);
}
// Link up the condition block with the code that follows the loop.
// (the false branch).
addSuccessor(ExitConditionBlock, KnownVal.isTrue() ? NULL : LoopSuccessor);
// There can be no more statements in the body block(s) since we loop back to
// the body. NULL out Block to force lazy creation of another block.
Block = NULL;
// Return the loop body, which is the dominating block for the loop.
Succ = BodyBlock;
return BodyBlock;
}
CFGBlock *CFGBuilder::VisitContinueStmt(ContinueStmt *C) {
// "continue" is a control-flow statement. Thus we stop processing the
// current block.
if (badCFG)
return 0;
// Now create a new block that ends with the continue statement.
Block = createBlock(false);
Block->setTerminator(C);
// If there is no target for the continue, then we are looking at an
// incomplete AST. This means the CFG cannot be constructed.
if (ContinueJumpTarget.block) {
addAutomaticObjDtors(ScopePos, ContinueJumpTarget.scopePosition, C);
addSuccessor(Block, ContinueJumpTarget.block);
} else
badCFG = true;
return Block;
}
CFGBlock *CFGBuilder::VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *E,
AddStmtChoice asc) {
if (asc.alwaysAdd(*this, E)) {
autoCreateBlock();
appendStmt(Block, E);
}
// VLA types have expressions that must be evaluated.
CFGBlock *lastBlock = Block;
if (E->isArgumentType()) {
for (const VariableArrayType *VA =FindVA(E->getArgumentType().getTypePtr());
VA != 0; VA = FindVA(VA->getElementType().getTypePtr()))
lastBlock = addStmt(VA->getSizeExpr());
}
return lastBlock;
}
/// VisitStmtExpr - Utility method to handle (nested) statement
/// expressions (a GCC extension).
CFGBlock *CFGBuilder::VisitStmtExpr(StmtExpr *SE, AddStmtChoice asc) {
if (asc.alwaysAdd(*this, SE)) {
autoCreateBlock();
appendStmt(Block, SE);
}
return VisitCompoundStmt(SE->getSubStmt());
}
CFGBlock *CFGBuilder::VisitSwitchStmt(SwitchStmt *Terminator) {
// "switch" is a control-flow statement. Thus we stop processing the current
// block.
CFGBlock *SwitchSuccessor = NULL;
// 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 possible condition variable.
// Store scope position. Add implicit destructor.
if (VarDecl *VD = Terminator->getConditionVariable()) {
LocalScope::const_iterator SwitchBeginScopePos = ScopePos;
addLocalScopeForVarDecl(VD);
addAutomaticObjDtors(ScopePos, SwitchBeginScopePos, Terminator);
}
if (Block) {
if (badCFG)
return 0;
SwitchSuccessor = Block;
} else SwitchSuccessor = Succ;
// Save the current "switch" context.
SaveAndRestore<CFGBlock*> save_switch(SwitchTerminatedBlock),
save_default(DefaultCaseBlock);
SaveAndRestore<JumpTarget> save_break(BreakJumpTarget);
// Set the "default" case to be the block after the switch statement. If the
// switch statement contains a "default:", this value will be overwritten with
// the block for that code.
DefaultCaseBlock = SwitchSuccessor;
// Create a new block that will contain the switch statement.
SwitchTerminatedBlock = createBlock(false);
// Now process the switch body. The code after the switch is the implicit
// successor.
Succ = SwitchSuccessor;
BreakJumpTarget = JumpTarget(SwitchSuccessor, ScopePos);
// When visiting the body, the case statements should automatically get linked
// up to the switch. We also don't keep a pointer to the body, since all
// control-flow from the switch goes to case/default statements.
assert(Terminator->getBody() && "switch must contain a non-NULL body");
Block = NULL;
// For pruning unreachable case statements, save the current state
// for tracking the condition value.
SaveAndRestore<bool> save_switchExclusivelyCovered(switchExclusivelyCovered,
false);
// Determine if the switch condition can be explicitly evaluated.
assert(Terminator->getCond() && "switch condition must be non-NULL");
Expr::EvalResult result;
bool b = tryEvaluate(Terminator->getCond(), result);
SaveAndRestore<Expr::EvalResult*> save_switchCond(switchCond,
b ? &result : 0);
// If body is not a compound statement create implicit scope
// and add destructors.
if (!isa<CompoundStmt>(Terminator->getBody()))
addLocalScopeAndDtors(Terminator->getBody());
addStmt(Terminator->getBody());
if (Block) {
if (badCFG)
return 0;
}
// If we have no "default:" case, the default transition is to the code
// following the switch body. Moreover, take into account if all the
// cases of a switch are covered (e.g., switching on an enum value).
addSuccessor(SwitchTerminatedBlock,
switchExclusivelyCovered || Terminator->isAllEnumCasesCovered()
? 0 : DefaultCaseBlock);
// Add the terminator and condition in the switch block.
SwitchTerminatedBlock->setTerminator(Terminator);
Block = SwitchTerminatedBlock;
Block = addStmt(Terminator->getCond());
// Finally, if the SwitchStmt contains a condition variable, add both the
// SwitchStmt and the condition variable initialization to the CFG.
if (VarDecl *VD = Terminator->getConditionVariable()) {
if (Expr *Init = VD->getInit()) {
autoCreateBlock();
appendStmt(Block, Terminator->getConditionVariableDeclStmt());
addStmt(Init);
}
}
return Block;
}
static bool shouldAddCase(bool &switchExclusivelyCovered,
const Expr::EvalResult *switchCond,
const CaseStmt *CS,
ASTContext &Ctx) {
if (!switchCond)
return true;
bool addCase = false;
if (!switchExclusivelyCovered) {
if (switchCond->Val.isInt()) {
// Evaluate the LHS of the case value.
const llvm::APSInt &lhsInt = CS->getLHS()->EvaluateKnownConstInt(Ctx);
const llvm::APSInt &condInt = switchCond->Val.getInt();
if (condInt == lhsInt) {
addCase = true;
switchExclusivelyCovered = true;
}
else if (condInt < lhsInt) {
if (const Expr *RHS = CS->getRHS()) {
// Evaluate the RHS of the case value.
const llvm::APSInt &V2 = RHS->EvaluateKnownConstInt(Ctx);
if (V2 <= condInt) {
addCase = true;
switchExclusivelyCovered = true;
}
}
}
}
else
addCase = true;
}
return addCase;
}
CFGBlock *CFGBuilder::VisitCaseStmt(CaseStmt *CS) {
// CaseStmts are essentially labels, so they are the first statement in a
// block.
CFGBlock *TopBlock = 0, *LastBlock = 0;
if (Stmt *Sub = CS->getSubStmt()) {
// For deeply nested chains of CaseStmts, instead of doing a recursion
// (which can blow out the stack), manually unroll and create blocks
// along the way.
while (isa<CaseStmt>(Sub)) {
CFGBlock *currentBlock = createBlock(false);
currentBlock->setLabel(CS);
if (TopBlock)
addSuccessor(LastBlock, currentBlock);
else
TopBlock = currentBlock;
addSuccessor(SwitchTerminatedBlock,
shouldAddCase(switchExclusivelyCovered, switchCond,
CS, *Context)
? currentBlock : 0);
LastBlock = currentBlock;
CS = cast<CaseStmt>(Sub);
Sub = CS->getSubStmt();
}
addStmt(Sub);
}
CFGBlock *CaseBlock = Block;
if (!CaseBlock)
CaseBlock = createBlock();
// Cases statements partition blocks, so this is the top of the basic block we
// were processing (the "case XXX:" is the label).
CaseBlock->setLabel(CS);
if (badCFG)
return 0;
// Add this block to the list of successors for the block with the switch
// statement.
assert(SwitchTerminatedBlock);
addSuccessor(SwitchTerminatedBlock,
shouldAddCase(switchExclusivelyCovered, switchCond,
CS, *Context)
? CaseBlock : 0);
// We set Block to NULL to allow lazy creation of a new block (if necessary)
Block = NULL;
if (TopBlock) {
addSuccessor(LastBlock, CaseBlock);
Succ = TopBlock;
} else {
// This block is now the implicit successor of other blocks.
Succ = CaseBlock;
}
return Succ;
}
CFGBlock *CFGBuilder::VisitDefaultStmt(DefaultStmt *Terminator) {
if (Terminator->getSubStmt())
addStmt(Terminator->getSubStmt());
DefaultCaseBlock = Block;
if (!DefaultCaseBlock)
DefaultCaseBlock = createBlock();
// Default statements partition blocks, so this is the top of the basic block
// we were processing (the "default:" is the label).
DefaultCaseBlock->setLabel(Terminator);
if (badCFG)
return 0;
// Unlike case statements, we don't add the default block to the successors
// for the switch statement immediately. This is done when we finish
// processing the switch statement. This allows for the default case
// (including a fall-through to the code after the switch statement) to always
// be the last successor of a switch-terminated block.
// We set Block to NULL to allow lazy creation of a new block (if necessary)
Block = NULL;
// This block is now the implicit successor of other blocks.
Succ = DefaultCaseBlock;
return DefaultCaseBlock;
}
CFGBlock *CFGBuilder::VisitCXXTryStmt(CXXTryStmt *Terminator) {
// "try"/"catch" is a control-flow statement. Thus we stop processing the
// current block.
CFGBlock *TrySuccessor = NULL;
if (Block) {
if (badCFG)
return 0;
TrySuccessor = Block;
} else TrySuccessor = Succ;
CFGBlock *PrevTryTerminatedBlock = TryTerminatedBlock;
// Create a new block that will contain the try statement.
CFGBlock *NewTryTerminatedBlock = createBlock(false);
// Add the terminator in the try block.
NewTryTerminatedBlock->setTerminator(Terminator);
bool HasCatchAll = false;
for (unsigned h = 0; h <Terminator->getNumHandlers(); ++h) {
// The code after the try is the implicit successor.
Succ = TrySuccessor;
CXXCatchStmt *CS = Terminator->getHandler(h);
if (CS->getExceptionDecl() == 0) {
HasCatchAll