//===--- 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/Support/SaveAndRestore.h"
#include "clang/Analysis/CFG.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/AST/PrettyPrinter.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 AddStmtChoice {
public:
enum Kind { NotAlwaysAdd = 0, AlwaysAdd, AlwaysAddAsLValue };
public:
AddStmtChoice(Kind kind) : k(kind) {}
bool alwaysAdd() const { return k != NotAlwaysAdd; }
bool asLValue() const { return k == AlwaysAddAsLValue; }
private:
Kind k;
};
/// 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 {
ASTContext *Context;
llvm::OwningPtr<CFG> cfg;
CFGBlock* Block;
CFGBlock* Succ;
CFGBlock* ContinueTargetBlock;
CFGBlock* BreakTargetBlock;
CFGBlock* SwitchTerminatedBlock;
CFGBlock* DefaultCaseBlock;
CFGBlock* TryTerminatedBlock;
// LabelMap records the mapping from Label expressions to their blocks.
typedef llvm::DenseMap<LabelStmt*,CFGBlock*> 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<CFGBlock*> BackpatchBlocksTy;
BackpatchBlocksTy BackpatchBlocks;
// A list of labels whose address has been taken (for indirect gotos).
typedef llvm::SmallPtrSet<LabelStmt*,5> LabelSetTy;
LabelSetTy AddressTakenLabels;
public:
explicit CFGBuilder() : cfg(new CFG()), // crew a new CFG
Block(NULL), Succ(NULL),
ContinueTargetBlock(NULL), BreakTargetBlock(NULL),
SwitchTerminatedBlock(NULL), DefaultCaseBlock(NULL),
TryTerminatedBlock(NULL) {}
// buildCFG - Used by external clients to construct the CFG.
CFG* buildCFG(const Decl *D, Stmt *Statement, ASTContext *C, bool AddEHEdges,
bool AddScopes);
private:
// Visitors to walk an AST and construct the CFG.
CFGBlock *VisitAddrLabelExpr(AddrLabelExpr *A, AddStmtChoice asc);
CFGBlock *VisitBinaryOperator(BinaryOperator *B, AddStmtChoice asc);
CFGBlock *VisitBlockExpr(BlockExpr* E, 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(ConditionalOperator *C,
AddStmtChoice asc);
CFGBlock *VisitContinueStmt(ContinueStmt *C);
CFGBlock *VisitCXXCatchStmt(CXXCatchStmt *S);
CFGBlock *VisitCXXThrowExpr(CXXThrowExpr *T);
CFGBlock *VisitCXXTryStmt(CXXTryStmt *S);
CFGBlock *VisitDeclStmt(DeclStmt *DS);
CFGBlock *VisitDeclSubExpr(Decl* D);
CFGBlock *VisitDefaultStmt(DefaultStmt *D);
CFGBlock *VisitDoStmt(DoStmt *D);
CFGBlock *VisitForStmt(ForStmt *F);
CFGBlock *VisitGotoStmt(GotoStmt* G);
CFGBlock *VisitIfStmt(IfStmt *I);
CFGBlock *VisitIndirectGotoStmt(IndirectGotoStmt *I);
CFGBlock *VisitLabelStmt(LabelStmt *L);
CFGBlock *VisitObjCAtCatchStmt(ObjCAtCatchStmt *S);
CFGBlock *VisitObjCAtSynchronizedStmt(ObjCAtSynchronizedStmt *S);
CFGBlock *VisitObjCAtThrowStmt(ObjCAtThrowStmt *S);
CFGBlock *VisitObjCAtTryStmt(ObjCAtTryStmt *S);
CFGBlock *VisitObjCForCollectionStmt(ObjCForCollectionStmt *S);
CFGBlock *VisitReturnStmt(ReturnStmt* R);
CFGBlock *VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E, AddStmtChoice asc);
CFGBlock *VisitStmtExpr(StmtExpr *S, AddStmtChoice asc);
CFGBlock *VisitSwitchStmt(SwitchStmt *S);
CFGBlock *VisitWhileStmt(WhileStmt *W);
CFGBlock *Visit(Stmt *S, AddStmtChoice asc = AddStmtChoice::NotAlwaysAdd);
CFGBlock *VisitStmt(Stmt *S, AddStmtChoice asc);
CFGBlock *VisitChildren(Stmt* S);
// NYS == Not Yet Supported
CFGBlock* NYS() {
badCFG = true;
return Block;
}
CFGBlock *StartScope(Stmt *S, CFGBlock *B) {
if (!AddScopes)
return B;
if (B == 0)
B = createBlock();
B->StartScope(S, cfg->getBumpVectorContext());
return B;
}
void EndScope(Stmt *S) {
if (!AddScopes)
return;
if (Block == 0)
Block = createBlock();
Block->EndScope(S, cfg->getBumpVectorContext());
}
void autoCreateBlock() { if (!Block) Block = createBlock(); }
CFGBlock *createBlock(bool add_successor = true);
bool FinishBlock(CFGBlock* B);
CFGBlock *addStmt(Stmt *S, AddStmtChoice asc = AddStmtChoice::AlwaysAdd) {
return Visit(S, asc);
}
void AppendStmt(CFGBlock *B, Stmt *S,
AddStmtChoice asc = AddStmtChoice::AlwaysAdd) {
B->appendStmt(S, cfg->getBumpVectorContext(), asc.asLValue());
}
void AddSuccessor(CFGBlock *B, CFGBlock *S) {
B->addSuccessor(S, cfg->getBumpVectorContext());
}
/// 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;
}
};
/// 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) {
Expr::EvalResult Result;
if (!S->isTypeDependent() && !S->isValueDependent() &&
S->Evaluate(Result, *Context) && Result.Val.isInt())
return Result.Val.getInt().getBoolValue();
return TryResult();
}
bool badCFG;
// True iff EH edges on CallExprs should be added to the CFG.
bool AddEHEdges;
// True iff scope start and scope end notes should be added to the CFG.
bool AddScopes;
};
// FIXME: Add support for dependent-sized array types in C++?
// Does it even make sense to build a CFG for an uninstantiated template?
static VariableArrayType* FindVA(Type* t) {
while (ArrayType* vt = dyn_cast<ArrayType>(t)) {
if (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, ASTContext* C,
bool addehedges, bool AddScopes) {
AddEHEdges = addehedges;
Context = C;
assert(cfg.get());
if (!Statement)
return NULL;
this->AddScopes = AddScopes;
badCFG = false;
// 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.
// Visit the statements and create the CFG.
CFGBlock* B = addStmt(Statement);
if (const CXXConstructorDecl *CD = dyn_cast_or_null<CXXConstructorDecl>(D)) {
// FIXME: Add code for base initializers and member initializers.
(void)CD;
}
if (!B)
B = Succ;
if (B) {
// Finalize the last constructed block. This usually involves reversing the
// order of the statements in the block.
if (Block) FinishBlock(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;
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;
AddSuccessor(B, LI->second);
}
// 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);
}
Succ = B;
}
// Create an empty entry block that has no predecessors.
cfg->setEntry(createBlock());
return badCFG ? NULL : 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;
}
/// FinishBlock - "Finalize" the block by checking if we have a bad CFG.
bool CFGBuilder::FinishBlock(CFGBlock* B) {
if (badCFG)
return false;
assert(B);
return true;
}
/// 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) {
tryAgain:
switch (S->getStmtClass()) {
default:
return VisitStmt(S, asc);
case Stmt::AddrLabelExprClass:
return VisitAddrLabelExpr(cast<AddrLabelExpr>(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:
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::CXXThrowExprClass:
return VisitCXXThrowExpr(cast<CXXThrowExpr>(S));
case Stmt::CXXTryStmtClass:
return VisitCXXTryStmt(cast<CXXTryStmt>(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::IndirectGotoStmtClass:
return VisitIndirectGotoStmt(cast<IndirectGotoStmt>(S));
case Stmt::LabelStmtClass:
return VisitLabelStmt(cast<LabelStmt>(S));
case Stmt::ObjCAtCatchStmtClass:
return VisitObjCAtCatchStmt(cast<ObjCAtCatchStmt>(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::ParenExprClass:
S = cast<ParenExpr>(S)->getSubExpr();
goto tryAgain;
case Stmt::NullStmtClass:
return Block;
case Stmt::ReturnStmtClass:
return VisitReturnStmt(cast<ReturnStmt>(S));
case Stmt::SizeOfAlignOfExprClass:
return VisitSizeOfAlignOfExpr(cast<SizeOfAlignOfExpr>(S), asc);
case Stmt::StmtExprClass:
return VisitStmtExpr(cast<StmtExpr>(S), asc);
case Stmt::SwitchStmtClass:
return VisitSwitchStmt(cast<SwitchStmt>(S));
case Stmt::WhileStmtClass:
return VisitWhileStmt(cast<WhileStmt>(S));
}
}
CFGBlock *CFGBuilder::VisitStmt(Stmt *S, AddStmtChoice asc) {
if (asc.alwaysAdd()) {
autoCreateBlock();
AppendStmt(Block, S, asc);
}
return VisitChildren(S);
}
/// VisitChildren - Visit the children of a Stmt.
CFGBlock *CFGBuilder::VisitChildren(Stmt* Terminator) {
CFGBlock *B = Block;
for (Stmt::child_iterator I = Terminator->child_begin(),
E = Terminator->child_end(); I != E; ++I) {
if (*I) B = Visit(*I);
}
return B;
}
CFGBlock *CFGBuilder::VisitAddrLabelExpr(AddrLabelExpr *A,
AddStmtChoice asc) {
AddressTakenLabels.insert(A->getLabel());
if (asc.alwaysAdd()) {
autoCreateBlock();
AppendStmt(Block, A, asc);
}
return Block;
}
CFGBlock *CFGBuilder::VisitBinaryOperator(BinaryOperator *B,
AddStmtChoice asc) {
if (B->isLogicalOp()) { // && or ||
CFGBlock* ConfluenceBlock = Block ? Block : createBlock();
AppendStmt(ConfluenceBlock, B, asc);
if (!FinishBlock(ConfluenceBlock))
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 (!FinishBlock(RHSBlock))
return 0;
// See if this is a known constant.
TryResult KnownVal = TryEvaluateBool(B->getLHS());
if (KnownVal.isKnown() && (B->getOpcode() == BinaryOperator::LOr))
KnownVal.negate();
// Now link the LHSBlock with RHSBlock.
if (B->getOpcode() == BinaryOperator::LOr) {
AddSuccessor(LHSBlock, KnownVal.isTrue() ? NULL : ConfluenceBlock);
AddSuccessor(LHSBlock, KnownVal.isFalse() ? NULL : RHSBlock);
} else {
assert(B->getOpcode() == BinaryOperator::LAnd);
AddSuccessor(LHSBlock, KnownVal.isFalse() ? NULL : RHSBlock);
AddSuccessor(LHSBlock, KnownVal.isTrue() ? NULL : ConfluenceBlock);
}
// Generate the blocks for evaluating the LHS.
Block = LHSBlock;
return addStmt(B->getLHS());
}
else if (B->getOpcode() == BinaryOperator::Comma) { // ,
autoCreateBlock();
AppendStmt(Block, B, asc);
addStmt(B->getRHS());
return addStmt(B->getLHS());
}
return VisitStmt(B, asc);
}
CFGBlock *CFGBuilder::VisitBlockExpr(BlockExpr *E, AddStmtChoice asc) {
if (asc.alwaysAdd()) {
autoCreateBlock();
AppendStmt(Block, E, asc);
}
return Block;
}
CFGBlock *CFGBuilder::VisitBreakStmt(BreakStmt *B) {
// "break" is a control-flow statement. Thus we stop processing the current
// block.
if (Block && !FinishBlock(Block))
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 (BreakTargetBlock)
AddSuccessor(Block, BreakTargetBlock);
else
badCFG = true;
return Block;
}
static bool CanThrow(Expr *E) {
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->hasEmptyExceptionSpec())
return false;
}
return true;
}
CFGBlock *CFGBuilder::VisitCallExpr(CallExpr *C, AddStmtChoice asc) {
// If this is a call to a no-return function, this stops the block here.
bool NoReturn = false;
if (C->getCallee()->getType().getNoReturnAttr()) {
NoReturn = true;
}
bool AddEHEdge = false;
// Languages without exceptions are assumed to not throw.
if (Context->getLangOptions().Exceptions) {
if (AddEHEdges)
AddEHEdge = true;
}
if (FunctionDecl *FD = C->getDirectCallee()) {
if (FD->hasAttr<NoReturnAttr>())
NoReturn = true;
if (FD->hasAttr<NoThrowAttr>())
AddEHEdge = false;
}
if (!CanThrow(C->getCallee()))
AddEHEdge = false;
if (!NoReturn && !AddEHEdge)
return VisitStmt(C, asc);
if (Block) {
Succ = Block;
if (!FinishBlock(Block))
return 0;
}
Block = createBlock(!NoReturn);
AppendStmt(Block, C, asc);
if (NoReturn) {
// Wire this to the exit block directly.
AddSuccessor(Block, &cfg->getExit());
}
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, asc);
if (!FinishBlock(ConfluenceBlock))
return 0;
Succ = ConfluenceBlock;
Block = NULL;
CFGBlock* LHSBlock = addStmt(C->getLHS());
if (!FinishBlock(LHSBlock))
return 0;
Succ = ConfluenceBlock;
Block = NULL;
CFGBlock* RHSBlock = addStmt(C->getRHS());
if (!FinishBlock(RHSBlock))
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) {
EndScope(C);
CFGBlock* LastBlock = Block;
for (CompoundStmt::reverse_body_iterator I=C->body_rbegin(), E=C->body_rend();
I != E; ++I ) {
LastBlock = addStmt(*I);
if (badCFG)
return NULL;
}
LastBlock = StartScope(C, LastBlock);
return LastBlock;
}
CFGBlock *CFGBuilder::VisitConditionalOperator(ConditionalOperator *C,
AddStmtChoice asc) {
// Create the confluence block that will "merge" the results of the ternary
// expression.
CFGBlock* ConfluenceBlock = Block ? Block : createBlock();
AppendStmt(ConfluenceBlock, C, asc);
if (!FinishBlock(ConfluenceBlock))
return 0;
// 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 = NULL;
if (C->getLHS()) {
LHSBlock = addStmt(C->getLHS());
if (!FinishBlock(LHSBlock))
return 0;
Block = NULL;
}
// Create the block for the RHS expression.
Succ = ConfluenceBlock;
CFGBlock* RHSBlock = addStmt(C->getRHS());
if (!FinishBlock(RHSBlock))
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());
if (LHSBlock) {
AddSuccessor(Block, KnownVal.isFalse() ? NULL : LHSBlock);
} else {
if (KnownVal.isFalse()) {
// If we know the condition is false, add NULL as the successor for
// the block containing the condition. In this case, the confluence
// block will have just one predecessor.
AddSuccessor(Block, 0);
assert(ConfluenceBlock->pred_size() == 1);
} else {
// If we have no LHS expression, add the ConfluenceBlock as a direct
// successor for the block containing the condition. Moreover, we need to
// reverse the order of the predecessors in the ConfluenceBlock because
// the RHSBlock will have been added to the succcessors already, and we
// want the first predecessor to the the block containing the expression
// for the case when the ternary expression evaluates to true.
AddSuccessor(Block, ConfluenceBlock);
assert(ConfluenceBlock->pred_size() == 2);
std::reverse(ConfluenceBlock->pred_begin(),
ConfluenceBlock->pred_end());
}
}
AddSuccessor(Block, KnownVal.isTrue() ? NULL : RHSBlock);
Block->setTerminator(C);
return addStmt(C->getCond());
}
CFGBlock *CFGBuilder::VisitDeclStmt(DeclStmt *DS) {
autoCreateBlock();
if (DS->isSingleDecl()) {
AppendStmt(Block, DS);
return VisitDeclSubExpr(DS->getSingleDecl());
}
CFGBlock *B = 0;
// FIXME: Add a reverse iterator for DeclStmt to avoid this extra copy.
typedef llvm::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.
AppendStmt(Block, DSNew);
B = VisitDeclSubExpr(D);
}
return B;
}
/// VisitDeclSubExpr - Utility method to add block-level expressions for
/// initializers in Decls.
CFGBlock *CFGBuilder::VisitDeclSubExpr(Decl* D) {
assert(Block);
VarDecl *VD = dyn_cast<VarDecl>(D);
if (!VD)
return Block;
Expr *Init = VD->getInit();
if (Init) {
// Optimization: Don't create separate block-level statements for literals.
switch (Init->getStmtClass()) {
case Stmt::IntegerLiteralClass:
case Stmt::CharacterLiteralClass:
case Stmt::StringLiteralClass:
break;
default:
Block = addStmt(Init,
VD->getType()->isReferenceType()
? AddStmtChoice::AlwaysAddAsLValue
: AddStmtChoice::AlwaysAdd);
}
}
// If the type of VD is a VLA, then we must process its size expressions.
for (VariableArrayType* VA = FindVA(VD->getType().getTypePtr()); VA != 0;
VA = FindVA(VA->getElementType().getTypePtr()))
Block = addStmt(VA->getSizeExpr());
return Block;
}
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.
// The block we were proccessing is now finished. Make it the successor
// block.
if (Block) {
Succ = Block;
if (!FinishBlock(Block))
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;
ElseBlock = addStmt(Else);
if (!ElseBlock) // Can occur when the Else body has all NullStmts.
ElseBlock = sv.get();
else if (Block) {
if (!FinishBlock(ElseBlock))
return 0;
}
}
// Process the true branch.
CFGBlock* ThenBlock;
{
Stmt* Then = I->getThen();
assert(Then);
SaveAndRestore<CFGBlock*> sv(Succ);
Block = NULL;
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 (!FinishBlock(ThenBlock))
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, AddStmtChoice::AlwaysAdd);
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.
if (Block)
FinishBlock(Block);
// Create the new block.
Block = createBlock(false);
// The Exit block is the only successor.
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) == LabelMap.end() && "label already in map");
LabelMap[ L ] = LabelBlock;
// 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 (!FinishBlock(LabelBlock))
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::VisitGotoStmt(GotoStmt* G) {
// Goto is a control-flow statement. Thus we stop processing the current
// block and create a new one.
if (Block)
FinishBlock(Block);
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(Block);
else
AddSuccessor(Block, I->second);
return Block;
}
CFGBlock* CFGBuilder::VisitForStmt(ForStmt* F) {
CFGBlock* LoopSuccessor = NULL;
// "for" is a control-flow statement. Thus we stop processing the current
// block.
if (Block) {
if (!FinishBlock(Block))
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(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);
assert(Block == EntryConditionBlock);
// 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, AddStmtChoice::AlwaysAdd);
EntryConditionBlock = addStmt(Init);
assert(Block == EntryConditionBlock);
}
}
if (Block) {
if (!FinishBlock(EntryConditionBlock))
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 and break targets
SaveAndRestore<CFGBlock*> save_Block(Block), save_Succ(Succ),
save_continue(ContinueTargetBlock),
save_break(BreakTargetBlock);
// Create a new block to contain the (bottom) of the loop body.
Block = NULL;
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 = createBlock();
}
// Finish up the increment (or empty) block if it hasn't been already.
if (Block) {
assert(Block == Succ);
if (!FinishBlock(Block))
return 0;
Block = 0;
}
ContinueTargetBlock = Succ;
// 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.
ContinueTargetBlock->setLoopTarget(F);
// All breaks should go to the code following the loop.
BreakTargetBlock = LoopSuccessor;
// 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 = ContinueTargetBlock; // can happen for "for (...;...;...) ;"
else if (Block && !FinishBlock(BodyBlock))
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);
} else {
// 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::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 (!FinishBlock(Block))
return 0;
LoopSuccessor = Block;
Block = 0;
} else
LoopSuccessor = Succ;
// Build the condition blocks.
CFGBlock* ExitConditionBlock = createBlock(false);
CFGBlock* EntryConditionBlock = ExitConditionBlock;
// 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 necesary. We DON'T add the statement by default to
// the CFG unless it contains control-flow.
EntryConditionBlock = Visit(S->getElement(), AddStmtChoice::NotAlwaysAdd);
if (Block) {
if (!FinishBlock(EntryConditionBlock))
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),
save_continue(ContinueTargetBlock), save_break(BreakTargetBlock);
BreakTargetBlock = LoopSuccessor;
ContinueTargetBlock = EntryConditionBlock;
CFGBlock* BodyBlock = addStmt(S->getBody());
if (!BodyBlock)
BodyBlock = EntryConditionBlock; // can happen for "for (X in Y) ;"
else if (Block) {
if (!FinishBlock(BodyBlock))
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::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 (!FinishBlock(SyncBlock))
return 0;
Block = 0;
}
Succ = SyncBlock;
// Inline the sync expression.
return addStmt(S->getSynchExpr());
}
CFGBlock* CFGBuilder::VisitObjCAtTryStmt(ObjCAtTryStmt* S) {
// FIXME
return NYS();
}
CFGBlock* CFGBuilder::VisitWhileStmt(WhileStmt* W) {
CFGBlock* LoopSuccessor = NULL;
// "while" is a control-flow statement. Thus we stop processing the current
// block.
if (Block) {
if (!FinishBlock(Block))
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(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);
assert(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, AddStmtChoice::AlwaysAdd);
EntryConditionBlock = addStmt(Init);
assert(Block == EntryConditionBlock);
}
}
if (Block) {
if (!FinishBlock(EntryConditionBlock))
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),
save_continue(ContinueTargetBlock),
save_break(BreakTargetBlock);
// 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);
ContinueTargetBlock = Succ;
// All breaks should go to the code following the loop.
BreakTargetBlock = LoopSuccessor;
// NULL out Block to force lazy instantiation of blocks for the body.
Block = NULL;
// Create the body. The returned block is the entry to the loop body.
CFGBlock* BodyBlock = addStmt(W->getBody());
if (!BodyBlock)
BodyBlock = ContinueTargetBlock; // can happen for "while(...) ;"
else if (Block) {
if (!FinishBlock(BodyBlock))
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 (Block && !FinishBlock(Block))
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 (Block && !FinishBlock(Block))
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 (!FinishBlock(Block))
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 (!FinishBlock(EntryConditionBlock))
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),
save_continue(ContinueTargetBlock),
save_break(BreakTargetBlock);
// All continues within this loop should go to the condition block
ContinueTargetBlock = EntryConditionBlock;
// All breaks should go to the code following the loop.
BreakTargetBlock = LoopSuccessor;
// NULL out Block to force lazy instantiation of blocks for the body.
Block = NULL;
// 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 (!FinishBlock(BodyBlock))
return 0;
}
// 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, KnownVal.isFalse() ? NULL : LoopBackBlock);
}
// 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 (Block && !FinishBlock(Block))
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 (ContinueTargetBlock)
AddSuccessor(Block, ContinueTargetBlock);
else
badCFG = true;
return Block;
}
CFGBlock *CFGBuilder::VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E,
AddStmtChoice asc) {
if (asc.alwaysAdd()) {
autoCreateBlock();
AppendStmt(Block, E);
}
// VLA types have expressions that must be evaluated.
if (E->isArgumentType()) {
for (VariableArrayType* VA = FindVA(E->getArgumentType().getTypePtr());
VA != 0; VA = FindVA(VA->getElementType().getTypePtr()))
addStmt(VA->getSizeExpr());
}
return Block;
}
/// VisitStmtExpr - Utility method to handle (nested) statement
/// expressions (a GCC extension).
CFGBlock* CFGBuilder::VisitStmtExpr(StmtExpr *SE, AddStmtChoice asc) {
if (asc.alwaysAdd()) {
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;
if (Block) {
if (!FinishBlock(Block))
return 0;
SwitchSuccessor = Block;
} else SwitchSuccessor = Succ;
// Save the current "switch" context.
SaveAndRestore<CFGBlock*> save_switch(SwitchTerminatedBlock),
save_break(BreakTargetBlock),
save_default(DefaultCaseBlock);
// 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;
BreakTargetBlock = SwitchSuccessor;
// 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;
CFGBlock *BodyBlock = addStmt(Terminator->getBody());
if (Block) {
if (!FinishBlock(BodyBlock))
return 0;
}
// If we have no "default:" case, the default transition is to the code
// following the switch body.
AddSuccessor(SwitchTerminatedBlock, DefaultCaseBlock);
// Add the terminator and condition in the switch block.
SwitchTerminatedBlock->setTerminator(Terminator);
assert(Terminator->getCond() && "switch condition must be non-NULL");
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, AddStmtChoice::AlwaysAdd);
addStmt(Init);
}
}
return Block;
}
CFGBlock* CFGBuilder::VisitCaseStmt(CaseStmt* CS) {
// CaseStmts are essentially labels, so they are the first statement in a
// block.
if (CS->getSubStmt())
addStmt(CS->getSubStmt());
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 (!FinishBlock(CaseBlock))
return 0;
// Add this block to the list of successors for the block with the switch
// statement.
assert(SwitchTerminatedBlock);
AddSuccessor(SwitchTerminatedBlock, CaseBlock);
// 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 = CaseBlock;
return CaseBlock;
}
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 (!FinishBlock(DefaultCaseBlock))
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 (!FinishBlock(Block))
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 = true;
}
Block = NULL;
CFGBlock *CatchBlock = VisitCXXCatchStmt(CS);
if (CatchBlock == 0)
return 0;
// Add this block to the list of successors for the block with the try
// statement.
AddSuccessor(NewTryTerminatedBlock, CatchBlock);
}
if (!HasCatchAll) {
if (PrevTryTerminatedBlock)
AddSuccessor(NewTryTerminatedBlock, PrevTryTerminatedBlock);
else
AddSuccessor(NewTryTerminatedBlock, &cfg->getExit());
}
// The code after the try is the implicit successor.
Succ = TrySuccessor;
// Save the current "try" context.
SaveAndRestore<CFGBlock*> save_try(TryTerminatedBlock);
TryTerminatedBlock = NewTryTerminatedBlock;
assert(Terminator->getTryBlock() && "try must contain a non-NULL body");
Block = NULL;
Block = addStmt(Terminator->getTryBlock());
return Block;
}
CFGBlock* CFGBuilder::VisitCXXCatchStmt(CXXCatchStmt* CS) {
// CXXCatchStmt are treated like labels, so they are the first statement in a
// block.
if (CS->getHandlerBlock())
addStmt(CS->getHandlerBlock());
CFGBlock* CatchBlock = Block;
if (!CatchBlock)
CatchBlock = createBlock();
CatchBlock->setLabel(CS);
if (!FinishBlock(CatchBlock))
return 0;
// We set Block to NULL to allow lazy creation of a new block (if necessary)
Block = NULL;
return CatchBlock;
}
CFGBlock* CFGBuilder::VisitIndirectGotoStmt(IndirectGotoStmt* I) {
// Lazily create the indirect-goto dispatch block if there isn't one already.
CFGBlock* IBlock = cfg->getIndirectGotoBlock();
if (!IBlock) {
IBlock = createBlock(false);
cfg->setIndirectGotoBlock(IBlock);
}
// IndirectGoto is a control-flow statement. Thus we stop processing the
// current block and create a new one.
if (Block && !FinishBlock(Block))
return 0;
Block = createBlock(false);
Block->setTerminator(I);
AddSuccessor(Block, IBlock);
return addStmt(I->getTarget());
}
} // end anonymous namespace
/// createBlock - Constructs and adds a new CFGBlock to the CFG. The block has
/// no successors or predecessors. If this is the first block created in the
/// CFG, it is automatically set to be the Entry and Exit of the CFG.
CFGBlock* CFG::createBlock() {
bool first_block = begin() == end();
// Create the block.
CFGBlock *Mem = getAllocator().Allocate<CFGBlock>();
new (Mem) CFGBlock(NumBlockIDs++, BlkBVC);
Blocks.push_back(Mem, BlkBVC);
// If this is the first block, set it as the Entry and Exit.
if (first_block)
Entry = Exit = &back();
// Return the block.
return &back();
}
/// buildCFG - Constructs a CFG from an AST. Ownership of the returned
/// CFG is returned to the caller.
CFG* CFG::buildCFG(const Decl *D, Stmt* Statement, ASTContext *C,
bool AddEHEdges, bool AddScopes) {
CFGBuilder Builder;
return Builder.buildCFG(D, Statement, C, AddEHEdges, AddScopes);
}
//===----------------------------------------------------------------------===//
// CFG: Queries for BlkExprs.
//===----------------------------------------------------------------------===//
namespace {
typedef llvm::DenseMap<const Stmt*,unsigned> BlkExprMapTy;
}
static void FindSubExprAssignments(Stmt *S,
llvm::SmallPtrSet<Expr*,50>& Set) {
if (!S)
return;
for (Stmt::child_iterator I=S->child_begin(), E=S->child_end(); I!=E; ++I) {
Stmt *child = *I;
if (!child)
continue;
if (BinaryOperator* B = dyn_cast<BinaryOperator>(child))
if (B->isAssignmentOp()) Set.insert(B);
FindSubExprAssignments(child, Set);
}
}
static BlkExprMapTy* PopulateBlkExprMap(CFG& cfg) {
BlkExprMapTy* M = new BlkExprMapTy();
// Look for assignments that are used as subexpressions. These are the only
// assignments that we want to *possibly* register as a block-level
// expression. Basically, if an assignment occurs both in a subexpression and
// at the block-level, it is a block-level expression.
llvm::SmallPtrSet<Expr*,50> SubExprAssignments;
for (CFG::iterator I=cfg.begin(), E=cfg.end(); I != E; ++I)
for (CFGBlock::iterator BI=(*I)->begin(), EI=(*I)->end(); BI != EI; ++BI)
FindSubExprAssignments(*BI, SubExprAssignments);
for (CFG::iterator I=cfg.begin(), E=cfg.end(); I != E; ++I) {
// Iterate over the statements again on identify the Expr* and Stmt* at the
// block-level that are block-level expressions.
for (CFGBlock::iterator BI=(*I)->begin(), EI=(*I)->end(); BI != EI; ++BI)
if (Expr* Exp = dyn_cast<Expr>(*BI)) {
if (BinaryOperator* B = dyn_cast<BinaryOperator>(Exp)) {
// Assignment expressions that are not nested within another
// expression are really "statements" whose value is never used by
// another expression.
if (B->isAssignmentOp() && !SubExprAssignments.count(Exp))
continue;
} else if (const StmtExpr* Terminator = dyn_cast<StmtExpr>(Exp)) {
// Special handling for statement expressions. The last statement in
// the statement expression is also a block-level expr.
const CompoundStmt* C = Terminator->getSubStmt();
if (!C->body_empty()) {
unsigned x = M->size();
(*M)[C->body_back()] = x;
}
}
unsigned x = M->size();
(*M)[Exp] = x;
}
// Look at terminators. The condition is a block-level expression.
Stmt* S = (*I)->getTerminatorCondition();
if (S && M->find(S) == M->end()) {
unsigned x = M->size();
(*M)[S] = x;
}
}
return M;
}
CFG::BlkExprNumTy CFG::getBlkExprNum(const Stmt* S) {
assert(S != NULL);
if (!BlkExprMap) { BlkExprMap = (void*) PopulateBlkExprMap(*this); }
BlkExprMapTy* M = reinterpret_cast<BlkExprMapTy*>(BlkExprMap);
BlkExprMapTy::iterator I = M->find(S);
return (I == M->end()) ? CFG::BlkExprNumTy() : CFG::BlkExprNumTy(I->second);
}
unsigned CFG::getNumBlkExprs() {
if (const BlkExprMapTy* M = reinterpret_cast<const BlkExprMapTy*>(BlkExprMap))
return M->size();
else {
// We assume callers interested in the number of BlkExprs will want
// the map constructed if it doesn't already exist.
BlkExprMap = (void*) PopulateBlkExprMap(*this);
return reinterpret_cast<BlkExprMapTy*>(BlkExprMap)->size();
}
}
//===----------------------------------------------------------------------===//
// Cleanup: CFG dstor.
//===----------------------------------------------------------------------===//
CFG::~CFG() {
delete reinterpret_cast<const BlkExprMapTy*>(BlkExprMap);
}
//===----------------------------------------------------------------------===//
// CFG pretty printing
//===----------------------------------------------------------------------===//
namespace {
class StmtPrinterHelper : public PrinterHelper {
typedef llvm::DenseMap<Stmt*,std::pair<unsigned,unsigned> > StmtMapTy;
StmtMapTy StmtMap;
signed CurrentBlock;
unsigned CurrentStmt;
const LangOptions &LangOpts;
public:
StmtPrinterHelper(const CFG* cfg, const LangOptions &LO)
: CurrentBlock(0), CurrentStmt(0), LangOpts(LO) {
for (CFG::const_iterator I = cfg->begin(), E = cfg->end(); I != E; ++I ) {
unsigned j = 1;
for (CFGBlock::const_iterator BI = (*I)->begin(), BEnd = (*I)->end() ;
BI != BEnd; ++BI, ++j )
StmtMap[*BI] = std::make_pair((*I)->getBlockID(),j);
}
}
virtual ~StmtPrinterHelper() {}
const LangOptions &getLangOpts() const { return LangOpts; }
void setBlockID(signed i) { CurrentBlock = i; }
void setStmtID(unsigned i) { CurrentStmt = i; }
virtual bool handledStmt(Stmt* Terminator, llvm::raw_ostream& OS) {
StmtMapTy::iterator I = StmtMap.find(Terminator);
if (I == StmtMap.end())
return false;
if (CurrentBlock >= 0 && I->second.first == (unsigned) CurrentBlock
&& I->second.second == CurrentStmt) {
return false;
}
OS << "[B" << I->second.first << "." << I->second.second << "]";
return true;
}
};
} // end anonymous namespace
namespace {
class CFGBlockTerminatorPrint
: public StmtVisitor<CFGBlockTerminatorPrint,void> {
llvm::raw_ostream& OS;
StmtPrinterHelper* Helper;
PrintingPolicy Policy;
public:
CFGBlockTerminatorPrint(llvm::raw_ostream& os, StmtPrinterHelper* helper,
const PrintingPolicy &Policy)
: OS(os), Helper(helper), Policy(Policy) {}
void VisitIfStmt(IfStmt* I) {
OS << "if ";
I->getCond()->printPretty(OS,Helper,Policy);
}
// Default case.
void VisitStmt(Stmt* Terminator) {
Terminator->printPretty(OS, Helper, Policy);
}
void VisitForStmt(ForStmt* F) {
OS << "for (" ;
if (F->getInit())
OS << "...";
OS << "; ";
if (Stmt* C = F->getCond())
C->printPretty(OS, Helper, Policy);
OS << "; ";
if (F->getInc())
OS << "...";
OS << ")";
}
void VisitWhileStmt(WhileStmt* W) {
OS << "while " ;
if (Stmt* C = W->getCond())
C->printPretty(OS, Helper, Policy);
}
void VisitDoStmt(DoStmt* D) {
OS << "do ... while ";
if (Stmt* C = D->getCond())
C->printPretty(OS, Helper, Policy);
}
void VisitSwitchStmt(SwitchStmt* Terminator) {
OS << "switch ";
Terminator->getCond()->printPretty(OS, Helper, Policy);
}
void VisitCXXTryStmt(CXXTryStmt* CS) {
OS << "try ...";
}
void VisitConditionalOperator(ConditionalOperator* C) {
C->getCond()->printPretty(OS, Helper, Policy);
OS << " ? ... : ...";
}
void VisitChooseExpr(ChooseExpr* C) {
OS << "__builtin_choose_expr( ";
C->getCond()->printPretty(OS, Helper, Policy);
OS << " )";
}
void VisitIndirectGotoStmt(IndirectGotoStmt* I) {
OS << "goto *";
I->getTarget()->printPretty(OS, Helper, Policy);
}
void VisitBinaryOperator(BinaryOperator* B) {
if (!B->isLogicalOp()) {
VisitExpr(B);
return;
}
B->getLHS()->printPretty(OS, Helper, Policy);
switch (B->getOpcode()) {
case BinaryOperator::LOr:
OS << " || ...";
return;
case BinaryOperator::LAnd:
OS << " && ...";
return;
default:
assert(false && "Invalid logical operator.");
}
}
void VisitExpr(Expr* E) {
E->printPretty(OS, Helper, Policy);
}
};
} // end anonymous namespace
static void print_stmt(llvm::raw_ostream &OS, StmtPrinterHelper* Helper,
const CFGElement &E) {
Stmt *Terminator = E;
if (E.asStartScope()) {
OS << "start scope\n";
return;
}
if (E.asEndScope()) {
OS << "end scope\n";
return;
}
if (Helper) {
// special printing for statement-expressions.
if (StmtExpr* SE = dyn_cast<StmtExpr>(Terminator)) {
CompoundStmt* Sub = SE->getSubStmt();
if (Sub->child_begin() != Sub->child_end()) {
OS << "({ ... ; ";
Helper->handledStmt(*SE->getSubStmt()->body_rbegin(),OS);
OS << " })\n";
return;
}
}
// special printing for comma expressions.
if (BinaryOperator* B = dyn_cast<BinaryOperator>(Terminator)) {
if (B->getOpcode() == BinaryOperator::Comma) {
OS << "... , ";
Helper->handledStmt(B->getRHS(),OS);
OS << '\n';
return;
}
}
}
Terminator->printPretty(OS, Helper, PrintingPolicy(Helper->getLangOpts()));
// Expressions need a newline.
if (isa<Expr>(Terminator)) OS << '\n';
}
static void print_block(llvm::raw_ostream& OS, const CFG* cfg,
const CFGBlock& B,
StmtPrinterHelper* Helper, bool print_edges) {
if (Helper) Helper->setBlockID(B.getBlockID());
// Print the header.
OS << "\n [ B" << B.getBlockID();
if (&B == &cfg->getEntry())
OS << " (ENTRY) ]\n";
else if (&B == &cfg->getExit())
OS << " (EXIT) ]\n";
else if (&B == cfg->getIndirectGotoBlock())
OS << " (INDIRECT GOTO DISPATCH) ]\n";
else
OS << " ]\n";
// Print the label of this block.
if (Stmt* Label = const_cast<Stmt*>(B.getLabel())) {
if (print_edges)
OS << " ";
if (LabelStmt* L = dyn_cast<LabelStmt>(Label))
OS << L->getName();
else if (CaseStmt* C = dyn_cast<CaseStmt>(Label)) {
OS << "case ";
C->getLHS()->printPretty(OS, Helper,
PrintingPolicy(Helper->getLangOpts()));
if (C->getRHS()) {
OS << " ... ";
C->getRHS()->printPretty(OS, Helper,
PrintingPolicy(Helper->getLangOpts()));
}
} else if (isa<DefaultStmt>(Label))
OS << "default";
else if (CXXCatchStmt *CS = dyn_cast<CXXCatchStmt>(Label)) {
OS << "catch (";
if (CS->getExceptionDecl())
CS->getExceptionDecl()->print(OS, PrintingPolicy(Helper->getLangOpts()),
0);
else
OS << "...";
OS << ")";
} else
assert(false && "Invalid label statement in CFGBlock.");
OS << ":\n";
}
// Iterate through the statements in the block and print them.
unsigned j = 1;
for (CFGBlock::const_iterator I = B.begin(), E = B.end() ;
I != E ; ++I, ++j ) {
// Print the statement # in the basic block and the statement itself.
if (print_edges)
OS << " ";
OS << llvm::format("%3d", j) << ": ";
if (Helper)
Helper->setStmtID(j);
print_stmt(OS,Helper,*I);
}
// Print the terminator of this block.
if (B.getTerminator()) {
if (print_edges)
OS << " ";
OS << " T: ";
if (Helper) Helper->setBlockID(-1);
CFGBlockTerminatorPrint TPrinter(OS, Helper,
PrintingPolicy(Helper->getLangOpts()));
TPrinter.Visit(const_cast<Stmt*>(B.getTerminator()));
OS << '\n';
}
if (print_edges) {
// Print the predecessors of this block.
OS << " Predecessors (" << B.pred_size() << "):";
unsigned i = 0;
for (CFGBlock::const_pred_iterator I = B.pred_begin(), E = B.pred_end();
I != E; ++I, ++i) {
if (i == 8 || (i-8) == 0)
OS << "\n ";
OS << " B" << (*I)->getBlockID();
}
OS << '\n';
// Print the successors of this block.
OS << " Successors (" << B.succ_size() << "):";
i = 0;
for (CFGBlock::const_succ_iterator I = B.succ_begin(), E = B.succ_end();
I != E; ++I, ++i) {
if (i == 8 || (i-8) % 10 == 0)
OS << "\n ";
if (*I)
OS << " B" << (*I)->getBlockID();
else
OS << " NULL";
}
OS << '\n';
}
}
/// dump - A simple pretty printer of a CFG that outputs to stderr.
void CFG::dump(const LangOptions &LO) const { print(llvm::errs(), LO); }
/// print - A simple pretty printer of a CFG that outputs to an ostream.
void CFG::print(llvm::raw_ostream &OS, const LangOptions &LO) const {
StmtPrinterHelper Helper(this, LO);
// Print the entry block.
print_block(OS, this, getEntry(), &Helper, true);
// Iterate through the CFGBlocks and print them one by one.
for (const_iterator I = Blocks.begin(), E = Blocks.end() ; I != E ; ++I) {
// Skip the entry block, because we already printed it.
if (&(**I) == &getEntry() || &(**I) == &getExit())
continue;
print_block(OS, this, **I, &Helper, true);
}
// Print the exit block.
print_block(OS, this, getExit(), &Helper, true);
OS.flush();
}
/// dump - A simply pretty printer of a CFGBlock that outputs to stderr.
void CFGBlock::dump(const CFG* cfg, const LangOptions &LO) const {
print(llvm::errs(), cfg, LO);
}
/// print - A simple pretty printer of a CFGBlock that outputs to an ostream.
/// Generally this will only be called from CFG::print.
void CFGBlock::print(llvm::raw_ostream& OS, const CFG* cfg,
const LangOptions &LO) const {
StmtPrinterHelper Helper(cfg, LO);
print_block(OS, cfg, *this, &Helper, true);
}
/// printTerminator - A simple pretty printer of the terminator of a CFGBlock.
void CFGBlock::printTerminator(llvm::raw_ostream &OS,
const LangOptions &LO) const {
CFGBlockTerminatorPrint TPrinter(OS, NULL, PrintingPolicy(LO));
TPrinter.Visit(const_cast<Stmt*>(getTerminator()));
}
Stmt* CFGBlock::getTerminatorCondition() {
if (!Terminator)
return NULL;
Expr* E = NULL;
switch (Terminator->getStmtClass()) {
default:
break;
case Stmt::ForStmtClass:
E = cast<ForStmt>(Terminator)->getCond();
break;
case Stmt::WhileStmtClass:
E = cast<WhileStmt>(Terminator)->getCond();
break;
case Stmt::DoStmtClass:
E = cast<DoStmt>(Terminator)->getCond();
break;
case Stmt::IfStmtClass:
E = cast<IfStmt>(Terminator)->getCond();
break;
case Stmt::ChooseExprClass:
E = cast<ChooseExpr>(Terminator)->getCond();
break;
case Stmt::IndirectGotoStmtClass:
E = cast<IndirectGotoStmt>(Terminator)->getTarget();
break;
case Stmt::SwitchStmtClass:
E = cast<SwitchStmt>(Terminator)->getCond();
break;
case Stmt::ConditionalOperatorClass:
E = cast<ConditionalOperator>(Terminator)->getCond();
break;
case Stmt::BinaryOperatorClass: // '&&' and '||'
E = cast<BinaryOperator>(Terminator)->getLHS();
break;
case Stmt::ObjCForCollectionStmtClass:
return Terminator;
}
return E ? E->IgnoreParens() : NULL;
}
bool CFGBlock::hasBinaryBranchTerminator() const {
if (!Terminator)
return false;
Expr* E = NULL;
switch (Terminator->getStmtClass()) {
default:
return false;
case Stmt::ForStmtClass:
case Stmt::WhileStmtClass:
case Stmt::DoStmtClass:
case Stmt::IfStmtClass:
case Stmt::ChooseExprClass:
case Stmt::ConditionalOperatorClass:
case Stmt::BinaryOperatorClass:
return true;
}
return E ? E->IgnoreParens() : NULL;
}
//===----------------------------------------------------------------------===//
// CFG Graphviz Visualization
//===----------------------------------------------------------------------===//
#ifndef NDEBUG
static StmtPrinterHelper* GraphHelper;
#endif
void CFG::viewCFG(const LangOptions &LO) const {
#ifndef NDEBUG
StmtPrinterHelper H(this, LO);
GraphHelper = &H;
llvm::ViewGraph(this,"CFG");
GraphHelper = NULL;
#endif
}
namespace llvm {
template<>
struct DOTGraphTraits<const CFG*> : public DefaultDOTGraphTraits {
DOTGraphTraits (bool isSimple=false) : DefaultDOTGraphTraits(isSimple) {}
static std::string getNodeLabel(const CFGBlock* Node, const CFG* Graph) {
#ifndef NDEBUG
std::string OutSStr;
llvm::raw_string_ostream Out(OutSStr);
print_block(Out,Graph, *Node, GraphHelper, false);
std::string& OutStr = Out.str();
if (OutStr[0] == '\n') OutStr.erase(OutStr.begin());
// Process string output to make it nicer...
for (unsigned i = 0; i != OutStr.length(); ++i)
if (OutStr[i] == '\n') { // Left justify
OutStr[i] = '\\';
OutStr.insert(OutStr.begin()+i+1, 'l');
}
return OutStr;
#else
return "";
#endif
}
};
} // end namespace llvm