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Diffstat (limited to 'clang/lib/AST/CFG.cpp')
| -rw-r--r-- | clang/lib/AST/CFG.cpp | 1509 |
1 files changed, 1509 insertions, 0 deletions
diff --git a/clang/lib/AST/CFG.cpp b/clang/lib/AST/CFG.cpp new file mode 100644 index 00000000000..e2aba6b3ff3 --- /dev/null +++ b/clang/lib/AST/CFG.cpp @@ -0,0 +1,1509 @@ +//===--- 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/AST/CFG.h" +#include "clang/AST/Expr.h" +#include "clang/AST/StmtVisitor.h" +#include "clang/AST/PrettyPrinter.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/Support/GraphWriter.h" +#include "llvm/Support/Streams.h" +#include "llvm/Support/Compiler.h" +#include <set> +#include <iomanip> +#include <algorithm> +#include <sstream> +#include <iostream> + +using namespace clang; + +namespace { + +// SaveAndRestore - A utility class that uses RIIA to save and restore +// the value of a variable. +template<typename T> +struct VISIBILITY_HIDDEN SaveAndRestore { + SaveAndRestore(T& x) : X(x), old_value(x) {} + ~SaveAndRestore() { X = old_value; } + T get() { return old_value; } + + T& X; + T old_value; +}; + +/// CFGBuilder - This class is 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 VISIBILITY_HIDDEN CFGBuilder : public StmtVisitor<CFGBuilder,CFGBlock*> { + CFG* cfg; + CFGBlock* Block; + CFGBlock* Succ; + CFGBlock* ContinueTargetBlock; + CFGBlock* BreakTargetBlock; + CFGBlock* SwitchTerminatedBlock; + CFGBlock* DefaultCaseBlock; + + // 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(NULL), Block(NULL), Succ(NULL), + ContinueTargetBlock(NULL), BreakTargetBlock(NULL), + SwitchTerminatedBlock(NULL), DefaultCaseBlock(NULL) { + // Create an empty CFG. + cfg = new CFG(); + } + + ~CFGBuilder() { delete cfg; } + + // buildCFG - Used by external clients to construct the CFG. + CFG* buildCFG(Stmt* Statement); + + // Visitors to walk an AST and construct the CFG. Called by + // buildCFG. Do not call directly! + + CFGBlock* VisitStmt(Stmt* Statement); + CFGBlock* VisitNullStmt(NullStmt* Statement); + CFGBlock* VisitCompoundStmt(CompoundStmt* C); + CFGBlock* VisitIfStmt(IfStmt* I); + CFGBlock* VisitReturnStmt(ReturnStmt* R); + CFGBlock* VisitLabelStmt(LabelStmt* L); + CFGBlock* VisitGotoStmt(GotoStmt* G); + CFGBlock* VisitForStmt(ForStmt* F); + CFGBlock* VisitWhileStmt(WhileStmt* W); + CFGBlock* VisitDoStmt(DoStmt* D); + CFGBlock* VisitContinueStmt(ContinueStmt* C); + CFGBlock* VisitBreakStmt(BreakStmt* B); + CFGBlock* VisitSwitchStmt(SwitchStmt* S); + CFGBlock* VisitCaseStmt(CaseStmt* S); + CFGBlock* VisitDefaultStmt(DefaultStmt* D); + CFGBlock* VisitIndirectGotoStmt(IndirectGotoStmt* I); + + // FIXME: Add support for ObjC-specific control-flow structures. + + CFGBlock* VisitObjCForCollectionStmt(ObjCForCollectionStmt* S) { + badCFG = true; + return Block; + } + + CFGBlock* VisitObjCAtTryStmt(ObjCAtTryStmt* S) { + badCFG = true; + return Block; + } + +private: + CFGBlock* createBlock(bool add_successor = true); + CFGBlock* addStmt(Stmt* S); + CFGBlock* WalkAST(Stmt* S, bool AlwaysAddStmt); + CFGBlock* WalkAST_VisitChildren(Stmt* S); + CFGBlock* WalkAST_VisitDeclSubExprs(StmtIterator& I); + CFGBlock* WalkAST_VisitStmtExpr(StmtExpr* S); + void FinishBlock(CFGBlock* B); + + bool badCFG; +}; + +/// 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(Stmt* Statement) { + assert (cfg); + if (!Statement) return NULL; + + 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 = Visit(Statement); + 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; + + B->addSuccessor(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; + + B->addSuccessor(LI->second); + } + + Succ = B; + } + + // Create an empty entry block that has no predecessors. + cfg->setEntry(createBlock()); + + if (badCFG) { + delete cfg; + cfg = NULL; + return NULL; + } + + // NULL out cfg so that repeated calls to the builder will fail and that + // the ownership of the constructed CFG is passed to the caller. + CFG* t = cfg; + cfg = NULL; + return t; +} + +/// 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) B->addSuccessor(Succ); + return B; +} + +/// FinishBlock - When the last statement has been added to the block, +/// we must reverse the statements because they have been inserted +/// in reverse order. +void CFGBuilder::FinishBlock(CFGBlock* B) { + assert (B); + B->reverseStmts(); +} + +/// addStmt - Used to add statements/expressions to the current CFGBlock +/// "Block". This method calls WalkAST on the passed statement to see if it +/// contains any short-circuit expressions. If so, it recursively creates +/// the necessary blocks for such expressions. It returns the "topmost" block +/// of the created blocks, or the original value of "Block" when this method +/// was called if no additional blocks are created. +CFGBlock* CFGBuilder::addStmt(Stmt* S) { + if (!Block) Block = createBlock(); + return WalkAST(S,true); +} + +/// WalkAST - Used by addStmt to 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::WalkAST(Stmt* S, bool AlwaysAddStmt = false) { + switch (S->getStmtClass()) { + case Stmt::ConditionalOperatorClass: { + ConditionalOperator* C = cast<ConditionalOperator>(S); + + // Create the confluence block that will "merge" the results + // of the ternary expression. + CFGBlock* ConfluenceBlock = (Block) ? Block : createBlock(); + ConfluenceBlock->appendStmt(C); + FinishBlock(ConfluenceBlock); + + // 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 = Visit(C->getLHS()); + FinishBlock(LHSBlock); + Block = NULL; + } + + // Create the block for the RHS expression. + Succ = ConfluenceBlock; + CFGBlock* RHSBlock = Visit(C->getRHS()); + FinishBlock(RHSBlock); + + // Create the block that will contain the condition. + Block = createBlock(false); + + if (LHSBlock) + Block->addSuccessor(LHSBlock); + 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. + Block->addSuccessor(ConfluenceBlock); + assert (ConfluenceBlock->pred_size() == 2); + std::reverse(ConfluenceBlock->pred_begin(), + ConfluenceBlock->pred_end()); + } + + Block->addSuccessor(RHSBlock); + + Block->setTerminator(C); + return addStmt(C->getCond()); + } + + case Stmt::ChooseExprClass: { + ChooseExpr* C = cast<ChooseExpr>(S); + + CFGBlock* ConfluenceBlock = (Block) ? Block : createBlock(); + ConfluenceBlock->appendStmt(C); + FinishBlock(ConfluenceBlock); + + Succ = ConfluenceBlock; + Block = NULL; + CFGBlock* LHSBlock = Visit(C->getLHS()); + FinishBlock(LHSBlock); + + Succ = ConfluenceBlock; + Block = NULL; + CFGBlock* RHSBlock = Visit(C->getRHS()); + FinishBlock(RHSBlock); + + Block = createBlock(false); + Block->addSuccessor(LHSBlock); + Block->addSuccessor(RHSBlock); + Block->setTerminator(C); + return addStmt(C->getCond()); + } + + case Stmt::DeclStmtClass: { + ScopedDecl* D = cast<DeclStmt>(S)->getDecl(); + Block->appendStmt(S); + + StmtIterator I(D); + return WalkAST_VisitDeclSubExprs(I); + } + + case Stmt::AddrLabelExprClass: { + AddrLabelExpr* A = cast<AddrLabelExpr>(S); + AddressTakenLabels.insert(A->getLabel()); + + if (AlwaysAddStmt) Block->appendStmt(S); + return Block; + } + + case Stmt::StmtExprClass: + return WalkAST_VisitStmtExpr(cast<StmtExpr>(S)); + + case Stmt::UnaryOperatorClass: { + UnaryOperator* U = cast<UnaryOperator>(S); + + // sizeof(expressions). For such expressions, + // the subexpression is not really evaluated, so + // we don't care about control-flow within the sizeof. + if (U->getOpcode() == UnaryOperator::SizeOf) { + Block->appendStmt(S); + return Block; + } + + break; + } + + case Stmt::BinaryOperatorClass: { + BinaryOperator* B = cast<BinaryOperator>(S); + + if (B->isLogicalOp()) { // && or || + CFGBlock* ConfluenceBlock = (Block) ? Block : createBlock(); + ConfluenceBlock->appendStmt(B); + FinishBlock(ConfluenceBlock); + + // 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 = Visit(B->getRHS()); + + // Now link the LHSBlock with RHSBlock. + if (B->getOpcode() == BinaryOperator::LOr) { + LHSBlock->addSuccessor(ConfluenceBlock); + LHSBlock->addSuccessor(RHSBlock); + } + else { + assert (B->getOpcode() == BinaryOperator::LAnd); + LHSBlock->addSuccessor(RHSBlock); + LHSBlock->addSuccessor(ConfluenceBlock); + } + + // Generate the blocks for evaluating the LHS. + Block = LHSBlock; + return addStmt(B->getLHS()); + } + else if (B->getOpcode() == BinaryOperator::Comma) { // , + Block->appendStmt(B); + addStmt(B->getRHS()); + return addStmt(B->getLHS()); + } + + break; + } + + case Stmt::ParenExprClass: + return WalkAST(cast<ParenExpr>(S)->getSubExpr(), AlwaysAddStmt); + + default: + break; + }; + + if (AlwaysAddStmt) Block->appendStmt(S); + return WalkAST_VisitChildren(S); +} + +/// WalkAST_VisitDeclSubExprs - Utility method to handle Decls contained in +/// DeclStmts. Because the initialization code (and sometimes the +/// the type declarations) for DeclStmts can contain arbitrary expressions, +/// we must linearize declarations to handle arbitrary control-flow induced by +/// those expressions. +CFGBlock* CFGBuilder::WalkAST_VisitDeclSubExprs(StmtIterator& I) { + if (I == StmtIterator()) + return Block; + + Stmt* S = *I; + ++I; + WalkAST_VisitDeclSubExprs(I); + + // Optimization: Don't create separate block-level statements for literals. + + switch (S->getStmtClass()) { + case Stmt::IntegerLiteralClass: + case Stmt::CharacterLiteralClass: + case Stmt::StringLiteralClass: + break; + + // All other cases. + + default: + Block = addStmt(S); + } + + return Block; +} + +/// WalkAST_VisitChildren - Utility method to call WalkAST on the +/// children of a Stmt. +CFGBlock* CFGBuilder::WalkAST_VisitChildren(Stmt* S) { + CFGBlock* B = Block; + for (Stmt::child_iterator I = S->child_begin(), E = S->child_end() ; + I != E; ++I) + if (*I) B = WalkAST(*I); + + return B; +} + +/// WalkAST_VisitStmtExpr - Utility method to handle (nested) statement +/// expressions (a GCC extension). +CFGBlock* CFGBuilder::WalkAST_VisitStmtExpr(StmtExpr* S) { + Block->appendStmt(S); + return VisitCompoundStmt(S->getSubStmt()); +} + +/// VisitStmt - Handle statements with no branching control flow. +CFGBlock* CFGBuilder::VisitStmt(Stmt* Statement) { + // We cannot assume that we are in the middle of a basic block, since + // the CFG might only be constructed for this single statement. If + // we have no current basic block, just create one lazily. + if (!Block) Block = createBlock(); + + // Simply add the statement to the current block. We actually + // insert statements in reverse order; this order is reversed later + // when processing the containing element in the AST. + addStmt(Statement); + + return Block; +} + +CFGBlock* CFGBuilder::VisitNullStmt(NullStmt* Statement) { + return Block; +} + +CFGBlock* CFGBuilder::VisitCompoundStmt(CompoundStmt* C) { + + for (CompoundStmt::reverse_body_iterator I=C->body_rbegin(), E=C->body_rend(); + I != E; ++I ) { + Visit(*I); + } + + 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 and reverse its statements. 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; + FinishBlock(Block); + } + + // Process the false branch. NULL out Block so that the recursive + // call to Visit will create a new basic block. + // Null out Block so that all successor + 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 = Visit(Else); + + if (!ElseBlock) // Can occur when the Else body has all NullStmts. + ElseBlock = sv.get(); + else if (Block) + FinishBlock(ElseBlock); + } + + // Process the true branch. NULL out Block so that the recursive + // call to Visit will create a new basic block. + // Null out Block so that all successor + CFGBlock* ThenBlock; + { + Stmt* Then = I->getThen(); + assert (Then); + SaveAndRestore<CFGBlock*> sv(Succ); + Block = NULL; + ThenBlock = Visit(Then); + + if (!ThenBlock) // Can occur when the Then body has all NullStmts. + ThenBlock = sv.get(); + else if (Block) + FinishBlock(ThenBlock); + } + + // 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); + + // Now add the successors. + Block->addSuccessor(ThenBlock); + Block->addSuccessor(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". + return addStmt(I->getCond()->IgnoreParens()); +} + + +CFGBlock* CFGBuilder::VisitReturnStmt(ReturnStmt* R) { + // If we were in the middle of a block we stop processing that block + // and reverse its statements. + // + // 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. + Block->addSuccessor(&cfg->getExit()); + + // Add the return statement to the block. This may create new blocks + // if R contains control-flow (short-circuit operations). + return addStmt(R); +} + +CFGBlock* CFGBuilder::VisitLabelStmt(LabelStmt* L) { + // Get the block of the labeled statement. Add it to our map. + Visit(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); + FinishBlock(LabelBlock); + + // 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 + Block->addSuccessor(I->second); + + return Block; +} + +CFGBlock* CFGBuilder::VisitForStmt(ForStmt* F) { + // "for" is a control-flow statement. Thus we stop processing the + // current block. + + CFGBlock* LoopSuccessor = NULL; + + if (Block) { + FinishBlock(Block); + 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); + if (Block) FinishBlock(EntryConditionBlock); + } + + // The condition block is the implicit successor for the loop body as + // well as any code above the loop. + Succ = EntryConditionBlock; + + // 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); + + // 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; + + // Create a new block to contain the (bottom) of the loop body. + Block = NULL; + + // If we have increment code, insert it at the end of the body block. + if (Stmt* I = F->getInc()) Block = addStmt(I); + + // Now populate the body block, and in the process create new blocks + // as we walk the body of the loop. + CFGBlock* BodyBlock = Visit(F->getBody()); + + if (!BodyBlock) + BodyBlock = EntryConditionBlock; // can happen for "for (...;...; ) ;" + else if (Block) + FinishBlock(BodyBlock); + + // This new body block is a successor to our "exit" condition block. + ExitConditionBlock->addSuccessor(BodyBlock); + } + + // Link up the condition block with the code that follows the loop. + // (the false branch). + ExitConditionBlock->addSuccessor(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::VisitWhileStmt(WhileStmt* W) { + // "while" is a control-flow statement. Thus we stop processing the + // current block. + + CFGBlock* LoopSuccessor = NULL; + + if (Block) { + FinishBlock(Block); + 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 (Block) FinishBlock(EntryConditionBlock); + } + + // The condition block is the implicit successor for the loop body as + // well as any code above the loop. + Succ = EntryConditionBlock; + + // 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); + + // 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. + CFGBlock* BodyBlock = Visit(W->getBody()); + + if (!BodyBlock) + BodyBlock = EntryConditionBlock; // can happen for "while(...) ;" + else if (Block) + FinishBlock(BodyBlock); + + // Add the loop body entry as a successor to the condition. + ExitConditionBlock->addSuccessor(BodyBlock); + } + + // Link up the condition block with the code that follows the loop. + // (the false branch). + ExitConditionBlock->addSuccessor(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::VisitDoStmt(DoStmt* D) { + // "do...while" is a control-flow statement. Thus we stop processing the + // current block. + + CFGBlock* LoopSuccessor = NULL; + + if (Block) { + FinishBlock(Block); + 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) FinishBlock(EntryConditionBlock); + } + + // The condition block is the implicit successor for the loop body. + Succ = EntryConditionBlock; + + // 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 = Visit(D->getBody()); + + if (!BodyBlock) + BodyBlock = EntryConditionBlock; // can happen for "do ; while(...)" + else if (Block) + FinishBlock(BodyBlock); + + // Add the loop body entry as a successor to the condition. + ExitConditionBlock->addSuccessor(BodyBlock); + } + + // Link up the condition block with the code that follows the loop. + // (the false branch). + ExitConditionBlock->addSuccessor(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); + + // 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. Handle this by not registering a successor. + if (ContinueTargetBlock) Block->addSuccessor(ContinueTargetBlock); + + return Block; +} + +CFGBlock* CFGBuilder::VisitBreakStmt(BreakStmt* B) { + // "break" is a control-flow statement. Thus we stop processing the + // current block. + if (Block) FinishBlock(Block); + + // Now create a new block that ends with the continue statement. + Block = createBlock(false); + Block->setTerminator(B); + + // If there is no target for the break, then we are looking at an + // incomplete AST. Handle this by not registering a successor. + if (BreakTargetBlock) Block->addSuccessor(BreakTargetBlock); + + return Block; +} + +CFGBlock* CFGBuilder::VisitSwitchStmt(SwitchStmt* S) { + // "switch" is a control-flow statement. Thus we stop processing the + // current block. + CFGBlock* SwitchSuccessor = NULL; + + if (Block) { + FinishBlock(Block); + 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 (S->getBody() && "switch must contain a non-NULL body"); + Block = NULL; + CFGBlock *BodyBlock = Visit(S->getBody()); + if (Block) FinishBlock(BodyBlock); + + // If we have no "default:" case, the default transition is to the + // code following the switch body. + SwitchTerminatedBlock->addSuccessor(DefaultCaseBlock); + + // Add the terminator and condition in the switch block. + SwitchTerminatedBlock->setTerminator(S); + assert (S->getCond() && "switch condition must be non-NULL"); + Block = SwitchTerminatedBlock; + + return addStmt(S->getCond()); +} + +CFGBlock* CFGBuilder::VisitCaseStmt(CaseStmt* S) { + // CaseStmts are essentially labels, so they are the + // first statement in a block. + + if (S->getSubStmt()) Visit(S->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(S); + FinishBlock(CaseBlock); + + // Add this block to the list of successors for the block with the + // switch statement. + assert (SwitchTerminatedBlock); + SwitchTerminatedBlock->addSuccessor(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* S) { + if (S->getSubStmt()) Visit(S->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(S); + FinishBlock(DefaultCaseBlock); + + // 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::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); + Block = createBlock(false); + Block->setTerminator(I); + Block->addSuccessor(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. + Blocks.push_front(CFGBlock(NumBlockIDs++)); + + // If this is the first block, set it as the Entry and Exit. + if (first_block) Entry = Exit = &front(); + + // Return the block. + return &front(); +} + +/// buildCFG - Constructs a CFG from an AST. Ownership of the returned +/// CFG is returned to the caller. +CFG* CFG::buildCFG(Stmt* Statement) { + CFGBuilder Builder; + return Builder.buildCFG(Statement); +} + +/// reverseStmts - Reverses the orders of statements within a CFGBlock. +void CFGBlock::reverseStmts() { std::reverse(Stmts.begin(),Stmts.end()); } + +//===----------------------------------------------------------------------===// +// 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) { + if (!*I) continue; + + if (BinaryOperator* B = dyn_cast<BinaryOperator>(*I)) + if (B->isAssignmentOp()) Set.insert(B); + + FindSubExprAssignments(*I, 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 register as 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); + + // Iterate over the statements again on identify the Expr* and Stmt* at + // the block-level that are block-level expressions. + for (CFG::iterator I=cfg.begin(), E=cfg.end(); I != E; ++I) + for (CFGBlock::iterator BI=I->begin(), EI=I->end(); BI != EI; ++BI) + if (Expr* E = dyn_cast<Expr>(*BI)) { + + if (BinaryOperator* B = dyn_cast<BinaryOperator>(E)) { + // 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(E)) + continue; + } + else if (const StmtExpr* S = dyn_cast<StmtExpr>(E)) { + // Special handling for statement expressions. The last statement + // in the statement expression is also a block-level expr. + const CompoundStmt* C = S->getSubStmt(); + if (!C->body_empty()) { + unsigned x = M->size(); + (*M)[C->body_back()] = x; + } + } + + unsigned x = M->size(); + (*M)[E] = 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); + + if (I == M->end()) return CFG::BlkExprNumTy(); + else return 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(); + } +} + +typedef std::set<std::pair<CFGBlock*,CFGBlock*> > BlkEdgeSetTy; + +const std::pair<CFGBlock*,CFGBlock*>* +CFG::getBlockEdgeImpl(const CFGBlock* B1, const CFGBlock* B2) { + + BlkEdgeSetTy*& p = reinterpret_cast<BlkEdgeSetTy*&>(BlkEdgeSet); + if (!p) p = new BlkEdgeSetTy(); + + return &*(p->insert(std::make_pair(const_cast<CFGBlock*>(B1), + const_cast<CFGBlock*>(B2))).first); +} + +CFG::~CFG() { + delete reinterpret_cast<const BlkExprMapTy*>(BlkExprMap); + delete reinterpret_cast<BlkEdgeSetTy*>(BlkEdgeSet); +} + +//===----------------------------------------------------------------------===// +// CFG pretty printing +//===----------------------------------------------------------------------===// + +namespace { + +class VISIBILITY_HIDDEN StmtPrinterHelper : public PrinterHelper { + + typedef llvm::DenseMap<Stmt*,std::pair<unsigned,unsigned> > StmtMapTy; + StmtMapTy StmtMap; + signed CurrentBlock; + unsigned CurrentStmt; + +public: + + StmtPrinterHelper(const CFG* cfg) : CurrentBlock(0), CurrentStmt(0) { + 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() {} + + void setBlockID(signed i) { CurrentBlock = i; } + void setStmtID(unsigned i) { CurrentStmt = i; } + + virtual bool handledStmt(Stmt* S, std::ostream& OS) { + + StmtMapTy::iterator I = StmtMap.find(S); + + 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; + } +}; + +class VISIBILITY_HIDDEN CFGBlockTerminatorPrint + : public StmtVisitor<CFGBlockTerminatorPrint,void> { + + std::ostream& OS; + StmtPrinterHelper* Helper; +public: + CFGBlockTerminatorPrint(std::ostream& os, StmtPrinterHelper* helper) + : OS(os), Helper(helper) {} + + void VisitIfStmt(IfStmt* I) { + OS << "if "; + I->getCond()->printPretty(OS,Helper); + } + + // Default case. + void VisitStmt(Stmt* S) { S->printPretty(OS); } + + void VisitForStmt(ForStmt* F) { + OS << "for (" ; + if (F->getInit()) OS << "..."; + OS << "; "; + if (Stmt* C = F->getCond()) C->printPretty(OS,Helper); + OS << "; "; + if (F->getInc()) OS << "..."; + OS << ")"; + } + + void VisitWhileStmt(WhileStmt* W) { + OS << "while " ; + if (Stmt* C = W->getCond()) C->printPretty(OS,Helper); + } + + void VisitDoStmt(DoStmt* D) { + OS << "do ... while "; + if (Stmt* C = D->getCond()) C->printPretty(OS,Helper); + } + + void VisitSwitchStmt(SwitchStmt* S) { + OS << "switch "; + S->getCond()->printPretty(OS,Helper); + } + + void VisitConditionalOperator(ConditionalOperator* C) { + C->getCond()->printPretty(OS,Helper); + OS << " ? ... : ..."; + } + + void VisitChooseExpr(ChooseExpr* C) { + OS << "__builtin_choose_expr( "; + C->getCond()->printPretty(OS,Helper); + OS << " )"; + } + + void VisitIndirectGotoStmt(IndirectGotoStmt* I) { + OS << "goto *"; + I->getTarget()->printPretty(OS,Helper); + } + + void VisitBinaryOperator(BinaryOperator* B) { + if (!B->isLogicalOp()) { + VisitExpr(B); + return; + } + + B->getLHS()->printPretty(OS,Helper); + + 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); + } +}; + + +void print_stmt(std::ostream&OS, StmtPrinterHelper* Helper, Stmt* S) { + if (Helper) { + // special printing for statement-expressions. + if (StmtExpr* SE = dyn_cast<StmtExpr>(S)) { + 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>(S)) { + if (B->getOpcode() == BinaryOperator::Comma) { + OS << "... , "; + Helper->handledStmt(B->getRHS(),OS); + OS << '\n'; + return; + } + } + } + + S->printPretty(OS, Helper); + + // Expressions need a newline. + if (isa<Expr>(S)) OS << '\n'; +} + +void print_block(std::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* S = const_cast<Stmt*>(B.getLabel())) { + + if (print_edges) + OS << " "; + + if (LabelStmt* L = dyn_cast<LabelStmt>(S)) + OS << L->getName(); + else if (CaseStmt* C = dyn_cast<CaseStmt>(S)) { + OS << "case "; + C->getLHS()->printPretty(OS); + if (C->getRHS()) { + OS << " ... "; + C->getRHS()->printPretty(OS); + } + } + else if (isa<DefaultStmt>(S)) + OS << "default"; + 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 << std::setw(3) << 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); + 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 "; + + OS << " B" << (*I)->getBlockID(); + } + + OS << '\n'; + } +} + +} // end anonymous namespace + +/// dump - A simple pretty printer of a CFG that outputs to stderr. +void CFG::dump() const { print(*llvm::cerr.stream()); } + +/// print - A simple pretty printer of a CFG that outputs to an ostream. +void CFG::print(std::ostream& OS) const { + + StmtPrinterHelper Helper(this); + + // 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); +} + +/// dump - A simply pretty printer of a CFGBlock that outputs to stderr. +void CFGBlock::dump(const CFG* cfg) const { print(*llvm::cerr.stream(), cfg); } + +/// 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(std::ostream& OS, const CFG* cfg) const { + StmtPrinterHelper Helper(cfg); + print_block(OS, cfg, *this, &Helper, true); +} + +/// printTerminator - A simple pretty printer of the terminator of a CFGBlock. +void CFGBlock::printTerminator(std::ostream& OS) const { + CFGBlockTerminatorPrint TPrinter(OS,NULL); + TPrinter.Visit(const_cast<Stmt*>(getTerminator())); +} + + +//===----------------------------------------------------------------------===// +// CFG Graphviz Visualization +//===----------------------------------------------------------------------===// + + +#ifndef NDEBUG +static StmtPrinterHelper* GraphHelper; +#endif + +void CFG::viewCFG() const { +#ifndef NDEBUG + StmtPrinterHelper H(this); + GraphHelper = &H; + llvm::ViewGraph(this,"CFG"); + GraphHelper = NULL; +#else + std::cerr << "CFG::viewCFG is only available in debug builds on " + << "systems with Graphviz or gv!\n"; +#endif +} + +namespace llvm { +template<> +struct DOTGraphTraits<const CFG*> : public DefaultDOTGraphTraits { + static std::string getNodeLabel(const CFGBlock* Node, const CFG* Graph) { + +#ifndef NDEBUG + std::ostringstream Out; + 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 |
