clang-1/lib/Analysis/BodyFarm.cpp

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C++

//== BodyFarm.cpp - Factory for conjuring up fake bodies ----------*- C++ -*-//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// BodyFarm is a factory for creating faux implementations for functions/methods
// for analysis purposes.
//
//===----------------------------------------------------------------------===//
#include "BodyFarm.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Decl.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprObjC.h"
#include "llvm/ADT/StringSwitch.h"
using namespace clang;
//===----------------------------------------------------------------------===//
// Helper creation functions for constructing faux ASTs.
//===----------------------------------------------------------------------===//
static bool isDispatchBlock(QualType Ty) {
// Is it a block pointer?
const BlockPointerType *BPT = Ty->getAs<BlockPointerType>();
if (!BPT)
return false;
// Check if the block pointer type takes no arguments and
// returns void.
const FunctionProtoType *FT =
BPT->getPointeeType()->getAs<FunctionProtoType>();
if (!FT || !FT->getResultType()->isVoidType() ||
FT->getNumArgs() != 0)
return false;
return true;
}
namespace {
class ASTMaker {
public:
ASTMaker(ASTContext &C) : C(C) {}
/// Create a new BinaryOperator representing a simple assignment.
BinaryOperator *makeAssignment(const Expr *LHS, const Expr *RHS, QualType Ty);
/// Create a new BinaryOperator representing a comparison.
BinaryOperator *makeComparison(const Expr *LHS, const Expr *RHS,
BinaryOperator::Opcode Op);
/// Create a new compound stmt using the provided statements.
CompoundStmt *makeCompound(ArrayRef<Stmt*>);
/// Create a new DeclRefExpr for the referenced variable.
DeclRefExpr *makeDeclRefExpr(const VarDecl *D);
/// Create a new UnaryOperator representing a dereference.
UnaryOperator *makeDereference(const Expr *Arg, QualType Ty);
/// Create an implicit cast for an integer conversion.
Expr *makeIntegralCast(const Expr *Arg, QualType Ty);
/// Create an implicit cast to a builtin boolean type.
ImplicitCastExpr *makeIntegralCastToBoolean(const Expr *Arg);
// Create an implicit cast for lvalue-to-rvaluate conversions.
ImplicitCastExpr *makeLvalueToRvalue(const Expr *Arg, QualType Ty);
/// Create an Objective-C bool literal.
ObjCBoolLiteralExpr *makeObjCBool(bool Val);
/// Create a Return statement.
ReturnStmt *makeReturn(const Expr *RetVal);
private:
ASTContext &C;
};
}
BinaryOperator *ASTMaker::makeAssignment(const Expr *LHS, const Expr *RHS,
QualType Ty) {
return new (C) BinaryOperator(const_cast<Expr*>(LHS), const_cast<Expr*>(RHS),
BO_Assign, Ty, VK_RValue,
OK_Ordinary, SourceLocation(), false);
}
BinaryOperator *ASTMaker::makeComparison(const Expr *LHS, const Expr *RHS,
BinaryOperator::Opcode Op) {
assert(BinaryOperator::isLogicalOp(Op) ||
BinaryOperator::isComparisonOp(Op));
return new (C) BinaryOperator(const_cast<Expr*>(LHS),
const_cast<Expr*>(RHS),
Op,
C.getLogicalOperationType(),
VK_RValue,
OK_Ordinary, SourceLocation(), false);
}
CompoundStmt *ASTMaker::makeCompound(ArrayRef<Stmt *> Stmts) {
return new (C) CompoundStmt(C, Stmts, SourceLocation(), SourceLocation());
}
DeclRefExpr *ASTMaker::makeDeclRefExpr(const VarDecl *D) {
DeclRefExpr *DR =
DeclRefExpr::Create(/* Ctx = */ C,
/* QualifierLoc = */ NestedNameSpecifierLoc(),
/* TemplateKWLoc = */ SourceLocation(),
/* D = */ const_cast<VarDecl*>(D),
/* isEnclosingLocal = */ false,
/* NameLoc = */ SourceLocation(),
/* T = */ D->getType(),
/* VK = */ VK_LValue);
return DR;
}
UnaryOperator *ASTMaker::makeDereference(const Expr *Arg, QualType Ty) {
return new (C) UnaryOperator(const_cast<Expr*>(Arg), UO_Deref, Ty,
VK_LValue, OK_Ordinary, SourceLocation());
}
ImplicitCastExpr *ASTMaker::makeLvalueToRvalue(const Expr *Arg, QualType Ty) {
return ImplicitCastExpr::Create(C, Ty, CK_LValueToRValue,
const_cast<Expr*>(Arg), 0, VK_RValue);
}
Expr *ASTMaker::makeIntegralCast(const Expr *Arg, QualType Ty) {
if (Arg->getType() == Ty)
return const_cast<Expr*>(Arg);
return ImplicitCastExpr::Create(C, Ty, CK_IntegralCast,
const_cast<Expr*>(Arg), 0, VK_RValue);
}
ImplicitCastExpr *ASTMaker::makeIntegralCastToBoolean(const Expr *Arg) {
return ImplicitCastExpr::Create(C, C.BoolTy, CK_IntegralToBoolean,
const_cast<Expr*>(Arg), 0, VK_RValue);
}
ObjCBoolLiteralExpr *ASTMaker::makeObjCBool(bool Val) {
QualType Ty = C.getBOOLDecl() ? C.getBOOLType() : C.ObjCBuiltinBoolTy;
return new (C) ObjCBoolLiteralExpr(Val, Ty, SourceLocation());
}
ReturnStmt *ASTMaker::makeReturn(const Expr *RetVal) {
return new (C) ReturnStmt(SourceLocation(), const_cast<Expr*>(RetVal), 0);
}
//===----------------------------------------------------------------------===//
// Creation functions for faux ASTs.
//===----------------------------------------------------------------------===//
typedef Stmt *(*FunctionFarmer)(ASTContext &C, const FunctionDecl *D);
/// Create a fake body for dispatch_once.
static Stmt *create_dispatch_once(ASTContext &C, const FunctionDecl *D) {
// Check if we have at least two parameters.
if (D->param_size() != 2)
return 0;
// Check if the first parameter is a pointer to integer type.
const ParmVarDecl *Predicate = D->getParamDecl(0);
QualType PredicateQPtrTy = Predicate->getType();
const PointerType *PredicatePtrTy = PredicateQPtrTy->getAs<PointerType>();
if (!PredicatePtrTy)
return 0;
QualType PredicateTy = PredicatePtrTy->getPointeeType();
if (!PredicateTy->isIntegerType())
return 0;
// Check if the second parameter is the proper block type.
const ParmVarDecl *Block = D->getParamDecl(1);
QualType Ty = Block->getType();
if (!isDispatchBlock(Ty))
return 0;
// Everything checks out. Create a fakse body that checks the predicate,
// sets it, and calls the block. Basically, an AST dump of:
//
// void dispatch_once(dispatch_once_t *predicate, dispatch_block_t block) {
// if (!*predicate) {
// *predicate = 1;
// block();
// }
// }
ASTMaker M(C);
// (1) Create the call.
DeclRefExpr *DR = M.makeDeclRefExpr(Block);
ImplicitCastExpr *ICE = M.makeLvalueToRvalue(DR, Ty);
CallExpr *CE = new (C) CallExpr(C, ICE, ArrayRef<Expr*>(), C.VoidTy,
VK_RValue, SourceLocation());
// (2) Create the assignment to the predicate.
IntegerLiteral *IL =
IntegerLiteral::Create(C, llvm::APInt(C.getTypeSize(C.IntTy), (uint64_t) 1),
C.IntTy, SourceLocation());
BinaryOperator *B =
M.makeAssignment(
M.makeDereference(
M.makeLvalueToRvalue(
M.makeDeclRefExpr(Predicate), PredicateQPtrTy),
PredicateTy),
M.makeIntegralCast(IL, PredicateTy),
PredicateTy);
// (3) Create the compound statement.
Stmt *Stmts[2];
Stmts[0] = B;
Stmts[1] = CE;
CompoundStmt *CS = M.makeCompound(ArrayRef<Stmt*>(Stmts, 2));
// (4) Create the 'if' condition.
ImplicitCastExpr *LValToRval =
M.makeLvalueToRvalue(
M.makeDereference(
M.makeLvalueToRvalue(
M.makeDeclRefExpr(Predicate),
PredicateQPtrTy),
PredicateTy),
PredicateTy);
UnaryOperator *UO = new (C) UnaryOperator(LValToRval, UO_LNot, C.IntTy,
VK_RValue, OK_Ordinary,
SourceLocation());
// (5) Create the 'if' statement.
IfStmt *If = new (C) IfStmt(C, SourceLocation(), 0, UO, CS);
return If;
}
/// Create a fake body for dispatch_sync.
static Stmt *create_dispatch_sync(ASTContext &C, const FunctionDecl *D) {
// Check if we have at least two parameters.
if (D->param_size() != 2)
return 0;
// Check if the second parameter is a block.
const ParmVarDecl *PV = D->getParamDecl(1);
QualType Ty = PV->getType();
if (!isDispatchBlock(Ty))
return 0;
// Everything checks out. Create a fake body that just calls the block.
// This is basically just an AST dump of:
//
// void dispatch_sync(dispatch_queue_t queue, void (^block)(void)) {
// block();
// }
//
ASTMaker M(C);
DeclRefExpr *DR = M.makeDeclRefExpr(PV);
ImplicitCastExpr *ICE = M.makeLvalueToRvalue(DR, Ty);
CallExpr *CE = new (C) CallExpr(C, ICE, ArrayRef<Expr*>(), C.VoidTy,
VK_RValue, SourceLocation());
return CE;
}
static Stmt *create_OSAtomicCompareAndSwap(ASTContext &C, const FunctionDecl *D)
{
// There are exactly 3 arguments.
if (D->param_size() != 3)
return 0;
// Signature:
// _Bool OSAtomicCompareAndSwapPtr(void *__oldValue,
// void *__newValue,
// void * volatile *__theValue)
// Generate body:
// if (oldValue == *theValue) {
// *theValue = newValue;
// return YES;
// }
// else return NO;
QualType ResultTy = D->getResultType();
bool isBoolean = ResultTy->isBooleanType();
if (!isBoolean && !ResultTy->isIntegralType(C))
return 0;
const ParmVarDecl *OldValue = D->getParamDecl(0);
QualType OldValueTy = OldValue->getType();
const ParmVarDecl *NewValue = D->getParamDecl(1);
QualType NewValueTy = NewValue->getType();
assert(OldValueTy == NewValueTy);
const ParmVarDecl *TheValue = D->getParamDecl(2);
QualType TheValueTy = TheValue->getType();
const PointerType *PT = TheValueTy->getAs<PointerType>();
if (!PT)
return 0;
QualType PointeeTy = PT->getPointeeType();
ASTMaker M(C);
// Construct the comparison.
Expr *Comparison =
M.makeComparison(
M.makeLvalueToRvalue(M.makeDeclRefExpr(OldValue), OldValueTy),
M.makeLvalueToRvalue(
M.makeDereference(
M.makeLvalueToRvalue(M.makeDeclRefExpr(TheValue), TheValueTy),
PointeeTy),
PointeeTy),
BO_EQ);
// Construct the body of the IfStmt.
Stmt *Stmts[2];
Stmts[0] =
M.makeAssignment(
M.makeDereference(
M.makeLvalueToRvalue(M.makeDeclRefExpr(TheValue), TheValueTy),
PointeeTy),
M.makeLvalueToRvalue(M.makeDeclRefExpr(NewValue), NewValueTy),
NewValueTy);
Expr *BoolVal = M.makeObjCBool(true);
Expr *RetVal = isBoolean ? M.makeIntegralCastToBoolean(BoolVal)
: M.makeIntegralCast(BoolVal, ResultTy);
Stmts[1] = M.makeReturn(RetVal);
CompoundStmt *Body = M.makeCompound(ArrayRef<Stmt*>(Stmts, 2));
// Construct the else clause.
BoolVal = M.makeObjCBool(false);
RetVal = isBoolean ? M.makeIntegralCastToBoolean(BoolVal)
: M.makeIntegralCast(BoolVal, ResultTy);
Stmt *Else = M.makeReturn(RetVal);
/// Construct the If.
Stmt *If =
new (C) IfStmt(C, SourceLocation(), 0, Comparison, Body,
SourceLocation(), Else);
return If;
}
Stmt *BodyFarm::getBody(const FunctionDecl *D) {
D = D->getCanonicalDecl();
Optional<Stmt *> &Val = Bodies[D];
if (Val.hasValue())
return Val.getValue();
Val = 0;
if (D->getIdentifier() == 0)
return 0;
StringRef Name = D->getName();
if (Name.empty())
return 0;
FunctionFarmer FF;
if (Name.startswith("OSAtomicCompareAndSwap") ||
Name.startswith("objc_atomicCompareAndSwap")) {
FF = create_OSAtomicCompareAndSwap;
}
else {
FF = llvm::StringSwitch<FunctionFarmer>(Name)
.Case("dispatch_sync", create_dispatch_sync)
.Case("dispatch_once", create_dispatch_once)
.Default(NULL);
}
if (FF) { Val = FF(C, D); }
return Val.getValue();
}