BodyFarm.cpp revision 5dbd990d7978fb990b61a9bcf1b71314a3e743fe 
1//== BodyFarm.cpp  - Factory for conjuring up fake bodies ----------*- C++ -*-//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// BodyFarm is a factory for creating faux implementations for functions/methods
11// for analysis purposes.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/ADT/StringSwitch.h"
16#include "clang/AST/ASTContext.h"
17#include "clang/AST/Expr.h"
18#include "clang/AST/Decl.h"
19#include "clang/AST/ExprObjC.h"
20#include "BodyFarm.h"
21
22using namespace clang;
23
24//===----------------------------------------------------------------------===//
25// Helper creation functions for constructing faux ASTs.
26//===----------------------------------------------------------------------===//
27
28static bool isDispatchBlock(QualType Ty) {
29  // Is it a block pointer?
30  const BlockPointerType *BPT = Ty->getAs<BlockPointerType>();
31  if (!BPT)
32    return false;
33
34  // Check if the block pointer type takes no arguments and
35  // returns void.
36  const FunctionProtoType *FT =
37  BPT->getPointeeType()->getAs<FunctionProtoType>();
38  if (!FT || !FT->getResultType()->isVoidType()  ||
39      FT->getNumArgs() != 0)
40    return false;
41
42  return true;
43}
44
45namespace {
46class ASTMaker {
47public:
48  ASTMaker(ASTContext &C) : C(C) {}
49
50  /// Create a new BinaryOperator representing a simple assignment.
51  BinaryOperator *makeAssignment(const Expr *LHS, const Expr *RHS, QualType Ty);
52
53  /// Create a new BinaryOperator representing a comparison.
54  BinaryOperator *makeComparison(const Expr *LHS, const Expr *RHS,
55                                 BinaryOperator::Opcode Op);
56
57  /// Create a new compound stmt using the provided statements.
58  CompoundStmt *makeCompound(ArrayRef<Stmt*>);
59
60  /// Create a new DeclRefExpr for the referenced variable.
61  DeclRefExpr *makeDeclRefExpr(const VarDecl *D);
62
63  /// Create a new UnaryOperator representing a dereference.
64  UnaryOperator *makeDereference(const Expr *Arg, QualType Ty);
65
66  /// Create an implicit cast for an integer conversion.
67  Expr *makeIntegralCast(const Expr *Arg, QualType Ty);
68
69  /// Create an implicit cast to a builtin boolean type.
70  ImplicitCastExpr *makeIntegralCastToBoolean(const Expr *Arg);
71
72  // Create an implicit cast for lvalue-to-rvaluate conversions.
73  ImplicitCastExpr *makeLvalueToRvalue(const Expr *Arg, QualType Ty);
74
75  /// Create an Objective-C bool literal.
76  ObjCBoolLiteralExpr *makeObjCBool(bool Val);
77
78  /// Create a Return statement.
79  ReturnStmt *makeReturn(const Expr *RetVal);
80
81private:
82  ASTContext &C;
83};
84}
85
86BinaryOperator *ASTMaker::makeAssignment(const Expr *LHS, const Expr *RHS,
87                                         QualType Ty) {
88 return new (C) BinaryOperator(const_cast<Expr*>(LHS), const_cast<Expr*>(RHS),
89                               BO_Assign, Ty, VK_RValue,
90                               OK_Ordinary, SourceLocation(), false);
91}
92
93BinaryOperator *ASTMaker::makeComparison(const Expr *LHS, const Expr *RHS,
94                                         BinaryOperator::Opcode Op) {
95  assert(BinaryOperator::isLogicalOp(Op) ||
96         BinaryOperator::isComparisonOp(Op));
97  return new (C) BinaryOperator(const_cast<Expr*>(LHS),
98                                const_cast<Expr*>(RHS),
99                                Op,
100                                C.getLogicalOperationType(),
101                                VK_RValue,
102                                OK_Ordinary, SourceLocation(), false);
103}
104
105CompoundStmt *ASTMaker::makeCompound(ArrayRef<Stmt *> Stmts) {
106  return new (C) CompoundStmt(C, const_cast<Stmt**>(Stmts.data()),
107                              Stmts.size(),
108                              SourceLocation(), SourceLocation());
109}
110
111DeclRefExpr *ASTMaker::makeDeclRefExpr(const VarDecl *D) {
112  DeclRefExpr *DR =
113    DeclRefExpr::Create(/* Ctx = */ C,
114                        /* QualifierLoc = */ NestedNameSpecifierLoc(),
115                        /* TemplateKWLoc = */ SourceLocation(),
116                        /* D = */ const_cast<VarDecl*>(D),
117                        /* isEnclosingLocal = */ false,
118                        /* NameLoc = */ SourceLocation(),
119                        /* T = */ D->getType(),
120                        /* VK = */ VK_LValue);
121  return DR;
122}
123
124UnaryOperator *ASTMaker::makeDereference(const Expr *Arg, QualType Ty) {
125  return new (C) UnaryOperator(const_cast<Expr*>(Arg), UO_Deref, Ty,
126                               VK_LValue, OK_Ordinary, SourceLocation());
127}
128
129ImplicitCastExpr *ASTMaker::makeLvalueToRvalue(const Expr *Arg, QualType Ty) {
130  return ImplicitCastExpr::Create(C, Ty, CK_LValueToRValue,
131                                  const_cast<Expr*>(Arg), 0, VK_RValue);
132}
133
134Expr *ASTMaker::makeIntegralCast(const Expr *Arg, QualType Ty) {
135  if (Arg->getType() == Ty)
136    return const_cast<Expr*>(Arg);
137
138  return ImplicitCastExpr::Create(C, Ty, CK_IntegralCast,
139                                  const_cast<Expr*>(Arg), 0, VK_RValue);
140}
141
142ImplicitCastExpr *ASTMaker::makeIntegralCastToBoolean(const Expr *Arg) {
143  return ImplicitCastExpr::Create(C, C.BoolTy, CK_IntegralToBoolean,
144                                  const_cast<Expr*>(Arg), 0, VK_RValue);
145}
146
147ObjCBoolLiteralExpr *ASTMaker::makeObjCBool(bool Val) {
148  QualType Ty = C.getBOOLDecl() ? C.getBOOLType() : C.ObjCBuiltinBoolTy;
149  return new (C) ObjCBoolLiteralExpr(Val, Ty, SourceLocation());
150}
151
152ReturnStmt *ASTMaker::makeReturn(const Expr *RetVal) {
153  return new (C) ReturnStmt(SourceLocation(), const_cast<Expr*>(RetVal), 0);
154}
155
156//===----------------------------------------------------------------------===//
157// Creation functions for faux ASTs.
158//===----------------------------------------------------------------------===//
159
160typedef Stmt *(*FunctionFarmer)(ASTContext &C, const FunctionDecl *D);
161
162/// Create a fake body for dispatch_once.
163static Stmt *create_dispatch_once(ASTContext &C, const FunctionDecl *D) {
164  // Check if we have at least two parameters.
165  if (D->param_size() != 2)
166    return 0;
167
168  // Check if the first parameter is a pointer to integer type.
169  const ParmVarDecl *Predicate = D->getParamDecl(0);
170  QualType PredicateQPtrTy = Predicate->getType();
171  const PointerType *PredicatePtrTy = PredicateQPtrTy->getAs<PointerType>();
172  if (!PredicatePtrTy)
173    return 0;
174  QualType PredicateTy = PredicatePtrTy->getPointeeType();
175  if (!PredicateTy->isIntegerType())
176    return 0;
177
178  // Check if the second parameter is the proper block type.
179  const ParmVarDecl *Block = D->getParamDecl(1);
180  QualType Ty = Block->getType();
181  if (!isDispatchBlock(Ty))
182    return 0;
183
184  // Everything checks out.  Create a fakse body that checks the predicate,
185  // sets it, and calls the block.  Basically, an AST dump of:
186  //
187  // void dispatch_once(dispatch_once_t *predicate, dispatch_block_t block) {
188  //  if (!*predicate) {
189  //    *predicate = 1;
190  //    block();
191  //  }
192  // }
193
194  ASTMaker M(C);
195
196  // (1) Create the call.
197  DeclRefExpr *DR = M.makeDeclRefExpr(Block);
198  ImplicitCastExpr *ICE = M.makeLvalueToRvalue(DR, Ty);
199  CallExpr *CE = new (C) CallExpr(C, ICE, ArrayRef<Expr*>(), C.VoidTy,
200                                  VK_RValue, SourceLocation());
201
202  // (2) Create the assignment to the predicate.
203  IntegerLiteral *IL =
204    IntegerLiteral::Create(C, llvm::APInt(C.getTypeSize(C.IntTy), (uint64_t) 1),
205                           C.IntTy, SourceLocation());
206  BinaryOperator *B =
207    M.makeAssignment(
208       M.makeDereference(
209          M.makeLvalueToRvalue(
210            M.makeDeclRefExpr(Predicate), PredicateQPtrTy),
211            PredicateTy),
212       M.makeIntegralCast(IL, PredicateTy),
213       PredicateTy);
214
215  // (3) Create the compound statement.
216  Stmt *Stmts[2];
217  Stmts[0] = B;
218  Stmts[1] = CE;
219  CompoundStmt *CS = M.makeCompound(ArrayRef<Stmt*>(Stmts, 2));
220
221  // (4) Create the 'if' condition.
222  ImplicitCastExpr *LValToRval =
223    M.makeLvalueToRvalue(
224      M.makeDereference(
225        M.makeLvalueToRvalue(
226          M.makeDeclRefExpr(Predicate),
227          PredicateQPtrTy),
228        PredicateTy),
229    PredicateTy);
230
231  UnaryOperator *UO = new (C) UnaryOperator(LValToRval, UO_LNot, C.IntTy,
232                                           VK_RValue, OK_Ordinary,
233                                           SourceLocation());
234
235  // (5) Create the 'if' statement.
236  IfStmt *If = new (C) IfStmt(C, SourceLocation(), 0, UO, CS);
237  return If;
238}
239
240/// Create a fake body for dispatch_sync.
241static Stmt *create_dispatch_sync(ASTContext &C, const FunctionDecl *D) {
242  // Check if we have at least two parameters.
243  if (D->param_size() != 2)
244    return 0;
245
246  // Check if the second parameter is a block.
247  const ParmVarDecl *PV = D->getParamDecl(1);
248  QualType Ty = PV->getType();
249  if (!isDispatchBlock(Ty))
250    return 0;
251
252  // Everything checks out.  Create a fake body that just calls the block.
253  // This is basically just an AST dump of:
254  //
255  // void dispatch_sync(dispatch_queue_t queue, void (^block)(void)) {
256  //   block();
257  // }
258  //
259  ASTMaker M(C);
260  DeclRefExpr *DR = M.makeDeclRefExpr(PV);
261  ImplicitCastExpr *ICE = M.makeLvalueToRvalue(DR, Ty);
262  CallExpr *CE = new (C) CallExpr(C, ICE, ArrayRef<Expr*>(), C.VoidTy,
263                                  VK_RValue, SourceLocation());
264  return CE;
265}
266
267static Stmt *create_OSAtomicCompareAndSwap(ASTContext &C, const FunctionDecl *D)
268{
269  // There are exactly 3 arguments.
270  if (D->param_size() != 3)
271    return 0;
272
273  // Body for:
274  //   if (oldValue == *theValue) {
275  //    *theValue = newValue;
276  //    return YES;
277  //   }
278  //   else return NO;
279
280  QualType ResultTy = D->getResultType();
281  bool isBoolean = ResultTy->isBooleanType();
282  if (!isBoolean && !ResultTy->isIntegralType(C))
283    return 0;
284
285  const ParmVarDecl *OldValue = D->getParamDecl(0);
286  QualType OldValueTy = OldValue->getType();
287
288  const ParmVarDecl *NewValue = D->getParamDecl(1);
289  QualType NewValueTy = NewValue->getType();
290
291  assert(OldValueTy == NewValueTy);
292
293  const ParmVarDecl *TheValue = D->getParamDecl(2);
294  QualType TheValueTy = TheValue->getType();
295  const PointerType *PT = TheValueTy->getAs<PointerType>();
296  if (!PT)
297    return 0;
298  QualType PointeeTy = PT->getPointeeType();
299
300  ASTMaker M(C);
301  // Construct the comparison.
302  Expr *Comparison =
303    M.makeComparison(
304      M.makeLvalueToRvalue(M.makeDeclRefExpr(OldValue), OldValueTy),
305      M.makeLvalueToRvalue(
306        M.makeDereference(
307          M.makeLvalueToRvalue(M.makeDeclRefExpr(TheValue), TheValueTy),
308          PointeeTy),
309        PointeeTy),
310      BO_EQ);
311
312  // Construct the body of the IfStmt.
313  Stmt *Stmts[2];
314  Stmts[0] =
315    M.makeAssignment(
316      M.makeDereference(
317        M.makeLvalueToRvalue(M.makeDeclRefExpr(TheValue), TheValueTy),
318        PointeeTy),
319      M.makeLvalueToRvalue(M.makeDeclRefExpr(NewValue), NewValueTy),
320      NewValueTy);
321
322  Expr *BoolVal = M.makeObjCBool(true);
323  Expr *RetVal = isBoolean ? M.makeIntegralCastToBoolean(BoolVal)
324                           : M.makeIntegralCast(BoolVal, ResultTy);
325  Stmts[1] = M.makeReturn(RetVal);
326  CompoundStmt *Body = M.makeCompound(ArrayRef<Stmt*>(Stmts, 2));
327
328  // Construct the else clause.
329  BoolVal = M.makeObjCBool(false);
330  RetVal = isBoolean ? M.makeIntegralCastToBoolean(BoolVal)
331                     : M.makeIntegralCast(BoolVal, ResultTy);
332  Stmt *Else = M.makeReturn(RetVal);
333
334  /// Construct the If.
335  Stmt *If =
336    new (C) IfStmt(C, SourceLocation(), 0, Comparison, Body,
337                   SourceLocation(), Else);
338
339  return If;
340}
341
342Stmt *BodyFarm::getBody(const FunctionDecl *D) {
343  D = D->getCanonicalDecl();
344
345  llvm::Optional<Stmt *> &Val = Bodies[D];
346  if (Val.hasValue())
347    return Val.getValue();
348
349  Val = 0;
350
351  if (D->getIdentifier() == 0)
352    return 0;
353
354  StringRef Name = D->getName();
355  if (Name.empty())
356    return 0;
357
358  FunctionFarmer FF;
359
360  if (Name.startswith("OSAtomicCompareAndSwap") ||
361      Name.startswith("objc_atomicCompareAndSwap")) {
362    FF = create_OSAtomicCompareAndSwap;
363  }
364  else {
365    FF = llvm::StringSwitch<FunctionFarmer>(Name)
366          .Case("dispatch_sync", create_dispatch_sync)
367          .Case("dispatch_once", create_dispatch_once)
368        .Default(NULL);
369  }
370
371  if (FF) { Val = FF(C, D); }
372  return Val.getValue();
373}
374
375