BodyFarm.cpp revision 651f13cea278ec967336033dd032faef0e9fc2ec 
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 "BodyFarm.h"
16#include "clang/AST/ASTContext.h"
17#include "clang/AST/Decl.h"
18#include "clang/AST/Expr.h"
19#include "clang/AST/ExprObjC.h"
20#include "llvm/ADT/StringSwitch.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->getReturnType()->isVoidType() || FT->getNumParams() != 0)
39    return false;
40
41  return true;
42}
43
44namespace {
45class ASTMaker {
46public:
47  ASTMaker(ASTContext &C) : C(C) {}
48
49  /// Create a new BinaryOperator representing a simple assignment.
50  BinaryOperator *makeAssignment(const Expr *LHS, const Expr *RHS, QualType Ty);
51
52  /// Create a new BinaryOperator representing a comparison.
53  BinaryOperator *makeComparison(const Expr *LHS, const Expr *RHS,
54                                 BinaryOperator::Opcode Op);
55
56  /// Create a new compound stmt using the provided statements.
57  CompoundStmt *makeCompound(ArrayRef<Stmt*>);
58
59  /// Create a new DeclRefExpr for the referenced variable.
60  DeclRefExpr *makeDeclRefExpr(const VarDecl *D);
61
62  /// Create a new UnaryOperator representing a dereference.
63  UnaryOperator *makeDereference(const Expr *Arg, QualType Ty);
64
65  /// Create an implicit cast for an integer conversion.
66  Expr *makeIntegralCast(const Expr *Arg, QualType Ty);
67
68  /// Create an implicit cast to a builtin boolean type.
69  ImplicitCastExpr *makeIntegralCastToBoolean(const Expr *Arg);
70
71  // Create an implicit cast for lvalue-to-rvaluate conversions.
72  ImplicitCastExpr *makeLvalueToRvalue(const Expr *Arg, QualType Ty);
73
74  /// Create an Objective-C bool literal.
75  ObjCBoolLiteralExpr *makeObjCBool(bool Val);
76
77  /// Create an Objective-C ivar reference.
78  ObjCIvarRefExpr *makeObjCIvarRef(const Expr *Base, const ObjCIvarDecl *IVar);
79
80  /// Create a Return statement.
81  ReturnStmt *makeReturn(const Expr *RetVal);
82
83private:
84  ASTContext &C;
85};
86}
87
88BinaryOperator *ASTMaker::makeAssignment(const Expr *LHS, const Expr *RHS,
89                                         QualType Ty) {
90 return new (C) BinaryOperator(const_cast<Expr*>(LHS), const_cast<Expr*>(RHS),
91                               BO_Assign, Ty, VK_RValue,
92                               OK_Ordinary, SourceLocation(), false);
93}
94
95BinaryOperator *ASTMaker::makeComparison(const Expr *LHS, const Expr *RHS,
96                                         BinaryOperator::Opcode Op) {
97  assert(BinaryOperator::isLogicalOp(Op) ||
98         BinaryOperator::isComparisonOp(Op));
99  return new (C) BinaryOperator(const_cast<Expr*>(LHS),
100                                const_cast<Expr*>(RHS),
101                                Op,
102                                C.getLogicalOperationType(),
103                                VK_RValue,
104                                OK_Ordinary, SourceLocation(), false);
105}
106
107CompoundStmt *ASTMaker::makeCompound(ArrayRef<Stmt *> Stmts) {
108  return new (C) CompoundStmt(C, Stmts, 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
152ObjCIvarRefExpr *ASTMaker::makeObjCIvarRef(const Expr *Base,
153                                           const ObjCIvarDecl *IVar) {
154  return new (C) ObjCIvarRefExpr(const_cast<ObjCIvarDecl*>(IVar),
155                                 IVar->getType(), SourceLocation(),
156                                 SourceLocation(), const_cast<Expr*>(Base),
157                                 /*arrow=*/true, /*free=*/false);
158}
159
160
161ReturnStmt *ASTMaker::makeReturn(const Expr *RetVal) {
162  return new (C) ReturnStmt(SourceLocation(), const_cast<Expr*>(RetVal), 0);
163}
164
165//===----------------------------------------------------------------------===//
166// Creation functions for faux ASTs.
167//===----------------------------------------------------------------------===//
168
169typedef Stmt *(*FunctionFarmer)(ASTContext &C, const FunctionDecl *D);
170
171/// Create a fake body for dispatch_once.
172static Stmt *create_dispatch_once(ASTContext &C, const FunctionDecl *D) {
173  // Check if we have at least two parameters.
174  if (D->param_size() != 2)
175    return 0;
176
177  // Check if the first parameter is a pointer to integer type.
178  const ParmVarDecl *Predicate = D->getParamDecl(0);
179  QualType PredicateQPtrTy = Predicate->getType();
180  const PointerType *PredicatePtrTy = PredicateQPtrTy->getAs<PointerType>();
181  if (!PredicatePtrTy)
182    return 0;
183  QualType PredicateTy = PredicatePtrTy->getPointeeType();
184  if (!PredicateTy->isIntegerType())
185    return 0;
186
187  // Check if the second parameter is the proper block type.
188  const ParmVarDecl *Block = D->getParamDecl(1);
189  QualType Ty = Block->getType();
190  if (!isDispatchBlock(Ty))
191    return 0;
192
193  // Everything checks out.  Create a fakse body that checks the predicate,
194  // sets it, and calls the block.  Basically, an AST dump of:
195  //
196  // void dispatch_once(dispatch_once_t *predicate, dispatch_block_t block) {
197  //  if (!*predicate) {
198  //    *predicate = 1;
199  //    block();
200  //  }
201  // }
202
203  ASTMaker M(C);
204
205  // (1) Create the call.
206  DeclRefExpr *DR = M.makeDeclRefExpr(Block);
207  ImplicitCastExpr *ICE = M.makeLvalueToRvalue(DR, Ty);
208  CallExpr *CE = new (C) CallExpr(C, ICE, None, C.VoidTy, VK_RValue,
209                                  SourceLocation());
210
211  // (2) Create the assignment to the predicate.
212  IntegerLiteral *IL =
213    IntegerLiteral::Create(C, llvm::APInt(C.getTypeSize(C.IntTy), (uint64_t) 1),
214                           C.IntTy, SourceLocation());
215  BinaryOperator *B =
216    M.makeAssignment(
217       M.makeDereference(
218          M.makeLvalueToRvalue(
219            M.makeDeclRefExpr(Predicate), PredicateQPtrTy),
220            PredicateTy),
221       M.makeIntegralCast(IL, PredicateTy),
222       PredicateTy);
223
224  // (3) Create the compound statement.
225  Stmt *Stmts[2];
226  Stmts[0] = B;
227  Stmts[1] = CE;
228  CompoundStmt *CS = M.makeCompound(ArrayRef<Stmt*>(Stmts, 2));
229
230  // (4) Create the 'if' condition.
231  ImplicitCastExpr *LValToRval =
232    M.makeLvalueToRvalue(
233      M.makeDereference(
234        M.makeLvalueToRvalue(
235          M.makeDeclRefExpr(Predicate),
236          PredicateQPtrTy),
237        PredicateTy),
238    PredicateTy);
239
240  UnaryOperator *UO = new (C) UnaryOperator(LValToRval, UO_LNot, C.IntTy,
241                                           VK_RValue, OK_Ordinary,
242                                           SourceLocation());
243
244  // (5) Create the 'if' statement.
245  IfStmt *If = new (C) IfStmt(C, SourceLocation(), 0, UO, CS);
246  return If;
247}
248
249/// Create a fake body for dispatch_sync.
250static Stmt *create_dispatch_sync(ASTContext &C, const FunctionDecl *D) {
251  // Check if we have at least two parameters.
252  if (D->param_size() != 2)
253    return 0;
254
255  // Check if the second parameter is a block.
256  const ParmVarDecl *PV = D->getParamDecl(1);
257  QualType Ty = PV->getType();
258  if (!isDispatchBlock(Ty))
259    return 0;
260
261  // Everything checks out.  Create a fake body that just calls the block.
262  // This is basically just an AST dump of:
263  //
264  // void dispatch_sync(dispatch_queue_t queue, void (^block)(void)) {
265  //   block();
266  // }
267  //
268  ASTMaker M(C);
269  DeclRefExpr *DR = M.makeDeclRefExpr(PV);
270  ImplicitCastExpr *ICE = M.makeLvalueToRvalue(DR, Ty);
271  CallExpr *CE = new (C) CallExpr(C, ICE, None, C.VoidTy, VK_RValue,
272                                  SourceLocation());
273  return CE;
274}
275
276static Stmt *create_OSAtomicCompareAndSwap(ASTContext &C, const FunctionDecl *D)
277{
278  // There are exactly 3 arguments.
279  if (D->param_size() != 3)
280    return 0;
281
282  // Signature:
283  // _Bool OSAtomicCompareAndSwapPtr(void *__oldValue,
284  //                                 void *__newValue,
285  //                                 void * volatile *__theValue)
286  // Generate body:
287  //   if (oldValue == *theValue) {
288  //    *theValue = newValue;
289  //    return YES;
290  //   }
291  //   else return NO;
292
293  QualType ResultTy = D->getReturnType();
294  bool isBoolean = ResultTy->isBooleanType();
295  if (!isBoolean && !ResultTy->isIntegralType(C))
296    return 0;
297
298  const ParmVarDecl *OldValue = D->getParamDecl(0);
299  QualType OldValueTy = OldValue->getType();
300
301  const ParmVarDecl *NewValue = D->getParamDecl(1);
302  QualType NewValueTy = NewValue->getType();
303
304  assert(OldValueTy == NewValueTy);
305
306  const ParmVarDecl *TheValue = D->getParamDecl(2);
307  QualType TheValueTy = TheValue->getType();
308  const PointerType *PT = TheValueTy->getAs<PointerType>();
309  if (!PT)
310    return 0;
311  QualType PointeeTy = PT->getPointeeType();
312
313  ASTMaker M(C);
314  // Construct the comparison.
315  Expr *Comparison =
316    M.makeComparison(
317      M.makeLvalueToRvalue(M.makeDeclRefExpr(OldValue), OldValueTy),
318      M.makeLvalueToRvalue(
319        M.makeDereference(
320          M.makeLvalueToRvalue(M.makeDeclRefExpr(TheValue), TheValueTy),
321          PointeeTy),
322        PointeeTy),
323      BO_EQ);
324
325  // Construct the body of the IfStmt.
326  Stmt *Stmts[2];
327  Stmts[0] =
328    M.makeAssignment(
329      M.makeDereference(
330        M.makeLvalueToRvalue(M.makeDeclRefExpr(TheValue), TheValueTy),
331        PointeeTy),
332      M.makeLvalueToRvalue(M.makeDeclRefExpr(NewValue), NewValueTy),
333      NewValueTy);
334
335  Expr *BoolVal = M.makeObjCBool(true);
336  Expr *RetVal = isBoolean ? M.makeIntegralCastToBoolean(BoolVal)
337                           : M.makeIntegralCast(BoolVal, ResultTy);
338  Stmts[1] = M.makeReturn(RetVal);
339  CompoundStmt *Body = M.makeCompound(ArrayRef<Stmt*>(Stmts, 2));
340
341  // Construct the else clause.
342  BoolVal = M.makeObjCBool(false);
343  RetVal = isBoolean ? M.makeIntegralCastToBoolean(BoolVal)
344                     : M.makeIntegralCast(BoolVal, ResultTy);
345  Stmt *Else = M.makeReturn(RetVal);
346
347  /// Construct the If.
348  Stmt *If =
349    new (C) IfStmt(C, SourceLocation(), 0, Comparison, Body,
350                   SourceLocation(), Else);
351
352  return If;
353}
354
355Stmt *BodyFarm::getBody(const FunctionDecl *D) {
356  D = D->getCanonicalDecl();
357
358  Optional<Stmt *> &Val = Bodies[D];
359  if (Val.hasValue())
360    return Val.getValue();
361
362  Val = 0;
363
364  if (D->getIdentifier() == 0)
365    return 0;
366
367  StringRef Name = D->getName();
368  if (Name.empty())
369    return 0;
370
371  FunctionFarmer FF;
372
373  if (Name.startswith("OSAtomicCompareAndSwap") ||
374      Name.startswith("objc_atomicCompareAndSwap")) {
375    FF = create_OSAtomicCompareAndSwap;
376  }
377  else {
378    FF = llvm::StringSwitch<FunctionFarmer>(Name)
379          .Case("dispatch_sync", create_dispatch_sync)
380          .Case("dispatch_once", create_dispatch_once)
381        .Default(NULL);
382  }
383
384  if (FF) { Val = FF(C, D); }
385  return Val.getValue();
386}
387
388static Stmt *createObjCPropertyGetter(ASTContext &Ctx,
389                                      const ObjCPropertyDecl *Prop) {
390  // First, find the backing ivar.
391  const ObjCIvarDecl *IVar = Prop->getPropertyIvarDecl();
392  if (!IVar)
393    return 0;
394
395  // Ignore weak variables, which have special behavior.
396  if (Prop->getPropertyAttributes() & ObjCPropertyDecl::OBJC_PR_weak)
397    return 0;
398
399  // Look to see if Sema has synthesized a body for us. This happens in
400  // Objective-C++ because the return value may be a C++ class type with a
401  // non-trivial copy constructor. We can only do this if we can find the
402  // @synthesize for this property, though (or if we know it's been auto-
403  // synthesized).
404  const ObjCImplementationDecl *ImplDecl =
405    IVar->getContainingInterface()->getImplementation();
406  if (ImplDecl) {
407    for (const auto *I : ImplDecl->property_impls()) {
408      if (I->getPropertyDecl() != Prop)
409        continue;
410
411      if (I->getGetterCXXConstructor()) {
412        ASTMaker M(Ctx);
413        return M.makeReturn(I->getGetterCXXConstructor());
414      }
415    }
416  }
417
418  // Sanity check that the property is the same type as the ivar, or a
419  // reference to it, and that it is either an object pointer or trivially
420  // copyable.
421  if (!Ctx.hasSameUnqualifiedType(IVar->getType(),
422                                  Prop->getType().getNonReferenceType()))
423    return 0;
424  if (!IVar->getType()->isObjCLifetimeType() &&
425      !IVar->getType().isTriviallyCopyableType(Ctx))
426    return 0;
427
428  // Generate our body:
429  //   return self->_ivar;
430  ASTMaker M(Ctx);
431
432  const VarDecl *selfVar = Prop->getGetterMethodDecl()->getSelfDecl();
433
434  Expr *loadedIVar =
435    M.makeObjCIvarRef(
436      M.makeLvalueToRvalue(
437        M.makeDeclRefExpr(selfVar),
438        selfVar->getType()),
439      IVar);
440
441  if (!Prop->getType()->isReferenceType())
442    loadedIVar = M.makeLvalueToRvalue(loadedIVar, IVar->getType());
443
444  return M.makeReturn(loadedIVar);
445}
446
447Stmt *BodyFarm::getBody(const ObjCMethodDecl *D) {
448  // We currently only know how to synthesize property accessors.
449  if (!D->isPropertyAccessor())
450    return 0;
451
452  D = D->getCanonicalDecl();
453
454  Optional<Stmt *> &Val = Bodies[D];
455  if (Val.hasValue())
456    return Val.getValue();
457  Val = 0;
458
459  const ObjCPropertyDecl *Prop = D->findPropertyDecl();
460  if (!Prop)
461    return 0;
462
463  // For now, we only synthesize getters.
464  if (D->param_size() != 0)
465    return 0;
466
467  Val = createObjCPropertyGetter(C, Prop);
468
469  return Val.getValue();
470}
471
472