BodyFarm.cpp revision a6d62a10a6e1b8aa3c8294d8cac842c3720df7ff 
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 "BodyFarm.h"
20
21using namespace clang;
22
23//===----------------------------------------------------------------------===//
24// Helper creation functions for constructing faux ASTs.
25//===----------------------------------------------------------------------===//
26
27static bool isDispatchBlock(QualType Ty) {
28  // Is it a block pointer?
29  const BlockPointerType *BPT = Ty->getAs<BlockPointerType>();
30  if (!BPT)
31    return false;
32
33  // Check if the block pointer type takes no arguments and
34  // returns void.
35  const FunctionProtoType *FT =
36  BPT->getPointeeType()->getAs<FunctionProtoType>();
37  if (!FT || !FT->getResultType()->isVoidType()  ||
38      FT->getNumArgs() != 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 DeclRefExpr for the referenced variable.
50  DeclRefExpr *makeDeclRefExpr(const VarDecl *D);
51
52  /// Create an implicit cast for an integer conversion.
53  ImplicitCastExpr *makeIntegralCast(const Expr *Arg, QualType Ty);
54
55private:
56  ASTContext &C;
57};
58}
59
60DeclRefExpr *ASTMaker::makeDeclRefExpr(const VarDecl *D) {
61  DeclRefExpr *DR =
62    DeclRefExpr::Create(/* Ctx = */ C,
63                        /* QualifierLoc = */ NestedNameSpecifierLoc(),
64                        /* TemplateKWLoc = */ SourceLocation(),
65                        /* D = */ const_cast<VarDecl*>(D),
66                        /* isEnclosingLocal = */ false,
67                        /* NameLoc = */ SourceLocation(),
68                        /* T = */ D->getType(),
69                        /* VK = */ VK_LValue);
70  return DR;
71}
72
73ImplicitCastExpr *ASTMaker::makeIntegralCast(const Expr *Arg, QualType Ty) {
74  return ImplicitCastExpr::Create(C, Ty, CK_IntegralCast,
75                                  const_cast<Expr*>(Arg), 0, VK_RValue);
76}
77
78//===----------------------------------------------------------------------===//
79// Creation functions for faux ASTs.
80//===----------------------------------------------------------------------===//
81
82typedef Stmt *(*FunctionFarmer)(ASTContext &C, const FunctionDecl *D);
83
84/// Create a fake body for dispatch_once.
85static Stmt *create_dispatch_once(ASTContext &C, const FunctionDecl *D) {
86  // Check if we have at least two parameters.
87  if (D->param_size() != 2)
88    return 0;
89
90  // Check if the first parameter is a pointer to integer type.
91  const ParmVarDecl *Predicate = D->getParamDecl(0);
92  QualType PredicateQPtrTy = Predicate->getType();
93  const PointerType *PredicatePtrTy = PredicateQPtrTy->getAs<PointerType>();
94  if (!PredicatePtrTy)
95    return 0;
96  QualType PredicateTy = PredicatePtrTy->getPointeeType();
97  if (!PredicateTy->isIntegerType())
98    return 0;
99
100  // Check if the second parameter is the proper block type.
101  const ParmVarDecl *Block = D->getParamDecl(1);
102  QualType Ty = Block->getType();
103  if (!isDispatchBlock(Ty))
104    return 0;
105
106  // Everything checks out.  Create a fakse body that checks the predicate,
107  // sets it, and calls the block.  Basically, an AST dump of:
108  //
109  // void dispatch_once(dispatch_once_t *predicate, dispatch_block_t block) {
110  //  if (!*predicate) {
111  //    *predicate = 1;
112  //    block();
113  //  }
114  // }
115
116  ASTMaker M(C);
117
118  // (1) Create the call.
119  DeclRefExpr *DR = M.makeDeclRefExpr(Block);
120  ImplicitCastExpr *ICE = ImplicitCastExpr::Create(C, Ty, CK_LValueToRValue,
121                                                   DR, 0, VK_RValue);
122  CallExpr *CE = new (C) CallExpr(C, ICE, ArrayRef<Expr*>(), C.VoidTy,
123                                  VK_RValue, SourceLocation());
124
125  // (2) Create the assignment to the predicate.
126  IntegerLiteral *IL =
127    IntegerLiteral::Create(C, llvm::APInt(C.getTypeSize(C.IntTy), (uint64_t) 1),
128                           C.IntTy, SourceLocation());
129  ICE = M.makeIntegralCast(IL, PredicateTy);
130  DR = M.makeDeclRefExpr(Predicate);
131  ImplicitCastExpr *LValToRval =
132    ImplicitCastExpr::Create(C, PredicateQPtrTy, CK_LValueToRValue, DR,
133                             0, VK_RValue);
134  UnaryOperator *UO = new (C) UnaryOperator(LValToRval, UO_Deref, PredicateTy,
135                                            VK_LValue, OK_Ordinary,
136                                            SourceLocation());
137  BinaryOperator *B = new (C) BinaryOperator(UO, ICE, BO_Assign,
138                                             PredicateTy, VK_RValue,
139                                             OK_Ordinary,
140                                             SourceLocation());
141  // (3) Create the compound statement.
142  Stmt *Stmts[2];
143  Stmts[0] = B;
144  Stmts[1] = CE;
145  CompoundStmt *CS = new (C) CompoundStmt(C, Stmts, 2, SourceLocation(),
146                                          SourceLocation());
147
148  // (4) Create the 'if' condition.
149  DR = M.makeDeclRefExpr(Predicate);
150  LValToRval = ImplicitCastExpr::Create(C, PredicateQPtrTy, CK_LValueToRValue,
151                                        DR, 0, VK_RValue);
152  UO = new (C) UnaryOperator(LValToRval, UO_Deref, PredicateTy,
153                             VK_LValue, OK_Ordinary,
154                             SourceLocation());
155  LValToRval = ImplicitCastExpr::Create(C, PredicateTy, CK_LValueToRValue,
156                                        UO, 0, VK_RValue);
157  UO = new (C) UnaryOperator(LValToRval, UO_LNot, C.IntTy,
158                             VK_RValue, OK_Ordinary, SourceLocation());
159
160  // (5) Create the 'if' statement.
161  IfStmt *If = new (C) IfStmt(C, SourceLocation(), 0, UO, CS);
162  return If;
163}
164
165/// Create a fake body for dispatch_sync.
166static Stmt *create_dispatch_sync(ASTContext &C, const FunctionDecl *D) {
167  // Check if we have at least two parameters.
168  if (D->param_size() != 2)
169    return 0;
170
171  // Check if the second parameter is a block.
172  const ParmVarDecl *PV = D->getParamDecl(1);
173  QualType Ty = PV->getType();
174  if (!isDispatchBlock(Ty))
175    return 0;
176
177  // Everything checks out.  Create a fake body that just calls the block.
178  // This is basically just an AST dump of:
179  //
180  // void dispatch_sync(dispatch_queue_t queue, void (^block)(void)) {
181  //   block();
182  // }
183  //
184  ASTMaker M(C);
185  DeclRefExpr *DR = M.makeDeclRefExpr(PV);
186  ImplicitCastExpr *ICE = ImplicitCastExpr::Create(C, Ty, CK_LValueToRValue,
187                                                   DR, 0, VK_RValue);
188  CallExpr *CE = new (C) CallExpr(C, ICE, ArrayRef<Expr*>(), C.VoidTy,
189                                  VK_RValue, SourceLocation());
190  return CE;
191}
192
193Stmt *BodyFarm::getBody(const FunctionDecl *D) {
194  D = D->getCanonicalDecl();
195
196  llvm::Optional<Stmt *> &Val = Bodies[D];
197  if (Val.hasValue())
198    return Val.getValue();
199
200  Val = 0;
201
202  if (D->getIdentifier() == 0)
203    return 0;
204
205  StringRef Name = D->getName();
206  if (Name.empty())
207    return 0;
208
209  FunctionFarmer FF =
210    llvm::StringSwitch<FunctionFarmer>(Name)
211      .Case("dispatch_sync", create_dispatch_sync)
212      .Case("dispatch_once", create_dispatch_once)
213      .Default(NULL);
214
215  if (FF) {
216    Val = FF(C, D);
217  }
218
219  return Val.getValue();
220}
221
222