1 //===----- CGCall.h - Encapsulate calling convention details ----*- 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 // These classes wrap the information about a call or function
11 // definition used to handle ABI compliancy.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_CLANG_LIB_CODEGEN_CGCALL_H
16 #define LLVM_CLANG_LIB_CODEGEN_CGCALL_H
17 
18 #include "CGValue.h"
19 #include "EHScopeStack.h"
20 #include "clang/AST/CanonicalType.h"
21 #include "clang/AST/Type.h"
22 #include "llvm/IR/Value.h"
23 
24 // FIXME: Restructure so we don't have to expose so much stuff.
25 #include "ABIInfo.h"
26 
27 namespace llvm {
28   class AttributeSet;
29   class Function;
30   class Type;
31   class Value;
32 }
33 
34 namespace clang {
35   class ASTContext;
36   class Decl;
37   class FunctionDecl;
38   class ObjCMethodDecl;
39   class VarDecl;
40 
41 namespace CodeGen {
42   typedef SmallVector<llvm::AttributeSet, 8> AttributeListType;
43 
44   /// Abstract information about a function or function prototype.
45   class CGCalleeInfo {
46     /// \brief The function prototype of the callee.
47     const FunctionProtoType *CalleeProtoTy;
48     /// \brief The function declaration of the callee.
49     const Decl *CalleeDecl;
50 
51   public:
52     explicit CGCalleeInfo() : CalleeProtoTy(nullptr), CalleeDecl(nullptr) {}
53     CGCalleeInfo(const FunctionProtoType *calleeProtoTy, const Decl *calleeDecl)
54         : CalleeProtoTy(calleeProtoTy), CalleeDecl(calleeDecl) {}
55     CGCalleeInfo(const FunctionProtoType *calleeProtoTy)
56         : CalleeProtoTy(calleeProtoTy), CalleeDecl(nullptr) {}
57     CGCalleeInfo(const Decl *calleeDecl)
58         : CalleeProtoTy(nullptr), CalleeDecl(calleeDecl) {}
59 
60     const FunctionProtoType *getCalleeFunctionProtoType() const {
61       return CalleeProtoTy;
62     }
63     const Decl *getCalleeDecl() const { return CalleeDecl; }
64   };
65 
66   /// All available information about a concrete callee.
67   class CGCallee {
68     enum class SpecialKind : uintptr_t {
69       Invalid,
70       Builtin,
71       PseudoDestructor,
72 
73       Last = PseudoDestructor
74     };
75 
76     SpecialKind KindOrFunctionPointer;
77     union {
78       CGCalleeInfo AbstractInfo;
79       struct {
80         const FunctionDecl *Decl;
81         unsigned ID;
82       } BuiltinInfo;
83       struct {
84         const CXXPseudoDestructorExpr *Expr;
85       } PseudoDestructorInfo;
86     };
87 
88     explicit CGCallee(SpecialKind kind) : KindOrFunctionPointer(kind) {}
89 
90     CGCallee(const FunctionDecl *builtinDecl, unsigned builtinID)
91         : KindOrFunctionPointer(SpecialKind::Builtin) {
92       BuiltinInfo.Decl = builtinDecl;
93       BuiltinInfo.ID = builtinID;
94     }
95 
96   public:
97     CGCallee() : KindOrFunctionPointer(SpecialKind::Invalid) {}
98 
99     /// Construct a callee.  Call this constructor directly when this
100     /// isn't a direct call.
101     CGCallee(const CGCalleeInfo &abstractInfo, llvm::Value *functionPtr)
102         : KindOrFunctionPointer(SpecialKind(uintptr_t(functionPtr))) {
103       AbstractInfo = abstractInfo;
104       assert(functionPtr && "configuring callee without function pointer");
105       assert(functionPtr->getType()->isPointerTy());
106       assert(functionPtr->getType()->getPointerElementType()->isFunctionTy());
107     }
108 
109     static CGCallee forBuiltin(unsigned builtinID,
110                                const FunctionDecl *builtinDecl) {
111       CGCallee result(SpecialKind::Builtin);
112       result.BuiltinInfo.Decl = builtinDecl;
113       result.BuiltinInfo.ID = builtinID;
114       return result;
115     }
116 
117     static CGCallee forPseudoDestructor(const CXXPseudoDestructorExpr *E) {
118       CGCallee result(SpecialKind::PseudoDestructor);
119       result.PseudoDestructorInfo.Expr = E;
120       return result;
121     }
122 
123     static CGCallee forDirect(llvm::Constant *functionPtr,
124                         const CGCalleeInfo &abstractInfo = CGCalleeInfo()) {
125       return CGCallee(abstractInfo, functionPtr);
126     }
127 
128     bool isBuiltin() const {
129       return KindOrFunctionPointer == SpecialKind::Builtin;
130     }
131     const FunctionDecl *getBuiltinDecl() const {
132       assert(isBuiltin());
133       return BuiltinInfo.Decl;
134     }
135     unsigned getBuiltinID() const {
136       assert(isBuiltin());
137       return BuiltinInfo.ID;
138     }
139 
140     bool isPseudoDestructor() const {
141       return KindOrFunctionPointer == SpecialKind::PseudoDestructor;
142     }
143     const CXXPseudoDestructorExpr *getPseudoDestructorExpr() const {
144       assert(isPseudoDestructor());
145       return PseudoDestructorInfo.Expr;
146     }
147 
148     bool isOrdinary() const {
149       return uintptr_t(KindOrFunctionPointer) > uintptr_t(SpecialKind::Last);
150     }
151     const CGCalleeInfo &getAbstractInfo() const {
152       assert(isOrdinary());
153       return AbstractInfo;
154     }
155     llvm::Value *getFunctionPointer() const {
156       assert(isOrdinary());
157       return reinterpret_cast<llvm::Value*>(uintptr_t(KindOrFunctionPointer));
158     }
159     llvm::FunctionType *getFunctionType() const {
160       return cast<llvm::FunctionType>(
161                     getFunctionPointer()->getType()->getPointerElementType());
162     }
163     void setFunctionPointer(llvm::Value *functionPtr) {
164       assert(isOrdinary());
165       KindOrFunctionPointer = SpecialKind(uintptr_t(functionPtr));
166     }
167   };
168 
169   struct CallArg {
170     RValue RV;
171     QualType Ty;
172     bool NeedsCopy;
173     CallArg(RValue rv, QualType ty, bool needscopy)
174     : RV(rv), Ty(ty), NeedsCopy(needscopy)
175     { }
176   };
177 
178   /// CallArgList - Type for representing both the value and type of
179   /// arguments in a call.
180   class CallArgList :
181     public SmallVector<CallArg, 16> {
182   public:
183     CallArgList() : StackBase(nullptr) {}
184 
185     struct Writeback {
186       /// The original argument.  Note that the argument l-value
187       /// is potentially null.
188       LValue Source;
189 
190       /// The temporary alloca.
191       Address Temporary;
192 
193       /// A value to "use" after the writeback, or null.
194       llvm::Value *ToUse;
195     };
196 
197     struct CallArgCleanup {
198       EHScopeStack::stable_iterator Cleanup;
199 
200       /// The "is active" insertion point.  This instruction is temporary and
201       /// will be removed after insertion.
202       llvm::Instruction *IsActiveIP;
203     };
204 
205     void add(RValue rvalue, QualType type, bool needscopy = false) {
206       push_back(CallArg(rvalue, type, needscopy));
207     }
208 
209     /// Add all the arguments from another CallArgList to this one. After doing
210     /// this, the old CallArgList retains its list of arguments, but must not
211     /// be used to emit a call.
212     void addFrom(const CallArgList &other) {
213       insert(end(), other.begin(), other.end());
214       Writebacks.insert(Writebacks.end(),
215                         other.Writebacks.begin(), other.Writebacks.end());
216       CleanupsToDeactivate.insert(CleanupsToDeactivate.end(),
217                                   other.CleanupsToDeactivate.begin(),
218                                   other.CleanupsToDeactivate.end());
219       assert(!(StackBase && other.StackBase) && "can't merge stackbases");
220       if (!StackBase)
221         StackBase = other.StackBase;
222     }
223 
224     void addWriteback(LValue srcLV, Address temporary,
225                       llvm::Value *toUse) {
226       Writeback writeback = { srcLV, temporary, toUse };
227       Writebacks.push_back(writeback);
228     }
229 
230     bool hasWritebacks() const { return !Writebacks.empty(); }
231 
232     typedef llvm::iterator_range<SmallVectorImpl<Writeback>::const_iterator>
233       writeback_const_range;
234 
235     writeback_const_range writebacks() const {
236       return writeback_const_range(Writebacks.begin(), Writebacks.end());
237     }
238 
239     void addArgCleanupDeactivation(EHScopeStack::stable_iterator Cleanup,
240                                    llvm::Instruction *IsActiveIP) {
241       CallArgCleanup ArgCleanup;
242       ArgCleanup.Cleanup = Cleanup;
243       ArgCleanup.IsActiveIP = IsActiveIP;
244       CleanupsToDeactivate.push_back(ArgCleanup);
245     }
246 
247     ArrayRef<CallArgCleanup> getCleanupsToDeactivate() const {
248       return CleanupsToDeactivate;
249     }
250 
251     void allocateArgumentMemory(CodeGenFunction &CGF);
252     llvm::Instruction *getStackBase() const { return StackBase; }
253     void freeArgumentMemory(CodeGenFunction &CGF) const;
254 
255     /// \brief Returns if we're using an inalloca struct to pass arguments in
256     /// memory.
257     bool isUsingInAlloca() const { return StackBase; }
258 
259   private:
260     SmallVector<Writeback, 1> Writebacks;
261 
262     /// Deactivate these cleanups immediately before making the call.  This
263     /// is used to cleanup objects that are owned by the callee once the call
264     /// occurs.
265     SmallVector<CallArgCleanup, 1> CleanupsToDeactivate;
266 
267     /// The stacksave call.  It dominates all of the argument evaluation.
268     llvm::CallInst *StackBase;
269   };
270 
271   /// FunctionArgList - Type for representing both the decl and type
272   /// of parameters to a function. The decl must be either a
273   /// ParmVarDecl or ImplicitParamDecl.
274   class FunctionArgList : public SmallVector<const VarDecl*, 16> {
275   };
276 
277   /// ReturnValueSlot - Contains the address where the return value of a
278   /// function can be stored, and whether the address is volatile or not.
279   class ReturnValueSlot {
280     llvm::PointerIntPair<llvm::Value *, 2, unsigned int> Value;
281     CharUnits Alignment;
282 
283     // Return value slot flags
284     enum Flags {
285       IS_VOLATILE = 0x1,
286       IS_UNUSED = 0x2,
287     };
288 
289   public:
290     ReturnValueSlot() {}
291     ReturnValueSlot(Address Addr, bool IsVolatile, bool IsUnused = false)
292       : Value(Addr.isValid() ? Addr.getPointer() : nullptr,
293               (IsVolatile ? IS_VOLATILE : 0) | (IsUnused ? IS_UNUSED : 0)),
294         Alignment(Addr.isValid() ? Addr.getAlignment() : CharUnits::Zero()) {}
295 
296     bool isNull() const { return !getValue().isValid(); }
297 
298     bool isVolatile() const { return Value.getInt() & IS_VOLATILE; }
299     Address getValue() const { return Address(Value.getPointer(), Alignment); }
300     bool isUnused() const { return Value.getInt() & IS_UNUSED; }
301   };
302 
303 }  // end namespace CodeGen
304 }  // end namespace clang
305 
306 #endif
307