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 CLANG_CODEGEN_CGCALL_H
16 #define CLANG_CODEGEN_CGCALL_H
17 
18 #include "CGValue.h"
19 #include "clang/AST/CanonicalType.h"
20 #include "clang/AST/Type.h"
21 #include "llvm/ADT/FoldingSet.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   struct CallArg {
45     RValue RV;
46     QualType Ty;
47     bool NeedsCopy;
48     CallArg(RValue rv, QualType ty, bool needscopy)
49     : RV(rv), Ty(ty), NeedsCopy(needscopy)
50     { }
51   };
52 
53   /// CallArgList - Type for representing both the value and type of
54   /// arguments in a call.
55   class CallArgList :
56     public SmallVector<CallArg, 16> {
57   public:
58     struct Writeback {
59       /// The original argument.  Note that the argument l-value
60       /// is potentially null.
61       LValue Source;
62 
63       /// The temporary alloca.
64       llvm::Value *Temporary;
65 
66       /// A value to "use" after the writeback, or null.
67       llvm::Value *ToUse;
68     };
69 
70     void add(RValue rvalue, QualType type, bool needscopy = false) {
71       push_back(CallArg(rvalue, type, needscopy));
72     }
73 
74     void addFrom(const CallArgList &other) {
75       insert(end(), other.begin(), other.end());
76       Writebacks.insert(Writebacks.end(),
77                         other.Writebacks.begin(), other.Writebacks.end());
78     }
79 
80     void addWriteback(LValue srcLV, llvm::Value *temporary,
81                       llvm::Value *toUse) {
82       Writeback writeback;
83       writeback.Source = srcLV;
84       writeback.Temporary = temporary;
85       writeback.ToUse = toUse;
86       Writebacks.push_back(writeback);
87     }
88 
89     bool hasWritebacks() const { return !Writebacks.empty(); }
90 
91     typedef SmallVectorImpl<Writeback>::const_iterator writeback_iterator;
92     writeback_iterator writeback_begin() const { return Writebacks.begin(); }
93     writeback_iterator writeback_end() const { return Writebacks.end(); }
94 
95   private:
96     SmallVector<Writeback, 1> Writebacks;
97   };
98 
99   /// A class for recording the number of arguments that a function
100   /// signature requires.
101   class RequiredArgs {
102     /// The number of required arguments, or ~0 if the signature does
103     /// not permit optional arguments.
104     unsigned NumRequired;
105   public:
106     enum All_t { All };
107 
108     RequiredArgs(All_t _) : NumRequired(~0U) {}
109     explicit RequiredArgs(unsigned n) : NumRequired(n) {
110       assert(n != ~0U);
111     }
112 
113     /// Compute the arguments required by the given formal prototype,
114     /// given that there may be some additional, non-formal arguments
115     /// in play.
116     static RequiredArgs forPrototypePlus(const FunctionProtoType *prototype,
117                                          unsigned additional) {
118       if (!prototype->isVariadic()) return All;
119       return RequiredArgs(prototype->getNumArgs() + additional);
120     }
121 
122     static RequiredArgs forPrototype(const FunctionProtoType *prototype) {
123       return forPrototypePlus(prototype, 0);
124     }
125 
126     static RequiredArgs forPrototype(CanQual<FunctionProtoType> prototype) {
127       return forPrototype(prototype.getTypePtr());
128     }
129 
130     static RequiredArgs forPrototypePlus(CanQual<FunctionProtoType> prototype,
131                                          unsigned additional) {
132       return forPrototypePlus(prototype.getTypePtr(), additional);
133     }
134 
135     bool allowsOptionalArgs() const { return NumRequired != ~0U; }
136     unsigned getNumRequiredArgs() const {
137       assert(allowsOptionalArgs());
138       return NumRequired;
139     }
140 
141     unsigned getOpaqueData() const { return NumRequired; }
142     static RequiredArgs getFromOpaqueData(unsigned value) {
143       if (value == ~0U) return All;
144       return RequiredArgs(value);
145     }
146   };
147 
148   /// FunctionArgList - Type for representing both the decl and type
149   /// of parameters to a function. The decl must be either a
150   /// ParmVarDecl or ImplicitParamDecl.
151   class FunctionArgList : public SmallVector<const VarDecl*, 16> {
152   };
153 
154   /// CGFunctionInfo - Class to encapsulate the information about a
155   /// function definition.
156   class CGFunctionInfo : public llvm::FoldingSetNode {
157     struct ArgInfo {
158       CanQualType type;
159       ABIArgInfo info;
160     };
161 
162     /// The LLVM::CallingConv to use for this function (as specified by the
163     /// user).
164     unsigned CallingConvention : 8;
165 
166     /// The LLVM::CallingConv to actually use for this function, which may
167     /// depend on the ABI.
168     unsigned EffectiveCallingConvention : 8;
169 
170     /// The clang::CallingConv that this was originally created with.
171     unsigned ASTCallingConvention : 8;
172 
173     /// Whether this function is noreturn.
174     unsigned NoReturn : 1;
175 
176     /// Whether this function is returns-retained.
177     unsigned ReturnsRetained : 1;
178 
179     /// How many arguments to pass inreg.
180     unsigned HasRegParm : 1;
181     unsigned RegParm : 4;
182 
183     RequiredArgs Required;
184 
185     unsigned NumArgs;
186     ArgInfo *getArgsBuffer() {
187       return reinterpret_cast<ArgInfo*>(this+1);
188     }
189     const ArgInfo *getArgsBuffer() const {
190       return reinterpret_cast<const ArgInfo*>(this + 1);
191     }
192 
193     CGFunctionInfo() : Required(RequiredArgs::All) {}
194 
195   public:
196     static CGFunctionInfo *create(unsigned llvmCC,
197                                   const FunctionType::ExtInfo &extInfo,
198                                   CanQualType resultType,
199                                   ArrayRef<CanQualType> argTypes,
200                                   RequiredArgs required);
201 
202     typedef const ArgInfo *const_arg_iterator;
203     typedef ArgInfo *arg_iterator;
204 
205     const_arg_iterator arg_begin() const { return getArgsBuffer() + 1; }
206     const_arg_iterator arg_end() const { return getArgsBuffer() + 1 + NumArgs; }
207     arg_iterator arg_begin() { return getArgsBuffer() + 1; }
208     arg_iterator arg_end() { return getArgsBuffer() + 1 + NumArgs; }
209 
210     unsigned  arg_size() const { return NumArgs; }
211 
212     bool isVariadic() const { return Required.allowsOptionalArgs(); }
213     RequiredArgs getRequiredArgs() const { return Required; }
214 
215     bool isNoReturn() const { return NoReturn; }
216 
217     /// In ARC, whether this function retains its return value.  This
218     /// is not always reliable for call sites.
219     bool isReturnsRetained() const { return ReturnsRetained; }
220 
221     /// getASTCallingConvention() - Return the AST-specified calling
222     /// convention.
223     CallingConv getASTCallingConvention() const {
224       return CallingConv(ASTCallingConvention);
225     }
226 
227     /// getCallingConvention - Return the user specified calling
228     /// convention, which has been translated into an LLVM CC.
229     unsigned getCallingConvention() const { return CallingConvention; }
230 
231     /// getEffectiveCallingConvention - Return the actual calling convention to
232     /// use, which may depend on the ABI.
233     unsigned getEffectiveCallingConvention() const {
234       return EffectiveCallingConvention;
235     }
236     void setEffectiveCallingConvention(unsigned Value) {
237       EffectiveCallingConvention = Value;
238     }
239 
240     bool getHasRegParm() const { return HasRegParm; }
241     unsigned getRegParm() const { return RegParm; }
242 
243     FunctionType::ExtInfo getExtInfo() const {
244       return FunctionType::ExtInfo(isNoReturn(),
245                                    getHasRegParm(), getRegParm(),
246                                    getASTCallingConvention(),
247                                    isReturnsRetained());
248     }
249 
250     CanQualType getReturnType() const { return getArgsBuffer()[0].type; }
251 
252     ABIArgInfo &getReturnInfo() { return getArgsBuffer()[0].info; }
253     const ABIArgInfo &getReturnInfo() const { return getArgsBuffer()[0].info; }
254 
255     void Profile(llvm::FoldingSetNodeID &ID) {
256       ID.AddInteger(getASTCallingConvention());
257       ID.AddBoolean(NoReturn);
258       ID.AddBoolean(ReturnsRetained);
259       ID.AddBoolean(HasRegParm);
260       ID.AddInteger(RegParm);
261       ID.AddInteger(Required.getOpaqueData());
262       getReturnType().Profile(ID);
263       for (arg_iterator it = arg_begin(), ie = arg_end(); it != ie; ++it)
264         it->type.Profile(ID);
265     }
266     static void Profile(llvm::FoldingSetNodeID &ID,
267                         const FunctionType::ExtInfo &info,
268                         RequiredArgs required,
269                         CanQualType resultType,
270                         ArrayRef<CanQualType> argTypes) {
271       ID.AddInteger(info.getCC());
272       ID.AddBoolean(info.getNoReturn());
273       ID.AddBoolean(info.getProducesResult());
274       ID.AddBoolean(info.getHasRegParm());
275       ID.AddInteger(info.getRegParm());
276       ID.AddInteger(required.getOpaqueData());
277       resultType.Profile(ID);
278       for (ArrayRef<CanQualType>::iterator
279              i = argTypes.begin(), e = argTypes.end(); i != e; ++i) {
280         i->Profile(ID);
281       }
282     }
283   };
284 
285   /// ReturnValueSlot - Contains the address where the return value of a
286   /// function can be stored, and whether the address is volatile or not.
287   class ReturnValueSlot {
288     llvm::PointerIntPair<llvm::Value *, 1, bool> Value;
289 
290   public:
291     ReturnValueSlot() {}
292     ReturnValueSlot(llvm::Value *Value, bool IsVolatile)
293       : Value(Value, IsVolatile) {}
294 
295     bool isNull() const { return !getValue(); }
296 
297     bool isVolatile() const { return Value.getInt(); }
298     llvm::Value *getValue() const { return Value.getPointer(); }
299   };
300 
301 }  // end namespace CodeGen
302 }  // end namespace clang
303 
304 #endif
305