1 //===----- CGCall.h - Encapsulate calling convention details ----*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // These classes wrap the information about a call or function
10 // definition used to handle ABI compliancy.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_LIB_CODEGEN_CGCALL_H
15 #define LLVM_CLANG_LIB_CODEGEN_CGCALL_H
16 
17 #include "CGValue.h"
18 #include "EHScopeStack.h"
19 #include "clang/AST/ASTFwd.h"
20 #include "clang/AST/CanonicalType.h"
21 #include "clang/AST/GlobalDecl.h"
22 #include "clang/AST/Type.h"
23 #include "llvm/IR/Value.h"
24 
25 // FIXME: Restructure so we don't have to expose so much stuff.
26 #include "ABIInfo.h"
27 
28 namespace llvm {
29 class AttributeList;
30 class Function;
31 class Type;
32 class Value;
33 } // namespace llvm
34 
35 namespace clang {
36 class ASTContext;
37 class Decl;
38 class FunctionDecl;
39 class ObjCMethodDecl;
40 class VarDecl;
41 
42 namespace CodeGen {
43 
44 /// Abstract information about a function or function prototype.
45 class CGCalleeInfo {
46   /// The function prototype of the callee.
47   const FunctionProtoType *CalleeProtoTy;
48   /// The function declaration of the callee.
49   GlobalDecl CalleeDecl;
50 
51 public:
52   explicit CGCalleeInfo() : CalleeProtoTy(nullptr), CalleeDecl() {}
53   CGCalleeInfo(const FunctionProtoType *calleeProtoTy, GlobalDecl calleeDecl)
54       : CalleeProtoTy(calleeProtoTy), CalleeDecl(calleeDecl) {}
55   CGCalleeInfo(const FunctionProtoType *calleeProtoTy)
56       : CalleeProtoTy(calleeProtoTy), CalleeDecl() {}
57   CGCalleeInfo(GlobalDecl calleeDecl)
58       : CalleeProtoTy(nullptr), CalleeDecl(calleeDecl) {}
59 
60   const FunctionProtoType *getCalleeFunctionProtoType() const {
61     return CalleeProtoTy;
62   }
63   const GlobalDecl 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     Virtual,
73 
74     Last = Virtual
75   };
76 
77   struct BuiltinInfoStorage {
78     const FunctionDecl *Decl;
79     unsigned ID;
80   };
81   struct PseudoDestructorInfoStorage {
82     const CXXPseudoDestructorExpr *Expr;
83   };
84   struct VirtualInfoStorage {
85     const CallExpr *CE;
86     GlobalDecl MD;
87     Address Addr;
88     llvm::FunctionType *FTy;
89   };
90 
91   SpecialKind KindOrFunctionPointer;
92   union {
93     CGCalleeInfo AbstractInfo;
94     BuiltinInfoStorage BuiltinInfo;
95     PseudoDestructorInfoStorage PseudoDestructorInfo;
96     VirtualInfoStorage VirtualInfo;
97   };
98 
99   explicit CGCallee(SpecialKind kind) : KindOrFunctionPointer(kind) {}
100 
101   CGCallee(const FunctionDecl *builtinDecl, unsigned builtinID)
102       : KindOrFunctionPointer(SpecialKind::Builtin) {
103     BuiltinInfo.Decl = builtinDecl;
104     BuiltinInfo.ID = builtinID;
105   }
106 
107 public:
108   CGCallee() : KindOrFunctionPointer(SpecialKind::Invalid) {}
109 
110   /// Construct a callee.  Call this constructor directly when this
111   /// isn't a direct call.
112   CGCallee(const CGCalleeInfo &abstractInfo, llvm::Value *functionPtr)
113       : KindOrFunctionPointer(
114             SpecialKind(reinterpret_cast<uintptr_t>(functionPtr))) {
115     AbstractInfo = abstractInfo;
116     assert(functionPtr && "configuring callee without function pointer");
117     assert(functionPtr->getType()->isPointerTy());
118     assert(functionPtr->getType()->getPointerElementType()->isFunctionTy());
119   }
120 
121   static CGCallee forBuiltin(unsigned builtinID,
122                              const FunctionDecl *builtinDecl) {
123     CGCallee result(SpecialKind::Builtin);
124     result.BuiltinInfo.Decl = builtinDecl;
125     result.BuiltinInfo.ID = builtinID;
126     return result;
127   }
128 
129   static CGCallee forPseudoDestructor(const CXXPseudoDestructorExpr *E) {
130     CGCallee result(SpecialKind::PseudoDestructor);
131     result.PseudoDestructorInfo.Expr = E;
132     return result;
133   }
134 
135   static CGCallee forDirect(llvm::Constant *functionPtr,
136                             const CGCalleeInfo &abstractInfo = CGCalleeInfo()) {
137     return CGCallee(abstractInfo, functionPtr);
138   }
139 
140   static CGCallee forDirect(llvm::FunctionCallee functionPtr,
141                             const CGCalleeInfo &abstractInfo = CGCalleeInfo()) {
142     return CGCallee(abstractInfo, functionPtr.getCallee());
143   }
144 
145   static CGCallee forVirtual(const CallExpr *CE, GlobalDecl MD, Address Addr,
146                              llvm::FunctionType *FTy) {
147     CGCallee result(SpecialKind::Virtual);
148     result.VirtualInfo.CE = CE;
149     result.VirtualInfo.MD = MD;
150     result.VirtualInfo.Addr = Addr;
151     result.VirtualInfo.FTy = FTy;
152     return result;
153   }
154 
155   bool isBuiltin() const {
156     return KindOrFunctionPointer == SpecialKind::Builtin;
157   }
158   const FunctionDecl *getBuiltinDecl() const {
159     assert(isBuiltin());
160     return BuiltinInfo.Decl;
161   }
162   unsigned getBuiltinID() const {
163     assert(isBuiltin());
164     return BuiltinInfo.ID;
165   }
166 
167   bool isPseudoDestructor() const {
168     return KindOrFunctionPointer == SpecialKind::PseudoDestructor;
169   }
170   const CXXPseudoDestructorExpr *getPseudoDestructorExpr() const {
171     assert(isPseudoDestructor());
172     return PseudoDestructorInfo.Expr;
173   }
174 
175   bool isOrdinary() const {
176     return uintptr_t(KindOrFunctionPointer) > uintptr_t(SpecialKind::Last);
177   }
178   CGCalleeInfo getAbstractInfo() const {
179     if (isVirtual())
180       return VirtualInfo.MD;
181     assert(isOrdinary());
182     return AbstractInfo;
183   }
184   llvm::Value *getFunctionPointer() const {
185     assert(isOrdinary());
186     return reinterpret_cast<llvm::Value *>(uintptr_t(KindOrFunctionPointer));
187   }
188   void setFunctionPointer(llvm::Value *functionPtr) {
189     assert(isOrdinary());
190     KindOrFunctionPointer =
191         SpecialKind(reinterpret_cast<uintptr_t>(functionPtr));
192   }
193 
194   bool isVirtual() const {
195     return KindOrFunctionPointer == SpecialKind::Virtual;
196   }
197   const CallExpr *getVirtualCallExpr() const {
198     assert(isVirtual());
199     return VirtualInfo.CE;
200   }
201   GlobalDecl getVirtualMethodDecl() const {
202     assert(isVirtual());
203     return VirtualInfo.MD;
204   }
205   Address getThisAddress() const {
206     assert(isVirtual());
207     return VirtualInfo.Addr;
208   }
209   llvm::FunctionType *getVirtualFunctionType() const {
210     assert(isVirtual());
211     return VirtualInfo.FTy;
212   }
213 
214   /// If this is a delayed callee computation of some sort, prepare
215   /// a concrete callee.
216   CGCallee prepareConcreteCallee(CodeGenFunction &CGF) const;
217 };
218 
219 struct CallArg {
220 private:
221   union {
222     RValue RV;
223     LValue LV; /// The argument is semantically a load from this l-value.
224   };
225   bool HasLV;
226 
227   /// A data-flow flag to make sure getRValue and/or copyInto are not
228   /// called twice for duplicated IR emission.
229   mutable bool IsUsed;
230 
231 public:
232   QualType Ty;
233   CallArg(RValue rv, QualType ty)
234       : RV(rv), HasLV(false), IsUsed(false), Ty(ty) {}
235   CallArg(LValue lv, QualType ty)
236       : LV(lv), HasLV(true), IsUsed(false), Ty(ty) {}
237   bool hasLValue() const { return HasLV; }
238   QualType getType() const { return Ty; }
239 
240   /// \returns an independent RValue. If the CallArg contains an LValue,
241   /// a temporary copy is returned.
242   RValue getRValue(CodeGenFunction &CGF) const;
243 
244   LValue getKnownLValue() const {
245     assert(HasLV && !IsUsed);
246     return LV;
247   }
248   RValue getKnownRValue() const {
249     assert(!HasLV && !IsUsed);
250     return RV;
251   }
252   void setRValue(RValue _RV) {
253     assert(!HasLV);
254     RV = _RV;
255   }
256 
257   bool isAggregate() const { return HasLV || RV.isAggregate(); }
258 
259   void copyInto(CodeGenFunction &CGF, Address A) const;
260 };
261 
262 /// CallArgList - Type for representing both the value and type of
263 /// arguments in a call.
264 class CallArgList : public SmallVector<CallArg, 8> {
265 public:
266   CallArgList() : StackBase(nullptr) {}
267 
268   struct Writeback {
269     /// The original argument.  Note that the argument l-value
270     /// is potentially null.
271     LValue Source;
272 
273     /// The temporary alloca.
274     Address Temporary;
275 
276     /// A value to "use" after the writeback, or null.
277     llvm::Value *ToUse;
278   };
279 
280   struct CallArgCleanup {
281     EHScopeStack::stable_iterator Cleanup;
282 
283     /// The "is active" insertion point.  This instruction is temporary and
284     /// will be removed after insertion.
285     llvm::Instruction *IsActiveIP;
286   };
287 
288   void add(RValue rvalue, QualType type) { push_back(CallArg(rvalue, type)); }
289 
290   void addUncopiedAggregate(LValue LV, QualType type) {
291     push_back(CallArg(LV, type));
292   }
293 
294   /// Add all the arguments from another CallArgList to this one. After doing
295   /// this, the old CallArgList retains its list of arguments, but must not
296   /// be used to emit a call.
297   void addFrom(const CallArgList &other) {
298     insert(end(), other.begin(), other.end());
299     Writebacks.insert(Writebacks.end(), other.Writebacks.begin(),
300                       other.Writebacks.end());
301     CleanupsToDeactivate.insert(CleanupsToDeactivate.end(),
302                                 other.CleanupsToDeactivate.begin(),
303                                 other.CleanupsToDeactivate.end());
304     assert(!(StackBase && other.StackBase) && "can't merge stackbases");
305     if (!StackBase)
306       StackBase = other.StackBase;
307   }
308 
309   void addWriteback(LValue srcLV, Address temporary, llvm::Value *toUse) {
310     Writeback writeback = {srcLV, temporary, toUse};
311     Writebacks.push_back(writeback);
312   }
313 
314   bool hasWritebacks() const { return !Writebacks.empty(); }
315 
316   typedef llvm::iterator_range<SmallVectorImpl<Writeback>::const_iterator>
317       writeback_const_range;
318 
319   writeback_const_range writebacks() const {
320     return writeback_const_range(Writebacks.begin(), Writebacks.end());
321   }
322 
323   void addArgCleanupDeactivation(EHScopeStack::stable_iterator Cleanup,
324                                  llvm::Instruction *IsActiveIP) {
325     CallArgCleanup ArgCleanup;
326     ArgCleanup.Cleanup = Cleanup;
327     ArgCleanup.IsActiveIP = IsActiveIP;
328     CleanupsToDeactivate.push_back(ArgCleanup);
329   }
330 
331   ArrayRef<CallArgCleanup> getCleanupsToDeactivate() const {
332     return CleanupsToDeactivate;
333   }
334 
335   void allocateArgumentMemory(CodeGenFunction &CGF);
336   llvm::Instruction *getStackBase() const { return StackBase; }
337   void freeArgumentMemory(CodeGenFunction &CGF) const;
338 
339   /// Returns if we're using an inalloca struct to pass arguments in
340   /// memory.
341   bool isUsingInAlloca() const { return StackBase; }
342 
343 private:
344   SmallVector<Writeback, 1> Writebacks;
345 
346   /// Deactivate these cleanups immediately before making the call.  This
347   /// is used to cleanup objects that are owned by the callee once the call
348   /// occurs.
349   SmallVector<CallArgCleanup, 1> CleanupsToDeactivate;
350 
351   /// The stacksave call.  It dominates all of the argument evaluation.
352   llvm::CallInst *StackBase;
353 };
354 
355 /// FunctionArgList - Type for representing both the decl and type
356 /// of parameters to a function. The decl must be either a
357 /// ParmVarDecl or ImplicitParamDecl.
358 class FunctionArgList : public SmallVector<const VarDecl *, 16> {};
359 
360 /// ReturnValueSlot - Contains the address where the return value of a
361 /// function can be stored, and whether the address is volatile or not.
362 class ReturnValueSlot {
363   Address Addr = Address::invalid();
364 
365   // Return value slot flags
366   unsigned IsVolatile : 1;
367   unsigned IsUnused : 1;
368   unsigned IsExternallyDestructed : 1;
369 
370 public:
371   ReturnValueSlot()
372       : IsVolatile(false), IsUnused(false), IsExternallyDestructed(false) {}
373   ReturnValueSlot(Address Addr, bool IsVolatile, bool IsUnused = false,
374                   bool IsExternallyDestructed = false)
375       : Addr(Addr), IsVolatile(IsVolatile), IsUnused(IsUnused),
376         IsExternallyDestructed(IsExternallyDestructed) {}
377 
378   bool isNull() const { return !Addr.isValid(); }
379   bool isVolatile() const { return IsVolatile; }
380   Address getValue() const { return Addr; }
381   bool isUnused() const { return IsUnused; }
382   bool isExternallyDestructed() const { return IsExternallyDestructed; }
383 };
384 
385 } // end namespace CodeGen
386 } // end namespace clang
387 
388 #endif
389