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(SpecialKind(uintptr_t(functionPtr))) {
114     AbstractInfo = abstractInfo;
115     assert(functionPtr && "configuring callee without function pointer");
116     assert(functionPtr->getType()->isPointerTy());
117     assert(functionPtr->getType()->getPointerElementType()->isFunctionTy());
118   }
119 
120   static CGCallee forBuiltin(unsigned builtinID,
121                              const FunctionDecl *builtinDecl) {
122     CGCallee result(SpecialKind::Builtin);
123     result.BuiltinInfo.Decl = builtinDecl;
124     result.BuiltinInfo.ID = builtinID;
125     return result;
126   }
127 
128   static CGCallee forPseudoDestructor(const CXXPseudoDestructorExpr *E) {
129     CGCallee result(SpecialKind::PseudoDestructor);
130     result.PseudoDestructorInfo.Expr = E;
131     return result;
132   }
133 
134   static CGCallee forDirect(llvm::Constant *functionPtr,
135                             const CGCalleeInfo &abstractInfo = CGCalleeInfo()) {
136     return CGCallee(abstractInfo, functionPtr);
137   }
138 
139   static CGCallee forDirect(llvm::FunctionCallee functionPtr,
140                             const CGCalleeInfo &abstractInfo = CGCalleeInfo()) {
141     return CGCallee(abstractInfo, functionPtr.getCallee());
142   }
143 
144   static CGCallee forVirtual(const CallExpr *CE, GlobalDecl MD, Address Addr,
145                              llvm::FunctionType *FTy) {
146     CGCallee result(SpecialKind::Virtual);
147     result.VirtualInfo.CE = CE;
148     result.VirtualInfo.MD = MD;
149     result.VirtualInfo.Addr = Addr;
150     result.VirtualInfo.FTy = FTy;
151     return result;
152   }
153 
154   bool isBuiltin() const {
155     return KindOrFunctionPointer == SpecialKind::Builtin;
156   }
157   const FunctionDecl *getBuiltinDecl() const {
158     assert(isBuiltin());
159     return BuiltinInfo.Decl;
160   }
161   unsigned getBuiltinID() const {
162     assert(isBuiltin());
163     return BuiltinInfo.ID;
164   }
165 
166   bool isPseudoDestructor() const {
167     return KindOrFunctionPointer == SpecialKind::PseudoDestructor;
168   }
169   const CXXPseudoDestructorExpr *getPseudoDestructorExpr() const {
170     assert(isPseudoDestructor());
171     return PseudoDestructorInfo.Expr;
172   }
173 
174   bool isOrdinary() const {
175     return uintptr_t(KindOrFunctionPointer) > uintptr_t(SpecialKind::Last);
176   }
177   CGCalleeInfo getAbstractInfo() const {
178     if (isVirtual())
179       return VirtualInfo.MD;
180     assert(isOrdinary());
181     return AbstractInfo;
182   }
183   llvm::Value *getFunctionPointer() const {
184     assert(isOrdinary());
185     return reinterpret_cast<llvm::Value *>(uintptr_t(KindOrFunctionPointer));
186   }
187   void setFunctionPointer(llvm::Value *functionPtr) {
188     assert(isOrdinary());
189     KindOrFunctionPointer = SpecialKind(uintptr_t(functionPtr));
190   }
191 
192   bool isVirtual() const {
193     return KindOrFunctionPointer == SpecialKind::Virtual;
194   }
195   const CallExpr *getVirtualCallExpr() const {
196     assert(isVirtual());
197     return VirtualInfo.CE;
198   }
199   GlobalDecl getVirtualMethodDecl() const {
200     assert(isVirtual());
201     return VirtualInfo.MD;
202   }
203   Address getThisAddress() const {
204     assert(isVirtual());
205     return VirtualInfo.Addr;
206   }
207   llvm::FunctionType *getVirtualFunctionType() const {
208     assert(isVirtual());
209     return VirtualInfo.FTy;
210   }
211 
212   /// If this is a delayed callee computation of some sort, prepare
213   /// a concrete callee.
214   CGCallee prepareConcreteCallee(CodeGenFunction &CGF) const;
215 };
216 
217 struct CallArg {
218 private:
219   union {
220     RValue RV;
221     LValue LV; /// The argument is semantically a load from this l-value.
222   };
223   bool HasLV;
224 
225   /// A data-flow flag to make sure getRValue and/or copyInto are not
226   /// called twice for duplicated IR emission.
227   mutable bool IsUsed;
228 
229 public:
230   QualType Ty;
231   CallArg(RValue rv, QualType ty)
232       : RV(rv), HasLV(false), IsUsed(false), Ty(ty) {}
233   CallArg(LValue lv, QualType ty)
234       : LV(lv), HasLV(true), IsUsed(false), Ty(ty) {}
235   bool hasLValue() const { return HasLV; }
236   QualType getType() const { return Ty; }
237 
238   /// \returns an independent RValue. If the CallArg contains an LValue,
239   /// a temporary copy is returned.
240   RValue getRValue(CodeGenFunction &CGF) const;
241 
242   LValue getKnownLValue() const {
243     assert(HasLV && !IsUsed);
244     return LV;
245   }
246   RValue getKnownRValue() const {
247     assert(!HasLV && !IsUsed);
248     return RV;
249   }
250   void setRValue(RValue _RV) {
251     assert(!HasLV);
252     RV = _RV;
253   }
254 
255   bool isAggregate() const { return HasLV || RV.isAggregate(); }
256 
257   void copyInto(CodeGenFunction &CGF, Address A) const;
258 };
259 
260 /// CallArgList - Type for representing both the value and type of
261 /// arguments in a call.
262 class CallArgList : public SmallVector<CallArg, 8> {
263 public:
264   CallArgList() : StackBase(nullptr) {}
265 
266   struct Writeback {
267     /// The original argument.  Note that the argument l-value
268     /// is potentially null.
269     LValue Source;
270 
271     /// The temporary alloca.
272     Address Temporary;
273 
274     /// A value to "use" after the writeback, or null.
275     llvm::Value *ToUse;
276   };
277 
278   struct CallArgCleanup {
279     EHScopeStack::stable_iterator Cleanup;
280 
281     /// The "is active" insertion point.  This instruction is temporary and
282     /// will be removed after insertion.
283     llvm::Instruction *IsActiveIP;
284   };
285 
286   struct EndLifetimeInfo {
287     llvm::Value *Addr;
288     llvm::Value *Size;
289   };
290 
291   void add(RValue rvalue, QualType type) { push_back(CallArg(rvalue, type)); }
292 
293   void addUncopiedAggregate(LValue LV, QualType type) {
294     push_back(CallArg(LV, type));
295   }
296 
297   /// Add all the arguments from another CallArgList to this one. After doing
298   /// this, the old CallArgList retains its list of arguments, but must not
299   /// be used to emit a call.
300   void addFrom(const CallArgList &other) {
301     insert(end(), other.begin(), other.end());
302     Writebacks.insert(Writebacks.end(), other.Writebacks.begin(),
303                       other.Writebacks.end());
304     CleanupsToDeactivate.insert(CleanupsToDeactivate.end(),
305                                 other.CleanupsToDeactivate.begin(),
306                                 other.CleanupsToDeactivate.end());
307     LifetimeCleanups.insert(LifetimeCleanups.end(),
308                             other.LifetimeCleanups.begin(),
309                             other.LifetimeCleanups.end());
310     assert(!(StackBase && other.StackBase) && "can't merge stackbases");
311     if (!StackBase)
312       StackBase = other.StackBase;
313   }
314 
315   void addWriteback(LValue srcLV, Address temporary, llvm::Value *toUse) {
316     Writeback writeback = {srcLV, temporary, toUse};
317     Writebacks.push_back(writeback);
318   }
319 
320   bool hasWritebacks() const { return !Writebacks.empty(); }
321 
322   typedef llvm::iterator_range<SmallVectorImpl<Writeback>::const_iterator>
323       writeback_const_range;
324 
325   writeback_const_range writebacks() const {
326     return writeback_const_range(Writebacks.begin(), Writebacks.end());
327   }
328 
329   void addArgCleanupDeactivation(EHScopeStack::stable_iterator Cleanup,
330                                  llvm::Instruction *IsActiveIP) {
331     CallArgCleanup ArgCleanup;
332     ArgCleanup.Cleanup = Cleanup;
333     ArgCleanup.IsActiveIP = IsActiveIP;
334     CleanupsToDeactivate.push_back(ArgCleanup);
335   }
336 
337   ArrayRef<CallArgCleanup> getCleanupsToDeactivate() const {
338     return CleanupsToDeactivate;
339   }
340 
341   void allocateArgumentMemory(CodeGenFunction &CGF);
342   llvm::Instruction *getStackBase() const { return StackBase; }
343   void freeArgumentMemory(CodeGenFunction &CGF) const;
344 
345   /// Returns if we're using an inalloca struct to pass arguments in
346   /// memory.
347   bool isUsingInAlloca() const { return StackBase; }
348 
349   void addLifetimeCleanup(EndLifetimeInfo Info) {
350     LifetimeCleanups.push_back(Info);
351   }
352 
353   ArrayRef<EndLifetimeInfo> getLifetimeCleanups() const {
354     return LifetimeCleanups;
355   }
356 
357 private:
358   SmallVector<Writeback, 1> Writebacks;
359 
360   /// Deactivate these cleanups immediately before making the call.  This
361   /// is used to cleanup objects that are owned by the callee once the call
362   /// occurs.
363   SmallVector<CallArgCleanup, 1> CleanupsToDeactivate;
364 
365   /// Lifetime information needed to call llvm.lifetime.end for any temporary
366   /// argument allocas.
367   SmallVector<EndLifetimeInfo, 2> LifetimeCleanups;
368 
369   /// The stacksave call.  It dominates all of the argument evaluation.
370   llvm::CallInst *StackBase;
371 };
372 
373 /// FunctionArgList - Type for representing both the decl and type
374 /// of parameters to a function. The decl must be either a
375 /// ParmVarDecl or ImplicitParamDecl.
376 class FunctionArgList : public SmallVector<const VarDecl *, 16> {};
377 
378 /// ReturnValueSlot - Contains the address where the return value of a
379 /// function can be stored, and whether the address is volatile or not.
380 class ReturnValueSlot {
381   llvm::PointerIntPair<llvm::Value *, 2, unsigned int> Value;
382   CharUnits Alignment;
383 
384   // Return value slot flags
385   enum Flags {
386     IS_VOLATILE = 0x1,
387     IS_UNUSED = 0x2,
388   };
389 
390 public:
391   ReturnValueSlot() {}
392   ReturnValueSlot(Address Addr, bool IsVolatile, bool IsUnused = false)
393       : Value(Addr.isValid() ? Addr.getPointer() : nullptr,
394               (IsVolatile ? IS_VOLATILE : 0) | (IsUnused ? IS_UNUSED : 0)),
395         Alignment(Addr.isValid() ? Addr.getAlignment() : CharUnits::Zero()) {}
396 
397   bool isNull() const { return !getValue().isValid(); }
398 
399   bool isVolatile() const { return Value.getInt() & IS_VOLATILE; }
400   Address getValue() const { return Address(Value.getPointer(), Alignment); }
401   bool isUnused() const { return Value.getInt() & IS_UNUSED; }
402 };
403 
404 } // end namespace CodeGen
405 } // end namespace clang
406 
407 #endif
408