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 Type;
30 class Value;
31 } // namespace llvm
32 
33 namespace clang {
34 class Decl;
35 class FunctionDecl;
36 class VarDecl;
37 
38 namespace CodeGen {
39 
40 /// Abstract information about a function or function prototype.
41 class CGCalleeInfo {
42   /// The function prototype of the callee.
43   const FunctionProtoType *CalleeProtoTy;
44   /// The function declaration of the callee.
45   GlobalDecl CalleeDecl;
46 
47 public:
48   explicit CGCalleeInfo() : CalleeProtoTy(nullptr) {}
49   CGCalleeInfo(const FunctionProtoType *calleeProtoTy, GlobalDecl calleeDecl)
50       : CalleeProtoTy(calleeProtoTy), CalleeDecl(calleeDecl) {}
51   CGCalleeInfo(const FunctionProtoType *calleeProtoTy)
52       : CalleeProtoTy(calleeProtoTy) {}
53   CGCalleeInfo(GlobalDecl calleeDecl)
54       : CalleeProtoTy(nullptr), CalleeDecl(calleeDecl) {}
55 
56   const FunctionProtoType *getCalleeFunctionProtoType() const {
57     return CalleeProtoTy;
58   }
59   const GlobalDecl getCalleeDecl() const { return CalleeDecl; }
60 };
61 
62 /// All available information about a concrete callee.
63 class CGCallee {
64   enum class SpecialKind : uintptr_t {
65     Invalid,
66     Builtin,
67     PseudoDestructor,
68     Virtual,
69 
70     Last = Virtual
71   };
72 
73   struct BuiltinInfoStorage {
74     const FunctionDecl *Decl;
75     unsigned ID;
76   };
77   struct PseudoDestructorInfoStorage {
78     const CXXPseudoDestructorExpr *Expr;
79   };
80   struct VirtualInfoStorage {
81     const CallExpr *CE;
82     GlobalDecl MD;
83     Address Addr;
84     llvm::FunctionType *FTy;
85   };
86 
87   SpecialKind KindOrFunctionPointer;
88   union {
89     CGCalleeInfo AbstractInfo;
90     BuiltinInfoStorage BuiltinInfo;
91     PseudoDestructorInfoStorage PseudoDestructorInfo;
92     VirtualInfoStorage VirtualInfo;
93   };
94 
95   explicit CGCallee(SpecialKind kind) : KindOrFunctionPointer(kind) {}
96 
97   CGCallee(const FunctionDecl *builtinDecl, unsigned builtinID)
98       : KindOrFunctionPointer(SpecialKind::Builtin) {
99     BuiltinInfo.Decl = builtinDecl;
100     BuiltinInfo.ID = builtinID;
101   }
102 
103 public:
104   CGCallee() : KindOrFunctionPointer(SpecialKind::Invalid) {}
105 
106   /// Construct a callee.  Call this constructor directly when this
107   /// isn't a direct call.
108   CGCallee(const CGCalleeInfo &abstractInfo, llvm::Value *functionPtr)
109       : KindOrFunctionPointer(
110             SpecialKind(reinterpret_cast<uintptr_t>(functionPtr))) {
111     AbstractInfo = abstractInfo;
112     assert(functionPtr && "configuring callee without function pointer");
113     assert(functionPtr->getType()->isPointerTy());
114     assert(functionPtr->getType()->isOpaquePointerTy() ||
115            functionPtr->getType()->getPointerElementType()->isFunctionTy());
116   }
117 
118   static CGCallee forBuiltin(unsigned builtinID,
119                              const FunctionDecl *builtinDecl) {
120     CGCallee result(SpecialKind::Builtin);
121     result.BuiltinInfo.Decl = builtinDecl;
122     result.BuiltinInfo.ID = builtinID;
123     return result;
124   }
125 
126   static CGCallee forPseudoDestructor(const CXXPseudoDestructorExpr *E) {
127     CGCallee result(SpecialKind::PseudoDestructor);
128     result.PseudoDestructorInfo.Expr = E;
129     return result;
130   }
131 
132   static CGCallee forDirect(llvm::Constant *functionPtr,
133                             const CGCalleeInfo &abstractInfo = CGCalleeInfo()) {
134     return CGCallee(abstractInfo, functionPtr);
135   }
136 
137   static CGCallee forDirect(llvm::FunctionCallee functionPtr,
138                             const CGCalleeInfo &abstractInfo = CGCalleeInfo()) {
139     return CGCallee(abstractInfo, functionPtr.getCallee());
140   }
141 
142   static CGCallee forVirtual(const CallExpr *CE, GlobalDecl MD, Address Addr,
143                              llvm::FunctionType *FTy) {
144     CGCallee result(SpecialKind::Virtual);
145     result.VirtualInfo.CE = CE;
146     result.VirtualInfo.MD = MD;
147     result.VirtualInfo.Addr = Addr;
148     result.VirtualInfo.FTy = FTy;
149     return result;
150   }
151 
152   bool isBuiltin() const {
153     return KindOrFunctionPointer == SpecialKind::Builtin;
154   }
155   const FunctionDecl *getBuiltinDecl() const {
156     assert(isBuiltin());
157     return BuiltinInfo.Decl;
158   }
159   unsigned getBuiltinID() const {
160     assert(isBuiltin());
161     return BuiltinInfo.ID;
162   }
163 
164   bool isPseudoDestructor() const {
165     return KindOrFunctionPointer == SpecialKind::PseudoDestructor;
166   }
167   const CXXPseudoDestructorExpr *getPseudoDestructorExpr() const {
168     assert(isPseudoDestructor());
169     return PseudoDestructorInfo.Expr;
170   }
171 
172   bool isOrdinary() const {
173     return uintptr_t(KindOrFunctionPointer) > uintptr_t(SpecialKind::Last);
174   }
175   CGCalleeInfo getAbstractInfo() const {
176     if (isVirtual())
177       return VirtualInfo.MD;
178     assert(isOrdinary());
179     return AbstractInfo;
180   }
181   llvm::Value *getFunctionPointer() const {
182     assert(isOrdinary());
183     return reinterpret_cast<llvm::Value *>(uintptr_t(KindOrFunctionPointer));
184   }
185   void setFunctionPointer(llvm::Value *functionPtr) {
186     assert(isOrdinary());
187     KindOrFunctionPointer =
188         SpecialKind(reinterpret_cast<uintptr_t>(functionPtr));
189   }
190 
191   bool isVirtual() const {
192     return KindOrFunctionPointer == SpecialKind::Virtual;
193   }
194   const CallExpr *getVirtualCallExpr() const {
195     assert(isVirtual());
196     return VirtualInfo.CE;
197   }
198   GlobalDecl getVirtualMethodDecl() const {
199     assert(isVirtual());
200     return VirtualInfo.MD;
201   }
202   Address getThisAddress() const {
203     assert(isVirtual());
204     return VirtualInfo.Addr;
205   }
206   llvm::FunctionType *getVirtualFunctionType() const {
207     assert(isVirtual());
208     return VirtualInfo.FTy;
209   }
210 
211   /// If this is a delayed callee computation of some sort, prepare
212   /// a concrete callee.
213   CGCallee prepareConcreteCallee(CodeGenFunction &CGF) const;
214 };
215 
216 struct CallArg {
217 private:
218   union {
219     RValue RV;
220     LValue LV; /// The argument is semantically a load from this l-value.
221   };
222   bool HasLV;
223 
224   /// A data-flow flag to make sure getRValue and/or copyInto are not
225   /// called twice for duplicated IR emission.
226   mutable bool IsUsed;
227 
228 public:
229   QualType Ty;
230   CallArg(RValue rv, QualType ty)
231       : RV(rv), HasLV(false), IsUsed(false), Ty(ty) {}
232   CallArg(LValue lv, QualType ty)
233       : LV(lv), HasLV(true), IsUsed(false), Ty(ty) {}
234   bool hasLValue() const { return HasLV; }
235   QualType getType() const { return Ty; }
236 
237   /// \returns an independent RValue. If the CallArg contains an LValue,
238   /// a temporary copy is returned.
239   RValue getRValue(CodeGenFunction &CGF) const;
240 
241   LValue getKnownLValue() const {
242     assert(HasLV && !IsUsed);
243     return LV;
244   }
245   RValue getKnownRValue() const {
246     assert(!HasLV && !IsUsed);
247     return RV;
248   }
249   void setRValue(RValue _RV) {
250     assert(!HasLV);
251     RV = _RV;
252   }
253 
254   bool isAggregate() const { return HasLV || RV.isAggregate(); }
255 
256   void copyInto(CodeGenFunction &CGF, Address A) const;
257 };
258 
259 /// CallArgList - Type for representing both the value and type of
260 /// arguments in a call.
261 class CallArgList : public SmallVector<CallArg, 8> {
262 public:
263   CallArgList() : StackBase(nullptr) {}
264 
265   struct Writeback {
266     /// The original argument.  Note that the argument l-value
267     /// is potentially null.
268     LValue Source;
269 
270     /// The temporary alloca.
271     Address Temporary;
272 
273     /// A value to "use" after the writeback, or null.
274     llvm::Value *ToUse;
275   };
276 
277   struct CallArgCleanup {
278     EHScopeStack::stable_iterator Cleanup;
279 
280     /// The "is active" insertion point.  This instruction is temporary and
281     /// will be removed after insertion.
282     llvm::Instruction *IsActiveIP;
283   };
284 
285   void add(RValue rvalue, QualType type) { push_back(CallArg(rvalue, type)); }
286 
287   void addUncopiedAggregate(LValue LV, QualType type) {
288     push_back(CallArg(LV, type));
289   }
290 
291   /// Add all the arguments from another CallArgList to this one. After doing
292   /// this, the old CallArgList retains its list of arguments, but must not
293   /// be used to emit a call.
294   void addFrom(const CallArgList &other) {
295     insert(end(), other.begin(), other.end());
296     Writebacks.insert(Writebacks.end(), other.Writebacks.begin(),
297                       other.Writebacks.end());
298     CleanupsToDeactivate.insert(CleanupsToDeactivate.end(),
299                                 other.CleanupsToDeactivate.begin(),
300                                 other.CleanupsToDeactivate.end());
301     assert(!(StackBase && other.StackBase) && "can't merge stackbases");
302     if (!StackBase)
303       StackBase = other.StackBase;
304   }
305 
306   void addWriteback(LValue srcLV, Address temporary, llvm::Value *toUse) {
307     Writeback writeback = {srcLV, temporary, toUse};
308     Writebacks.push_back(writeback);
309   }
310 
311   bool hasWritebacks() const { return !Writebacks.empty(); }
312 
313   typedef llvm::iterator_range<SmallVectorImpl<Writeback>::const_iterator>
314       writeback_const_range;
315 
316   writeback_const_range writebacks() const {
317     return writeback_const_range(Writebacks.begin(), Writebacks.end());
318   }
319 
320   void addArgCleanupDeactivation(EHScopeStack::stable_iterator Cleanup,
321                                  llvm::Instruction *IsActiveIP) {
322     CallArgCleanup ArgCleanup;
323     ArgCleanup.Cleanup = Cleanup;
324     ArgCleanup.IsActiveIP = IsActiveIP;
325     CleanupsToDeactivate.push_back(ArgCleanup);
326   }
327 
328   ArrayRef<CallArgCleanup> getCleanupsToDeactivate() const {
329     return CleanupsToDeactivate;
330   }
331 
332   void allocateArgumentMemory(CodeGenFunction &CGF);
333   llvm::Instruction *getStackBase() const { return StackBase; }
334   void freeArgumentMemory(CodeGenFunction &CGF) const;
335 
336   /// Returns if we're using an inalloca struct to pass arguments in
337   /// memory.
338   bool isUsingInAlloca() const { return StackBase; }
339 
340 private:
341   SmallVector<Writeback, 1> Writebacks;
342 
343   /// Deactivate these cleanups immediately before making the call.  This
344   /// is used to cleanup objects that are owned by the callee once the call
345   /// occurs.
346   SmallVector<CallArgCleanup, 1> CleanupsToDeactivate;
347 
348   /// The stacksave call.  It dominates all of the argument evaluation.
349   llvm::CallInst *StackBase;
350 };
351 
352 /// FunctionArgList - Type for representing both the decl and type
353 /// of parameters to a function. The decl must be either a
354 /// ParmVarDecl or ImplicitParamDecl.
355 class FunctionArgList : public SmallVector<const VarDecl *, 16> {};
356 
357 /// ReturnValueSlot - Contains the address where the return value of a
358 /// function can be stored, and whether the address is volatile or not.
359 class ReturnValueSlot {
360   Address Addr = Address::invalid();
361 
362   // Return value slot flags
363   unsigned IsVolatile : 1;
364   unsigned IsUnused : 1;
365   unsigned IsExternallyDestructed : 1;
366 
367 public:
368   ReturnValueSlot()
369       : IsVolatile(false), IsUnused(false), IsExternallyDestructed(false) {}
370   ReturnValueSlot(Address Addr, bool IsVolatile, bool IsUnused = false,
371                   bool IsExternallyDestructed = false)
372       : Addr(Addr), IsVolatile(IsVolatile), IsUnused(IsUnused),
373         IsExternallyDestructed(IsExternallyDestructed) {}
374 
375   bool isNull() const { return !Addr.isValid(); }
376   bool isVolatile() const { return IsVolatile; }
377   Address getValue() const { return Addr; }
378   bool isUnused() const { return IsUnused; }
379   bool isExternallyDestructed() const { return IsExternallyDestructed; }
380 };
381 
382 } // end namespace CodeGen
383 } // end namespace clang
384 
385 #endif
386