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/CanonicalType.h"
20 #include "clang/AST/GlobalDecl.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 AttributeList;
29 class Function;
30 class Type;
31 class Value;
32 } // namespace llvm
33 
34 namespace clang {
35 class ASTContext;
36 class Decl;
37 class FunctionDecl;
38 class ObjCMethodDecl;
39 class VarDecl;
40 
41 namespace CodeGen {
42 
43 /// Abstract information about a function or function prototype.
44 class CGCalleeInfo {
45   /// The function prototype of the callee.
46   const FunctionProtoType *CalleeProtoTy;
47   /// The function declaration of the callee.
48   GlobalDecl CalleeDecl;
49 
50 public:
51   explicit CGCalleeInfo() : CalleeProtoTy(nullptr), CalleeDecl() {}
52   CGCalleeInfo(const FunctionProtoType *calleeProtoTy, GlobalDecl calleeDecl)
53       : CalleeProtoTy(calleeProtoTy), CalleeDecl(calleeDecl) {}
54   CGCalleeInfo(const FunctionProtoType *calleeProtoTy)
55       : CalleeProtoTy(calleeProtoTy), CalleeDecl() {}
56   CGCalleeInfo(GlobalDecl calleeDecl)
57       : CalleeProtoTy(nullptr), CalleeDecl(calleeDecl) {}
58 
59   const FunctionProtoType *getCalleeFunctionProtoType() const {
60     return CalleeProtoTy;
61   }
62   const GlobalDecl getCalleeDecl() const { return CalleeDecl; }
63 };
64 
65 /// All available information about a concrete callee.
66 class CGCallee {
67   enum class SpecialKind : uintptr_t {
68     Invalid,
69     Builtin,
70     PseudoDestructor,
71     Virtual,
72 
73     Last = Virtual
74   };
75 
76   struct BuiltinInfoStorage {
77     const FunctionDecl *Decl;
78     unsigned ID;
79   };
80   struct PseudoDestructorInfoStorage {
81     const CXXPseudoDestructorExpr *Expr;
82   };
83   struct VirtualInfoStorage {
84     const CallExpr *CE;
85     GlobalDecl MD;
86     Address Addr;
87     llvm::FunctionType *FTy;
88   };
89 
90   SpecialKind KindOrFunctionPointer;
91   union {
92     CGCalleeInfo AbstractInfo;
93     BuiltinInfoStorage BuiltinInfo;
94     PseudoDestructorInfoStorage PseudoDestructorInfo;
95     VirtualInfoStorage VirtualInfo;
96   };
97 
98   explicit CGCallee(SpecialKind kind) : KindOrFunctionPointer(kind) {}
99 
100   CGCallee(const FunctionDecl *builtinDecl, unsigned builtinID)
101       : KindOrFunctionPointer(SpecialKind::Builtin) {
102     BuiltinInfo.Decl = builtinDecl;
103     BuiltinInfo.ID = builtinID;
104   }
105 
106 public:
107   CGCallee() : KindOrFunctionPointer(SpecialKind::Invalid) {}
108 
109   /// Construct a callee.  Call this constructor directly when this
110   /// isn't a direct call.
111   CGCallee(const CGCalleeInfo &abstractInfo, llvm::Value *functionPtr)
112       : KindOrFunctionPointer(SpecialKind(uintptr_t(functionPtr))) {
113     AbstractInfo = abstractInfo;
114     assert(functionPtr && "configuring callee without function pointer");
115     assert(functionPtr->getType()->isPointerTy());
116     assert(functionPtr->getType()->getPointerElementType()->isFunctionTy());
117   }
118 
119   static CGCallee forBuiltin(unsigned builtinID,
120                              const FunctionDecl *builtinDecl) {
121     CGCallee result(SpecialKind::Builtin);
122     result.BuiltinInfo.Decl = builtinDecl;
123     result.BuiltinInfo.ID = builtinID;
124     return result;
125   }
126 
127   static CGCallee forPseudoDestructor(const CXXPseudoDestructorExpr *E) {
128     CGCallee result(SpecialKind::PseudoDestructor);
129     result.PseudoDestructorInfo.Expr = E;
130     return result;
131   }
132 
133   static CGCallee forDirect(llvm::Constant *functionPtr,
134                             const CGCalleeInfo &abstractInfo = CGCalleeInfo()) {
135     return CGCallee(abstractInfo, functionPtr);
136   }
137 
138   static CGCallee forDirect(llvm::FunctionCallee functionPtr,
139                             const CGCalleeInfo &abstractInfo = CGCalleeInfo()) {
140     return CGCallee(abstractInfo, functionPtr.getCallee());
141   }
142 
143   static CGCallee forVirtual(const CallExpr *CE, GlobalDecl MD, Address Addr,
144                              llvm::FunctionType *FTy) {
145     CGCallee result(SpecialKind::Virtual);
146     result.VirtualInfo.CE = CE;
147     result.VirtualInfo.MD = MD;
148     result.VirtualInfo.Addr = Addr;
149     result.VirtualInfo.FTy = FTy;
150     return result;
151   }
152 
153   bool isBuiltin() const {
154     return KindOrFunctionPointer == SpecialKind::Builtin;
155   }
156   const FunctionDecl *getBuiltinDecl() const {
157     assert(isBuiltin());
158     return BuiltinInfo.Decl;
159   }
160   unsigned getBuiltinID() const {
161     assert(isBuiltin());
162     return BuiltinInfo.ID;
163   }
164 
165   bool isPseudoDestructor() const {
166     return KindOrFunctionPointer == SpecialKind::PseudoDestructor;
167   }
168   const CXXPseudoDestructorExpr *getPseudoDestructorExpr() const {
169     assert(isPseudoDestructor());
170     return PseudoDestructorInfo.Expr;
171   }
172 
173   bool isOrdinary() const {
174     return uintptr_t(KindOrFunctionPointer) > uintptr_t(SpecialKind::Last);
175   }
176   CGCalleeInfo getAbstractInfo() const {
177     if (isVirtual())
178       return VirtualInfo.MD;
179     assert(isOrdinary());
180     return AbstractInfo;
181   }
182   llvm::Value *getFunctionPointer() const {
183     assert(isOrdinary());
184     return reinterpret_cast<llvm::Value *>(uintptr_t(KindOrFunctionPointer));
185   }
186   void setFunctionPointer(llvm::Value *functionPtr) {
187     assert(isOrdinary());
188     KindOrFunctionPointer = SpecialKind(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   llvm::PointerIntPair<llvm::Value *, 2, unsigned int> Value;
361   CharUnits Alignment;
362 
363   // Return value slot flags
364   enum Flags {
365     IS_VOLATILE = 0x1,
366     IS_UNUSED = 0x2,
367   };
368 
369 public:
370   ReturnValueSlot() {}
371   ReturnValueSlot(Address Addr, bool IsVolatile, bool IsUnused = false)
372       : Value(Addr.isValid() ? Addr.getPointer() : nullptr,
373               (IsVolatile ? IS_VOLATILE : 0) | (IsUnused ? IS_UNUSED : 0)),
374         Alignment(Addr.isValid() ? Addr.getAlignment() : CharUnits::Zero()) {}
375 
376   bool isNull() const { return !getValue().isValid(); }
377 
378   bool isVolatile() const { return Value.getInt() & IS_VOLATILE; }
379   Address getValue() const { return Address(Value.getPointer(), Alignment); }
380   bool isUnused() const { return Value.getInt() & IS_UNUSED; }
381 };
382 
383 } // end namespace CodeGen
384 } // end namespace clang
385 
386 #endif
387