1 //===---- TargetInfo.h - Encapsulate target 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 LLVM_CLANG_LIB_CODEGEN_TARGETINFO_H
16 #define LLVM_CLANG_LIB_CODEGEN_TARGETINFO_H
17 
18 #include "CodeGenModule.h"
19 #include "CGValue.h"
20 #include "clang/AST/Type.h"
21 #include "clang/Basic/LLVM.h"
22 #include "clang/Basic/SyncScope.h"
23 #include "llvm/ADT/SmallString.h"
24 #include "llvm/ADT/StringRef.h"
25 
26 namespace llvm {
27 class Constant;
28 class GlobalValue;
29 class Type;
30 class Value;
31 }
32 
33 namespace clang {
34 class Decl;
35 
36 namespace CodeGen {
37 class ABIInfo;
38 class CallArgList;
39 class CodeGenFunction;
40 class CGBlockInfo;
41 class CGFunctionInfo;
42 
43 /// TargetCodeGenInfo - This class organizes various target-specific
44 /// codegeneration issues, like target-specific attributes, builtins and so
45 /// on.
46 class TargetCodeGenInfo {
47   ABIInfo *Info;
48 
49 public:
50   // WARNING: Acquires the ownership of ABIInfo.
51   TargetCodeGenInfo(ABIInfo *info = nullptr) : Info(info) {}
52   virtual ~TargetCodeGenInfo();
53 
54   /// getABIInfo() - Returns ABI info helper for the target.
55   const ABIInfo &getABIInfo() const { return *Info; }
56 
57   /// setTargetAttributes - Provides a convenient hook to handle extra
58   /// target-specific attributes for the given global.
59   virtual void setTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
60                                    CodeGen::CodeGenModule &M,
61                                    ForDefinition_t IsForDefinition) const {}
62 
63   /// emitTargetMD - Provides a convenient hook to handle extra
64   /// target-specific metadata for the given global.
65   virtual void emitTargetMD(const Decl *D, llvm::GlobalValue *GV,
66                             CodeGen::CodeGenModule &M) const {}
67 
68   /// Determines the size of struct _Unwind_Exception on this platform,
69   /// in 8-bit units.  The Itanium ABI defines this as:
70   ///   struct _Unwind_Exception {
71   ///     uint64 exception_class;
72   ///     _Unwind_Exception_Cleanup_Fn exception_cleanup;
73   ///     uint64 private_1;
74   ///     uint64 private_2;
75   ///   };
76   virtual unsigned getSizeOfUnwindException() const;
77 
78   /// Controls whether __builtin_extend_pointer should sign-extend
79   /// pointers to uint64_t or zero-extend them (the default).  Has
80   /// no effect for targets:
81   ///   - that have 64-bit pointers, or
82   ///   - that cannot address through registers larger than pointers, or
83   ///   - that implicitly ignore/truncate the top bits when addressing
84   ///     through such registers.
85   virtual bool extendPointerWithSExt() const { return false; }
86 
87   /// Determines the DWARF register number for the stack pointer, for
88   /// exception-handling purposes.  Implements __builtin_dwarf_sp_column.
89   ///
90   /// Returns -1 if the operation is unsupported by this target.
91   virtual int getDwarfEHStackPointer(CodeGen::CodeGenModule &M) const {
92     return -1;
93   }
94 
95   /// Initializes the given DWARF EH register-size table, a char*.
96   /// Implements __builtin_init_dwarf_reg_size_table.
97   ///
98   /// Returns true if the operation is unsupported by this target.
99   virtual bool initDwarfEHRegSizeTable(CodeGen::CodeGenFunction &CGF,
100                                        llvm::Value *Address) const {
101     return true;
102   }
103 
104   /// Performs the code-generation required to convert a return
105   /// address as stored by the system into the actual address of the
106   /// next instruction that will be executed.
107   ///
108   /// Used by __builtin_extract_return_addr().
109   virtual llvm::Value *decodeReturnAddress(CodeGen::CodeGenFunction &CGF,
110                                            llvm::Value *Address) const {
111     return Address;
112   }
113 
114   /// Performs the code-generation required to convert the address
115   /// of an instruction into a return address suitable for storage
116   /// by the system in a return slot.
117   ///
118   /// Used by __builtin_frob_return_addr().
119   virtual llvm::Value *encodeReturnAddress(CodeGen::CodeGenFunction &CGF,
120                                            llvm::Value *Address) const {
121     return Address;
122   }
123 
124   /// Corrects the low-level LLVM type for a given constraint and "usual"
125   /// type.
126   ///
127   /// \returns A pointer to a new LLVM type, possibly the same as the original
128   /// on success; 0 on failure.
129   virtual llvm::Type *adjustInlineAsmType(CodeGen::CodeGenFunction &CGF,
130                                           StringRef Constraint,
131                                           llvm::Type *Ty) const {
132     return Ty;
133   }
134 
135   /// Adds constraints and types for result registers.
136   virtual void addReturnRegisterOutputs(
137       CodeGen::CodeGenFunction &CGF, CodeGen::LValue ReturnValue,
138       std::string &Constraints, std::vector<llvm::Type *> &ResultRegTypes,
139       std::vector<llvm::Type *> &ResultTruncRegTypes,
140       std::vector<CodeGen::LValue> &ResultRegDests, std::string &AsmString,
141       unsigned NumOutputs) const {}
142 
143   /// doesReturnSlotInterfereWithArgs - Return true if the target uses an
144   /// argument slot for an 'sret' type.
145   virtual bool doesReturnSlotInterfereWithArgs() const { return true; }
146 
147   /// Retrieve the address of a function to call immediately before
148   /// calling objc_retainAutoreleasedReturnValue.  The
149   /// implementation of objc_autoreleaseReturnValue sniffs the
150   /// instruction stream following its return address to decide
151   /// whether it's a call to objc_retainAutoreleasedReturnValue.
152   /// This can be prohibitively expensive, depending on the
153   /// relocation model, and so on some targets it instead sniffs for
154   /// a particular instruction sequence.  This functions returns
155   /// that instruction sequence in inline assembly, which will be
156   /// empty if none is required.
157   virtual StringRef getARCRetainAutoreleasedReturnValueMarker() const {
158     return "";
159   }
160 
161   /// Return a constant used by UBSan as a signature to identify functions
162   /// possessing type information, or 0 if the platform is unsupported.
163   virtual llvm::Constant *
164   getUBSanFunctionSignature(CodeGen::CodeGenModule &CGM) const {
165     return nullptr;
166   }
167 
168   /// Determine whether a call to an unprototyped functions under
169   /// the given calling convention should use the variadic
170   /// convention or the non-variadic convention.
171   ///
172   /// There's a good reason to make a platform's variadic calling
173   /// convention be different from its non-variadic calling
174   /// convention: the non-variadic arguments can be passed in
175   /// registers (better for performance), and the variadic arguments
176   /// can be passed on the stack (also better for performance).  If
177   /// this is done, however, unprototyped functions *must* use the
178   /// non-variadic convention, because C99 states that a call
179   /// through an unprototyped function type must succeed if the
180   /// function was defined with a non-variadic prototype with
181   /// compatible parameters.  Therefore, splitting the conventions
182   /// makes it impossible to call a variadic function through an
183   /// unprototyped type.  Since function prototypes came out in the
184   /// late 1970s, this is probably an acceptable trade-off.
185   /// Nonetheless, not all platforms are willing to make it, and in
186   /// particularly x86-64 bends over backwards to make the
187   /// conventions compatible.
188   ///
189   /// The default is false.  This is correct whenever:
190   ///   - the conventions are exactly the same, because it does not
191   ///     matter and the resulting IR will be somewhat prettier in
192   ///     certain cases; or
193   ///   - the conventions are substantively different in how they pass
194   ///     arguments, because in this case using the variadic convention
195   ///     will lead to C99 violations.
196   ///
197   /// However, some platforms make the conventions identical except
198   /// for passing additional out-of-band information to a variadic
199   /// function: for example, x86-64 passes the number of SSE
200   /// arguments in %al.  On these platforms, it is desirable to
201   /// call unprototyped functions using the variadic convention so
202   /// that unprototyped calls to varargs functions still succeed.
203   ///
204   /// Relatedly, platforms which pass the fixed arguments to this:
205   ///   A foo(B, C, D);
206   /// differently than they would pass them to this:
207   ///   A foo(B, C, D, ...);
208   /// may need to adjust the debugger-support code in Sema to do the
209   /// right thing when calling a function with no know signature.
210   virtual bool isNoProtoCallVariadic(const CodeGen::CallArgList &args,
211                                      const FunctionNoProtoType *fnType) const;
212 
213   /// Gets the linker options necessary to link a dependent library on this
214   /// platform.
215   virtual void getDependentLibraryOption(llvm::StringRef Lib,
216                                          llvm::SmallString<24> &Opt) const;
217 
218   /// Gets the linker options necessary to detect object file mismatches on
219   /// this platform.
220   virtual void getDetectMismatchOption(llvm::StringRef Name,
221                                        llvm::StringRef Value,
222                                        llvm::SmallString<32> &Opt) const {}
223 
224   /// Get LLVM calling convention for OpenCL kernel.
225   virtual unsigned getOpenCLKernelCallingConv() const;
226 
227   /// Get target specific null pointer.
228   /// \param T is the LLVM type of the null pointer.
229   /// \param QT is the clang QualType of the null pointer.
230   /// \return ConstantPointerNull with the given type \p T.
231   /// Each target can override it to return its own desired constant value.
232   virtual llvm::Constant *getNullPointer(const CodeGen::CodeGenModule &CGM,
233       llvm::PointerType *T, QualType QT) const;
234 
235   /// Get target favored AST address space of a global variable for languages
236   /// other than OpenCL and CUDA.
237   /// If \p D is nullptr, returns the default target favored address space
238   /// for global variable.
239   virtual unsigned getGlobalVarAddressSpace(CodeGenModule &CGM,
240                                             const VarDecl *D) const;
241 
242   /// Get the AST address space for alloca.
243   virtual unsigned getASTAllocaAddressSpace() const { return LangAS::Default; }
244 
245   /// Perform address space cast of an expression of pointer type.
246   /// \param V is the LLVM value to be casted to another address space.
247   /// \param SrcAddr is the language address space of \p V.
248   /// \param DestAddr is the targeted language address space.
249   /// \param DestTy is the destination LLVM pointer type.
250   /// \param IsNonNull is the flag indicating \p V is known to be non null.
251   virtual llvm::Value *performAddrSpaceCast(CodeGen::CodeGenFunction &CGF,
252                                             llvm::Value *V, unsigned SrcAddr,
253                                             unsigned DestAddr,
254                                             llvm::Type *DestTy,
255                                             bool IsNonNull = false) const;
256 
257   /// Perform address space cast of a constant expression of pointer type.
258   /// \param V is the LLVM constant to be casted to another address space.
259   /// \param SrcAddr is the language address space of \p V.
260   /// \param DestAddr is the targeted language address space.
261   /// \param DestTy is the destination LLVM pointer type.
262   virtual llvm::Constant *
263   performAddrSpaceCast(CodeGenModule &CGM, llvm::Constant *V, unsigned SrcAddr,
264                        unsigned DestAddr, llvm::Type *DestTy) const;
265 
266   /// Get the syncscope used in LLVM IR.
267   virtual llvm::SyncScope::ID getLLVMSyncScopeID(SyncScope S,
268                                                  llvm::LLVMContext &C) const;
269 
270   /// Inteface class for filling custom fields of a block literal for OpenCL.
271   class TargetOpenCLBlockHelper {
272   public:
273     typedef std::pair<llvm::Value *, StringRef> ValueTy;
274     TargetOpenCLBlockHelper() {}
275     virtual ~TargetOpenCLBlockHelper() {}
276     /// Get the custom field types for OpenCL blocks.
277     virtual llvm::SmallVector<llvm::Type *, 1> getCustomFieldTypes() = 0;
278     /// Get the custom field values for OpenCL blocks.
279     virtual llvm::SmallVector<ValueTy, 1>
280     getCustomFieldValues(CodeGenFunction &CGF, const CGBlockInfo &Info) = 0;
281     virtual bool areAllCustomFieldValuesConstant(const CGBlockInfo &Info) = 0;
282     /// Get the custom field values for OpenCL blocks if all values are LLVM
283     /// constants.
284     virtual llvm::SmallVector<llvm::Constant *, 1>
285     getCustomFieldValues(CodeGenModule &CGM, const CGBlockInfo &Info) = 0;
286   };
287   virtual TargetOpenCLBlockHelper *getTargetOpenCLBlockHelper() const {
288     return nullptr;
289   }
290 };
291 
292 } // namespace CodeGen
293 } // namespace clang
294 
295 #endif // LLVM_CLANG_LIB_CODEGEN_TARGETINFO_H
296