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 CLANG_CODEGEN_TARGETINFO_H 16 #define CLANG_CODEGEN_TARGETINFO_H 17 18 #include "clang/AST/Type.h" 19 #include "clang/Basic/LLVM.h" 20 #include "llvm/ADT/SmallString.h" 21 #include "llvm/ADT/StringRef.h" 22 23 namespace llvm { 24 class Constant; 25 class GlobalValue; 26 class Type; 27 class Value; 28 } 29 30 namespace clang { 31 class ABIInfo; 32 class Decl; 33 34 namespace CodeGen { 35 class CallArgList; 36 class CodeGenModule; 37 class CodeGenFunction; 38 class CGFunctionInfo; 39 } 40 41 /// TargetCodeGenInfo - This class organizes various target-specific 42 /// codegeneration issues, like target-specific attributes, builtins and so 43 /// on. 44 class TargetCodeGenInfo { 45 ABIInfo *Info; 46 47 public: 48 // WARNING: Acquires the ownership of ABIInfo. 49 TargetCodeGenInfo(ABIInfo *info = 0) : Info(info) {} 50 virtual ~TargetCodeGenInfo(); 51 52 /// getABIInfo() - Returns ABI info helper for the target. 53 const ABIInfo &getABIInfo() const { return *Info; } 54 55 /// SetTargetAttributes - Provides a convenient hook to handle extra 56 /// target-specific attributes for the given global. 57 virtual void SetTargetAttributes(const Decl *D, llvm::GlobalValue *GV, 58 CodeGen::CodeGenModule &M) const {} 59 60 /// EmitTargetMD - Provides a convenient hook to handle extra 61 /// target-specific metadata for the given global. 62 virtual void emitTargetMD(const Decl *D, llvm::GlobalValue *GV, 63 CodeGen::CodeGenModule &M) const {} 64 65 /// Determines the size of struct _Unwind_Exception on this platform, 66 /// in 8-bit units. The Itanium ABI defines this as: 67 /// struct _Unwind_Exception { 68 /// uint64 exception_class; 69 /// _Unwind_Exception_Cleanup_Fn exception_cleanup; 70 /// uint64 private_1; 71 /// uint64 private_2; 72 /// }; 73 virtual unsigned getSizeOfUnwindException() const; 74 75 /// Controls whether __builtin_extend_pointer should sign-extend 76 /// pointers to uint64_t or zero-extend them (the default). Has 77 /// no effect for targets: 78 /// - that have 64-bit pointers, or 79 /// - that cannot address through registers larger than pointers, or 80 /// - that implicitly ignore/truncate the top bits when addressing 81 /// through such registers. 82 virtual bool extendPointerWithSExt() const { return false; } 83 84 /// Determines the DWARF register number for the stack pointer, for 85 /// exception-handling purposes. Implements __builtin_dwarf_sp_column. 86 /// 87 /// Returns -1 if the operation is unsupported by this target. 88 virtual int getDwarfEHStackPointer(CodeGen::CodeGenModule &M) const { 89 return -1; 90 } 91 92 /// Initializes the given DWARF EH register-size table, a char*. 93 /// Implements __builtin_init_dwarf_reg_size_table. 94 /// 95 /// Returns true if the operation is unsupported by this target. 96 virtual bool initDwarfEHRegSizeTable(CodeGen::CodeGenFunction &CGF, 97 llvm::Value *Address) const { 98 return true; 99 } 100 101 /// Performs the code-generation required to convert a return 102 /// address as stored by the system into the actual address of the 103 /// next instruction that will be executed. 104 /// 105 /// Used by __builtin_extract_return_addr(). 106 virtual llvm::Value *decodeReturnAddress(CodeGen::CodeGenFunction &CGF, 107 llvm::Value *Address) const { 108 return Address; 109 } 110 111 /// Performs the code-generation required to convert the address 112 /// of an instruction into a return address suitable for storage 113 /// by the system in a return slot. 114 /// 115 /// Used by __builtin_frob_return_addr(). 116 virtual llvm::Value *encodeReturnAddress(CodeGen::CodeGenFunction &CGF, 117 llvm::Value *Address) const { 118 return Address; 119 } 120 121 /// Corrects the low-level LLVM type for a given constraint and "usual" 122 /// type. 123 /// 124 /// \returns A pointer to a new LLVM type, possibly the same as the original 125 /// on success; 0 on failure. 126 virtual llvm::Type *adjustInlineAsmType(CodeGen::CodeGenFunction &CGF, 127 StringRef Constraint, 128 llvm::Type *Ty) const { 129 return Ty; 130 } 131 132 /// doesReturnSlotInterfereWithArgs - Return true if the target uses an 133 /// argument slot for an 'sret' type. 134 virtual bool doesReturnSlotInterfereWithArgs() const { return true; } 135 136 /// Retrieve the address of a function to call immediately before 137 /// calling objc_retainAutoreleasedReturnValue. The 138 /// implementation of objc_autoreleaseReturnValue sniffs the 139 /// instruction stream following its return address to decide 140 /// whether it's a call to objc_retainAutoreleasedReturnValue. 141 /// This can be prohibitively expensive, depending on the 142 /// relocation model, and so on some targets it instead sniffs for 143 /// a particular instruction sequence. This functions returns 144 /// that instruction sequence in inline assembly, which will be 145 /// empty if none is required. 146 virtual StringRef getARCRetainAutoreleasedReturnValueMarker() const { 147 return ""; 148 } 149 150 /// Return a constant used by UBSan as a signature to identify functions 151 /// possessing type information, or 0 if the platform is unsupported. 152 virtual llvm::Constant * 153 getUBSanFunctionSignature(CodeGen::CodeGenModule &CGM) const { 154 return nullptr; 155 } 156 157 /// Determine whether a call to an unprototyped functions under 158 /// the given calling convention should use the variadic 159 /// convention or the non-variadic convention. 160 /// 161 /// There's a good reason to make a platform's variadic calling 162 /// convention be different from its non-variadic calling 163 /// convention: the non-variadic arguments can be passed in 164 /// registers (better for performance), and the variadic arguments 165 /// can be passed on the stack (also better for performance). If 166 /// this is done, however, unprototyped functions *must* use the 167 /// non-variadic convention, because C99 states that a call 168 /// through an unprototyped function type must succeed if the 169 /// function was defined with a non-variadic prototype with 170 /// compatible parameters. Therefore, splitting the conventions 171 /// makes it impossible to call a variadic function through an 172 /// unprototyped type. Since function prototypes came out in the 173 /// late 1970s, this is probably an acceptable trade-off. 174 /// Nonetheless, not all platforms are willing to make it, and in 175 /// particularly x86-64 bends over backwards to make the 176 /// conventions compatible. 177 /// 178 /// The default is false. This is correct whenever: 179 /// - the conventions are exactly the same, because it does not 180 /// matter and the resulting IR will be somewhat prettier in 181 /// certain cases; or 182 /// - the conventions are substantively different in how they pass 183 /// arguments, because in this case using the variadic convention 184 /// will lead to C99 violations. 185 /// 186 /// However, some platforms make the conventions identical except 187 /// for passing additional out-of-band information to a variadic 188 /// function: for example, x86-64 passes the number of SSE 189 /// arguments in %al. On these platforms, it is desirable to 190 /// call unprototyped functions using the variadic convention so 191 /// that unprototyped calls to varargs functions still succeed. 192 /// 193 /// Relatedly, platforms which pass the fixed arguments to this: 194 /// A foo(B, C, D); 195 /// differently than they would pass them to this: 196 /// A foo(B, C, D, ...); 197 /// may need to adjust the debugger-support code in Sema to do the 198 /// right thing when calling a function with no know signature. 199 virtual bool isNoProtoCallVariadic(const CodeGen::CallArgList &args, 200 const FunctionNoProtoType *fnType) const; 201 202 /// Gets the linker options necessary to link a dependent library on this 203 /// platform. 204 virtual void getDependentLibraryOption(llvm::StringRef Lib, 205 llvm::SmallString<24> &Opt) const; 206 207 /// Gets the linker options necessary to detect object file mismatches on 208 /// this platform. 209 virtual void getDetectMismatchOption(llvm::StringRef Name, 210 llvm::StringRef Value, 211 llvm::SmallString<32> &Opt) const {} 212 }; 213 } 214 215 #endif // CLANG_CODEGEN_TARGETINFO_H 216
