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 "CGValue.h" 19 #include "clang/AST/Type.h" 20 #include "clang/Basic/LLVM.h" 21 #include "llvm/ADT/SmallString.h" 22 #include "llvm/ADT/StringRef.h" 23 24 namespace llvm { 25 class Constant; 26 class GlobalValue; 27 class Type; 28 class Value; 29 } 30 31 namespace clang { 32 class ABIInfo; 33 class Decl; 34 35 namespace CodeGen { 36 class CallArgList; 37 class CodeGenModule; 38 class CodeGenFunction; 39 class CGFunctionInfo; 40 } 41 42 /// TargetCodeGenInfo - This class organizes various target-specific 43 /// codegeneration issues, like target-specific attributes, builtins and so 44 /// on. 45 class TargetCodeGenInfo { 46 ABIInfo *Info; 47 48 public: 49 // WARNING: Acquires the ownership of ABIInfo. 50 TargetCodeGenInfo(ABIInfo *info = 0) : Info(info) {} 51 virtual ~TargetCodeGenInfo(); 52 53 /// getABIInfo() - Returns ABI info helper for the target. 54 const ABIInfo &getABIInfo() const { return *Info; } 55 56 /// SetTargetAttributes - Provides a convenient hook to handle extra 57 /// target-specific attributes for the given global. 58 virtual void SetTargetAttributes(const Decl *D, llvm::GlobalValue *GV, 59 CodeGen::CodeGenModule &M) const {} 60 61 /// EmitTargetMD - Provides a convenient hook to handle extra 62 /// target-specific metadata for the given global. 63 virtual void emitTargetMD(const Decl *D, llvm::GlobalValue *GV, 64 CodeGen::CodeGenModule &M) const {} 65 66 /// Determines the size of struct _Unwind_Exception on this platform, 67 /// in 8-bit units. The Itanium ABI defines this as: 68 /// struct _Unwind_Exception { 69 /// uint64 exception_class; 70 /// _Unwind_Exception_Cleanup_Fn exception_cleanup; 71 /// uint64 private_1; 72 /// uint64 private_2; 73 /// }; 74 virtual unsigned getSizeOfUnwindException() const; 75 76 /// Controls whether __builtin_extend_pointer should sign-extend 77 /// pointers to uint64_t or zero-extend them (the default). Has 78 /// no effect for targets: 79 /// - that have 64-bit pointers, or 80 /// - that cannot address through registers larger than pointers, or 81 /// - that implicitly ignore/truncate the top bits when addressing 82 /// through such registers. 83 virtual bool extendPointerWithSExt() const { return false; } 84 85 /// Determines the DWARF register number for the stack pointer, for 86 /// exception-handling purposes. Implements __builtin_dwarf_sp_column. 87 /// 88 /// Returns -1 if the operation is unsupported by this target. 89 virtual int getDwarfEHStackPointer(CodeGen::CodeGenModule &M) const { 90 return -1; 91 } 92 93 /// Initializes the given DWARF EH register-size table, a char*. 94 /// Implements __builtin_init_dwarf_reg_size_table. 95 /// 96 /// Returns true if the operation is unsupported by this target. 97 virtual bool initDwarfEHRegSizeTable(CodeGen::CodeGenFunction &CGF, 98 llvm::Value *Address) const { 99 return true; 100 } 101 102 /// Performs the code-generation required to convert a return 103 /// address as stored by the system into the actual address of the 104 /// next instruction that will be executed. 105 /// 106 /// Used by __builtin_extract_return_addr(). 107 virtual llvm::Value *decodeReturnAddress(CodeGen::CodeGenFunction &CGF, 108 llvm::Value *Address) const { 109 return Address; 110 } 111 112 /// Performs the code-generation required to convert the address 113 /// of an instruction into a return address suitable for storage 114 /// by the system in a return slot. 115 /// 116 /// Used by __builtin_frob_return_addr(). 117 virtual llvm::Value *encodeReturnAddress(CodeGen::CodeGenFunction &CGF, 118 llvm::Value *Address) const { 119 return Address; 120 } 121 122 /// Corrects the low-level LLVM type for a given constraint and "usual" 123 /// type. 124 /// 125 /// \returns A pointer to a new LLVM type, possibly the same as the original 126 /// on success; 0 on failure. 127 virtual llvm::Type *adjustInlineAsmType(CodeGen::CodeGenFunction &CGF, 128 StringRef Constraint, 129 llvm::Type *Ty) const { 130 return Ty; 131 } 132 133 /// Adds constraints and types for result registers. 134 virtual void addReturnRegisterOutputs( 135 CodeGen::CodeGenFunction &CGF, CodeGen::LValue ReturnValue, 136 std::string &Constraints, std::vector<llvm::Type *> &ResultRegTypes, 137 std::vector<llvm::Type *> &ResultTruncRegTypes, 138 std::vector<CodeGen::LValue> &ResultRegDests, std::string &AsmString, 139 unsigned NumOutputs) const {} 140 141 /// doesReturnSlotInterfereWithArgs - Return true if the target uses an 142 /// argument slot for an 'sret' type. 143 virtual bool doesReturnSlotInterfereWithArgs() const { return true; } 144 145 /// Retrieve the address of a function to call immediately before 146 /// calling objc_retainAutoreleasedReturnValue. The 147 /// implementation of objc_autoreleaseReturnValue sniffs the 148 /// instruction stream following its return address to decide 149 /// whether it's a call to objc_retainAutoreleasedReturnValue. 150 /// This can be prohibitively expensive, depending on the 151 /// relocation model, and so on some targets it instead sniffs for 152 /// a particular instruction sequence. This functions returns 153 /// that instruction sequence in inline assembly, which will be 154 /// empty if none is required. 155 virtual StringRef getARCRetainAutoreleasedReturnValueMarker() const { 156 return ""; 157 } 158 159 /// Return a constant used by UBSan as a signature to identify functions 160 /// possessing type information, or 0 if the platform is unsupported. 161 virtual llvm::Constant * 162 getUBSanFunctionSignature(CodeGen::CodeGenModule &CGM) const { 163 return nullptr; 164 } 165 166 /// Determine whether a call to an unprototyped functions under 167 /// the given calling convention should use the variadic 168 /// convention or the non-variadic convention. 169 /// 170 /// There's a good reason to make a platform's variadic calling 171 /// convention be different from its non-variadic calling 172 /// convention: the non-variadic arguments can be passed in 173 /// registers (better for performance), and the variadic arguments 174 /// can be passed on the stack (also better for performance). If 175 /// this is done, however, unprototyped functions *must* use the 176 /// non-variadic convention, because C99 states that a call 177 /// through an unprototyped function type must succeed if the 178 /// function was defined with a non-variadic prototype with 179 /// compatible parameters. Therefore, splitting the conventions 180 /// makes it impossible to call a variadic function through an 181 /// unprototyped type. Since function prototypes came out in the 182 /// late 1970s, this is probably an acceptable trade-off. 183 /// Nonetheless, not all platforms are willing to make it, and in 184 /// particularly x86-64 bends over backwards to make the 185 /// conventions compatible. 186 /// 187 /// The default is false. This is correct whenever: 188 /// - the conventions are exactly the same, because it does not 189 /// matter and the resulting IR will be somewhat prettier in 190 /// certain cases; or 191 /// - the conventions are substantively different in how they pass 192 /// arguments, because in this case using the variadic convention 193 /// will lead to C99 violations. 194 /// 195 /// However, some platforms make the conventions identical except 196 /// for passing additional out-of-band information to a variadic 197 /// function: for example, x86-64 passes the number of SSE 198 /// arguments in %al. On these platforms, it is desirable to 199 /// call unprototyped functions using the variadic convention so 200 /// that unprototyped calls to varargs functions still succeed. 201 /// 202 /// Relatedly, platforms which pass the fixed arguments to this: 203 /// A foo(B, C, D); 204 /// differently than they would pass them to this: 205 /// A foo(B, C, D, ...); 206 /// may need to adjust the debugger-support code in Sema to do the 207 /// right thing when calling a function with no know signature. 208 virtual bool isNoProtoCallVariadic(const CodeGen::CallArgList &args, 209 const FunctionNoProtoType *fnType) const; 210 211 /// Gets the linker options necessary to link a dependent library on this 212 /// platform. 213 virtual void getDependentLibraryOption(llvm::StringRef Lib, 214 llvm::SmallString<24> &Opt) const; 215 216 /// Gets the linker options necessary to detect object file mismatches on 217 /// this platform. 218 virtual void getDetectMismatchOption(llvm::StringRef Name, 219 llvm::StringRef Value, 220 llvm::SmallString<32> &Opt) const {} 221 222 /// Gets the target-specific default alignment used when an 'aligned' clause 223 /// is used with a 'simd' OpenMP directive without specifying a specific 224 /// alignment. 225 virtual unsigned getOpenMPSimdDefaultAlignment(QualType Type) const { 226 return 0; 227 } 228 }; 229 } 230 231 #endif 232
