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