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