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 virtual llvm::Type* adjustInlineAsmType(CodeGen::CodeGenFunction &CGF, 115 StringRef Constraint, 116 llvm::Type* Ty) const { 117 return Ty; 118 } 119 120 /// Retrieve the address of a function to call immediately before 121 /// calling objc_retainAutoreleasedReturnValue. The 122 /// implementation of objc_autoreleaseReturnValue sniffs the 123 /// instruction stream following its return address to decide 124 /// whether it's a call to objc_retainAutoreleasedReturnValue. 125 /// This can be prohibitively expensive, depending on the 126 /// relocation model, and so on some targets it instead sniffs for 127 /// a particular instruction sequence. This functions returns 128 /// that instruction sequence in inline assembly, which will be 129 /// empty if none is required. 130 virtual StringRef getARCRetainAutoreleasedReturnValueMarker() const { 131 return ""; 132 } 133 134 /// Determine whether a call to an unprototyped functions under 135 /// the given calling convention should use the variadic 136 /// convention or the non-variadic convention. 137 /// 138 /// There's a good reason to make a platform's variadic calling 139 /// convention be different from its non-variadic calling 140 /// convention: the non-variadic arguments can be passed in 141 /// registers (better for performance), and the variadic arguments 142 /// can be passed on the stack (also better for performance). If 143 /// this is done, however, unprototyped functions *must* use the 144 /// non-variadic convention, because C99 states that a call 145 /// through an unprototyped function type must succeed if the 146 /// function was defined with a non-variadic prototype with 147 /// compatible parameters. Therefore, splitting the conventions 148 /// makes it impossible to call a variadic function through an 149 /// unprototyped type. Since function prototypes came out in the 150 /// late 1970s, this is probably an acceptable trade-off. 151 /// Nonetheless, not all platforms are willing to make it, and in 152 /// particularly x86-64 bends over backwards to make the 153 /// conventions compatible. 154 /// 155 /// The default is false. This is correct whenever: 156 /// - the conventions are exactly the same, because it does not 157 /// matter and the resulting IR will be somewhat prettier in 158 /// certain cases; or 159 /// - the conventions are substantively different in how they pass 160 /// arguments, because in this case using the variadic convention 161 /// will lead to C99 violations. 162 /// 163 /// However, some platforms make the conventions identical except 164 /// for passing additional out-of-band information to a variadic 165 /// function: for example, x86-64 passes the number of SSE 166 /// arguments in %al. On these platforms, it is desireable to 167 /// call unprototyped functions using the variadic convention so 168 /// that unprototyped calls to varargs functions still succeed. 169 virtual bool isNoProtoCallVariadic(const CodeGen::CallArgList &args, 170 const FunctionNoProtoType *fnType) const; 171 172 /// Gets the linker options necessary to link a dependent library on this 173 /// platform. 174 virtual void getDependentLibraryOption(llvm::StringRef Lib, 175 llvm::SmallString<24> &Opt) const; 176 }; 177 } 178 179 #endif // CLANG_CODEGEN_TARGETINFO_H 180