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