1 //===-- llvm/Attributes.h - Container for Attributes ------------*- 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 // This file contains the simple types necessary to represent the 11 // attributes associated with functions and their calls. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_ATTRIBUTES_H 16 #define LLVM_ATTRIBUTES_H 17 18 #include "llvm/Support/MathExtras.h" 19 #include "llvm/ADT/ArrayRef.h" 20 #include <cassert> 21 #include <string> 22 23 namespace llvm { 24 class Type; 25 26 namespace Attribute { 27 /// We use this proxy POD type to allow constructing Attributes constants 28 /// using initializer lists. Do not use this class directly. 29 struct AttrConst { 30 uint64_t v; 31 AttrConst operator | (const AttrConst Attrs) const { 32 AttrConst Res = {v | Attrs.v}; 33 return Res; 34 } 35 AttrConst operator ~ () const { 36 AttrConst Res = {~v}; 37 return Res; 38 } 39 }; 40 } // namespace Attribute 41 42 43 /// Attributes - A bitset of attributes. 44 class Attributes { 45 public: 46 Attributes() : Bits(0) { } 47 explicit Attributes(uint64_t Val) : Bits(Val) { } 48 /*implicit*/ Attributes(Attribute::AttrConst Val) : Bits(Val.v) { } 49 // This is a "safe bool() operator". 50 operator const void *() const { return Bits ? this : 0; } 51 bool isEmptyOrSingleton() const { return (Bits & (Bits - 1)) == 0; } 52 bool operator == (const Attributes &Attrs) const { 53 return Bits == Attrs.Bits; 54 } 55 bool operator != (const Attributes &Attrs) const { 56 return Bits != Attrs.Bits; 57 } 58 Attributes operator | (const Attributes &Attrs) const { 59 return Attributes(Bits | Attrs.Bits); 60 } 61 Attributes operator & (const Attributes &Attrs) const { 62 return Attributes(Bits & Attrs.Bits); 63 } 64 Attributes operator ^ (const Attributes &Attrs) const { 65 return Attributes(Bits ^ Attrs.Bits); 66 } 67 Attributes &operator |= (const Attributes &Attrs) { 68 Bits |= Attrs.Bits; 69 return *this; 70 } 71 Attributes &operator &= (const Attributes &Attrs) { 72 Bits &= Attrs.Bits; 73 return *this; 74 } 75 Attributes operator ~ () const { return Attributes(~Bits); } 76 uint64_t Raw() const { return Bits; } 77 private: 78 // Currently, we need less than 64 bits. 79 uint64_t Bits; 80 }; 81 82 namespace Attribute { 83 84 /// Function parameters and results can have attributes to indicate how they 85 /// should be treated by optimizations and code generation. This enumeration 86 /// lists the attributes that can be associated with parameters, function 87 /// results or the function itself. 88 /// @brief Function attributes. 89 90 // We declare AttrConst objects that will be used throughout the code 91 // and also raw uint64_t objects with _i suffix to be used below for other 92 // constant declarations. This is done to avoid static CTORs and at the same 93 // time to keep type-safety of Attributes. 94 #define DECLARE_LLVM_ATTRIBUTE(name, value) \ 95 const uint64_t name##_i = value; \ 96 const AttrConst name = {value}; 97 98 DECLARE_LLVM_ATTRIBUTE(None,0) ///< No attributes have been set 99 DECLARE_LLVM_ATTRIBUTE(ZExt,1<<0) ///< Zero extended before/after call 100 DECLARE_LLVM_ATTRIBUTE(SExt,1<<1) ///< Sign extended before/after call 101 DECLARE_LLVM_ATTRIBUTE(NoReturn,1<<2) ///< Mark the function as not returning 102 DECLARE_LLVM_ATTRIBUTE(InReg,1<<3) ///< Force argument to be passed in register 103 DECLARE_LLVM_ATTRIBUTE(StructRet,1<<4) ///< Hidden pointer to structure to return 104 DECLARE_LLVM_ATTRIBUTE(NoUnwind,1<<5) ///< Function doesn't unwind stack 105 DECLARE_LLVM_ATTRIBUTE(NoAlias,1<<6) ///< Considered to not alias after call 106 DECLARE_LLVM_ATTRIBUTE(ByVal,1<<7) ///< Pass structure by value 107 DECLARE_LLVM_ATTRIBUTE(Nest,1<<8) ///< Nested function static chain 108 DECLARE_LLVM_ATTRIBUTE(ReadNone,1<<9) ///< Function does not access memory 109 DECLARE_LLVM_ATTRIBUTE(ReadOnly,1<<10) ///< Function only reads from memory 110 DECLARE_LLVM_ATTRIBUTE(NoInline,1<<11) ///< inline=never 111 DECLARE_LLVM_ATTRIBUTE(AlwaysInline,1<<12) ///< inline=always 112 DECLARE_LLVM_ATTRIBUTE(OptimizeForSize,1<<13) ///< opt_size 113 DECLARE_LLVM_ATTRIBUTE(StackProtect,1<<14) ///< Stack protection. 114 DECLARE_LLVM_ATTRIBUTE(StackProtectReq,1<<15) ///< Stack protection required. 115 DECLARE_LLVM_ATTRIBUTE(Alignment,31<<16) ///< Alignment of parameter (5 bits) 116 // stored as log2 of alignment with +1 bias 117 // 0 means unaligned different from align 1 118 DECLARE_LLVM_ATTRIBUTE(NoCapture,1<<21) ///< Function creates no aliases of pointer 119 DECLARE_LLVM_ATTRIBUTE(NoRedZone,1<<22) /// disable redzone 120 DECLARE_LLVM_ATTRIBUTE(NoImplicitFloat,1<<23) /// disable implicit floating point 121 /// instructions. 122 DECLARE_LLVM_ATTRIBUTE(Naked,1<<24) ///< Naked function 123 DECLARE_LLVM_ATTRIBUTE(InlineHint,1<<25) ///< source said inlining was 124 ///desirable 125 DECLARE_LLVM_ATTRIBUTE(StackAlignment,7<<26) ///< Alignment of stack for 126 ///function (3 bits) stored as log2 127 ///of alignment with +1 bias 128 ///0 means unaligned (different from 129 ///alignstack= {1)) 130 DECLARE_LLVM_ATTRIBUTE(ReturnsTwice,1<<29) ///< Function can return twice 131 DECLARE_LLVM_ATTRIBUTE(UWTable,1<<30) ///< Function must be in a unwind 132 ///table 133 DECLARE_LLVM_ATTRIBUTE(NonLazyBind,1U<<31) ///< Function is called early and/or 134 /// often, so lazy binding isn't 135 /// worthwhile. 136 DECLARE_LLVM_ATTRIBUTE(AddressSafety,1ULL<<32) ///< Address safety checking is on. 137 138 #undef DECLARE_LLVM_ATTRIBUTE 139 140 /// Note that uwtable is about the ABI or the user mandating an entry in the 141 /// unwind table. The nounwind attribute is about an exception passing by the 142 /// function. 143 /// In a theoretical system that uses tables for profiling and sjlj for 144 /// exceptions, they would be fully independent. In a normal system that 145 /// uses tables for both, the semantics are: 146 /// nil = Needs an entry because an exception might pass by. 147 /// nounwind = No need for an entry 148 /// uwtable = Needs an entry because the ABI says so and because 149 /// an exception might pass by. 150 /// uwtable + nounwind = Needs an entry because the ABI says so. 151 152 /// @brief Attributes that only apply to function parameters. 153 const AttrConst ParameterOnly = {ByVal_i | Nest_i | 154 StructRet_i | NoCapture_i}; 155 156 /// @brief Attributes that may be applied to the function itself. These cannot 157 /// be used on return values or function parameters. 158 const AttrConst FunctionOnly = {NoReturn_i | NoUnwind_i | ReadNone_i | 159 ReadOnly_i | NoInline_i | AlwaysInline_i | OptimizeForSize_i | 160 StackProtect_i | StackProtectReq_i | NoRedZone_i | NoImplicitFloat_i | 161 Naked_i | InlineHint_i | StackAlignment_i | 162 UWTable_i | NonLazyBind_i | ReturnsTwice_i | AddressSafety_i}; 163 164 /// @brief Parameter attributes that do not apply to vararg call arguments. 165 const AttrConst VarArgsIncompatible = {StructRet_i}; 166 167 /// @brief Attributes that are mutually incompatible. 168 const AttrConst MutuallyIncompatible[5] = { 169 {ByVal_i | Nest_i | StructRet_i}, 170 {ByVal_i | Nest_i | InReg_i }, 171 {ZExt_i | SExt_i}, 172 {ReadNone_i | ReadOnly_i}, 173 {NoInline_i | AlwaysInline_i} 174 }; 175 176 /// @brief Which attributes cannot be applied to a type. 177 Attributes typeIncompatible(Type *Ty); 178 179 /// This turns an int alignment (a power of 2, normally) into the 180 /// form used internally in Attributes. 181 inline Attributes constructAlignmentFromInt(unsigned i) { 182 // Default alignment, allow the target to define how to align it. 183 if (i == 0) 184 return None; 185 186 assert(isPowerOf2_32(i) && "Alignment must be a power of two."); 187 assert(i <= 0x40000000 && "Alignment too large."); 188 return Attributes((Log2_32(i)+1) << 16); 189 } 190 191 /// This returns the alignment field of an attribute as a byte alignment value. 192 inline unsigned getAlignmentFromAttrs(Attributes A) { 193 Attributes Align = A & Attribute::Alignment; 194 if (!Align) 195 return 0; 196 197 return 1U << ((Align.Raw() >> 16) - 1); 198 } 199 200 /// This turns an int stack alignment (which must be a power of 2) into 201 /// the form used internally in Attributes. 202 inline Attributes constructStackAlignmentFromInt(unsigned i) { 203 // Default alignment, allow the target to define how to align it. 204 if (i == 0) 205 return None; 206 207 assert(isPowerOf2_32(i) && "Alignment must be a power of two."); 208 assert(i <= 0x100 && "Alignment too large."); 209 return Attributes((Log2_32(i)+1) << 26); 210 } 211 212 /// This returns the stack alignment field of an attribute as a byte alignment 213 /// value. 214 inline unsigned getStackAlignmentFromAttrs(Attributes A) { 215 Attributes StackAlign = A & Attribute::StackAlignment; 216 if (!StackAlign) 217 return 0; 218 219 return 1U << ((StackAlign.Raw() >> 26) - 1); 220 } 221 222 /// This returns an integer containing an encoding of all the 223 /// LLVM attributes found in the given attribute bitset. Any 224 /// change to this encoding is a breaking change to bitcode 225 /// compatibility. 226 inline uint64_t encodeLLVMAttributesForBitcode(Attributes Attrs) { 227 // FIXME: It doesn't make sense to store the alignment information as an 228 // expanded out value, we should store it as a log2 value. However, we can't 229 // just change that here without breaking bitcode compatibility. If this ever 230 // becomes a problem in practice, we should introduce new tag numbers in the 231 // bitcode file and have those tags use a more efficiently encoded alignment 232 // field. 233 234 // Store the alignment in the bitcode as a 16-bit raw value instead of a 235 // 5-bit log2 encoded value. Shift the bits above the alignment up by 236 // 11 bits. 237 238 uint64_t EncodedAttrs = Attrs.Raw() & 0xffff; 239 if (Attrs & Attribute::Alignment) 240 EncodedAttrs |= (1ull << 16) << 241 (((Attrs & Attribute::Alignment).Raw()-1) >> 16); 242 EncodedAttrs |= (Attrs.Raw() & (0xfffull << 21)) << 11; 243 244 return EncodedAttrs; 245 } 246 247 /// This returns an attribute bitset containing the LLVM attributes 248 /// that have been decoded from the given integer. This function 249 /// must stay in sync with 'encodeLLVMAttributesForBitcode'. 250 inline Attributes decodeLLVMAttributesForBitcode(uint64_t EncodedAttrs) { 251 // The alignment is stored as a 16-bit raw value from bits 31--16. 252 // We shift the bits above 31 down by 11 bits. 253 254 unsigned Alignment = (EncodedAttrs & (0xffffull << 16)) >> 16; 255 assert((!Alignment || isPowerOf2_32(Alignment)) && 256 "Alignment must be a power of two."); 257 258 Attributes Attrs(EncodedAttrs & 0xffff); 259 if (Alignment) 260 Attrs |= Attribute::constructAlignmentFromInt(Alignment); 261 Attrs |= Attributes((EncodedAttrs & (0xfffull << 32)) >> 11); 262 263 return Attrs; 264 } 265 266 267 /// The set of Attributes set in Attributes is converted to a 268 /// string of equivalent mnemonics. This is, presumably, for writing out 269 /// the mnemonics for the assembly writer. 270 /// @brief Convert attribute bits to text 271 std::string getAsString(Attributes Attrs); 272 } // end namespace Attribute 273 274 /// This is just a pair of values to associate a set of attributes 275 /// with an index. 276 struct AttributeWithIndex { 277 Attributes Attrs; ///< The attributes that are set, or'd together. 278 unsigned Index; ///< Index of the parameter for which the attributes apply. 279 ///< Index 0 is used for return value attributes. 280 ///< Index ~0U is used for function attributes. 281 282 static AttributeWithIndex get(unsigned Idx, Attributes Attrs) { 283 AttributeWithIndex P; 284 P.Index = Idx; 285 P.Attrs = Attrs; 286 return P; 287 } 288 }; 289 290 //===----------------------------------------------------------------------===// 291 // AttrListPtr Smart Pointer 292 //===----------------------------------------------------------------------===// 293 294 class AttributeListImpl; 295 296 /// AttrListPtr - This class manages the ref count for the opaque 297 /// AttributeListImpl object and provides accessors for it. 298 class AttrListPtr { 299 /// AttrList - The attributes that we are managing. This can be null 300 /// to represent the empty attributes list. 301 AttributeListImpl *AttrList; 302 public: 303 AttrListPtr() : AttrList(0) {} 304 AttrListPtr(const AttrListPtr &P); 305 const AttrListPtr &operator=(const AttrListPtr &RHS); 306 ~AttrListPtr(); 307 308 //===--------------------------------------------------------------------===// 309 // Attribute List Construction and Mutation 310 //===--------------------------------------------------------------------===// 311 312 /// get - Return a Attributes list with the specified parameters in it. 313 static AttrListPtr get(ArrayRef<AttributeWithIndex> Attrs); 314 315 /// addAttr - Add the specified attribute at the specified index to this 316 /// attribute list. Since attribute lists are immutable, this 317 /// returns the new list. 318 AttrListPtr addAttr(unsigned Idx, Attributes Attrs) const; 319 320 /// removeAttr - Remove the specified attribute at the specified index from 321 /// this attribute list. Since attribute lists are immutable, this 322 /// returns the new list. 323 AttrListPtr removeAttr(unsigned Idx, Attributes Attrs) const; 324 325 //===--------------------------------------------------------------------===// 326 // Attribute List Accessors 327 //===--------------------------------------------------------------------===// 328 /// getParamAttributes - The attributes for the specified index are 329 /// returned. 330 Attributes getParamAttributes(unsigned Idx) const { 331 assert (Idx && Idx != ~0U && "Invalid parameter index!"); 332 return getAttributes(Idx); 333 } 334 335 /// getRetAttributes - The attributes for the ret value are 336 /// returned. 337 Attributes getRetAttributes() const { 338 return getAttributes(0); 339 } 340 341 /// getFnAttributes - The function attributes are returned. 342 Attributes getFnAttributes() const { 343 return getAttributes(~0U); 344 } 345 346 /// paramHasAttr - Return true if the specified parameter index has the 347 /// specified attribute set. 348 bool paramHasAttr(unsigned Idx, Attributes Attr) const { 349 return getAttributes(Idx) & Attr; 350 } 351 352 /// getParamAlignment - Return the alignment for the specified function 353 /// parameter. 354 unsigned getParamAlignment(unsigned Idx) const { 355 return Attribute::getAlignmentFromAttrs(getAttributes(Idx)); 356 } 357 358 /// hasAttrSomewhere - Return true if the specified attribute is set for at 359 /// least one parameter or for the return value. 360 bool hasAttrSomewhere(Attributes Attr) const; 361 362 /// operator==/!= - Provide equality predicates. 363 bool operator==(const AttrListPtr &RHS) const 364 { return AttrList == RHS.AttrList; } 365 bool operator!=(const AttrListPtr &RHS) const 366 { return AttrList != RHS.AttrList; } 367 368 void dump() const; 369 370 //===--------------------------------------------------------------------===// 371 // Attribute List Introspection 372 //===--------------------------------------------------------------------===// 373 374 /// getRawPointer - Return a raw pointer that uniquely identifies this 375 /// attribute list. 376 void *getRawPointer() const { 377 return AttrList; 378 } 379 380 // Attributes are stored as a dense set of slots, where there is one 381 // slot for each argument that has an attribute. This allows walking over the 382 // dense set instead of walking the sparse list of attributes. 383 384 /// isEmpty - Return true if there are no attributes. 385 /// 386 bool isEmpty() const { 387 return AttrList == 0; 388 } 389 390 /// getNumSlots - Return the number of slots used in this attribute list. 391 /// This is the number of arguments that have an attribute set on them 392 /// (including the function itself). 393 unsigned getNumSlots() const; 394 395 /// getSlot - Return the AttributeWithIndex at the specified slot. This 396 /// holds a index number plus a set of attributes. 397 const AttributeWithIndex &getSlot(unsigned Slot) const; 398 399 private: 400 explicit AttrListPtr(AttributeListImpl *L); 401 402 /// getAttributes - The attributes for the specified index are 403 /// returned. Attributes for the result are denoted with Idx = 0. 404 Attributes getAttributes(unsigned Idx) const; 405 406 }; 407 408 } // End llvm namespace 409 410 #endif 411