include/llvm/Attributes.h

   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 <cassert>
  20 #include <string>
  21
  22 namespace llvm {
  23 class Type;
  24
  25 /// Attributes - A bitset of attributes.
  26 typedef unsigned Attributes;
  27
  28 namespace Attribute {
  29
  30 /// Function parameters and results can have attributes to indicate how they
  31 /// should be treated by optimizations and code generation. This enumeration
  32 /// lists the attributes that can be associated with parameters, function
  33 /// results or the function itself.
  34 /// @brief Function attributes.
  35
  36 const Attributes None      = 0;     ///< No attributes have been set
  37 const Attributes ZExt      = 1<<0;  ///< Zero extended before/after call
  38 const Attributes SExt      = 1<<1;  ///< Sign extended before/after call
  39 const Attributes NoReturn  = 1<<2;  ///< Mark the function as not returning
  40 const Attributes InReg     = 1<<3;  ///< Force argument to be passed in register
  41 const Attributes StructRet = 1<<4;  ///< Hidden pointer to structure to return
  42 const Attributes NoUnwind  = 1<<5;  ///< Function doesn't unwind stack
  43 const Attributes NoAlias   = 1<<6;  ///< Considered to not alias after call
  44 const Attributes ByVal     = 1<<7;  ///< Pass structure by value
  45 const Attributes Nest      = 1<<8;  ///< Nested function static chain
  46 const Attributes ReadNone  = 1<<9;  ///< Function does not access memory
  47 const Attributes ReadOnly  = 1<<10; ///< Function only reads from memory
  48 const Attributes NoInline        = 1<<11; ///< inline=never
  49 const Attributes AlwaysInline    = 1<<12; ///< inline=always
  50 const Attributes OptimizeForSize = 1<<13; ///< opt_size
  51 const Attributes StackProtect    = 1<<14; ///< Stack protection.
  52 const Attributes StackProtectReq = 1<<15; ///< Stack protection required.
  53 const Attributes Alignment = 31<<16; ///< Alignment of parameter (5 bits)
  54                                      // stored as log2 of alignment with +1 bias
  55                                      // 0 means unaligned different from align 1
  56 const Attributes NoCapture = 1<<21; ///< Function creates no aliases of pointer
  57 const Attributes NoRedZone = 1<<22; /// disable redzone
  58 const Attributes NoImplicitFloat = 1<<23; /// disable implicit floating point
  59                                           /// instructions.
  60 const Attributes Naked           = 1<<24; ///< Naked function
  61 const Attributes InlineHint      = 1<<25; ///< source said inlining was
  62                                           ///desirable
  63 const Attributes StackAlignment  = 7<<26; ///< Alignment of stack for
  64                                           ///function (3 bits) stored as log2
  65                                           ///of alignment with +1 bias
  66                                           ///0 means unaligned (different from
  67                                           ///alignstack(1))
  68 const Attributes Hotpatch    = 1<<29;     ///< Function should have special
  69                                           ///'hotpatch' sequence in prologue
  70 const Attributes UWTable     = 1<<30;     ///< Function must be in a unwind
  71                                           ///table
  72
  73 /// Note that uwtable is about the ABI or the user mandating an entry in the
  74 /// unwind table. The nounwind attribute is about an exception passing by the
  75 /// function.
  76 /// In a theoretical system that uses tables for profiling and sjlj for
  77 /// exceptions, they would be fully independent. In a normal system that
  78 /// uses tables for both, the semantics are:
  79 /// nil                = Needs an entry because an exception might pass by.
  80 /// nounwind           = No need for an entry
  81 /// uwtable            = Needs an entry because the ABI says so and because
  82 ///                      an exception might pass by.
  83 /// uwtable + nounwind = Needs an entry because the ABI says so.
  84
  85 /// @brief Attributes that only apply to function parameters.
  86 const Attributes ParameterOnly = ByVal | Nest | StructRet | NoCapture;
  87
  88 /// @brief Attributes that may be applied to the function itself.  These cannot
  89 /// be used on return values or function parameters.
  90 const Attributes FunctionOnly = NoReturn | NoUnwind | ReadNone | ReadOnly |
  91   NoInline | AlwaysInline | OptimizeForSize | StackProtect | StackProtectReq |
  92   NoRedZone | NoImplicitFloat | Naked | InlineHint | StackAlignment |
  93   Hotpatch | UWTable;
  94
  95 /// @brief Parameter attributes that do not apply to vararg call arguments.
  96 const Attributes VarArgsIncompatible = StructRet;
  97
  98 /// @brief Attributes that are mutually incompatible.
  99 const Attributes MutuallyIncompatible[4] = {
 100   ByVal | InReg | Nest | StructRet,
 101   ZExt  | SExt,
 102   ReadNone | ReadOnly,
 103   NoInline | AlwaysInline
 104 };
 105
 106 /// @brief Which attributes cannot be applied to a type.
 107 Attributes typeIncompatible(const Type *Ty);
 108
 109 /// This turns an int alignment (a power of 2, normally) into the
 110 /// form used internally in Attributes.
 111 inline Attributes constructAlignmentFromInt(unsigned i) {
 112   // Default alignment, allow the target to define how to align it.
 113   if (i == 0)
 114     return 0;
 115
 116   assert(isPowerOf2_32(i) && "Alignment must be a power of two.");
 117   assert(i <= 0x40000000 && "Alignment too large.");
 118   return (Log2_32(i)+1) << 16;
 119 }
 120
 121 /// This returns the alignment field of an attribute as a byte alignment value.
 122 inline unsigned getAlignmentFromAttrs(Attributes A) {
 123   Attributes Align = A & Attribute::Alignment;
 124   if (Align == 0)
 125     return 0;
 126
 127   return 1U << ((Align >> 16) - 1);
 128 }
 129
 130 /// This turns an int stack alignment (which must be a power of 2) into
 131 /// the form used internally in Attributes.
 132 inline Attributes constructStackAlignmentFromInt(unsigned i) {
 133   // Default alignment, allow the target to define how to align it.
 134   if (i == 0)
 135     return 0;
 136
 137   assert(isPowerOf2_32(i) && "Alignment must be a power of two.");
 138   assert(i <= 0x100 && "Alignment too large.");
 139   return (Log2_32(i)+1) << 26;
 140 }
 141
 142 /// This returns the stack alignment field of an attribute as a byte alignment
 143 /// value.
 144 inline unsigned getStackAlignmentFromAttrs(Attributes A) {
 145   Attributes StackAlign = A & Attribute::StackAlignment;
 146   if (StackAlign == 0)
 147     return 0;
 148
 149   return 1U << ((StackAlign >> 26) - 1);
 150 }
 151
 152
 153 /// The set of Attributes set in Attributes is converted to a
 154 /// string of equivalent mnemonics. This is, presumably, for writing out
 155 /// the mnemonics for the assembly writer.
 156 /// @brief Convert attribute bits to text
 157 std::string getAsString(Attributes Attrs);
 158 } // end namespace Attribute
 159
 160 /// This is just a pair of values to associate a set of attributes
 161 /// with an index.
 162 struct AttributeWithIndex {
 163   Attributes Attrs; ///< The attributes that are set, or'd together.
 164   unsigned Index; ///< Index of the parameter for which the attributes apply.
 165                   ///< Index 0 is used for return value attributes.
 166                   ///< Index ~0U is used for function attributes.
 167
 168   static AttributeWithIndex get(unsigned Idx, Attributes Attrs) {
 169     AttributeWithIndex P;
 170     P.Index = Idx;
 171     P.Attrs = Attrs;
 172     return P;
 173   }
 174 };
 175
 176 //===----------------------------------------------------------------------===//
 177 // AttrListPtr Smart Pointer
 178 //===----------------------------------------------------------------------===//
 179
 180 class AttributeListImpl;
 181
 182 /// AttrListPtr - This class manages the ref count for the opaque
 183 /// AttributeListImpl object and provides accessors for it.
 184 class AttrListPtr {
 185   /// AttrList - The attributes that we are managing.  This can be null
 186   /// to represent the empty attributes list.
 187   AttributeListImpl *AttrList;
 188 public:
 189   AttrListPtr() : AttrList(0) {}
 190   AttrListPtr(const AttrListPtr &P);
 191   const AttrListPtr &operator=(const AttrListPtr &RHS);
 192   ~AttrListPtr();
 193
 194   //===--------------------------------------------------------------------===//
 195   // Attribute List Construction and Mutation
 196   //===--------------------------------------------------------------------===//
 197
 198   /// get - Return a Attributes list with the specified parameter in it.
 199   static AttrListPtr get(const AttributeWithIndex *Attr, unsigned NumAttrs);
 200
 201   /// get - Return a Attribute list with the parameters specified by the
 202   /// consecutive random access iterator range.
 203   template <typename Iter>
 204   static AttrListPtr get(const Iter &I, const Iter &E) {
 205     if (I == E) return AttrListPtr();  // Empty list.
 206     return get(&*I, static_cast<unsigned>(E-I));
 207   }
 208
 209   /// addAttr - Add the specified attribute at the specified index to this
 210   /// attribute list.  Since attribute lists are immutable, this
 211   /// returns the new list.
 212   AttrListPtr addAttr(unsigned Idx, Attributes Attrs) const;
 213
 214   /// removeAttr - Remove the specified attribute at the specified index from
 215   /// this attribute list.  Since attribute lists are immutable, this
 216   /// returns the new list.
 217   AttrListPtr removeAttr(unsigned Idx, Attributes Attrs) const;
 218
 219   //===--------------------------------------------------------------------===//
 220   // Attribute List Accessors
 221   //===--------------------------------------------------------------------===//
 222   /// getParamAttributes - The attributes for the specified index are
 223   /// returned.
 224   Attributes getParamAttributes(unsigned Idx) const {
 225     assert (Idx && Idx != ~0U && "Invalid parameter index!");
 226     return getAttributes(Idx);
 227   }
 228
 229   /// getRetAttributes - The attributes for the ret value are
 230   /// returned.
 231   Attributes getRetAttributes() const {
 232     return getAttributes(0);
 233   }
 234
 235   /// getFnAttributes - The function attributes are returned.
 236   Attributes getFnAttributes() const {
 237     return getAttributes(~0U);
 238   }
 239
 240   /// paramHasAttr - Return true if the specified parameter index has the
 241   /// specified attribute set.
 242   bool paramHasAttr(unsigned Idx, Attributes Attr) const {
 243     return (getAttributes(Idx) & Attr) != 0;
 244   }
 245
 246   /// getParamAlignment - Return the alignment for the specified function
 247   /// parameter.
 248   unsigned getParamAlignment(unsigned Idx) const {
 249     return Attribute::getAlignmentFromAttrs(getAttributes(Idx));
 250   }
 251
 252   /// hasAttrSomewhere - Return true if the specified attribute is set for at
 253   /// least one parameter or for the return value.
 254   bool hasAttrSomewhere(Attributes Attr) const;
 255
 256   /// operator==/!= - Provide equality predicates.
 257   bool operator==(const AttrListPtr &RHS) const
 258   { return AttrList == RHS.AttrList; }
 259   bool operator!=(const AttrListPtr &RHS) const
 260   { return AttrList != RHS.AttrList; }
 261
 262   void dump() const;
 263
 264   //===--------------------------------------------------------------------===//
 265   // Attribute List Introspection
 266   //===--------------------------------------------------------------------===//
 267
 268   /// getRawPointer - Return a raw pointer that uniquely identifies this
 269   /// attribute list.
 270   void *getRawPointer() const {
 271     return AttrList;
 272   }
 273
 274   // Attributes are stored as a dense set of slots, where there is one
 275   // slot for each argument that has an attribute.  This allows walking over the
 276   // dense set instead of walking the sparse list of attributes.
 277
 278   /// isEmpty - Return true if there are no attributes.
 279   ///
 280   bool isEmpty() const {
 281     return AttrList == 0;
 282   }
 283
 284   /// getNumSlots - Return the number of slots used in this attribute list.
 285   /// This is the number of arguments that have an attribute set on them
 286   /// (including the function itself).
 287   unsigned getNumSlots() const;
 288
 289   /// getSlot - Return the AttributeWithIndex at the specified slot.  This
 290   /// holds a index number plus a set of attributes.
 291   const AttributeWithIndex &getSlot(unsigned Slot) const;
 292
 293 private:
 294   explicit AttrListPtr(AttributeListImpl *L);
 295
 296   /// getAttributes - The attributes for the specified index are
 297   /// returned.  Attributes for the result are denoted with Idx = 0.
 298   Attributes getAttributes(unsigned Idx) const;
 299
 300 };
 301
 302 } // End llvm namespace
 303
 304 #endif