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 const Attributes NonLazyBind = 1U<<31;    ///< Function is called early and/or
  73                                           ///  often, so lazy binding isn't
  74                                           ///  worthwhile.
  75
  76 /// Note that uwtable is about the ABI or the user mandating an entry in the
  77 /// unwind table. The nounwind attribute is about an exception passing by the
  78 /// function.
  79 /// In a theoretical system that uses tables for profiling and sjlj for
  80 /// exceptions, they would be fully independent. In a normal system that
  81 /// uses tables for both, the semantics are:
  82 /// nil                = Needs an entry because an exception might pass by.
  83 /// nounwind           = No need for an entry
  84 /// uwtable            = Needs an entry because the ABI says so and because
  85 ///                      an exception might pass by.
  86 /// uwtable + nounwind = Needs an entry because the ABI says so.
  87
  88 /// @brief Attributes that only apply to function parameters.
  89 const Attributes ParameterOnly = ByVal | Nest | StructRet | NoCapture;
  90
  91 /// @brief Attributes that may be applied to the function itself.  These cannot
  92 /// be used on return values or function parameters.
  93 const Attributes FunctionOnly = NoReturn | NoUnwind | ReadNone | ReadOnly |
  94   NoInline | AlwaysInline | OptimizeForSize | StackProtect | StackProtectReq |
  95   NoRedZone | NoImplicitFloat | Naked | InlineHint | StackAlignment |
  96   Hotpatch | UWTable | NonLazyBind;
  97
  98 /// @brief Parameter attributes that do not apply to vararg call arguments.
  99 const Attributes VarArgsIncompatible = StructRet;
 100
 101 /// @brief Attributes that are mutually incompatible.
 102 const Attributes MutuallyIncompatible[4] = {
 103   ByVal | InReg | Nest | StructRet,
 104   ZExt  | SExt,
 105   ReadNone | ReadOnly,
 106   NoInline | AlwaysInline
 107 };
 108
 109 /// @brief Which attributes cannot be applied to a type.
 110 Attributes typeIncompatible(const Type *Ty);
 111
 112 /// This turns an int alignment (a power of 2, normally) into the
 113 /// form used internally in Attributes.
 114 inline Attributes constructAlignmentFromInt(unsigned i) {
 115   // Default alignment, allow the target to define how to align it.
 116   if (i == 0)
 117     return 0;
 118
 119   assert(isPowerOf2_32(i) && "Alignment must be a power of two.");
 120   assert(i <= 0x40000000 && "Alignment too large.");
 121   return (Log2_32(i)+1) << 16;
 122 }
 123
 124 /// This returns the alignment field of an attribute as a byte alignment value.
 125 inline unsigned getAlignmentFromAttrs(Attributes A) {
 126   Attributes Align = A & Attribute::Alignment;
 127   if (Align == 0)
 128     return 0;
 129
 130   return 1U << ((Align >> 16) - 1);
 131 }
 132
 133 /// This turns an int stack alignment (which must be a power of 2) into
 134 /// the form used internally in Attributes.
 135 inline Attributes constructStackAlignmentFromInt(unsigned i) {
 136   // Default alignment, allow the target to define how to align it.
 137   if (i == 0)
 138     return 0;
 139
 140   assert(isPowerOf2_32(i) && "Alignment must be a power of two.");
 141   assert(i <= 0x100 && "Alignment too large.");
 142   return (Log2_32(i)+1) << 26;
 143 }
 144
 145 /// This returns the stack alignment field of an attribute as a byte alignment
 146 /// value.
 147 inline unsigned getStackAlignmentFromAttrs(Attributes A) {
 148   Attributes StackAlign = A & Attribute::StackAlignment;
 149   if (StackAlign == 0)
 150     return 0;
 151
 152   return 1U << ((StackAlign >> 26) - 1);
 153 }
 154
 155
 156 /// The set of Attributes set in Attributes is converted to a
 157 /// string of equivalent mnemonics. This is, presumably, for writing out
 158 /// the mnemonics for the assembly writer.
 159 /// @brief Convert attribute bits to text
 160 std::string getAsString(Attributes Attrs);
 161 } // end namespace Attribute
 162
 163 /// This is just a pair of values to associate a set of attributes
 164 /// with an index.
 165 struct AttributeWithIndex {
 166   Attributes Attrs; ///< The attributes that are set, or'd together.
 167   unsigned Index; ///< Index of the parameter for which the attributes apply.
 168                   ///< Index 0 is used for return value attributes.
 169                   ///< Index ~0U is used for function attributes.
 170
 171   static AttributeWithIndex get(unsigned Idx, Attributes Attrs) {
 172     AttributeWithIndex P;
 173     P.Index = Idx;
 174     P.Attrs = Attrs;
 175     return P;
 176   }
 177 };
 178
 179 //===----------------------------------------------------------------------===//
 180 // AttrListPtr Smart Pointer
 181 //===----------------------------------------------------------------------===//
 182
 183 class AttributeListImpl;
 184
 185 /// AttrListPtr - This class manages the ref count for the opaque
 186 /// AttributeListImpl object and provides accessors for it.
 187 class AttrListPtr {
 188   /// AttrList - The attributes that we are managing.  This can be null
 189   /// to represent the empty attributes list.
 190   AttributeListImpl *AttrList;
 191 public:
 192   AttrListPtr() : AttrList(0) {}
 193   AttrListPtr(const AttrListPtr &P);
 194   const AttrListPtr &operator=(const AttrListPtr &RHS);
 195   ~AttrListPtr();
 196
 197   //===--------------------------------------------------------------------===//
 198   // Attribute List Construction and Mutation
 199   //===--------------------------------------------------------------------===//
 200
 201   /// get - Return a Attributes list with the specified parameter in it.
 202   static AttrListPtr get(const AttributeWithIndex *Attr, unsigned NumAttrs);
 203
 204   /// get - Return a Attribute list with the parameters specified by the
 205   /// consecutive random access iterator range.
 206   template <typename Iter>
 207   static AttrListPtr get(const Iter &I, const Iter &E) {
 208     if (I == E) return AttrListPtr();  // Empty list.
 209     return get(&*I, static_cast<unsigned>(E-I));
 210   }
 211
 212   /// addAttr - Add the specified attribute at the specified index to this
 213   /// attribute list.  Since attribute lists are immutable, this
 214   /// returns the new list.
 215   AttrListPtr addAttr(unsigned Idx, Attributes Attrs) const;
 216
 217   /// removeAttr - Remove the specified attribute at the specified index from
 218   /// this attribute list.  Since attribute lists are immutable, this
 219   /// returns the new list.
 220   AttrListPtr removeAttr(unsigned Idx, Attributes Attrs) const;
 221
 222   //===--------------------------------------------------------------------===//
 223   // Attribute List Accessors
 224   //===--------------------------------------------------------------------===//
 225   /// getParamAttributes - The attributes for the specified index are
 226   /// returned.
 227   Attributes getParamAttributes(unsigned Idx) const {
 228     assert (Idx && Idx != ~0U && "Invalid parameter index!");
 229     return getAttributes(Idx);
 230   }
 231
 232   /// getRetAttributes - The attributes for the ret value are
 233   /// returned.
 234   Attributes getRetAttributes() const {
 235     return getAttributes(0);
 236   }
 237
 238   /// getFnAttributes - The function attributes are returned.
 239   Attributes getFnAttributes() const {
 240     return getAttributes(~0U);
 241   }
 242
 243   /// paramHasAttr - Return true if the specified parameter index has the
 244   /// specified attribute set.
 245   bool paramHasAttr(unsigned Idx, Attributes Attr) const {
 246     return (getAttributes(Idx) & Attr) != 0;
 247   }
 248
 249   /// getParamAlignment - Return the alignment for the specified function
 250   /// parameter.
 251   unsigned getParamAlignment(unsigned Idx) const {
 252     return Attribute::getAlignmentFromAttrs(getAttributes(Idx));
 253   }
 254
 255   /// hasAttrSomewhere - Return true if the specified attribute is set for at
 256   /// least one parameter or for the return value.
 257   bool hasAttrSomewhere(Attributes Attr) const;
 258
 259   /// operator==/!= - Provide equality predicates.
 260   bool operator==(const AttrListPtr &RHS) const
 261   { return AttrList == RHS.AttrList; }
 262   bool operator!=(const AttrListPtr &RHS) const
 263   { return AttrList != RHS.AttrList; }
 264
 265   void dump() const;
 266
 267   //===--------------------------------------------------------------------===//
 268   // Attribute List Introspection
 269   //===--------------------------------------------------------------------===//
 270
 271   /// getRawPointer - Return a raw pointer that uniquely identifies this
 272   /// attribute list.
 273   void *getRawPointer() const {
 274     return AttrList;
 275   }
 276
 277   // Attributes are stored as a dense set of slots, where there is one
 278   // slot for each argument that has an attribute.  This allows walking over the
 279   // dense set instead of walking the sparse list of attributes.
 280
 281   /// isEmpty - Return true if there are no attributes.
 282   ///
 283   bool isEmpty() const {
 284     return AttrList == 0;
 285   }
 286
 287   /// getNumSlots - Return the number of slots used in this attribute list.
 288   /// This is the number of arguments that have an attribute set on them
 289   /// (including the function itself).
 290   unsigned getNumSlots() const;
 291
 292   /// getSlot - Return the AttributeWithIndex at the specified slot.  This
 293   /// holds a index number plus a set of attributes.
 294   const AttributeWithIndex &getSlot(unsigned Slot) const;
 295
 296 private:
 297   explicit AttrListPtr(AttributeListImpl *L);
 298
 299   /// getAttributes - The attributes for the specified index are
 300   /// returned.  Attributes for the result are denoted with Idx = 0.
 301   Attributes getAttributes(unsigned Idx) const;
 302
 303 };
 304
 305 } // End llvm namespace
 306
 307 #endif