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
22namespace llvm {
23class Type;
24
25/// Attributes - A bitset of attributes.
26typedef unsigned Attributes;
27
28namespace 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
36const Attributes None      = 0;     ///< No attributes have been set
37const Attributes ZExt      = 1<<0;  ///< Zero extended before/after call
38const Attributes SExt      = 1<<1;  ///< Sign extended before/after call
39const Attributes NoReturn  = 1<<2;  ///< Mark the function as not returning
40const Attributes InReg     = 1<<3;  ///< Force argument to be passed in register
41const Attributes StructRet = 1<<4;  ///< Hidden pointer to structure to return
42const Attributes NoUnwind  = 1<<5;  ///< Function doesn't unwind stack
43const Attributes NoAlias   = 1<<6;  ///< Considered to not alias after call
44const Attributes ByVal     = 1<<7;  ///< Pass structure by value
45const Attributes Nest      = 1<<8;  ///< Nested function static chain
46const Attributes ReadNone  = 1<<9;  ///< Function does not access memory
47const Attributes ReadOnly  = 1<<10; ///< Function only reads from memory
48const Attributes NoInline        = 1<<11; ///< inline=never
49const Attributes AlwaysInline    = 1<<12; ///< inline=always
50const Attributes OptimizeForSize = 1<<13; ///< opt_size
51const Attributes StackProtect    = 1<<14; ///< Stack protection.
52const Attributes StackProtectReq = 1<<15; ///< Stack protection required.
53const 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
56const Attributes NoCapture = 1<<21; ///< Function creates no aliases of pointer
57const Attributes NoRedZone = 1<<22; /// disable redzone
58const Attributes NoImplicitFloat = 1<<23; /// disable implicit floating point
59                                          /// instructions.
60const Attributes Naked           = 1<<24; ///< Naked function
61const Attributes InlineHint      = 1<<25; ///< source said inlining was
62                                          ///desirable
63const 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))
68const Attributes ReturnsTwice    = 1<<29; ///< Function can return twice
69const Attributes UWTable     = 1<<30;     ///< Function must be in a unwind
70                                          ///table
71const Attributes NonLazyBind = 1U<<31;    ///< Function is called early and/or
72                                          ///  often, so lazy binding isn't
73                                          ///  worthwhile.
74
75/// Note that uwtable is about the ABI or the user mandating an entry in the
76/// unwind table. The nounwind attribute is about an exception passing by the
77/// function.
78/// In a theoretical system that uses tables for profiling and sjlj for
79/// exceptions, they would be fully independent. In a normal system that
80/// uses tables for both, the semantics are:
81/// nil                = Needs an entry because an exception might pass by.
82/// nounwind           = No need for an entry
83/// uwtable            = Needs an entry because the ABI says so and because
84///                      an exception might pass by.
85/// uwtable + nounwind = Needs an entry because the ABI says so.
86
87/// @brief Attributes that only apply to function parameters.
88const Attributes ParameterOnly = ByVal | Nest | StructRet | NoCapture;
89
90/// @brief Attributes that may be applied to the function itself.  These cannot
91/// be used on return values or function parameters.
92const Attributes FunctionOnly = NoReturn | NoUnwind | ReadNone | ReadOnly |
93  NoInline | AlwaysInline | OptimizeForSize | StackProtect | StackProtectReq |
94  NoRedZone | NoImplicitFloat | Naked | InlineHint | StackAlignment |
95  UWTable | NonLazyBind | ReturnsTwice;
96
97/// @brief Parameter attributes that do not apply to vararg call arguments.
98const Attributes VarArgsIncompatible = StructRet;
99
100/// @brief Attributes that are mutually incompatible.
101const Attributes MutuallyIncompatible[4] = {
102  ByVal | InReg | Nest | StructRet,
103  ZExt  | SExt,
104  ReadNone | ReadOnly,
105  NoInline | AlwaysInline
106};
107
108/// @brief Which attributes cannot be applied to a type.
109Attributes typeIncompatible(Type *Ty);
110
111/// This turns an int alignment (a power of 2, normally) into the
112/// form used internally in Attributes.
113inline Attributes constructAlignmentFromInt(unsigned i) {
114  // Default alignment, allow the target to define how to align it.
115  if (i == 0)
116    return 0;
117
118  assert(isPowerOf2_32(i) && "Alignment must be a power of two.");
119  assert(i <= 0x40000000 && "Alignment too large.");
120  return (Log2_32(i)+1) << 16;
121}
122
123/// This returns the alignment field of an attribute as a byte alignment value.
124inline unsigned getAlignmentFromAttrs(Attributes A) {
125  Attributes Align = A & Attribute::Alignment;
126  if (Align == 0)
127    return 0;
128
129  return 1U << ((Align >> 16) - 1);
130}
131
132/// This turns an int stack alignment (which must be a power of 2) into
133/// the form used internally in Attributes.
134inline Attributes constructStackAlignmentFromInt(unsigned i) {
135  // Default alignment, allow the target to define how to align it.
136  if (i == 0)
137    return 0;
138
139  assert(isPowerOf2_32(i) && "Alignment must be a power of two.");
140  assert(i <= 0x100 && "Alignment too large.");
141  return (Log2_32(i)+1) << 26;
142}
143
144/// This returns the stack alignment field of an attribute as a byte alignment
145/// value.
146inline unsigned getStackAlignmentFromAttrs(Attributes A) {
147  Attributes StackAlign = A & Attribute::StackAlignment;
148  if (StackAlign == 0)
149    return 0;
150
151  return 1U << ((StackAlign >> 26) - 1);
152}
153
154
155/// The set of Attributes set in Attributes is converted to a
156/// string of equivalent mnemonics. This is, presumably, for writing out
157/// the mnemonics for the assembly writer.
158/// @brief Convert attribute bits to text
159std::string getAsString(Attributes Attrs);
160} // end namespace Attribute
161
162/// This is just a pair of values to associate a set of attributes
163/// with an index.
164struct AttributeWithIndex {
165  Attributes Attrs; ///< The attributes that are set, or'd together.
166  unsigned Index; ///< Index of the parameter for which the attributes apply.
167                  ///< Index 0 is used for return value attributes.
168                  ///< Index ~0U is used for function attributes.
169
170  static AttributeWithIndex get(unsigned Idx, Attributes Attrs) {
171    AttributeWithIndex P;
172    P.Index = Idx;
173    P.Attrs = Attrs;
174    return P;
175  }
176};
177
178//===----------------------------------------------------------------------===//
179// AttrListPtr Smart Pointer
180//===----------------------------------------------------------------------===//
181
182class AttributeListImpl;
183
184/// AttrListPtr - This class manages the ref count for the opaque
185/// AttributeListImpl object and provides accessors for it.
186class AttrListPtr {
187  /// AttrList - The attributes that we are managing.  This can be null
188  /// to represent the empty attributes list.
189  AttributeListImpl *AttrList;
190public:
191  AttrListPtr() : AttrList(0) {}
192  AttrListPtr(const AttrListPtr &P);
193  const AttrListPtr &operator=(const AttrListPtr &RHS);
194  ~AttrListPtr();
195
196  //===--------------------------------------------------------------------===//
197  // Attribute List Construction and Mutation
198  //===--------------------------------------------------------------------===//
199
200  /// get - Return a Attributes list with the specified parameter in it.
201  static AttrListPtr get(const AttributeWithIndex *Attr, unsigned NumAttrs);
202
203  /// get - Return a Attribute list with the parameters specified by the
204  /// consecutive random access iterator range.
205  template <typename Iter>
206  static AttrListPtr get(const Iter &I, const Iter &E) {
207    if (I == E) return AttrListPtr();  // Empty list.
208    return get(&*I, static_cast<unsigned>(E-I));
209  }
210
211  /// addAttr - Add the specified attribute at the specified index to this
212  /// attribute list.  Since attribute lists are immutable, this
213  /// returns the new list.
214  AttrListPtr addAttr(unsigned Idx, Attributes Attrs) const;
215
216  /// removeAttr - Remove the specified attribute at the specified index from
217  /// this attribute list.  Since attribute lists are immutable, this
218  /// returns the new list.
219  AttrListPtr removeAttr(unsigned Idx, Attributes Attrs) const;
220
221  //===--------------------------------------------------------------------===//
222  // Attribute List Accessors
223  //===--------------------------------------------------------------------===//
224  /// getParamAttributes - The attributes for the specified index are
225  /// returned.
226  Attributes getParamAttributes(unsigned Idx) const {
227    assert (Idx && Idx != ~0U && "Invalid parameter index!");
228    return getAttributes(Idx);
229  }
230
231  /// getRetAttributes - The attributes for the ret value are
232  /// returned.
233  Attributes getRetAttributes() const {
234    return getAttributes(0);
235  }
236
237  /// getFnAttributes - The function attributes are returned.
238  Attributes getFnAttributes() const {
239    return getAttributes(~0U);
240  }
241
242  /// paramHasAttr - Return true if the specified parameter index has the
243  /// specified attribute set.
244  bool paramHasAttr(unsigned Idx, Attributes Attr) const {
245    return (getAttributes(Idx) & Attr) != 0;
246  }
247
248  /// getParamAlignment - Return the alignment for the specified function
249  /// parameter.
250  unsigned getParamAlignment(unsigned Idx) const {
251    return Attribute::getAlignmentFromAttrs(getAttributes(Idx));
252  }
253
254  /// hasAttrSomewhere - Return true if the specified attribute is set for at
255  /// least one parameter or for the return value.
256  bool hasAttrSomewhere(Attributes Attr) const;
257
258  /// operator==/!= - Provide equality predicates.
259  bool operator==(const AttrListPtr &RHS) const
260  { return AttrList == RHS.AttrList; }
261  bool operator!=(const AttrListPtr &RHS) const
262  { return AttrList != RHS.AttrList; }
263
264  void dump() const;
265
266  //===--------------------------------------------------------------------===//
267  // Attribute List Introspection
268  //===--------------------------------------------------------------------===//
269
270  /// getRawPointer - Return a raw pointer that uniquely identifies this
271  /// attribute list.
272  void *getRawPointer() const {
273    return AttrList;
274  }
275
276  // Attributes are stored as a dense set of slots, where there is one
277  // slot for each argument that has an attribute.  This allows walking over the
278  // dense set instead of walking the sparse list of attributes.
279
280  /// isEmpty - Return true if there are no attributes.
281  ///
282  bool isEmpty() const {
283    return AttrList == 0;
284  }
285
286  /// getNumSlots - Return the number of slots used in this attribute list.
287  /// This is the number of arguments that have an attribute set on them
288  /// (including the function itself).
289  unsigned getNumSlots() const;
290
291  /// getSlot - Return the AttributeWithIndex at the specified slot.  This
292  /// holds a index number plus a set of attributes.
293  const AttributeWithIndex &getSlot(unsigned Slot) const;
294
295private:
296  explicit AttrListPtr(AttributeListImpl *L);
297
298  /// getAttributes - The attributes for the specified index are
299  /// returned.  Attributes for the result are denoted with Idx = 0.
300  Attributes getAttributes(unsigned Idx) const;
301
302};
303
304} // End llvm namespace
305
306#endif
307