Attributes.h revision 60507d53e7e8e6b0c537675f68204a93c3033de7 
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/// \file
11/// \brief This file contains the simple types necessary to represent the
12/// attributes associated with functions and their calls.
13///
14//===----------------------------------------------------------------------===//
15
16#ifndef LLVM_ATTRIBUTES_H
17#define LLVM_ATTRIBUTES_H
18
19#include "llvm/ADT/ArrayRef.h"
20#include "llvm/Support/MathExtras.h"
21#include <cassert>
22#include <string>
23
24namespace llvm {
25
26class AttrBuilder;
27class AttributeImpl;
28class LLVMContext;
29class Type;
30
31//===----------------------------------------------------------------------===//
32/// \class
33/// \brief Functions, function parameters, and return types can have attributes
34/// to indicate how they should be treated by optimizations and code
35/// generation. This class represents one of those attributes. It's light-weight
36/// and should be passed around by-value.
37class Attribute {
38public:
39  /// This enumeration lists the attributes that can be associated with
40  /// parameters, function results or the function itself.
41  ///
42  /// Note: uwtable is about the ABI or the user mandating an entry in the
43  /// unwind table. The nounwind attribute is about an exception passing by the
44  /// function.
45  ///
46  /// In a theoretical system that uses tables for profiling and sjlj for
47  /// exceptions, they would be fully independent. In a normal system that uses
48  /// tables for both, the semantics are:
49  ///
50  /// nil                = Needs an entry because an exception might pass by.
51  /// nounwind           = No need for an entry
52  /// uwtable            = Needs an entry because the ABI says so and because
53  ///                      an exception might pass by.
54  /// uwtable + nounwind = Needs an entry because the ABI says so.
55
56  enum AttrKind {
57    // IR-Level Attributes
58    None,                  ///< No attributes have been set
59    AddressSafety,         ///< Address safety checking is on.
60    Alignment,             ///< Alignment of parameter (5 bits)
61                           ///< stored as log2 of alignment with +1 bias
62                           ///< 0 means unaligned (different from align(1))
63    AlwaysInline,          ///< inline=always
64    ByVal,                 ///< Pass structure by value
65    InlineHint,            ///< Source said inlining was desirable
66    InReg,                 ///< Force argument to be passed in register
67    MinSize,               ///< Function must be optimized for size first
68    Naked,                 ///< Naked function
69    Nest,                  ///< Nested function static chain
70    NoAlias,               ///< Considered to not alias after call
71    NoCapture,             ///< Function creates no aliases of pointer
72    NoDuplicate,           ///< Call cannot be duplicated
73    NoImplicitFloat,       ///< Disable implicit floating point insts
74    NoInline,              ///< inline=never
75    NonLazyBind,           ///< Function is called early and/or
76                           ///< often, so lazy binding isn't worthwhile
77    NoRedZone,             ///< Disable redzone
78    NoReturn,              ///< Mark the function as not returning
79    NoUnwind,              ///< Function doesn't unwind stack
80    OptimizeForSize,       ///< opt_size
81    ReadNone,              ///< Function does not access memory
82    ReadOnly,              ///< Function only reads from memory
83    ReturnsTwice,          ///< Function can return twice
84    SExt,                  ///< Sign extended before/after call
85    StackAlignment,        ///< Alignment of stack for function (3 bits)
86                           ///< stored as log2 of alignment with +1 bias 0
87                           ///< means unaligned (different from
88                           ///< alignstack=(1))
89    StackProtect,          ///< Stack protection.
90    StackProtectReq,       ///< Stack protection required.
91    StructRet,             ///< Hidden pointer to structure to return
92    UWTable,               ///< Function must be in a unwind table
93    ZExt                   ///< Zero extended before/after call
94  };
95private:
96  AttributeImpl *pImpl;
97  Attribute(AttributeImpl *A) : pImpl(A) {}
98public:
99  Attribute() : pImpl(0) {}
100
101  /// \brief Return a uniquified Attribute object. This takes the uniquified
102  /// value from the Builder and wraps it in the Attribute class.
103  static Attribute get(LLVMContext &Context, ArrayRef<AttrKind> Vals);
104  static Attribute get(LLVMContext &Context, AttrBuilder &B);
105
106  /// \brief Return true if the attribute is present.
107  bool hasAttribute(AttrKind Val) const;
108
109  /// \brief Return true if attributes exist
110  bool hasAttributes() const;
111
112  /// \brief Returns the alignment field of an attribute as a byte alignment
113  /// value.
114  unsigned getAlignment() const;
115
116  /// \brief Returns the stack alignment field of an attribute as a byte
117  /// alignment value.
118  unsigned getStackAlignment() const;
119
120  /// \brief Equality and non-equality query methods.
121  bool operator==(AttrKind K) const;
122  bool operator!=(AttrKind K) const;
123
124  // FIXME: Remove these 'operator' methods.
125  bool operator==(const Attribute &A) const {
126    return pImpl == A.pImpl;
127  }
128  bool operator!=(const Attribute &A) const {
129    return pImpl != A.pImpl;
130  }
131
132  uint64_t getBitMask() const;
133
134  /// \brief Which attributes cannot be applied to a type.
135  static Attribute typeIncompatible(Type *Ty);
136
137  /// \brief This returns an integer containing an encoding of all the LLVM
138  /// attributes found in the given attribute bitset.  Any change to this
139  /// encoding is a breaking change to bitcode compatibility.
140  static uint64_t encodeLLVMAttributesForBitcode(Attribute Attrs);
141
142  /// \brief This returns an attribute bitset containing the LLVM attributes
143  /// that have been decoded from the given integer.  This function must stay in
144  /// sync with 'encodeLLVMAttributesForBitcode'.
145  static Attribute decodeLLVMAttributesForBitcode(LLVMContext &C,
146                                                  uint64_t EncodedAttrs);
147
148  /// \brief The Attribute is converted to a string of equivalent mnemonic. This
149  /// is, presumably, for writing out the mnemonics for the assembly writer.
150  std::string getAsString() const;
151};
152
153//===----------------------------------------------------------------------===//
154/// \class
155/// \brief This class is used in conjunction with the Attribute::get method to
156/// create an Attribute object. The object itself is uniquified. The Builder's
157/// value, however, is not. So this can be used as a quick way to test for
158/// equality, presence of attributes, etc.
159class AttrBuilder {
160  uint64_t Bits;
161public:
162  AttrBuilder() : Bits(0) {}
163  explicit AttrBuilder(uint64_t B) : Bits(B) {}
164  AttrBuilder(const Attribute &A) : Bits(A.getBitMask()) {}
165
166  void clear() { Bits = 0; }
167
168  /// \brief Add an attribute to the builder.
169  AttrBuilder &addAttribute(Attribute::AttrKind Val);
170
171  /// \brief Remove an attribute from the builder.
172  AttrBuilder &removeAttribute(Attribute::AttrKind Val);
173
174  /// \brief Add the attributes from A to the builder.
175  AttrBuilder &addAttributes(const Attribute &A);
176
177  /// \brief Remove the attributes from A from the builder.
178  AttrBuilder &removeAttributes(const Attribute &A);
179
180  /// \brief Return true if the builder has the specified attribute.
181  bool contains(Attribute::AttrKind A) const;
182
183  /// \brief Return true if the builder has IR-level attributes.
184  bool hasAttributes() const;
185
186  /// \brief Return true if the builder has any attribute that's in the
187  /// specified attribute.
188  bool hasAttributes(const Attribute &A) const;
189
190  /// \brief Return true if the builder has an alignment attribute.
191  bool hasAlignmentAttr() const;
192
193  /// \brief Retrieve the alignment attribute, if it exists.
194  uint64_t getAlignment() const;
195
196  /// \brief Retrieve the stack alignment attribute, if it exists.
197  uint64_t getStackAlignment() const;
198
199  /// \brief This turns an int alignment (which must be a power of 2) into the
200  /// form used internally in Attribute.
201  AttrBuilder &addAlignmentAttr(unsigned Align);
202
203  /// \brief This turns an int stack alignment (which must be a power of 2) into
204  /// the form used internally in Attribute.
205  AttrBuilder &addStackAlignmentAttr(unsigned Align);
206
207  /// \brief Add the raw value to the internal representation.
208  ///
209  /// N.B. This should be used ONLY for decoding LLVM bitcode!
210  AttrBuilder &addRawValue(uint64_t Val);
211
212  /// \brief Remove attributes that are used on functions only.
213  void removeFunctionOnlyAttrs() {
214    removeAttribute(Attribute::NoReturn)
215      .removeAttribute(Attribute::NoUnwind)
216      .removeAttribute(Attribute::ReadNone)
217      .removeAttribute(Attribute::ReadOnly)
218      .removeAttribute(Attribute::NoInline)
219      .removeAttribute(Attribute::AlwaysInline)
220      .removeAttribute(Attribute::OptimizeForSize)
221      .removeAttribute(Attribute::StackProtect)
222      .removeAttribute(Attribute::StackProtectReq)
223      .removeAttribute(Attribute::NoRedZone)
224      .removeAttribute(Attribute::NoImplicitFloat)
225      .removeAttribute(Attribute::Naked)
226      .removeAttribute(Attribute::InlineHint)
227      .removeAttribute(Attribute::StackAlignment)
228      .removeAttribute(Attribute::UWTable)
229      .removeAttribute(Attribute::NonLazyBind)
230      .removeAttribute(Attribute::ReturnsTwice)
231      .removeAttribute(Attribute::AddressSafety)
232      .removeAttribute(Attribute::MinSize)
233      .removeAttribute(Attribute::NoDuplicate);
234  }
235
236  uint64_t getBitMask() const { return Bits; }
237
238  bool operator==(const AttrBuilder &B) {
239    return Bits == B.Bits;
240  }
241  bool operator!=(const AttrBuilder &B) {
242    return Bits != B.Bits;
243  }
244};
245
246//===----------------------------------------------------------------------===//
247/// \class
248/// \brief This is just a pair of values to associate a set of attributes with
249/// an index.
250struct AttributeWithIndex {
251  Attribute Attrs;  ///< The attributes that are set, or'd together.
252  unsigned Index;   ///< Index of the parameter for which the attributes apply.
253                    ///< Index 0 is used for return value attributes.
254                    ///< Index ~0U is used for function attributes.
255
256  static AttributeWithIndex get(LLVMContext &C, unsigned Idx,
257                                ArrayRef<Attribute::AttrKind> Attrs) {
258    return get(Idx, Attribute::get(C, Attrs));
259  }
260  static AttributeWithIndex get(unsigned Idx, Attribute Attrs) {
261    AttributeWithIndex P;
262    P.Index = Idx;
263    P.Attrs = Attrs;
264    return P;
265  }
266};
267
268//===----------------------------------------------------------------------===//
269// AttributeSet Smart Pointer
270//===----------------------------------------------------------------------===//
271
272class AttributeSetImpl;
273
274//===----------------------------------------------------------------------===//
275/// \class
276/// \brief This class manages the ref count for the opaque AttributeSetImpl
277/// object and provides accessors for it.
278class AttributeSet {
279public:
280  enum AttrIndex {
281    ReturnIndex = 0U,
282    FunctionIndex = ~0U
283  };
284private:
285  /// \brief The attributes that we are managing.  This can be null to represent
286  /// the empty attributes list.
287  AttributeSetImpl *AttrList;
288
289  /// \brief The attributes for the specified index are returned.  Attributes
290  /// for the result are denoted with Idx = 0.
291  Attribute getAttributes(unsigned Idx) const;
292
293  explicit AttributeSet(AttributeSetImpl *LI) : AttrList(LI) {}
294public:
295  AttributeSet() : AttrList(0) {}
296  AttributeSet(const AttributeSet &P) : AttrList(P.AttrList) {}
297  const AttributeSet &operator=(const AttributeSet &RHS);
298
299  //===--------------------------------------------------------------------===//
300  // Attribute List Construction and Mutation
301  //===--------------------------------------------------------------------===//
302
303  /// \brief Return an AttributeSet with the specified parameters in it.
304  static AttributeSet get(LLVMContext &C, ArrayRef<AttributeWithIndex> Attrs);
305
306  /// \brief Add the specified attribute at the specified index to this
307  /// attribute list.  Since attribute lists are immutable, this returns the new
308  /// list.
309  AttributeSet addAttr(LLVMContext &C, unsigned Idx, Attribute Attrs) const;
310
311  /// \brief Remove the specified attribute at the specified index from this
312  /// attribute list.  Since attribute lists are immutable, this returns the new
313  /// list.
314  AttributeSet removeAttr(LLVMContext &C, unsigned Idx, Attribute Attrs) const;
315
316  //===--------------------------------------------------------------------===//
317  // Attribute List Accessors
318  //===--------------------------------------------------------------------===//
319
320  /// \brief The attributes for the specified index are returned.
321  Attribute getParamAttributes(unsigned Idx) const {
322    return getAttributes(Idx);
323  }
324
325  /// \brief The attributes for the ret value are returned.
326  Attribute getRetAttributes() const {
327    return getAttributes(ReturnIndex);
328  }
329
330  /// \brief The function attributes are returned.
331  Attribute getFnAttributes() const {
332    return getAttributes(FunctionIndex);
333  }
334
335  /// \brief Return the alignment for the specified function parameter.
336  unsigned getParamAlignment(unsigned Idx) const {
337    return getAttributes(Idx).getAlignment();
338  }
339
340  /// \brief Return true if the attribute exists at the given index.
341  bool hasAttribute(unsigned Index, Attribute::AttrKind Kind) const;
342
343  /// \brief Return true if attribute exists at the given index.
344  bool hasAttributes(unsigned Index) const;
345
346  /// \brief Get the stack alignment.
347  unsigned getStackAlignment(unsigned Index) const;
348
349  /// \brief Return the attributes at the index as a string.
350  std::string getAsString(unsigned Index) const;
351
352  uint64_t getBitMask(unsigned Index) const;
353
354  /// \brief Return true if the specified attribute is set for at least one
355  /// parameter or for the return value.
356  bool hasAttrSomewhere(Attribute::AttrKind Attr) const;
357
358  /// operator==/!= - Provide equality predicates.
359  bool operator==(const AttributeSet &RHS) const {
360    return AttrList == RHS.AttrList;
361  }
362  bool operator!=(const AttributeSet &RHS) const {
363    return AttrList != RHS.AttrList;
364  }
365
366  //===--------------------------------------------------------------------===//
367  // Attribute List Introspection
368  //===--------------------------------------------------------------------===//
369
370  /// \brief Return a raw pointer that uniquely identifies this attribute list.
371  void *getRawPointer() const {
372    return AttrList;
373  }
374
375  // Attributes are stored as a dense set of slots, where there is one slot for
376  // each argument that has an attribute.  This allows walking over the dense
377  // set instead of walking the sparse list of attributes.
378
379  /// \brief Return true if there are no attributes.
380  bool isEmpty() const {
381    return AttrList == 0;
382  }
383
384  /// \brief Return the number of slots used in this attribute list.  This is
385  /// the number of arguments that have an attribute set on them (including the
386  /// function itself).
387  unsigned getNumSlots() const;
388
389  /// \brief Return the AttributeWithIndex at the specified slot.  This holds a
390  /// index number plus a set of attributes.
391  const AttributeWithIndex &getSlot(unsigned Slot) const;
392
393  void dump() const;
394};
395
396} // end llvm namespace
397
398#endif
399