Attributes.h revision 1bbd644301ed4d8a7efd4ceb15f71c56fa914f28 
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/ADT/DenseSet.h"
21#include "llvm/Support/MathExtras.h"
22#include <cassert>
23#include <string>
24
25namespace llvm {
26
27class AttrBuilder;
28class AttributeImpl;
29class LLVMContext;
30class Type;
31
32//===----------------------------------------------------------------------===//
33/// \class
34/// \brief Functions, function parameters, and return types can have attributes
35/// to indicate how they should be treated by optimizations and code
36/// generation. This class represents one of those attributes. It's light-weight
37/// and should be passed around by-value.
38class Attribute {
39public:
40  /// This enumeration lists the attributes that can be associated with
41  /// parameters, function results or the function itself.
42  ///
43  /// Note: uwtable is about the ABI or the user mandating an entry in the
44  /// unwind table. The nounwind attribute is about an exception passing by the
45  /// function.
46  ///
47  /// In a theoretical system that uses tables for profiling and sjlj for
48  /// exceptions, they would be fully independent. In a normal system that uses
49  /// tables for both, the semantics are:
50  ///
51  /// nil                = Needs an entry because an exception might pass by.
52  /// nounwind           = No need for an entry
53  /// uwtable            = Needs an entry because the ABI says so and because
54  ///                      an exception might pass by.
55  /// uwtable + nounwind = Needs an entry because the ABI says so.
56
57  enum AttrKind {
58    // IR-Level Attributes
59    None,                  ///< No attributes have been set
60    AddressSafety,         ///< Address safety checking is on.
61    Alignment,             ///< Alignment of parameter (5 bits)
62                           ///< stored as log2 of alignment with +1 bias
63                           ///< 0 means unaligned (different from align(1))
64    AlwaysInline,          ///< inline=always
65    ByVal,                 ///< Pass structure by value
66    InlineHint,            ///< Source said inlining was desirable
67    InReg,                 ///< Force argument to be passed in register
68    MinSize,               ///< Function must be optimized for size first
69    Naked,                 ///< Naked function
70    Nest,                  ///< Nested function static chain
71    NoAlias,               ///< Considered to not alias after call
72    NoCapture,             ///< Function creates no aliases of pointer
73    NoDuplicate,           ///< Call cannot be duplicated
74    NoImplicitFloat,       ///< Disable implicit floating point insts
75    NoInline,              ///< inline=never
76    NonLazyBind,           ///< Function is called early and/or
77                           ///< often, so lazy binding isn't worthwhile
78    NoRedZone,             ///< Disable redzone
79    NoReturn,              ///< Mark the function as not returning
80    NoUnwind,              ///< Function doesn't unwind stack
81    OptimizeForSize,       ///< opt_size
82    ReadNone,              ///< Function does not access memory
83    ReadOnly,              ///< Function only reads from memory
84    ReturnsTwice,          ///< Function can return twice
85    SExt,                  ///< Sign extended before/after call
86    StackAlignment,        ///< Alignment of stack for function (3 bits)
87                           ///< stored as log2 of alignment with +1 bias 0
88                           ///< means unaligned (different from
89                           ///< alignstack=(1))
90    StackProtect,          ///< Stack protection.
91    StackProtectReq,       ///< Stack protection required.
92    StructRet,             ///< Hidden pointer to structure to return
93    UWTable,               ///< Function must be in a unwind table
94    ZExt,                  ///< Zero extended before/after call
95
96    EndAttrKinds           ///< Sentinal value useful for loops
97  };
98private:
99  AttributeImpl *pImpl;
100  Attribute(AttributeImpl *A) : pImpl(A) {}
101public:
102  Attribute() : pImpl(0) {}
103
104  /// \brief Return a uniquified Attribute object. This takes the uniquified
105  /// value from the Builder and wraps it in the Attribute class.
106  static Attribute get(LLVMContext &Context, ArrayRef<AttrKind> Vals);
107  static Attribute get(LLVMContext &Context, AttrBuilder &B);
108
109  /// \brief Return true if the attribute is present.
110  bool hasAttribute(AttrKind Val) const;
111
112  /// \brief Return true if attributes exist
113  bool hasAttributes() const;
114
115  /// \brief Returns the alignment field of an attribute as a byte alignment
116  /// value.
117  unsigned getAlignment() const;
118
119  /// \brief Set the alignment field of an attribute.
120  void setAlignment(unsigned Align);
121
122  /// \brief Returns the stack alignment field of an attribute as a byte
123  /// alignment value.
124  unsigned getStackAlignment() const;
125
126  /// \brief Set the stack alignment field of an attribute.
127  void setStackAlignment(unsigned Align);
128
129  /// \brief Equality and non-equality query methods.
130  bool operator==(AttrKind K) const;
131  bool operator!=(AttrKind K) const;
132
133  // FIXME: Remove these 'operator' methods.
134  bool operator==(const Attribute &A) const {
135    return pImpl == A.pImpl;
136  }
137  bool operator!=(const Attribute &A) const {
138    return pImpl != A.pImpl;
139  }
140
141  uint64_t getBitMask() const;
142
143  /// \brief Which attributes cannot be applied to a type.
144  static Attribute typeIncompatible(Type *Ty);
145
146  /// \brief This returns an integer containing an encoding of all the LLVM
147  /// attributes found in the given attribute bitset.  Any change to this
148  /// encoding is a breaking change to bitcode compatibility.
149  static uint64_t encodeLLVMAttributesForBitcode(Attribute Attrs);
150
151  /// \brief This returns an attribute bitset containing the LLVM attributes
152  /// that have been decoded from the given integer.  This function must stay in
153  /// sync with 'encodeLLVMAttributesForBitcode'.
154  static Attribute decodeLLVMAttributesForBitcode(LLVMContext &C,
155                                                  uint64_t EncodedAttrs);
156
157  /// \brief The Attribute is converted to a string of equivalent mnemonic. This
158  /// is, presumably, for writing out the mnemonics for the assembly writer.
159  std::string getAsString() const;
160};
161
162//===----------------------------------------------------------------------===//
163/// \class
164/// \brief Provide DenseMapInfo for Attribute::AttrKinds. This is used by
165/// AttrBuilder.
166template<> struct DenseMapInfo<Attribute::AttrKind> {
167  static inline Attribute::AttrKind getEmptyKey() {
168    return Attribute::AttrKind(~0U);
169  }
170  static inline Attribute::AttrKind getTombstoneKey() {
171    return Attribute::AttrKind(~0U - 1);
172  }
173  static unsigned getHashValue(const Attribute::AttrKind &Val) {
174    return Val * 37U;
175  }
176  static bool isEqual(const Attribute::AttrKind &LHS,
177                      const Attribute::AttrKind &RHS) {
178    return LHS == RHS;
179  }
180};
181
182//===----------------------------------------------------------------------===//
183/// \class
184/// \brief This class is used in conjunction with the Attribute::get method to
185/// create an Attribute object. The object itself is uniquified. The Builder's
186/// value, however, is not. So this can be used as a quick way to test for
187/// equality, presence of attributes, etc.
188class AttrBuilder {
189  DenseSet<Attribute::AttrKind> Attrs;
190  uint64_t Alignment;
191  uint64_t StackAlignment;
192public:
193  AttrBuilder() : Alignment(0), StackAlignment(0) {}
194  explicit AttrBuilder(uint64_t B) : Alignment(0), StackAlignment(0) {
195    addRawValue(B);
196  }
197  AttrBuilder(const Attribute &A) : Alignment(0), StackAlignment(0) {
198    addAttributes(A);
199  }
200
201  void clear();
202
203  /// \brief Add an attribute to the builder.
204  AttrBuilder &addAttribute(Attribute::AttrKind Val);
205
206  /// \brief Remove an attribute from the builder.
207  AttrBuilder &removeAttribute(Attribute::AttrKind Val);
208
209  /// \brief Add the attributes from A to the builder.
210  AttrBuilder &addAttributes(const Attribute &A);
211
212  /// \brief Remove the attributes from A from the builder.
213  AttrBuilder &removeAttributes(const Attribute &A);
214
215  /// \brief Return true if the builder has the specified attribute.
216  bool contains(Attribute::AttrKind A) const;
217
218  /// \brief Return true if the builder has IR-level attributes.
219  bool hasAttributes() const;
220
221  /// \brief Return true if the builder has any attribute that's in the
222  /// specified attribute.
223  bool hasAttributes(const Attribute &A) const;
224
225  /// \brief Return true if the builder has an alignment attribute.
226  bool hasAlignmentAttr() const;
227
228  /// \brief Retrieve the alignment attribute, if it exists.
229  uint64_t getAlignment() const { return Alignment; }
230
231  /// \brief Retrieve the stack alignment attribute, if it exists.
232  uint64_t getStackAlignment() const { return StackAlignment; }
233
234  /// \brief This turns an int alignment (which must be a power of 2) into the
235  /// form used internally in Attribute.
236  AttrBuilder &addAlignmentAttr(unsigned Align);
237
238  /// \brief This turns an int stack alignment (which must be a power of 2) into
239  /// the form used internally in Attribute.
240  AttrBuilder &addStackAlignmentAttr(unsigned Align);
241
242  typedef DenseSet<Attribute::AttrKind>::iterator       iterator;
243  typedef DenseSet<Attribute::AttrKind>::const_iterator const_iterator;
244
245  iterator begin() { return Attrs.begin(); }
246  iterator end()   { return Attrs.end(); }
247
248  const_iterator begin() const { return Attrs.begin(); }
249  const_iterator end() const   { return Attrs.end(); }
250
251  /// \brief Add the raw value to the internal representation.
252  ///
253  /// N.B. This should be used ONLY for decoding LLVM bitcode!
254  AttrBuilder &addRawValue(uint64_t Val);
255
256  /// \brief Remove attributes that are used on functions only.
257  void removeFunctionOnlyAttrs() {
258    removeAttribute(Attribute::NoReturn)
259      .removeAttribute(Attribute::NoUnwind)
260      .removeAttribute(Attribute::ReadNone)
261      .removeAttribute(Attribute::ReadOnly)
262      .removeAttribute(Attribute::NoInline)
263      .removeAttribute(Attribute::AlwaysInline)
264      .removeAttribute(Attribute::OptimizeForSize)
265      .removeAttribute(Attribute::StackProtect)
266      .removeAttribute(Attribute::StackProtectReq)
267      .removeAttribute(Attribute::NoRedZone)
268      .removeAttribute(Attribute::NoImplicitFloat)
269      .removeAttribute(Attribute::Naked)
270      .removeAttribute(Attribute::InlineHint)
271      .removeAttribute(Attribute::StackAlignment)
272      .removeAttribute(Attribute::UWTable)
273      .removeAttribute(Attribute::NonLazyBind)
274      .removeAttribute(Attribute::ReturnsTwice)
275      .removeAttribute(Attribute::AddressSafety)
276      .removeAttribute(Attribute::MinSize)
277      .removeAttribute(Attribute::NoDuplicate);
278  }
279
280  uint64_t getBitMask() const;
281
282  bool operator==(const AttrBuilder &B);
283  bool operator!=(const AttrBuilder &B) {
284    return !(*this == B);
285  }
286};
287
288//===----------------------------------------------------------------------===//
289/// \class
290/// \brief This is just a pair of values to associate a set of attributes with
291/// an index.
292struct AttributeWithIndex {
293  Attribute Attrs;  ///< The attributes that are set, or'd together.
294  unsigned Index;   ///< Index of the parameter for which the attributes apply.
295                    ///< Index 0 is used for return value attributes.
296                    ///< Index ~0U is used for function attributes.
297
298  static AttributeWithIndex get(LLVMContext &C, unsigned Idx,
299                                ArrayRef<Attribute::AttrKind> Attrs) {
300    return get(Idx, Attribute::get(C, Attrs));
301  }
302  static AttributeWithIndex get(unsigned Idx, Attribute Attrs) {
303    AttributeWithIndex P;
304    P.Index = Idx;
305    P.Attrs = Attrs;
306    return P;
307  }
308};
309
310//===----------------------------------------------------------------------===//
311// AttributeSet Smart Pointer
312//===----------------------------------------------------------------------===//
313
314class AttributeSetImpl;
315
316//===----------------------------------------------------------------------===//
317/// \class
318/// \brief This class manages the ref count for the opaque AttributeSetImpl
319/// object and provides accessors for it.
320class AttributeSet {
321public:
322  enum AttrIndex {
323    ReturnIndex = 0U,
324    FunctionIndex = ~0U
325  };
326private:
327  /// \brief The attributes that we are managing.  This can be null to represent
328  /// the empty attributes list.
329  AttributeSetImpl *AttrList;
330
331  /// \brief The attributes for the specified index are returned.  Attributes
332  /// for the result are denoted with Idx = 0.
333  Attribute getAttributes(unsigned Idx) const;
334
335  explicit AttributeSet(AttributeSetImpl *LI) : AttrList(LI) {}
336public:
337  AttributeSet() : AttrList(0) {}
338  AttributeSet(const AttributeSet &P) : AttrList(P.AttrList) {}
339  const AttributeSet &operator=(const AttributeSet &RHS);
340
341  //===--------------------------------------------------------------------===//
342  // Attribute List Construction and Mutation
343  //===--------------------------------------------------------------------===//
344
345  /// \brief Return an AttributeSet with the specified parameters in it.
346  static AttributeSet get(LLVMContext &C, ArrayRef<AttributeWithIndex> Attrs);
347  static AttributeSet get(LLVMContext &C, unsigned Idx, AttrBuilder &B);
348
349  /// \brief Add the specified attribute at the specified index to this
350  /// attribute list.  Since attribute lists are immutable, this returns the new
351  /// list.
352  AttributeSet addAttr(LLVMContext &C, unsigned Idx, Attribute Attrs) const;
353
354  /// \brief Remove the specified attribute at the specified index from this
355  /// attribute list.  Since attribute lists are immutable, this returns the new
356  /// list.
357  AttributeSet removeAttr(LLVMContext &C, unsigned Idx, Attribute Attrs) const;
358
359  //===--------------------------------------------------------------------===//
360  // Attribute List Accessors
361  //===--------------------------------------------------------------------===//
362
363  /// \brief The attributes for the specified index are returned.
364  Attribute getParamAttributes(unsigned Idx) const {
365    return getAttributes(Idx);
366  }
367
368  /// \brief The attributes for the ret value are returned.
369  Attribute getRetAttributes() const {
370    return getAttributes(ReturnIndex);
371  }
372
373  /// \brief The function attributes are returned.
374  Attribute getFnAttributes() const {
375    return getAttributes(FunctionIndex);
376  }
377
378  /// \brief Return the alignment for the specified function parameter.
379  unsigned getParamAlignment(unsigned Idx) const {
380    return getAttributes(Idx).getAlignment();
381  }
382
383  /// \brief Return true if the attribute exists at the given index.
384  bool hasAttribute(unsigned Index, Attribute::AttrKind Kind) const;
385
386  /// \brief Return true if attribute exists at the given index.
387  bool hasAttributes(unsigned Index) const;
388
389  /// \brief Get the stack alignment.
390  unsigned getStackAlignment(unsigned Index) const;
391
392  /// \brief Return the attributes at the index as a string.
393  std::string getAsString(unsigned Index) const;
394
395  uint64_t getBitMask(unsigned Index) const;
396
397  /// \brief Return true if the specified attribute is set for at least one
398  /// parameter or for the return value.
399  bool hasAttrSomewhere(Attribute::AttrKind Attr) const;
400
401  /// operator==/!= - Provide equality predicates.
402  bool operator==(const AttributeSet &RHS) const {
403    return AttrList == RHS.AttrList;
404  }
405  bool operator!=(const AttributeSet &RHS) const {
406    return AttrList != RHS.AttrList;
407  }
408
409  //===--------------------------------------------------------------------===//
410  // Attribute List Introspection
411  //===--------------------------------------------------------------------===//
412
413  /// \brief Return a raw pointer that uniquely identifies this attribute list.
414  void *getRawPointer() const {
415    return AttrList;
416  }
417
418  // Attributes are stored as a dense set of slots, where there is one slot for
419  // each argument that has an attribute.  This allows walking over the dense
420  // set instead of walking the sparse list of attributes.
421
422  /// \brief Return true if there are no attributes.
423  bool isEmpty() const {
424    return AttrList == 0;
425  }
426
427  /// \brief Return the number of slots used in this attribute list.  This is
428  /// the number of arguments that have an attribute set on them (including the
429  /// function itself).
430  unsigned getNumSlots() const;
431
432  /// \brief Return the AttributeWithIndex at the specified slot.  This holds a
433  /// index number plus a set of attributes.
434  const AttributeWithIndex &getSlot(unsigned Slot) const;
435
436  void dump() const;
437};
438
439} // end llvm namespace
440
441#endif
442