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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 ReturnsTwice    = 1<<29; ///< Function can return twice
69 const Attributes UWTable     = 1<<30;     ///< Function must be in a unwind
70                                           ///table
71 const 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.
88 const 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.
92 const 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.
98 const Attributes VarArgsIncompatible = StructRet;
99 
100 /// @brief Attributes that are mutually incompatible.
101 const 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.
109 Attributes typeIncompatible(Type *Ty);
110 
111 /// This turns an int alignment (a power of 2, normally) into the
112 /// form used internally in Attributes.
constructAlignmentFromInt(unsigned i)113 inline 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.
getAlignmentFromAttrs(Attributes A)124 inline 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.
constructStackAlignmentFromInt(unsigned i)134 inline 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.
getStackAlignmentFromAttrs(Attributes A)146 inline 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
159 std::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.
164 struct 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 
getAttributeWithIndex170   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 
182 class AttributeListImpl;
183 
184 /// AttrListPtr - This class manages the ref count for the opaque
185 /// AttributeListImpl object and provides accessors for it.
186 class AttrListPtr {
187   /// AttrList - The attributes that we are managing.  This can be null
188   /// to represent the empty attributes list.
189   AttributeListImpl *AttrList;
190 public:
AttrListPtr()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>
get(const Iter & I,const Iter & E)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.
getParamAttributes(unsigned Idx)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.
getRetAttributes()233   Attributes getRetAttributes() const {
234     return getAttributes(0);
235   }
236 
237   /// getFnAttributes - The function attributes are returned.
getFnAttributes()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.
paramHasAttr(unsigned Idx,Attributes Attr)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.
getParamAlignment(unsigned Idx)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.
getRawPointer()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   ///
isEmpty()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 
295 private:
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