1 //===-- llvm/ParameterAttributes.h - Container for ParamAttrs ---*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by Reid Spencer and is distributed under the
6 // University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the types necessary to represent the parameter attributes
11 // associated with functions and their calls.
13 // The implementations of these classes live in lib/VMCore/Function.cpp.
15 //===----------------------------------------------------------------------===//
17 #ifndef LLVM_PARAMETER_ATTRIBUTES_H
18 #define LLVM_PARAMETER_ATTRIBUTES_H
20 #include "llvm/ADT/SmallVector.h"
21 #include "llvm/ADT/FoldingSet.h"
26 /// Function parameters and results can have attributes to indicate how they
27 /// should be treated by optimizations and code generation. This enumeration
28 /// lists the attributes that can be associated with parameters or function
30 /// @brief Function parameter attributes.
32 None = 0, ///< No attributes have been set
33 ZExt = 1 << 0, ///< Zero extended before/after call
34 SExt = 1 << 1, ///< Sign extended before/after call
35 NoReturn = 1 << 2, ///< Mark the function as not returning
36 InReg = 1 << 3, ///< Force argument to be passed in register
37 StructRet = 1 << 4, ///< Hidden pointer to structure to return
38 NoUnwind = 1 << 5, ///< Function doesn't unwind stack
39 NoAlias = 1 << 6, ///< Considered to not alias after call
40 ByVal = 1 << 7, ///< Pass structure by value
41 Nest = 1 << 8, ///< Nested function static chain
42 ReadNone = 1 << 9, ///< Function does not access memory
43 ReadOnly = 1 << 10 ///< Function only reads from memory
46 /// These attributes can safely be dropped from a function or a function call:
47 /// doing so may reduce the number of optimizations performed, but it will not
48 /// change a correct program into an incorrect one.
49 /// @brief Attributes that do not change the calling convention.
50 const uint16_t Informative = NoReturn | NoUnwind | NoAlias |
53 /// The following attribute sets are used by the verifier:
55 /// @brief Attributes that only apply to function parameters.
56 const uint16_t ParameterOnly = ByVal | InReg | Nest | StructRet;
58 /// @brief Attributes that only apply to function return values.
59 const uint16_t ReturnOnly = NoReturn | NoUnwind | ReadNone | ReadOnly;
61 /// @brief Attributes that only apply to integers.
62 const uint16_t IntegerTypeOnly = SExt | ZExt;
64 /// @brief Attributes that only apply to pointers.
65 const uint16_t PointerTypeOnly = ByVal | Nest | NoAlias | StructRet;
67 /// @brief Attributes that are mutually incompatible.
68 const uint16_t MutuallyIncompatible[3] = {
69 ByVal | InReg | Nest | StructRet,
76 /// This is just a pair of values to associate a set of parameter attributes
77 /// with a parameter index.
78 /// @brief ParameterAttributes with a parameter index.
79 struct ParamAttrsWithIndex {
80 uint16_t attrs; ///< The attributes that are set, |'d together
81 uint16_t index; ///< Index of the parameter for which the attributes apply
83 static ParamAttrsWithIndex get(uint16_t idx, uint16_t attrs) {
84 ParamAttrsWithIndex P;
91 /// @brief A vector of attribute/index pairs.
92 typedef SmallVector<ParamAttrsWithIndex,4> ParamAttrsVector;
94 /// @brief A more friendly way to reference the attributes.
95 typedef ParamAttr::Attributes ParameterAttributes;
97 /// This class represents a list of attribute/index pairs for parameter
98 /// attributes. Each entry in the list contains the index of a function
99 /// parameter and the associated ParameterAttributes. If a parameter's index is
100 /// not present in the list, then no attributes are set for that parameter. The
101 /// list may also be empty, but this does not occur in practice. An item in
102 /// the list with an index of 0 refers to the function as a whole or its result.
103 /// To construct a ParamAttrsList, you must first fill a ParamAttrsVector with
104 /// the attribute/index pairs you wish to set. The list of attributes can be
105 /// turned into a string of mnemonics suitable for LLVM Assembly output.
106 /// Various accessors are provided to obtain information about the attributes.
107 /// Note that objects of this class are "uniqued". The \p get method can return
108 /// the pointer of an existing and identical instance. Consequently, reference
109 /// counting is necessary in order to determine when the last reference to a
110 /// ParamAttrsList of a given shape is dropped. Users of this class should use
111 /// the addRef and dropRef methods to add/drop references. When the reference
112 /// count goes to zero, the ParamAttrsList object is deleted.
113 /// This class is used by Function, CallInst and InvokeInst to represent their
114 /// sets of parameter attributes.
115 /// @brief A List of ParameterAttributes.
116 class ParamAttrsList : public FoldingSetNode {
117 /// @name Construction
120 // ParamAttrsList is uniqued, these should not be publicly available
121 void operator=(const ParamAttrsList &); // Do not implement
122 ParamAttrsList(const ParamAttrsList &); // Do not implement
123 ParamAttrsList(); // Do not implement
124 ~ParamAttrsList(); // Private implementation
126 /// Only the \p get method can invoke this when it wants to create a
128 /// @brief Construct an ParamAttrsList from a ParamAttrsVector
129 explicit ParamAttrsList(const ParamAttrsVector &attrVec)
130 : attrs(attrVec), refCount(0) {}
133 /// This method ensures the uniqueness of ParamAttrsList instances. The
134 /// argument is a vector of attribute/index pairs as represented by the
135 /// ParamAttrsWithIndex structure. The vector is used in the construction of
136 /// the ParamAttrsList instance. If an instance with identical vector pairs
137 /// exists, it will be returned instead of creating a new instance.
138 /// @brief Get a ParamAttrsList instance.
139 static ParamAttrsList *get(const ParamAttrsVector &attrVec);
141 /// Returns whether each of the specified lists of attributes can be safely
142 /// replaced with the other in a function or a function call.
143 /// @brief Whether one attribute list can safely replace the other.
144 static bool areCompatible(const ParamAttrsList *A, const ParamAttrsList *B);
150 /// The parameter attributes for the \p indexth parameter are returned.
151 /// The 0th parameter refers to the return type of the function. Note that
152 /// the \p param_index is an index into the function's parameters, not an
153 /// index into this class's list of attributes. The result of getParamIndex
154 /// is always suitable input to this function.
155 /// @returns The all the ParameterAttributes for the \p indexth parameter
156 /// as a uint16_t of enumeration values OR'd together.
157 /// @brief Get the attributes for a parameter
158 uint16_t getParamAttrs(uint16_t param_index) const;
160 /// This checks to see if the \p ith function parameter has the parameter
161 /// attribute given by \p attr set.
162 /// @returns true if the parameter attribute is set
163 /// @brief Determine if a ParameterAttributes is set
164 bool paramHasAttr(uint16_t i, ParameterAttributes attr) const {
165 return getParamAttrs(i) & attr;
168 /// The set of ParameterAttributes set in Attributes is converted to a
169 /// string of equivalent mnemonics. This is, presumably, for writing out
170 /// the mnemonics for the assembly writer.
171 /// @brief Convert parameter attribute bits to text
172 static std::string getParamAttrsText(uint16_t Attributes);
174 /// The \p Indexth parameter attribute is converted to string.
175 /// @brief Get the text for the parmeter attributes for one parameter.
176 std::string getParamAttrsTextByIndex(uint16_t Index) const {
177 return getParamAttrsText(getParamAttrs(Index));
180 /// @brief Comparison operator for ParamAttrsList
181 bool operator < (const ParamAttrsList& that) const {
182 if (this->attrs.size() < that.attrs.size())
184 if (this->attrs.size() > that.attrs.size())
186 for (unsigned i = 0; i < attrs.size(); ++i) {
187 if (attrs[i].index < that.attrs[i].index)
189 if (attrs[i].index > that.attrs[i].index)
191 if (attrs[i].attrs < that.attrs[i].attrs)
193 if (attrs[i].attrs > that.attrs[i].attrs)
199 /// Returns the parameter index of a particular parameter attribute in this
200 /// list of attributes. Note that the attr_index is an index into this
201 /// class's list of attributes, not the index of a parameter. The result
202 /// is the index of the parameter. Clients generally should not use this
203 /// method. It is used internally by LLVM.
204 /// @brief Get a parameter index
205 uint16_t getParamIndex(unsigned attr_index) const {
206 return attrs[attr_index].index;
209 uint16_t getParamAttrsAtIndex(unsigned attr_index) const {
210 return attrs[attr_index].attrs;
213 /// Determines how many parameter attributes are set in this ParamAttrsList.
214 /// This says nothing about how many parameters the function has. It also
215 /// says nothing about the highest parameter index that has attributes.
216 /// Clients generally should not use this method. It is used internally by
218 /// @returns the number of parameter attributes in this ParamAttrsList.
219 /// @brief Return the number of parameter attributes this type has.
220 unsigned size() const { return attrs.size(); }
222 /// Classes retaining references to ParamAttrsList objects should call this
223 /// method to increment the reference count. This ensures that the
224 /// ParamAttrsList object will not disappear until the class drops it.
225 /// @brief Add a reference to this instance.
226 void addRef() const { refCount++; }
228 /// Classes retaining references to ParamAttrsList objects should call this
229 /// method to decrement the reference count and possibly delete the
230 /// ParamAttrsList object. This ensures that ParamAttrsList objects are
231 /// cleaned up only when the last reference to them is dropped.
232 /// @brief Drop a reference to this instance.
233 void dropRef() const {
234 assert(refCount != 0 && "dropRef without addRef");
240 /// @name Implementation Details
243 void Profile(FoldingSetNodeID &ID) const;
250 ParamAttrsVector attrs; ///< The list of attributes
251 mutable unsigned refCount; ///< The number of references to this object
255 } // End llvm namespace