#include "llvm/ADT/FoldingSet.h"
namespace llvm {
-
-/// Function parameters can have attributes to indicate how they should be
-/// treated by optimizations and code generation. This enumeration lists the
-/// attributes that can be associated with parameters or function results.
-/// @brief Function parameter attributes.
namespace ParamAttr {
+/// Function parameters and results can have attributes to indicate how they
+/// should be treated by optimizations and code generation. This enumeration
+/// lists the attributes that can be associated with parameters or function
+/// results.
+/// @brief Function parameter attributes.
enum Attributes {
None = 0, ///< No attributes have been set
ZExt = 1 << 0, ///< zero extended before/after call
}
/// This is just a pair of values to associate a set of parameter attributes
-/// with a parameter index.
+/// with a parameter index.
/// @brief ParameterAttributes with a parameter index.
struct ParamAttrsWithIndex {
uint16_t attrs; ///< The attributes that are set, |'d together
/// @brief A vector of attribute/index pairs.
typedef SmallVector<ParamAttrsWithIndex,4> ParamAttrsVector;
+/// @brief A more friendly way to reference the attributes.
typedef ParamAttr::Attributes ParameterAttributes;
-/// This class is used by Function and CallInst to represent the set of
-/// parameter attributes used. It represents a list of pairs of uint16_t, one
-/// for the parameter index, and one a set of ParameterAttributes bits.
-/// Parameters that have no attributes are not present in the list. The list
-/// may also be empty, but this doesn't occur in practice. The list constructs
-/// as empty and is filled by the insert method. The list can be turned into
-/// a string of mnemonics suitable for LLVM Assembly output. Various accessors
-/// are provided to obtain information about the attributes.
+/// This class represents a list of attribute/index pairs for parameter
+/// attributes. Each entry in the list contains the index of a function
+/// parameter and the associated ParameterAttributes. If a parameter's index is
+/// not present in the list, then no attributes are set for that parameter. The
+/// list may also be empty, but this does not occur in practice. An item in
+/// the list with an index of 0 refers to the function as a whole or its result.
+/// To construct a ParamAttrsList, you must first fill a ParamAttrsVector with
+/// the attribute/index pairs you wish to set. The list of attributes can be
+/// turned into a string of mnemonics suitable for LLVM Assembly output.
+/// Various accessors are provided to obtain information about the attributes.
+/// Note that objects of this class are "uniqued". The \p get method can return
+/// the pointer of an existing and identical instance. Consequently, reference
+/// counting is necessary in order to determine when the last reference to a
+/// ParamAttrsList of a given shape is dropped. Users of this class should use
+/// the addRef and dropRef methods to add/drop references. When the reference
+/// count goes to zero, the ParamAttrsList object is deleted.
+/// This class is used by Function, CallInst and InvokeInst to represent their
+/// sets of parameter attributes.
/// @brief A List of ParameterAttributes.
class ParamAttrsList : public FoldingSetNode {
/// @name Construction
/// @{
private:
- // ParamAttrsList is uniqued, thes should not be publicly available
+ // ParamAttrsList is uniqued, these should not be publicly available
void operator=(const ParamAttrsList &); // Do not implement
ParamAttrsList(const ParamAttrsList &); // Do not implement
ParamAttrsList(); // Do not implement
- ~ParamAttrsList() {} // Not public!
+ ~ParamAttrsList(); // Private implementation
+ /// Only the \p get method can invoke this when it wants to create a
+ /// new instance.
/// @brief Construct an ParamAttrsList from a ParamAttrsVector
- explicit ParamAttrsList(const ParamAttrsVector &attrVec) : attrs(attrVec) {}
+ explicit ParamAttrsList(const ParamAttrsVector &attrVec)
+ : attrs(attrVec), refCount(0) {}
public:
/// This method ensures the uniqueness of ParamAttrsList instances. The
/// @brief Return the number of parameter attributes this type has.
unsigned size() const { return attrs.size(); }
+ /// Classes retaining references to ParamAttrsList objects should call this
+ /// method to increment the reference count. This ensures that the
+ /// ParamAttrsList object will not disappear until the class drops it.
+ /// @brief Add a reference to this instance.
+ void addRef() const { refCount++; }
+
+ /// Classes retaining references to ParamAttrsList objects should call this
+ /// method to decrement the reference count and possibly delete the
+ /// ParamAttrsList object. This ensures that ParamAttrsList objects are
+ /// cleaned up only when the last reference to them is dropped.
+ /// @brief Drop a reference to this instance.
+ void dropRef() const {
+ assert(refCount != 0 && "dropRef without addRef");
+ if (--refCount == 0)
+ delete this;
+ }
+
/// @}
/// @name Implementation Details
/// @{
/// @name Data
/// @{
private:
- ParamAttrsVector attrs; ///< The list of attributes
+ ParamAttrsVector attrs; ///< The list of attributes
+ mutable unsigned refCount; ///< The number of references to this object
/// @}
};
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