Attributes

 

Attributes provide a means of annotating instructions and basic blocks with arbitrary information. Attributes attached to an object are structured into a list. An attribute has three properties:

• a value, which is an opaque string of bytes;
• a size, which is an integer representing the length of value in bytes,
• a type, which is an integer representing the nature of the information stored in the value field; for system-defined attributes, type is a negative number.

Predefined Attributes

There are five predefined attribute types. The user can define additional types; user-defined types must correspond to strictly positive type codes.

NO_ATT

is the attribute type returned by the SALTO attribute manipulation calls on failure;

UNPARSE_ATT

modifies the behavior of produceCode() methods of classes INST and BB; if this attribute is present, the text produced by the unparser will be the value of the attribute, and not the external representation of actual basic block or instruction.

CYCLE_ATT

is used by schedule management functions INST::setCycle(), and INST::getCycle() and BB::orderAccordingToCycles() when setting scheduling information of instructions in a basic block and reordering the instructions of a basic block according to their cycle numbers.

COMMENT_ATT

allows to attach comments to a basic block or an instruction. When unparsing an instruction, an end-of-line comment is added. When unparsing a basic block, a number of line comments sufficient to represent the value of the attribute is placed immediately before the first instruction of the basic block.

EXTENDED_BB_ATT,

if attached to a basic block, indicates that this block contains multiple branch instructions and/or backward jumps to the beginning of the block, but still has a single entry point (the first instruction of the block).

INST_IL_ID_ATT

allows to attach to an instruction its ID number in an external tool attached to SALTO.

Attribute Management

SaltoAttribute::SaltoAttribute(int t, void *pt, int size)

default constructor;
builds an attribute of type t, containing the data of size size pointed to by pt;

int SaltoAttribute::getAttributeType(void)

returns the type of the attribute;

void SaltoAttribute::setAttributeType(int t)

sets the type of the attribute;

void *SaltoAttribute::getAttributeData(void)

returns a pointer to the data field of the attribute;

void SaltoAttribute::setAttributeData(void *d)

sets the data pointer of the attribute to d;

int SaltoAttribute::getAttributeSize()

returns the size of the data field of the attribute;

void SaltoAttribute::setAttributeSize(int s)

sets the size of the data field of the attribute to s;

int SaltoAttribute::getTypeNode()

returns the type of the object to which the attribute is attached; possible return values are CFGNODE, BBNODE and INSTNODE.

void *SaltoAttribute::getPtToSalto()

returns a pointer to the SALTO object to which the attribute is attached; this pointer must be re-cast according to the type of the attribute.

void SaltoAttribute::setPtToSalto(void *sa)

sets the pointer to the SALTO object to which the attribute is attached;

void SaltoAttribute::resetPtToSalto()

sets the pointer to SALTO object to NULL.

void SaltoAttribute::setPtToSalto(BB &st)

sets the pointer to SALTO object to the address of basic block &st;

void SaltoAttribute::setPtToSalto(INST &st)

sets the pointer to SALTO object to the address of instruction &st;

void SaltoAttribute::getCFG(void)

returns the pointer to the CFG attribute is attached to; returns NULL if the attribute is attached to a SALTO object of another type.

BB *SaltoAttribute::getBB(void)

returns the pointer to the basic block the attribute is attached to; returns NULL if the attribute is attached to a SALTO object of another type.

INST *SaltoAttribute::getINST(void)

returns the pointer to the instruction the attribute is attached to; returns NULL if the attribute is attached to a SALTO object of another type.

SaltoAttribute *copy(void)

copy an attribute; the data field is not copied.

Attribute Usage

 

The following are methods for attribute manipulation, available on objects of classes CFG, BB, and INST.

N.B: since these methods are applicable to objects of several classes, no class prefix is given in the prototypes listed.

int numberOfAttributes(void)

returns the number of attributes currently attached to the object;

int numberOfAttributes(int type)

returns the number of attributes of type type already attached to the object;

SaltoAttribute *getAttribute(int pos)

returns the pos-th attribute of the current object;

SaltoAttribute *getAttribute(int pos, int type)

returns the pos-th attribute of type
type attached to the current object;

void setAttribute(int pos, SaltoAttribute *att)

sets the pos-th attribute of the current object to att; prints an error message and returns without side effects if no such attribute exists;

void setAttribute(int pos, int type, SaltoAttribute *att)

sets the pos-th attribute of type type attached to the object to att; prints an error message and returns without side effects if no such attribute exists;

int attributeType(int pos)

returns the type of the pos-th attribute attached to the object; returns NO_ATT if no such attribute exists;

void *attributeValue(int pos)

returns the pointer to the value of pos-th attribute of the object; returns NULL if no such attribute exists;

void *attributeValue(int pos, int type)

returns the value of the pos-th attribute of type type attached to the object; returns NULL if no such attribute exists;

void addAttribute(int type, void *a, int size)

adds an attribute of type type and
size size, and containing the data pointed to by a, at end of attribute list of the current object; no copy of data is made;

void addAttribute(int type)

adds an attribute of type type and containing no data;

void addAttribute(void *a, int size)

adds a type-less attribute of size size containing the data pointed to by a, at end of attribute list of the current object; no copy of data is made;

void addAttribute(Attribute *att)

adds a complete attribute pointed to by att at the end of the attribute list of the object;

void *deleteAttribute(uint pos)

removes the pos-th attribute of the object.