Package com.ibm.wala.core.util.ssa

Class SSAValue

java.lang.Object

com.ibm.wala.core.util.ssa.SSAValue

Direct Known Subclasses:

ParameterAccessor.Parameter

public class SSAValue
extends Object

A number representating an SSA-Value and its type.

WALA does not use this on a regular basis but it may come in handy for creating SyntheticMethods.

Use ParameterAccessor to get the parameters of a function as SSAValues.

Since:

2013-10-20

Author:

Tobias Blaschke <code@tobiasblaschke.de>

See Also:

• TypeSafeInstructionFactory
• ParameterAccessor

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	SSAValue.NamedKey	Identify variables by a string and type.
static class	SSAValue.TypeKey	A key that matches variables by their type - does not compare to NamedKey.
static class	SSAValue.UniqueKey	A key that cannot be recreated.
static interface	SSAValue.VariableKey	All variables with the same name in the source code.
static class	SSAValue.WeaklyNamedKey	This NamedKey also equals to TypeKeys.

Field Summary

Fields

Modifier and Type	Field	Description
final SSAValue.VariableKey	key	All variables with the same name in the source code share a key.
protected final MethodReference	mRef	Method the variable is valid in
protected final int	number	The SSA Value itself
protected final TypeReference	type	The type of this variable

Constructor Summary

Constructors

Constructor	Description
SSAValue(int number, SSAValue copyFrom)	Create a new instance of the same type, validity and name.
SSAValue(int number, TypeReference type, MethodReference validIn)	Generates a SSAValue with a UniqueKey.
SSAValue(int number, TypeReference type, MethodReference validIn, SSAValue.VariableKey key)	Makes a SSAValue with number and type valid in the specified Method.
SSAValue(int number, TypeReference type, MethodReference validIn, String variableName)	Generates a SSAValue with a NamedKey (or TypeKey if name==null).

Method Summary

Modifier and Type	Method	Description
boolean	equals(Object o)
int	getNumber()	The SSA-Value to use with SSAInstructions.
TypeReference	getType()	The type this SSA-Value represents.
MethodReference	getValidIn()	Return the MethodReference this Variable was set valid in.
String	getVariableName()	Return the optional variable name.
int	hashCode()
boolean	isAssigned()	If setAssigned() was called on this variable.
void	setAssigned()	Mark this variable as assigned.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Details

number

protected final int number

The SSA Value itself

type

protected final TypeReference type

The type of this variable

key

public final SSAValue.VariableKey key

All variables with the same name in the source code share a key.

mRef

protected final MethodReference mRef

Method the variable is valid in

Constructor Details

SSAValue

public SSAValue(int number,
 TypeReference type,
 MethodReference validIn,
 SSAValue.VariableKey key)

Makes a SSAValue with number and type valid in the specified Method.

The number is the one to use with SSAInstructions.

The MethodReference (validIn) is an optional value. However the TypeSafeInstructionFactory relies on it to verify its ReturnInstruction so setting it does not hurt.

The variableName is optional and not really used yet. It might be handy for debugging.

Parameters:

number - access the value using this number

validIn - optionally assign this value to a method

Throws:

IllegalArgumentException - on negative parameter number

SSAValue

public SSAValue(int number,
 TypeReference type,
 MethodReference validIn,
 String variableName)

Generates a SSAValue with a NamedKey (or TypeKey if name==null).

SSAValue

public SSAValue(int number,
 TypeReference type,
 MethodReference validIn)

Generates a SSAValue with a UniqueKey.

SSAValue

public SSAValue(int number,
 SSAValue copyFrom)

Create a new instance of the same type, validity and name.

Of course you still have to assign something to this value.

Parameters:

number - the new number to use

copyFrom - where to get the rest of the attributes

Method Details

getNumber

public int getNumber()

The SSA-Value to use with SSAInstructions.

As an alternative one can generate Instructions using the TypeSafeInstructionFactory which takes SSAValues as parameters.

getType

public TypeReference getType()

The type this SSA-Value represents.

isAssigned

public boolean isAssigned()

If setAssigned() was called on this variable.

setAssigned

public void setAssigned()

Mark this variable as assigned.

Sets the value returned by isAssigned() to true. As a safety measure one can only call this method once on a SSAValue, the second time raises an exception.

The TypeSafeInstructionFactory calls this method when writing to an SSAValue. It does however not check the setting when reading from an SSAValue.

This does obviously not prevent from generating a new SSAValue with the same number and double-assign anyhow.

Throws:

IllegalStateException - if the variable was already assigned to

getValidIn

public MethodReference getValidIn()

Return the MethodReference this Variable was set valid in.

The value returned by this method is the one set in the constructor. As this parameter is optional to it this function may return null if it was not set.

Returns:

the argument validIn to the constructor

getVariableName

public String getVariableName()

Return the optional variable name.

Returns:

the argument variableName to the constructor

toString

public String toString()

Overrides:

toString in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object