Class SSAPhiInstruction

java.lang.Object

com.ibm.wala.ssa.SSAInstruction

com.ibm.wala.ssa.SSAPhiInstruction

public class SSAPhiInstruction
extends SSAInstruction

A phi instruction in SSA form.

See any modern compiler textbook for the definition of phi and the nature of SSA.

Note: In SSA IRs, these instructions do not appear in the normal instruction array returned by IR.getInstructions(); instead these instructions live in ISSABasicBlock.

getUse(i) corresponds to the value number from the i^th predecessor of the corresponding ISSABasicBlock b in ControlFlowGraph g, where predecessor order is the order of nodes returned by the Iterator g.getPredNodes(b).

Note: if getUse(i) returns AbstractIntStackMachine.TOP (that is, -1), then that use represents an edge in the CFG which is infeasible in verifiable bytecode.

Nested Class Summary

Nested classes/interfaces inherited from class SSAInstruction

SSAInstruction.IVisitor, SSAInstruction.Visitor

Field Summary

Fields inherited from class SSAInstruction

NO_INDEX

Constructor Summary

Constructors

Constructor	Description
SSAPhiInstruction(int iindex, int result, int[] params)

Method Summary

Modifier and Type	Method	Description
SSAInstruction	copyForSSA(SSAInstructionFactory insts, int[] defs, int[] uses)	This method is meant to be used during SSA conversion for an IR that is not in SSA form.
int	getDef()
int	getDef(int i)	Return the ith def
int	getNumberOfDefs()
int	getNumberOfUses()
int	getUse(int j)
protected String	getValueString(SymbolTable symbolTable, int valueNumber)
boolean	hasDef()	Does this instruction define a normal value, as distinct from a set of exceptions possibly thrown by it (e.g.
int	hashCode()
boolean	isFallThrough()
void	setValues(int[] i)	Clients should not call this.
String	toString(SymbolTable symbolTable)
void	visit(SSAInstruction.IVisitor v)	Apply an IVisitor to this instruction.

Methods inherited from class SSAInstruction

equals, getExceptionTypes, iIndex, isPEI, setInstructionIndex, toString

Methods inherited from class Object

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

Constructor Details

SSAPhiInstruction

public SSAPhiInstruction(int iindex,
 int result,
 int[] params)
                  throws IllegalArgumentException

Throws:

IllegalArgumentException

Method Details

copyForSSA

public SSAInstruction copyForSSA(SSAInstructionFactory insts,
 int[] defs,
 int[] uses)
                          throws IllegalArgumentException

Description copied from class: SSAInstruction

This method is meant to be used during SSA conversion for an IR that is not in SSA form. It creates a new SSAInstruction of the same type as the receiver, with a combination of the receiver's uses and defs and those from the method parameters.

In particular, if the 'defs' parameter is null, then the new instruction has the same defs as the receiver. If 'defs' is not null, it must be an array with a size equal to the number of defs that the receiver instruction has. In this case, the new instruction has defs taken from the array. The uses of the new instruction work in the same way with the 'uses' parameter.

Note that this only applies to CAst-based IR translation, since Java bytecode-based IR generation uses a different SSA construction mechanism.

TODO: move this into the SSAInstructionFactory

Specified by:

copyForSSA in class SSAInstruction

Throws:

IllegalArgumentException

toString

public String toString(SymbolTable symbolTable)

Specified by:

toString in class SSAInstruction

visit

public void visit(SSAInstruction.IVisitor v)

Description copied from class: SSAInstruction

Apply an IVisitor to this instruction. We invoke the appropriate IVisitor method according to the type of this instruction.

Specified by:

visit in class SSAInstruction

hasDef

public boolean hasDef()

Description copied from class: SSAInstruction

Does this instruction define a normal value, as distinct from a set of exceptions possibly thrown by it (e.g. for invoke instructions).

Overrides:

hasDef in class SSAInstruction

Returns:

true if the instruction does define a proper value.

See Also:

• SSAInstruction.getDef()

getDef

public int getDef()

Overrides:

getDef in class SSAInstruction

getDef

public int getDef(int i)

Description copied from class: SSAInstruction

Return the ith def

Overrides:

getDef in class SSAInstruction

Parameters:

i - number of the def, starting at 0.

getNumberOfUses

public int getNumberOfUses()

Overrides:

getNumberOfUses in class SSAInstruction

getNumberOfDefs

public int getNumberOfDefs()

Overrides:

getNumberOfDefs in class SSAInstruction

getUse

public int getUse(int j)
           throws IllegalArgumentException

Overrides:

getUse in class SSAInstruction

Returns:

value number representing the jth use in this instruction. -1 means TOP (i.e., the value doesn't matter)

Throws:

IllegalArgumentException

setValues

public void setValues(int[] i)

Clients should not call this. only for SSA builders. I hate this. Nuke it someday.

getValueString

protected String getValueString(SymbolTable symbolTable,
 int valueNumber)

Overrides:

getValueString in class SSAInstruction

hashCode

public int hashCode()

Specified by:

hashCode in class SSAInstruction

isFallThrough

public boolean isFallThrough()

Specified by:

isFallThrough in class SSAInstruction

Returns:

true iff this instruction may fall through to the next