com.ibm.wala.ssa
Class SSAPiInstruction
java.lang.Object
com.ibm.wala.ssa.SSAInstruction
com.ibm.wala.ssa.SSAAbstractUnaryInstruction
com.ibm.wala.ssa.SSAUnaryOpInstruction
com.ibm.wala.ssa.SSAPiInstruction
public class SSAPiInstruction
- extends SSAUnaryOpInstruction
A Pi instruction is a dummy assignment inserted at the tail of a basic block, in order
to get a new variable name to associate with some flow-insensitive dataflow fact.
You can build an IR with or without Pi instructions, depending on SSAOptions selected.
A Pi instruction is linked to its "cause" instruction, which is usually a conditional
branch.
for example, the following pseudo-code
boolean condition = (x instanceof Integer);
if (condition) {
S1;
else {
S2;
}
could be translated roughly as follows:
boolean condition = (x instanceof Integer);
LABEL1: if (condition) {
x_1 = pi(x, LABEL1);
S1;
else {
x_2 = pi(x, LABEL2);
S2;
}
| Methods inherited from class java.lang.Object |
clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
SSAPiInstruction
public SSAPiInstruction(int result,
int val,
int piBlock,
int successorBlock,
SSAInstruction cause)
- Parameters:
successorBlock - the successor block; this PI assignment happens on the transition between this basic block and
the successor block.
copyForSSA
public SSAInstruction copyForSSA(SSAInstructionFactory insts,
int[] defs,
int[] uses)
- 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
- Overrides:
copyForSSA in class SSAUnaryOpInstruction
toString
public java.lang.String toString(SymbolTable symbolTable)
- Overrides:
toString in class SSAUnaryOpInstruction
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.
- Overrides:
visit in class SSAUnaryOpInstruction
- See Also:
SSAInstruction.visit(IVisitor)
getSuccessor
public int getSuccessor()
getPiBlock
public int getPiBlock()
getCause
public SSAInstruction getCause()
getVal
public int getVal()