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
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; }
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Nested Class Summary
Nested classes/interfaces inherited from class com.ibm.wala.ssa.SSAInstruction
SSAInstruction.IVisitor, SSAInstruction.Visitor
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Field Summary
Fields inherited from class com.ibm.wala.ssa.SSAAbstractUnaryInstruction
result, val
Fields inherited from class com.ibm.wala.ssa.SSAInstruction
NO_INDEX
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Constructor Summary
ConstructorDescriptionSSAPiInstruction
(int iindex, int result, int val, int piBlock, int successorBlock, SSAInstruction cause) -
Method Summary
Modifier and TypeMethodDescriptioncopyForSSA
(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.getCause()
int
int
int
getVal()
toString
(SymbolTable symbolTable) void
Apply an IVisitor to this instruction.Methods inherited from class com.ibm.wala.ssa.SSAUnaryOpInstruction
getOpcode
Methods inherited from class com.ibm.wala.ssa.SSAAbstractUnaryInstruction
getDef, getDef, getNumberOfDefs, getNumberOfUses, getUse, hasDef, hashCode, isFallThrough
Methods inherited from class com.ibm.wala.ssa.SSAInstruction
equals, getExceptionTypes, getValueString, iIndex, isPEI, setInstructionIndex, toString
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Constructor Details
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SSAPiInstruction
public SSAPiInstruction(int iindex, 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.
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Method Details
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copyForSSA
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 classSSAUnaryOpInstruction
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toString
- Overrides:
toString
in classSSAUnaryOpInstruction
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visit
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 classSSAUnaryOpInstruction
- See Also:
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getSuccessor
public int getSuccessor() -
getPiBlock
public int getPiBlock() -
getCause
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getVal
public int getVal()
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