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 ith 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.

  • Constructor Details

  • 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:
    • 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