Class Subroutine

java.lang.Object
EDU.purdue.cs.bloat.cfg.Subroutine
public class Subroutine extends Object
Subroutine represents a subroutine (target of a jsr instruction) in java bytecode. Subroutines are used to implement the finally part of a try-catch-finally block.

Each Subroutine belongs in a control flow graph, has an entry and exit block, and has a local variable that contains its return address. Additionally, it maintains a list of paths from blocks in which the subroutine is called to block that is executed after the subroutine returns.

Note that it is assumed that each subroutine ends with a ret. While this is true for bytecode generated by javac, it is not required.

See Also:

  • Constructor Summary

    Constructors
    Constructor
    Description
    Subroutine(FlowGraph graph)
    Constructor.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    addPath(Block callerBlock, Block returnBlock)
    Adds a path from the block before a Subroutine is called to a block after the subroutine is called.
    Block
    entry()
    Returns the first Block in the subroutine.
    Block
    exit()
    Returns the last Block in the subroutine.
    FlowGraph
    graph()
    Returns the CFG that contains this subroutine.
    int
    numPaths()
    Returns the number of places that this subroutine is called.
    Collection
    paths()
    Returns the paths (a Collection of two-element arrays of Blocks) that represent the Blocks that end in a call to this subroutine and the block that begin with the return address from this subroutine.
    Block
    pathSource(Block block)
    Returns the "caller block" for a given "return block".
    Block
    pathTarget(Block block)
    Returns the "return block" for a given "caller block".
    void
    print(PrintStream out)
    Prints a textual representation of this Subroutine.
    void
    removeAllPaths()
    Removes all caller-return paths.
    void
    removePath(Block callerBlock, Block returnBlock)
    Removes a path between a caller Block and a return Block.
    void
    removePathsContaining(Block block)
    Removes all paths involving block regardless of whether it is a calling (source) block or a returning (target) block.
    LocalVariable
    returnAddress()
    Returns the local variable containing the return address of this subroutine.
    void
    setEntry(Block entry)
    Sets the entry Block for this Subroutine.
    void
    setExit(Block exit)
    Sets the exit Block for this Subroutine.
    void
    setReturnAddress(LocalVariable returnAddress)
    Sets the address (stored in a LocalVariable) to which this subroutine will return once it is finished.
    String
    toString()
     

    Methods inherited from class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

  • Constructor Details

    • Subroutine

      public Subroutine(FlowGraph graph)
      Constructor.
      Parameters:
      graph - The CFG containing the block.

  • Method Details

    • returnAddress

      public LocalVariable returnAddress()
      Returns the local variable containing the return address of this subroutine.

    • setReturnAddress

      public void setReturnAddress(LocalVariable returnAddress)
      Sets the address (stored in a LocalVariable) to which this subroutine will return once it is finished.
      Parameters:
      returnAddress - Local variable that stores the address to which the subroutine returns when it is completed.
      See Also:

    • numPaths

      public int numPaths()
      Returns the number of places that this subroutine is called.

    • paths

      public Collection paths()
      Returns the paths (a Collection of two-element arrays of Blocks) that represent the Blocks that end in a call to this subroutine and the block that begin with the return address from this subroutine.

    • graph

      public FlowGraph graph()
      Returns the CFG that contains this subroutine.

    • removePathsContaining

      public void removePathsContaining(Block block)
      Removes all paths involving block regardless of whether it is a calling (source) block or a returning (target) block.

    • removePath

      public void removePath(Block callerBlock, Block returnBlock)
      Removes a path between a caller Block and a return Block.

    • removeAllPaths

      public void removeAllPaths()
      Removes all caller-return paths.

    • addPath

      public void addPath(Block callerBlock, Block returnBlock)
      Adds a path from the block before a Subroutine is called to a block after the subroutine is called. If the callerBlock is already associated with a returnBlock, the old returnBlock is replaced.
      Parameters:
      callerBlock - The block in which the subroutine is called. This Block ends with a jsr to this subroutine.
      returnBlock - The block to which the subroutine returns. This Block begins at the return address of this subroutine.

    • pathTarget

      public Block pathTarget(Block block)
      Returns the "return block" for a given "caller block".

    • pathSource

      public Block pathSource(Block block)
      Returns the "caller block" for a given "return block".

    • setEntry

      public void setEntry(Block entry)
      Sets the entry Block for this Subroutine.

    • setExit

      public void setExit(Block exit)
      Sets the exit Block for this Subroutine.

    • entry

      public Block entry()
      Returns the first Block in the subroutine.

    • exit

      public Block exit()
      Returns the last Block in the subroutine.

    • print

      public void print(PrintStream out)
      Prints a textual representation of this Subroutine.
      Parameters:
      out - The PrintStream to which to print.

    • toString

      public String toString()
      Overrides:
      toString in class Object