DominatorSystem (Jikes RVM API)

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org.jikesrvm.compilers.opt.controlflow
Class DominatorSystem

java.lang.Object
  org.jikesrvm.compilers.opt.dfsolver.DF_System
      org.jikesrvm.compilers.opt.controlflow.DominatorSystem

class DominatorSystem
extends DF_System
extends DF_System

Implementation of the dataflow equation system to calculate dominators.

Field Summary
`private IR`	`ir` The governing IR.

Fields inherited from class org.jikesrvm.compilers.opt.dfsolver.DF_System
`cells, workList`

Constructor Summary
`DominatorSystem(IR ir)` Default constructor.

Method Summary
`(package private) DF_LatticeCell[]`	`getCellsForPredecessors(BasicBlock bb)` Return a list of lattice cells corresponding to the predecessors of a basic block.
`(package private) Object`	`getKey(BasicBlock bb)` Get the DF_LatticeCell key corresponding to a basic block
`protected void`	`initializeLatticeCells()` Initialize the lattice variables (Dominator sets) for each basic block.
`protected void`	`initializeWorkList()` Initialize the work list for the dataflow equation system.
`protected DF_LatticeCell`	`makeCell(Object key)` Make a new DF_LatticeCell key corresponding to a basic block
`(package private) void`	`setupEquations()` Go through each basic block in the IR, and add equations to the system as required.

Methods inherited from class org.jikesrvm.compilers.opt.dfsolver.DF_System
`addAllEquationsToWorkList, addCellAppearancesToWorkList, addNewEquationsToWorkList, addToWorkList, changedCell, findOrCreateCell, getCell, getEquations, getNumberOfEquations, getSolution, newEquation, newEquation, solve, toString, updateWorkList`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

ir

private final IR ir

The governing IR.

Constructor Detail

DominatorSystem

public DominatorSystem(IR ir)

Default constructor.

Parameters:: ir - the governing IR

Method Detail

setupEquations

void setupEquations()

Go through each basic block in the IR, and add equations to the system as required.

Uses the algorithm contained in Dragon book, pg. 670-1.

     D(n0) := { n0 }
     for n in N - { n0 } do D(n) := N;
     while changes to any D(n) occur do
       for n in N - {n0} do
           D(n) := {n} U (intersect of D(p) over all predecessors p of n)

initializeLatticeCells

protected void initializeLatticeCells()

Initialize the lattice variables (Dominator sets) for each basic block.

Specified by:: initializeLatticeCells in class DF_System

initializeWorkList

protected void initializeWorkList()

Initialize the work list for the dataflow equation system.

The initial work list is every equation containing the start node.

Specified by:: initializeWorkList in class DF_System

getKey

Object getKey(BasicBlock bb)

Get the DF_LatticeCell key corresponding to a basic block

Parameters:: bb - the basic block
Returns:: the key (just the block itself)

makeCell

protected DF_LatticeCell makeCell(Object key)

Make a new DF_LatticeCell key corresponding to a basic block

Specified by:: makeCell in class DF_System

Parameters:: key - the basic block
Returns:: the new cell

getCellsForPredecessors

DF_LatticeCell[] getCellsForPredecessors(BasicBlock bb)

Return a list of lattice cells corresponding to the predecessors of a basic block.

Parameters:: bb - the basic block