ReachableAnalysis

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ic.dfa
Class ReachableAnalysis

java.lang.Object
  ic.dfa.DataFlowAnalysis<Boolean>
      ic.dfa.ReachableAnalysis

public class ReachableAnalysis
extends DataFlowAnalysis<Boolean>
extends DataFlowAnalysis<Boolean>

A simple analysis to determine whether there are unreachable statements in a program. That is it, determines whether there is a path from the entry to each program point. For example:

 void main(string[] a) {
   boolean b;
   int y,z;
   if (b) {
      return;
      z = z + 1;  // NOT REACHABLE
   } 
   y = y + 1;
 }

In this code, the assignment following the return is not reachable. The analysis is defined as follows:

   D  : forward
   V  : { true, false }  where true < false.  
   Top: false.
   /\ : boolean ||
   f  : f_I(s) = s for all instructions I
   boundary:  OUT[in] = true

After dataflow analysis, unreachable blocks will have IN[b] == false.

Field Summary

Fields inherited from class ic.dfa.DataFlowAnalysis
`cfg, in, out`

Constructor Summary
`ReachableAnalysis(ControlFlowGraph cfg)`

Method Summary
`Boolean`	`boundary()` Initial value for out[enter] or in[exit], depending on direction.
`boolean`	`equals(Boolean t1, Boolean t2)` Return true if t1 and t2 are equivalent.
`boolean`	`isForward()` Return true iff the analysis is a forward analysis.
`Boolean`	`meet(Boolean t1, Boolean t2)` Return the meet of t1 and t2 in the lattice.
`Boolean`	`top()` Top value in the lattice of T elements.
`Boolean`	`transfer(ic.tac.TInstr instr, Boolean t)` Return the result of applying the transfer function for instr to t.

Methods inherited from class ic.dfa.DataFlowAnalysis
`in, out, solve, solveBackward, solveForward, toString`

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

Constructor Detail

ReachableAnalysis

public ReachableAnalysis(ControlFlowGraph cfg)

Method Detail