Steps

• Construct the EXPOSED and PRESERVED sets for each basic block

• Then for each basic block

  • Compute definitions that reach that block by taking the union of the outgoing sets of all blocks from which control can directly arrive at the top of the block
  • Update the outgoing definition set by computing the set intersecting the union set with that basic block’s PRESERVED set
  • Then union in the EXPOSED set for the block

• Continue processing the basic blocks for the subprogram in this manner until no further changes occur

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