Method: Fisk::CFG.live_variables

Defined in:
lib/fisk/basic_block.rb

.live_variables(blocks) ⇒ Object 



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# File 'lib/fisk/basic_block.rb', line 109

def self.live_variables blocks
  seen = Set.new

  blocks.each do |block|
    used = Set.new
    defd = Set.new

    block.insns.each do |insn|
      if insn.has_temp_registers?
        insn.temp_registers.each do |reg|
          defd << reg unless seen.include?(reg)
          used << reg unless defd.include?(reg)
          seen << reg
        end
      end
    end

    block.use = used.to_a
    block.def = defd.to_a
    block.in  = []
    block.out = []
  end

  worklist = blocks.dup
  while block = worklist.pop
    block.out = block.succ.inject([]) { |out_registers, succ_block|
      out_registers | succ_block.in
    }
    ins = block.in | block.use | (block.out - block.def)

    if ins == block.in
      # Done with this block!
      block.live.each do |live_register|
        live_register.end_point ||= block.end_point

        if live_register.start_point > block.start_point
          live_register.start_point = block.start_point
        end

        if live_register.end_point < block.end_point
          live_register.end_point = block.end_point
        end
      end
    else
      block.in = ins
      worklist.concat(block.pred)
    end
  end

  seen
end