[snipe.git] / optimize / labelcoalescing.sml

structure LabelCoalescing :> OPTIMIZATION =
struct
  structure X = x86
  
  structure LabelMap = SplayMapFn(struct
                                    type ord_key = Label.label
                                    val compare = Label.compare
                                  end)
  
  fun coalesce insns =
    let
      fun lmap (SOME(a)) ((X.LABEL l)::is) = let val (m, il) = lmap (SOME(a)) is in (LabelMap.insert(m, l, a), il) end
        | lmap (NONE) ((X.LABEL l)::is) = let val (m, il) = lmap (SOME(l)) is in  (LabelMap.insert(m, l, l), (X.LABEL l)::il) end
        | lmap _ (i::is) = let val (m, il) = lmap NONE is in (m, i::il) end
        | lmap _ nil = (LabelMap.empty, nil)

      val (labelmap, insns') = lmap NONE insns

      fun convert ((X.Jcc(c,l))::is) = (X.Jcc(c, valOf(LabelMap.find(labelmap,l))))::(convert is)
        | convert ((X.JMP(l))::is) = (X.JMP(valOf(LabelMap.find(labelmap,l))))::(convert is)
        | convert (i::is) = i::(convert is)
        | convert nil = nil
    in
      convert insns'
    end  
  
  val optimizer = { shortname = "labelcoalescing", description = "Coalesces adjacent labels", func = Optimizer.PRELIVENESS coalesce }
end