local

   include "sparcInstr.sml"

in

functor SparcPeephole(SparcInstr : SPARCINSTR) : PEEPHOLE =
struct
   structure I = SparcInstr
   structure C = I.C

   (* IMPORTANT: instructions are now given in forward order *)
   fun peephole instrs =
   let fun isZero(I.LAB le)  = I.LabelExp.valueOf le = 0
         | isZero(I.REG r)   = C.registerNum r = 0
         | isZero(I.IMMED i) = i = 0
         | isZero _ = false

       fun removable(I.ARITH{a=(I.ADD | I.SUB), r, i, d}) =
             C.sameColor(r,d) andalso isZero i
         | removable(I.ANNOTATION{i,a}) = removable i
         | removable _ = false

       fun loop(current, instrs) = 
           case current of
             [] => instrs
           | i::rest where removable i => loop(rest, instrs)
           | i::rest => loop(rest, i::instrs)
   in  loop(instrs, [])
   end
end 

end