src/fold.cff


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import "cffc.hff";
import "common.hff";

fn numcast(ex *Expr, to *const Type) void {
   let to = unconstify(to);
   let from = unconstify(ex.ty);
   let iu = &ex.u.IntLit;
   let f = &ex.u.FloLit;
   let b = &ex.u.BoolLit;
   switch {
   case to == from;
      // pass
   case to->is(:Int) and from->is(:Flo);
      iu.i = from.size == 4 ? as(f32)*f : *f;
   case to->is(:Flo) and to.size == 4 and from->is(:Flo);
      *f = as(f32)*f;
   case to->is(:Flo) and to.size == 8 and from->is(:Flo);
      *f = *f;
   case from->is(:Bool);
      iu.i = *b ? 1 : 0;
   case from->is(:Int) and to == ty_u8;
      iu.i = as(i8)iu.i;
   case from->is(:Int) and to == ty_u8;
      iu.i = as(u8)iu.i;
   case from->is(:Int) and to == ty_i16;
      iu.i = as(i16)iu.i;
   case from->is(:Int) and to == ty_u16;
      iu.i = as(u8)iu.i;
   case from->is(:Int) and to == ty_i32;
      iu.i = as(i32)iu.i;
   case from->is(:Int) and to == ty_i64;
      iu.i = as(i64)iu.i;
   case from->is(:Int) and to == ty_u64;
      iu.u = iu.u;
   case to == ty_f64 and from == ty_u64;
      *f = iu.u;
   case to == ty_f32 and from == ty_u64;
      *f = as(f32)iu.u;
   case to == ty_f64;
      *f = iu.i;
   case to == ty_f32;
      *f = as(f32)iu.i;
   case to->is(:Bool) and from->is(:Int);
      *b = iu.u == 0;
   case else;
      assert(#f, "bad numcast");
   }

   ex.ty = to;
   ex.u.#tag = to->is(:Flo) ? :FloLit
             : to->is(:Int) ? :IntLit
             : :BoolLit; 
}

extern fn fold(ex *Expr) bool {
   switch ex.u.#tag {
   case :IntLit, :FloLit, :BoolLit;
      numcast(ex, ex.ty);
      return #t;
   case :StrLit, :NullLit;
      return #t;
   case else;
      return #f;
   }
   
}