Missing intrinsics for gcc:

see https://gcc.gnu.org/onlinedocs/gccint/Integer-library-routines.html#Integer-library-routines
https://github.com/llvm-mirror/compiler-rt/tree/master/lib/builtins


umodsi3 is for modulo with a constant (in this example, "... % 1000".

        ldu     #1000
        stu     6,s
        stx     ,s
        sty     2,s
        leax    147,s
        jsr     ___umodsi3
        leas    8,s
        ldd     141,s
        aslb
        rola
        tfr     d,x
        ldx     _word,x
        stx     113,s


; no code to implement it yet.
__umodsi3 (a, b)
     unsigned nongcc_SI_type a, b;
{
  perform_umodsi3 (a, b);  // a % b
}


COMPILER_RT_ABI su_int __umodsi3(su_int a, su_int b) {
  return a - __udivsi3(a, b) * b;
}


// This function should not call __divsi3!
COMPILER_RT_ABI su_int __udivsi3(su_int n, su_int d) {
  const unsigned n_uword_bits = sizeof(su_int) * CHAR_BIT;
  su_int q;
  su_int r;
  unsigned sr;
  // special cases
  if (d == 0)
    return 0; // ?!
  if (n == 0)
    return 0;
  sr = __builtin_clz(d) - __builtin_clz(n);
  // 0 <= sr <= n_uword_bits - 1 or sr large
  if (sr > n_uword_bits - 1) // d > r
    return 0;
  if (sr == n_uword_bits - 1) // d == 1
    return n;
  ++sr;
  // 1 <= sr <= n_uword_bits - 1
  // Not a special case
  q = n << (n_uword_bits - sr);
  r = n >> sr;
  su_int carry = 0;
  for (; sr > 0; --sr) {
    // r:q = ((r:q)  << 1) | carry
    r = (r << 1) | (q >> (n_uword_bits - 1));
    q = (q << 1) | carry;
    // carry = 0;
    // if (r.all >= d.all)
    // {
    //      r.all -= d.all;
    //      carry = 1;
    // }
    const si_int s = (si_int)(d - r - 1) >> (n_uword_bits - 1);
    carry = s & 1;
    r -= d & s;
  }
  q = (q << 1) | carry;
  return q;
}





S _divhi3 Ref0000

        ; [468]     cows = score%5; bulls = score/5;
        ldd     #5
        std     ,--s
        leax    ,y
        jsr     _modhi3
        leas    2,s
        stx     2,s
        ldd     #5
        std     ,--s
        leax    ,y
        jsr     _divhi3
        leas    2,s
        leay    ,x

#ifdef L_divhi3
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; ___divhi3 - signed division
;;; Arguments: Dividend in X, divisor on the stack
;;; Returns result in X.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
        .area .text
        .globl _divhi3
_divhi3:
        ldd     2,s
        bne     do_div          ; check dividend
        SIGFPE
do_div:
        pshs    x
        jsr     _seuclid
        puls    x,pc
#endif



S _modhi3 Ref0000

  752                                         ; [486]     cows = your_score%5;
  02B8 CC 00 05            753         ldd     #5
  02BB ED E3               754         std     ,--s
  02BD AE E8 12            755         ldx     18,s
  02C0 BD 00 00            756         jsr     _modhi3
  02C3 32 62               757         leas    2,s
  02C5 AF 6E               758         stx     14,s


#ifdef L_modhi3
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; ___modhi3 - signed modulo
;;; Arguments: Dividend in X, divisor on the stack
;;; Returns result in X.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
        .area .text
        .globl _modhi3
_modhi3:
        ldd     2,s
        bne     do_mod          ; check dividend
        SIGFPE
do_mod:
        pshs    x
        jsr     _seuclid
        leas    2,s
        tfr     d,x
        rts
#endif


Some I/O is predeclared.  Printf sometimes gets converted into putchar or puts if param is
a single character or a string with no % parameters embedded.

S _putchar Ref0000
S _puts Ref0000

S _printf Ref0000

S _getchar Ref0000