;; -*- Mode: Lisp; -*-

(in-package :b32-asm)        

(tagbody
   (defmacro jc (addr)
     `(progn
        (jnc (+ @ 2))
        (jmp ,addr)))
   (defmacro jz (addr)
     `(progn
        (jnz (+ @ 2))
        (jmp ,addr)))
   (defmacro call (addr)
     `(progn
        (lod '(jmp (+ @ 2)))
        (jmp ,addr)))
   (defmacro halt ()
     '(jmp @))
   (defmacro stoi (addr)
     ;; A <- [[addr]]
     `(progn
        (sto aux)
        (lod ,addr)
        (ior '(sto 0))
        (sto (+ @ 2))
        (lod aux)
        (sto 0)))
   (defmacro lodi (addr)
     ;; [[addr]] <- A
     `(progn
        (lod ,addr)
        (ior '(lod 0))
        (sto (+ @ 1))
        (lod 0)))

   (defconstant +tty+ #xF00000)

   (:bss)
 aux (ds 1)

   ;;
   ;; div --- unsigned integer divison
   ;;

   (:bss)
 div.x  (dw 0)                          ;dividend
 div.y  (dw 0)                          ;divisor
 div.q  (dw 0)                          ;quotient
 div.m  (dw 0)                          ;"mask"
 div.tmp (dw 0)                         ;temporary

   (:text)
   (jmp start)
  
   (:text)
 div
   (sto div.ret)
   (lod '0) (sto div.q)
   (lod '1) (sto div.m)                 ;m = 1
 div.L1
   ;; while x <= 2y, shift both y and m left
   ;; and 2y still fits
   (lod div.y)
   (and '#x80000000)
   (jnz div.L2)
   (lod div.y)
   (add div.y)
   (sto div.tmp)
   (lod div.x)
   (sub div.tmp)
   (jc div.L2)                          ;does not fit
   (lod div.tmp)
   (sto div.y)                                ;y = y + y
   (lod div.m) (add div.m) (sto div.m)        ;m = m + k
   (jmp div.L1)
 div.L2
   (lod div.x)
   (sub div.y)
   (jc div.L3)
   (sto div.x)
   (lod div.q) (add div.m) (sto div.q)
 div.L3
   (lod div.m) (asr) (and '#x7FFFFFFF)
   (jz div.done)
   (sto div.m)
   (lod div.y) (asr) (and '#x7FFFFFFF) (sto div.y)
   (jmp div.L2)
 div.done
   (lod div.q)
 div.ret
   (jmp @)

   ;;
   ;; pru -- Print unsigned number in PRU.N in base PRU.BASE
   ;;
   (:bss)
 pru.n           (dw 0)                 ;number to print
 pru.base        (dw 10)                ;print base
 pru.buf         (ds 32)                ;output buffer
 pru.ptr         (ds 1)
   (:text)
 pru
   (sto pru.done)
   (lod 'pru.buf)
   (sto pru.ptr)

 pru.L1
   ;; n = n / base, div.x = n % base
   (lod pru.n)
   (sto div.x)
   (lod pru.base)
   (sto div.y)
   (call div)
   (sto pru.n)
   ;; put remainder (= digit to print) into buffer
   (lod div.x)
   (stoi pru.ptr)
   ;; until n=0, continue
   (lod pru.n)
   (jz  pru.L2)
   ;; ptr++
   (lod pru.ptr) (add '1) (sto pru.ptr)
   (jmp pru.L1)                         ;loop
 pru.L2
   ;; Output buffer in reverse
   (lodi pru.ptr)                       ;A = *ptr
   (sub '10)
   (jc  pru.L4)                         ;<= 10
   (add '(- #\A #\0 10))                ;correct for printing A..Z
 pru.L4
   (add '(+ 10 #\0))            ;correct for ASCII and prior (SUB '10)
   (sto +tty+)
   (lod pru.ptr) (sub '1) (sto pru.ptr) ;ptr++
   ;; check for end
   (sub '(- pru.buf 1))
   (jnz pru.L2)                         ;loop
 pru.done
   (jmp 0)

   ;;
   ;; pri -- print signed number in pri.n in base pru.base
   ;;

   (:bss)
   (defconstant pri.n pru.n)            ;shared
   (:text)
 pri
   (sto pru.done)                       ;setup for tail call
   ;; check for negative numbers
   (lod pri.n)
   (and '#x80000000)
   (jz  (+ pru 1))                      ;positive, tail call
   ;; print sign
   (lod '#\-)
   (sto +tty+)
   ;; negate
   (lod '0)
   (sub pri.n)
   (sto pru.n)
   (jmp (+ pru 1))                      ;tail call

   ;;
   ;; prs -- print zero terminated string pointed to by prs.s
   ;;
   (:bss)
 prs.s   (dw 0)
   (:text)
 prs
   (sto prs.done)
 prs.L1
   (lodi prs.s)
   (jz  prs.done)
   (sto +tty+)
   (lod prs.s) (add '1) (sto prs.s)
   (jmp prs.L1)
 prs.done
   (jmp 0)

   )

#+NIL
(tagbody
   ;;
   ;; hello -- base 36 demo
   ;;
   (:text)
 hello
   (sto hello.done)
          
   (lod '36) (sto pru.base)
          
   (lod '29234652) (sto pru.n) (call pru)
   (lod '#\space) (sto +tty+)
   (lod '22342248) (sto pru.n) (call pru)
   (lod '#\space) (sto +tty+)
   (lod '13801) (sto pru.n) (call pru)
   (lod '#\space) (sto +tty+)
   (lod '1004137) (sto pru.n) (call pru)
   (lod '573386) (sto pru.n) (call pru)
 hello.done
   (jmp 0))