2.11BSD#431 - /usr/src/lib/libc/pdp/crt/almul.s

   1: /*
   2:  * Copyright (c) 1987 Regents of the University of California.
   3:  * All rights reserved.  The Berkeley software License Agreement
   4:  * specifies the terms and conditions for redistribution.
   5:  */
   6: 
   7: #ifdef LIBC_SCCS
   8:         <@(#)almul.s	2.3 (Berkeley) 1/28/87\0>
   9:         .even
  10: #endif LIBC_SCCS
  11: 
  12: /*
  13:  * almul(lhs, rhs)
  14:  *	long	*lhs, rhs;
  15:  *
  16:  * 32-bit "*=" routine for fixed point hardware.  Also recommended for floating
  17:  * hardware, for compatility & speed.  Credit to an unknown author who slipped
  18:  * it under the door.  Calls to aldiv are generated automatically by the C
  19:  * compiler.
  20:  */
  21: #include "DEFS.h"
  22: 
  23: ASENTRY(almul)
  24:         mov     r2,-(sp)        / save r2-4
  25:         mov     r3,-(sp)
  26:         mov     r4,-(sp)
  27:         mov     8.(sp),r4       / r4 = lhs
  28:         mov     2(r4),r2        / r2 = loint(*lhs)
  29:         sxt     r1              / r1 = sxt(loint(*lhs)) - hiint(*lhs)
  30:         sub     (r4),r1
  31:         mov     12.(sp),r0      / r0 = loint(rhs)
  32:         sxt     r3              / r3 = sxt(loint(rhs)) - hiint(rhs)
  33:         sub     10.(sp),r3
  34:         mul     r0,r1           / MAGIC = loint(rhs) * hiint(*lhs)'
  35:         mul     r2,r3           /       + loint(*lhs) * hiint(rhs)'
  36:         add     r1,r3
  37:         mul     r2,r0           / prod (r0:r1) = loint(lhs)*loint(rhs)
  38:         sub     r3,r0           / hiint(prod) -= MAGIC
  39:         mov     r0,(r4)+        / *lhs = prod
  40:         mov     r1,(r4)
  41:         mov     (sp)+,r4        / restore regsisters
  42:         mov     (sp)+,r3        /   and return
  43:         mov     (sp)+,r2
  44:         rts     pc

Defined functions