2.11BSD#431 - /usr/src/lib/libc/pdp/crt/lmul.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:         <@(#)lmul.s	2.3 (Berkeley) 1/28/87\0>
   9:         .even
  10: #endif LIBC_SCCS
  11: 
  12: /*
  13:  * lmul(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(lmul)
  24:         mov     r2,-(sp)        / faster than csv and just 1 more word
  25:         mov     r3,-(sp)
  26:         mov     8.(sp),r2       / r2 = loint(lhs)
  27:         sxt     r1              / r1 = sxt(loint(lhs)) - hiint(lhs)
  28:         sub     6(sp),r1
  29:         mov     12.(sp),r0      / r0 = loint(rhs)
  30:         sxt     r3              / r3 = sxt(loint(rhs)) - hiint(rhs)
  31:         sub     10.(sp),r3
  32:         mul     r0,r1           / MAGIC = loint(rhs) * hiint(lhs)'
  33:         mul     r2,r3           /       + loint(lhs) * hiint(rhs)'
  34:         add     r1,r3
  35:         mul     r2,r0           / prod (r0:r1) = loint(lhs)*loint(rhs)
  36:         sub     r3,r0           / hiint(prod) -= MAGIC
  37:         mov     (sp)+,r3
  38:         mov     (sp)+,r2
  39:         rts     pc

Defined functions