arch/powerpc/lib/_lshrdi3.S

   1 /*
   2  * This code was copied from arch/powerpc/kernel/misc_32.S in the Linux
   3  * kernel sources (commit 85e2efbb1db9a18d218006706d6e4fbeb0216213, also
   4  * known as 2.6.38-rc5).  The source file copyrights are as follows:
   5  *
   6  * (C) Copyright 1995-1996 Gary Thomas (gdt@linuxppc.org)
   7  *
   8  * Largely rewritten by Cort Dougan (cort@cs.nmt.edu)
   9  * and Paul Mackerras.
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License as
  13  * published by the Free Software Foundation; either version 2 of
  14  * the License, or (at your option) any later version.
  15  */
  16
  17 #include <ppc_asm.tmpl>
  18 #include <ppc_defs.h>
  19 #include <config.h>
  20
  21 /*
  22  * Extended precision shifts.
  23  *
  24  * Updated to be valid for shift counts from 0 to 63 inclusive.
  25  * -- Gabriel
  26  *
  27  * R3/R4 has 64 bit value
  28  * R5    has shift count
  29  * result in R3/R4
  30  *
  31  *  ashrdi3: arithmetic right shift (sign propagation)
  32  *  lshrdi3: logical right shift
  33  *  ashldi3: left shift
  34  */
  35         .globl __lshrdi3
  36 __lshrdi3:
  37         subfic  r6,r5,32
  38         srw     r4,r4,r5        # LSW = count > 31 ? 0 : LSW >> count
  39         addi    r7,r5,32        # could be xori, or addi with -32
  40         slw     r6,r3,r6        # t1 = count > 31 ? 0 : MSW << (32-count)
  41         srw     r7,r3,r7        # t2 = count < 32 ? 0 : MSW >> (count-32)
  42         or      r4,r4,r6        # LSW |= t1
  43         srw     r3,r3,r5        # MSW = MSW >> count
  44         or      r4,r4,r7        # LSW |= t2
  45         blr