source/libs/gmp/gmp-src/mpn/x86/rshift.asm

   1 dnl  x86 mpn_rshift -- mpn right shift.
   2
   3 dnl  Copyright 1992, 1994, 1996, 1999-2002 Free Software Foundation, Inc.
   4
   5 dnl  This file is part of the GNU MP Library.
   6 dnl
   7 dnl  The GNU MP Library is free software; you can redistribute it and/or modify
   8 dnl  it under the terms of either:
   9 dnl
  10 dnl    * the GNU Lesser General Public License as published by the Free
  11 dnl      Software Foundation; either version 3 of the License, or (at your
  12 dnl      option) any later version.
  13 dnl
  14 dnl  or
  15 dnl
  16 dnl    * the GNU General Public License as published by the Free Software
  17 dnl      Foundation; either version 2 of the License, or (at your option) any
  18 dnl      later version.
  19 dnl
  20 dnl  or both in parallel, as here.
  21 dnl
  22 dnl  The GNU MP Library is distributed in the hope that it will be useful, but
  23 dnl  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  24 dnl  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  25 dnl  for more details.
  26 dnl
  27 dnl  You should have received copies of the GNU General Public License and the
  28 dnl  GNU Lesser General Public License along with the GNU MP Library.  If not,
  29 dnl  see https://www.gnu.org/licenses/.
  30
  31 include(`../config.m4')
  32
  33
  34 C     cycles/limb
  35 C P54    7.5
  36 C P55    7.0
  37 C P6     2.5
  38 C K6     4.5
  39 C K7     5.0
  40 C P4    16.5
  41
  42
  43 C mp_limb_t mpn_rshift (mp_ptr dst, mp_srcptr src, mp_size_t size,
  44 C                       unsigned shift);
  45
  46 defframe(PARAM_SHIFT,16)
  47 defframe(PARAM_SIZE, 12)
  48 defframe(PARAM_SRC,  8)
  49 defframe(PARAM_DST,  4)
  50
  51         TEXT
  52         ALIGN(8)
  53 PROLOGUE(mpn_rshift)
  54
  55         pushl   %edi
  56         pushl   %esi
  57         pushl   %ebx
  58 deflit(`FRAME',12)
  59
  60         movl    PARAM_DST,%edi
  61         movl    PARAM_SRC,%esi
  62         movl    PARAM_SIZE,%edx
  63         movl    PARAM_SHIFT,%ecx
  64
  65         leal    -4(%edi,%edx,4),%edi
  66         leal    (%esi,%edx,4),%esi
  67         negl    %edx
  68
  69         movl    (%esi,%edx,4),%ebx      C read least significant limb
  70         xorl    %eax,%eax
  71         shrdl(  %cl, %ebx, %eax)        C compute carry limb
  72         incl    %edx
  73         jz      L(end)
  74         pushl   %eax                    C push carry limb onto stack
  75         testb   $1,%dl
  76         jnz     L(1)                    C enter loop in the middle
  77         movl    %ebx,%eax
  78
  79         ALIGN(8)
  80 L(oop): movl    (%esi,%edx,4),%ebx      C load next higher limb
  81         shrdl(  %cl, %ebx, %eax)        C compute result limb
  82         movl    %eax,(%edi,%edx,4)      C store it
  83         incl    %edx
  84 L(1):   movl    (%esi,%edx,4),%eax
  85         shrdl(  %cl, %eax, %ebx)
  86         movl    %ebx,(%edi,%edx,4)
  87         incl    %edx
  88         jnz     L(oop)
  89
  90         shrl    %cl,%eax                C compute most significant limb
  91         movl    %eax,(%edi)             C store it
  92
  93         popl    %eax                    C pop carry limb
  94
  95         popl    %ebx
  96         popl    %esi
  97         popl    %edi
  98         ret
  99
 100 L(end): shrl    %cl,%ebx                C compute most significant limb
 101         movl    %ebx,(%edi)             C store it
 102
 103         popl    %ebx
 104         popl    %esi
 105         popl    %edi
 106         ret
 107
 108 EPILOGUE()