source/libs/gmp/gmp-src/mpn/powerpc32/750/rshift.asm

   1 dnl  PowerPC 750 mpn_rshift -- mpn right shift.
   2
   3 dnl  Copyright 2002, 2003 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 750:     3.0
  36 C 7400:    3.0
  37
  38
  39 C mp_limb_t mpn_rshift (mp_ptr dst, mp_srcptr src, mp_size_t size,
  40 C                       unsigned shift);
  41 C
  42 C This code is the same per-limb speed as mpn/powerpc32/rshift.asm, but
  43 C smaller and saving about 30 or so cycles of overhead.
  44
  45 ASM_START()
  46 PROLOGUE(mpn_rshift)
  47
  48         C r3    dst
  49         C r4    src
  50         C r5    size
  51         C r6    shift
  52
  53         mtctr   r5              C size
  54         lwz     r8, 0(r4)       C src[0]
  55
  56         subfic  r7, r6, 32      C 32-shift
  57         addi    r5, r3, -4      C dst-4
  58
  59         slw     r3, r8, r7      C return value
  60         bdz     L(one)
  61
  62         lwzu    r9, 4(r4)       C src[1]
  63         srw     r8, r8, r6      C src[0] >> shift
  64         bdz     L(two)
  65
  66
  67 L(top):
  68         C r3    return value
  69         C r4    src, incrementing
  70         C r5    dst, incrementing
  71         C r6    shift
  72         C r7    32-shift
  73         C r8    src[i-1] >> shift
  74         C r9    src[i]
  75         C r10
  76
  77         lwzu    r10, 4(r4)
  78         slw     r11, r9, r7
  79
  80         or      r8, r8, r11
  81         stwu    r8, 4(r5)
  82
  83         srw     r8, r9, r6
  84         bdz     L(odd)
  85
  86         C r8    src[i-1] >> shift
  87         C r9
  88         C r10   src[i]
  89
  90         lwzu    r9, 4(r4)
  91         slw     r11, r10, r7
  92
  93         or      r8, r8, r11
  94         stwu    r8, 4(r5)
  95
  96         srw     r8, r10, r6
  97         bdnz    L(top)
  98
  99
 100 L(two):
 101         C r3    return value
 102         C r4
 103         C r5    &dst[size-2]
 104         C r6    shift
 105         C r7    32-shift
 106         C r8    src[size-2] >> shift
 107         C r9    src[size-1]
 108         C r10
 109
 110         slw     r11, r9, r7
 111         srw     r12, r9, r6     C src[size-1] >> shift
 112
 113         or      r8, r8, r11
 114         stw     r12, 8(r5)      C dst[size-1]
 115
 116         stw     r8, 4(r5)       C dst[size-2]
 117         blr
 118
 119
 120 L(odd):
 121         C r3    return value
 122         C r4
 123         C r5    &dst[size-2]
 124         C r6    shift
 125         C r7    32-shift
 126         C r8    src[size-2] >> shift
 127         C r9
 128         C r10   src[size-1]
 129
 130         slw     r11, r10, r7
 131         srw     r12, r10, r6
 132
 133         or      r8, r8, r11
 134         stw     r12, 8(r5)      C dst[size-1]
 135
 136         stw     r8, 4(r5)       C dst[size-2]
 137         blr
 138
 139
 140 L(one):
 141         C r3    return value
 142         C r4
 143         C r5    dst-4
 144         C r6    shift
 145         C r7
 146         C r8    src[0]
 147
 148         srw     r8, r8, r6
 149
 150         stw     r8, 4(r5)       C dst[0]
 151         blr
 152
 153 EPILOGUE(mpn_rshift)