source/libs/gmp/gmp-src/mpn/arm64/mod_34lsub1.asm

   1 dnl  ARM64 mpn_mod_34lsub1 -- remainder modulo 2^48-1.
   2
   3 dnl  Copyright 2012-2014 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 C            cycles/limb
  34 C Cortex-A53     ?
  35 C Cortex-A57     ?
  36
  37 define(`ap',    x0)
  38 define(`n',     x1)
  39
  40 changecom(@&*$)
  41
  42 C mp_limb_t mpn_mod_34lsub1 (mp_srcptr up, mp_size_t n)
  43
  44 C TODO
  45 C  * An alternative inner loop which could run at 0.722 c/l:
  46 C       adds    x8, x8, x2
  47 C       adcs    x9, x9, x3
  48 C       ldp     x2, x3, [ap, #-32]
  49 C       adcs    x10, x10, x4
  50 C       adc     x12, x12, xzr
  51 C       adds    x8, x8, x5
  52 C       ldp     x4, x5, [ap, #-16]
  53 C       sub     n, n, #6
  54 C       adcs    x9, x9, x6
  55 C       adcs    x10, x10, x7
  56 C       ldp     x6, x7, [ap], #48
  57 C       adc     x12, x12, xzr
  58 C       tbz     n, #63, L(top)
  59
  60 ASM_START()
  61         TEXT
  62         ALIGN(32)
  63 PROLOGUE(mpn_mod_34lsub1)
  64         subs    n, n, #3
  65         mov     x8, #0
  66         b.lt    L(le2)                  C n <= 2
  67
  68         ldp     x2, x3, [ap, #0]
  69         ldr     x4, [ap, #16]
  70         add     ap, ap, #24
  71         subs    n, n, #3
  72         b.lt    L(sum)                  C n <= 5
  73         cmn     x0, #0                  C clear carry
  74
  75 L(top): ldp     x5, x6, [ap, #0]
  76         ldr     x7, [ap, #16]
  77         add     ap, ap, #24
  78         sub     n, n, #3
  79         adcs    x2, x2, x5
  80         adcs    x3, x3, x6
  81         adcs    x4, x4, x7
  82         tbz     n, #63, L(top)
  83
  84         adc     x8, xzr, xzr            C x8 <= 1
  85
  86 L(sum): cmn     n, #2
  87         mov     x5, #0
  88         b.lo    1f
  89         ldr     x5, [ap], #8
  90 1:      mov     x6, #0
  91         b.ls    1f
  92         ldr     x6, [ap], #8
  93 1:      adds    x2, x2, x5
  94         adcs    x3, x3, x6
  95         adcs    x4, x4, xzr
  96         adc     x8, x8, xzr             C x8 <= 2
  97
  98 L(sum2):
  99         and     x0, x2, #0xffffffffffff
 100         add     x0, x0, x2, lsr #48
 101         add     x0, x0, x8
 102
 103         lsl     x8, x3, #16
 104         and     x1, x8, #0xffffffffffff
 105         add     x0, x0, x1
 106         add     x0, x0, x3, lsr #32
 107
 108         lsl     x8, x4, #32
 109         and     x1, x8, #0xffffffffffff
 110         add     x0, x0, x1
 111         add     x0, x0, x4, lsr #16
 112         ret
 113
 114 L(le2): cmn     n, #1
 115         b.ne    L(1)
 116         ldp     x2, x3, [ap]
 117         mov     x4, #0
 118         b       L(sum2)
 119 L(1):   ldr     x2, [ap]
 120         and     x0, x2, #0xffffffffffff
 121         add     x0, x0, x2, lsr #48
 122         ret
 123 EPILOGUE()