source/libs/gmp/gmp-src/mpn/x86_64/div_qr_2n_pi1.asm

   1 dnl  x86-64 mpn_div_qr_2n_pi1
   2 dnl  -- Divide an mpn number by a normalized 2-limb number,
   3 dnl     using a single-limb inverse.
   4
   5 dnl  Copyright 2007, 2008, 2010-2012 Free Software Foundation, Inc.
   6
   7 dnl  This file is part of the GNU MP Library.
   8 dnl
   9 dnl  The GNU MP Library is free software; you can redistribute it and/or modify
  10 dnl  it under the terms of either:
  11 dnl
  12 dnl    * the GNU Lesser General Public License as published by the Free
  13 dnl      Software Foundation; either version 3 of the License, or (at your
  14 dnl      option) any later version.
  15 dnl
  16 dnl  or
  17 dnl
  18 dnl    * the GNU General Public License as published by the Free Software
  19 dnl      Foundation; either version 2 of the License, or (at your option) any
  20 dnl      later version.
  21 dnl
  22 dnl  or both in parallel, as here.
  23 dnl
  24 dnl  The GNU MP Library is distributed in the hope that it will be useful, but
  25 dnl  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  26 dnl  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  27 dnl  for more details.
  28 dnl
  29 dnl  You should have received copies of the GNU General Public License and the
  30 dnl  GNU Lesser General Public License along with the GNU MP Library.  If not,
  31 dnl  see https://www.gnu.org/licenses/.
  32
  33 include(`../config.m4')
  34
  35
  36 C               c/l
  37 C INPUT PARAMETERS
  38 define(`qp',            `%rdi')
  39 define(`rp',            `%rsi')
  40 define(`up_param',      `%rdx')
  41 define(`un',            `%rcx')
  42 define(`d1',            `%r8')
  43 define(`d0',            `%r9')
  44 define(`di_param',      `8(%rsp)')
  45
  46 define(`di',            `%r10')
  47 define(`up',            `%r11')
  48 define(`u2',            `%rbx')
  49 define(`u1',            `%r12')
  50 define(`t1',            `%r13')
  51 define(`t0',            `%r14')
  52 define(`md1',           `%r15')
  53
  54 C TODO
  55 C * Store qh in the same stack slot as di_param, instead of pushing
  56 C   it. (we could put it in register %rbp, but then we would need to
  57 C   save and restore that instead, which doesn't seem like a win).
  58
  59 ABI_SUPPORT(DOS64)
  60 ABI_SUPPORT(STD64)
  61
  62 ASM_START()
  63         TEXT
  64         ALIGN(16)
  65 PROLOGUE(mpn_div_qr_2n_pi1)
  66         FUNC_ENTRY(4)
  67 IFDOS(` mov     56(%rsp), %r8   ')
  68 IFDOS(` mov     64(%rsp), %r9   ')
  69 IFDOS(`define(`di_param', `72(%rsp)')')
  70         mov     di_param, di
  71         mov     up_param, up
  72         push    %r15
  73         push    %r14
  74         push    %r13
  75         push    %r12
  76         push    %rbx
  77
  78         mov     -16(up, un, 8), u1
  79         mov     -8(up, un, 8), u2
  80
  81         mov     u1, t0
  82         mov     u2, t1
  83         sub     d0, t0
  84         sbb     d1, t1
  85         cmovnc  t0, u1
  86         cmovnc  t1, u2
  87         C push qh which is !carry
  88         sbb     %rax, %rax
  89         inc     %rax
  90         push    %rax
  91         lea     -2(un), un
  92         mov     d1, md1
  93         neg     md1
  94
  95         jmp     L(next)
  96
  97         ALIGN(16)
  98 L(loop):
  99         C udiv_qr_3by2 (q,u2,u1,u2,u1,n0, d1,d0,di)
 100         C Based on the optimized divrem_2.asm code.
 101
 102         mov     di, %rax
 103         mul     u2
 104         mov     u1, t0
 105         add     %rax, t0        C q0 in t0
 106         adc     u2, %rdx
 107         mov     %rdx, t1        C q in t1
 108         imul    md1, %rdx
 109         mov     d0, %rax
 110         lea     (%rdx, u1), u2
 111         mul     t1
 112         mov     (up, un, 8), u1
 113         sub     d0, u1
 114         sbb     d1, u2
 115         sub     %rax, u1
 116         sbb     %rdx, u2
 117         xor     R32(%rax), R32(%rax)
 118         xor     R32(%rdx), R32(%rdx)
 119         cmp     t0, u2
 120         cmovnc  d0, %rax
 121         cmovnc  d1, %rdx
 122         adc     $0, t1
 123         nop
 124         add     %rax, u1
 125         adc     %rdx, u2
 126         cmp     d1, u2
 127         jae     L(fix)
 128 L(bck):
 129         mov     t1, (qp, un, 8)
 130 L(next):
 131         sub     $1, un
 132         jnc     L(loop)
 133 L(end):
 134         mov     u2, 8(rp)
 135         mov     u1, (rp)
 136
 137         C qh on stack
 138         pop     %rax
 139
 140         pop     %rbx
 141         pop     %r12
 142         pop     %r13
 143         pop     %r14
 144         pop     %r15
 145         FUNC_EXIT()
 146         ret
 147
 148 L(fix): C Unlikely update. u2 >= d1
 149         seta    %dl
 150         cmp     d0, u1
 151         setae   %al
 152         orb     %dl, %al                C "orb" form to placate Sun tools
 153         je      L(bck)
 154         inc     t1
 155         sub     d0, u1
 156         sbb     d1, u2
 157         jmp     L(bck)
 158 EPILOGUE()