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dnl ARM v8a mpn_gcd_22.
dnl Copyright 2019 Free Software Foundation, Inc.
dnl This file is part of the GNU MP Library.
dnl
dnl The GNU MP Library is free software; you can redistribute it and/or modify
dnl it under the terms of either:
dnl
dnl * the GNU Lesser General Public License as published by the Free
dnl Software Foundation; either version 3 of the License, or (at your
dnl option) any later version.
dnl
dnl or
dnl
dnl * the GNU General Public License as published by the Free Software
dnl Foundation; either version 2 of the License, or (at your option) any
dnl later version.
dnl
dnl or both in parallel, as here.
dnl
dnl The GNU MP Library is distributed in the hope that it will be useful, but
dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
dnl for more details.
dnl
dnl You should have received copies of the GNU General Public License and the
dnl GNU Lesser General Public License along with the GNU MP Library. If not,
dnl see https://www.gnu.org/licenses/.
include(`../config.m4')
changecom(blah)
C cycles/bit (approx)
C Cortex-A35 ?
C Cortex-A53 7.26
C Cortex-A55 ?
C Cortex-A57 ?
C Cortex-A72 5.72
C Cortex-A73 6.43
C Cortex-A75 ?
C Cortex-A76 ?
C Cortex-A77 ?
define(`u1', `x0')
define(`u0', `x1')
define(`v1', `x2')
define(`v0', `x3')
define(`t0', `x5')
define(`t1', `x6')
define(`cnt', `x7')
define(`tnc', `x8')
ASM_START()
PROLOGUE(mpn_gcd_22)
ALIGN(16)
L(top): subs t0, u0, v0 C 0 6
cbz t0, L(lowz)
sbcs t1, u1, v1 C 1 7
rbit cnt, t0 C 1
cneg t0, t0, cc C 2
cinv t1, t1, cc C 2 u = |u - v|
L(bck): csel v0, v0, u0, cs C 2
csel v1, v1, u1, cs C 2 v = min(u,v)
clz cnt, cnt C 2
sub tnc, xzr, cnt C 3
lsr u0, t0, cnt C 3
lsl x14, t1, tnc C 4
lsr u1, t1, cnt C 3
orr u0, u0, x14 C 5
orr x11, u1, v1
cbnz x11, L(top)
subs x4, u0, v0 C 0
b.eq L(end1) C
ALIGN(16)
L(top1):rbit x12, x4 C 1,5
clz x12, x12 C 2
csneg x4, x4, x4, cs C v = abs(u-v), even 1
csel u0, v0, u0, cs C u = min(u,v) 1
lsr v0, x4, x12 C 3
subs x4, u0, v0 C 4
b.ne L(top1) C
L(end1):mov x0, u0
mov x1, #0
ret
L(lowz):C We come here when v0 - u0 = 0
C 1. If v1 - u1 = 0, then gcd is u = v.
C 2. Else compute gcd_21({v1,v0}, |u1-v1|)
subs t0, u1, v1
b.eq L(end)
mov t1, #0
rbit cnt, t0 C 1
cneg t0, t0, cc C 2
b L(bck) C FIXME: make conditional
L(end): mov x0, v0
mov x1, v1
ret
EPILOGUE()
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