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dnl ARM v6t2 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')
C cycles/bit (approx)
C StrongARM -
C XScale -
C Cortex-A5 10.1
C Cortex-A7 9.1
C Cortex-A8 6.3
C Cortex-A9 ?
C Cortex-A12 7.7
C Cortex-A15 5.7
C Cortex-A17 ?
C Cortex-A53 7.0
define(`gp', `r0')
define(`u1', `r1')
define(`u0', `r2')
define(`v1', `r3')
define(`v0', `r4')
define(`t0', `r5')
define(`t1', `r6')
define(`cnt', `r7')
ASM_START()
PROLOGUE(mpn_gcd_22)
push { r4-r7 }
ldr v0, [sp,#16] C
L(top): subs t0, u0, v0 C 0 7
beq L(lowz)
sbcs t1, u1, v1 C 1 8
rbit cnt, t0 C 1
negcc t0, t0
mvncc t1, t1
L(bck): movcc v0, u0
movcc v1, u1
clz cnt, cnt C 2
rsb r12, cnt, #32 C 3
lsr u0, t0, cnt C 3
lsl r12, t1, r12 C 4
lsr u1, t1, cnt C 3
orr u0, u0, r12 C 5
orrs r12, u1, v1
bne L(top)
str r12, [gp,#4] C high result limb <= 0
mov r6, gp
mov r0, u0 C pass 1st argument
mov r1, v0 C pass 2nd argument
mov r7, r14 C preserve link register
bl mpn_gcd_11
str r0, [r6,#0]
mov r14, r7
pop { r4-r7 }
bx r14
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
beq L(end)
mov t1, #0
rbit cnt, t0 C 1
negcc t0, t0
b L(bck)
L(end): str v0, [gp,#0]
str v1, [gp,#4]
pop { r4-r7 }
bx r14
EPILOGUE()
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