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dnl ARM v4 mpn_divexact_1.
dnl Contributed to the GNU project by Torbjorn Granlund.
dnl Copyright 2012 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/limb cycles/limb
C norm unorm modexact_1c_odd
C StrongARM ?
C XScale ?
C Cortex-A7 ?
C Cortex-A8 ?
C Cortex-A9 10 12
C Cortex-A15 9 9
C Architecture requirements:
C v5 -
C v5t -
C v5te -
C v6 -
C v6t2 -
C v7a -
define(`rp', `r0')
define(`up', `r1')
define(`n', `r2')
define(`d', `r3')
define(`cy', `r7')
define(`cnt', `r6')
define(`tnc', `r8')
ASM_START()
PROLOGUE(mpn_divexact_1)
tst d, #1
push {r4-r9}
mov cnt, #0
bne L(inv)
C count trailing zeros
movs r4, d, lsl #16
moveq d, d, lsr #16
moveq cnt, #16
tst d, #0xff
moveq d, d, lsr #8
addeq cnt, cnt, #8
LEA( r4, ctz_tab)
and r5, d, #0xff
ldrb r4, [r4, r5]
mov d, d, lsr r4
add cnt, cnt, r4
C binvert limb
L(inv): LEA( r4, binvert_limb_table)
and r12, d, #254
ldrb r4, [r4, r12, lsr #1]
mul r12, r4, r4
mul r12, d, r12
rsb r12, r12, r4, lsl #1
mul r4, r12, r12
mul r4, d, r4
rsb r4, r4, r12, lsl #1 C r4 = inverse
tst cnt, cnt
ldr r5, [up], #4 C up[0]
mov cy, #0
bne L(unnorm)
L(norm):
subs n, n, #1 C set carry as side-effect
beq L(edn)
ALIGN(16)
L(tpn): sbcs cy, r5, cy
ldr r5, [up], #4
sub n, n, #1
mul r9, r4, cy
tst n, n
umull r12, cy, d, r9
str r9, [rp], #4
bne L(tpn)
L(edn): sbc cy, r5, cy
mul r9, r4, cy
str r9, [rp]
pop {r4-r9}
return r14
L(unnorm):
rsb tnc, cnt, #32
mov r5, r5, lsr cnt
subs n, n, #1 C set carry as side-effect
beq L(edu)
ALIGN(16)
L(tpu): ldr r12, [up], #4
orr r9, r5, r12, lsl tnc
mov r5, r12, lsr cnt
sbcs cy, r9, cy C critical path ->cy->cy->
sub n, n, #1
mul r9, r4, cy C critical path ->cy->r9->
tst n, n
umull r12, cy, d, r9 C critical path ->r9->cy->
str r9, [rp], #4
bne L(tpu)
L(edu): sbc cy, r5, cy
mul r9, r4, cy
str r9, [rp]
pop {r4-r9}
return r14
EPILOGUE()
RODATA
ctz_tab:
.byte 8,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0
.byte 5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0
.byte 6,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0
.byte 5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0
.byte 7,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0
.byte 5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0
.byte 6,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0
.byte 5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0
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