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C arm/ecc-secp521r1-modp.asm
ifelse(`
Copyright (C) 2013 Niels Möller
This file is part of GNU Nettle.
GNU Nettle is free software: you can redistribute it and/or
modify it under the terms of either:
* the GNU Lesser General Public License as published by the Free
Software Foundation; either version 3 of the License, or (at your
option) any later version.
or
* the GNU General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your
option) any later version.
or both in parallel, as here.
GNU Nettle is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received copies of the GNU General Public License and
the GNU Lesser General Public License along with this program. If
not, see http://www.gnu.org/licenses/.
')
.file "ecc-secp521r1-modp.asm"
.arm
define(`HP', `r0')
define(`RP', `r1')
define(`XP', `r2')
define(`T0', `r3')
define(`T1', `r4')
define(`T2', `r5')
define(`F0', `r6')
define(`F1', `r7')
define(`F2', `r8')
define(`F3', `r10')
define(`H', `r12')
define(`N', `lr')
C ecc_secp521r1_modp (const struct ecc_modulo *m, mp_limb_t *rp)
.text
.Lc511:
.int 511
.align 2
PROLOGUE(_nettle_ecc_secp521r1_modp)
push {r4,r5,r6,r7,r8,r10,lr}
C Use that B^17 = 2^23 (mod p)
ldr F3, [XP, #+68] C 17
add HP, XP, #72 C 18
ldr T0, [XP] C 0
adds T0, T0, F3, lsl #23
str T0, [XP], #+4
mov N, #5
C 5 iterations, reading limbs 18-20, 21-23, 24-26, 27-29, 30-32
C and adding to limbs 1-3, 4-6, 7-9, 19-12, 13-15
.Loop:
ldm XP, {T0,T1,T2} C 1+3*k -- 3+3*k
lsr F0, F3, #9
ldm HP!, {F1,F2,F3} C 18+3*k -- 20+3*k
orr F0, F0, F1, lsl #23
lsr F1, F1, #9
orr F1, F1, F2, lsl #23
lsr F2, F2, #9
orr F2, F2, F3, lsl #23
adcs T0, T0, F0
adcs T1, T1, F1
adcs T2, T2, F2
sub N, N, #1
stm XP!,{T0,T1,T2}
teq N, #0
bne .Loop
ldr F0, [XP], #-64 C 16
ldr F1, [HP] C 33
ldr T0, .Lc511
C Handling of high limbs
C F0 = rp[16] + carry in + F3 >> 9
adcs F0, F0, F3, lsr #9
C Copy low 9 bits to H, then shift right including carry
and H, F0, T0
mov F0, F0, rrx
lsr F0, F0, #8
C Add in F1 = rp[33], with weight 2^1056 = 2^14
adds F0, F0, F1, lsl #14
lsr F1, F1, #18
adc F1, F1, #0
ldm XP!, {T0, T1} C 0-1
adds T0, T0, F0
adcs T1, T1, F1
stm RP!, {T0, T1}
ldm XP!, {T0,T1,T2,F0,F1,F2,F3} C 2-8
adcs T0, T0, #0
adcs T1, T1, #0
adcs T2, T2, #0
adcs F0, F0, #0
adcs F1, F1, #0
adcs F2, F2, #0
adcs F3, F3, #0
stm RP!, {T0,T1,T2,F0,F1,F2,F3} C 2-8
ldm XP, {T0,T1,T2,F0,F1,F2,F3} C 9-15
adcs T0, T0, #0
adcs T1, T1, #0
adcs T2, T2, #0
adcs F0, F0, #0
adcs F1, F1, #0
adcs F2, F2, #0
adcs F3, F3, #0
adcs H, H, #0
stm RP, {T0,T1,T2,F0,F1,F2,F3,H} C 9-16
pop {r4,r5,r6,r7,r8,r10,pc}
EPILOGUE(_nettle_ecc_secp521r1_modp)
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