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dnl ARM mpn_mod_34lsub1 -- remainder modulo 2^24-1.
dnl Copyright 2012, 2013 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
C StrongARM ?
C XScale ?
C Cortex-A5 2.67
C Cortex-A7 2.35
C Cortex-A8 2.0
C Cortex-A9 1.33
C Cortex-A15 1.33
C Cortex-A17 3.34
C Cortex-A53 2.0
define(`ap', r0)
define(`n', r1)
C mp_limb_t mpn_mod_34lsub1 (mp_srcptr up, mp_size_t n)
C TODO
C * Write cleverer summation code.
C * Consider loading 6 64-bit aligned registers at a time, to approach 1 c/l.
ASM_START()
TEXT
ALIGN(32)
PROLOGUE(mpn_mod_34lsub1)
push { r4, r5, r6, r7 }
subs n, n, #3
mov r7, #0
blt L(le2) C n <= 2
ldmia ap!, { r2, r3, r12 }
subs n, n, #3
blt L(sum) C n <= 5
cmn r0, #0 C clear carry
sub n, n, #3
b L(mid)
L(top): adcs r2, r2, r4
adcs r3, r3, r5
adcs r12, r12, r6
L(mid): ldmia ap!, { r4, r5, r6 }
tst n, n
sub n, n, #3
bpl L(top)
add n, n, #3
adcs r2, r2, r4
adcs r3, r3, r5
adcs r12, r12, r6
movcs r7, #1 C r7 <= 1
L(sum): cmn n, #2
movlo r4, #0
ldrhs r4, [ap], #4
movls r5, #0
ldrhi r5, [ap], #4
adds r2, r2, r4
adcs r3, r3, r5
adcs r12, r12, #0
adc r7, r7, #0 C r7 <= 2
L(sum2):
bic r0, r2, #0xff000000
add r0, r0, r2, lsr #24
add r0, r0, r7
mov r7, r3, lsl #8
bic r1, r7, #0xff000000
add r0, r0, r1
add r0, r0, r3, lsr #16
mov r7, r12, lsl #16
bic r1, r7, #0xff000000
add r0, r0, r1
add r0, r0, r12, lsr #8
pop { r4, r5, r6, r7 }
return lr
L(le2): cmn n, #1
bne L(1)
ldmia ap!, { r2, r3 }
mov r12, #0
b L(sum2)
L(1): ldr r2, [ap]
bic r0, r2, #0xff000000
add r0, r0, r2, lsr #24
pop { r4, r5, r6, r7 }
return lr
EPILOGUE()
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