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dnl ARM64 mpn_rshift.
dnl Copyright 2013, 2014, 2017 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 assumed optimal c/l
C Cortex-A53 3.5-4.0 3.25
C Cortex-A57 2.0 2.0
C X-Gene 2.67 2.5
C TODO
C * The feed-in code used 1 ldr for odd sized and 2 ldr for even sizes. These
C numbers should be 1 and 0, respectively. The str in wind-down should also
C go.
C * Using extr and with 63 separate loops we might reach 1.25 c/l on A57.
C * A53's speed depends on alignment, but not as simply as for lshift/lshiftc.
changecom(blah)
define(`rp_arg', `x0')
define(`up', `x1')
define(`n', `x2')
define(`cnt', `x3')
define(`rp', `x16')
define(`tnc',`x8')
define(`PSHIFT', lsr)
define(`NSHIFT', lsl)
ASM_START()
PROLOGUE(mpn_rshift)
mov rp, rp_arg
sub tnc, xzr, cnt
lsr x17, n, #2
tbz n, #0, L(bx0)
L(bx1): ldr x5, [up]
tbnz n, #1, L(b11)
L(b01): NSHIFT x0, x5, tnc
PSHIFT x2, x5, cnt
cbnz x17, L(gt1)
str x2, [rp]
ret
L(gt1): ldp x4, x5, [up,#8]
sub up, up, #8
sub rp, rp, #32
b L(lo2)
L(b11): NSHIFT x0, x5, tnc
PSHIFT x2, x5, cnt
ldp x6, x7, [up,#8]!
sub rp, rp, #16
b L(lo3)
L(bx0): ldp x4, x5, [up]
tbz n, #1, L(b00)
L(b10): NSHIFT x0, x4, tnc
PSHIFT x13, x4, cnt
NSHIFT x10, x5, tnc
PSHIFT x2, x5, cnt
cbnz x17, L(gt2)
orr x10, x10, x13
stp x10, x2, [rp]
ret
L(gt2): ldp x4, x5, [up,#16]
orr x10, x10, x13
str x10, [rp],#-24
b L(lo2)
L(b00): NSHIFT x0, x4, tnc
PSHIFT x13, x4, cnt
NSHIFT x10, x5, tnc
PSHIFT x2, x5, cnt
ldp x6, x7, [up,#16]!
orr x10, x10, x13
str x10, [rp],#-8
b L(lo0)
ALIGN(16)
L(top): ldp x4, x5, [up,#16]
orr x10, x10, x13
orr x11, x12, x2
stp x11, x10, [rp,#16]
PSHIFT x2, x7, cnt
L(lo2): NSHIFT x10, x5, tnc
NSHIFT x12, x4, tnc
PSHIFT x13, x4, cnt
ldp x6, x7, [up,#32]!
orr x10, x10, x13
orr x11, x12, x2
stp x11, x10, [rp,#32]!
PSHIFT x2, x5, cnt
L(lo0): sub x17, x17, #1
L(lo3): NSHIFT x10, x7, tnc
NSHIFT x12, x6, tnc
PSHIFT x13, x6, cnt
cbnz x17, L(top)
L(end): orr x10, x10, x13
orr x11, x12, x2
PSHIFT x2, x7, cnt
stp x11, x10, [rp,#16]
str x2, [rp,#32]
ret
EPILOGUE()
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