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dnl Alpha ev67 mpn_hamdist -- mpn hamming distance.
dnl Copyright 2003, 2005 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 ev67: 2.5 cycles/limb
C unsigned long mpn_hamdist (mp_srcptr xp, mp_srcptr yp, mp_size_t size);
C
C The hope was for 2.0 c/l here, but that isn't achieved. We're limited by
C renaming register shortage. Since we need 5 instructions per limb, further
C unrolling could approach 1.5 c/l.
C
C The main loop processes two limbs from each operand on each iteration. An
C odd size is handled by processing xp[0]^yp[0] at the start. If the size
C is even that result is discarded, and is repeated by the main loop.
C
ASM_START()
PROLOGUE(mpn_hamdist)
C r16 xp
C r17 yp
C r18 size
ldq r1, 0(r16) C L0 xp[0]
ldq r2, 0(r17) C L1 yp[0]
and r18, 1, r8 C U1 1 if size odd
srl r18, 1, r18 C U0 size, limb pairs
clr r0 C L0 initial total
s8addq r8, r17, r17 C U1 yp++ if size odd
s8addq r8, r16, r16 C L1 xp++ if size odd
clr r6 C U0 dummy initial xor 1
xor r1, r2, r5 C L initial xor 0
beq r18, L(one) C U if size==1
cmoveq r8, r31, r5 C L discard first limb if size even
unop C U
ALIGN(16)
L(top):
C r0 total accumulating
C r7 xor 0
C r8 xor 1
C r16 xp, incrementing
C r17 yp, incrementing
C r18 size, limb pairs, decrementing
ldq r1, 0(r16) C L
ldq r2, 0(r17) C L
ctpop r5, r7 C U0
lda r16, 16(r16) C U
ldq r3, -8(r16) C L
ldq r4, 8(r17) C L
ctpop r6, r8 C U0
lda r17, 16(r17) C U
ldl r31, 256(r16) C L prefetch
ldl r31, 256(r17) C L prefetch
xor r1, r2, r5 C U
lda r18, -1(r18) C U
xor r3, r4, r6 C U
addq r0, r7, r0 C L
addq r0, r8, r0 C L
bne r18, L(top) C U
ctpop r6, r8 C U0
addq r0, r8, r0 C L
L(one):
ctpop r5, r7 C U0
addq r0, r7, r0 C L
ret r31, (r26), 1 C L0
EPILOGUE()
ASM_END()
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