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dnl Intel P5 mpn_hamdist -- mpn hamming distance.
dnl Copyright 2001, 2002 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 P5: 14.0 cycles/limb
C unsigned long mpn_hamdist (mp_srcptr src1, mp_srcptr src2, mp_size_t size);
C
C It might be possible to shave 1 cycle from the loop, and hence 2
C cycles/limb. The xorb is taking 2 cycles, but a separate load and xor
C would be 1, if the right schedule could be found (not found so far).
C Wanting to avoid potential cache bank clashes makes it tricky.
C The slightly strange quoting here helps the renaming done by tune/many.pl.
deflit(TABLE_NAME,
m4_assert_defined(`GSYM_PREFIX')
GSYM_PREFIX`'mpn_popcount``'_table')
defframe(PARAM_SIZE,12)
defframe(PARAM_SRC2, 8)
defframe(PARAM_SRC1, 4)
TEXT
ALIGN(8)
PROLOGUE(mpn_hamdist)
deflit(`FRAME',0)
movl PARAM_SIZE, %ecx
pushl %esi FRAME_pushl()
shll %ecx C size in byte pairs
pushl %edi FRAME_pushl()
ifdef(`PIC',`
pushl %ebx FRAME_pushl()
pushl %ebp FRAME_pushl()
call L(here) FRAME_pushl()
L(here):
movl PARAM_SRC1, %esi
popl %ebp FRAME_popl()
movl PARAM_SRC2, %edi
addl $_GLOBAL_OFFSET_TABLE_+[.-L(here)], %ebp
xorl %ebx, %ebx C byte
xorl %edx, %edx C byte
movl TABLE_NAME@GOT(%ebp), %ebp
xorl %eax, %eax C total
define(TABLE,`(%ebp,$1)')
',`
dnl non-PIC
movl PARAM_SRC1, %esi
movl PARAM_SRC2, %edi
xorl %eax, %eax C total
pushl %ebx FRAME_pushl()
xorl %edx, %edx C byte
xorl %ebx, %ebx C byte
define(TABLE,`TABLE_NAME($1)')
')
C The nop after the xorb seems necessary. Although a movb might be
C expected to go down the V pipe in the second cycle of the xorb, it
C doesn't and costs an extra 2 cycles.
L(top):
C eax total
C ebx byte
C ecx counter, 2*size to 2
C edx byte
C esi src1
C edi src2
C ebp [PIC] table
addl %ebx, %eax
movb -1(%esi,%ecx,2), %bl
addl %edx, %eax
movb -1(%edi,%ecx,2), %dl
xorb %dl, %bl
movb -2(%esi,%ecx,2), %dl
xorb -2(%edi,%ecx,2), %dl
nop
movb TABLE(%ebx), %bl
decl %ecx
movb TABLE(%edx), %dl
jnz L(top)
ifdef(`PIC',`
popl %ebp
')
addl %ebx, %eax
popl %ebx
addl %edx, %eax
popl %edi
popl %esi
ret
EPILOGUE()
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