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dnl AMD K6 mpn_divexact_by3 -- mpn division by 3, expecting no remainder.
dnl
dnl K6: 11.0 cycles/limb
dnl Copyright (C) 2000 Free Software Foundation, Inc.
dnl
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
dnl modify it under the terms of the GNU Lesser General Public License as
dnl published by the Free Software Foundation; either version 2.1 of the
dnl License, or (at your option) any later version.
dnl
dnl The GNU MP Library is distributed in the hope that it will be useful,
dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
dnl Lesser General Public License for more details.
dnl
dnl You should have received a copy of the GNU Lesser General Public
dnl License along with the GNU MP Library; see the file COPYING.LIB. If
dnl not, write to the Free Software Foundation, Inc., 59 Temple Place -
dnl Suite 330, Boston, MA 02111-1307, USA.
include(`../config.m4')
C mp_limb_t mpn_divexact_by3c (mp_ptr dst, mp_srcptr src, mp_size_t size,
C mp_limb_t carry);
C
C Using %esi in (%esi,%ecx,4) or 0(%esi,%ecx,4) addressing modes doesn't
C lead to vector decoding, unlike plain (%esi) does.
defframe(PARAM_CARRY,16)
defframe(PARAM_SIZE, 12)
defframe(PARAM_SRC, 8)
defframe(PARAM_DST, 4)
dnl multiplicative inverse of 3, modulo 2^32
deflit(INVERSE_3, 0xAAAAAAAB)
.text
ALIGN(32)
PROLOGUE(mpn_divexact_by3c)
deflit(`FRAME',0)
movl PARAM_SIZE, %ecx
pushl %esi defframe_pushl(SAVE_ESI)
movl PARAM_SRC, %esi
pushl %edi defframe_pushl(SAVE_EDI)
movl PARAM_DST, %edi
pushl %ebx defframe_pushl(SAVE_EBX)
movl PARAM_CARRY, %ebx
leal (%esi,%ecx,4), %esi
pushl $3 defframe_pushl(VAR_THREE)
leal (%edi,%ecx,4), %edi
negl %ecx
C Need 32 alignment for claimed speed, to avoid the movl store
C opcode/modrm crossing a cache line boundary
ALIGN(32)
L(top):
C eax scratch, low product
C ebx carry limb (0 to 3)
C ecx counter, limbs, negative
C edx scratch, high product
C esi &src[size]
C edi &dst[size]
C ebp
C
C The 0(%esi,%ecx,4) form pads so the finishup "movl %ebx, %eax"
C doesn't cross a 32 byte boundary, saving a couple of cycles
C (that's a fixed couple, not per loop).
Zdisp( movl, 0,(%esi,%ecx,4), %eax)
subl %ebx, %eax
setc %bl
imull $INVERSE_3, %eax
movl %eax, (%edi,%ecx,4)
addl $2, %ecx
mull VAR_THREE
addl %edx, %ebx
loop L(top)
movl SAVE_ESI, %esi
movl %ebx, %eax
movl SAVE_EBX, %ebx
movl SAVE_EDI, %edi
addl $FRAME, %esp
ret
EPILOGUE()
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