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dnl x86 mpn_divexact_1 -- mpn by limb exact division.
dnl Copyright 2001, 2002 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 cycles/limb
C P54 30.0
C P55 29.0
C P6 13.0 odd divisor, 12.0 even (strangely)
C K6 14.0
C K7 12.0
C P4 42.0
C mp_limb_t mpn_divexact_1 (mp_ptr dst, mp_srcptr src, mp_size_t size,
C mp_limb_t divisor);
C
defframe(PARAM_DIVISOR,16)
defframe(PARAM_SIZE, 12)
defframe(PARAM_SRC, 8)
defframe(PARAM_DST, 4)
dnl re-use parameter space
define(VAR_INVERSE,`PARAM_SRC')
TEXT
ALIGN(16)
PROLOGUE(mpn_divexact_1)
deflit(`FRAME',0)
movl PARAM_DIVISOR, %eax
pushl %ebp FRAME_pushl()
movl PARAM_SIZE, %ebp
pushl %edi FRAME_pushl()
pushl %ebx FRAME_pushl()
movl $-1, %ecx C shift count
pushl %esi FRAME_pushl()
L(strip_twos):
incl %ecx
shrl %eax
jnc L(strip_twos)
leal 1(%eax,%eax), %ebx C d without twos
andl $127, %eax C d/2, 7 bits
ifdef(`PIC',`
call L(movl_eip_edx)
addl $_GLOBAL_OFFSET_TABLE_, %edx
movl modlimb_invert_table@GOT(%edx), %edx
movzbl (%eax,%edx), %eax C inv 8 bits
',`
dnl non-PIC
movzbl modlimb_invert_table(%eax), %eax C inv 8 bits
')
leal (%eax,%eax), %edx C 2*inv
movl %ebx, PARAM_DIVISOR C d without twos
imull %eax, %eax C inv*inv
movl PARAM_SRC, %esi
movl PARAM_DST, %edi
imull %ebx, %eax C inv*inv*d
subl %eax, %edx C inv = 2*inv - inv*inv*d
leal (%edx,%edx), %eax C 2*inv
imull %edx, %edx C inv*inv
leal (%esi,%ebp,4), %esi C src end
leal (%edi,%ebp,4), %edi C dst end
negl %ebp C -size
imull %ebx, %edx C inv*inv*d
subl %edx, %eax C inv = 2*inv - inv*inv*d
ASSERT(e,` C expect d*inv == 1 mod 2^BITS_PER_MP_LIMB
pushl %eax FRAME_pushl()
imull PARAM_DIVISOR, %eax
cmpl $1, %eax
popl %eax FRAME_popl()')
movl %eax, VAR_INVERSE
movl (%esi,%ebp,4), %eax C src[0]
xorl %ebx, %ebx
xorl %edx, %edx
incl %ebp
jz L(one)
movl (%esi,%ebp,4), %edx C src[1]
shrdl( %cl, %edx, %eax)
movl VAR_INVERSE, %edx
jmp L(entry)
ALIGN(8)
nop C k6 code alignment
nop
L(top):
C eax q
C ebx carry bit, 0 or -1
C ecx shift
C edx carry limb
C esi src end
C edi dst end
C ebp counter, limbs, negative
movl -4(%esi,%ebp,4), %eax
subl %ebx, %edx C accumulate carry bit
movl (%esi,%ebp,4), %ebx
shrdl( %cl, %ebx, %eax)
subl %edx, %eax C apply carry limb
movl VAR_INVERSE, %edx
sbbl %ebx, %ebx
L(entry):
imull %edx, %eax
movl %eax, -4(%edi,%ebp,4)
movl PARAM_DIVISOR, %edx
mull %edx
incl %ebp
jnz L(top)
movl -4(%esi), %eax C src high limb
L(one):
shrl %cl, %eax
popl %esi FRAME_popl()
addl %ebx, %eax C apply carry bit
popl %ebx FRAME_popl()
subl %edx, %eax C apply carry limb
imull VAR_INVERSE, %eax
movl %eax, -4(%edi)
popl %edi
popl %ebp
ret
ifdef(`PIC',`
L(movl_eip_edx):
movl (%esp), %edx
ret_internal
')
EPILOGUE()
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