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dnl AMD K6 mpn_preinv_mod_1 -- mpn by 1 remainder, with pre-inverted divisor.
dnl Copyright 2000, 2002, 2003 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 3 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 License
dnl along with the GNU MP Library. If not, see http://www.gnu.org/licenses/.
include(`../config.m4')
C K6: 18.0 cycles/limb
C mp_limb_t mpn_preinv_mod_1 (mp_srcptr src, mp_size_t size, mp_limb_t divisor,
C mp_limb_t inverse);
C
C This code is only 2 c/l faster than a simple divl, but that's 10% so it's
C considered worthwhile (just).
defframe(PARAM_INVERSE,16)
defframe(PARAM_DIVISOR,12)
defframe(PARAM_SIZE, 8)
defframe(PARAM_SRC, 4)
TEXT
ALIGN(32)
PROLOGUE(mpn_preinv_mod_1)
deflit(`FRAME',0)
ASSERT(ae,`cmpl $1, PARAM_SIZE')
ASSERT(nz,`testl $0x80000000, PARAM_DIVISOR')
movl PARAM_SIZE, %ecx
pushl %ebp FRAME_pushl()
movl PARAM_SRC, %ebp
pushl %edi FRAME_pushl()
movl PARAM_DIVISOR, %eax
pushl %esi FRAME_pushl()
movl -4(%ebp,%ecx,4), %esi C src high limb
pushl %ebx FRAME_pushl()
movl %edx, %edi C first n2 to cancel
subl %eax, %esi C first n1 = high-divisor
decl %ecx
jz L(done_sbbl)
L(top):
C eax scratch
C ebx n10, nadj, q1
C ecx counter, size to 1
C edx scratch
C esi n2
C edi old high, for underflow test
C ebp src
sbbl %edx, %edi C high n-(q1+1)*d, 0 or -1
L(entry):
andl PARAM_DIVISOR, %edi
L(q1_ff_top):
movl -4(%ebp,%ecx,4), %ebx
addl %esi, %edi C possible addback
movl %ebx, %esi C n10
sarl $31, %ebx C -n1 = 0 or -1
movl %edi, %eax C n2
movl PARAM_INVERSE, %edx
subl %ebx, %eax C n2+n1
mull %edx C m*(n2+n1)
andl PARAM_DIVISOR, %ebx C -n1 & d
addl %esi, %ebx C nadj = n10 + (-n1&d), ignoring overflow
addl %ebx, %eax C low m*(n2+n1) + nadj, giving carry flag
leal 1(%edi), %ebx C n2+1
adcl %ebx, %edx C 1+high(n2<<32+m*(n2+n1)+nadj) = q1+1
movl PARAM_DIVISOR, %eax C d
jz L(q1_ff)
mull %edx C (q1+1)*d
subl %eax, %esi C low n-(q1+1)*d
loop L(top)
L(done_sbbl):
sbbl %edx, %edi C high n-(q1+1)*d, 0 or -1
andl PARAM_DIVISOR, %edi
L(done_esi_edi):
popl %ebx
leal (%esi,%edi), %eax
popl %esi
popl %edi
popl %ebp
ret
C Special case for q1=0xFFFFFFFF, giving q=0xFFFFFFFF meaning the low dword
C of q*d is simply -d and the remainder n-q*d = n10+d. This is rarely
C reached.
L(q1_ff):
movl PARAM_DIVISOR, %edi
loop L(q1_ff_top)
jmp L(done_esi_edi)
EPILOGUE()
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