text: dnl  AMD K6 mpn_divexact_by3 -- mpn division by 3, expecting no remainder.
  
  dnl  Copyright 2000, 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., 51 Franklin Street,
  dnl  Fifth Floor, Boston, MA 02110-1301, USA.
  
  include(`../config.m4')
  
  
  C K6: 10.0 cycles/limb
  
  
  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(16)
  
  	nop	C code alignment
  
  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, %edx
  	leal	(%esi,%ecx,4), %esi
  
  	pushl	%ebp		defframe_pushl(SAVE_EBP)
  	movl	$3, %ebp
  
  	leal	0(%edi,%ecx,4), %edi
  	negl	%ecx
  
  
  L(top):
  	C eax	scratch, low product
  	C ebx	carry limb (0 to 2)
  	C ecx	counter, limbs, negative
  	C edx	scratch, high product
  	C esi	&src[size]
  	C edi	&dst[size]
  	C ebp	3
  
  	movl	(%esi,%ecx,4), %eax
  	subl	%edx, %eax
  
  	sbbl	%ebx, %ebx		C borrow 0 or -1
  
  	imull	$INVERSE_3, %eax, %eax
  
  	movl	%eax, (%edi,%ecx,4)
  	addl	$2, %ecx
  
  	mull	%ebp
  
  	subl	%ebx, %edx		C new carry
  	loop	L(top)
  
  
  	movl	SAVE_ESI, %esi
  	movl	%edx, %eax
  
  	movl	SAVE_EBX, %ebx
  
  	movl	SAVE_EBP, %ebp
  
  	movl	SAVE_EDI, %edi
  	addl	$FRAME, %esp
  
  	ret
  
  EPILOGUE()
  