/* Subtract two limb vectors of equal, non-zero length for PowerPC.
   Copyright (C) 1997 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <sysdep.h>

/* mp_limb_t mpn_sub_n (mp_ptr res_ptr, mp_srcptr s1_ptr, mp_srcptr s2_ptr,
                        mp_size_t size)
   Calculate s1-s2 and put result in res_ptr; return borrow, 0 or 1.  */

/* Note on optimisation: This code is optimal for the 601.  Almost every other
   possible 2-unrolled inner loop will not be.  Also, watch out for the
   alignment...  */

EALIGN(__mpn_sub_n,3,1)
/* Set up for loop below.  */
	mtcrf 0x01,%r6
	srwi. %r7,%r6,1
	mtctr %r7
	bt    31,2f

/* Set the carry (clear the borrow).  */
	subfc %r0,%r0,%r0
/* Adjust pointers for loop.  */
	addi  %r3,%r3,-4
	addi  %r4,%r4,-4
	addi  %r5,%r5,-4
	b     0f

2:	lwz   %r7,0(%r5)
	lwz   %r6,0(%r4)
	subfc %r6,%r7,%r6
	stw   %r6,0(%r3)
        beq   1f

/* Align start of loop to an odd word boundary to guarantee that the
   last two words can be fetched in one access (for 601).  This turns
   out to be important.  */
0:
	lwz   %r9,4(%r4)
	lwz   %r8,4(%r5)
	lwzu  %r6,8(%r4)
	lwzu  %r7,8(%r5)
	subfe %r8,%r8,%r9
	stw   %r8,4(%r3)
	subfe %r6,%r7,%r6
	stwu  %r6,8(%r3)
	bdnz  0b
/* Return the borrow. */
1:	subfe %r3,%r3,%r3
	neg   %r3,%r3
	blr
END(__mpn_sub_n)
