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/* 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)
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