/* Subtract two limb vectors of equal, non-zero length for PowerPC.
   Copyright (C) 1997, 1999, 2000 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 Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.

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

#include <sysdep.h>
#include <bp-sym.h>
#include <bp-asm.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 (BP_SYM (__mpn_sub_n), 3, 1)

#if __BOUNDED_POINTERS__
        slwi r10,r6,2           /* convert limbs to bytes */
        CHECK_BOUNDS_BOTH_WIDE (r3, r8, r9, r10)
        CHECK_BOUNDS_BOTH_WIDE (r4, r8, r9, r10)
        CHECK_BOUNDS_BOTH_WIDE (r5, r8, r9, r10)
#endif

/* Set up for loop below.  */
        mtcrf 0x01,r6
        srwi. r7,r6,1
        mtctr r7
        bt    31,L(2)

/* 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     L(0)

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

/* 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.  */
L(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  L(0)
/* Return the borrow. */
L(1):   subfe r3,r3,r3
        neg   r3,r3
        blr
END (BP_SYM (__mpn_sub_n))