/* 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)