diff options
Diffstat (limited to 'sysdeps/powerpc/sub_n.s')
| -rw-r--r-- | sysdeps/powerpc/sub_n.s | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/sysdeps/powerpc/sub_n.s b/sysdeps/powerpc/sub_n.s new file mode 100644 index 0000000000..8711bf9a40 --- /dev/null +++ b/sysdeps/powerpc/sub_n.s @@ -0,0 +1,69 @@ + # 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. + + # 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... + + .align 3 + .globl __mpn_sub_n + .type __mpn_sub_n,@function + nop +__mpn_sub_n: + # 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 |