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; mc88100 __mpn_sub -- Subtract two limb vectors of the same length > 0 and
; store difference in a third limb vector.
; Copyright (C) 1992, 1994, 1996 Free Software Foundation, Inc.
; This file is part of the GNU MP Library.
; The GNU MP 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 MP 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 MP Library; see the file COPYING.LIB. If not, write to
; the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
; INPUT PARAMETERS
; res_ptr r2
; s1_ptr r3
; s2_ptr r4
; size r5
; This code has been optimized to run one instruction per clock, avoiding
; load stalls and writeback contention. As a result, the instruction
; order is not always natural.
; The speed is about 4.6 clocks/limb + 18 clocks/limb-vector on an 88100,
; but on the 88110, it seems to run much slower, 6.6 clocks/limb.
text
align 16
global ___mpn_sub_n
___mpn_sub_n:
ld r6,r3,0 ; read first limb from s1_ptr
extu r10,r5,3
ld r7,r4,0 ; read first limb from s2_ptr
subu r5,r0,r5
mak r5,r5,3<4>
bcnd.n eq0,r5,Lzero
subu.co r0,r0,r0 ; initialize carry
or r12,r0,lo16(Lbase)
or.u r12,r12,hi16(Lbase)
addu r12,r12,r5 ; r12 is address for entering in loop
extu r5,r5,2 ; divide by 4
subu r2,r2,r5 ; adjust res_ptr
subu r3,r3,r5 ; adjust s1_ptr
subu r4,r4,r5 ; adjust s2_ptr
or r8,r6,r0
jmp.n r12
or r9,r7,r0
Loop: addu r3,r3,32
st r8,r2,28
addu r4,r4,32
ld r6,r3,0
addu r2,r2,32
ld r7,r4,0
Lzero: subu r10,r10,1 ; subtract 0 + 8r limbs (adj loop cnt)
Lbase: ld r8,r3,4
subu.cio r6,r6,r7
ld r9,r4,4
st r6,r2,0
ld r6,r3,8 ; subtract 7 + 8r limbs
subu.cio r8,r8,r9
ld r7,r4,8
st r8,r2,4
ld r8,r3,12 ; subtract 6 + 8r limbs
subu.cio r6,r6,r7
ld r9,r4,12
st r6,r2,8
ld r6,r3,16 ; subtract 5 + 8r limbs
subu.cio r8,r8,r9
ld r7,r4,16
st r8,r2,12
ld r8,r3,20 ; subtract 4 + 8r limbs
subu.cio r6,r6,r7
ld r9,r4,20
st r6,r2,16
ld r6,r3,24 ; subtract 3 + 8r limbs
subu.cio r8,r8,r9
ld r7,r4,24
st r8,r2,20
ld r8,r3,28 ; subtract 2 + 8r limbs
subu.cio r6,r6,r7
ld r9,r4,28
st r6,r2,24
bcnd.n ne0,r10,Loop ; subtract 1 + 8r limbs
subu.cio r8,r8,r9
st r8,r2,28 ; store most significant limb
addu.ci r2,r0,r0 ; return carry-out from most sign. limb
jmp.n r1
xor r2,r2,1
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