1 # Alpha 21064 __mpn_rshift --
3 # Copyright (C) 1994, 1995 Free Software Foundation, Inc.
5 # This file is part of the GNU MP Library.
7 # The GNU MP Library is free software; you can redistribute it and/or modify
8 # it under the terms of the GNU Lesser General Public License as published by
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13 # WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14 # or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
15 # License for more details.
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18 # along with the GNU MP Library; see the file COPYING.LIB. If not, write to
19 # the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
29 # This code runs at 4.8 cycles/limb on the 21064. With infinite unrolling,
30 # it would take 4 cycles/limb. It should be possible to get down to 3
31 # cycles/limb since both ldq and stq can be paired with the other used
32 # instructions. But there are many restrictions in the 21064 pipeline that
33 # makes it hard, if not impossible, to get down to 3 cycles/limb:
35 # 1. ldq has a 3 cycle delay, srl and sll have a 2 cycle delay.
36 # 2. Only aligned instruction pairs can be paired.
37 # 3. The store buffer or silo might not be able to deal with the bandwidth.
48 ldq $4,0($17) # load first limb
52 and $18,4-1,$20 # number of limbs in first loop
53 sll $4,$7,$0 # compute function result