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dnl Alpha mpn_rshift -- Shift a number right.
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dnl Copyright 1994, 1995, 2000 Free Software Foundation, Inc.
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dnl Copyright 1994, 1995, 2000, 2002 Free Software Foundation, Inc.
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dnl This file is part of the GNU MP Library.
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dnl License for more details.
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dnl You should have received a copy of the GNU Lesser General Public License
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dnl along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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dnl the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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dnl MA 02111-1307, USA.
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dnl along with the GNU MP Library; see the file COPYING.LIB. If not, write
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dnl to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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dnl Boston, MA 02110-1301, USA.
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include(`../config.m4')
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dnl This code runs at 4.8 cycles/limb on the 21064. With infinite unrolling,
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dnl it would take 4 cycles/limb. It should be possible to get down to 3
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dnl cycles/limb since both ldq and stq can be paired with the other used
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dnl instructions. But there are many restrictions in the 21064 pipeline that
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dnl makes it hard, if not impossible, to get down to 3 cycles/limb:
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dnl 1. ldq has a 3 cycle delay, srl and sll have a 2 cycle delay.
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dnl 2. Only aligned instruction pairs can be paired.
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dnl 3. The store buffer or silo might not be able to deal with the bandwidth.
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PROLOGUE(mpn_rshift)