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120 lines
2.9 KiB
ArmAsm
120 lines
2.9 KiB
ArmAsm
/* alpha rshift
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* Copyright (C) 1994, 1995, 1998, 1999,
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* 2000, 2001 Free Software Foundation, Inc.
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*
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* This file is part of GNUPG.
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*
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* GNUPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* GNUPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*
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* Note: This code is heavily based on the GNU MP Library.
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* Actually it's the same code with only minor changes in the
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* way the data is stored; this is to support the abstraction
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* of an optional secure memory allocation which may be used
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* to avoid revealing of sensitive data due to paging etc.
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* The GNU MP Library itself is published under the LGPL;
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* however I decided to publish this code under the plain GPL.
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*/
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/*******************
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* mpi_limb_t
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* mpihelp_rshift( mpi_ptr_t wp, (r16)
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* mpi_ptr_t up, (r17)
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* mpi_size_t usize, (r18)
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* unsigned cnt) (r19)
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*
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* This code runs at 4.8 cycles/limb on the 21064. With infinite unrolling,
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* it would take 4 cycles/limb. It should be possible to get down to 3
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* cycles/limb since both ldq and stq can be paired with the other used
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* instructions. But there are many restrictions in the 21064 pipeline that
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* makes it hard, if not impossible, to get down to 3 cycles/limb:
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*
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* 1. ldq has a 3 cycle delay, srl and sll have a 2 cycle delay.
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* 2. Only aligned instruction pairs can be paired.
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* 3. The store buffer or silo might not be able to deal with the bandwidth.
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*/
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.set noreorder
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.set noat
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.text
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.align 3
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.globl mpihelp_rshift
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.ent mpihelp_rshift
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mpihelp_rshift:
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.frame $30,0,$26,0
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ldq $4,0($17) # load first limb
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addq $17,8,$17
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subq $31,$19,$7
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subq $18,1,$18
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and $18,4-1,$20 # number of limbs in first loop
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sll $4,$7,$0 # compute function result
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beq $20,.R0
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subq $18,$20,$18
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.align 3
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.Roop0:
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ldq $3,0($17)
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addq $16,8,$16
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addq $17,8,$17
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subq $20,1,$20
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srl $4,$19,$5
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sll $3,$7,$6
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bis $3,$3,$4
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bis $5,$6,$8
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stq $8,-8($16)
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bne $20,.Roop0
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.R0: beq $18,.Rend
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.align 3
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.Roop: ldq $3,0($17)
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addq $16,32,$16
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subq $18,4,$18
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srl $4,$19,$5
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sll $3,$7,$6
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ldq $4,8($17)
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srl $3,$19,$1
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bis $5,$6,$8
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stq $8,-32($16)
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sll $4,$7,$2
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ldq $3,16($17)
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srl $4,$19,$5
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bis $1,$2,$8
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stq $8,-24($16)
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sll $3,$7,$6
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ldq $4,24($17)
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srl $3,$19,$1
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bis $5,$6,$8
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stq $8,-16($16)
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sll $4,$7,$2
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addq $17,32,$17
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bis $1,$2,$8
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stq $8,-8($16)
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bgt $18,.Roop
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.Rend: srl $4,$19,$8
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stq $8,0($16)
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ret $31,($26),1
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.end mpihelp_rshift
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