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Annotation of OpenXM_contrib/gmp/mpn/alpha/rshift.asm, Revision 1.1

1.1     ! maekawa     1: dnl  Alpha mpn_rshift -- Shift a number right.
        !             2:
        !             3: dnl  Copyright (C) 1994, 1995, 2000 Free Software Foundation, Inc.
        !             4:
        !             5: dnl  This file is part of the GNU MP Library.
        !             6:
        !             7: dnl  The GNU MP Library is free software; you can redistribute it and/or modify
        !             8: dnl  it under the terms of the GNU Lesser General Public License as published by
        !             9: dnl  the Free Software Foundation; either version 2.1 of the License, or (at your
        !            10: dnl  option) any later version.
        !            11:
        !            12: dnl  The GNU MP Library is distributed in the hope that it will be useful, but
        !            13: dnl  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
        !            14: dnl  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
        !            15: dnl  License for more details.
        !            16:
        !            17: dnl  You should have received a copy of the GNU Lesser General Public License
        !            18: dnl  along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
        !            19: dnl  the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
        !            20: dnl  MA 02111-1307, USA.
        !            21:
        !            22: include(`../config.m4')
        !            23:
        !            24: dnl  INPUT PARAMETERS
        !            25: dnl  res_ptr   r16
        !            26: dnl  s1_ptr    r17
        !            27: dnl  size      r18
        !            28: dnl  cnt       r19
        !            29:
        !            30: dnl  This code runs at 4.8 cycles/limb on the 21064.  With infinite unrolling,
        !            31: dnl  it would take 4 cycles/limb.  It should be possible to get down to 3
        !            32: dnl  cycles/limb since both ldq and stq can be paired with the other used
        !            33: dnl  instructions.  But there are many restrictions in the 21064 pipeline that
        !            34: dnl  makes it hard, if not impossible, to get down to 3 cycles/limb:
        !            35:
        !            36: dnl  1. ldq has a 3 cycle delay, srl and sll have a 2 cycle delay.
        !            37: dnl  2. Only aligned instruction pairs can be paired.
        !            38: dnl  3. The store buffer or silo might not be able to deal with the bandwidth.
        !            39:
        !            40: ASM_START()
        !            41: PROLOGUE(mpn_rshift)
        !            42:        ldq     r4,0(r17)       C load first limb
        !            43:        addq    r17,8,r17
        !            44:        subq    r31,r19,r7
        !            45:        subq    r18,1,r18
        !            46:        and     r18,4-1,r20     C number of limbs in first loop
        !            47:        sll     r4,r7,r0        C compute function result
        !            48:
        !            49:        beq     r20,$L0
        !            50:        subq    r18,r20,r18
        !            51:
        !            52:        ALIGN(8)
        !            53: $Loop0:
        !            54:        ldq     r3,0(r17)
        !            55:        addq    r16,8,r16
        !            56:        addq    r17,8,r17
        !            57:        subq    r20,1,r20
        !            58:        srl     r4,r19,r5
        !            59:        sll     r3,r7,r6
        !            60:        bis     r3,r3,r4
        !            61:        bis     r5,r6,r8
        !            62:        stq     r8,-8(r16)
        !            63:        bne     r20,$Loop0
        !            64:
        !            65: $L0:   beq     r18,$Lend
        !            66:
        !            67:        ALIGN(8)
        !            68: $Loop: ldq     r3,0(r17)
        !            69:        addq    r16,32,r16
        !            70:        subq    r18,4,r18
        !            71:        srl     r4,r19,r5
        !            72:        sll     r3,r7,r6
        !            73:
        !            74:        ldq     r4,8(r17)
        !            75:        srl     r3,r19,r1
        !            76:        bis     r5,r6,r8
        !            77:        stq     r8,-32(r16)
        !            78:        sll     r4,r7,r2
        !            79:
        !            80:        ldq     r3,16(r17)
        !            81:        srl     r4,r19,r5
        !            82:        bis     r1,r2,r8
        !            83:        stq     r8,-24(r16)
        !            84:        sll     r3,r7,r6
        !            85:
        !            86:        ldq     r4,24(r17)
        !            87:        srl     r3,r19,r1
        !            88:        bis     r5,r6,r8
        !            89:        stq     r8,-16(r16)
        !            90:        sll     r4,r7,r2
        !            91:
        !            92:        addq    r17,32,r17
        !            93:        bis     r1,r2,r8
        !            94:        stq     r8,-8(r16)
        !            95:
        !            96:        bgt     r18,$Loop
        !            97:
        !            98: $Lend: srl     r4,r19,r8
        !            99:        stq     r8,0(r16)
        !           100:        ret     r31,(r26),1
        !           101: EPILOGUE(mpn_rshift)
        !           102: ASM_END()