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Annotation of OpenXM_contrib/gmp/mpn/x86/pentium4/sse2/diveby3.asm, Revision 1.1

1.1     ! ohara       1: dnl  Intel Pentium-4 mpn_divexact_by3 -- mpn exact division by 3.
        !             2:
        !             3: dnl  Copyright 2001, 2002 Free Software Foundation, Inc.
        !             4: dnl
        !             5: dnl  This file is part of the GNU MP Library.
        !             6: dnl
        !             7: dnl  The GNU MP Library is free software; you can redistribute it and/or
        !             8: dnl  modify it under the terms of the GNU Library General Public License as
        !             9: dnl  published by the Free Software Foundation; either version 2 of the
        !            10: dnl  License, or (at your option) any later version.
        !            11: dnl
        !            12: dnl  The GNU MP Library is distributed in the hope that it will be useful,
        !            13: dnl  but WITHOUT ANY WARRANTY; without even the implied warranty of
        !            14: dnl  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
        !            15: dnl  Library General Public License for more details.
        !            16: dnl
        !            17: dnl  You should have received a copy of the GNU Library General Public
        !            18: dnl  License along with the GNU MP Library; see the file COPYING.LIB.  If
        !            19: dnl  not, write to the Free Software Foundation, Inc., 59 Temple Place -
        !            20: dnl  Suite 330, Boston, MA 02111-1307, USA.
        !            21:
        !            22: include(`../config.m4')
        !            23:
        !            24:
        !            25: C P4: 18.0 cycles/limb
        !            26:
        !            27:
        !            28: C mp_limb_t mpn_divexact_by3c (mp_ptr dst, mp_srcptr src, mp_size_t size,
        !            29: C                              mp_limb_t carry);
        !            30: C
        !            31: C The dependent chain in the loop is as follows, and this is what the code
        !            32: C measures.
        !            33: C
        !            34: C      psubq     (src-cbit) - climb    2
        !            35: C      pmuludq   s*inverse             8
        !            36: C      pand      mask q                2
        !            37: C      psllq     2*q                   2
        !            38: C      paddq     q+2*q                 2
        !            39: C      psrlq     high(3*q)             2
        !            40: C                                     --
        !            41: C                                     18
        !            42: C
        !            43: C Perhaps the s*inverse can be taken off the dependent chain as described in
        !            44: C mpn/generic/diveby3.c, with a modified 3*q calculation that can give
        !            45: C high(3*q)*inv too.
        !            46:
        !            47:
        !            48: defframe(PARAM_CARRY,16)
        !            49: defframe(PARAM_SIZE, 12)
        !            50: defframe(PARAM_SRC,   8)
        !            51: defframe(PARAM_DST,   4)
        !            52:
        !            53:        RODATA
        !            54: C multiplicative inverse of 3, modulo 2^32
        !            55:        ALIGN(4)
        !            56: L(inverse):
        !            57:        .long   0xAAAAAAAB
        !            58:
        !            59:        TEXT
        !            60:        ALIGN(16)
        !            61:
        !            62: PROLOGUE(mpn_divexact_by3c)
        !            63: deflit(`FRAME',0)
        !            64:
        !            65:        movl    PARAM_SRC, %eax
        !            66:        pxor    %mm0, %mm0
        !            67:
        !            68:        movd    PARAM_CARRY, %mm1
        !            69:        pcmpeqd %mm6, %mm6
        !            70:
        !            71:        movd    L(inverse), %mm7
        !            72:
        !            73:        movl    PARAM_DST, %edx
        !            74:        psrlq   $32, %mm6               C 0x00000000FFFFFFFF
        !            75:
        !            76:        movl    PARAM_SIZE, %ecx
        !            77:
        !            78: L(top):
        !            79:        C eax   src, incrementing
        !            80:        C ebx
        !            81:        C ecx   counter, limbs, decrementing
        !            82:        C edx   dst, incrementing
        !            83:        C
        !            84:        C mm0   carry bit
        !            85:        C mm1   carry limb
        !            86:        C mm6   0x00000000FFFFFFFF
        !            87:        C mm7   inverse
        !            88:
        !            89:        movd    (%eax), %mm2
        !            90:        addl    $4, %eax
        !            91:
        !            92:        psubq   %mm0, %mm2              C src - cbit
        !            93:
        !            94:        psubq   %mm1, %mm2              C src - cbit - climb
        !            95:        movq    %mm2, %mm0
        !            96:        psrlq   $63, %mm0               C new cbit
        !            97:
        !            98:        pmuludq %mm7, %mm2              C s*inverse
        !            99:        movd    %mm2, (%edx)            C q
        !           100:        addl    $4, %edx
        !           101:
        !           102:        movq    %mm6, %mm1
        !           103:
        !           104:        pand    %mm2, %mm1
        !           105:
        !           106:        pand    %mm6, %mm2
        !           107:
        !           108:        psllq   $1, %mm1
        !           109:
        !           110:        C
        !           111:
        !           112:        paddq   %mm2, %mm1
        !           113:
        !           114:        C
        !           115:
        !           116:        psrlq   $32, %mm1
        !           117:
        !           118:        subl    $1, %ecx
        !           119:        jnz     L(top)
        !           120:
        !           121:
        !           122:        paddd   %mm1, %mm0
        !           123:        movd    %mm0, %eax
        !           124:        emms
        !           125:        ret
        !           126:
        !           127: EPILOGUE()