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

1.1     ! maekawa     1: dnl  x86 mpn_divexact_by3 -- mpn division by 3, expecting no remainder.
        !             2:
        !             3:
        !             4: dnl  Copyright (C) 2000 Free Software Foundation, Inc.
        !             5: dnl
        !             6: dnl  This file is part of the GNU MP Library.
        !             7: dnl
        !             8: dnl  The GNU MP Library is free software; you can redistribute it and/or
        !             9: dnl  modify it under the terms of the GNU Lesser General Public License as
        !            10: dnl  published by the Free Software Foundation; either version 2.1 of the
        !            11: dnl  License, or (at your option) any later version.
        !            12: dnl
        !            13: dnl  The GNU MP Library is distributed in the hope that it will be useful,
        !            14: dnl  but WITHOUT ANY WARRANTY; without even the implied warranty of
        !            15: dnl  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
        !            16: dnl  Lesser General Public License for more details.
        !            17: dnl
        !            18: dnl  You should have received a copy of the GNU Lesser General Public
        !            19: dnl  License along with the GNU MP Library; see the file COPYING.LIB.  If
        !            20: dnl  not, write to the Free Software Foundation, Inc., 59 Temple Place -
        !            21: dnl  Suite 330, Boston, MA 02111-1307, USA.
        !            22:
        !            23:
        !            24: dnl  The following all have their own optimized versions of this routine,
        !            25: dnl  but for reference the code here runs as follows.
        !            26: dnl
        !            27: dnl       cycles/limb
        !            28: dnl  P54     18.0
        !            29: dnl  P55     17.0
        !            30: dnl  P6      14.5
        !            31: dnl  K6      14.0
        !            32: dnl  K7      10.0
        !            33:
        !            34:
        !            35: include(`../config.m4')
        !            36:
        !            37:
        !            38: C mp_limb_t mpn_divexact_by3c (mp_ptr dst, mp_srcptr src, mp_size_t size,
        !            39: C                              mp_limb_t carry);
        !            40:
        !            41: defframe(PARAM_CARRY,16)
        !            42: defframe(PARAM_SIZE, 12)
        !            43: defframe(PARAM_SRC,   8)
        !            44: defframe(PARAM_DST,   4)
        !            45:
        !            46: dnl  multiplicative inverse of 3, modulo 2^32
        !            47: deflit(INVERSE_3,       0xAAAAAAAB)
        !            48:
        !            49: dnl  ceil(b/3) and ceil(b*2/3) where b=2^32
        !            50: deflit(ONE_THIRD_CEIL,  0x55555556)
        !            51: deflit(TWO_THIRDS_CEIL, 0xAAAAAAAB)
        !            52:
        !            53:        .text
        !            54:        ALIGN(8)
        !            55:
        !            56: PROLOGUE(mpn_divexact_by3c)
        !            57: deflit(`FRAME',0)
        !            58:
        !            59:        movl    PARAM_SRC, %ecx
        !            60:        pushl   %ebp            FRAME_pushl()
        !            61:
        !            62:        movl    PARAM_SIZE, %ebp
        !            63:        pushl   %edi            FRAME_pushl()
        !            64:
        !            65:        movl    PARAM_DST, %edi
        !            66:        pushl   %esi            FRAME_pushl()
        !            67:
        !            68:        movl    $INVERSE_3, %esi
        !            69:        pushl   %ebx            FRAME_pushl()
        !            70:
        !            71:        leal    (%ecx,%ebp,4), %ecx
        !            72:        movl    PARAM_CARRY, %ebx
        !            73:
        !            74:        leal    (%edi,%ebp,4), %edi
        !            75:        negl    %ebp
        !            76:
        !            77:
        !            78:        ALIGN(8)
        !            79: L(top):
        !            80:        C eax   scratch, low product
        !            81:        C ebx   carry limb (0 to 3)
        !            82:        C ecx   &src[size]
        !            83:        C edx   scratch, high product
        !            84:        C esi   multiplier
        !            85:        C edi   &dst[size]
        !            86:        C ebp   counter, limbs, negative
        !            87:
        !            88:        movl    (%ecx,%ebp,4), %eax
        !            89:
        !            90:        subl    %ebx, %eax
        !            91:
        !            92:        setc    %bl
        !            93:
        !            94:        imull   %esi
        !            95:
        !            96:        cmpl    $ONE_THIRD_CEIL, %eax
        !            97:        movl    %eax, (%edi,%ebp,4)
        !            98:
        !            99:        sbbl    $-1, %ebx       C +1 if eax>=ceil(b/3)
        !           100:        cmpl    $TWO_THIRDS_CEIL, %eax
        !           101:
        !           102:        sbbl    $-1, %ebx       C +1 if eax>=ceil(b*2/3)
        !           103:        incl    %ebp
        !           104:
        !           105:        jnz     L(top)
        !           106:
        !           107:
        !           108:        movl    %ebx, %eax
        !           109:        popl    %ebx
        !           110:        popl    %esi
        !           111:        popl    %edi
        !           112:        popl    %ebp
        !           113:        ret
        !           114:
        !           115: EPILOGUE()