Annotation of OpenXM_contrib/gmp/mpn/x86/k7/diveby3.asm, Revision 1.1
1.1 ! maekawa 1: dnl AMD K7 mpn_divexact_by3 -- mpn division by 3, expecting no remainder.
! 2: dnl
! 3: dnl K7: 8.0 cycles/limb
! 4:
! 5:
! 6: dnl Copyright (C) 2000 Free Software Foundation, Inc.
! 7: dnl
! 8: dnl This file is part of the GNU MP Library.
! 9: dnl
! 10: dnl The GNU MP Library is free software; you can redistribute it and/or
! 11: dnl modify it under the terms of the GNU Lesser General Public License as
! 12: dnl published by the Free Software Foundation; either version 2.1 of the
! 13: dnl License, or (at your option) any later version.
! 14: dnl
! 15: dnl The GNU MP Library is distributed in the hope that it will be useful,
! 16: dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
! 17: dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
! 18: dnl Lesser General Public License for more details.
! 19: dnl
! 20: dnl You should have received a copy of the GNU Lesser General Public
! 21: dnl License along with the GNU MP Library; see the file COPYING.LIB. If
! 22: dnl not, write to the Free Software Foundation, Inc., 59 Temple Place -
! 23: dnl Suite 330, Boston, MA 02111-1307, USA.
! 24:
! 25:
! 26: include(`../config.m4')
! 27:
! 28:
! 29: C mp_limb_t mpn_divexact_by3c (mp_ptr dst, mp_srcptr src, mp_size_t size,
! 30: C mp_limb_t carry);
! 31:
! 32: defframe(PARAM_CARRY,16)
! 33: defframe(PARAM_SIZE, 12)
! 34: defframe(PARAM_SRC, 8)
! 35: defframe(PARAM_DST, 4)
! 36:
! 37: dnl multiplicative inverse of 3, modulo 2^32
! 38: deflit(INVERSE_3, 0xAAAAAAAB)
! 39:
! 40: dnl ceil(b/3) and floor(b*2/3) where b=2^32
! 41: deflit(ONE_THIRD_CEIL, 0x55555556)
! 42: deflit(TWO_THIRDS_FLOOR, 0xAAAAAAAA)
! 43:
! 44: .text
! 45: ALIGN(32)
! 46:
! 47: PROLOGUE(mpn_divexact_by3c)
! 48: deflit(`FRAME',0)
! 49:
! 50: movl PARAM_SRC, %ecx
! 51: pushl %ebx defframe_pushl(SAVE_EBX)
! 52:
! 53: movl PARAM_CARRY, %ebx
! 54: pushl %ebp defframe_pushl(SAVE_EBP)
! 55:
! 56: movl PARAM_SIZE, %ebp
! 57: pushl %edi defframe_pushl(SAVE_EDI)
! 58:
! 59: movl (%ecx), %eax C src low limb
! 60: pushl %esi defframe_pushl(SAVE_ESI)
! 61:
! 62: movl PARAM_DST, %edi
! 63: movl $TWO_THIRDS_FLOOR, %esi
! 64: leal -4(%ecx,%ebp,4), %ecx C &src[size-1]
! 65:
! 66: subl %ebx, %eax
! 67:
! 68: setc %bl
! 69: decl %ebp
! 70: jz L(last)
! 71:
! 72: leal (%edi,%ebp,4), %edi C &dst[size-1]
! 73: negl %ebp
! 74:
! 75:
! 76: ALIGN(16)
! 77: L(top):
! 78: C eax src limb, carry subtracted
! 79: C ebx carry limb (0 or 1)
! 80: C ecx &src[size-1]
! 81: C edx scratch
! 82: C esi TWO_THIRDS_FLOOR
! 83: C edi &dst[size-1]
! 84: C ebp counter, limbs, negative
! 85:
! 86: imull $INVERSE_3, %eax, %edx
! 87:
! 88: movl 4(%ecx,%ebp,4), %eax C next src limb
! 89: cmpl $ONE_THIRD_CEIL, %edx
! 90:
! 91: sbbl $-1, %ebx C +1 if result>=ceil(b/3)
! 92: cmpl %edx, %esi
! 93:
! 94: sbbl %ebx, %eax C and further 1 if result>=ceil(b*2/3)
! 95: movl %edx, (%edi,%ebp,4)
! 96: incl %ebp
! 97:
! 98: setc %bl C new carry
! 99: jnz L(top)
! 100:
! 101:
! 102:
! 103: L(last):
! 104: C eax src limb, carry subtracted
! 105: C ebx carry limb (0 or 1)
! 106: C ecx &src[size-1]
! 107: C edx scratch
! 108: C esi multiplier
! 109: C edi &dst[size-1]
! 110: C ebp
! 111:
! 112: imull $INVERSE_3, %eax
! 113:
! 114: cmpl $ONE_THIRD_CEIL, %eax
! 115: movl %eax, (%edi)
! 116: movl SAVE_EBP, %ebp
! 117:
! 118: sbbl $-1, %ebx C +1 if eax>=ceil(b/3)
! 119: cmpl %eax, %esi
! 120: movl $0, %eax
! 121:
! 122: adcl %ebx, %eax C further +1 if eax>=ceil(b*2/3)
! 123: movl SAVE_EDI, %edi
! 124: movl SAVE_ESI, %esi
! 125:
! 126: movl SAVE_EBX, %ebx
! 127: addl $FRAME, %esp
! 128:
! 129: ret
! 130:
! 131: EPILOGUE()
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