2008-06-25 03:33:36 -04:00
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; Copyright 2000, 2001, 2002 Free Software Foundation, Inc.
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;
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; This file is part of the GNU MP Library.
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;
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; The GNU MP Library is free software; you can redistribute it and/or
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; modify it under the terms of the GNU Lesser General Public License as
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; published by the Free Software Foundation; either version 2.1 of the
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; License, or (at your option) any later version.
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;
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; The GNU MP Library 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 GNU
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; Lesser General Public License for more details.
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;
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; You should have received a copy of the GNU Lesser General Public
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; License along with the GNU MP Library; see the file COPYING.LIB. If
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; not, write to the Free Software Foundation, Inc., 59 Temple Place -
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; Suite 330, Boston, MA 02111-1307, USA.
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;
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; Translation of AT&T syntax code by Brian Gladman
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%include "x86i.inc"
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%define PARAM_CARRY esp+frame+16
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%define PARAM_SIZE esp+frame+12
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%define PARAM_SRC esp+frame+8
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%define PARAM_DST esp+frame+4
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%assign frame 0
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; multiplicative inverse of 3,modulo 2^32
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; ceil(b/3) and ceil(b*2/3) where b=2^32
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%define INVERSE_3 0xAAAAAAAB
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%define ONE_THIRD_CEIL 0x55555556
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%define TWO_THIRDS_CEIL 0xAAAAAAAB
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section .text
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global ___gmpn_divexact_by3c
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%ifdef DLL
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export ___gmpn_divexact_by3c
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%endif
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align 8
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___gmpn_divexact_by3c:
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mov ecx,[PARAM_SRC]
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FR_push ebp
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mov ebp,[PARAM_SIZE]
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FR_push edi
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mov edi,[PARAM_DST]
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FR_push esi
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mov esi,INVERSE_3
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FR_push ebx
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lea ecx,[ecx+ebp*4]
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mov ebx,[PARAM_CARRY]
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lea edi,[edi+ebp*4]
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neg ebp
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; eax scratch,low product
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; ebx carry limb (0 to 3)
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; ecx &src[size]
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; edx scratch,high product
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; esi multiplier
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; edi &dst[size]
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; ebp counter,limbs,negative
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align 8
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Ltop:
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mov eax,[ecx+ebp*4]
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sub eax,ebx
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setc bl
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imul esi
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cmp eax,ONE_THIRD_CEIL
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mov [edi+ebp*4],eax
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sbb ebx,-1 ; +1 if eax>=ceil(b/3)
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cmp eax,TWO_THIRDS_CEIL
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sbb ebx,-1 ; +1 if eax>=ceil(b*2/3)
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inc ebp
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jnz Ltop
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mov eax,ebx
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pop ebx
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pop esi
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pop edi
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pop ebp
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ret
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end
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