数学计算

开发平台：
Unix_Linux

lshift.asm：源码内容
							dnl  Intel Pentium mpn_lshift -- mpn left shift.
dnl  Copyright 1992, 1994, 1995, 1996, 1999, 2000, 2002 Free Software
dnl  Foundation, Inc.
dnl
dnl  This file is part of the GNU MP Library.
dnl
dnl  The GNU MP Library is free software; you can redistribute it and/or
dnl  modify it under the terms of the GNU Lesser General Public License as
dnl  published by the Free Software Foundation; either version 3 of the
dnl  License, or (at your option) any later version.
dnl
dnl  The GNU MP Library is distributed in the hope that it will be useful,
dnl  but WITHOUT ANY WARRANTY; without even the implied warranty of
dnl  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
dnl  Lesser General Public License for more details.
dnl
dnl  You should have received a copy of the GNU Lesser General Public License
dnl  along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.
include(`../config.m4')
C         cycles/limb
C P5,P54:    6.0
C P55:       5.375
C mp_limb_t mpn_lshift (mp_ptr dst, mp_srcptr src, mp_size_t size,
C                       unsigned shift);
C
C The main shift-by-N loop should run at 5.375 c/l and that's what P55 does,
C but P5 and P54 run only at 6.0 c/l, which is 4 cycles lost somewhere.
defframe(PARAM_SHIFT,16)
defframe(PARAM_SIZE, 12)
defframe(PARAM_SRC,  8)
defframe(PARAM_DST,  4)
	TEXT
	ALIGN(8)
PROLOGUE(mpn_lshift)
	pushl	%edi
	pushl	%esi
	pushl	%ebx
	pushl	%ebp
deflit(`FRAME',16)
	movl	PARAM_DST,%edi
	movl	PARAM_SRC,%esi
	movl	PARAM_SIZE,%ebp
	movl	PARAM_SHIFT,%ecx
C We can use faster code for shift-by-1 under certain conditions.
	cmp	$1,%ecx
	jne	L(normal)
	leal	4(%esi),%eax
	cmpl	%edi,%eax
	jnc	L(special)		C jump if s_ptr + 1 >= res_ptr
	leal	(%esi,%ebp,4),%eax
	cmpl	%eax,%edi
	jnc	L(special)		C jump if res_ptr >= s_ptr + size
L(normal):
	leal	-4(%edi,%ebp,4),%edi
	leal	-4(%esi,%ebp,4),%esi
	movl	(%esi),%edx
	subl	$4,%esi
	xorl	%eax,%eax
	shldl(	%cl, %edx, %eax)	C compute carry limb
	pushl	%eax			C push carry limb onto stack
	decl	%ebp
	pushl	%ebp
	shrl	$3,%ebp
	jz	L(end)
	movl	(%edi),%eax		C fetch destination cache line
	ALIGN(4)
L(oop):	movl	-28(%edi),%eax		C fetch destination cache line
	movl	%edx,%ebx
	movl	(%esi),%eax
	movl	-4(%esi),%edx
	shldl(	%cl, %eax, %ebx)
	shldl(	%cl, %edx, %eax)
	movl	%ebx,(%edi)
	movl	%eax,-4(%edi)
	movl	-8(%esi),%ebx
	movl	-12(%esi),%eax
	shldl(	%cl, %ebx, %edx)
	shldl(	%cl, %eax, %ebx)
	movl	%edx,-8(%edi)
	movl	%ebx,-12(%edi)
	movl	-16(%esi),%edx
	movl	-20(%esi),%ebx
	shldl(	%cl, %edx, %eax)
	shldl(	%cl, %ebx, %edx)
	movl	%eax,-16(%edi)
	movl	%edx,-20(%edi)
	movl	-24(%esi),%eax
	movl	-28(%esi),%edx
	shldl(	%cl, %eax, %ebx)
	shldl(	%cl, %edx, %eax)
	movl	%ebx,-24(%edi)
	movl	%eax,-28(%edi)
	subl	$32,%esi
	subl	$32,%edi
	decl	%ebp
	jnz	L(oop)
L(end):	popl	%ebp
	andl	$7,%ebp
	jz	L(end2)
L(oop2):
	movl	(%esi),%eax
	shldl(	%cl,%eax,%edx)
	movl	%edx,(%edi)
	movl	%eax,%edx
	subl	$4,%esi
	subl	$4,%edi
	decl	%ebp
	jnz	L(oop2)
L(end2):
	shll	%cl,%edx		C compute least significant limb
	movl	%edx,(%edi)		C store it
	popl	%eax			C pop carry limb
	popl	%ebp
	popl	%ebx
	popl	%esi
	popl	%edi
	ret
C We loop from least significant end of the arrays, which is only
C permissable if the source and destination don't overlap, since the
C function is documented to work for overlapping source and destination.
L(special):
	movl	(%esi),%edx
	addl	$4,%esi
	decl	%ebp
	pushl	%ebp
	shrl	$3,%ebp
	addl	%edx,%edx
	incl	%ebp
	decl	%ebp
	jz	L(Lend)
	movl	(%edi),%eax		C fetch destination cache line
	ALIGN(4)
L(Loop):
	movl	28(%edi),%eax		C fetch destination cache line
	movl	%edx,%ebx
	movl	(%esi),%eax
	movl	4(%esi),%edx
	adcl	%eax,%eax
	movl	%ebx,(%edi)
	adcl	%edx,%edx
	movl	%eax,4(%edi)
	movl	8(%esi),%ebx
	movl	12(%esi),%eax
	adcl	%ebx,%ebx
	movl	%edx,8(%edi)
	adcl	%eax,%eax
	movl	%ebx,12(%edi)
	movl	16(%esi),%edx
	movl	20(%esi),%ebx
	adcl	%edx,%edx
	movl	%eax,16(%edi)
	adcl	%ebx,%ebx
	movl	%edx,20(%edi)
	movl	24(%esi),%eax
	movl	28(%esi),%edx
	adcl	%eax,%eax
	movl	%ebx,24(%edi)
	adcl	%edx,%edx
	movl	%eax,28(%edi)
	leal	32(%esi),%esi		C use leal not to clobber carry
	leal	32(%edi),%edi
	decl	%ebp
	jnz	L(Loop)
L(Lend):
	popl	%ebp
	sbbl	%eax,%eax		C save carry in %eax
	andl	$7,%ebp
	jz	L(Lend2)
	addl	%eax,%eax		C restore carry from eax
L(Loop2):
	movl	%edx,%ebx
	movl	(%esi),%edx
	adcl	%edx,%edx
	movl	%ebx,(%edi)
	leal	4(%esi),%esi		C use leal not to clobber carry
	leal	4(%edi),%edi
	decl	%ebp
	jnz	L(Loop2)
	jmp	L(L1)
L(Lend2):
	addl	%eax,%eax		C restore carry from eax
L(L1):	movl	%edx,(%edi)		C store last limb
	sbbl	%eax,%eax
	negl	%eax
	popl	%ebp
	popl	%ebx
	popl	%esi
	popl	%edi
	ret
EPILOGUE()

						