copyd.asm

来自「最优秀的大数计算源码,适合各种大数的计算,底层对各种机器进行汇编优化,速度最快」· 汇编 代码 · 共 65 行

dnl  Pentium-4 mpn_copyd -- copy limb vector, decrementing.
dnl

dnl  Copyright 1999, 2000, 2001 Free Software 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 2.1 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
dnl  License along with the GNU MP Library; see the file COPYING.LIB.  If
dnl  not, write to the Free Software Foundation, Inc., 59 Temple Place -
dnl  Suite 330, Boston, MA 02111-1307, USA.


dnl  The std/rep/movsl/cld is very slow for small blocks on pentium4.  Its
dnl  startup time seems to be about 165 cycles.  It then copies at a rate of
dnl  one limb per cycle.  We therefore fall back to an open-coded 2 c/l
dnl  copying loop for smaller sizes.

dnl  Ultimately, we may want to use 64-bit movq or 128-bit movdqu in some
dnl  nifty unrolled arrangement.  Clearly, that could reach much higher
dnl  speeds, at least for large blocks.

include(`../config.m4')


defframe(PARAM_SIZE, 12)
defframe(PARAM_SRC, 8)
defframe(PARAM_DST,  4)

	TEXT
	ALIGN(8)

PROLOGUE(mpn_copyd)
deflit(`FRAME',0)

	movl	PARAM_SIZE, %ecx

	movl	PARAM_SRC, %eax
	movl	PARAM_DST, %edx
	movl	%ebx, PARAM_SIZE
	addl	$-1, %ecx
	js	L(end)

L(loop):
	movl	(%eax,%ecx,4), %ebx
	movl	%ebx, (%edx,%ecx,4)
	addl	$-1, %ecx

	jns	L(loop)
L(end):
	movl	PARAM_SIZE, %ebx
	ret

EPILOGUE()