lshift.s

一个C源代码分析器

# i80386 __mpn_lshift -- 

# Copyright (C) 1992, 1994 Free Software Foundation, Inc.

# This file is part of the GNU MP Library.

# The GNU MP Library is free software; you can redistribute it and/or modify
# it under the terms of the GNU Library General Public License as published by
# the Free Software Foundation; either version 2 of the License, or (at your
# option) any later version.

# The GNU MP Library is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
# License for more details.

# You should have received a copy of the GNU Library General Public License
# along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
# the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.


# INPUT PARAMETERS
# res_ptr	(sp + 4)
# s_ptr		(sp + 8)
# size		(sp + 12)
# cnt		(sp + 16)

#include "sysdep.h"
#include "asm-syntax.h"

.text
	.align 2
	.globl C_SYMBOL_NAME(__mpn_lshift)
C_SYMBOL_NAME(__mpn_lshift):
	pushl	%edi
	pushl	%esi
	pushl	%ebx

	movl	16(%esp),%edi	# res_ptr
	movl	20(%esp),%esi	# s_ptr
	movl	24(%esp),%edx	# size
	movl	28(%esp),%ecx	# cnt

	subl	$4,%esi			# adjust s_ptr

	movl	(%esi,%edx,4),%ebx	# read most significant limb
	xorl	%eax,%eax
	shldl	%cl,%ebx,%eax		# compute carry limb
	decl	%edx
	jz	Lend
	pushl	%eax			# push carry limb onto stack
	testb	$1,%edx
	jnz	L1			# enter loop in the middle
	movl	%ebx,%eax

	.align	2,0x90
Loop:	movl	(%esi,%edx,4),%ebx	# load next lower limb
	shldl	%cl,%ebx,%eax		# compute result limb
	movl	%eax,(%edi,%edx,4)	# store it
	decl	%edx
L1:	movl	(%esi,%edx,4),%eax
	shldl	%cl,%eax,%ebx
	movl	%ebx,(%edi,%edx,4)
	decl	%edx
	jnz	Loop

	shll	%cl,%eax		# compute least significant limb
	movl	%eax,(%edi)		# store it

	popl	%eax			# pop carry limb

	popl	%ebx
	popl	%esi
	popl	%edi
	ret

Lend:	shll	%cl,%ebx		# compute least significant limb
	movl	%ebx,(%edi)		# store it

	popl	%ebx
	popl	%esi
	popl	%edi
	ret