memset.s

来自「Glibc 2.3.2源代码(解压后有100多M)」· S 代码 · 共 45 行

/* Set a block of memory to some byte value.  For IBM S390
   Copyright (C) 2000, 2001 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Martin Schwidefsky ([e-mail]).

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

/*
 * R2 = address to memory area
 * R3 = byte to fill memory with
 * R4 = number of bytes to fill
 */

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

	.text
ENTRY(memset)
	ltr     %r4,%r4
	jz      .L1
	lr      %r0,%r2             # save source address
	lr      %r1,%r3             # move pad byte to R1
	lr      %r3,%r4
	sr      %r4,%r4             # no source for MVCLE, only a pad byte
	sr      %r5,%r5
.L0:    mvcle   %r2,%r4,0(%r1)      # thats it, MVCLE is your friend
	jo      .L0
	lr      %r2,%r0             # return value is source address
.L1:
	br      %r14
END(memset)