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/******************************** -*- C -*- ****************************
*
* Fast versions of memset(s, 0, n)
*
*
***********************************************************************/
/***********************************************************************
*
* Copyright 2000, 2001, 2002, 2006 Free Software Foundation, Inc.
* Written by Paolo Bonzini. Inspired by the Linux source code.
*
* This file is part of GNU Smalltalk.
*
* GNU Smalltalk is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2, or (at your option) any later
* version.
*
* Linking GNU Smalltalk statically or dynamically with other modules is
* making a combined work based on GNU Smalltalk. Thus, the terms and
* conditions of the GNU General Public License cover the whole
* combination.
*
* In addition, as a special exception, the Free Software Foundation
* give you permission to combine GNU Smalltalk with free software
* programs or libraries that are released under the GNU LGPL and with
* independent programs running under the GNU Smalltalk virtual machine.
*
* You may copy and distribute such a system following the terms of the
* GNU GPL for GNU Smalltalk and the licenses of the other code
* concerned, provided that you include the source code of that other
* code when and as the GNU GPL requires distribution of source code.
*
* Note that people who make modified versions of GNU Smalltalk are not
* obligated to grant this special exception for their modified
* versions; it is their choice whether to do so. The GNU General
* Public License gives permission to release a modified version without
* this exception; this exception also makes it possible to release a
* modified version which carries forward this exception.
*
* GNU Smalltalk 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 General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* GNU Smalltalk; see the file COPYING. If not, write to the Free Software
* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*/
#ifndef GST_MEMZERO_H
#define GST_MEMZERO_H
#include "config.h"
/**************************************** not GCC ************************/
#ifndef __GNUC__
/* Fool the preprocessor and make it discard the following code */
#define GST_MEMZERO_DONE
#endif
/******************************************** GCC ************************/
/* GCC optimizes memset(s, 0, n) but not bzero(s, n).
The optimization is broken before EGCS 1.1. */
#if GNUC_PREREQ (2, 91)
#define memzero(s, n) __builtin_memset (s, '\0', n)
#define GST_MEMZERO_DONE
#endif
/**************************************** MIPS ***************************/
#if defined(__mips) || defined(mips)
#ifndef GST_MEMZERO_DONE
#define GST_MEMZERO_DONE
static inline void
memzero (PTR s,
size_t count)
{
if (!count)
return;
/* hmmm... this zeroes memory a byte at a time... I wonder whether it
is really faster than the generic version... */
__asm__ __volatile__ (".set noreorder" "\n"
"1: sb %3,(%0)" "\n"
" bne %0,%1,1b" "\n"
" addiu %0,%0,1" "\n"
" .set treorder":"=r" (s),
"=r" (count):"0" (s),
"r" (0L),
"1" (s + count - 1):"memory");
}
#endif
#endif
/**************************************** Intel x86 **********************/
#if defined(__i386__) || defined(__i386) || defined(i386)
#ifndef GST_MEMZERO_DONE
#define GST_MEMZERO_DONE
static inline void
memzero (PTR s,
size_t count)
{
int d0, d1;
__asm__ __volatile__ ("cld" "\n"
" rep ; stosl" "\n"
" testb $2,%b3" "\n"
" je 1f" "\n"
" stosw" "\n"
"1: testb $1,%b3" "\n"
" je 2f" "\n"
" stosb" "\n" "2:":"=&c" (d0),
"=&D" (d1):"a" (0L),
"q" (count),
"0" (count / 4),
"1" ((intptr_t) s):"memory");
}
#endif
#endif
/**************************************** Default implementation *********/
#if !defined(GST_MEMZERO_DONE) || !defined(__GNUC__)
/* cfr memmove.c -- both files implement a very fast unrolled loop, using
* approx. the same code (this has only destination, memmove has
* source+destination). */
#define COPY(type) *((type *) dst)++ = (type) 0;
/* This loop ensures that dst is aligned to a power of two
* bigger than sizeof(type)
*/
#define LOOP_ALIGN(type) \
while(n >= sizeof(type) && ((intptr_t) dst) & sizeof(type) ) { \
n -= sizeof(type); \
COPY(type); \
} \
/* This loop does as much as possible with the given type. */
#define LOOP_FINISH(type) \
while(n >= sizeof(type)) { \
n -= sizeof(type); \
COPY(type); \
} \
static inline void
memzero (PTR dst,
size_t n)
{
LOOP_ALIGN (char);
LOOP_ALIGN (short);
if (sizeof (long) > sizeof (int))
{
LOOP_ALIGN (int);
LOOP_FINISH (long);
}
LOOP_FINISH (int);
LOOP_FINISH (short);
LOOP_FINISH (char);
}
#undef LOOP_ALIGN
#undef LOOP_FINISH
#undef COPY
#endif
#undef GST_MEMZERO_DONE
#endif /* GST_MEMZERO_H */
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