[MPlayer-dev-eng] Re: ffmpeg byteswap
Bohdan Horst
nexus at irc.pl
Thu Nov 14 18:06:38 CET 2002
On Thu, Nov 14, 2002 at 01:58:14PM -0200, Mario Sergio Fujikawa Ferreira wrote:
> On Thu, Nov 14, 2002 at 12:48:09PM +0100, Bohdan Horst wrote:
> >
> > are there any performance differences between:
> >
> >
> > from original libavcodec/bswap.h:
> >
> > inline static unsigned short ByteSwap16(unsigned short x)
> > {
> > __asm("xchgb %b0,%h0" :
> > "=q" (x) :
> > "0" (x));
> > return x;
> > }
> >
> > inline static unsigned int ByteSwap32(unsigned int x)
> > {
> > #if __CPU__ > 386
> > __asm("bswap %0":
> > "=r" (x) :
> > #else
> > __asm("xchgb %b0,%h0\n"
> > " rorl $16,%0\n"
> > " xchgb %b0,%h0":
> > "=q" (x) :
> > #endif
> > "0" (x));
> > return x;
> > }
> >
> >
> > and from FreeBSD-STABLE native:
> >
> > sys/endian.h -> machine/endian.h ($FreeBSD: src/sys/i386/include/endian.h,v 1.18 1999/12/29 04:33:01 peter Exp $)
> >
> > #define __byte_swap_word(x) \
> > __extension__ ({ register u_short __X = (x); \
> > __asm ("xchgb %h1, %b1" \
> > : "=q" (__X) \
> > : "0" (__X)); \
> > __X; })
> >
> >
> > #if defined(_KERNEL) && (defined(I486_CPU) || defined(I586_CPU) || defined(I686_CPU)) && !defined(I386_CPU)
> > #define __byte_swap_long(x) \
> > __extension__ ({ register u_long __X = (x); \
> > __asm ("bswap %0" \
> > : "=r" (__X) \
> > : "0" (__X)); \
> > __X; })
> > #else
> > #define __byte_swap_long(x) \
> > __extension__ ({ register u_long __X = (x); \
> > __asm ("xchgb %h1, %b1\n\trorl $16, %1\n\txchgb %h1, %b1" \
> > : "=q" (__X) \
> > : "0" (__X)); \
> > __X; })
> > #endif
> >
> >
> > in my tests both works very very similar (i made some benchmarks)
>
> Actually, I am relying on "Steve O'Hara-Smith" <steve at sohara.org>
> and on freebsd-multimedia at FreeBSD.org for benchmark feedback.
> The optimized byteswap I'm using under FreeBSD is as follows
>
> ENTRY(ntohl)
> movl 4(%esp),%eax
> xchgb %al,%ah
> roll $16,%eax
> xchgb %al,%ah
> ret
>
> ENTRY(ntohs)
> movzwl 4(%esp),%eax
> xchgb %al,%ah
> ret
>
> #define be16toh(x) ntohs((x))
> #define be32toh(x) ntohl((x))
>
> #define bswap_16(x) (be16toh(x))
> #define bswap_32(x) (be32toh(x))
>
> Could you try against these? At "close" inspection
> they're ridiculously similar to ffmpeg code. I apologize
> but my i386 asm is rusty, almost dead. :(
> My desire to prefer the FreeBSD code was two-fold
>
> 1) Hope that the FreeBSD code would get better
> with increased versions but ffmpeg can cope with that ease
>
> 2) Hope to be cross platform since the macro
> points to an adequate byteswap for that platform (x86, ia64, alpha
> ...)
>
> Well, let me know what you're findings are.
can anyone take a short look at differences noticed above ?
my asm konwledge is about 0 :(
included:
freebsd ffmpeg byteswap patch: patch-libavcodec::bswap.h
freebsd include file: machine/endian.h
best regards
--
/ irl: Bohdan 'Nexus' Horst | irc: Nexus \
{----------------------v-------^---------------}
\ http://irc.pl/nexus | mailto: nexus at irc.pl /
-------------- next part --------------
--- libavcodec/bswap.h.orig Sun Nov 3 04:51:51 2002
+++ libavcodec/bswap.h Sun Nov 3 04:53:30 2002
@@ -5,6 +5,14 @@
#include <byteswap.h>
#else
+#if (defined(__unix__) || defined(unix)) && !defined(USG)
+#include <sys/param.h>
+#endif
+
+#if defined(__FreeBSD__) && __FreeBSD_version >= 470000
+#include <sys/endian.h>
+#endif
+
#ifdef ARCH_X86
inline static unsigned short ByteSwap16(unsigned short x)
{
@@ -13,7 +21,11 @@
"0" (x));
return x;
}
+#if defined(__FreeBSD__) && __FreeBSD_version >= 470000
+#define bswap_16(x) (be16toh(x))
+#else
#define bswap_16(x) ByteSwap16(x)
+#endif
inline static unsigned int ByteSwap32(unsigned int x)
{
@@ -29,7 +41,11 @@
"0" (x));
return x;
}
+#if defined(__FreeBSD__) && __FreeBSD_version >= 470000
+#define bswap_32(x) (be32toh(x))
+#else
#define bswap_32(x) ByteSwap32(x)
+#endif
inline static unsigned long long int ByteSwap64(unsigned long long int x)
{
-------------- next part --------------
/*
* Copyright (c) 1987, 1991 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* from: @(#)endian.h 7.8 (Berkeley) 4/3/91
* $FreeBSD: src/sys/i386/include/endian.h,v 1.18 1999/12/29 04:33:01 peter Exp $
*/
#ifndef _MACHINE_ENDIAN_H_
#define _MACHINE_ENDIAN_H_
/*
* Define the order of 32-bit words in 64-bit words.
*/
#define _QUAD_HIGHWORD 1
#define _QUAD_LOWWORD 0
#ifndef _POSIX_SOURCE
/*
* Definitions for byte order, according to byte significance from low
* address to high.
*/
#define LITTLE_ENDIAN 1234 /* LSB first: i386, vax */
#define BIG_ENDIAN 4321 /* MSB first: 68000, ibm, net */
#define PDP_ENDIAN 3412 /* LSB first in word, MSW first in long */
#define BYTE_ORDER LITTLE_ENDIAN
#ifndef _KERNEL
#include <sys/cdefs.h>
#endif
__BEGIN_DECLS
unsigned long htonl __P((unsigned long));
unsigned short htons __P((unsigned short));
unsigned long ntohl __P((unsigned long));
unsigned short ntohs __P((unsigned short));
__END_DECLS
#define __word_swap_long(x) \
__extension__ ({ register u_long __X = (x); \
__asm ("rorl $16, %1" \
: "=r" (__X) \
: "0" (__X)); \
__X; })
#if defined(_KERNEL) && (defined(I486_CPU) || defined(I586_CPU) || defined(I686_CPU)) && !defined(I386_CPU)
#define __byte_swap_long(x) \
__extension__ ({ register u_long __X = (x); \
__asm ("bswap %0" \
: "=r" (__X) \
: "0" (__X)); \
__X; })
#else
#define __byte_swap_long(x) \
__extension__ ({ register u_long __X = (x); \
__asm ("xchgb %h1, %b1\n\trorl $16, %1\n\txchgb %h1, %b1" \
: "=q" (__X) \
: "0" (__X)); \
__X; })
#endif
#define __byte_swap_word(x) \
__extension__ ({ register u_short __X = (x); \
__asm ("xchgb %h1, %b1" \
: "=q" (__X) \
: "0" (__X)); \
__X; })
/*
* Macros for network/external number representation conversion.
*/
#ifdef __GNUC__
#define ntohl __byte_swap_long
#define ntohs __byte_swap_word
#define htonl __byte_swap_long
#define htons __byte_swap_word
#endif
#define NTOHL(x) ((x) = ntohl((u_long)(x)))
#define NTOHS(x) ((x) = ntohs((u_short)(x)))
#define HTONL(x) ((x) = htonl((u_long)(x)))
#define HTONS(x) ((x) = htons((u_short)(x)))
#endif /* ! _POSIX_SOURCE */
#endif /* !_MACHINE_ENDIAN_H_ */
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