Re: [PATCH] include/qemu: Use builtins for bswap

[Philippe Mathieu-Daudé]

On 7/8/21 8:17 PM, Richard Henderson wrote:
> All supported compilers have builtins for this.
> Drop all of the complicated system detection stuff.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  meson.build          |  6 -----
>  include/qemu/bswap.h | 53 +++-----------------------------------------
>  2 files changed, 3 insertions(+), 56 deletions(-)
> 
> diff --git a/meson.build b/meson.build
> index 7e12de01be..6024f2d6fb 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -1290,8 +1290,6 @@ config_host_data.set('HAVE_STRCHRNUL', 
> cc.has_function('strchrnul'))
>  config_host_data.set('HAVE_SYSTEM_FUNCTION', cc.has_function('system', 
> prefix: '#include <stdlib.h>'))
>  
>  # has_header_symbol
> -config_host_data.set('CONFIG_BYTESWAP_H',
> -                     cc.has_header_symbol('byteswap.h', 'bswap_32'))
>  config_host_data.set('CONFIG_EPOLL_CREATE1',
>                       cc.has_header_symbol('sys/epoll.h', 'epoll_create1'))
>  config_host_data.set('CONFIG_HAS_ENVIRON',
> @@ -1311,10 +1309,6 @@ config_host_data.set('CONFIG_INOTIFY',
>                       cc.has_header_symbol('sys/inotify.h', 'inotify_init'))
>  config_host_data.set('CONFIG_INOTIFY1',
>                       cc.has_header_symbol('sys/inotify.h', 'inotify_init1'))
> -config_host_data.set('CONFIG_MACHINE_BSWAP_H',
> -                     cc.has_header_symbol('machine/bswap.h', 'bswap32',
> -                                          prefix: '''#include <sys/endian.h>
> -                                                     #include 
> <sys/types.h>'''))
>  config_host_data.set('CONFIG_PRCTL_PR_SET_TIMERSLACK',
>                       cc.has_header_symbol('sys/prctl.h', 
> 'PR_SET_TIMERSLACK'))
>  config_host_data.set('CONFIG_RTNETLINK',
> diff --git a/include/qemu/bswap.h b/include/qemu/bswap.h
> index 2d3bb8bbed..9e12bd8073 100644
> --- a/include/qemu/bswap.h
> +++ b/include/qemu/bswap.h
> @@ -1,73 +1,26 @@
>  #ifndef BSWAP_H
>  #define BSWAP_H
>  
> -#ifdef CONFIG_MACHINE_BSWAP_H
> -# include <sys/endian.h>
> -# include <machine/bswap.h>
> -#elif defined(__FreeBSD__)
> -# include <sys/endian.h>
> -#elif defined(__HAIKU__)
> -# include <endian.h>
> -#elif defined(CONFIG_BYTESWAP_H)
> -# include <byteswap.h>
> -#define BSWAP_FROM_BYTESWAP
> -# else
> -#define BSWAP_FROM_FALLBACKS
> -#endif /* ! CONFIG_MACHINE_BSWAP_H */
> -
>  #ifdef __cplusplus
>  extern "C" {
>  #endif
>  
>  #include "fpu/softfloat-types.h"
>  
> -#ifdef BSWAP_FROM_BYTESWAP
>  static inline uint16_t bswap16(uint16_t x)
>  {
> -    return bswap_16(x);
> +    return __builtin_bswap16(x);
>  }
>  
>  static inline uint32_t bswap32(uint32_t x)
>  {
> -    return bswap_32(x);
> +    return __builtin_bswap32(x);
>  }
>  
>  static inline uint64_t bswap64(uint64_t x)
>  {
> -    return bswap_64(x);
> +    return __builtin_bswap64(x);
>  }
> -#endif
> -
> -#ifdef BSWAP_FROM_FALLBACKS
> -static inline uint16_t bswap16(uint16_t x)
> -{
> -    return (((x & 0x00ff) << 8) |
> -            ((x & 0xff00) >> 8));
> -}
> -
> -static inline uint32_t bswap32(uint32_t x)
> -{
> -    return (((x & 0x000000ffU) << 24) |
> -            ((x & 0x0000ff00U) <<  8) |
> -            ((x & 0x00ff0000U) >>  8) |
> -            ((x & 0xff000000U) >> 24));
> -}
> -
> -static inline uint64_t bswap64(uint64_t x)
> -{
> -    return (((x & 0x00000000000000ffULL) << 56) |
> -            ((x & 0x000000000000ff00ULL) << 40) |
> -            ((x & 0x0000000000ff0000ULL) << 24) |
> -            ((x & 0x00000000ff000000ULL) <<  8) |
> -            ((x & 0x000000ff00000000ULL) >>  8) |
> -            ((x & 0x0000ff0000000000ULL) >> 24) |
> -            ((x & 0x00ff000000000000ULL) >> 40) |
> -            ((x & 0xff00000000000000ULL) >> 56));
> -}
> -#endif
> -
> -#undef BSWAP_FROM_BYTESWAP
> -#undef BSWAP_FROM_FALLBACKS
>  
>  static inline void bswap16s(uint16_t *s)
>  {
> 

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>