Re: [PATCH 3/4] qemu/bswap: Add const_le64() and const_be64()

[Richard Henderson <richard.henderson@linaro.org>]

On 9/17/20 9:31 AM, Philippe Mathieu-Daudé wrote:
> From: Philippe Mathieu-Daudé <f4bug@amsat.org>
> 
> We already have the const_endian() macros for 16-bit and
> 32-bit values. Implement the 64-bit equivalent macros.
> 
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  include/qemu/bswap.h | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/include/qemu/bswap.h b/include/qemu/bswap.h
> index 6885984e00c..de256cea3ab 100644
> --- a/include/qemu/bswap.h
> +++ b/include/qemu/bswap.h
> @@ -83,11 +83,20 @@ static inline void bswap64s(uint64_t *s)
>  #endif
>  
>  /*
> - * Same as cpu_to_{be,le}{16,32} described below, except that gcc will
> + * Same as cpu_to_{be,le}{16,32,64} described below, except that gcc will
>   * figure the result is a compile-time constant if you pass in a constant.
>   * So this can be used to initialize static variables.
>   */
>  #if defined(HOST_WORDS_BIGENDIAN)
> +# define const_le64(_x)                          \
> +    ((((_x) & 0x00000000000000ffU) << 56) |      \
> +     (((_x) & 0x000000000000ff00U) << 40) |      \
> +     (((_x) & 0x0000000000ff0000U) << 24) |      \
> +     (((_x) & 0x00000000ff000000U) <<  8) |      \
> +     (((_x) & 0x000000ff00000000U) >>  8) |      \
> +     (((_x) & 0x0000ff0000000000U) >> 24) |      \
> +     (((_x) & 0x00ff000000000000U) >> 40) |      \
> +     (((_x) & 0xff00000000000000U) >> 56))
>  # define const_le32(_x)                          \
>      ((((_x) & 0x000000ffU) << 24) |              \
>       (((_x) & 0x0000ff00U) <<  8) |              \
> @@ -96,11 +105,22 @@ static inline void bswap64s(uint64_t *s)
>  # define const_le16(_x)                          \
>      ((((_x) & 0x00ff) << 8) |                    \
>       (((_x) & 0xff00) >> 8))
> +# define const_be64(_x) (_x)
>  # define const_be32(_x) (_x)
>  # define const_be16(_x) (_x)
>  #else
> +# define const_le64(_x) (_x)
>  # define const_le32(_x) (_x)
>  # define const_le16(_x) (_x)
> +# define const_be64(_x)                          \
> +    ((((_x) & 0x00000000000000ffU) << 56) |      \
> +     (((_x) & 0x000000000000ff00U) << 40) |      \
> +     (((_x) & 0x0000000000ff0000U) << 24) |      \
> +     (((_x) & 0x00000000ff000000U) <<  8) |      \
> +     (((_x) & 0x000000ff00000000U) >>  8) |      \
> +     (((_x) & 0x0000ff0000000000U) >> 24) |      \
> +     (((_x) & 0x00ff000000000000U) >> 40) |      \
> +     (((_x) & 0xff00000000000000U) >> 56))
>  # define const_be32(_x)                          \
>      ((((_x) & 0x000000ffU) << 24) |              \
>       (((_x) & 0x0000ff00U) <<  8) |              \
> 

This duplication suggests that we define these as const_bswap64, and define
const_le64/be64 on top of that.  Similar for the other defines as you're moving
them.


r~