[Spice-devel] [PATCH spice-gtk 4/4] canvas: use precomputed revers_bits

[Christophe Fergeau]

On Tue, Sep 10, 2013 at 04:43:39PM +0200, Marc-André Lureau wrote:
> From: Marc-André Lureau <marcandre.lureau at gmail.com>
> 
> Thos function shows up in some profiling results, it seems we can
> trivially replace it with a precomputed array of 256bytes.
> ---
>  common/canvas_base.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
> 
> diff --git a/common/canvas_base.c b/common/canvas_base.c
> index 38a8497..2753fae 100644
> --- a/common/canvas_base.c
> +++ b/common/canvas_base.c
> @@ -1329,6 +1329,8 @@ static pixman_image_t* canvas_get_image_from_self(SpiceCanvas *canvas,
>      return surface;
>  }
>  
> +
> +#ifdef REVERS_BITS_SLOW
>  static inline uint8_t revers_bits(uint8_t byte)
>  {
>      uint8_t ret = 0;
> @@ -1341,6 +1343,47 @@ static inline uint8_t revers_bits(uint8_t byte)
>      }
>      return ret;
>  }
> +#else
> +static inline uint8_t revers_bits(uint8_t byte)
> +{
> +    static const uint8_t revers[] = {
> +        0x0, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,
> +        0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
> +        0x8, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,
> +        0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
> +        0x4, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4,
> +        0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
> +        0xc, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec,
> +        0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
> +        0x2, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,
> +        0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
> +        0xa, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,
> +        0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
> +        0x6, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6,
> +        0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
> +        0xe, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,
> +        0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
> +        0x1, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1,
> +        0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
> +        0x9, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9,
> +        0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
> +        0x5, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,
> +        0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
> +        0xd, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed,
> +        0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
> +        0x3, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3,
> +        0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
> +        0xb, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,
> +        0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
> +        0x7, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7,
> +        0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
> +        0xf, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,
> +        0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff
> +    };

I'd tend to compute the table at startup rather than having the hardcoded
values in the source, just as you do for the golomb stuff.

Christophe

> +
> +    return revers[byte];
> +}
> +#endif
>  
>  static pixman_image_t *canvas_get_bitmap_mask(CanvasBase *canvas, SpiceBitmap* bitmap, int invers)
>  {
> -- 
> 1.8.3.1
> 
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