As we use a variable length the compiler does not realise that it is a fixed value of either 2 or 4 bytes. Instead of performing the inline comparison itself, the compiler inserts a function call to the generic memcmp routine which is optimised for long comparisons of variable length. That turns out to be quite expensive...
Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Dave Airlie airlied@redhat.com --- drivers/gpu/drm/udl/udl_transfer.c | 46 ++++++++++++++++++++++-------------- 1 file changed, 28 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/udl/udl_transfer.c b/drivers/gpu/drm/udl/udl_transfer.c index 142fee5..f343db7 100644 --- a/drivers/gpu/drm/udl/udl_transfer.c +++ b/drivers/gpu/drm/udl/udl_transfer.c @@ -75,15 +75,19 @@ static int udl_trim_hline(const u8 *bback, const u8 **bfront, int *width_bytes) } #endif
-static inline u16 pixel32_to_be16p(const uint8_t *pixel) +static inline u16 pixel32_to_be16(const uint32_t pixel) { - uint32_t pix = *(uint32_t *)pixel; - u16 retval; + return (((pixel >> 3) & 0x001f) | + ((pixel >> 5) & 0x07e0) | + ((pixel >> 8) & 0xf800)); +}
- retval = (((pix >> 3) & 0x001f) | - ((pix >> 5) & 0x07e0) | - ((pix >> 8) & 0xf800)); - return retval; +static bool pixel_repeats(const void *pixel, const uint32_t repeat, int bpp) +{ + if (bpp == 2) + return *(const uint16_t *)pixel == repeat; + else + return *(const uint32_t *)pixel == repeat; }
/* @@ -152,29 +156,33 @@ static void udl_compress_hline16( prefetch_range((void *) pixel, (cmd_pixel_end - pixel) * bpp);
while (pixel < cmd_pixel_end) { - const u8 * const repeating_pixel = pixel; - - if (bpp == 2) - *(uint16_t *)cmd = cpu_to_be16p((uint16_t *)pixel); - else if (bpp == 4) - *(uint16_t *)cmd = cpu_to_be16(pixel32_to_be16p(pixel)); + const u8 *const start = pixel; + u32 repeating_pixel; + + if (bpp == 2) { + repeating_pixel = *(uint16_t *)pixel; + *(uint16_t *)cmd = cpu_to_be16(repeating_pixel); + } else { + repeating_pixel = *(uint32_t *)pixel; + *(uint16_t *)cmd = cpu_to_be16(pixel32_to_be16(repeating_pixel)); + }
cmd += 2; pixel += bpp;
if (unlikely((pixel < cmd_pixel_end) && - (!memcmp(pixel, repeating_pixel, bpp)))) { + (pixel_repeats(pixel, repeating_pixel, bpp)))) { /* go back and fill in raw pixel count */ - *raw_pixels_count_byte = (((repeating_pixel - + *raw_pixels_count_byte = (((start - raw_pixel_start) / bpp) + 1) & 0xFF;
- while ((pixel < cmd_pixel_end) - && (!memcmp(pixel, repeating_pixel, bpp))) { + while ((pixel < cmd_pixel_end) && + (pixel_repeats(pixel, repeating_pixel, bpp))) { pixel += bpp; }
/* immediately after raw data is repeat byte */ - *cmd++ = (((pixel - repeating_pixel) / bpp) - 1) & 0xFF; + *cmd++ = (((pixel - start) / bpp) - 1) & 0xFF;
/* Then start another raw pixel span */ raw_pixel_start = pixel; @@ -223,6 +231,8 @@ int udl_render_hline(struct drm_device *dev, int bpp, struct urb **urb_ptr, u8 *cmd = *urb_buf_ptr; u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;
+ BUG_ON(!(bpp == 2 || bpp == 4)); + line_start = (u8 *) (front + byte_offset); next_pixel = line_start; line_end = next_pixel + byte_width;