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 at chris-wilson.co.uk>
Cc: Dave Airlie <airlied at 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;
--
1.7.10.4
