Patch #5432 from Thomas Paul Diffenbach - small speedup for ipod video lcd_update function.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@10252 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 13 insertions, 6 deletions

diff --git a/firmware/drivers/lcd-ipodvideo.c b/firmware/drivers/lcd-ipodvideo.c
index 84b830377e..b94ab0b992 100644
--- a/firmware/drivers/lcd-ipodvideo.c
+++ b/firmware/drivers/lcd-ipodvideo.c
@@ -172,12 +172,19 @@ void lcd_update_rect(int x, int y, int width, int height)
         unsigned short *end = &src[LCD_WIDTH * height];
         int line_rem = (LCD_WIDTH - width);
         while (src < end) {
-            /* for each column */
-            unsigned short *end_line = src + width;
-            while (src < end_line) {
-                /* write out two pixels */
-                outw(*(src++), 0x30000000);
-                outw(*(src++), 0x30000000);
+            /* Duff's Device to unroll loop */
+            register int count = width ;
+            register int n=( count + 7 ) / 8;
+            switch( count % 8 ) {
+                case 0: do{ outw(*(src++), 0x30000000);
+                case 7:     outw(*(src++), 0x30000000);
+                case 6:     outw(*(src++), 0x30000000);
+                case 5:     outw(*(src++), 0x30000000);
+                case 4:     outw(*(src++), 0x30000000);
+                case 3:     outw(*(src++), 0x30000000);
+                case 2:     outw(*(src++), 0x30000000);
+                case 1:     outw(*(src++), 0x30000000);
+              } while(--n>0);
             }
             src += line_rem;
         }