Use fast path for RGB 565 -> 32-bit XRGB 8888

Hello Sam, while profiling ScummVM I noticed it was making use of the generic BlitNToN blitter, which struck me as odd because it should be a very classical codepath. After investigating, I saw that in the blit op chooser: { 0x0000F800,0x000007E0,0x0000001F, 4, 0x00FF0000,0x0000FF00,0x000000FF, 0, NULL, Blit_RGB565_ARGB8888, SET_ALPHA }, { 0x0000F800,0x000007E0,0x0000001F, 4, 0x000000FF,0x0000FF00,0x00FF0000, 0, NULL, Blit_RGB565_ABGR8888, SET_ALPHA }, { 0x0000F800,0x000007E0,0x0000001F, 4, 0xFF000000,0x00FF0000,0x0000FF00, 0, NULL, Blit_RGB565_RGBA8888, SET_ALPHA }, { 0x0000F800,0x000007E0,0x0000001F, 4, 0x0000FF00,0x00FF0000,0xFF000000, 0, NULL, Blit_RGB565_BGRA8888, SET_ALPHA }, Couldn't the optimized versions be used for NO_ALPHA too? I take it that the resulting alpha component can be undefined as it should never be used. I tried this (see attached patch) and it worked perfectly (and therefore faster) on ScummVM but there might be a trick (I'm not expert at the semantics of SDL, ie NO_ALPHA, SET_ALPHA and COPY_ALPHA there). What do you think? Cheers, Bertrand
libsdl-org · Sep 2, 2012 · 6f4a75d · 6f4a75d
1 parent 79f5116
commit 6f4a75d
Showing 1 changed file with 4 additions and 4 deletions.
diff --git a/src/video/SDL_blit_N.c b/src/video/SDL_blit_N.c
@@ -2307,13 +2307,13 @@ static const struct blit_table normal_blit_2[] = {
       2, NULL, Blit_RGB555_32Altivec, NO_ALPHA | COPY_ALPHA | SET_ALPHA },
 #endif
     { 0x0000F800,0x000007E0,0x0000001F, 4, 0x00FF0000,0x0000FF00,0x000000FF,
-      0, NULL, Blit_RGB565_ARGB8888, SET_ALPHA },
+      0, NULL, Blit_RGB565_ARGB8888, NO_ALPHA | COPY_ALPHA | SET_ALPHA },
     { 0x0000F800,0x000007E0,0x0000001F, 4, 0x000000FF,0x0000FF00,0x00FF0000,
-      0, NULL, Blit_RGB565_ABGR8888, SET_ALPHA },
+      0, NULL, Blit_RGB565_ABGR8888, NO_ALPHA | COPY_ALPHA | SET_ALPHA },
     { 0x0000F800,0x000007E0,0x0000001F, 4, 0xFF000000,0x00FF0000,0x0000FF00,
-      0, NULL, Blit_RGB565_RGBA8888, SET_ALPHA },
+      0, NULL, Blit_RGB565_RGBA8888, NO_ALPHA | COPY_ALPHA | SET_ALPHA },
     { 0x0000F800,0x000007E0,0x0000001F, 4, 0x0000FF00,0x00FF0000,0xFF000000,
-      0, NULL, Blit_RGB565_BGRA8888, SET_ALPHA },
+      0, NULL, Blit_RGB565_BGRA8888, NO_ALPHA | COPY_ALPHA | SET_ALPHA },
 
     /* Default for 16-bit RGB source, used if no other blitter matches */
     { 0,0,0, 0, 0,0,0, 0, NULL, BlitNtoN, 0 }