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 · fa92345 · fa92345
1 parent 9894b5b
commit fa92345
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
@@ -2360,16 +2360,16 @@ static const struct blit_table normal_blit_2[] = {
 #endif
     {0x0000F800, 0x000007E0, 0x0000001F, 4, 0x00FF0000, 0x0000FF00,
      0x000000FF,
-     0, Blit_RGB565_ARGB8888, SET_ALPHA},
+     0, Blit_RGB565_ARGB8888, NO_ALPHA | COPY_ALPHA | SET_ALPHA},
     {0x0000F800, 0x000007E0, 0x0000001F, 4, 0x000000FF, 0x0000FF00,
      0x00FF0000,
-     0, Blit_RGB565_ABGR8888, SET_ALPHA},
+     0, Blit_RGB565_ABGR8888, NO_ALPHA | COPY_ALPHA | SET_ALPHA},
     {0x0000F800, 0x000007E0, 0x0000001F, 4, 0xFF000000, 0x00FF0000,
      0x0000FF00,
-     0, Blit_RGB565_RGBA8888, SET_ALPHA},
+     0, Blit_RGB565_RGBA8888, NO_ALPHA | COPY_ALPHA | SET_ALPHA},
     {0x0000F800, 0x000007E0, 0x0000001F, 4, 0x0000FF00, 0x00FF0000,
      0xFF000000,
-     0, Blit_RGB565_BGRA8888, SET_ALPHA},
+     0, 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, BlitNtoN, 0}