diff options
Diffstat (limited to 'src/mesa/x86')
| -rw-r--r-- | src/mesa/x86/mmx_blend.S | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/src/mesa/x86/mmx_blend.S b/src/mesa/x86/mmx_blend.S index caf1f17ba4..8efae08f5e 100644 --- a/src/mesa/x86/mmx_blend.S +++ b/src/mesa/x86/mmx_blend.S @@ -39,7 +39,15 @@ * * achieving the exact results */ -#define GMBT_ROUNDOFF 1 +#define GMBT_ROUNDOFF 0 + +/* instead of the roundoff this adds a small correction to satisfy the OpenGL criteria + * + * t/255 ~= (t + (t >> 8) + (t >> 15)) >> 8 + * + * note that although is faster than rounding off it doesn't give always the exact results + */ +#define GMBT_GEOMETRIC_CORRECTION 1 /* * do @@ -282,6 +290,14 @@ LLBL (GMBT_loop_begin): PADDW ( MM3, MM2 ) /* t1 + (t1 >> 8) ~= (t1/255) << 8 */ PADDW ( MM5, MM6 ) /* t2 + (t2 >> 8) ~= (t2/255) << 8 */ + +#if GMBT_GEOMETRIC_CORRECTION + PSRLW ( CONST(7), MM3 ) /* t1 >> 15 */ + PSRLW ( CONST(7), MM5 ) /* t2 >> 15 */ + + PADDW ( MM3, MM2 ) /* t1 + (t1 >> 8) + (t1 >>15) ~= (t1/255) << 8 */ + PADDW ( MM5, MM6 ) /* t2 + (t2 >> 8) + (t2 >>15) ~= (t2/255) << 8 */ +#endif #endif #if GMBT_SIGNED_ARITHMETIC |