On 11.12.2014 01:08, Jason Ekstrand wrote: > > > On Tue, Dec 9, 2014 at 10:53 PM, Michel Dänzer <mic...@daenzer.net > <mailto:mic...@daenzer.net>> wrote: > > On 09.12.2014 21:06, Iago Toral Quiroga wrote: > > From: Jason Ekstrand <jason.ekstr...@intel.com > <mailto:jason.ekstr...@intel.com>> > > > > This patch fixes the return of a wrong value when x is lower than > > -MAX_INT(src_bits) as the result would not be between [-1.0 1.0]. > > > > v2 by Samuel Iglesias <sigles...@igalia.com > <mailto:sigles...@igalia.com>>: > > - Modify unorm_to_float() to avoid doing the division when > > x == -MAX_INT(src_bits) > > > > Reviewed-by: Ian Romanick <ian.d.roman...@intel.com > <mailto:ian.d.roman...@intel.com>> > > --- > > src/mesa/main/format_utils.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/src/mesa/main/format_utils.c b/src/mesa/main/format_utils.c > > index 93a0cea..5dd0848 100644 > > --- a/src/mesa/main/format_utils.c > > +++ b/src/mesa/main/format_utils.c > > @@ -152,7 +152,7 @@ unorm_to_float(unsigned x, unsigned src_bits) > > static inline float > > snorm_to_float(int x, unsigned src_bits) > > { > > - if (x == -MAX_INT(src_bits)) > > + if (x <= -MAX_INT(src_bits)) > > return -1.0f; > > else > > return x * (1.0f / (float)MAX_INT(src_bits)); > > > > The commit log talks about unorm_to_float, but the code modifies > snorm_to_float. Also, I think something like > > mesa: Fix clamping to -1.0 in snorm_to_float > > would be a more useful shortlog. > > > BTW, don't this function and unorm_to_float also need corresponding > clamping to 1.0 for values >= MAX_INT(src_bits)? > > > Yes and no. Every place that we use [us]norm_to_*, we assume that the > value passed in is represented by the given number of bits. Therefore, > clamping above should always be useless. The one edge case is the > signed value MIN_INT(src_bits) (or, if you prefer, -MAX_INT(src_bits) - > 1) in which is representable in the given number of bits but is actually > less than -1 according to the formula. Technically, using an equality > there was Ok, it's just that I had it equal to the wrong thing.
So, is returning -1.0 for -MAX_INT(src_bits) correct then, or should the test be '== MIN_INT(src_bits)' or '== -MAX_INT(src_bits) - 1' or either variant using <=? -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
