On Thu, 2015-01-08 at 13:54 +0200, Aras Pranckevicius wrote: > I see precision qualifiers being parsed and stored in the AST, > but I > don't see where this information is passed to the IR: > ir_variable or > glsl_type don't have this info, in fact, > apply_type_qualifier_to_variable() in ast_to_hir.cpp seems to > ignore the > ast precision qualifier data completely. > > > Correct, precision is blissfully ignored in Mesa IR. > > > > So I am guessing that we should add precision information to > the > glsl_type, but I wonder if there is a reason why this hasn't > been done > yet > > > I did add precision support for glsl-optimizer > (https://github.com/aras-p/glsl-optimizer) which is a fork of Mesa. > > > I forgot why I did not make precision be part of the type to be > honest, but I think there was some reason. Maybe because a ton of > places in Mesa do things like "get me a float type", and changing all > these places to deal with 4x more types (unspecified, low, medium, > high) did not sound attactive. > > > So what I did is ir make ir_rvalues and ir_variables have precision > (and a few other oddball things, like return type of > ir_function_signature). And then in places that construct rvalues or > variables, the precision is determined. In some cases that comes > directly from AST, in other cases (e.g. results of optimization > passes) it comes from "higher precision of things being operated > upon" (e.g. result of a+b is higher precision of the arguments), etc. > > > And then I tweaked some optimization passes to stop applying > optimizations across different precision. For example, tree grafting > should not paste subtrees into other places, if precision is different > there. > > > Not sure if my approach (precision as not part of type, but rvalues > +variables) is a good one, but seems to work so far in glsl-optimizer.
Hi Aras, thanks for the input. For now I am not really trying to fully incorporate precision qualifiers into the IR, what I am trying to do is to get enough info in the IR so I can do compile and link time checks for variable definitions, so I am not going down to the level of ir_rvalue for example. I think that part can be added later, once we decide to put precision qualifiers into actual use in Mesa. BTW, in the end I did not add the precision info to glsl_type, I am also adding this in ir_variable. That approach complicated things more than necessary and there are also various mentions in the spec that state that precision qualifiers do change a variable's type, so that approach seemed less consistent with the spirit of the spec too. Iago _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
