[Mesa-dev] tgsi dump and parsing

[Jose Fonseca]

Yes, if we change the representation, we should keep backwards compatability in tgsi text parsing 

Jose

----- Original Message -----
> There are some TGSI shaders parsed by tgsi_text_translate which
> declare floating-point immediates. Any incompatible change to the
> parser would break them.
> 
> Marek
> 
> On Wed, Aug 28, 2013 at 3:57 PM, Jose Fonseca <jfonseca at vmware.com> wrote:
> > ----- Original Message -----
> >> On Wed, Aug 28, 2013 at 3:32 PM, Dave Airlie <airlied at gmail.com> wrote:
> >> >>> IMM[0] FLT32 { 0x...., 0x...., 0x...., 0x.... }  # 1.0, 3.0, 2.0, 4.0
> >> >>
> >> >> If you use "%.9g" instead of "%.4f" then floating point numbers will be
> >> >> preserved without loss of precision.
> >> >>
> >> >
> >> > I see a -nan in my tests that doesn't get reparsed so I expect hex is
> >> > still better.
> >> >
> >> >
> >> > oops to list as well this time, sorry.
> >>
> >> Just in case you are wondering its
> >> tests/shaders/glsl-const-builtin-inversesqrt.shader_test and
> >> tests/shaders/glsl-const-builtin-normalize.shader_test
> >> that throw up the -nan in the dumps.
> >
> > We could teach tgsi_parse to understand `nan` too.
> >
> > We could also have a new tgsi_compare() function that, instead of doing a
> > bare memcmp, it would scan the tokens, and account for the ambiguity of
> > NaNs in IMM FLT32.
> >
> >
> > I just feel a bit awkward that we have `IMM[x] INT32 {...}` and `IMM[x]
> > FLT32 {...}` but end up dumping floats as integers. The whole point of
> > INT32/FLT32 is to allow humans to read the numbers, because it is just
> > syntactic sugar: by definition a shader must behave precisely the same way
> > regardless the IMMS have INT32 or FLT32, as in TGSI the type is not
> > defined by the arguments but rather the opcodes.
> >
> > Also, editing IMM FLT32 by hand will be much harder -- you'll need to
> > convert floats their integer repreentation, as the floats in the comment
> > will likely be ignored..
> >
> >
> > To me, it seems that would be trading off a concrete advantage -- the
> > usability of the TGSI textual representation --, for this much more
> > dubious advantage of perfect bit-by-bit reversibility of TGSI
> > binary<->text shaders.
> >
> >
> > That said, I don't feel strongly either way.
> >
> >
> > Jose
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>