[Mesa-dev] [PATCH] glsl: Fix gl_NormalMatrix swizzle setup to match i965's invariants.

[Eric Anholt]

On Wed, 19 Oct 2011 11:26:02 -0700, Paul Berry <stereotype441 at gmail.com> wrote:
Non-text part: multipart/alternative
> On 18 October 2011 17:33, Eric Anholt <eric at anholt.net> wrote:
> 
> > A driver trying to set up builtin uniforms is faced with a problem:
> > How do I walk the ir_variable structure (representing an array of
> > structs, or array of matrices, or struct, or whatever), and set up
> > driver structures so that dereference of that uniform gets the
> > corresponding ParameterValues[] entry.  The rule in general is that
> > each corresponding vector-sized field of an array of structs is one
> > builtin uniform state slot.  i965 relied on another invariant: each
> > state slot has a number of unique channel swizzles corresponding to
> > the number of elements in the field's vector, to avoid needing to walk
> > the glsl_type in parallel to get at vector_elements.
> >
> 
> Since only the i965 driver relies on this invariant, it would be easy for a
> mesa core developer to mess this up in the future and not notice.  Can we
> add an assertion to ir_variable.cpp's add_uniform() function to verify the
> invariant?  That would also serve as a nice place to document why the
> invariant is necessary.

That would require the same walking of the glsl_type that we're trying
to avoid in the driver.  Also, apparently idr's going to be rebuilding
how this is hooked up anyway, so that the driver doesn't care any more.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 197 bytes
Desc: not available
URL: <http://lists.freedesktop.org/archives/mesa-dev/attachments/20111020/15dd96da/attachment.pgp>