linker: Wrap access of producer_var with a NULL check

producer_var could be NULL if consumer_var is not NULL and
consumer_is_fs is false.  This will occur when the producer is NULL and
the consumer is the geometry shader for a program that contains only a
geometry shader.  This will occur starting with the next patch.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Cc: pavol@klacansky.com
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=82585
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
linker: Assign varying locations geometry shader inputs for SSO

Previously only geometry shader outputs would be assigned locations if
the geometry shader was the only stage in the linked program.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Cc: pavol@klacansky.com
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=82585
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
freedreno/a4xx: frag-depth fixes

Also seems to fix kill/discard.

Signed-off-by: Rob Clark <robclark@freedesktop.org>
i965/fs: Don't offset uniform registers in half().

Half gives you the second half of a SIMD16 register, but if the register
is a uniform it would incorrectly give you the next register.

Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
i965: Add var->location != -1 assertions.

We shouldn't receive variables with invalid locations set - adding these
assertions should help catch problems before they cause crashes later.

Inspired by similar code in st_glsl_to_tgsi.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>