i965/fs: Handle non-const sample number in interpolateAtSample

If a non-const sample number is given to interpolateAtSample it will
now generate an indirect send message with the sample ID similar to
how non-const sampler array indexing works. Previously non-const
values were ignored and instead it ended up using a constant 0 value.

The generator will try to determine if the sample ID is dynamically
uniform via nir_src_is_dynamically_uniform. If not it will query the
pixel interpolator in a loop, once for each different live sample
number. The next live sample number is found using emit_uniformize. If
multiple live channels have the same sample number then they will be
handled in a single iteration of the loop. The loop is necessary
because the indirect send message doesn't seem to have a way to
specify a different value for each fragment.

This fixes the following two Piglit tests:

arb_gpu_shader5-interpolateAtSample-nonconst
arb_gpu_shader5-interpolateAtSample-dynamically-nonuniform

v2: Handle dynamically non-uniform sample ids.
v3: Remove the BREAK instruction and predicate the WHILE directly.
    Make the tokens arrays const. (Matt Turner)
v4: Iterate over the live channels instead of each possible sample
    number.
v5: Don't special case immediate values in
    brw_pixel_interpolator_query. Make a better wrapper for the
    function to set up the PI send instruction. Ensure that the SHL
    instructions are scalar. (Francisco Jerez).

Reviewed-by: Francisco Jerez <[email protected]>

1 files changed, 2 insertions, 3 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
index 6f8b75e339f..17e19cf807a 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
@@ -1377,15 +1377,14 @@ fs_generator::generate_pixel_interpolator_query(fs_inst *inst,
                                                 struct brw_reg msg_data,
                                                 unsigned msg_type)
 {
-   assert(msg_data.file == BRW_IMMEDIATE_VALUE &&
-          msg_data.type == BRW_REGISTER_TYPE_UD);
+   assert(msg_data.type == BRW_REGISTER_TYPE_UD);
 
    brw_pixel_interpolator_query(p,
          retype(dst, BRW_REGISTER_TYPE_UW),
          src,
          inst->pi_noperspective,
          msg_type,
-         msg_data.dw1.ud,
+         msg_data,
          inst->mlen,
          inst->regs_written);
 }