i965: Select ranges of UBO data to be uploaded as push constants.

This adds a NIR pass that decides which portions of UBOS we should
upload as push constants, rather than pull constants.

v2: Switch to uint16_t for the UBO block number, because we may
    have a lot of them in Vulkan (suggested by Jason).  Add more
    comments about bitfield trickery (requested by Matt).

v3: Skip vec4 stages for now...I haven't finished wiring up support
    in the vec4 backend, and so pushing the data but not using it
    will just be wasteful.

Reviewed-by: Matt Turner <mattst88@gmail.com>

src/intel/compiler/brw_nir.h

@@ -142,6 +142,10 @@ void brw_nir_setup_glsl_uniforms(nir_shader *shader,
 void brw_nir_setup_arb_uniforms(nir_shader *shader, struct gl_program *prog,
                                 struct brw_stage_prog_data *stage_prog_data);
 
+void brw_nir_analyze_ubo_ranges(const struct brw_compiler *compiler,
+                                nir_shader *nir,
+                                struct brw_ubo_range out_ranges[4]);
+
 bool brw_nir_opt_peephole_ffma(nir_shader *shader);
 
 #define BRW_NIR_FRAG_OUTPUT_INDEX_SHIFT 0