intel/fs: make tcs input_vertices dynamic

We need to do 3 things to accomplish this :

   1. make all the register access consider the maximal case when
      unknown at compile time

   2. move the clamping of load_per_vertex_input prior to lowering
      nir_intrinsic_load_patch_vertices_in (in the dynamic cases, the
      clamping will use the nir_intrinsic_load_patch_vertices_in to
      clamp), meaning clamping using derefs rather than lowered
      nir_intrinsic_load_per_vertex_input

   3. in the known cases, lower nir_intrinsic_load_patch_vertices_in
      in NIR (so that the clamped elements still be vectorized to the
      smallest number of URB read messages)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22378>

src/intel/compiler/brw_fs_nir.cpp

@@ -2665,7 +2665,8 @@ fs_visitor::get_tcs_multi_patch_icp_handle(const fs_builder &bld,
     * we might read up to nir->info.gs.vertices_in registers.
     */
    bld.emit(SHADER_OPCODE_MOV_INDIRECT, icp_handle, start,
-            icp_offset_bytes, brw_imm_ud(tcs_key->input_vertices * REG_SIZE));
+            icp_offset_bytes,
+            brw_imm_ud(brw_tcs_prog_key_input_vertices(tcs_key) * REG_SIZE));
 
    return icp_handle;
 }
@@ -2675,7 +2676,6 @@ fs_visitor::nir_emit_tcs_intrinsic(const fs_builder &bld,
                                    nir_intrinsic_instr *instr)
 {
    assert(stage == MESA_SHADER_TESS_CTRL);
-   struct brw_tcs_prog_key *tcs_key = (struct brw_tcs_prog_key *) key;
    struct brw_tcs_prog_data *tcs_prog_data = brw_tcs_prog_data(prog_data);
    struct brw_vue_prog_data *vue_prog_data = &tcs_prog_data->base;
 
@@ -2690,10 +2690,6 @@ fs_visitor::nir_emit_tcs_intrinsic(const fs_builder &bld,
    case nir_intrinsic_load_invocation_id:
       bld.MOV(retype(dst, invocation_id.type), invocation_id);
       break;
-   case nir_intrinsic_load_patch_vertices_in:
-      bld.MOV(retype(dst, BRW_REGISTER_TYPE_D),
-              brw_imm_d(tcs_key->input_vertices));
-      break;
 
    case nir_intrinsic_scoped_barrier:
       if (nir_intrinsic_memory_scope(instr) != NIR_SCOPE_NONE)