ac/llvm: get back nir_intrinsic_load_gs_vertex_offset_amd

Will be used by radeonsi.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16788>

src/amd/llvm/ac_nir_to_llvm.c

@@ -4033,6 +4033,9 @@ static void visit_intrinsic(struct ac_nir_context *ctx, nir_intrinsic_instr *ins
       result = ac_build_gather_values(&ctx->ac, coord, 3);
       break;
    }
+   case nir_intrinsic_load_gs_vertex_offset_amd:
+      result = ac_get_arg(&ctx->ac, ctx->args->gs_vtx_offset[nir_intrinsic_base(instr)]);
+      break;
    case nir_intrinsic_vote_all: {
       result = ac_build_vote_all(&ctx->ac, get_src(ctx, instr->src[0]));
       break;