nir: remove dead glsl variables before lowering io.

For cull distance GLSL will let unsized unused arrays get
into the backend, we should nuke those straight away, to
save caring about them later.

This fixes:
arb_separate_shader_objects/linker/large-number-of-unused-varyings
as a side effect (even without culling changes).

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/src/mesa/drivers/dri/i965/brw_nir.c b/src/mesa/drivers/dri/i965/brw_nir.c
index 372b746453e6dac536d090530b76f983d6d47a36..9274f2e1616d6d240a8b327fed6907674a7bcbed 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_nir.c
+++ b/src/mesa/drivers/dri/i965/brw_nir.c
@@ -561,6 +561,7 @@ brw_create_nir(struct brw_context *brw,
    /* First, lower the GLSL IR or Mesa IR to NIR */
    if (shader_prog) {
       nir = glsl_to_nir(shader_prog, stage, options);
+      nir_remove_dead_variables(nir, nir_var_shader_in | nir_var_shader_out);
       OPT_V(nir_lower_io_to_temporaries,
             nir_shader_get_entrypoint(nir),
             true, false);