nir: Move vc4's alpha test lowering to core NIR.

I've been doing this inside of vc4, but vc5 wants it as well and it may be
useful for other drivers (Intel has a related path for pre-gen6 with MRT,
and freedreno had a TGSI path for it at one point).

This required defining a common enum for the standard comparison
functions, but other lowering passes are likely to also want that enum.

v2: Add to meson.build as well.

Acked-by: Rob Clark <[email protected]>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index bb5aba605a1..5af150310f2 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2447,6 +2447,8 @@ bool nir_lower_constant_initializers(nir_shader *shader,
 
 bool nir_move_vec_src_uses_to_dest(nir_shader *shader);
 bool nir_lower_vec_to_movs(nir_shader *shader);
+void nir_lower_alpha_test(nir_shader *shader, enum compare_func func,
+                          bool alpha_to_one);
 bool nir_lower_alu_to_scalar(nir_shader *shader);
 bool nir_lower_load_const_to_scalar(nir_shader *shader);
 bool nir_lower_read_invocation_to_scalar(nir_shader *shader);