nir: Add nir_intrinsic_load_back_face_agx

On AGX, the special register for front facing is inverted from its meaning in
APIs. We need to lower load_front_face to inot(load_back_face). Doing this in
the backend is trivial, but then we would miss out on algebraic optimizations
for the inot.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Acked-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11199>

diff --git a/src/compiler/nir/nir_intrinsics.py b/src/compiler/nir/nir_intrinsics.py
index 072a366..18d24b9 100644 (file)
--- a/src/compiler/nir/nir_intrinsics.py
+++ b/src/compiler/nir/nir_intrinsics.py
@@ -1183,6 +1183,9 @@ store("tlb_sample_color_v3d", [1], [BASE, COMPONENT, SRC_TYPE], [])
 # the target framebuffer
 intrinsic("load_fb_layers_v3d", dest_comp=1, flags=[CAN_ELIMINATE, CAN_REORDER])
 
+# Logical complement of load_front_face, mapping to an AGX system value
+system_value("back_face_agx", 1, bit_sizes=[1, 32])
+
 # Intel-specific query for loading from the brw_image_param struct passed
 # into the shader as a uniform.  The variable is a deref to the image
 # variable. The const index specifies which of the six parameters to load.