From 6da06bf7d7fa8a6e108911fda0cc30a4c4e6348f Mon Sep 17 00:00:00 2001
From: Faith Ekstrand <faith.ekstrand@collabora.com>
Date: Thu, 21 Sep 2023 16:42:48 -0500
Subject: [PATCH] nak/nir: Return one sample for gl_SampleMaskIn[0] when sample
 shading

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24998>
---
 src/nouveau/compiler/nak_nir.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/nouveau/compiler/nak_nir.c b/src/nouveau/compiler/nak_nir.c
index 59c8f2e56d9..b8904161e11 100644
--- a/src/nouveau/compiler/nak_nir.c
+++ b/src/nouveau/compiler/nak_nir.c
@@ -422,6 +422,22 @@ lower_fs_input_intrin(nir_builder *b, nir_intrinsic_instr *intrin, void *data)
       return true;
    }
 
+   case nir_intrinsic_load_sample_mask_in: {
+      if (!b->shader->info.fs.uses_sample_shading &&
+          !(fs_key && fs_key->force_sample_shading))
+         return false;
+
+      b->cursor = nir_after_instr(&intrin->instr);
+
+      /* Mask off just the current sample */
+      nir_def *sample = nir_load_sample_id(b);
+      nir_def *mask = nir_ishl(b, nir_imm_int(b, 1), sample);
+      mask = nir_iand(b, &intrin->def, mask);
+      nir_def_rewrite_uses_after(&intrin->def, mask, mask->parent_instr);
+
+      return true;
+   }
+
    default:
       return false;
    }