panfrost: add lowering pass for multisampled images

Panfrost generally treats 2D multisampled images like 3D images,
with the R coordinate holding the sample index. This commit adds
a lowering pass to convert 2DMS images to 3D for the compiler. It
is not actually invoked yet.

Signed-off-by: Eric R. Smith <eric.smith@collabora.com>
Reviewed-by:   Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27626>

src/panfrost/util/meson.build

@@ -28,6 +28,7 @@ libpanfrost_util_files = files(
   'pan_liveness.c',
   'pan_lower_framebuffer.c',
   'pan_lower_helper_invocation.c',
+  'pan_lower_image_ms.c',
   'pan_lower_sample_position.c',
   'pan_lower_store_component.c',
   'pan_lower_writeout.c',

src/panfrost/util/pan_ir.h

@@ -399,6 +399,7 @@ void pan_print_alu_type(nir_alu_type t, FILE *fp);
 bool pan_nir_lower_zs_store(nir_shader *nir);
 bool pan_nir_lower_store_component(nir_shader *shader);
 
+bool pan_nir_lower_image_ms(nir_shader *shader);
 bool pan_nir_lower_64bit_intrin(nir_shader *shader);
 
 bool pan_lower_helper_invocation(nir_shader *shader);

src/panfrost/util/pan_lower_image_ms.c

@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2024 Collabora, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Authors (Collabora):
+ *   Eric Smith <eric.smith@collabora.com>
+ */
+
+#include "compiler/nir/nir.h"
+#include "compiler/nir/nir_builder.h"
+#include "pan_ir.h"
+
+static bool
+nir_lower_image_ms(nir_builder *b, nir_intrinsic_instr *intr,
+                        UNUSED void *data)
+{
+   switch (intr->intrinsic) {
+   case nir_intrinsic_image_load:
+   case nir_intrinsic_image_deref_load:
+   case nir_intrinsic_image_store:
+   case nir_intrinsic_image_deref_store:
+   case nir_intrinsic_image_texel_address:
+      break;
+   default:
+      return false;
+   }
+
+   if (nir_intrinsic_image_dim(intr) != GLSL_SAMPLER_DIM_MS)
+      return false;
+
+   b->cursor = nir_before_instr(&intr->instr);
+
+   nir_def *coord = intr->src[1].ssa;
+   nir_def *index = intr->src[2].ssa;
+
+   /* image2DMS is treated by panfrost as if it were a 3D image, so
+    * the sample index is in src[2]. We need to put this into the coordinates
+    * in the Z component
+    */
+   nir_src_rewrite(&intr->src[1],
+                   nir_vector_insert_imm(b, coord,
+                                         nir_channel(b, index, 0),
+                                         2) );
+   nir_intrinsic_set_image_dim(intr, GLSL_SAMPLER_DIM_3D);
+   return true;
+}
+
+bool
+pan_nir_lower_image_ms(nir_shader *shader)
+{
+   return nir_shader_intrinsics_pass(
+      shader, nir_lower_image_ms,
+      nir_metadata_block_index | nir_metadata_dominance, NULL);
+}