nir: Add nir_lower_image() to lower cube image sizes

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9466>

src/compiler/nir/meson.build

@@ -157,6 +157,7 @@ files_libnir = files(
   'nir_lower_load_const_to_scalar.c',
   'nir_lower_locals_to_regs.c',
   'nir_lower_idiv.c',
+  'nir_lower_image.c',
   'nir_lower_indirect_derefs.c',
   'nir_lower_input_attachments.c',
   'nir_lower_int64.c',

src/compiler/nir/nir.h

@@ -4935,6 +4935,16 @@ typedef struct nir_lower_tex_options {
 bool nir_lower_tex(nir_shader *shader,
                    const nir_lower_tex_options *options);
 
+typedef struct nir_lower_image_options {
+   /**
+    * If true, lower cube size operations.
+    */
+   bool lower_cube_size;
+} nir_lower_image_options;
+
+bool nir_lower_image(nir_shader *nir,
+                     const nir_lower_image_options *options);
+
 bool nir_lower_readonly_images_to_tex(nir_shader *shader, bool per_variable);
 
 enum nir_lower_non_uniform_access_type {

src/compiler/nir/nir_lower_image.c

@@ -0,0 +1,89 @@
+/*
+ * Copyright © 2021 Intel Corporation
+ *
+ * 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.
+ */
+
+/**
+ * This lowering pass supports (as configured via nir_lower_image_options)
+ * image related conversions:
+ *   + cube array size lowering. The size operation is converted from cube
+ *     size to a 2d-array with the z component divided by 6.
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+
+static void
+lower_cube_size(nir_builder *b, nir_intrinsic_instr *intrin)
+{
+   assert(nir_intrinsic_image_dim(intrin) == GLSL_SAMPLER_DIM_CUBE);
+
+   b->cursor = nir_before_instr(&intrin->instr);
+
+   nir_intrinsic_instr *_2darray_size =
+      nir_instr_as_intrinsic(nir_instr_clone(b->shader, &intrin->instr));
+   nir_intrinsic_set_image_dim(_2darray_size, GLSL_SAMPLER_DIM_2D);
+   nir_intrinsic_set_image_array(_2darray_size, true);
+   nir_builder_instr_insert(b, &_2darray_size->instr);
+
+   nir_ssa_def *size = nir_instr_ssa_def(&_2darray_size->instr);
+   nir_ssa_def *comps[NIR_MAX_VEC_COMPONENTS] = { NULL, };
+   unsigned coord_comps = intrin->dest.ssa.num_components;
+   for (unsigned c = 0; c < coord_comps; c++) {
+      if (c == 2) {
+         comps[2] = nir_idiv(b, nir_channel(b, size, 2), nir_imm_int(b, 6));
+      } else {
+         comps[c] = nir_channel(b, size, c);
+      }
+   }
+
+   nir_ssa_def *vec = nir_vec(b, comps, intrin->dest.ssa.num_components);
+   nir_ssa_def_rewrite_uses(&intrin->dest.ssa, vec);
+   nir_instr_remove(&intrin->instr);
+   ralloc_free(&intrin->instr);
+}
+
+static bool
+lower_image_instr(nir_builder *b, nir_instr *instr, void *state)
+{
+   if (instr->type != nir_instr_type_intrinsic)
+      return false;
+
+   const nir_lower_image_options *options = state;
+   nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+
+   if (options->lower_cube_size &&
+       intrin->intrinsic == nir_intrinsic_image_deref_size &&
+       nir_intrinsic_image_dim(intrin) == GLSL_SAMPLER_DIM_CUBE) {
+      lower_cube_size(b, intrin);
+      return true;
+   }
+
+   return false;
+}
+
+bool
+nir_lower_image(nir_shader *nir, const nir_lower_image_options *options)
+{
+   return nir_shader_instructions_pass(nir, lower_image_instr,
+                                       nir_metadata_block_index |
+                                       nir_metadata_dominance, (void*)options);
+}