nir: add a pass to compact clip/cull distances.

v2: Use nir_is_per_vertex_io() rather than is_arrays_of_arrays().

Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]>

3 files changed, 190 insertions, 0 deletions

diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources
index d05bcacb9c5..6a7dcd847db 100644
--- a/src/compiler/Makefile.sources
+++ b/src/compiler/Makefile.sources
@@ -198,6 +198,7 @@ NIR_FILES = \
 	nir/nir_lower_bitmap.c \
 	nir/nir_lower_clamp_color_outputs.c \
 	nir/nir_lower_clip.c \
+	nir/nir_lower_clip_cull_distance_arrays.c \
 	nir/nir_lower_double_ops.c \
 	nir/nir_lower_double_packing.c \
 	nir/nir_lower_drawpixels.c \
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 68d62d98d86..3e6d168e974 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2441,6 +2441,7 @@ bool nir_lower_idiv(nir_shader *shader);
 
 void nir_lower_clip_vs(nir_shader *shader, unsigned ucp_enables);
 void nir_lower_clip_fs(nir_shader *shader, unsigned ucp_enables);
+void nir_lower_clip_cull_distance_arrays(nir_shader *nir);
 
 void nir_lower_two_sided_color(nir_shader *shader);
 
diff --git a/src/compiler/nir/nir_lower_clip_cull_distance_arrays.c b/src/compiler/nir/nir_lower_clip_cull_distance_arrays.c
new file mode 100644
index 00000000000..5a89eddc271
--- /dev/null
+++ b/src/compiler/nir/nir_lower_clip_cull_distance_arrays.c
@@ -0,0 +1,188 @@
+/*
+ * Copyright © 2015 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.
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+
+/**
+ * @file
+ *
+ * This pass combines separate clip and cull distance arrays into a
+ * single array that contains both.  Clip distances come first, then
+ * cull distances.  It also populates nir_shader_info with the size
+ * of the original arrays so the driver knows which are which.
+ */
+
+/**
+ * Get the length of the clip/cull distance array, looking past
+ * any interface block arrays.
+ */
+static unsigned
+get_unwrapped_array_length(nir_shader *nir, nir_variable *var)
+{
+   if (!var)
+      return 0;
+
+   /* Unwrap GS input and TCS input/output interfaces.  We want the
+    * underlying clip/cull distance array length, not the per-vertex
+    * array length.
+    */
+   const struct glsl_type *type = var->type;
+   if (nir_is_per_vertex_io(var, nir->stage))
+      type = glsl_get_array_element(type);
+
+   assert(glsl_type_is_array(type));
+
+   return glsl_get_length(type);
+}
+
+/**
+ * Update the type of the combined array (including interface block nesting).
+ */
+static void
+update_type(nir_variable *var, gl_shader_stage stage, unsigned length)
+{
+   const struct glsl_type *type = glsl_array_type(glsl_float_type(), length);
+
+   if (nir_is_per_vertex_io(var, stage))
+      type = glsl_array_type(type, glsl_get_length(var->type));
+
+   var->type = type;
+}
+
+/**
+ * Rewrite any clip/cull distances to refer to the new combined array.
+ */
+static void
+rewrite_references(nir_instr *instr,
+                   nir_variable *combined,
+                   unsigned cull_offset)
+{
+   if (instr->type != nir_instr_type_intrinsic)
+      return;
+
+   nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+
+   /* copy_var needs to be lowered to load/store before calling this pass */
+   assert(intrin->intrinsic != nir_intrinsic_copy_var);
+
+   if (intrin->intrinsic != nir_intrinsic_load_var &&
+       intrin->intrinsic != nir_intrinsic_store_var)
+      return;
+
+   nir_deref_var *var_ref = intrin->variables[0];
+   if (var_ref->var->data.mode != combined->data.mode)
+      return;
+
+   if (var_ref->var->data.location != VARYING_SLOT_CLIP_DIST0 &&
+       var_ref->var->data.location != VARYING_SLOT_CULL_DIST0)
+      return;
+
+   /* Update types along the deref chain */
+   const struct glsl_type *type = combined->type;
+   nir_deref *deref = &var_ref->deref;
+   while (deref) {
+      deref->type = type;
+      deref = deref->child;
+      type = glsl_get_array_element(type);
+   }
+
+   /* For cull distances, add an offset to the array index */
+   if (var_ref->var->data.location == VARYING_SLOT_CULL_DIST0) {
+      nir_deref *tail = nir_deref_tail(&intrin->variables[0]->deref);
+      nir_deref_array *array_ref = nir_deref_as_array(tail);
+
+      array_ref->base_offset += cull_offset;
+   }
+
+   /* Point the deref at the combined array */
+   var_ref->var = combined;
+
+   /* There's no need to update writemasks; it's a scalar array. */
+}
+
+static void
+combine_clip_cull(nir_shader *nir,
+                  struct exec_list *vars,
+                  bool store_info)
+{
+   nir_variable *cull = NULL;
+   nir_variable *clip = NULL;
+
+   nir_foreach_variable(var, vars) {
+      if (var->data.location == VARYING_SLOT_CLIP_DIST0)
+         clip = var;
+
+      if (var->data.location == VARYING_SLOT_CULL_DIST0)
+         cull = var;
+   }
+
+   const unsigned clip_array_size = get_unwrapped_array_length(nir, clip);
+   const unsigned cull_array_size = get_unwrapped_array_length(nir, cull);
+
+   if (store_info) {
+      nir->info->clip_distance_array_size = clip_array_size;
+      nir->info->cull_distance_array_size = cull_array_size;
+   }
+
+   if (clip)
+      clip->data.compact = true;
+
+   if (cull)
+      cull->data.compact = true;
+
+   if (cull_array_size > 0) {
+      if (clip_array_size == 0) {
+         /* No clip distances, just change the cull distance location */
+         cull->data.location = VARYING_SLOT_CLIP_DIST0;
+      } else {
+         /* Turn the ClipDistance array into a combined one */
+         update_type(clip, nir->stage, clip_array_size + cull_array_size);
+
+         /* Rewrite CullDistance to reference the combined array */
+         nir_foreach_function(function, nir) {
+            if (function->impl) {
+               nir_foreach_block(block, function->impl) {
+                  nir_foreach_instr(instr, block) {
+                     rewrite_references(instr, clip, clip_array_size);
+                  }
+               }
+            }
+         }
+
+         /* Delete the old CullDistance variable */
+         exec_node_remove(&cull->node);
+         ralloc_free(cull);
+      }
+   }
+}
+
+void
+nir_lower_clip_cull_distance_arrays(nir_shader *nir)
+{
+   if (nir->stage <= MESA_SHADER_GEOMETRY)
+      combine_clip_cull(nir, &nir->outputs, true);
+
+   if (nir->stage > MESA_SHADER_VERTEX)
+      combine_clip_cull(nir, &nir->inputs, false);
+}