nir: add varying array splitting pass

V2:
 - fix matrix support, non-array matrices were being skipped in v1

v3:
 - handle lowering of tcs output loads correctly
 - correctly mark indirect locations for either in or out not both
   when processing a stage.
 - use nir_src_copy() when lowering stores.

Reviewed-by: Nicolai Hähnle <[email protected]>

4 files changed, 386 insertions, 0 deletions

diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources
index 2ab8e163a26..c5094b7f198 100644
--- a/src/compiler/Makefile.sources
+++ b/src/compiler/Makefile.sources
@@ -226,6 +226,7 @@ NIR_FILES = \
 	nir/nir_lower_indirect_derefs.c \
 	nir/nir_lower_int64.c \
 	nir/nir_lower_io.c \
+	nir/nir_lower_io_arrays_to_elements.c \
 	nir/nir_lower_io_to_temporaries.c \
 	nir/nir_lower_io_to_scalar.c \
 	nir/nir_lower_io_types.c \
diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build
index e5c8326aa06..b61a07773d3 100644
--- a/src/compiler/nir/meson.build
+++ b/src/compiler/nir/meson.build
@@ -114,6 +114,7 @@ files_libnir = files(
   'nir_lower_indirect_derefs.c',
   'nir_lower_int64.c',
   'nir_lower_io.c',
+  'nir_lower_io_arrays_to_elements.c',
   'nir_lower_io_to_temporaries.c',
   'nir_lower_io_to_scalar.c',
   'nir_lower_io_types.c',
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index c01fa6707a4..4c5d976a60d 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2493,6 +2493,7 @@ bool nir_lower_alu_to_scalar(nir_shader *shader);
 bool nir_lower_load_const_to_scalar(nir_shader *shader);
 bool nir_lower_read_invocation_to_scalar(nir_shader *shader);
 bool nir_lower_phis_to_scalar(nir_shader *shader);
+void nir_lower_io_arrays_to_elements(nir_shader *producer, nir_shader *consumer);
 void nir_lower_io_to_scalar(nir_shader *shader, nir_variable_mode mask);
 void nir_lower_io_to_scalar_early(nir_shader *shader, nir_variable_mode mask);
 
diff --git a/src/compiler/nir/nir_lower_io_arrays_to_elements.c b/src/compiler/nir/nir_lower_io_arrays_to_elements.c
new file mode 100644
index 00000000000..94b93e3ec91
--- /dev/null
+++ b/src/compiler/nir/nir_lower_io_arrays_to_elements.c
@@ -0,0 +1,383 @@
+/*
+ * Copyright © 2017 Timothy Arceri
+ *
+ * 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 nir_lower_io_arrays_to_elements.c
+ *
+ * Split arrays/matrices with direct indexing into individual elements. This
+ * will allow optimisation passes to better clean up unused elements.
+ *
+ */
+
+static unsigned
+get_io_offset(nir_builder *b, nir_deref_var *deref, nir_variable *var,
+              unsigned *element_index)
+{
+   nir_deref *tail = &deref->deref;
+
+   /* For per-vertex input arrays (i.e. geometry shader inputs), skip the
+    * outermost array index.  Process the rest normally.
+    */
+   if (nir_is_per_vertex_io(var, b->shader->info.stage)) {
+      tail = tail->child;
+   }
+
+   unsigned offset = 0;
+   while (tail->child != NULL) {
+      tail = tail->child;
+
+      if (tail->deref_type == nir_deref_type_array) {
+         nir_deref_array *deref_array = nir_deref_as_array(tail);
+         assert(deref_array->deref_array_type != nir_deref_array_type_indirect);
+
+         unsigned size = glsl_count_attribute_slots(tail->type, false);
+         offset += size * deref_array->base_offset;
+
+         unsigned num_elements = glsl_type_is_array(tail->type) ?
+            glsl_get_aoa_size(tail->type) : 1;
+
+         num_elements *= glsl_type_is_matrix(glsl_without_array(tail->type)) ?
+            glsl_get_matrix_columns(glsl_without_array(tail->type)) : 1;
+
+         *element_index += num_elements * deref_array->base_offset;
+      } else if (tail->deref_type == nir_deref_type_struct) {
+         /* TODO: we could also add struct splitting support to this pass */
+         break;
+      }
+   }
+
+   return offset;
+}
+
+static nir_variable **
+get_array_elements(struct hash_table *ht, nir_variable *var,
+                   gl_shader_stage stage)
+{
+   nir_variable **elements;
+   struct hash_entry *entry = _mesa_hash_table_search(ht, var);
+   if (!entry) {
+      const struct glsl_type *type = var->type;
+      if (nir_is_per_vertex_io(var, stage)) {
+         assert(glsl_type_is_array(type));
+         type = glsl_get_array_element(type);
+      }
+
+      unsigned num_elements = glsl_type_is_array(type) ?
+         glsl_get_aoa_size(type) : 1;
+
+      num_elements *= glsl_type_is_matrix(glsl_without_array(type)) ?
+         glsl_get_matrix_columns(glsl_without_array(type)) : 1;
+
+      elements = (nir_variable **) calloc(num_elements, sizeof(nir_variable *));
+      _mesa_hash_table_insert(ht, var, elements);
+   } else {
+      elements = (nir_variable **) entry->data;
+   }
+
+   return elements;
+}
+
+static void
+create_array_deref(nir_intrinsic_instr *arr_intr,
+                   nir_intrinsic_instr *element_intr)
+{
+   assert(arr_intr->variables[0]->deref.child);
+
+   nir_deref *parent = &element_intr->variables[0]->deref;
+   nir_deref_array *darr =
+            nir_deref_as_array(arr_intr->variables[0]->deref.child);
+   nir_deref_array *ndarr = nir_deref_array_create(parent);
+
+   ndarr->deref.type = glsl_get_array_element(parent->type);
+   ndarr->deref_array_type = darr->deref_array_type;
+   ndarr->base_offset = darr->base_offset;
+
+   if (ndarr->deref_array_type == nir_deref_array_type_indirect)
+      nir_src_copy(&ndarr->indirect, &darr->indirect, parent);
+
+   element_intr->variables[0]->deref.child = &ndarr->deref;
+}
+
+static void
+lower_array(nir_builder *b, nir_intrinsic_instr *intr, nir_variable *var,
+            struct hash_table *varyings)
+{
+   b->cursor = nir_before_instr(&intr->instr);
+
+   nir_variable **elements =
+      get_array_elements(varyings, var, b->shader->info.stage);
+
+   unsigned elements_index = 0;
+   unsigned io_offset = get_io_offset(b, intr->variables[0], var,
+                                      &elements_index);
+
+   nir_variable *element = elements[elements_index];
+   if (!element) {
+         element = nir_variable_clone(var, b->shader);
+         element->data.location =  var->data.location + io_offset;
+
+         const struct glsl_type *type = glsl_without_array(element->type);
+
+         /* This pass also splits matrices so we need give them a new type. */
+         if (glsl_type_is_matrix(type)) {
+            type = glsl_vector_type(glsl_get_base_type(type),
+                                    glsl_get_vector_elements(type));
+         }
+
+         if (nir_is_per_vertex_io(var, b->shader->info.stage)) {
+            type = glsl_get_array_instance(type,
+                                           glsl_get_length(element->type));
+         }
+
+         element->type = type;
+         elements[elements_index] = element;
+
+         nir_shader_add_variable(b->shader, element);
+   }
+
+   nir_intrinsic_instr *element_intr =
+      nir_intrinsic_instr_create(b->shader, intr->intrinsic);
+   element_intr->num_components = intr->num_components;
+   element_intr->variables[0] = nir_deref_var_create(element_intr, element);
+
+   if (intr->intrinsic != nir_intrinsic_store_var) {
+      nir_ssa_dest_init(&element_intr->instr, &element_intr->dest,
+                        intr->num_components, intr->dest.ssa.bit_size, NULL);
+
+      if (intr->intrinsic == nir_intrinsic_interp_var_at_offset ||
+          intr->intrinsic == nir_intrinsic_interp_var_at_sample) {
+         nir_src_copy(&element_intr->src[0], &intr->src[0],
+                      &element_intr->instr);
+      }
+
+      nir_ssa_def_rewrite_uses(&intr->dest.ssa,
+                               nir_src_for_ssa(&element_intr->dest.ssa));
+   } else {
+      nir_intrinsic_set_write_mask(element_intr,
+                                   nir_intrinsic_write_mask(intr));
+      nir_src_copy(&element_intr->src[0], &intr->src[0],
+                   &element_intr->instr);
+   }
+
+   if (nir_is_per_vertex_io(var, b->shader->info.stage)) {
+      create_array_deref(intr, element_intr);
+   }
+
+   nir_builder_instr_insert(b, &element_intr->instr);
+
+   /* Remove the old load intrinsic */
+   nir_instr_remove(&intr->instr);
+}
+
+static bool
+deref_has_indirect(nir_builder *b, nir_variable *var, nir_deref_var *deref)
+{
+   nir_deref *tail = &deref->deref;
+
+   if (nir_is_per_vertex_io(var, b->shader->info.stage)) {
+      tail = tail->child;
+   }
+
+   for (tail = tail->child; tail; tail = tail->child) {
+      if (tail->deref_type != nir_deref_type_array)
+         continue;
+
+      nir_deref_array *arr = nir_deref_as_array(tail);
+      if (arr->deref_array_type == nir_deref_array_type_indirect)
+         return true;
+   }
+
+   return false;
+}
+
+/* Creates a mask of locations that contains arrays that are indexed via
+ * indirect indexing.
+ */
+static void
+create_indirects_mask(nir_shader *shader, uint64_t *indirects,
+                      uint64_t *patch_indirects, nir_variable_mode mode)
+{
+   nir_foreach_function(function, shader) {
+      if (function->impl) {
+         nir_builder b;
+         nir_builder_init(&b, function->impl);
+
+         nir_foreach_block(block, function->impl) {
+            nir_foreach_instr_safe(instr, block) {
+
+               if (instr->type != nir_instr_type_intrinsic)
+                  continue;
+
+               nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
+
+               if (intr->intrinsic != nir_intrinsic_load_var &&
+                   intr->intrinsic != nir_intrinsic_store_var &&
+                   intr->intrinsic != nir_intrinsic_interp_var_at_centroid &&
+                   intr->intrinsic != nir_intrinsic_interp_var_at_sample &&
+                   intr->intrinsic != nir_intrinsic_interp_var_at_offset)
+                  continue;
+
+               nir_variable *var = intr->variables[0]->var;
+
+               if (var->data.mode != mode)
+                  continue;
+
+               uint64_t loc_mask = 1 << var->data.location;
+               if (var->data.patch) {
+                  if (deref_has_indirect(&b, var, intr->variables[0]))
+                     patch_indirects[var->data.location_frac] |= loc_mask;
+               } else {
+                  if (deref_has_indirect(&b, var, intr->variables[0]))
+                     indirects[var->data.location_frac] |= loc_mask;
+               }
+            }
+         }
+      }
+   }
+}
+
+static void
+lower_io_arrays_to_elements(nir_shader *shader, nir_variable_mode mask,
+                            uint64_t *indirects, uint64_t *patch_indirects,
+                            struct hash_table *varyings)
+{
+   nir_foreach_function(function, shader) {
+      if (function->impl) {
+         nir_builder b;
+         nir_builder_init(&b, function->impl);
+
+         nir_foreach_block(block, function->impl) {
+            nir_foreach_instr_safe(instr, block) {
+               if (instr->type != nir_instr_type_intrinsic)
+                  continue;
+
+               nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
+
+               if (intr->intrinsic != nir_intrinsic_load_var &&
+                   intr->intrinsic != nir_intrinsic_store_var &&
+                   intr->intrinsic != nir_intrinsic_interp_var_at_centroid &&
+                   intr->intrinsic != nir_intrinsic_interp_var_at_sample &&
+                   intr->intrinsic != nir_intrinsic_interp_var_at_offset)
+                  continue;
+
+               nir_variable *var = intr->variables[0]->var;
+
+               /* Skip indirects */
+               uint64_t loc_mask = 1 << var->data.location;
+               if (var->data.patch) {
+                  if (patch_indirects[var->data.location_frac] & loc_mask)
+                     continue;
+               } else {
+                  if (indirects[var->data.location_frac] & loc_mask)
+                     continue;
+               }
+
+               nir_variable_mode mode = var->data.mode;
+
+               const struct glsl_type *type = var->type;
+               if (nir_is_per_vertex_io(var, b.shader->info.stage)) {
+                  assert(glsl_type_is_array(type));
+                  type = glsl_get_array_element(type);
+               }
+
+               /* Skip types we cannot split.
+                *
+                * TODO: Add support for struct splitting.
+                */
+               if ((!glsl_type_is_array(type) && !glsl_type_is_matrix(type))||
+                   glsl_type_is_struct(glsl_without_array(type)))
+                  continue;
+
+               if (var->data.location < VARYING_SLOT_VAR0 &&
+                   var->data.location >= 0)
+                  continue;
+
+               /* Don't bother splitting if we can't opt away any unused
+                * elements.
+                */
+               if (var->data.always_active_io)
+                  continue;
+
+               switch (intr->intrinsic) {
+               case nir_intrinsic_interp_var_at_centroid:
+               case nir_intrinsic_interp_var_at_sample:
+               case nir_intrinsic_interp_var_at_offset:
+               case nir_intrinsic_load_var:
+               case nir_intrinsic_store_var:
+                  if ((mask & nir_var_shader_in && mode == nir_var_shader_in) ||
+                      (mask & nir_var_shader_out && mode == nir_var_shader_out))
+                     lower_array(&b, intr, var, varyings);
+                  break;
+               default:
+                  break;
+               }
+            }
+         }
+      }
+   }
+}
+
+void
+nir_lower_io_arrays_to_elements(nir_shader *producer, nir_shader *consumer)
+{
+   struct hash_table *split_inputs =
+      _mesa_hash_table_create(NULL, _mesa_hash_pointer,
+                              _mesa_key_pointer_equal);
+   struct hash_table *split_outputs =
+      _mesa_hash_table_create(NULL, _mesa_hash_pointer,
+                              _mesa_key_pointer_equal);
+
+   uint64_t indirects[4] = {0}, patch_indirects[4] = {0};
+   create_indirects_mask(producer, indirects, patch_indirects,
+                         nir_var_shader_out);
+   create_indirects_mask(consumer, indirects, patch_indirects,
+                         nir_var_shader_in);
+
+   lower_io_arrays_to_elements(producer, nir_var_shader_out, indirects,
+                               patch_indirects, split_outputs);
+
+   lower_io_arrays_to_elements(consumer, nir_var_shader_in, indirects,
+                               patch_indirects, split_inputs);
+
+   /* Remove old input from the shaders inputs list */
+   struct hash_entry *entry;
+   hash_table_foreach(split_inputs, entry) {
+      nir_variable *var = (nir_variable *) entry->key;
+      exec_node_remove(&var->node);
+
+      free(entry->data);
+   }
+
+   /* Remove old output from the shaders outputs list */
+   hash_table_foreach(split_outputs, entry) {
+      nir_variable *var = (nir_variable *) entry->key;
+      exec_node_remove(&var->node);
+
+      free(entry->data);
+   }
+
+   _mesa_hash_table_destroy(split_inputs, NULL);
+   _mesa_hash_table_destroy(split_outputs, NULL);
+}