nir: Add a pass for lowering away constant initializers

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>

src/compiler/Makefile.sources

@@ -199,6 +199,7 @@ NIR_FILES = \
 	nir/nir_lower_clamp_color_outputs.c \
 	nir/nir_lower_clip.c \
 	nir/nir_lower_clip_cull_distance_arrays.c \
+	nir/nir_lower_constant_initializers.c \
 	nir/nir_lower_double_ops.c \
 	nir/nir_lower_double_packing.c \
 	nir/nir_lower_drawpixels.c \

src/compiler/nir/nir.h

@@ -2340,6 +2340,8 @@ void nir_lower_io_types(nir_shader *shader);
 void nir_lower_vars_to_ssa(nir_shader *shader);
 
 bool nir_remove_dead_variables(nir_shader *shader, nir_variable_mode modes);
+bool nir_lower_constant_initializers(nir_shader *shader,
+                                     nir_variable_mode modes);
 
 void nir_move_vec_src_uses_to_dest(nir_shader *shader);
 bool nir_lower_vec_to_movs(nir_shader *shader);

src/compiler/nir/nir_lower_constant_initializers.c

@@ -0,0 +1,112 @@
+/*
+ * Copyright © 2016 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"
+
+static bool
+deref_apply_constant_initializer(nir_deref_var *deref, void *state)
+{
+   struct nir_builder *b = state;
+
+   nir_load_const_instr *initializer =
+      nir_deref_get_const_initializer_load(b->shader, deref);
+   nir_builder_instr_insert(b, &initializer->instr);
+
+   nir_store_deref_var(b, deref, &initializer->def, 0xf);
+
+   return true;
+}
+
+static bool
+lower_const_initializer(struct nir_builder *b, struct exec_list *var_list)
+{
+   bool progress = false;
+
+   b->cursor = nir_before_cf_list(&b->impl->body);
+
+   nir_foreach_variable(var, var_list) {
+      if (!var->constant_initializer)
+         continue;
+
+      progress = true;
+
+      nir_deref_var deref;
+      deref.deref.deref_type = nir_deref_type_var,
+      deref.deref.child = NULL;
+      deref.deref.type = var->type,
+      deref.var = var;
+
+      nir_deref_foreach_leaf(&deref, deref_apply_constant_initializer, b);
+
+      var->constant_initializer = NULL;
+   }
+
+   return progress;
+}
+
+bool
+nir_lower_constant_initializers(nir_shader *shader, nir_variable_mode modes)
+{
+   bool progress = false;
+
+   nir_builder builder;
+   if (modes & ~nir_var_local)
+      nir_builder_init(&builder, nir_shader_get_entrypoint(shader));
+
+   if (modes & nir_var_shader_out)
+      progress |= lower_const_initializer(&builder, &shader->outputs);
+
+   if (modes & nir_var_global)
+      progress |= lower_const_initializer(&builder, &shader->globals);
+
+   if (modes & nir_var_system_value)
+      progress |= lower_const_initializer(&builder, &shader->system_values);
+
+   if (progress) {
+      nir_foreach_function(function, shader) {
+         if (function->impl) {
+            nir_metadata_preserve(function->impl, nir_metadata_block_index |
+                                                  nir_metadata_dominance |
+                                                  nir_metadata_live_ssa_defs);
+         }
+      }
+   }
+
+   if (modes & nir_var_local) {
+      nir_foreach_function(function, shader) {
+         if (!function->impl)
+            continue;
+
+         nir_builder_init(&builder, function->impl);
+         if (lower_const_initializer(&builder, &function->impl->locals)) {
+            nir_metadata_preserve(function->impl, nir_metadata_block_index |
+                                                  nir_metadata_dominance |
+                                                  nir_metadata_live_ssa_defs);
+            progress = true;
+         }
+      }
+   }
+
+   return progress;
+}