nir: add a pass to remove unused variables

After we lower variables, we want to delete them in order to free up
some memory.

v2: Jason Ekstrand <jason.ekstrand@intel.com>:
    whitespace fixes

src/glsl/Makefile.sources

@@ -22,6 +22,7 @@ NIR_FILES = \
 	$(GLSL_SRCDIR)/nir/nir_opcodes.c \
 	$(GLSL_SRCDIR)/nir/nir_opcodes.h \
 	$(GLSL_SRCDIR)/nir/nir_print.c \
+	$(GLSL_SRCDIR)/nir/nir_remove_dead_variables.c \
 	$(GLSL_SRCDIR)/nir/nir_validate.c \
 	$(GLSL_SRCDIR)/nir/nir_types.cpp \
 	$(GLSL_SRCDIR)/nir/glsl_to_nir.cpp

src/glsl/nir/nir.h

@@ -1252,6 +1252,8 @@ void nir_lower_variables_scalar(nir_shader *shader, bool lower_globals,
                                 bool lower_io, bool add_names,
                                 bool native_integers);
 
+void nir_remove_dead_variables(nir_shader *shader);
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif

src/glsl/nir/nir_remove_dead_variables.c

@@ -0,0 +1,138 @@
+/*
+ * Copyright © 2014 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.
+ *
+ * Authors:
+ *    Connor Abbott (cwabbott0@gmail.com)
+ *
+ */
+
+#include "nir.h"
+
+static void
+add_var_use_intrinsic(nir_intrinsic_instr *instr, struct set *live)
+{
+   unsigned num_vars = nir_intrinsic_infos[instr->intrinsic].num_variables;
+   for (unsigned i = 0; i < num_vars; i++) {
+      nir_variable *var = instr->variables[i]->var;
+      _mesa_set_add(live, _mesa_hash_pointer(var), var);
+   }
+}
+
+static void
+add_var_use_call(nir_call_instr *instr, struct set *live)
+{
+   if (instr->return_deref != NULL) {
+      nir_variable *var = instr->return_deref->var;
+      _mesa_set_add(live, _mesa_hash_pointer(var), var);
+   }
+
+   for (unsigned i = 0; i < instr->num_params; i++) {
+      nir_variable *var = instr->params[i]->var;
+      _mesa_set_add(live, _mesa_hash_pointer(var), var);
+   }
+}
+
+static void
+add_var_use_tex(nir_tex_instr *instr, struct set *live)
+{
+   if (instr->sampler != NULL) {
+      nir_variable *var = instr->sampler->var;
+      _mesa_set_add(live, _mesa_hash_pointer(var), var);
+   }
+}
+
+static bool
+add_var_use_block(nir_block *block, void *state)
+{
+   struct set *live = (struct set *) state;
+
+   nir_foreach_instr(block, instr) {
+      switch(instr->type) {
+      case nir_instr_type_intrinsic:
+         add_var_use_intrinsic(nir_instr_as_intrinsic(instr), live);
+         break;
+
+      case nir_instr_type_call:
+         add_var_use_call(nir_instr_as_call(instr), live);
+         break;
+
+      case nir_instr_type_texture:
+         add_var_use_tex(nir_instr_as_texture(instr), live);
+         break;
+
+      default:
+         break;
+      }
+   }
+
+   return true;
+}
+
+static void
+add_var_use_shader(nir_shader *shader, struct set *live)
+{
+   nir_foreach_overload(shader, overload) {
+      if (overload->impl) {
+         nir_foreach_block(overload->impl, add_var_use_block, live);
+      }
+   }
+}
+
+static void
+remove_dead_local_vars(nir_function_impl *impl, struct set *live)
+{
+   foreach_list_typed_safe(nir_variable, var, node, &impl->locals) {
+      struct set_entry *entry =
+         _mesa_set_search(live, _mesa_hash_pointer(var), var);
+      if (entry == NULL)
+         exec_node_remove(&var->node);
+   }
+}
+
+static void
+remove_dead_global_vars(nir_shader *shader, struct set *live)
+{
+   foreach_list_typed_safe(nir_variable, var, node, &shader->globals) {
+      struct set_entry *entry =
+         _mesa_set_search(live, _mesa_hash_pointer(var), var);
+      if (entry == NULL)
+         exec_node_remove(&var->node);
+   }
+}
+
+void
+nir_remove_dead_variables(nir_shader *shader)
+{
+   struct set *live =
+      _mesa_set_create(NULL, _mesa_key_pointer_equal);
+
+   add_var_use_shader(shader, live);
+
+   remove_dead_global_vars(shader, live);
+
+   nir_foreach_overload(shader, overload) {
+      if (overload->impl)
+         remove_dead_local_vars(overload->impl, live);
+   }
+
+   _mesa_set_destroy(live, NULL);
+}