mesa/src/glsl/opt_dead_functions.cpp

/*
 * Copyright © 2010 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.
 */

/**
 * \file opt_dead_functions.cpp
 *
 * Eliminates unused functions from the linked program.
 */

#include "ir.h"
#include "ir_visitor.h"
#include "ir_expression_flattening.h"
#include "glsl_types.h"

namespace {

class signature_entry : public exec_node
{
public:
   signature_entry(ir_function_signature *sig)
   {
      this->signature = sig;
      this->used = false;
   }

   ir_function_signature *signature;
   bool used;
};

class ir_dead_functions_visitor : public ir_hierarchical_visitor {
public:
   ir_dead_functions_visitor()
   {
      this->mem_ctx = ralloc_context(NULL);
   }

   ~ir_dead_functions_visitor()
   {
      ralloc_free(this->mem_ctx);
   }

   virtual ir_visitor_status visit_enter(ir_function_signature *);
   virtual ir_visitor_status visit_enter(ir_call *);

   signature_entry *get_signature_entry(ir_function_signature *var);

   /* List of signature_entry */
   exec_list signature_list;
   void *mem_ctx;
};

} /* unnamed namespace */

signature_entry *
ir_dead_functions_visitor::get_signature_entry(ir_function_signature *sig)
{
   foreach_iter(exec_list_iterator, iter, this->signature_list) {
      signature_entry *entry = (signature_entry *)iter.get();
      if (entry->signature == sig)
	 return entry;
   }

   signature_entry *entry = new(mem_ctx) signature_entry(sig);
   this->signature_list.push_tail(entry);
   return entry;
}


ir_visitor_status
ir_dead_functions_visitor::visit_enter(ir_function_signature *ir)
{
   signature_entry *entry = this->get_signature_entry(ir);

   if (strcmp(ir->function_name(), "main") == 0) {
      entry->used = true;
   }



   return visit_continue;
}


ir_visitor_status
ir_dead_functions_visitor::visit_enter(ir_call *ir)
{
   signature_entry *entry = this->get_signature_entry(ir->callee);

   entry->used = true;

   return visit_continue;
}

bool
do_dead_functions(exec_list *instructions)
{
   ir_dead_functions_visitor v;
   bool progress = false;

   visit_list_elements(&v, instructions);

   /* Now that we've figured out which function signatures are used, remove
    * the unused ones, and remove function definitions that have no more
    * signatures.
    */
    foreach_iter(exec_list_iterator, iter, v.signature_list) {
      signature_entry *entry = (signature_entry *)iter.get();

      if (!entry->used) {
	 entry->signature->remove();
	 delete entry->signature;
	 progress = true;
      }
      delete(entry);
   }

   /* We don't just do this above when we nuked a signature because of
    * const pointers.
    */
   foreach_iter(exec_list_iterator, iter, *instructions) {
      ir_instruction *ir = (ir_instruction *)iter.get();
      ir_function *func = ir->as_function();

      if (func && func->signatures.is_empty()) {
	 /* At this point (post-linking), the symbol table is no
	  * longer in use, so not removing the function from the
	  * symbol table should be OK.
	  */
	 func->remove();
	 delete func;
	 progress = true;
      }
   }

   return progress;
}