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/*

 * 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_copy_propagation.cpp

 *

 * Moves usage of recently-copied variables to the previous copy of

 * the variable.

 *

 * This should reduce the number of MOV instructions in the generated

 * programs unless copy propagation is also done on the LIR, and may

 * help anyway by triggering other optimizations that live in the HIR.

 */

#include "ir.h"

#include "ir_visitor.h"

#include "ir_basic_block.h"

#include "ir_optimization.h"

#include "glsl_types.h"

class acp_entry : public exec_node

{

public:

   acp_entry(ir_variable *lhs, ir_variable *rhs)

   {

      assert(lhs);

      assert(rhs);

      this->lhs = lhs;

      this->rhs = rhs;

   }

   ir_variable *lhs;

   ir_variable *rhs;

};

class kill_entry : public exec_node

{

public:

   kill_entry(ir_variable *var)

   {

      assert(var);

      this->var = var;

   }

   ir_variable *var;

};

class ir_copy_propagation_visitor : public ir_hierarchical_visitor {

public:

   ir_copy_propagation_visitor()

   {

      progress = false;

      mem_ctx = ralloc_context(0);

      this->acp = new(mem_ctx) exec_list;

      this->kills = new(mem_ctx) exec_list;

   }

   ~ir_copy_propagation_visitor()

   {

      ralloc_free(mem_ctx);

   }

   virtual ir_visitor_status visit(class ir_dereference_variable *);

   virtual ir_visitor_status visit_enter(class ir_loop *);

   virtual ir_visitor_status visit_enter(class ir_function_signature *);

   virtual ir_visitor_status visit_enter(class ir_function *);

   virtual ir_visitor_status visit_leave(class ir_assignment *);

   virtual ir_visitor_status visit_enter(class ir_call *);

   virtual ir_visitor_status visit_enter(class ir_if *);

   void add_copy(ir_assignment *ir);

   void kill(ir_variable *ir);

   void handle_if_block(exec_list *instructions);

   /** List of acp_entry: The available copies to propagate */

   exec_list *acp;

   /**

    * List of kill_entry: The variables whose values were killed in this

    * block.

    */

   exec_list *kills;

   bool progress;

   bool killed_all;

   void *mem_ctx;

};

ir_visitor_status

ir_copy_propagation_visitor::visit_enter(ir_function_signature *ir)

{

   /* Treat entry into a function signature as a completely separate

    * block.  Any instructions at global scope will be shuffled into

    * main() at link time, so they're irrelevant to us.

    */

   exec_list *orig_acp = this->acp;

   exec_list *orig_kills = this->kills;

   bool orig_killed_all = this->killed_all;

   this->acp = new(mem_ctx) exec_list;

   this->kills = new(mem_ctx) exec_list;

   this->killed_all = false;

   visit_list_elements(this, &ir->body);

   this->kills = orig_kills;

   this->acp = orig_acp;

   this->killed_all = orig_killed_all;

   return visit_continue_with_parent;

}

ir_visitor_status

ir_copy_propagation_visitor::visit_leave(ir_assignment *ir)

{

   kill(ir->lhs->variable_referenced());

   add_copy(ir);

   return visit_continue;

}

ir_visitor_status

ir_copy_propagation_visitor::visit_enter(ir_function *ir)

{

   (void) ir;

   return visit_continue;

}

/**

 * Replaces dereferences of ACP RHS variables with ACP LHS variables.

 *

 * This is where the actual copy propagation occurs.  Note that the

 * rewriting of ir_dereference means that the ir_dereference instance

 * must not be shared by multiple IR operations!

 */

ir_visitor_status

ir_copy_propagation_visitor::visit(ir_dereference_variable *ir)

{

   if (this->in_assignee)

      return visit_continue;

   ir_variable *var = ir->var;

   foreach_iter(exec_list_iterator, iter, *this->acp) {

      acp_entry *entry = (acp_entry *)iter.get();

      if (var == entry->lhs) {

	 ir->var = entry->rhs;

	 this->progress = true;

	 break;

      }

   }

   return visit_continue;

}

ir_visitor_status

ir_copy_propagation_visitor::visit_enter(ir_call *ir)

{

   /* Do copy propagation on call parameters, but skip any out params */

   exec_list_iterator sig_param_iter = ir->get_callee()->parameters.iterator();

   foreach_iter(exec_list_iterator, iter, ir->actual_parameters) {

      ir_variable *sig_param = (ir_variable *)sig_param_iter.get();

      ir_instruction *ir = (ir_instruction *)iter.get();

      if (sig_param->mode != ir_var_out && sig_param->mode != ir_var_inout) {

         ir->accept(this);

      }

      sig_param_iter.next();

   }

   /* Since we're unlinked, we don't (necssarily) know the side effects of

    * this call.  So kill all copies.

    */

   acp->make_empty();

   this->killed_all = true;

   return visit_continue_with_parent;

}

void

ir_copy_propagation_visitor::handle_if_block(exec_list *instructions)

{

   exec_list *orig_acp = this->acp;

   exec_list *orig_kills = this->kills;

   bool orig_killed_all = this->killed_all;

   this->acp = new(mem_ctx) exec_list;

   this->kills = new(mem_ctx) exec_list;

   this->killed_all = false;

   /* Populate the initial acp with a copy of the original */

   foreach_iter(exec_list_iterator, iter, *orig_acp) {

      acp_entry *a = (acp_entry *)iter.get();

      this->acp->push_tail(new(this->mem_ctx) acp_entry(a->lhs, a->rhs));

   }

   visit_list_elements(this, instructions);

   if (this->killed_all) {

      orig_acp->make_empty();

   }

   exec_list *new_kills = this->kills;

   this->kills = orig_kills;

   this->acp = orig_acp;

   this->killed_all = this->killed_all || orig_killed_all;

   foreach_iter(exec_list_iterator, iter, *new_kills) {

      kill_entry *k = (kill_entry *)iter.get();

      kill(k->var);

   }

}

ir_visitor_status

ir_copy_propagation_visitor::visit_enter(ir_if *ir)

{

   ir->condition->accept(this);

   handle_if_block(&ir->then_instructions);

   handle_if_block(&ir->else_instructions);

   /* handle_if_block() already descended into the children. */

   return visit_continue_with_parent;

}

ir_visitor_status

ir_copy_propagation_visitor::visit_enter(ir_loop *ir)

{

   exec_list *orig_acp = this->acp;

   exec_list *orig_kills = this->kills;

   bool orig_killed_all = this->killed_all;

   /* FINISHME: For now, the initial acp for loops is totally empty.

    * We could go through once, then go through again with the acp

    * cloned minus the killed entries after the first run through.

    */

   this->acp = new(mem_ctx) exec_list;

   this->kills = new(mem_ctx) exec_list;

   this->killed_all = false;

   visit_list_elements(this, &ir->body_instructions);

   if (this->killed_all) {

      orig_acp->make_empty();

   }

   exec_list *new_kills = this->kills;

   this->kills = orig_kills;

   this->acp = orig_acp;

   this->killed_all = this->killed_all || orig_killed_all;

   foreach_iter(exec_list_iterator, iter, *new_kills) {

      kill_entry *k = (kill_entry *)iter.get();

      kill(k->var);

   }

   /* already descended into the children. */

   return visit_continue_with_parent;

}

void

ir_copy_propagation_visitor::kill(ir_variable *var)

{

   assert(var != NULL);

   /* Remove any entries currently in the ACP for this kill. */

   foreach_iter(exec_list_iterator, iter, *acp) {

      acp_entry *entry = (acp_entry *)iter.get();

      if (entry->lhs == var || entry->rhs == var) {

	 entry->remove();

      }

   }

   /* Add the LHS variable to the list of killed variables in this block.

    */

   this->kills->push_tail(new(this->mem_ctx) kill_entry(var));

}

/**

 * Adds an entry to the available copy list if it's a plain assignment

 * of a variable to a variable.

 */

void

ir_copy_propagation_visitor::add_copy(ir_assignment *ir)

{

   acp_entry *entry;

   if (ir->condition) {

      ir_constant *condition = ir->condition->as_constant();

      if (!condition || !condition->value.b[0])

	 return;

   }

   ir_variable *lhs_var = ir->whole_variable_written();

   ir_variable *rhs_var = ir->rhs->whole_variable_referenced();

   if ((lhs_var != NULL) && (rhs_var != NULL)) {

      if (lhs_var == rhs_var) {

	 /* This is a dumb assignment, but we've conveniently noticed

	  * it here.  Removing it now would mess up the loop iteration

	  * calling us.  Just flag it to not execute, and someone else

	  * will clean up the mess.

	  */

	 ir->condition = new(ralloc_parent(ir)) ir_constant(false);

	 this->progress = true;

      } else {

	 entry = new(this->mem_ctx) acp_entry(lhs_var, rhs_var);

	 this->acp->push_tail(entry);

      }

   }

}

/**

 * Does a copy propagation pass on the code present in the instruction stream.

 */

bool

do_copy_propagation(exec_list *instructions)

{

   ir_copy_propagation_visitor v;

   visit_list_elements(&v, instructions);

   return v.progress;

}