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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_tree_grafting.cpp

 *

 * Takes assignments to variables that are dereferenced only once and

 * pastes the RHS expression into where the variable is dereferenced.

 *

 * In the process of various operations like function inlining and

 * tertiary op handling, we'll end up with our expression trees having

 * been chopped up into a series of assignments of short expressions

 * to temps.  Other passes like ir_algebraic.cpp would prefer to see

 * the deepest expression trees they can to try to optimize them.

 *

 * This is a lot like copy propagaton.  In comparison, copy

 * propagation only acts on plain copies, not arbitrary expressions on

 * the RHS.  Generally, we wouldn't want to go pasting some

 * complicated expression everywhere it got used, though, so we don't

 * handle expressions in that pass.

 *

 * The hard part is making sure we don't move an expression across

 * some other assignments that would change the value of the

 * expression.  So we split this into two passes: First, find the

 * variables in our scope which are written to once and read once, and

 * then go through basic blocks seeing if we find an opportunity to

 * move those expressions safely.

 */

#include "ir.h"

#include "ir_visitor.h"

#include "ir_variable_refcount.h"

#include "ir_basic_block.h"

#include "ir_optimization.h"

#include "glsl_types.h"

namespace {

static bool debug = false;

class ir_tree_grafting_visitor : public ir_hierarchical_visitor {

public:

   ir_tree_grafting_visitor(ir_assignment *graft_assign,

			    ir_variable *graft_var)

   {

      this->progress = false;

      this->graft_assign = graft_assign;

      this->graft_var = graft_var;

   }

   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_expression *);

   virtual ir_visitor_status visit_enter(class ir_function *);

   virtual ir_visitor_status visit_enter(class ir_function_signature *);

   virtual ir_visitor_status visit_enter(class ir_if *);

   virtual ir_visitor_status visit_enter(class ir_loop *);

   virtual ir_visitor_status visit_enter(class ir_swizzle *);

   virtual ir_visitor_status visit_enter(class ir_texture *);

   ir_visitor_status check_graft(ir_instruction *ir, ir_variable *var);

   bool do_graft(ir_rvalue **rvalue);

   bool progress;

   ir_variable *graft_var;

   ir_assignment *graft_assign;

};

struct find_deref_info {

   ir_variable *var;

   bool found;

};

void

dereferences_variable_callback(ir_instruction *ir, void *data)

{

   struct find_deref_info *info = (struct find_deref_info *)data;

   ir_dereference_variable *deref = ir->as_dereference_variable();

   if (deref && deref->var == info->var)

      info->found = true;

}

static bool

dereferences_variable(ir_instruction *ir, ir_variable *var)

{

   struct find_deref_info info;

   info.var = var;

   info.found = false;

   visit_tree(ir, dereferences_variable_callback, &info);

   return info.found;

}

bool

ir_tree_grafting_visitor::do_graft(ir_rvalue **rvalue)

{

   if (!*rvalue)

      return false;

   ir_dereference_variable *deref = (*rvalue)->as_dereference_variable();

   if (!deref || deref->var != this->graft_var)

      return false;

   if (debug) {

      printf("GRAFTING:\n");

      this->graft_assign->print();

      printf("\n");

      printf("TO:\n");

      (*rvalue)->print();

      printf("\n");

   }

   this->graft_assign->remove();

   *rvalue = this->graft_assign->rhs;

   this->progress = true;

   return true;

}

ir_visitor_status

ir_tree_grafting_visitor::visit_enter(ir_loop *ir)

{

   (void)ir;

   /* Do not traverse into the body of the loop since that is a

    * different basic block.

    */

   return visit_stop;

}

/**

 * Check if we can continue grafting after writing to a variable.  If the

 * expression we're trying to graft references the variable, we must stop.

 *

 * \param ir   An instruction that writes to a variable.

 * \param var  The variable being updated.

 */

ir_visitor_status

ir_tree_grafting_visitor::check_graft(ir_instruction *ir, ir_variable *var)

{

   if (dereferences_variable(this->graft_assign->rhs, var)) {

      if (debug) {

	 printf("graft killed by: ");

	 ir->print();

	 printf("\n");

      }

      return visit_stop;

   }

   return visit_continue;

}

ir_visitor_status

ir_tree_grafting_visitor::visit_leave(ir_assignment *ir)

{

   if (do_graft(&ir->rhs) ||

       do_graft(&ir->condition))

      return visit_stop;

   /* If this assignment updates a variable used in the assignment

    * we're trying to graft, then we're done.

    */

   return check_graft(ir, ir->lhs->variable_referenced());

}

ir_visitor_status

ir_tree_grafting_visitor::visit_enter(ir_function *ir)

{

   (void) ir;

   return visit_continue_with_parent;

}

ir_visitor_status

ir_tree_grafting_visitor::visit_enter(ir_function_signature *ir)

{

   (void)ir;

   return visit_continue_with_parent;

}

ir_visitor_status

ir_tree_grafting_visitor::visit_enter(ir_call *ir)

{

   exec_list_iterator sig_iter = ir->callee->parameters.iterator();

   /* Reminder: iterating ir_call iterates its parameters. */

   foreach_iter(exec_list_iterator, iter, *ir) {

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

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

      ir_rvalue *new_ir = ir;

      if (sig_param->mode != ir_var_function_in

          && sig_param->mode != ir_var_const_in) {

	 if (check_graft(ir, sig_param) == visit_stop)

	    return visit_stop;

	 continue;

      }

      if (do_graft(&new_ir)) {

	 ir->replace_with(new_ir);

	 return visit_stop;

      }

      sig_iter.next();

   }

   if (ir->return_deref && check_graft(ir, ir->return_deref->var) == visit_stop)

      return visit_stop;

   return visit_continue;

}

ir_visitor_status

ir_tree_grafting_visitor::visit_enter(ir_expression *ir)

{

   for (unsigned int i = 0; i < ir->get_num_operands(); i++) {

      if (do_graft(&ir->operands[i]))

	 return visit_stop;

   }

   return visit_continue;

}

ir_visitor_status

ir_tree_grafting_visitor::visit_enter(ir_if *ir)

{

   if (do_graft(&ir->condition))

      return visit_stop;

   /* Do not traverse into the body of the if-statement since that is a

    * different basic block.

    */

   return visit_continue_with_parent;

}

ir_visitor_status

ir_tree_grafting_visitor::visit_enter(ir_swizzle *ir)

{

   if (do_graft(&ir->val))

      return visit_stop;

   return visit_continue;

}

ir_visitor_status

ir_tree_grafting_visitor::visit_enter(ir_texture *ir)

{

   if (do_graft(&ir->coordinate) ||

       do_graft(&ir->projector) ||

       do_graft(&ir->offset) ||

       do_graft(&ir->shadow_comparitor))

	 return visit_stop;

   switch (ir->op) {

   case ir_tex:

   case ir_lod:

      break;

   case ir_txb:

      if (do_graft(&ir->lod_info.bias))

	 return visit_stop;

      break;

   case ir_txf:

   case ir_txl:

   case ir_txs:

      if (do_graft(&ir->lod_info.lod))

	 return visit_stop;

      break;

   case ir_txf_ms:

      if (do_graft(&ir->lod_info.sample_index))

         return visit_stop;

      break;

   case ir_txd:

      if (do_graft(&ir->lod_info.grad.dPdx) ||

	  do_graft(&ir->lod_info.grad.dPdy))

	 return visit_stop;

      break;

   }

   return visit_continue;

}

struct tree_grafting_info {

   ir_variable_refcount_visitor *refs;

   bool progress;

};

static bool

try_tree_grafting(ir_assignment *start,

		  ir_variable *lhs_var,

		  ir_instruction *bb_last)

{

   ir_tree_grafting_visitor v(start, lhs_var);

   if (debug) {

      printf("trying to graft: ");

      lhs_var->print();

      printf("\n");

   }

   for (ir_instruction *ir = (ir_instruction *)start->next;

	ir != bb_last->next;

	ir = (ir_instruction *)ir->next) {

      if (debug) {

	 printf("- ");

	 ir->print();

	 printf("\n");

      }

      ir_visitor_status s = ir->accept(&v);

      if (s == visit_stop)

	 return v.progress;

   }

   return false;

}

static void

tree_grafting_basic_block(ir_instruction *bb_first,

			  ir_instruction *bb_last,

			  void *data)

{

   struct tree_grafting_info *info = (struct tree_grafting_info *)data;

   ir_instruction *ir, *next;

   for (ir = bb_first, next = (ir_instruction *)ir->next;

	ir != bb_last->next;

	ir = next, next = (ir_instruction *)ir->next) {

      ir_assignment *assign = ir->as_assignment();

      if (!assign)

	 continue;

      ir_variable *lhs_var = assign->whole_variable_written();

      if (!lhs_var)

	 continue;

      if (lhs_var->mode == ir_var_function_out ||

	  lhs_var->mode == ir_var_function_inout ||

          lhs_var->mode == ir_var_shader_out)

	 continue;

      ir_variable_refcount_entry *entry = info->refs->get_variable_entry(lhs_var);

      if (!entry->declaration ||

	  entry->assigned_count != 1 ||

	  entry->referenced_count != 2)

	 continue;

      assert(assign == entry->assign);

      /* Found a possibly graftable assignment.  Now, walk through the

       * rest of the BB seeing if the deref is here, and if nothing interfered with

       * pasting its expression's values in between.

       */

      info->progress |= try_tree_grafting(assign, lhs_var, bb_last);

   }

}

} /* unnamed namespace */

/**

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

 */

bool

do_tree_grafting(exec_list *instructions)

{

   ir_variable_refcount_visitor refs;

   struct tree_grafting_info info;

   info.progress = false;

   info.refs = &refs;

   visit_list_elements(info.refs, instructions);

   call_for_basic_blocks(instructions, tree_grafting_basic_block, &info);

   return info.progress;

}