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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 lower_vec_index_to_cond_assign.cpp

 *

 * Turns indexing into vector types to a series of conditional moves

 * of each channel's swizzle into a temporary.

 *

 * Most GPUs don't have a native way to do this operation, and this

 * works around that.  For drivers using both this pass and

 * ir_vec_index_to_swizzle, there's a risk that this pass will happen

 * before sufficient constant folding to find that the array index is

 * constant.  However, we hope that other optimization passes,

 * particularly constant folding of assignment conditions and copy

 * propagation, will result in the same code in the end.

 */

#include "ir.h"

#include "ir_visitor.h"

#include "ir_optimization.h"

#include "glsl_types.h"

/**

 * Visitor class for replacing expressions with ir_constant values.

 */

class ir_vec_index_to_cond_assign_visitor : public ir_hierarchical_visitor {

public:

   ir_vec_index_to_cond_assign_visitor()

   {

      progress = false;

   }

   ir_rvalue *convert_vec_index_to_cond_assign(ir_rvalue *val);

   virtual ir_visitor_status visit_enter(ir_expression *);

   virtual ir_visitor_status visit_enter(ir_swizzle *);

   virtual ir_visitor_status visit_leave(ir_assignment *);

   virtual ir_visitor_status visit_enter(ir_return *);

   virtual ir_visitor_status visit_enter(ir_call *);

   virtual ir_visitor_status visit_enter(ir_if *);

   bool progress;

};

ir_rvalue *

ir_vec_index_to_cond_assign_visitor::convert_vec_index_to_cond_assign(ir_rvalue *ir)

{

   ir_dereference_array *orig_deref = ir->as_dereference_array();

   ir_assignment *assign;

   ir_variable *index, *var;

   ir_dereference *deref;

   ir_expression *condition;

   ir_swizzle *swizzle;

   int i;

   if (!orig_deref)

      return ir;

   if (orig_deref->array->type->is_matrix() ||

       orig_deref->array->type->is_array())

      return ir;

   void *mem_ctx = ralloc_parent(ir);

   assert(orig_deref->array_index->type->base_type == GLSL_TYPE_INT);

   /* Store the index to a temporary to avoid reusing its tree. */

   index = new(base_ir) ir_variable(glsl_type::int_type,

				    "vec_index_tmp_i",

				    ir_var_temporary);

   base_ir->insert_before(index);

   deref = new(base_ir) ir_dereference_variable(index);

   assign = new(base_ir) ir_assignment(deref, orig_deref->array_index, NULL);

   base_ir->insert_before(assign);

   /* Temporary where we store whichever value we swizzle out. */

   var = new(base_ir) ir_variable(ir->type, "vec_index_tmp_v",

				  ir_var_temporary);

   base_ir->insert_before(var);

   /* Generate a conditional move of each vector element to the temp. */

   for (i = 0; i < orig_deref->array->type->vector_elements; i++) {

      deref = new(base_ir) ir_dereference_variable(index);

      condition = new(base_ir) ir_expression(ir_binop_equal,

					     glsl_type::bool_type,

					     deref,

					     new(base_ir) ir_constant(i));

      /* Just clone the rest of the deref chain when trying to get at the

       * underlying variable.

       */

      swizzle = new(base_ir) ir_swizzle(orig_deref->array->clone(mem_ctx, NULL),

					i, 0, 0, 0, 1);

      deref = new(base_ir) ir_dereference_variable(var);

      assign = new(base_ir) ir_assignment(deref, swizzle, condition);

      base_ir->insert_before(assign);

   }

   this->progress = true;

   return new(base_ir) ir_dereference_variable(var);

}

ir_visitor_status

ir_vec_index_to_cond_assign_visitor::visit_enter(ir_expression *ir)

{

   unsigned int i;

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

      ir->operands[i] = convert_vec_index_to_cond_assign(ir->operands[i]);

   }

   return visit_continue;

}

ir_visitor_status

ir_vec_index_to_cond_assign_visitor::visit_enter(ir_swizzle *ir)

{

   /* Can't be hit from normal GLSL, since you can't swizzle a scalar (which

    * the result of indexing a vector is.  But maybe at some point we'll end up

    * using swizzling of scalars for vector construction.

    */

   ir->val = convert_vec_index_to_cond_assign(ir->val);

   return visit_continue;

}

ir_visitor_status

ir_vec_index_to_cond_assign_visitor::visit_leave(ir_assignment *ir)

{

   ir_variable *index, *var;

   ir_dereference_variable *deref;

   ir_assignment *assign;

   int i;

   ir->rhs = convert_vec_index_to_cond_assign(ir->rhs);

   if (ir->condition)

      ir->condition = convert_vec_index_to_cond_assign(ir->condition);

   /* Last, handle the LHS */

   ir_dereference_array *orig_deref = ir->lhs->as_dereference_array();

   if (!orig_deref ||

       orig_deref->array->type->is_matrix() ||

       orig_deref->array->type->is_array())

      return visit_continue;

   void *mem_ctx = ralloc_parent(ir);

   assert(orig_deref->array_index->type->base_type == GLSL_TYPE_INT);

   /* Store the index to a temporary to avoid reusing its tree. */

   index = new(ir) ir_variable(glsl_type::int_type, "vec_index_tmp_i",

			       ir_var_temporary);

   ir->insert_before(index);

   deref = new(ir) ir_dereference_variable(index);

   assign = new(ir) ir_assignment(deref, orig_deref->array_index, NULL);

   ir->insert_before(assign);

   /* Store the RHS to a temporary to avoid reusing its tree. */

   var = new(ir) ir_variable(ir->rhs->type, "vec_index_tmp_v",

			     ir_var_temporary);

   ir->insert_before(var);

   deref = new(ir) ir_dereference_variable(var);

   assign = new(ir) ir_assignment(deref, ir->rhs, NULL);

   ir->insert_before(assign);

   /* Generate a conditional move of each vector element to the temp. */

   for (i = 0; i < orig_deref->array->type->vector_elements; i++) {

      ir_rvalue *condition, *swizzle;

      deref = new(ir) ir_dereference_variable(index);

      condition = new(ir) ir_expression(ir_binop_equal,

					glsl_type::bool_type,

					deref,

					new(ir) ir_constant(i));

      /* Just clone the rest of the deref chain when trying to get at the

       * underlying variable.

       */

      swizzle = new(ir) ir_swizzle(orig_deref->array->clone(mem_ctx, NULL),

				   i, 0, 0, 0, 1);

      deref = new(ir) ir_dereference_variable(var);

      assign = new(ir) ir_assignment(swizzle, deref, condition);

      ir->insert_before(assign);

   }

   ir->remove();

   this->progress = true;

   return visit_continue;

}

ir_visitor_status

ir_vec_index_to_cond_assign_visitor::visit_enter(ir_call *ir)

{

   foreach_iter(exec_list_iterator, iter, *ir) {

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

      ir_rvalue *new_param = convert_vec_index_to_cond_assign(param);

      if (new_param != param) {

	 param->replace_with(new_param);

      }

   }

   return visit_continue;

}

ir_visitor_status

ir_vec_index_to_cond_assign_visitor::visit_enter(ir_return *ir)

{

   if (ir->value) {

      ir->value = convert_vec_index_to_cond_assign(ir->value);

   }

   return visit_continue;

}

ir_visitor_status

ir_vec_index_to_cond_assign_visitor::visit_enter(ir_if *ir)

{

   ir->condition = convert_vec_index_to_cond_assign(ir->condition);

   return visit_continue;

}

bool

do_vec_index_to_cond_assign(exec_list *instructions)

{

   ir_vec_index_to_cond_assign_visitor v;

   visit_list_elements(&v, instructions);

   return v.progress;

}