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/*

 * Copyright © 2011 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_clip_distance.cpp

 *

 * This pass accounts for the difference between the way

 * gl_ClipDistance is declared in standard GLSL (as an array of

 * floats), and the way it is frequently implemented in hardware (as

 * a pair of vec4s, with four clip distances packed into each).

 *

 * The declaration of gl_ClipDistance is replaced with a declaration

 * of gl_ClipDistanceMESA, and any references to gl_ClipDistance are

 * translated to refer to gl_ClipDistanceMESA with the appropriate

 * swizzling of array indices.  For instance:

 *

 *   gl_ClipDistance[i]

 *

 * is translated into:

 *

 *   gl_ClipDistanceMESA[i>>2][i&3]

 *

 * Since some hardware may not internally represent gl_ClipDistance as a pair

 * of vec4's, this lowering pass is optional.  To enable it, set the

 * LowerClipDistance flag in gl_shader_compiler_options to true.

 */

#include "glsl_symbol_table.h"

#include "ir_rvalue_visitor.h"

#include "ir.h"

#include "program/prog_instruction.h" /* For WRITEMASK_* */

class lower_clip_distance_visitor : public ir_rvalue_visitor {

public:

   lower_clip_distance_visitor()

      : progress(false), old_clip_distance_var(NULL),

        new_clip_distance_var(NULL)

   {

   }

   virtual ir_visitor_status visit(ir_variable *);

   void create_indices(ir_rvalue*, ir_rvalue *&, ir_rvalue *&);

   virtual ir_visitor_status visit_leave(ir_assignment *);

   void visit_new_assignment(ir_assignment *ir);

   virtual ir_visitor_status visit_leave(ir_call *);

   virtual void handle_rvalue(ir_rvalue **rvalue);

   void fix_lhs(ir_assignment *);

   bool progress;

   /**

    * Pointer to the declaration of gl_ClipDistance, if found.

    */

   ir_variable *old_clip_distance_var;

   /**

    * Pointer to the newly-created gl_ClipDistanceMESA variable.

    */

   ir_variable *new_clip_distance_var;

};

/**

 * Replace any declaration of gl_ClipDistance as an array of floats with a

 * declaration of gl_ClipDistanceMESA as an array of vec4's.

 */

ir_visitor_status

lower_clip_distance_visitor::visit(ir_variable *ir)

{

   /* No point in looking for the declaration of gl_ClipDistance if

    * we've already found it.

    */

   if (this->old_clip_distance_var)

      return visit_continue;

   if (ir->name && strcmp(ir->name, "gl_ClipDistance") == 0) {

      this->progress = true;

      this->old_clip_distance_var = ir;

      assert (ir->type->is_array());

      assert (ir->type->element_type() == glsl_type::float_type);

      unsigned new_size = (ir->type->array_size() + 3) / 4;

      /* Clone the old var so that we inherit all of its properties */

      this->new_clip_distance_var = ir->clone(ralloc_parent(ir), NULL);

      /* And change the properties that we need to change */

      this->new_clip_distance_var->name

         = ralloc_strdup(this->new_clip_distance_var, "gl_ClipDistanceMESA");

      this->new_clip_distance_var->type

         = glsl_type::get_array_instance(glsl_type::vec4_type, new_size);

      this->new_clip_distance_var->max_array_access = ir->max_array_access / 4;

      ir->replace_with(this->new_clip_distance_var);

   }

   return visit_continue;

}

/**

 * Create the necessary GLSL rvalues to index into gl_ClipDistanceMESA based

 * on the rvalue previously used to index into gl_ClipDistance.

 *

 * \param array_index Selects one of the vec4's in gl_ClipDistanceMESA

 * \param swizzle_index Selects a component within the vec4 selected by

 *        array_index.

 */

void

lower_clip_distance_visitor::create_indices(ir_rvalue *old_index,

                                            ir_rvalue *&array_index,

                                            ir_rvalue *&swizzle_index)

{

   void *ctx = ralloc_parent(old_index);

   /* Make sure old_index is a signed int so that the bitwise "shift" and

    * "and" operations below type check properly.

    */

   if (old_index->type != glsl_type::int_type) {

      assert (old_index->type == glsl_type::uint_type);

      old_index = new(ctx) ir_expression(ir_unop_u2i, old_index);

   }

   ir_constant *old_index_constant = old_index->constant_expression_value();

   if (old_index_constant) {

      /* gl_ClipDistance is being accessed via a constant index.  Don't bother

       * creating expressions to calculate the lowered indices.  Just create

       * constants.

       */

      int const_val = old_index_constant->get_int_component(0);

      array_index = new(ctx) ir_constant(const_val / 4);

      swizzle_index = new(ctx) ir_constant(const_val % 4);

   } else {

      /* Create a variable to hold the value of old_index (so that we

       * don't compute it twice).

       */

      ir_variable *old_index_var = new(ctx) ir_variable(

         glsl_type::int_type, "clip_distance_index", ir_var_temporary);

      this->base_ir->insert_before(old_index_var);

      this->base_ir->insert_before(new(ctx) ir_assignment(

         new(ctx) ir_dereference_variable(old_index_var), old_index));

      /* Create the expression clip_distance_index / 4.  Do this as a bit

       * shift because that's likely to be more efficient.

       */

      array_index = new(ctx) ir_expression(

         ir_binop_rshift, new(ctx) ir_dereference_variable(old_index_var),

         new(ctx) ir_constant(2));

      /* Create the expression clip_distance_index % 4.  Do this as a bitwise

       * AND because that's likely to be more efficient.

       */

      swizzle_index = new(ctx) ir_expression(

         ir_binop_bit_and, new(ctx) ir_dereference_variable(old_index_var),

         new(ctx) ir_constant(3));

   }

}

void

lower_clip_distance_visitor::handle_rvalue(ir_rvalue **rv)

{

   /* If the gl_ClipDistance var hasn't been declared yet, then

    * there's no way this deref can refer to it.

    */

   if (!this->old_clip_distance_var || *rv == NULL)

      return;

   ir_dereference_array *const array_deref = (*rv)->as_dereference_array();

   if (array_deref == NULL)

      return;

   /* Replace any expression that indexes into the gl_ClipDistance array

    * with an expression that indexes into one of the vec4's in

    * gl_ClipDistanceMESA and accesses the appropriate component.

    */

   ir_dereference_variable *old_var_ref =

      array_deref->array->as_dereference_variable();

   if (old_var_ref && old_var_ref->var == this->old_clip_distance_var) {

      this->progress = true;

      ir_rvalue *array_index;

      ir_rvalue *swizzle_index;

      this->create_indices(array_deref->array_index, array_index, swizzle_index);

      void *mem_ctx = ralloc_parent(array_deref);

      ir_dereference_array *const ClipDistanceMESA_deref =

         new(mem_ctx) ir_dereference_array(this->new_clip_distance_var,

                                           array_index);

      ir_expression *const expr =

         new(mem_ctx) ir_expression(ir_binop_vector_extract,

                                    ClipDistanceMESA_deref,

                                    swizzle_index);

      *rv = expr;

   }

}

void

lower_clip_distance_visitor::fix_lhs(ir_assignment *ir)

{

   if (ir->lhs->ir_type == ir_type_expression) {

      void *mem_ctx = ralloc_parent(ir);

      ir_expression *const expr = (ir_expression *) ir->lhs;

      /* The expression must be of the form:

       *

       *     (vector_extract gl_ClipDistanceMESA[i], j).

       */

      assert(expr->operation == ir_binop_vector_extract);

      assert(expr->operands[0]->ir_type == ir_type_dereference_array);

      assert(expr->operands[0]->type == glsl_type::vec4_type);

      ir_dereference *const new_lhs = (ir_dereference *) expr->operands[0];

      ir->rhs = new(mem_ctx) ir_expression(ir_triop_vector_insert,

					   glsl_type::vec4_type,

					   new_lhs->clone(mem_ctx, NULL),

					   ir->rhs,

					   expr->operands[1]);

      ir->set_lhs(new_lhs);

      ir->write_mask = WRITEMASK_XYZW;

   }

}

/**

 * Replace any assignment having gl_ClipDistance (undereferenced) as its LHS

 * or RHS with a sequence of assignments, one for each component of the array.

 * Each of these assignments is lowered to refer to gl_ClipDistanceMESA as

 * appropriate.

 */

ir_visitor_status

lower_clip_distance_visitor::visit_leave(ir_assignment *ir)

{

   /* First invoke the base class visitor.  This causes handle_rvalue() to be

    * called on ir->rhs and ir->condition.

    */

   ir_rvalue_visitor::visit_leave(ir);

   ir_dereference_variable *lhs_var = ir->lhs->as_dereference_variable();

   ir_dereference_variable *rhs_var = ir->rhs->as_dereference_variable();

   if ((lhs_var && lhs_var->var == this->old_clip_distance_var)

       || (rhs_var && rhs_var->var == this->old_clip_distance_var)) {

      /* LHS or RHS of the assignment is the entire gl_ClipDistance array.

       * Since we are reshaping gl_ClipDistance from an array of floats to an

       * array of vec4's, this isn't going to work as a bulk assignment

       * anymore, so unroll it to element-by-element assignments and lower

       * each of them.

       *

       * Note: to unroll into element-by-element assignments, we need to make

       * clones of the LHS and RHS.  This is safe because expressions and

       * l-values are side-effect free.

       */

      void *ctx = ralloc_parent(ir);

      int array_size = this->old_clip_distance_var->type->array_size();

      for (int i = 0; i < array_size; ++i) {

         ir_dereference_array *new_lhs = new(ctx) ir_dereference_array(

            ir->lhs->clone(ctx, NULL), new(ctx) ir_constant(i));

         ir_dereference_array *new_rhs = new(ctx) ir_dereference_array(

            ir->rhs->clone(ctx, NULL), new(ctx) ir_constant(i));

         this->handle_rvalue((ir_rvalue **) &new_rhs);

         /* Handle the LHS after creating the new assignment.  This must

          * happen in this order because handle_rvalue may replace the old LHS

          * with an ir_expression of ir_binop_vector_extract.  Since this is

          * not a valide l-value, this will cause an assertion in the

          * ir_assignment constructor to fail.

          *

          * If this occurs, replace the mangled LHS with a dereference of the

          * vector, and replace the RHS with an ir_triop_vector_insert.

          */

         ir_assignment *const assign = new(ctx) ir_assignment(new_lhs, new_rhs);

         this->handle_rvalue((ir_rvalue **) &assign->lhs);

         this->fix_lhs(assign);

         this->base_ir->insert_before(assign);

      }

      ir->remove();

      return visit_continue;

   }

   /* Handle the LHS as if it were an r-value.  Normally

    * rvalue_visit(ir_assignment *) only visits the RHS, but we need to lower

    * expressions in the LHS as well.

    *

    * This may cause the LHS to get replaced with an ir_expression of

    * ir_binop_vector_extract.  If this occurs, replace it with a dereference

    * of the vector, and replace the RHS with an ir_triop_vector_insert.

    */

   handle_rvalue((ir_rvalue **)&ir->lhs);

   this->fix_lhs(ir);

   return rvalue_visit(ir);

}

/**

 * Set up base_ir properly and call visit_leave() on a newly created

 * ir_assignment node.  This is used in cases where we have to insert an

 * ir_assignment in a place where we know the hierarchical visitor won't see

 * it.

 */

void

lower_clip_distance_visitor::visit_new_assignment(ir_assignment *ir)

{

   ir_instruction *old_base_ir = this->base_ir;

   this->base_ir = ir;

   ir->accept(this);

   this->base_ir = old_base_ir;

}

/**

 * If gl_ClipDistance appears as an argument in an ir_call expression, replace

 * it with a temporary variable, and make sure the ir_call is preceded and/or

 * followed by assignments that copy the contents of the temporary variable to

 * and/or from gl_ClipDistance.  Each of these assignments is then lowered to

 * refer to gl_ClipDistanceMESA.

 */

ir_visitor_status

lower_clip_distance_visitor::visit_leave(ir_call *ir)

{

   void *ctx = ralloc_parent(ir);

   const exec_node *formal_param_node = ir->callee->parameters.head;

   const exec_node *actual_param_node = ir->actual_parameters.head;

   while (!actual_param_node->is_tail_sentinel()) {

      ir_variable *formal_param = (ir_variable *) formal_param_node;

      ir_rvalue *actual_param = (ir_rvalue *) actual_param_node;

      /* Advance formal_param_node and actual_param_node now so that we can

       * safely replace actual_param with another node, if necessary, below.

       */

      formal_param_node = formal_param_node->next;

      actual_param_node = actual_param_node->next;

      ir_dereference_variable *deref = actual_param->as_dereference_variable();

      if (deref && deref->var == this->old_clip_distance_var) {

         /* User is trying to pass the whole gl_ClipDistance array to a

          * function call.  Since we are reshaping gl_ClipDistance from an

          * array of floats to an array of vec4's, this isn't going to work

          * anymore, so use a temporary array instead.

          */

         ir_variable *temp_clip_distance = new(ctx) ir_variable(

            actual_param->type, "temp_clip_distance", ir_var_temporary);

         this->base_ir->insert_before(temp_clip_distance);

         actual_param->replace_with(

            new(ctx) ir_dereference_variable(temp_clip_distance));

         if (formal_param->mode == ir_var_function_in

             || formal_param->mode == ir_var_function_inout) {

            /* Copy from gl_ClipDistance to the temporary before the call.

             * Since we are going to insert this copy before the current

             * instruction, we need to visit it afterwards to make sure it

             * gets lowered.

             */

            ir_assignment *new_assignment = new(ctx) ir_assignment(

               new(ctx) ir_dereference_variable(temp_clip_distance),

               new(ctx) ir_dereference_variable(old_clip_distance_var));

            this->base_ir->insert_before(new_assignment);

            this->visit_new_assignment(new_assignment);

         }

         if (formal_param->mode == ir_var_function_out

             || formal_param->mode == ir_var_function_inout) {

            /* Copy from the temporary to gl_ClipDistance after the call.

             * Since visit_list_elements() has already decided which

             * instruction it's going to visit next, we need to visit

             * afterwards to make sure it gets lowered.

             */

            ir_assignment *new_assignment = new(ctx) ir_assignment(

               new(ctx) ir_dereference_variable(old_clip_distance_var),

               new(ctx) ir_dereference_variable(temp_clip_distance));

            this->base_ir->insert_after(new_assignment);

            this->visit_new_assignment(new_assignment);

         }

      }

   }

   return rvalue_visit(ir);

}

bool

lower_clip_distance(gl_shader *shader)

{

   lower_clip_distance_visitor v;

   visit_list_elements(&v, shader->ir);

   if (v.new_clip_distance_var)

      shader->symbols->add_variable(v.new_clip_distance_var);

   return v.progress;

}