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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_array_splitting.cpp

 *

 * If an array is always dereferenced with a constant index, then

 * split it apart into its elements, making it more amenable to other

 * optimization passes.

 *

 * This skips uniform/varying arrays, which would need careful

 * handling due to their ir->location fields tying them to the GL API

 * and other shader stages.

 */

#include "ir.h"

#include "ir_visitor.h"

#include "ir_rvalue_visitor.h"

#include "glsl_types.h"

static bool debug = false;

namespace {

namespace opt_array_splitting {

class variable_entry : public exec_node

{

public:

   variable_entry(ir_variable *var)

   {

      this->var = var;

      this->split = true;

      this->declaration = false;

      this->components = NULL;

      this->mem_ctx = NULL;

      if (var->type->is_array())

	 this->size = var->type->length;

      else

	 this->size = var->type->matrix_columns;

   }

   ir_variable *var; /* The key: the variable's pointer. */

   unsigned size; /* array length or matrix columns */

   /** Whether this array should be split or not. */

   bool split;

   /* If the variable had a decl we can work with in the instruction

    * stream.  We can't do splitting on function arguments, which

    * don't get this variable set.

    */

   bool declaration;

   ir_variable **components;

   /** ralloc_parent(this->var) -- the shader's talloc context. */

   void *mem_ctx;

};

} /* namespace */

using namespace opt_array_splitting;

/**

 * This class does a walk over the tree, coming up with the set of

 * variables that could be split by looking to see if they are arrays

 * that are only ever constant-index dereferenced.

 */

class ir_array_reference_visitor : public ir_hierarchical_visitor {

public:

   ir_array_reference_visitor(void)

   {

      this->mem_ctx = ralloc_context(NULL);

      this->variable_list.make_empty();

   }

   ~ir_array_reference_visitor(void)

   {

      ralloc_free(mem_ctx);

   }

   bool get_split_list(exec_list *instructions, bool linked);

   virtual ir_visitor_status visit(ir_variable *);

   virtual ir_visitor_status visit(ir_dereference_variable *);

   virtual ir_visitor_status visit_enter(ir_dereference_array *);

   virtual ir_visitor_status visit_enter(ir_function_signature *);

   variable_entry *get_variable_entry(ir_variable *var);

   /* List of variable_entry */

   exec_list variable_list;

   void *mem_ctx;

};

} /* namespace */

variable_entry *

ir_array_reference_visitor::get_variable_entry(ir_variable *var)

{

   assert(var);

   if (var->data.mode != ir_var_auto &&

       var->data.mode != ir_var_temporary)

      return NULL;

   if (!(var->type->is_array() || var->type->is_matrix()))

      return NULL;

   /* If the array hasn't been sized yet, we can't split it.  After

    * linking, this should be resolved.

    */

   if (var->type->is_unsized_array())

      return NULL;

   foreach_in_list(variable_entry, entry, &this->variable_list) {

      if (entry->var == var)

	 return entry;

   }

   variable_entry *entry = new(mem_ctx) variable_entry(var);

   this->variable_list.push_tail(entry);

   return entry;

}

ir_visitor_status

ir_array_reference_visitor::visit(ir_variable *ir)

{

   variable_entry *entry = this->get_variable_entry(ir);

   if (entry)

      entry->declaration = true;

   return visit_continue;

}

ir_visitor_status

ir_array_reference_visitor::visit(ir_dereference_variable *ir)

{

   variable_entry *entry = this->get_variable_entry(ir->var);

   /* If we made it to here without seeing an ir_dereference_array,

    * then the dereference of this array didn't have a constant index

    * (see the visit_continue_with_parent below), so we can't split

    * the variable.

    */

   if (entry)

      entry->split = false;

   return visit_continue;

}

ir_visitor_status

ir_array_reference_visitor::visit_enter(ir_dereference_array *ir)

{

   ir_dereference_variable *deref = ir->array->as_dereference_variable();

   if (!deref)

      return visit_continue;

   variable_entry *entry = this->get_variable_entry(deref->var);

   /* If the access to the array has a variable index, we wouldn't

    * know which split variable this dereference should go to.

    */

   if (entry && !ir->array_index->as_constant())

      entry->split = false;

   return visit_continue_with_parent;

}

ir_visitor_status

ir_array_reference_visitor::visit_enter(ir_function_signature *ir)

{

   /* We don't have logic for array-splitting function arguments,

    * so just look at the body instructions and not the parameter

    * declarations.

    */

   visit_list_elements(this, &ir->body);

   return visit_continue_with_parent;

}

bool

ir_array_reference_visitor::get_split_list(exec_list *instructions,

					   bool linked)

{

   visit_list_elements(this, instructions);

   /* If the shaders aren't linked yet, we can't mess with global

    * declarations, which need to be matched by name across shaders.

    */

   if (!linked) {

      foreach_in_list(ir_instruction, node, instructions) {

	 ir_variable *var = node->as_variable();

	 if (var) {

	    variable_entry *entry = get_variable_entry(var);

	    if (entry)

	       entry->remove();

	 }

      }

   }

   /* Trim out variables we found that we can't split. */

   foreach_in_list_safe(variable_entry, entry, &variable_list) {

      if (debug) {

	 printf("array %s@%p: decl %d, split %d\n",

		entry->var->name, (void *) entry->var, entry->declaration,

		entry->split);

      }

      if (!(entry->declaration && entry->split)) {

	 entry->remove();

      }

   }

   return !variable_list.is_empty();

}

/**

 * This class rewrites the dereferences of arrays that have been split

 * to use the newly created ir_variables for each component.

 */

class ir_array_splitting_visitor : public ir_rvalue_visitor {

public:

   ir_array_splitting_visitor(exec_list *vars)

   {

      this->variable_list = vars;

   }

   virtual ~ir_array_splitting_visitor()

   {

   }

   virtual ir_visitor_status visit_leave(ir_assignment *);

   void split_deref(ir_dereference **deref);

   void handle_rvalue(ir_rvalue **rvalue);

   variable_entry *get_splitting_entry(ir_variable *var);

   exec_list *variable_list;

};

variable_entry *

ir_array_splitting_visitor::get_splitting_entry(ir_variable *var)

{

   assert(var);

   foreach_in_list(variable_entry, entry, this->variable_list) {

      if (entry->var == var) {

	 return entry;

      }

   }

   return NULL;

}

void

ir_array_splitting_visitor::split_deref(ir_dereference **deref)

{

   ir_dereference_array *deref_array = (*deref)->as_dereference_array();

   if (!deref_array)

      return;

   ir_dereference_variable *deref_var = deref_array->array->as_dereference_variable();

   if (!deref_var)

      return;

   ir_variable *var = deref_var->var;

   variable_entry *entry = get_splitting_entry(var);

   if (!entry)

      return;

   ir_constant *constant = deref_array->array_index->as_constant();

   assert(constant);

   if (constant->value.i[0] >= 0 && constant->value.i[0] < (int)entry->size) {

      *deref = new(entry->mem_ctx)

	 ir_dereference_variable(entry->components[constant->value.i[0]]);

   } else {

      /* There was a constant array access beyond the end of the

       * array.  This might have happened due to constant folding

       * after the initial parse.  This produces an undefined value,

       * but shouldn't crash.  Just give them an uninitialized

       * variable.

       */

      ir_variable *temp = new(entry->mem_ctx) ir_variable(deref_array->type,

							  "undef",

							  ir_var_temporary);

      entry->components[0]->insert_before(temp);

      *deref = new(entry->mem_ctx) ir_dereference_variable(temp);

   }

}

void

ir_array_splitting_visitor::handle_rvalue(ir_rvalue **rvalue)

{

   if (!*rvalue)

      return;

   ir_dereference *deref = (*rvalue)->as_dereference();

   if (!deref)

      return;

   split_deref(&deref);

   *rvalue = deref;

}

ir_visitor_status

ir_array_splitting_visitor::visit_leave(ir_assignment *ir)

{

   /* The normal rvalue visitor skips the LHS of assignments, but we

    * need to process those just the same.

    */

   ir_rvalue *lhs = ir->lhs;

   handle_rvalue(&lhs);

   ir->lhs = lhs->as_dereference();

   ir->lhs->accept(this);

   handle_rvalue(&ir->rhs);

   ir->rhs->accept(this);

   if (ir->condition) {

      handle_rvalue(&ir->condition);

      ir->condition->accept(this);

   }

   return visit_continue;

}

bool

optimize_split_arrays(exec_list *instructions, bool linked)

{

   ir_array_reference_visitor refs;

   if (!refs.get_split_list(instructions, linked))

      return false;

   void *mem_ctx = ralloc_context(NULL);

   /* Replace the decls of the arrays to be split with their split

    * components.

    */

   foreach_in_list(variable_entry, entry, &refs.variable_list) {

      const struct glsl_type *type = entry->var->type;

      const struct glsl_type *subtype;

      if (type->is_matrix())

	 subtype = type->column_type();

      else

	 subtype = type->fields.array;

      entry->mem_ctx = ralloc_parent(entry->var);

      entry->components = ralloc_array(mem_ctx,

				       ir_variable *,

				       entry->size);

      for (unsigned int i = 0; i < entry->size; i++) {

	 const char *name = ralloc_asprintf(mem_ctx, "%s_%d",

					    entry->var->name, i);

	 entry->components[i] =

	    new(entry->mem_ctx) ir_variable(subtype, name, ir_var_temporary);

	 entry->var->insert_before(entry->components[i]);

      }

      entry->var->remove();

   }

   ir_array_splitting_visitor split(&refs.variable_list);

   visit_list_elements(&split, instructions);

   if (debug)

      _mesa_print_ir(stdout, instructions, NULL);

   ralloc_free(mem_ctx);

   return true;

}