src/glsl/opt_structure_splitting.cpp

/*
 * 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_structure_splitting.cpp
 *
 * If a structure is only ever referenced by its components, then
 * split those components out to individual variables so they can be
 * handled normally by other optimization passes.
 *
 * This skips structures like uniforms, which need to be accessible as
 * structures for their access by the GL.
 */

#include "ir.h"
#include "ir_visitor.h"
#include "ir_print_visitor.h"
#include "ir_rvalue_visitor.h"
#include "glsl_types.h"

namespace {

static bool debug = false;

// XXX using variable_entry2 here to avoid collision (MSVC multiply-defined
// function) with the variable_entry class seen in ir_variable_refcount.h
// Perhaps we can use the one in ir_variable_refcount.h and make this class
// here go away?
class variable_entry2 : public exec_node
{
public:
   variable_entry2(ir_variable *var)
   {
      this->var = var;
      this->whole_structure_access = 0;
      this->declaration = false;
      this->components = NULL;
      this->mem_ctx = NULL;
   }

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

   /** Number of times the variable is referenced, including assignments. */
   unsigned whole_structure_access;

   /* 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 ralloc context. */
   void *mem_ctx;
};


class ir_structure_reference_visitor : public ir_hierarchical_visitor {
public:
   ir_structure_reference_visitor(void)
   {
      this->mem_ctx = ralloc_context(NULL);
      this->variable_list.make_empty();
   }

   ~ir_structure_reference_visitor(void)
   {
      ralloc_free(mem_ctx);
   }

   virtual ir_visitor_status visit(ir_variable *);
   virtual ir_visitor_status visit(ir_dereference_variable *);
   virtual ir_visitor_status visit_enter(ir_dereference_record *);
   virtual ir_visitor_status visit_enter(ir_assignment *);
   virtual ir_visitor_status visit_enter(ir_function_signature *);

   variable_entry2 *get_variable_entry2(ir_variable *var);

   /* List of variable_entry */
   exec_list variable_list;

   void *mem_ctx;
};

variable_entry2 *
ir_structure_reference_visitor::get_variable_entry2(ir_variable *var)
{
   assert(var);

   if (!var->type->is_record() || var->mode == ir_var_uniform)
      return NULL;

   foreach_iter(exec_list_iterator, iter, this->variable_list) {
      variable_entry2 *entry = (variable_entry2 *)iter.get();
      if (entry->var == var)
	 return entry;
   }

   variable_entry2 *entry = new(mem_ctx) variable_entry2(var);
   this->variable_list.push_tail(entry);
   return entry;
}


ir_visitor_status
ir_structure_reference_visitor::visit(ir_variable *ir)
{
   variable_entry2 *entry = this->get_variable_entry2(ir);

   if (entry)
      entry->declaration = true;

   return visit_continue;
}

ir_visitor_status
ir_structure_reference_visitor::visit(ir_dereference_variable *ir)
{
   ir_variable *const var = ir->variable_referenced();
   variable_entry2 *entry = this->get_variable_entry2(var);

   if (entry)
      entry->whole_structure_access++;

   return visit_continue;
}

ir_visitor_status
ir_structure_reference_visitor::visit_enter(ir_dereference_record *ir)
{
   (void) ir;
   /* Don't descend into the ir_dereference_variable below. */
   return visit_continue_with_parent;
}

ir_visitor_status
ir_structure_reference_visitor::visit_enter(ir_assignment *ir)
{
   /* If there are no structure references yet, no need to bother with
    * processing the expression tree.
    */
   if (this->variable_list.is_empty())
      return visit_continue_with_parent;

   if (ir->lhs->as_dereference_variable() &&
       ir->rhs->as_dereference_variable() &&
       !ir->condition) {
      /* We'll split copies of a structure to copies of components, so don't
       * descend to the ir_dereference_variables.
       */
      return visit_continue_with_parent;
   }
   return visit_continue;
}

ir_visitor_status
ir_structure_reference_visitor::visit_enter(ir_function_signature *ir)
{
   /* We don't have logic for structure-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;
}

class ir_structure_splitting_visitor : public ir_rvalue_visitor {
public:
   ir_structure_splitting_visitor(exec_list *vars)
   {
      this->variable_list = vars;
   }

   virtual ~ir_structure_splitting_visitor()
   {
   }

   virtual ir_visitor_status visit_leave(ir_assignment *);

   void split_deref(ir_dereference **deref);
   void handle_rvalue(ir_rvalue **rvalue);
   variable_entry2 *get_splitting_entry(ir_variable *var);

   exec_list *variable_list;
};

variable_entry2 *
ir_structure_splitting_visitor::get_splitting_entry(ir_variable *var)
{
   assert(var);

   if (!var->type->is_record())
      return NULL;

   foreach_iter(exec_list_iterator, iter, *this->variable_list) {
      variable_entry2 *entry = (variable_entry2 *)iter.get();
      if (entry->var == var) {
	 return entry;
      }
   }

   return NULL;
}

void
ir_structure_splitting_visitor::split_deref(ir_dereference **deref)
{
   if ((*deref)->ir_type != ir_type_dereference_record)
      return;

   ir_dereference_record *deref_record = (ir_dereference_record *)*deref;
   ir_dereference_variable *deref_var = deref_record->record->as_dereference_variable();
   if (!deref_var)
      return;

   variable_entry2 *entry = get_splitting_entry(deref_var->var);
   if (!entry)
      return;

   unsigned int i;
   for (i = 0; i < entry->var->type->length; i++) {
      if (strcmp(deref_record->field,
		 entry->var->type->fields.structure[i].name) == 0)
	 break;
   }
   assert(i != entry->var->type->length);

   *deref = new(entry->mem_ctx) ir_dereference_variable(entry->components[i]);
}

void
ir_structure_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_structure_splitting_visitor::visit_leave(ir_assignment *ir)
{
   ir_dereference_variable *lhs_deref = ir->lhs->as_dereference_variable();
   ir_dereference_variable *rhs_deref = ir->rhs->as_dereference_variable();
   variable_entry2 *lhs_entry = lhs_deref ? get_splitting_entry(lhs_deref->var) : NULL;
   variable_entry2 *rhs_entry = rhs_deref ? get_splitting_entry(rhs_deref->var) : NULL;
   const glsl_type *type = ir->rhs->type;

   if ((lhs_entry || rhs_entry) && !ir->condition) {
      for (unsigned int i = 0; i < type->length; i++) {
	 ir_dereference *new_lhs, *new_rhs;
	 void *mem_ctx = lhs_entry ? lhs_entry->mem_ctx : rhs_entry->mem_ctx;

	 if (lhs_entry) {
	    new_lhs = new(mem_ctx) ir_dereference_variable(lhs_entry->components[i]);
	 } else {
	    new_lhs = new(mem_ctx)
	       ir_dereference_record(ir->lhs->clone(mem_ctx, NULL),
				     type->fields.structure[i].name);
	 }

	 if (rhs_entry) {
	    new_rhs = new(mem_ctx) ir_dereference_variable(rhs_entry->components[i]);
	 } else {
	    new_rhs = new(mem_ctx)
	       ir_dereference_record(ir->rhs->clone(mem_ctx, NULL),
				     type->fields.structure[i].name);
	 }

	 ir->insert_before(new(mem_ctx) ir_assignment(new_lhs,
						      new_rhs,
						      NULL));
      }
      ir->remove();
   } else {
      handle_rvalue(&ir->rhs);
      split_deref(&ir->lhs);
   }

   handle_rvalue(&ir->condition);

   return visit_continue;
}

} /* unnamed namespace */

bool
do_structure_splitting(exec_list *instructions)
{
   ir_structure_reference_visitor refs;

   visit_list_elements(&refs, instructions);

   /* Trim out variables we can't split. */
   foreach_iter(exec_list_iterator, iter, refs.variable_list) {
      variable_entry2 *entry = (variable_entry2 *)iter.get();

      if (debug) {
	 printf("structure %s@%p: decl %d, whole_access %d\n",
		entry->var->name, (void *) entry->var, entry->declaration,
		entry->whole_structure_access);
      }

      if (!entry->declaration || entry->whole_structure_access) {
	 entry->remove();
      }
   }

   if (refs.variable_list.is_empty())
      return false;

   void *mem_ctx = ralloc_context(NULL);

   /* Replace the decls of the structures to be split with their split
    * components.
    */
   foreach_iter(exec_list_iterator, iter, refs.variable_list) {
      variable_entry2 *entry = (variable_entry2 *)iter.get();
      const struct glsl_type *type = entry->var->type;

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

      entry->components = ralloc_array(mem_ctx,
				       ir_variable *,
				       type->length);

      for (unsigned int i = 0; i < entry->var->type->length; i++) {
	 const char *name = ralloc_asprintf(mem_ctx, "%s_%s",
					    entry->var->name,
					    type->fields.structure[i].name);

	 entry->components[i] =
	    new(entry->mem_ctx) ir_variable(type->fields.structure[i].type,
					    name,
					    ir_var_temporary);
	 entry->var->insert_before(entry->components[i]);
      }

      entry->var->remove();
   }

   ir_structure_splitting_visitor split(&refs.variable_list);
   visit_list_elements(&split, instructions);

   ralloc_free(mem_ctx);

   return true;
}