ir_constant_expression.cpp

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 * Copyright © 2010 Intel Corporation
 *
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 * copy of this software and associated documentation files (the "Software"),
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 * The above copyright notice and this permission notice (including the next
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 * Software.
 *
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/**
 * \file ir_constant_expression.cpp
 * Evaluate and process constant valued expressions
 *
 * In GLSL, constant valued expressions are used in several places.  These
 * must be processed and evaluated very early in the compilation process.
 *
 *    * Sizes of arrays
 *    * Initializers for uniforms
 *    * Initializers for \c const variables
 */

#define NULL 0
#include "ir.h"
#include "ir_visitor.h"
#include "glsl_types.h"

/**
 * Visitor class for evaluating constant expressions
 */
class ir_constant_visitor : public ir_visitor {
public:
   ir_constant_visitor()
      : value(NULL)
   {
      /* empty */
   }

   virtual ~ir_constant_visitor()
   {
      /* empty */
   }

   /**
    * \name Visit methods
    *
    * As typical for the visitor pattern, there must be one \c visit method for
    * each concrete subclass of \c ir_instruction.  Virtual base classes within
    * the hierarchy should not have \c visit methods.
    */
   /*@{*/
   virtual void visit(ir_variable *);
   virtual void visit(ir_label *);
   virtual void visit(ir_function_signature *);
   virtual void visit(ir_function *);
   virtual void visit(ir_expression *);
   virtual void visit(ir_swizzle *);
   virtual void visit(ir_dereference *);
   virtual void visit(ir_assignment *);
   virtual void visit(ir_constant *);
   virtual void visit(ir_call *);
   virtual void visit(ir_return *);
   virtual void visit(ir_if *);
   /*@}*/

   /**
    * Value of the constant expression.
    *
    * \note
    * This field will be \c NULL if the expression is not constant valued.
    */
   /* FINIHSME: This cannot hold values for constant arrays or structures. */
   ir_constant *value;
};


ir_constant *
ir_instruction::constant_expression_value()
{
   ir_constant_visitor visitor;

   this->accept(& visitor);
   return visitor.value;
}


void
ir_constant_visitor::visit(ir_variable *ir)
{
   (void) ir;
   value = NULL;
}


void
ir_constant_visitor::visit(ir_label *ir)
{
   (void) ir;
   value = NULL;
}


void
ir_constant_visitor::visit(ir_function_signature *ir)
{
   (void) ir;
   value = NULL;
}


void
ir_constant_visitor::visit(ir_function *ir)
{
   (void) ir;
   value = NULL;
}

void
ir_constant_visitor::visit(ir_expression *ir)
{
   value = NULL;
   ir_constant *op[2];

   switch (ir->operation) {
   case ir_binop_mul:
      op[0] = ir->operands[0]->constant_expression_value();
      op[1] = ir->operands[1]->constant_expression_value();
      if (op[0] && op[1] && ir->operands[0]->type == ir->operands[1]->type) {
	 if (ir->operands[1]->type == glsl_type::float_type) {
	    value = new ir_constant(op[0]->value.f[0] * op[1]->value.f[0]);
	    value->type = glsl_type::float_type;
	 }
      }
      break;
   case ir_binop_logic_and:
      op[0] = ir->operands[0]->constant_expression_value();
      op[1] = ir->operands[1]->constant_expression_value();
      if (op[0] && op[1]) {
	 value = new ir_constant(op[0]->value.b[0] && op[1]->value.b[0]);
	 value->type = glsl_type::bool_type;
      }
      break;
   case ir_binop_logic_or:
      op[0] = ir->operands[0]->constant_expression_value();
      op[1] = ir->operands[1]->constant_expression_value();
      if (op[0] && op[1]) {
	 value = new ir_constant(op[0]->value.b[0] || op[1]->value.b[0]);
	 value->type = glsl_type::bool_type;
      }
      break;
   default:
      break;
   }
}


void
ir_constant_visitor::visit(ir_swizzle *ir)
{
   (void) ir;
   value = NULL;
}


void
ir_constant_visitor::visit(ir_dereference *ir)
{
   (void) ir;
   value = NULL;
}


void
ir_constant_visitor::visit(ir_assignment *ir)
{
   (void) ir;
   value = NULL;
}


void
ir_constant_visitor::visit(ir_constant *ir)
{
   value = ir;
}


void
ir_constant_visitor::visit(ir_call *ir)
{
   (void) ir;
   value = NULL;
}


void
ir_constant_visitor::visit(ir_return *ir)
{
   (void) ir;
   value = NULL;
}


void
ir_constant_visitor::visit(ir_if *ir)
{
   (void) ir;
   value = NULL;
}