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/* -*- c++ -*- */

/*

 * 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.

 */

#pragma once

#ifndef LOOP_ANALYSIS_H

#define LOOP_ANALYSIS_H

#include "ir.h"

#include "program/hash_table.h"

/**

 * Analyze and classify all variables used in all loops in the instruction list

 */

extern class loop_state *

analyze_loop_variables(exec_list *instructions);

/**

 * Fill in loop control fields

 *

 * Based on analysis of loop variables, this function tries to remove sequences

 * in the loop of the form

 *

 *  (if (expression bool ...) (break))

 *

 * and fill in the \c ir_loop::from, \c ir_loop::to, and \c ir_loop::counter

 * fields of the \c ir_loop.

 *

 * In this process, some conditional break-statements may be eliminated

 * altogether.  For example, if it is provable that one loop exit condition will

 * always be satisfied before another, the unnecessary exit condition will be

 * removed.

 */

extern bool

set_loop_controls(exec_list *instructions, loop_state *ls);

extern bool

unroll_loops(exec_list *instructions, loop_state *ls, unsigned max_iterations);

/**

 * Tracking for all variables used in a loop

 */

class loop_variable_state : public exec_node {

public:

   class loop_variable *get(const ir_variable *);

   class loop_variable *insert(ir_variable *);

   class loop_terminator *insert(ir_if *);

   /**

    * Loop whose variable state is being tracked by this structure

    */

   ir_loop *loop;

   /**

    * Variables that have not yet been classified

    */

   exec_list variables;

   /**

    * Variables whose values are constant within the body of the loop

    *

    * This list contains \c loop_variable objects.

    */

   exec_list constants;

   /**

    * Induction variables for this loop

    *

    * This list contains \c loop_variable objects.

    */

   exec_list induction_variables;

   /**

    * Simple if-statements that lead to the termination of the loop

    *

    * This list contains \c loop_terminator objects.

    *

    * \sa is_loop_terminator

    */

   exec_list terminators;

   /**

    * Hash table containing all variables accessed in this loop

    */

   hash_table *var_hash;

   /**

    * Maximum number of loop iterations.

    *

    * If this value is negative, then the loop may be infinite.  This actually

    * means that analysis was unable to determine an upper bound on the number

    * of loop iterations.

    */

   int max_iterations;

   /**

    * Number of ir_loop_jump instructions that operate on this loop

    */

   unsigned num_loop_jumps;

   loop_variable_state()

   {

      this->max_iterations = -1;

      this->num_loop_jumps = 0;

      this->var_hash = hash_table_ctor(0, hash_table_pointer_hash,

				       hash_table_pointer_compare);

   }

   ~loop_variable_state()

   {

      hash_table_dtor(this->var_hash);

   }

};

class loop_variable : public exec_node {

public:

   /** The variable in question. */

   ir_variable *var;

   /** Is the variable read in the loop before it is written? */

   bool read_before_write;

   /** Are all variables in the RHS of the assignment loop constants? */

   bool rhs_clean;

   /** Is there an assignment to the variable that is conditional? */

   bool conditional_assignment;

   /** Reference to the first assignment to the variable in the loop body. */

   ir_assignment *first_assignment;

   /** Number of assignments to the variable in the loop body. */

   unsigned num_assignments;

   /**

    * Increment values for loop induction variables

    *

    * Loop induction variables have a single increment of the form

    * \c b * \c biv + \c c, where \c b and \c c are loop constants and \c i

    * is a basic loop induction variable.

    *

    * If \c iv_scale is \c NULL, 1 is used.  If \c biv is the same as \c var,

    * then \c var is a basic loop induction variable.

    */

   /*@{*/

   ir_rvalue *iv_scale;

   ir_variable *biv;

   ir_rvalue *increment;

   /*@}*/

   inline bool is_loop_constant() const

   {

      const bool is_const = (this->num_assignments == 0)

	 || ((this->num_assignments == 1)

	     && !this->conditional_assignment

	     && !this->read_before_write

	     && this->rhs_clean);

      /* If the RHS of *the* assignment is clean, then there must be exactly

       * one assignment of the variable.

       */

      assert((this->rhs_clean && (this->num_assignments == 1))

	     || !this->rhs_clean);

      /* Variables that are marked read-only *MUST* be loop constant.

       */

      assert(!this->var->read_only || (this->var->read_only && is_const));

      return is_const;

   }

};

class loop_terminator : public exec_node {

public:

   ir_if *ir;

};

class loop_state {

public:

   ~loop_state();

   /**

    * Get the loop variable state data for a particular loop

    */

   loop_variable_state *get(const ir_loop *);

   loop_variable_state *insert(ir_loop *ir);

private:

   loop_state();

   /**

    * Hash table containing all loops that have been analyzed.

    */

   hash_table *ht;

   void *mem_ctx;

   friend class loop_analysis;

};

#endif /* LOOP_ANALYSIS_H */