/*

  $Id$

  Copyright 1989-2016 MINES ParisTech

  This file is part of PIPS.

  PIPS is free software: you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  any later version.

  PIPS is distributed in the hope that it will be useful, but WITHOUT ANY
  WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE.

  See the GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with PIPS.  If not, see <http://www.gnu.org/licenses/>.

*/
#ifdef HAVE_CONFIG_H
    #include "pips_config.h"
#endif

#include <stdio.h>
#include <stdlib.h>

#include "linear.h"

#include "genC.h"
#include "ri.h"
#include "effects.h"
#include "ri-util.h"
#include "prettyprint.h"
#include "effects-util.h"

#include "misc.h"
#include "properties.h"

#include "resources.h"
#include "pipsdbm.h"
#include "control.h"

#include "eole_private.h"
#include "expressions.h"

#define DEBUG_NAME "TRANSFORMATION_OPTIMIZE_EXPRESSIONS_DEBUG_LEVEL"

/****************************************************************** STRATEGY */

/* this structure defines a strategy for eole.
 */
typedef struct
{
  /* NAME of the strategy */
  string name;

  /* HUFFMAN.
   */
  bool apply_balancing;
  double (*huffman_cost)(expression);
  bool huffman_mode;
  
  /* EOLE. 2 passes.
   */
  string eole_strategy;

  bool apply_eole1;
  string apply_eole1_flags; /* not used yet */

  bool apply_eole2;
  string apply_eole2_flags;

  /* SIMPLIFY.
   */
  bool apply_nary_simplify;
  bool apply_simplify;

  /* GCM CSE 
   */
  bool apply_gcm;

  /* CSE 
   */
  bool apply_cse;

} optimization_strategy, *poptimization_strategy;

/* current strategy.
 */
static poptimization_strategy strategy = NULL;

/************************************************************** EOLE PROCESS */

/* file name prefixes to deal with eole.
 * /tmp should be fast (may be mapped into memory).
 */
#define OUT_FILE_NAME 	"/tmp/pips_to_eole"
#define IN_FILE_NAME	"/tmp/eole_to_pips"

/* property names.
 */
#define EOLE		"EOLE"		/* eole binary */
#define EOLE_FLAGS	"EOLE_FLAGS"	/* default options */
#define EOLE_OPTIONS	"EOLE_OPTIONS"	/* additionnal options */

/* returns the eole command to be executed in an allocated string.
 */
static string 
get_eole_command
  (const char* in, /* input file from eole. */
   const char* out,/* output file to eole. */
   const char* flags)
{
  return strdup(concatenate(get_string_property(EOLE), " ", 
			    flags, " ",
			    get_string_property(EOLE_OPTIONS), 
			    " -S ", strategy->eole_strategy,
			    " -o ", in, " ", out, NULL));
}

/************************************************ EOLE MANAGEABLE EXPRESSION */

static bool is_string_constant(entity e)
{
  basic b = entity_basic(e);

  if (type_functional_p(entity_type(e)) && 
      value_constant_p(entity_initial(e)) && 
      !basic_undefined_p(b))
    return basic_string_p(b);

  return false;
}

static void eole_okay_call_rwt(call c, bool * okay)
{
  if (is_string_constant(call_function(c)))
    *okay = false;

  /* IMPLIED-DO ? others ? */
}

static bool eole_manageable_expression(expression e)
{
  bool okay = true;
  gen_context_multi_recurse(e, &okay,
			    call_domain, gen_true, eole_okay_call_rwt,
			    NULL);
  return okay;
} 

/********************************************************* INTERFACE TO EOLE */

/* extract expressions with loop level information.
 */
typedef struct 
{
  list /* expressionwithlevel */ rhs; /* the list of RHS expressions. */
  list /* entity */ indices; /* the list of loop indices (not used yet). */
} extract_expr_t, * extract_expr_p;

static void add_one_more_expression(expression e, extract_expr_p context)
{
  expressionwithlevel ewl = 
    make_expressionwithlevel(gen_nreverse(gen_copy_seq(context->indices)), e);
  context->rhs = CONS(EXPRESSIONWITHLEVEL, ewl, context->rhs);
}

static bool loop_flt(loop l, extract_expr_p context)
{
  entity index = loop_index(l);
  context->indices = CONS(ENTITY, index, context->indices);
  return true; /* keep on. */
}

static void loop_rwt(loop l, extract_expr_p context)
{
  list tmp = context->indices;
  pips_assert("same index", ENTITY(CAR(context->indices))==loop_index(l));
  context->indices = CDR(context->indices);
  CDR(tmp) = NIL;
  gen_free_list(tmp);
}

/* rhs expressions of assignments.
 */
static bool call_filter(call c, extract_expr_p context)
{
  /* put all manageable expressions arguments... */
  MAP(EXPRESSION, e, 
      if (eole_manageable_expression(e)) add_one_more_expression(e, context), 
      call_arguments(c));
  return false;
}

/* other expressions may be found in loops and so?
 */
static bool expr_filter(expression e, extract_expr_p context)
{
  if (eole_manageable_expression(e))
    add_one_more_expression(e, context);
  return false;
}

static list /* of expressionwithlevel */ 
get_list_of_rhs(statement s)
{
  extract_expr_t context;

  context.rhs = NIL;
  context.indices = NIL;

  gen_context_multi_recurse(s, &context,
			    expression_domain, expr_filter, gen_null,
			    call_domain, call_filter, gen_null,
			    loop_domain, loop_flt, loop_rwt,
			    NULL);

  pips_assert("no indices", context.indices==NIL);
  
  return gen_nreverse(context.rhs);
}

/* export a list of expression of the current module.
 * done thru a convenient reference.
 */
static void write_list_of_rhs(FILE * out, list /* of expressionwithlevel */ le)
{
  /* reference astuce = make_reference(get_current_module_entity(), le);*/
  lexpressionwithlevel lewl = make_lexpressionwithlevel(le);
  write_lexpressionwithlevel(out, lewl);
  lexpressionwithlevel_list(lewl) = NIL;
  free_lexpressionwithlevel(lewl);
}

/* export expressions to eole thru the newgen format.
 * both entities and rhs expressions are exported. 
 */
static void write_to_eole(const char* module, list le, const char* file_name)
{
  FILE * toeole;
  
  pips_debug(3, "writing to eole for module %s\n", module);
  
  toeole = safe_fopen(file_name, "w");
  write_tabulated_entity(toeole);
  write_list_of_rhs(toeole, le);

  safe_fclose(toeole, file_name);
}

#define SIZE_OF_BUFFER 100

static string
read_and_allocate_string_from_file(FILE * file)
{
  int test; 
  char buffer[SIZE_OF_BUFFER];

  test = fscanf(file, "%s",buffer);
  pips_assert("fscanf - read string from file \n",(test==1));

  return strdup(buffer);
}


/* import a list of entity that have been created during the eole
 * transformations and create them
 */
static void 
read_new_entities_from_eole(FILE * file, const char* module){
  int num = 0;
  int i, test;
  string ent_type;
  string const_type;
  int const_size = 0;
  string const_value;
  
  entity e; 
  
  /* read the number of new entities to create */
  test = fscanf(file,"%d\n",&num);
  pips_assert("fscanf - read number of entity",(test==1));
  pips_debug(3,"reading %d new entity from module %s\n", num, module);

  for (i=0;i<num;i++)
  {
    ent_type = read_and_allocate_string_from_file(file);
    
    if (!strcmp(ent_type,"constant")) { /* constant */
      
      const_type = read_and_allocate_string_from_file(file);
      
      test = fscanf(file," %d\n", &const_size);
      pips_assert("fscanf - read entity basic type size\n",(test==1));

      const_value = read_and_allocate_string_from_file(file);

      if (same_string_p(const_type,"int")) {/* int */
	
	/* create integer entity */
	e = make_constant_entity(const_value, is_basic_int, const_size);
	pips_assert("make integer constant entity", entity_consistent_p(e));  
      }
      else if (same_string_p(const_type,"float")) {/* float */
	/* create float entity */
	e = make_constant_entity(const_value, is_basic_float, const_size);
	pips_assert("make float constant entity", entity_consistent_p(e));  
      }
      else if (same_string_p(const_type, "double")) { /* double */
	e = make_constant_entity(const_value, is_basic_float, const_size);
	pips_assert("make float constant entity", entity_consistent_p(e));  
      }
      else
	pips_internal_error("can't create this kind of constant entity: %s",
			    const_type);
      free(const_type);
      free(const_value);
    }
    else 
      pips_internal_error("can't create this kind of entity: %s", ent_type);
    
    free(ent_type);
  }
}   


/* import expressions from eole.
 */
static list /* of expression */
read_from_eole(const char* module, const char* file_name)
{
    FILE * fromeole;
    reference astuce;
    list result;

    pips_debug(3, "reading from eole for module %s\n", module);
    
    fromeole = safe_fopen(file_name, "r");

    /* read entities to create... 
     * should use some newgen type to do so (to share buffers...)
     */
    read_new_entities_from_eole(fromeole, module);

    astuce = read_reference(fromeole);
    result = reference_indices(astuce);
    reference_indices(astuce) = NIL;
    free_reference(astuce);

    return result;
}

/* swap term to term syntax field in expression list, as a side effect...
 */
static void 
swap_syntax_in_expression(  list /* of expressionwithlevel */ lcode,
			    list /* of expression */ lnew)
{
  pips_assert("equal length lists", gen_length(lcode)==gen_length(lnew));
  
  for(; lcode; lcode=CDR(lcode), lnew=CDR(lnew))
    {
      expression old, new;
      syntax tmp;

      old = expressionwithlevel_expression(EXPRESSIONWITHLEVEL(CAR(lcode)));
      new = EXPRESSION(CAR(lnew));
      
      tmp = expression_syntax(old);
      expression_syntax(old) = expression_syntax(new);
      expression_syntax(new) = tmp;	
    }
}

/* apply eole on all expressions in s.
 */
static void 
apply_eole_on_statement(const char* module_name, statement s, const char* flags)
{
  list /* of expressionwithlevel/expression */ le, ln;

  ln = NIL;
  le = get_list_of_rhs(s);
  
  if (gen_length(le)) /* not empty list */
  {
    string in, out, cmd;

    /* create temporary files */
    in = safe_new_tmp_file(IN_FILE_NAME);
    out = safe_new_tmp_file(OUT_FILE_NAME);
    
    /* write informations in out file for EOLE */
    write_to_eole(module_name, le, out);
    
    /* run eole (Evaluation Optimization for Loops and Expressions) 
     * as a separate process.
     */
    cmd = get_eole_command(in, out, flags);
    
    pips_debug(2, "executing: %s\n", cmd);
    
    safe_system(cmd);
    
    /* read optimized expressions from eole */
    ln = read_from_eole(module_name, in);
    
    /* replace the syntax values inside le by the syntax values from ln */
    swap_syntax_in_expression(le, ln);
    
    /* must now free the useless expressions */
    
    
    /* remove temorary files and free allocated memory.
     */
    safe_unlink(out);
    safe_unlink(in);
    
    /* free strings */
    free(out), out = NULL;
    free(in), in = NULL;
    free(cmd), cmd = NULL;
  }
  else 
    pips_debug(3, "no expression for module %s\n", module_name);

  pips_debug(3,"EOLE transformations done for module %s\n", module_name);

  /* free lists */
  gen_free_list(ln);
  gen_free_list(le);
}


/************************************************************* SOME PATTERNS */

/* A + (--B) -> A - B
 * FMA       -> FMS
 */
static entity
  bplus  = NULL,
  uminus = NULL,
  bminus = NULL,
  fmaop  = NULL,
  fmsop  = NULL;

/* returns B if uminus(B), else 0
 */
static expression is_uminus(expression e)
{
  syntax s = expression_syntax(e);
  if (syntax_call_p(s))
  {
    call c = syntax_call(s);
    if (call_function(c)==uminus && gen_length(call_arguments(c))==1)
      return EXPRESSION(CAR(call_arguments(c)));
  }
  return NULL;
}

static void call_simplify_rwt(call c)
{
  if (call_function(c)==bplus)
  {
    list la = call_arguments(c);
    expression e1, e2, me;
    
    pips_assert("2 args to binary plus", gen_length(la)==2);

    e1 = EXPRESSION(CAR(la));
    e2 = EXPRESSION(CAR(CDR(la)));

    me = is_uminus(e2);
    if (me)
    {
      EXPRESSION_(CAR(CDR(la))) = me; /* memory leak */
      call_function(c) = bminus;
      return;
    }

    me = is_uminus(e1);
    if (me)
    {
      EXPRESSION_(CAR(CDR(la))) = me;
      EXPRESSION_(CAR(la)) = e2; /* memory leak */
      call_function(c) = bminus;
      return;
    }
  }
  else if (call_function(c)==fmaop) /* FMA(A,B,-C) => FMS(A,B,C) */
  {
    list la = call_arguments(c);
    expression e3 = EXPRESSION(CAR(CDR(CDR(la)))), me;

    me = is_uminus(e3);
    if (me) 
    {
      /* avoid memory leak */
      gen_free_list(call_arguments(syntax_call(expression_syntax(e3))));
      call_arguments(syntax_call(expression_syntax(e3))) = NIL;
      free_expression(e3);
      
      call_function(c) = fmsop;
      EXPRESSION_(CAR(CDR(CDR(la)))) = me;
    }
  }
}

static void generate_bminus(statement s)
{
  bplus  = entity_intrinsic(PLUS_OPERATOR_NAME);
  uminus = entity_intrinsic(UNARY_MINUS_OPERATOR_NAME);
  bminus = entity_intrinsic(MINUS_OPERATOR_NAME);
  fmaop  = entity_intrinsic(EOLE_FMA_OPERATOR_NAME);
  fmsop  = entity_intrinsic(EOLE_FMS_OPERATOR_NAME);

  gen_recurse(s, call_domain, gen_true, call_simplify_rwt);

  bplus  = NULL;
  uminus = NULL;
  bminus = NULL;
  fmaop  = NULL;
  fmsop  = NULL;
}

/* look for some expressions in s and simplify some patterns.
 */
static void optimize_simplify_patterns(statement s)
{
  /* not implemented yet. */

  /* a + (-b)       -> a - b */
  /* (-b) + a       -> a - b */
  /* fma(a,b,-c) => fms(a,b,c) */
  generate_bminus(s);

  /* a * (1/ b)     -> a / b */
  /* (1/ b) * a     -> a / b */
  /* a + (-b * c)   -> a - (b * c) */
}


/************************************************************ N-ARY SIMPLIFY */

static entity
  multiply = NULL,
  inverse = NULL,
  divide = NULL;

static bool is_inverse(expression e)
{
  syntax s = expression_syntax(e);
  if (!syntax_call_p(s)) return false;
  return call_function(syntax_call(s)) == inverse;
}

static void call_nary_rwt(call c)
{
  entity func = call_function(c);
  list numerator = NIL, denominator = NIL;
  int nnum, nden;
  expression enu, eden;
  
  if (func != multiply) return;
  /* it is a multiply */
  
  MAP(EXPRESSION, e,
  {
    if (is_inverse(e))
      denominator = 
	CONS(EXPRESSION, 
	  EXPRESSION(CAR(call_arguments(syntax_call(expression_syntax(e))))),
	     denominator);
    else
      numerator = CONS(EXPRESSION, e, numerator);
  },
      call_arguments(c));

  nden = gen_length(denominator);
  nnum = gen_length(numerator);

  switch (nden)
  {
  case 0: /* nothing to change */
    gen_free_list(denominator);
    gen_free_list(numerator);
    return;
  case 1:
    eden = EXPRESSION(CAR(denominator));
    gen_free_list(denominator);
    break;
  default:
    eden = call_to_expression(make_call(multiply, denominator));
    break;
  }

  switch (nnum) 
  {
  case 0:
    enu = int_to_expression(1);
    break;
  case 1:
    enu = EXPRESSION(CAR(numerator));
    gen_free_list(numerator);
    break;
  default:
    enu = call_to_expression(make_call(multiply, numerator));
    break;
  }

  call_function(c) = divide;
  gen_free_list(call_arguments(c));
  call_arguments(c) = CONS(EXPRESSION, enu, CONS(EXPRESSION, eden, NIL));
}

static void optimize_simplify_nary_patterns(statement s)
{
  /* N-ARY * and 1/ -> N-ARY* / N-ARY*
   */
  multiply = entity_intrinsic(EOLE_PROD_OPERATOR_NAME);
  inverse  = entity_intrinsic(INVERSE_OPERATOR_NAME);
  divide   = entity_intrinsic("/");

  gen_recurse(s, call_domain, gen_true, call_nary_rwt);

  multiply = NULL;
  inverse  = NULL;
  divide   = NULL;
}


/* forward substitute if only there once. not implemented.
 */

/*********************************************************** EXPRESSION COST */

#if 0
/* computes the expression weight.
 */
static double expression_weight(expression e)
{
  double cost = 0.0E0;
  syntax s = expression_syntax(e);
  if (syntax_call_p(s))
  {
    list args = call_arguments(syntax_call(s));
    cost = gen_length(args) - 1.0E0;
    MAP(EXPRESSION, e, cost += expression_weight(e), args);
  }
  return cost;
}

/* computes the expression depth.
 */
static double expression_depth(expression e)
{
  double cost = 0.0E0;
  syntax s = expression_syntax(e);
  if (syntax_call_p(s))
  {
    MAP(EXPRESSION, e, 
	{ double w = expression_depth(e); cost = cost>w? cost: w; },
	call_arguments(syntax_call(s)));
    cost += 1.0E0; 
    /* too simple... may depend on the function called. complexity tables? */
  }
  return cost;
}
#endif

/* WG */
static double expression_gravity_rc(expression e, double depth)
{
  double cost = 0.0E0;
  syntax s = expression_syntax(e);
  if (syntax_call_p(s))
  {
    MAP(EXPRESSION, e, 
	cost += expression_gravity_rc(e, depth+1.0E0), /* ? */
	call_arguments(syntax_call(s)));
    cost += 1.0E0; /* too simple? */
  }
  return cost;
}

static double expression_gravity(expression e)
{
  return expression_gravity_rc(e, 0.0E0);
}

static double expression_gravity_inv(expression e)
{
  return -expression_gravity(e);
}

/************************************************************* NARY-FICATION */
/* switch binary to nary expressions where possible.
   this is normally done in eole anyway.
*/

typedef enum 
{ 
  not_asocom, /* 0 */
  is_plus, is_mult, 
  is_max, is_min, 
  is_and, is_or 
} 
  asocom_operator_t;

typedef struct
{
  char * binary;
  char * nary;
} 
  binary_to_nary_t;

#define MAX_NAME	"MAX"
#define MIN_NAME	"MIN"

static binary_to_nary_t bton[] = 
{
  { "+", EOLE_SUM_OPERATOR_NAME },
  { "*", EOLE_PROD_OPERATOR_NAME },

  { "MAX",   MAX_NAME },
  { "MIN",   MIN_NAME },

  { "MAX0",  MAX_NAME },
  { "DMAX1", MAX_NAME },
  { "AMAX1", MAX_NAME },
  { "AMAX0", MAX_NAME },

  { "MIN0",  MIN_NAME },
  { "DMIN1", MIN_NAME },
  { "AMIN1", MIN_NAME },
  { "AMIN0", MIN_NAME },
  
  /* ??? .AND. .OR.
   */
  { NULL, NULL }
};

static entity binary_to_nary(entity e)
{
  const char* lname = entity_local_name(e);
  binary_to_nary_t * pbn;

  for (pbn = bton; pbn->binary; pbn++)
    if (same_string_p(pbn->binary, lname))
      return entity_intrinsic(pbn->nary);

  return e;
}

static bool nary_operator_p(entity e)
{
  binary_to_nary_t * pbn;
  const char* lname = entity_local_name(e);

  for (pbn = bton; pbn->nary; pbn++)
    if (same_string_p(pbn->nary, lname))
      return true;

  return false;
}

/* top-down: switch calls to nary form.
 */
static bool nary_call_flt(call c)
{
  call_function(c) = binary_to_nary(call_function(c));
  return true;
}

/* bottom-up: + + -> +
 */
static void nary_call_rwt(call c)
{
  entity called = call_function(c);
  list newl = NIL, oldl = call_arguments(c);

  if (nary_operator_p(called))
    {
      MAP(EXPRESSION, e, 
      {
	syntax s = expression_syntax(e);
	if (syntax_call_p(s) && call_function(syntax_call(s))==called)
	  {
	    newl = gen_nconc(newl, call_arguments(syntax_call(s)));
	    call_arguments(syntax_call(s)) = NIL;
	    free_expression(e);
	  }
	else
	  {
	    newl = gen_nconc(newl, CONS(EXPRESSION, e, NIL));
	  }
      },
          oldl);
    }

  call_arguments(c) = newl;
  gen_free_list(oldl);
}

void naryfication_of_expressions(statement s)
{
  gen_recurse(s, call_domain, nary_call_flt, nary_call_rwt);
}

/*
  top down...

  -    -> + --
  /    -> * 1/ [not on integers]
  -- + -> + -- --
  1/ * -> * 1/ 1/
*/

typedef struct 
{
  string asym;
  string syme;
  string inv;
  bool not_ints;
} symetric_opertor_t;

static symetric_opertor_t symop[] =
{ { "-", "+", "--", false },
  { "/", "*", INVERSE_OPERATOR_NAME, true },
  { NULL, NULL, NULL, false }
};

static symetric_opertor_t * what_operator(entity e, int which_one)
{
  const char* lname = entity_local_name(e);
  symetric_opertor_t * sot;
  for (sot = symop; sot->asym; sot++)
    {
      if ((which_one==1 && same_string_p(lname, sot->asym)) ||
	  (which_one==0 && same_string_p(lname, sot->inv)) ||
	  (which_one==2 && same_string_p(lname, sot->syme)))
	return sot;
    }
  return NULL;
}

entity inverse_operator_of(entity e)
{
  symetric_opertor_t * sot = what_operator(e, 2);
  if (sot) return entity_intrinsic(sot->inv);
  else return NULL;
}

static bool inv_call_flt(call c)
{
  entity op = call_function(c);
  symetric_opertor_t * so;

  /* switch asymetric operation if needed */
  so = what_operator(op, true);
  if (so)
    {
      bool doit = true;

      if (so->not_ints)
	{
	  /* should use the type_checker results...
	   * maybe it could be implemented also as an analyses
	   * and not only a transformation? Well, I don't know
	   * how to store expression to type data, as expressions
	   * cannot be shared and are not "named" as statements are. FC.
	   */
	  expression tmp = call_to_expression(c);
	  basic b =  basic_of_expression(tmp);
	  if (basic_int_p(b)) doit = false;
	  syntax_call(expression_syntax(tmp)) = call_undefined;
	  free_expression(tmp);
	}
      
      if (doit) /* we have to substitute. */
	{
	  list largs = call_arguments(c);
	  expression second;
	  pips_assert("binary call", gen_length(largs)==2);
	  second = EXPRESSION(CAR(CDR(largs)));

	  call_function(c) = entity_intrinsic(so->syme);
	  expression_syntax(second) = 
	    make_syntax(is_syntax_call,
			make_call(entity_intrinsic(so->inv),
		CONS(EXPRESSION, 
		     make_expression(expression_syntax(second), 
				     normalized_undefined),
		     NIL)));
	}
    }

  /* push down inverse operators if needed. */     
  so = what_operator(op, false);
  if (so)
    {
      list largs = call_arguments(c);
      syntax s;
      pips_assert("one arg to inverse op", gen_length(largs)==1);
      s = expression_syntax(EXPRESSION(CAR(largs)));
      if (syntax_call_p(s))
	{
	  call called = syntax_call(s);
	  if (same_string_p(so->syme, 
			    entity_local_name(call_function(called))))
	    {
	      /* memory leak... */
	      entity invop = call_function(c);
	      call_function(c) = call_function(called);
	      call_arguments(c) = call_arguments(called);
	      /* now insert invop */
	      MAP(EXPRESSION, e, 
	      {
		expression_syntax(e) = 
		  make_syntax(is_syntax_call,
		      make_call(invop, 
				CONS(EXPRESSION, 
				     make_expression(expression_syntax(e),
						     normalized_undefined),
				     NIL)));
	      },
	          call_arguments(called));
	    }
	}
    }
  
  return true;
}

void inverse_normalization_of_expressions(statement s)
{
  gen_recurse(s, call_domain, inv_call_flt, gen_null);
}

/**************************************** HUFFMAN ALGORITHM ON AN EXPRESSION */

/* switch nary to binary with huffman algorithm.
 */ 
static entity huffman_nary_operator = NULL;
static entity huffman_binary_operator = NULL;
static double (*huffman_cost)(expression) = NULL;
/* true:  Huffman.
   false: rateau.
*/
static bool huffman_mode = true;

typedef struct
{
  expression expr;
  double cost;
} cost_expression;

/* comparison function for qsort. descending order.
 */
static int cost_expression_cmp(const void * v1, const void * v2)
{
  cost_expression * c1 = (cost_expression *) v1;
  cost_expression * c2 = (cost_expression *) v2;
  if (c1->cost==c2->cost) 
    /* when they are equals another criterion may be used, so as 
       to favor double loads (with neighbor references).
     */
    return 0;
  return 2*(c1->cost<c2->cost) - 1;
}

/* debug function */
/* print informations from an cost_expressions array */
static void
debug_cost_expression_array(string s,
			    cost_expression * tce,
			    int size)
{
  int i;
  pips_debug(9,"%s \n", s);
  pips_debug(9," %d elements in cost_expression array \n", size);

  for (i=0; i<size; i++) {
    pips_debug(9," - %d - expression : ", i); 
    print_expression(tce[i].expr);
    pips_debug(9,"\n - %d - cost : %f \n", i, tce[i].cost);
  }
}

/* build an cost_expression array from an expression list.
 */
static cost_expression * 
list_of_expressions_to_array(
    list /* of expression */ le,
    double (*cost)(expression))
{
  int len = gen_length(le), i=0;
  cost_expression * tce = malloc(len * sizeof(cost_expression));
  pips_assert("enough memory", tce!=NULL);
  
  MAP(EXPRESSION, e, 
  {
    tce[i].expr = e;
    tce[i].cost = cost(e);
    i++;
  },
    le);

  qsort(tce, len, sizeof(cost_expression), cost_expression_cmp);

  ifdebug(3) debug_cost_expression_array("qsort output", tce, len);

  return tce;
}

/* insert ce in tce[0..n-1] by decreassing order.
 */
static void 
insert_sorted_into_array(cost_expression * tce, int n, cost_expression ce)
{
  int i=0;
  while (i<n && ce.cost<tce[i].cost) i++; /* find where to insert. */
  while (n>=i) tce[n]=tce[n-1], n--;      /* shift tail. */
  tce[i] = ce;                            /* insert. */
}

/* simply insert.
 */
static void
insert_last_into_array(cost_expression * tce, int n, cost_expression ce)
{
  tce[n] = ce;
}

/* apply huffman balancing algorithm if it is a call to 
 * huffman_nary_operator.
 *
 * the prettyprint may only reflect this if the
 * PRETTYPRINT_ALL_PARENTHESES property is set to true.
 */
static void call_rwt(call c)
{
  if (call_function(c)==huffman_nary_operator) 
  {
    /* let us switch to a binary tree. */
    list args = call_arguments(c);
    int nargs = gen_length(args);
    cost_expression * tce;

    pips_debug(4, "dealing with operator %s\n", 
	       entity_name(huffman_nary_operator));

    //pips_assert("several arguments to nary operator", nargs>=2);
    if (nargs < 2)
    {
      fprintf(stderr,"\n[call_rwt] --- (nargs=%d) < 2; Call = %s \n",
	      nargs, entity_name(call_function(c)));
      print_expression(EXPRESSION(CAR(args)));
      return;
    }

    if (nargs==2) /* the call is already binary. */
    {
      call_function(c) = huffman_binary_operator;
      return;
    }
    /* else */

    tce = list_of_expressions_to_array(args, huffman_cost);
    /* drop initial list: */
    gen_free_list(args), args = NIL, call_arguments(c) = NIL;

    while (nargs>2)
    {
      cost_expression ce;
      ce.expr = MakeBinaryCall(huffman_binary_operator,
			       tce[nargs-1].expr, tce[nargs-2].expr);
      ce.cost = huffman_cost(ce.expr);

      if (huffman_mode)	insert_sorted_into_array(tce, nargs-2, ce);
      else      	insert_last_into_array(tce,  nargs-2, ce);

      ifdebug(3) debug_cost_expression_array("insert done", tce, nargs-1);

      nargs--;
    }

    /* last one is done in place. */
    call_function(c) = huffman_binary_operator;
    call_arguments(c) = CONS(EXPRESSION, tce[0].expr,
			     CONS(EXPRESSION, tce[1].expr, NIL));
    free(tce), tce = NULL;
  }
  else 
    pips_debug(3,"non huffman operator : %s\n ", 
	       entity_local_name(call_function(c)));
}

/* apply the huffman balancing on every call to nary_operator
 * and build calls to binary_operator instead, with cost to chose.
 */
static void 
build_binary_operators_with_huffman(
    statement s,
    entity nary_operator,
    entity binary_operator,
    double (*cost)(expression),
    bool mode)
{
  huffman_nary_operator = nary_operator;
  huffman_binary_operator = binary_operator;
  huffman_cost = cost;
  huffman_mode = mode;

  ifdebug(8) print_statement(s);

  gen_multi_recurse(s,
		    call_domain, gen_true, call_rwt,
		    NULL);

  huffman_nary_operator = NULL;
  huffman_binary_operator = NULL;
  huffman_cost = NULL;  
  huffman_mode = true;
}

/* switch nary operators to binary ones.
 * n+ -> +, n* -> *
 * missing: & | and so on.
 */
static void
switch_nary_to_binary(statement s)
{
  entity
    plus = entity_intrinsic(PLUS_OPERATOR_NAME),
    nplus = entity_intrinsic(EOLE_SUM_OPERATOR_NAME),
    mult = entity_intrinsic(MULTIPLY_OPERATOR_NAME),
    nmult = entity_intrinsic(EOLE_PROD_OPERATOR_NAME);

  /* options: another expression cost function could be used.
   * for instance, defining -expression_gravity would build
   * the most unbalanced possible expression tree wrt WG.
   */
  build_binary_operators_with_huffman
    (s, nplus, plus, strategy->huffman_cost, strategy->huffman_mode);
  build_binary_operators_with_huffman
    (s, nmult, mult, strategy->huffman_cost, strategy->huffman_mode);
}

/***************************************************** PREDEFINED STRATEGIES */

/* predefined optimization strategies.
 */
static optimization_strategy 
  strategies[] = 
{
  { 
    /* name */ "P2SC", 
    /* huff */ true, expression_gravity, true,
    /* eole */ "0", true, "", true, "-m",
    /* simp */ true, true,
    /* gcm */  true,
    /* cse */  false
  },
  {
    /* name */ "IA-64",
    /* huff */ true, expression_gravity, true,
    /* eole */ "0", true, "", true, "-m",
    /* simp */ true, true,
    /* gcm */  true,
    /* cse */  false
  },
  {
    /* name */ "R10K",
    /* huff */ true, expression_gravity_inv, false,
    /* eole */ "1", true, "", true, "-m",
    /* simp */ true, true,
    /* gcm */  true,
    /* cse */  false
  },
  { /* EOLE and Huffman and Simplify with gravity - most balanced tree*/
    /* WITHOUT FMA EXTRACTION */
    /* name */ "ultraIIi",
    /* huff */ true, expression_gravity, true,
    /* eole */ "0", true, "", false, "",
    /* simp */ true, true, 
    /* gcm */  false,
    /* cse */  false
  },
  { /* whatever you want */
    /* name */ "test",
    /* huff */ true, expression_gravity, true,
    /* eole */ "0", true, "", true, "-m",
    /* simp */ true, true,
    /* gcm */  false,
    /* cse */  true
  },
  { /* whatever you want */
    /* name */ "test_icm",
    /* huff */ true, expression_gravity, true,
    /* eole */ "0", true, "", true, "-m",
    /* simp */ true, true,
    /* gcm */  true,
    /* cse */  false
  },
  { /* whatever you want */
    /* name */ "test_cse",
    /* huff */ true, expression_gravity, true,
    /* eole */ "0", true, "", true, "-m",
    /* simp */ true, true,
    /* gcm */  false,
    /* cse */  true
  },
  { /* EOLE with gravity criterion only - most balanced tree ! */
    /* name */ "EOLE",
    /* huff */ false, NULL, false,
    /* eole */ "0", true, "", true, "-m",
    /* simp */ false, false, 
    /* gcm */  false,
    /* cse */  false
  },
  { /* EOLE and Huffman and Simplify with gravity - most balanced tree */
    /* name */ "GRAVITY",
    /* huff */ true, expression_gravity, true,
    /* eole */ "0", true, "", true, "-m",
    /* simp */ true, true, 
    /* gcm */  false,
    /* cse */  false
  },
  { /* EOLE and Huffman and Simplify - most UNbalanced tree */
    /* name */ "UNBALANCED",
    /* huff */ true, expression_gravity_inv, false,
    /* eole */ "1", true, "", true, "-m",
    /* simp */ true, true, 
    /* gcm */  false,
    /* cse */  false
  },
  { /* ICM only */
    /* name */ "ICM", 
    /* huff */ false, NULL, false,
    /* eole */ "0", false, "", false, "",
    /* simp */ false, false,
    /* gcm */  true,
    /* cse */  false
  },
  { /* CSE only*/
    /* name */ "CSE", 
    /* huff */ false, NULL, false,
    /* eole */ "0", false, "", false, "",
    /* simp */ false, false,
    /* gcm */  false,
    /* cse */  true
  },
  { /* both ICM and CSE */
    /* name */ "ICMCSE", 
    /* huff */ false, NULL, false,
    /* eole */ "0", false, "", false, "",
    /* simp */ false, false,
    /* gcm */  true,
    /* cse */  true
  },
  { /* Everything must be done */
    /* name */ "FULL", 
    /* huff */ true, expression_gravity, true,
    /* eole */ "0", true, "", true, "-m",
    /* simp */ true, true,
    /* gcm */  true,
    /* cse */  true
  },
  /* this one MUST be the last one! */
  {
    /* name */ NULL, /* default similar to P2SC. */
    /* huff */ true, expression_gravity, true,
    /* eole */ "0", true, "", true, "-m",
    /* simp */ true, true,
    /* gcm */  true,
    /* cse */  true
  }
};

static void set_current_optimization_strategy(void)
{
  const char* name = get_string_property("EOLE_OPTIMIZATION_STRATEGY");
  for (strategy = strategies; strategy->name!=NULL; strategy++)
  {
    if (same_string_p(name, strategy->name))
      return;
  }
  pips_user_warning("'%s' strategy not found, default assumed.\n", name);
}

static void reset_current_optimization_strategy(void)
{
  strategy = NULL;
}


/************************************************** DAVINCI DUMP EXPRESSIONS

This seems to be largely redundant with some functions in
ri-utils/expression.c such as davinci_dump_expression()
*/

#define GRAPH_PREFIX "optimize_expressions_"
#define GRAPH_SUFFIX ".daVinci"

/* dump all expressions in s as davinci graphs.
 */
static void davinci_dump_expressions(
   const char* module_name, string phase, statement s)
{
  string dir, filename;
  FILE * out;

  /* filename: $current.database/$module/$prefix_$phase.$suffix
   */
  dir = db_get_current_workspace_directory();
  filename = strdup(concatenate
      (dir, "/", module_name, "/", GRAPH_PREFIX, phase, GRAPH_SUFFIX, NULL));
  free(dir), dir = NULL;

  out = safe_fopen(filename, "w"); /* directory MUST exist */
  davinci_dump_all_expressions(out, s);
  safe_fclose(out, filename);

  free(filename), filename = NULL;
}


static
void do_convert_to_c_operator(call c) {
    entity op = call_function(c);
    if(ENTITY_PLUS_P(op))
        call_function(c)=entity_intrinsic(PLUS_C_OPERATOR_NAME);
    if(ENTITY_MINUS_P(op))
        call_function(c)=entity_intrinsic(MINUS_C_OPERATOR_NAME);
}
void convert_to_c_operators(void * v) {
    gen_recurse(v,call_domain,gen_true,do_convert_to_c_operator);
}

static
void do_convert_to_standard_operators(call c) {
    entity op = call_function(c);
    if(ENTITY_PLUS_C_P(op) || ENTITY_MINUS_C_P(op) ) {
        basic b0 = basic_of_expression(binary_call_lhs(c)),
              b1 = basic_of_expression(binary_call_rhs(c));
        if(!basic_pointer_p(b0)  && !basic_pointer_p(b1)) {
            if(ENTITY_PLUS_C_P(op))
                call_function(c)=entity_intrinsic(PLUS_OPERATOR_NAME);
            if(ENTITY_MINUS_C_P(op))
                call_function(c)=entity_intrinsic(MINUS_OPERATOR_NAME);
        }
        free_basic(b0);
        free_basic(b1);
    }
}

void convert_to_standard_operators(void * v) {
    gen_recurse(v,call_domain,gen_true,do_convert_to_standard_operators);
}



/* pipsmake interface to apply expression optimization according to
   various strategy.

   The strategy to use is specified with the EOLE_OPTIMIZATION_STRATEGY
   property. The strategies themselves are defined into the strategies[]
   array.

   In general, strategies involve an external optimization tool that is
   not provided with PIPS, so they cannot be used...

   At least the CSE, ICM and ICMCSE work without this tool and can be
   safely used. See the common_subexpression_elimination and icm phase to
   have a direct access to these 2 common working case. Well, it is not
   clear that ICMCSE would work since it would need to refresh the
   effects, which is not done. So the safe way is to use separately these
   2 phases.

   @param[in] module_name

   @return true since it is supposed to always work
*/
bool optimize_expressions(const char* module_name)
{
    statement s;

    debug_on(DEBUG_NAME);

    /* get needed stuff.
     */
    set_current_module_entity(local_name_to_top_level_entity(module_name));
    set_current_module_statement((statement)
        db_get_memory_resource(DBR_CODE, module_name, true));
    set_current_optimization_strategy();


    s = get_current_module_statement();
    convert_to_c_operators(s);

    /* check consistency before optimizations */
    pips_assert("consistency checking before optimizations",
		statement_consistent_p(s));

    ifdebug(1) davinci_dump_expressions(module_name, "initial", s);

    /* do something here.
     */

    /* Could perform more optimizations here...
     */

    /* EOLE Stuff
     */

    if (strategy->apply_eole1)
      apply_eole_on_statement(module_name, s, get_string_property(EOLE_FLAGS));

    /* Could perform more optimizations here...
     */
    /* CSE/ICM + atom
     */

    if (strategy->apply_gcm)
      perform_icm_association(module_name, s);

    if (strategy->apply_cse)
      perform_ac_cse(module_name, s);

    /* EOLE Stuff, second pass for FMA.
     */
    if (strategy->apply_eole2)
      apply_eole_on_statement(module_name, s, strategy->apply_eole2_flags);

    if (strategy->apply_nary_simplify)
      optimize_simplify_nary_patterns(s);

    if (strategy->apply_balancing)
      switch_nary_to_binary(s);

    if (strategy->apply_simplify)
      optimize_simplify_patterns(s);

    /* others?
     */

    /* check consistency after optimizations */
    unnormalize_expression(s);
    clean_up_sequences(s);
    convert_to_standard_operators(s);
    simplify_expressions(s);
    pips_assert("consistency checking after optimizations",
		statement_consistent_p(s));

    ifdebug(1) davinci_dump_expressions(module_name, "final", s);

    module_reorder(s);

    /* return result to pipsdbm
     */
    DB_PUT_MEMORY_RESOURCE(DBR_CODE, module_name, s);

    reset_current_module_entity();
    reset_current_module_statement();
    reset_current_optimization_strategy();

    debug_off();

    return true; /* okay ! */
}