registers.c

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/*
  $Id: registers.c 23495 2018-10-24 09:19:47Z coelho $
 
  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/>.
 
*/
 
// do not compile unless required
#include "phases.h"
#ifdef BUILDER_FORCE_REGISTER_DECLARATIONS
 
#ifdef HAVE_CONFIG_H
    #include "pips_config.h"
#endif
 
#include <stdlib.h>
#include <stdio.h>
 
#include "genC.h"
#include "linear.h"
 
#include "misc.h"
#include "pipsdbm.h"
#include "properties.h"
 
#include "ri.h"
#include "ri-util.h"
 
#include "control.h" // module_reorder
 
/************************************************* DETECT REGISTER VARIABLES */
 
// formal parameters and local variables can be declared registers
// for registers, the cannot be referenced (&i)
// for arrays, the address cannot be used, a[i] and not a, but on sizeof(a)
 
typedef struct {
  set invalidated; // of entities, which cannot be declared "register"
} drv_context;
 
// return first possible variable, or NULL
static entity expression_to_variable(const expression e)
{
  syntax s = expression_syntax(e);
  if (syntax_reference_p(s))
    return reference_variable(syntax_reference(s));
  else if (syntax_call_p(s))
  {
    list la = call_arguments(syntax_call(s));
    if (la)
      return expression_to_variable(EXPRESSION(CAR(la)));
    else
      return NULL;
  }
  else
    return NULL;
}
 
// loop indexes are ok as registers.
 
// detect explicit address-of operators
static bool drv_call_flt(const call c, drv_context * ctx)
{
  entity fun = call_function(c);
  pips_debug(8, "considering call to %s\n", entity_name(fun));
  if (ENTITY_ADDRESS_OF_P(fun)) // & ...
  {
    list la = call_arguments(c);
    pips_assert("one argument to &", gen_length(la)==1);
    entity var = expression_to_variable(EXPRESSION(CAR(la)));
    if (var)
    {
      pips_debug(7, "invalidating variable %s\n", entity_name(var));
      set_add_element(ctx->invalidated, ctx->invalidated, var);
    }
    // else no variable found... should it be allowed?
  }
  return true;
}
 
// detect implicit address-of for arrays
static bool drv_reference_flt(const reference r, drv_context * ctx)
{
  entity var = reference_variable(r);
  if (entity_array_p(var))
  {
    list dims =
      variable_dimensions(type_variable(ultimate_type(entity_type(var))));
    if (gen_length(dims) != gen_length(reference_indices(r)))
      set_add_element(ctx->invalidated, ctx->invalidated, var);
  }
  return true;
}
 
/* recurse in object to detect which variables cannot be declared register
 */
static void drv_collect(gen_chunk * object, drv_context * ctx)
{
  gen_context_multi_recurse(object, ctx,
                            call_domain, drv_call_flt, gen_null,
                            reference_domain, drv_reference_flt, gen_null,
                            // ignore sizeof
                            sizeofexpression_domain, gen_false, gen_null,
                            NULL);
}
 
/********************************************************** CUT DECLARATIONS */
 
typedef struct {
  // entities switched to "register"
  set switched;
  // statement -> list of declaration statements to insert before it
  hash_table newdecls;
  // statement -> direct enclosing sequence
  hash_table outside;
} cd_context;
 
static bool cut_declarations_flt(statement s, cd_context * ctx)
{
  // argh! do not strust statement_declarations necessarily
  if (!declaration_statement_p(s))
    return true;
 
  list decls = statement_declarations(s);
  int ndecls = gen_length(decls);
 
  pips_debug(3, "at statement %"_intFMT", %d declarations\n",
             statement_number(s), ndecls);
  ifdebug(7) {
    // show details...
    FOREACH(entity, vs, decls)
      pips_debug(7, " - variable: %s\n", entity_name(vs));
  }
 
  // check IR consistency
  sequence sq = (sequence) gen_get_ancestor_type(sequence_domain, s);
  pips_assert("declaration statement is in a sequence",
              sq && gen_in_list_p(s, sequence_statements(sq)));
 
  if (ndecls>1)
  {
    // built list of declaration statements
    list lds = NIL;
    // current list of variables
    list nl = NIL;
    // whether statements in nl are switched or not
    bool nswitched = false;
    FOREACH(entity, v, decls)
    {
      pips_debug(4, "%s (%sregister) in statement %"_intFMT"\n",
                 entity_name(v), set_belong_p(ctx->switched, v)? "": "NOT ",
                 statement_number(s));
 
      if (set_belong_p(ctx->switched, v))
      {
        if (nl) // a current list is being constructed
        {
          if (nswitched) // it already contains switched variables
            nl = CONS(entity, v, nl);
          else
          {
            pips_debug(5, "cutting on %s\n", entity_name(v));
            // cut list
            ndecls -= gen_length(nl);
            lds =
              CONS(statement,
                   make_declarations_statement
                   (gen_nreverse(nl), statement_number(s), string_undefined),
                   lds);
            // restart
            nl = CONS(entity, v, NIL), nswitched = true;
          }
        }
        else // first new list
          nl = CONS(entity, v, NIL), nswitched = true;
      }
      else // another unchanged variable
      {
        if (nl)
        {
          if (nswitched) // current list contains switched vars
          {
            pips_debug(5, "cutting S on %s\n", entity_name(v));
            // cut list
            ndecls -= gen_length(nl);
            lds =
              CONS(statement,
                   make_declarations_statement
                   (gen_nreverse(nl), statement_number(s), string_undefined),
                   lds);
            // restart
            nl = CONS(entity, v, NIL), nswitched = false;
          }
          else // non switched vars, insert in homogeneous list
            nl = CONS(entity, v, nl);
        }
        else // first new list
          nl = CONS(entity, v, NIL), nswitched = false;
      }
    }
 
    pips_assert("all declarations are managed", ndecls==(int) gen_length(nl));
 
    // store lds for later insertions
    // I do not that now because we are still recurring in the statements...
    if (lds)
    {
      hash_put(ctx->newdecls, s, gen_nreverse(lds));
      hash_put(ctx->outside, s, sq);
      // last list kept in current statement
      gen_free_list(statement_declarations(s));
      statement_declarations(s) = gen_nreverse(nl);
    }
    else // no change
      gen_free_list(nl);
  }
  return true;
}
 
// C99 6.7.1 2: variable can be at most in 1 storage class in
//               auto, extern, static, register, (typedef)
static bool variable_can_switch_to_register(entity var)
{
  if ((!get_bool_property("FORCE_REGISTER_POINTER") && entity_pointer_p(var)) ||
      (!get_bool_property("FORCE_REGISTER_ARRAY") && entity_array_p(var)) ||
      (!get_bool_property("FORCE_REGISTER_FORMAL") && entity_formal_p(var)))
    return false;
  else if (top_level_entity_p(var) || // extern
           entity_static_variable_p(var)) // static
    return false;
  else if (entity_variable_p(var)) // others
  {
    FOREACH(qualifier, q, variable_qualifiers(type_variable(entity_type(var))))
      if (qualifier_register_p(q))
        return false;
 
    return true;
  }
  else
    return false;
}
 
/* @brief modify list of qualifiers so that it includes register and *not* auto
 * @param lq initial list, which is freed on the fly
 * @return a newly allocated qualifier list
 */
static list make_it_register(list lq)
{
  list nlq = NIL;
  FOREACH(qualifier, q, lq)
  {
    if (!qualifier_register_p(q) && !qualifier_auto_p(q))
      nlq = CONS(qualifier, q, nlq);
    else
      free_qualifier(q);
  }
  gen_free_list(lq);
  return CONS(qualifier, make_qualifier_register(), gen_nreverse(nlq));
}
 
bool force_register_declarations(const char * module_name)
{
  statement stat = (statement)
    db_get_memory_resource(DBR_CODE, module_name, true);
  entity module = module_name_to_entity(module_name);
 
  set_current_module_statement(stat);
  set_current_module_entity(module);
 
  debug_on("PIPS_REGISTERS_DEBUG_LEVEL");
 
  // collect variables that cannot be registers
  drv_context ctx = { set_make(set_pointer) };
  set switched = set_make(set_pointer);
 
  // in the code
  drv_collect((void *) stat, &ctx);
 
  // and in variable initializations
  list vars = entity_declarations(module);
 
  FOREACH(entity, var, vars)
    drv_collect((void *) entity_initial(var), &ctx);
 
  // now switch those variables that could be
  FOREACH(entity, var, vars)
  {
    if (entity_variable_p(var) &&
        (entity_formal_p(var) || storage_ram_p(entity_storage(var))) &&
        !set_belong_p(ctx.invalidated, var) &&
        variable_can_switch_to_register(var))
    {
      pips_debug(2, "force %s as register\n", entity_name(var));
      variable v = type_variable(entity_type(var));
      variable_qualifiers(v) = make_it_register(variable_qualifiers(v));
      set_add_element(switched, switched, var);
    }
    else
      pips_debug(3, "variable %s kept\n", entity_name(var));
  }
 
  // now we have to possibly cut declaration lists as they must be homogeneous
  // think of "int i1, r1, i2;" where only r1 switched to register.
  cd_context cd = {
    switched, hash_table_make(hash_pointer, 0), hash_table_make(hash_pointer, 0)
  };
  gen_context_recurse(stat, &cd,
                      statement_domain, cut_declarations_flt, gen_null2);
 
  // perform actual insertions.
  HASH_FOREACH(statement, s, list, l, cd.newdecls)
  {
    pips_assert("sequence of statement", hash_defined_p(cd.outside, s));
    sequence sq = (sequence) hash_get(cd.outside, s);
 
    // put initial comment on the front statement
    statement front = STATEMENT(CAR(l));
    statement_comments(front) = statement_comments(s);
    statement_comments(s) = string_undefined;
 
    // link into the sequence
    sequence_statements(sq) =
      gen_insert_list(l, s, sequence_statements(sq), true);
  }
 
  // cleanup allocated stuff
  set_free(ctx.invalidated), ctx.invalidated = NULL;
  set_free(switched), switched = NULL;
  hash_table_free(cd.newdecls);
  hash_table_free(cd.outside);
 
  debug_off();
 
  // return result to pipsdbm
  // should not be needed: clean_up_sequences(stat);
  module_reorder(stat);
  DB_PUT_MEMORY_RESOURCE(DBR_CODE, module_name, stat);
 
  // cleanup
  reset_current_module_statement();
  reset_current_module_entity();
  return true;
}
 
#endif // BUILDER_FORCE_REGISTER_DECLARATIONS