gcc/:

[official-gcc.git] / gcc / ira.c

/* Integrated Register Allocator (IRA) entry point.
   Copyright (C) 2006, 2007, 2008, 2009
   Free Software Foundation, Inc.
   Contributed by Vladimir Makarov <vmakarov@redhat.com>.

This file is part of GCC.

GCC 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, or (at your option) any later
version.

GCC 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 GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

/* The integrated register allocator (IRA) is a
   regional register allocator performing graph coloring on a top-down
   traversal of nested regions.  Graph coloring in a region is based
   on Chaitin-Briggs algorithm.  It is called integrated because
   register coalescing, register live range splitting, and choosing a
   better hard register are done on-the-fly during coloring.  Register
   coalescing and choosing a cheaper hard register is done by hard
   register preferencing during hard register assigning.  The live
   range splitting is a byproduct of the regional register allocation.

   Major IRA notions are:

     o *Region* is a part of CFG where graph coloring based on
       Chaitin-Briggs algorithm is done.  IRA can work on any set of
       nested CFG regions forming a tree.  Currently the regions are
       the entire function for the root region and natural loops for
       the other regions.  Therefore data structure representing a
       region is called loop_tree_node.

     o *Cover class* is a register class belonging to a set of
       non-intersecting register classes containing all of the
       hard-registers available for register allocation.  The set of
       all cover classes for a target is defined in the corresponding
       machine-description file according some criteria.  Such notion
       is needed because Chaitin-Briggs algorithm works on
       non-intersected register classes.

     o *Allocno* represents the live range of a pseudo-register in a
       region.  Besides the obvious attributes like the corresponding
       pseudo-register number, cover class, conflicting allocnos and
       conflicting hard-registers, there are a few allocno attributes
       which are important for understanding the allocation algorithm:

       - *Live ranges*.  This is a list of ranges of *program
         points* where the allocno lives.  Program points represent
         places where a pseudo can be born or become dead (there are
         approximately two times more program points than the insns)
         and they are represented by integers starting with 0.  The
         live ranges are used to find conflicts between allocnos of
         different cover classes.  They also play very important role
         for the transformation of the IRA internal representation of
         several regions into a one region representation.  The later is
         used during the reload pass work because each allocno
         represents all of the corresponding pseudo-registers.

       - *Hard-register costs*.  This is a vector of size equal to the
         number of available hard-registers of the allocno's cover
         class.  The cost of a callee-clobbered hard-register for an
         allocno is increased by the cost of save/restore code around
         the calls through the given allocno's life.  If the allocno
         is a move instruction operand and another operand is a
         hard-register of the allocno's cover class, the cost of the
         hard-register is decreased by the move cost.

         When an allocno is assigned, the hard-register with minimal
         full cost is used.  Initially, a hard-register's full cost is
         the corresponding value from the hard-register's cost vector.
         If the allocno is connected by a *copy* (see below) to
         another allocno which has just received a hard-register, the
         cost of the hard-register is decreased.  Before choosing a
         hard-register for an allocno, the allocno's current costs of
         the hard-registers are modified by the conflict hard-register
         costs of all of the conflicting allocnos which are not
         assigned yet.

       - *Conflict hard-register costs*.  This is a vector of the same
         size as the hard-register costs vector.  To permit an
         unassigned allocno to get a better hard-register, IRA uses
         this vector to calculate the final full cost of the
         available hard-registers.  Conflict hard-register costs of an
         unassigned allocno are also changed with a change of the
         hard-register cost of the allocno when a copy involving the
         allocno is processed as described above.  This is done to
         show other unassigned allocnos that a given allocno prefers
         some hard-registers in order to remove the move instruction
         corresponding to the copy.

     o *Cap*.  If a pseudo-register does not live in a region but
       lives in a nested region, IRA creates a special allocno called
       a cap in the outer region.  A region cap is also created for a
       subregion cap.

     o *Copy*.  Allocnos can be connected by copies.  Copies are used
       to modify hard-register costs for allocnos during coloring.
       Such modifications reflects a preference to use the same
       hard-register for the allocnos connected by copies.  Usually
       copies are created for move insns (in this case it results in
       register coalescing).  But IRA also creates copies for operands
       of an insn which should be assigned to the same hard-register
       due to constraints in the machine description (it usually
       results in removing a move generated in reload to satisfy
       the constraints) and copies referring to the allocno which is
       the output operand of an instruction and the allocno which is
       an input operand dying in the instruction (creation of such
       copies results in less register shuffling).  IRA *does not*
       create copies between the same register allocnos from different
       regions because we use another technique for propagating
       hard-register preference on the borders of regions.

   Allocnos (including caps) for the upper region in the region tree
   *accumulate* information important for coloring from allocnos with
   the same pseudo-register from nested regions.  This includes
   hard-register and memory costs, conflicts with hard-registers,
   allocno conflicts, allocno copies and more.  *Thus, attributes for
   allocnos in a region have the same values as if the region had no
   subregions*.  It means that attributes for allocnos in the
   outermost region corresponding to the function have the same values
   as though the allocation used only one region which is the entire
   function.  It also means that we can look at IRA work as if the
   first IRA did allocation for all function then it improved the
   allocation for loops then their subloops and so on.

   IRA major passes are:

     o Building IRA internal representation which consists of the
       following subpasses:

       * First, IRA builds regions and creates allocnos (file
         ira-build.c) and initializes most of their attributes.

       * Then IRA finds a cover class for each allocno and calculates
         its initial (non-accumulated) cost of memory and each
         hard-register of its cover class (file ira-cost.c).

       * IRA creates live ranges of each allocno, calulates register
         pressure for each cover class in each region, sets up
         conflict hard registers for each allocno and info about calls
         the allocno lives through (file ira-lives.c).

       * IRA removes low register pressure loops from the regions
         mostly to speed IRA up (file ira-build.c).

       * IRA propagates accumulated allocno info from lower region
         allocnos to corresponding upper region allocnos (file
         ira-build.c).

       * IRA creates all caps (file ira-build.c).

       * Having live-ranges of allocnos and their cover classes, IRA
         creates conflicting allocnos of the same cover class for each
         allocno.  Conflicting allocnos are stored as a bit vector or
         array of pointers to the conflicting allocnos whatever is
         more profitable (file ira-conflicts.c).  At this point IRA
         creates allocno copies.

     o Coloring.  Now IRA has all necessary info to start graph coloring
       process.  It is done in each region on top-down traverse of the
       region tree (file ira-color.c).  There are following subpasses:
        
       * Optional aggressive coalescing of allocnos in the region.

       * Putting allocnos onto the coloring stack.  IRA uses Briggs
         optimistic coloring which is a major improvement over
         Chaitin's coloring.  Therefore IRA does not spill allocnos at
         this point.  There is some freedom in the order of putting
         allocnos on the stack which can affect the final result of
         the allocation.  IRA uses some heuristics to improve the order.

       * Popping the allocnos from the stack and assigning them hard
         registers.  If IRA can not assign a hard register to an
         allocno and the allocno is coalesced, IRA undoes the
         coalescing and puts the uncoalesced allocnos onto the stack in
         the hope that some such allocnos will get a hard register
         separately.  If IRA fails to assign hard register or memory
         is more profitable for it, IRA spills the allocno.  IRA
         assigns the allocno the hard-register with minimal full
         allocation cost which reflects the cost of usage of the
         hard-register for the allocno and cost of usage of the
         hard-register for allocnos conflicting with given allocno.

       * After allono assigning in the region, IRA modifies the hard
         register and memory costs for the corresponding allocnos in
         the subregions to reflect the cost of possible loads, stores,
         or moves on the border of the region and its subregions.
         When default regional allocation algorithm is used
         (-fira-algorithm=mixed), IRA just propagates the assignment
         for allocnos if the register pressure in the region for the
         corresponding cover class is less than number of available
         hard registers for given cover class.

     o Spill/restore code moving.  When IRA performs an allocation
       by traversing regions in top-down order, it does not know what
       happens below in the region tree.  Therefore, sometimes IRA
       misses opportunities to perform a better allocation.  A simple
       optimization tries to improve allocation in a region having
       subregions and containing in another region.  If the
       corresponding allocnos in the subregion are spilled, it spills
       the region allocno if it is profitable.  The optimization
       implements a simple iterative algorithm performing profitable
       transformations while they are still possible.  It is fast in
       practice, so there is no real need for a better time complexity
       algorithm.

     o Code change.  After coloring, two allocnos representing the same
       pseudo-register outside and inside a region respectively may be
       assigned to different locations (hard-registers or memory).  In
       this case IRA creates and uses a new pseudo-register inside the
       region and adds code to move allocno values on the region's
       borders.  This is done during top-down traversal of the regions
       (file ira-emit.c).  In some complicated cases IRA can create a
       new allocno to move allocno values (e.g. when a swap of values
       stored in two hard-registers is needed).  At this stage, the
       new allocno is marked as spilled.  IRA still creates the
       pseudo-register and the moves on the region borders even when
       both allocnos were assigned to the same hard-register.  If the
       reload pass spills a pseudo-register for some reason, the
       effect will be smaller because another allocno will still be in
       the hard-register.  In most cases, this is better then spilling
       both allocnos.  If reload does not change the allocation
       for the two pseudo-registers, the trivial move will be removed
       by post-reload optimizations.  IRA does not generate moves for
       allocnos assigned to the same hard register when the default
       regional allocation algorithm is used and the register pressure
       in the region for the corresponding allocno cover class is less
       than number of available hard registers for given cover class.
       IRA also does some optimizations to remove redundant stores and
       to reduce code duplication on the region borders.

     o Flattening internal representation.  After changing code, IRA
       transforms its internal representation for several regions into
       one region representation (file ira-build.c).  This process is
       called IR flattening.  Such process is more complicated than IR
       rebuilding would be, but is much faster.

     o After IR flattening, IRA tries to assign hard registers to all
       spilled allocnos.  This is impelemented by a simple and fast
       priority coloring algorithm (see function
       ira_reassign_conflict_allocnos::ira-color.c).  Here new allocnos
       created during the code change pass can be assigned to hard
       registers.

     o At the end IRA calls the reload pass.  The reload pass
       communicates with IRA through several functions in file
       ira-color.c to improve its decisions in

       * sharing stack slots for the spilled pseudos based on IRA info
         about pseudo-register conflicts.

       * reassigning hard-registers to all spilled pseudos at the end
         of each reload iteration.

       * choosing a better hard-register to spill based on IRA info
         about pseudo-register live ranges and the register pressure
         in places where the pseudo-register lives.

   IRA uses a lot of data representing the target processors.  These
   data are initilized in file ira.c.

   If function has no loops (or the loops are ignored when
   -fira-algorithm=CB is used), we have classic Chaitin-Briggs
   coloring (only instead of separate pass of coalescing, we use hard
   register preferencing).  In such case, IRA works much faster
   because many things are not made (like IR flattening, the
   spill/restore optimization, and the code change).

   Literature is worth to read for better understanding the code:

   o Preston Briggs, Keith D. Cooper, Linda Torczon.  Improvements to
     Graph Coloring Register Allocation.

   o David Callahan, Brian Koblenz.  Register allocation via
     hierarchical graph coloring.

   o Keith Cooper, Anshuman Dasgupta, Jason Eckhardt. Revisiting Graph
     Coloring Register Allocation: A Study of the Chaitin-Briggs and
     Callahan-Koblenz Algorithms.

   o Guei-Yuan Lueh, Thomas Gross, and Ali-Reza Adl-Tabatabai. Global
     Register Allocation Based on Graph Fusion.

   o Vladimir Makarov. The Integrated Register Allocator for GCC.

   o Vladimir Makarov.  The top-down register allocator for irregular
     register file architectures.

*/


#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "regs.h"
#include "rtl.h"
#include "tm_p.h"
#include "target.h"
#include "flags.h"
#include "obstack.h"
#include "bitmap.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "expr.h"
#include "recog.h"
#include "params.h"
#include "timevar.h"
#include "tree-pass.h"
#include "output.h"
#include "except.h"
#include "reload.h"
#include "errors.h"
#include "integrate.h"
#include "df.h"
#include "ggc.h"
#include "ira-int.h"


/* A modified value of flag `-fira-verbose' used internally.  */
int internal_flag_ira_verbose;

/* Dump file of the allocator if it is not NULL.  */
FILE *ira_dump_file;

/* Pools for allocnos, copies, allocno live ranges.  */
alloc_pool allocno_pool, copy_pool, allocno_live_range_pool;

/* The number of elements in the following array.  */
int ira_spilled_reg_stack_slots_num;

/* The following array contains info about spilled pseudo-registers
   stack slots used in current function so far.  */
struct ira_spilled_reg_stack_slot *ira_spilled_reg_stack_slots;

/* Correspondingly overall cost of the allocation, cost of the
   allocnos assigned to hard-registers, cost of the allocnos assigned
   to memory, cost of loads, stores and register move insns generated
   for pseudo-register live range splitting (see ira-emit.c).  */
int ira_overall_cost;
int ira_reg_cost, ira_mem_cost;
int ira_load_cost, ira_store_cost, ira_shuffle_cost;
int ira_move_loops_num, ira_additional_jumps_num;

/* All registers that can be eliminated.  */

HARD_REG_SET eliminable_regset;

/* Map: hard regs X modes -> set of hard registers for storing value
   of given mode starting with given hard register.  */
HARD_REG_SET ira_reg_mode_hard_regset[FIRST_PSEUDO_REGISTER][NUM_MACHINE_MODES];

/* The following two variables are array analogs of the macros
   MEMORY_MOVE_COST and REGISTER_MOVE_COST.  */
short int ira_memory_move_cost[MAX_MACHINE_MODE][N_REG_CLASSES][2];
move_table *ira_register_move_cost[MAX_MACHINE_MODE];

/* Similar to may_move_in_cost but it is calculated in IRA instead of
   regclass.  Another difference is that we take only available hard
   registers into account to figure out that one register class is a
   subset of the another one.  */
move_table *ira_may_move_in_cost[MAX_MACHINE_MODE];

/* Similar to may_move_out_cost but it is calculated in IRA instead of
   regclass.  Another difference is that we take only available hard
   registers into account to figure out that one register class is a
   subset of the another one.  */
move_table *ira_may_move_out_cost[MAX_MACHINE_MODE];

/* Register class subset relation: TRUE if the first class is a subset
   of the second one considering only hard registers available for the
   allocation.  */
int ira_class_subset_p[N_REG_CLASSES][N_REG_CLASSES];

/* Temporary hard reg set used for a different calculation.  */
static HARD_REG_SET temp_hard_regset;

\f

/* The function sets up the map IRA_REG_MODE_HARD_REGSET.  */
static void
setup_reg_mode_hard_regset (void)
{
  int i, m, hard_regno;

  for (m = 0; m < NUM_MACHINE_MODES; m++)
    for (hard_regno = 0; hard_regno < FIRST_PSEUDO_REGISTER; hard_regno++)
      {
        CLEAR_HARD_REG_SET (ira_reg_mode_hard_regset[hard_regno][m]);
        for (i = hard_regno_nregs[hard_regno][m] - 1; i >= 0; i--)
          if (hard_regno + i < FIRST_PSEUDO_REGISTER)
            SET_HARD_REG_BIT (ira_reg_mode_hard_regset[hard_regno][m],
                              hard_regno + i);
      }
}

\f

/* Hard registers that can not be used for the register allocator for
   all functions of the current compilation unit.  */
static HARD_REG_SET no_unit_alloc_regs;

/* Array of the number of hard registers of given class which are
   available for allocation.  The order is defined by the
   allocation order.  */
short ira_class_hard_regs[N_REG_CLASSES][FIRST_PSEUDO_REGISTER];

/* The number of elements of the above array for given register
   class.  */
int ira_class_hard_regs_num[N_REG_CLASSES];

/* Index (in ira_class_hard_regs) for given register class and hard
   register (in general case a hard register can belong to several
   register classes).  The index is negative for hard registers
   unavailable for the allocation. */
short ira_class_hard_reg_index[N_REG_CLASSES][FIRST_PSEUDO_REGISTER];

/* The function sets up the three arrays declared above.  */
static void
setup_class_hard_regs (void)
{
  int cl, i, hard_regno, n;
  HARD_REG_SET processed_hard_reg_set;

  ira_assert (SHRT_MAX >= FIRST_PSEUDO_REGISTER);
  /* We could call ORDER_REGS_FOR_LOCAL_ALLOC here (it is usually
     putting hard callee-used hard registers first).  But our
     heuristics work better.  */
  for (cl = (int) N_REG_CLASSES - 1; cl >= 0; cl--)
    {
      COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[cl]);
      AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
      CLEAR_HARD_REG_SET (processed_hard_reg_set);
      for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
        ira_class_hard_reg_index[cl][0] = -1;
      for (n = 0, i = 0; i < FIRST_PSEUDO_REGISTER; i++)
        {
#ifdef REG_ALLOC_ORDER
          hard_regno = reg_alloc_order[i];
#else
          hard_regno = i;
#endif    
          if (TEST_HARD_REG_BIT (processed_hard_reg_set, hard_regno))
            continue;
          SET_HARD_REG_BIT (processed_hard_reg_set, hard_regno);
          if (! TEST_HARD_REG_BIT (temp_hard_regset, hard_regno))
            ira_class_hard_reg_index[cl][hard_regno] = -1;
          else
            {
              ira_class_hard_reg_index[cl][hard_regno] = n;
              ira_class_hard_regs[cl][n++] = hard_regno;
            }
        }
      ira_class_hard_regs_num[cl] = n;
    }
}

/* Number of given class hard registers available for the register
   allocation for given classes.  */
int ira_available_class_regs[N_REG_CLASSES];

/* Set up IRA_AVAILABLE_CLASS_REGS.  */
static void
setup_available_class_regs (void)
{
  int i, j;

  memset (ira_available_class_regs, 0, sizeof (ira_available_class_regs));
  for (i = 0; i < N_REG_CLASSES; i++)
    {
      COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[i]);
      AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
      for (j = 0; j < FIRST_PSEUDO_REGISTER; j++)
        if (TEST_HARD_REG_BIT (temp_hard_regset, j))
          ira_available_class_regs[i]++;
    }
}

/* Set up global variables defining info about hard registers for the
   allocation.  These depend on USE_HARD_FRAME_P whose TRUE value means
   that we can use the hard frame pointer for the allocation.  */
static void
setup_alloc_regs (bool use_hard_frame_p)
{
  COPY_HARD_REG_SET (no_unit_alloc_regs, fixed_reg_set);
  if (! use_hard_frame_p)
    SET_HARD_REG_BIT (no_unit_alloc_regs, HARD_FRAME_POINTER_REGNUM);
  setup_class_hard_regs ();
  setup_available_class_regs ();
}

\f

/* Set up IRA_MEMORY_MOVE_COST, IRA_REGISTER_MOVE_COST.  */
static void
setup_class_subset_and_memory_move_costs (void)
{
  int cl, cl2;
  enum machine_mode mode;
  HARD_REG_SET temp_hard_regset2;

  for (mode = 0; mode < MAX_MACHINE_MODE; mode++)
    ira_memory_move_cost[mode][NO_REGS][0]
      = ira_memory_move_cost[mode][NO_REGS][1] = SHRT_MAX;
  for (cl = (int) N_REG_CLASSES - 1; cl >= 0; cl--)
    {
      if (cl != (int) NO_REGS)
        for (mode = 0; mode < MAX_MACHINE_MODE; mode++)
          {
            ira_memory_move_cost[mode][cl][0] =
              MEMORY_MOVE_COST (mode, (enum reg_class) cl, 0);
            ira_memory_move_cost[mode][cl][1] =
              MEMORY_MOVE_COST (mode, (enum reg_class) cl, 1);
            /* Costs for NO_REGS are used in cost calculation on the
               1st pass when the preferred register classes are not
               known yet.  In this case we take the best scenario.  */
            if (ira_memory_move_cost[mode][NO_REGS][0]
                > ira_memory_move_cost[mode][cl][0])
              ira_memory_move_cost[mode][NO_REGS][0]
                = ira_memory_move_cost[mode][cl][0];
            if (ira_memory_move_cost[mode][NO_REGS][1]
                > ira_memory_move_cost[mode][cl][1])
              ira_memory_move_cost[mode][NO_REGS][1]
                = ira_memory_move_cost[mode][cl][1];
          }
      for (cl2 = (int) N_REG_CLASSES - 1; cl2 >= 0; cl2--)
        {
          COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[cl]);
          AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
          COPY_HARD_REG_SET (temp_hard_regset2, reg_class_contents[cl2]);
          AND_COMPL_HARD_REG_SET (temp_hard_regset2, no_unit_alloc_regs);
          ira_class_subset_p[cl][cl2]
            = hard_reg_set_subset_p (temp_hard_regset, temp_hard_regset2);
        }
    }
}

\f

/* Define the following macro if allocation through malloc if
   preferable.  */
#define IRA_NO_OBSTACK

#ifndef IRA_NO_OBSTACK
/* Obstack used for storing all dynamic data (except bitmaps) of the
   IRA.  */
static struct obstack ira_obstack;
#endif

/* Obstack used for storing all bitmaps of the IRA.  */
static struct bitmap_obstack ira_bitmap_obstack;

/* Allocate memory of size LEN for IRA data.  */
void *
ira_allocate (size_t len)
{
  void *res;

#ifndef IRA_NO_OBSTACK
  res = obstack_alloc (&ira_obstack, len);
#else
  res = xmalloc (len);
#endif
  return res;
}

/* Reallocate memory PTR of size LEN for IRA data.  */
void *
ira_reallocate (void *ptr, size_t len)
{
  void *res;

#ifndef IRA_NO_OBSTACK
  res = obstack_alloc (&ira_obstack, len);
#else
  res = xrealloc (ptr, len);
#endif
  return res;
}

/* Free memory ADDR allocated for IRA data.  */
void
ira_free (void *addr ATTRIBUTE_UNUSED)
{
#ifndef IRA_NO_OBSTACK
  /* do nothing */
#else
  free (addr);
#endif
}


/* Allocate and returns bitmap for IRA.  */
bitmap
ira_allocate_bitmap (void)
{
  return BITMAP_ALLOC (&ira_bitmap_obstack);
}

/* Free bitmap B allocated for IRA.  */
void
ira_free_bitmap (bitmap b ATTRIBUTE_UNUSED)
{
  /* do nothing */
}

\f

/* Output information about allocation of all allocnos (except for
   caps) into file F.  */
void
ira_print_disposition (FILE *f)
{
  int i, n, max_regno;
  ira_allocno_t a;
  basic_block bb;

  fprintf (f, "Disposition:");
  max_regno = max_reg_num ();
  for (n = 0, i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
    for (a = ira_regno_allocno_map[i];
         a != NULL;
         a = ALLOCNO_NEXT_REGNO_ALLOCNO (a))
      {
        if (n % 4 == 0)
          fprintf (f, "\n");
        n++;
        fprintf (f, " %4d:r%-4d", ALLOCNO_NUM (a), ALLOCNO_REGNO (a));
        if ((bb = ALLOCNO_LOOP_TREE_NODE (a)->bb) != NULL)
          fprintf (f, "b%-3d", bb->index);
        else
          fprintf (f, "l%-3d", ALLOCNO_LOOP_TREE_NODE (a)->loop->num);
        if (ALLOCNO_HARD_REGNO (a) >= 0)
          fprintf (f, " %3d", ALLOCNO_HARD_REGNO (a));
        else
          fprintf (f, " mem");
      }
  fprintf (f, "\n");
}

/* Outputs information about allocation of all allocnos into
   stderr.  */
void
ira_debug_disposition (void)
{
  ira_print_disposition (stderr);
}

\f

/* For each reg class, table listing all the classes contained in it
   (excluding the class itself.  Non-allocatable registers are
   excluded from the consideration).  */
static enum reg_class alloc_reg_class_subclasses[N_REG_CLASSES][N_REG_CLASSES];

/* Initialize the table of subclasses of each reg class.  */
static void
setup_reg_subclasses (void)
{
  int i, j;
  HARD_REG_SET temp_hard_regset2;

  for (i = 0; i < N_REG_CLASSES; i++)
    for (j = 0; j < N_REG_CLASSES; j++)
      alloc_reg_class_subclasses[i][j] = LIM_REG_CLASSES;

  for (i = 0; i < N_REG_CLASSES; i++)
    {
      if (i == (int) NO_REGS)
        continue;

      COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[i]);
      AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
      if (hard_reg_set_empty_p (temp_hard_regset))
        continue;
      for (j = 0; j < N_REG_CLASSES; j++)
        if (i != j)
          {
            enum reg_class *p;

            COPY_HARD_REG_SET (temp_hard_regset2, reg_class_contents[j]);
            AND_COMPL_HARD_REG_SET (temp_hard_regset2, no_unit_alloc_regs);
            if (! hard_reg_set_subset_p (temp_hard_regset,
                                         temp_hard_regset2))
              continue;
            p = &alloc_reg_class_subclasses[j][0];
            while (*p != LIM_REG_CLASSES) p++;
            *p = (enum reg_class) i;
          }
    }
}

\f

/* Number of cover classes.  Cover classes is non-intersected register
   classes containing all hard-registers available for the
   allocation.  */
int ira_reg_class_cover_size;

/* The array containing cover classes (see also comments for macro
   IRA_COVER_CLASSES).  Only first IRA_REG_CLASS_COVER_SIZE elements are
   used for this.  */
enum reg_class ira_reg_class_cover[N_REG_CLASSES];

/* The number of elements in the subsequent array.  */
int ira_important_classes_num;

/* The array containing non-empty classes (including non-empty cover
   classes) which are subclasses of cover classes.  Such classes is
   important for calculation of the hard register usage costs.  */
enum reg_class ira_important_classes[N_REG_CLASSES];

/* The array containing indexes of important classes in the previous
   array.  The array elements are defined only for important
   classes.  */
int ira_important_class_nums[N_REG_CLASSES];

/* Set the four global variables defined above.  */
static void
setup_cover_and_important_classes (void)
{
  int i, j, n;
  bool set_p, eq_p;
  enum reg_class cl;
  const enum reg_class *cover_classes;
  HARD_REG_SET temp_hard_regset2;
  static enum reg_class classes[LIM_REG_CLASSES + 1];

  if (targetm.ira_cover_classes == NULL)
    cover_classes = NULL;
  else
    cover_classes = targetm.ira_cover_classes ();
  if (cover_classes == NULL)
    ira_assert (flag_ira_algorithm == IRA_ALGORITHM_PRIORITY);
  else
    {
      for (i = 0; (cl = cover_classes[i]) != LIM_REG_CLASSES; i++)
        classes[i] = cl;
      classes[i] = LIM_REG_CLASSES;
    }

  if (flag_ira_algorithm == IRA_ALGORITHM_PRIORITY)
    {
      n = 0;
      for (i = 0; i <= LIM_REG_CLASSES; i++)
        {
          if (i == NO_REGS)
            continue;
#ifdef CONSTRAINT__LIMIT
          for (j = 0; j < CONSTRAINT__LIMIT; j++)
            if ((int) regclass_for_constraint (j) == i)
              break;
          if (j < CONSTRAINT__LIMIT)
            {
              classes[n++] = i;
              continue;
            }
#endif
          COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[i]);
          AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
          for (j = 0; j < LIM_REG_CLASSES; j++)
            {
              if (i == j)
                continue;
              COPY_HARD_REG_SET (temp_hard_regset2, reg_class_contents[j]);
              AND_COMPL_HARD_REG_SET (temp_hard_regset2,
                                      no_unit_alloc_regs);
              if (hard_reg_set_equal_p (temp_hard_regset,
                                        temp_hard_regset2))
                    break;
            }
          if (j >= i)
            classes[n++] = i;
        }
      classes[n] = LIM_REG_CLASSES;
    }

  ira_reg_class_cover_size = 0;
  for (i = 0; (cl = classes[i]) != LIM_REG_CLASSES; i++)
    {
      for (j = 0; j < i; j++)
        if (flag_ira_algorithm != IRA_ALGORITHM_PRIORITY
            && reg_classes_intersect_p (cl, classes[j]))
          gcc_unreachable ();
      COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[cl]);
      AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
      if (! hard_reg_set_empty_p (temp_hard_regset))
        ira_reg_class_cover[ira_reg_class_cover_size++] = cl;
    }
  ira_important_classes_num = 0;
  for (cl = 0; cl < N_REG_CLASSES; cl++)
    {
      COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[cl]);
      AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
      if (! hard_reg_set_empty_p (temp_hard_regset))
        {
          set_p = eq_p = false;
          for (j = 0; j < ira_reg_class_cover_size; j++)
            {
              COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[cl]);
              AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
              COPY_HARD_REG_SET (temp_hard_regset2,
                                 reg_class_contents[ira_reg_class_cover[j]]);
              AND_COMPL_HARD_REG_SET (temp_hard_regset2, no_unit_alloc_regs);
              if (cl == ira_reg_class_cover[j])
                {
                  eq_p = false;
                  set_p = true;
                  break;
                }
              else if (hard_reg_set_equal_p (temp_hard_regset,
                                             temp_hard_regset2))
                eq_p = true;
              else if (hard_reg_set_subset_p (temp_hard_regset,
                                              temp_hard_regset2))
                set_p = true;
            }
          if (set_p && ! eq_p)
            {
              ira_important_class_nums[cl] = ira_important_classes_num;
              ira_important_classes[ira_important_classes_num++] = cl;
            }
        }
    }
}

/* Map of all register classes to corresponding cover class containing
   the given class.  If given class is not a subset of a cover class,
   we translate it into the cheapest cover class.  */
enum reg_class ira_class_translate[N_REG_CLASSES];

/* Set up array IRA_CLASS_TRANSLATE.  */
static void
setup_class_translate (void)
{
  enum reg_class cl, cover_class, best_class, *cl_ptr;
  enum machine_mode mode;
  int i, cost, min_cost, best_cost;

  for (cl = 0; cl < N_REG_CLASSES; cl++)
    ira_class_translate[cl] = NO_REGS;
  
  if (flag_ira_algorithm == IRA_ALGORITHM_PRIORITY)
    for (cl = 0; cl < LIM_REG_CLASSES; cl++)
      {
        COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[cl]);
        AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
        for (i = 0; i < ira_reg_class_cover_size; i++)
          {
            HARD_REG_SET temp_hard_regset2;
            
            cover_class = ira_reg_class_cover[i];
            COPY_HARD_REG_SET (temp_hard_regset2,
                               reg_class_contents[cover_class]);
            AND_COMPL_HARD_REG_SET (temp_hard_regset2, no_unit_alloc_regs);
            if (hard_reg_set_equal_p (temp_hard_regset, temp_hard_regset2))
              ira_class_translate[cl] = cover_class;
          }
      }
  for (i = 0; i < ira_reg_class_cover_size; i++)
    {
      cover_class = ira_reg_class_cover[i];
      if (flag_ira_algorithm != IRA_ALGORITHM_PRIORITY)
        for (cl_ptr = &alloc_reg_class_subclasses[cover_class][0];
             (cl = *cl_ptr) != LIM_REG_CLASSES;
             cl_ptr++)
          {
            if (ira_class_translate[cl] == NO_REGS)
              ira_class_translate[cl] = cover_class;
#ifdef ENABLE_IRA_CHECKING
            else
              {
                COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[cl]);
                AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
                if (! hard_reg_set_empty_p (temp_hard_regset))
                  gcc_unreachable ();
              }
#endif
          }
      ira_class_translate[cover_class] = cover_class;
    }
  /* For classes which are not fully covered by a cover class (in
     other words covered by more one cover class), use the cheapest
     cover class.  */
  for (cl = 0; cl < N_REG_CLASSES; cl++)
    {
      if (cl == NO_REGS || ira_class_translate[cl] != NO_REGS)
        continue;
      best_class = NO_REGS;
      best_cost = INT_MAX;
      for (i = 0; i < ira_reg_class_cover_size; i++)
        {
          cover_class = ira_reg_class_cover[i];
          COPY_HARD_REG_SET (temp_hard_regset,
                             reg_class_contents[cover_class]);
          AND_HARD_REG_SET (temp_hard_regset, reg_class_contents[cl]);
          AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
          if (! hard_reg_set_empty_p (temp_hard_regset))
            {
              min_cost = INT_MAX;
              for (mode = 0; mode < MAX_MACHINE_MODE; mode++)
                {
                  cost = (ira_memory_move_cost[mode][cl][0]
                          + ira_memory_move_cost[mode][cl][1]);
                  if (min_cost > cost)
                    min_cost = cost;
                }
              if (best_class == NO_REGS || best_cost > min_cost)
                {
                  best_class = cover_class;
                  best_cost = min_cost;
                }
            }
        }
      ira_class_translate[cl] = best_class;
    }
}

/* The biggest important reg_class inside of intersection of the two
   reg_classes (that is calculated taking only hard registers
   available for allocation into account).  If the both reg_classes
   contain no hard registers available for allocation, the value is
   calculated by taking all hard-registers including fixed ones into
   account.  */
enum reg_class ira_reg_class_intersect[N_REG_CLASSES][N_REG_CLASSES];

/* True if the two classes (that is calculated taking only hard
   registers available for allocation into account) are
   intersected.  */
bool ira_reg_classes_intersect_p[N_REG_CLASSES][N_REG_CLASSES];

/* Important classes with end marker LIM_REG_CLASSES which are
   supersets with given important class (the first index).  That
   includes given class itself.  This is calculated taking only hard
   registers available for allocation into account.  */
enum reg_class ira_reg_class_super_classes[N_REG_CLASSES][N_REG_CLASSES];

/* The biggest important reg_class inside of union of the two
   reg_classes (that is calculated taking only hard registers
   available for allocation into account).  If the both reg_classes
   contain no hard registers available for allocation, the value is
   calculated by taking all hard-registers including fixed ones into
   account.  In other words, the value is the corresponding
   reg_class_subunion value.  */
enum reg_class ira_reg_class_union[N_REG_CLASSES][N_REG_CLASSES];

/* Set up the above reg class relations.  */
static void
setup_reg_class_relations (void)
{
  int i, cl1, cl2, cl3;
  HARD_REG_SET intersection_set, union_set, temp_set2;
  bool important_class_p[N_REG_CLASSES];

  memset (important_class_p, 0, sizeof (important_class_p));
  for (i = 0; i < ira_important_classes_num; i++)
    important_class_p[ira_important_classes[i]] = true;
  for (cl1 = 0; cl1 < N_REG_CLASSES; cl1++)
    {
      ira_reg_class_super_classes[cl1][0] = LIM_REG_CLASSES;
      for (cl2 = 0; cl2 < N_REG_CLASSES; cl2++)
        {
          ira_reg_classes_intersect_p[cl1][cl2] = false;
          ira_reg_class_intersect[cl1][cl2] = NO_REGS;
          COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[cl1]);
          AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
          COPY_HARD_REG_SET (temp_set2, reg_class_contents[cl2]);
          AND_COMPL_HARD_REG_SET (temp_set2, no_unit_alloc_regs);
          if (hard_reg_set_empty_p (temp_hard_regset)
              && hard_reg_set_empty_p (temp_set2))
            {
              for (i = 0;; i++)
                {
                  cl3 = reg_class_subclasses[cl1][i];
                  if (cl3 == LIM_REG_CLASSES)
                    break;
                  if (reg_class_subset_p (ira_reg_class_intersect[cl1][cl2],
                                          (enum reg_class) cl3))
                    ira_reg_class_intersect[cl1][cl2] = (enum reg_class) cl3;
                }
              ira_reg_class_union[cl1][cl2] = reg_class_subunion[cl1][cl2];
              continue;
            }
          ira_reg_classes_intersect_p[cl1][cl2]
            = hard_reg_set_intersect_p (temp_hard_regset, temp_set2);
          if (important_class_p[cl1] && important_class_p[cl2]
              && hard_reg_set_subset_p (temp_hard_regset, temp_set2))
            {
              enum reg_class *p;

              p = &ira_reg_class_super_classes[cl1][0];
              while (*p != LIM_REG_CLASSES)
                p++;
              *p++ = (enum reg_class) cl2;
              *p = LIM_REG_CLASSES;
            }
          ira_reg_class_union[cl1][cl2] = NO_REGS;
          COPY_HARD_REG_SET (intersection_set, reg_class_contents[cl1]);
          AND_HARD_REG_SET (intersection_set, reg_class_contents[cl2]);
          AND_COMPL_HARD_REG_SET (intersection_set, no_unit_alloc_regs);
          COPY_HARD_REG_SET (union_set, reg_class_contents[cl1]);
          IOR_HARD_REG_SET (union_set, reg_class_contents[cl2]);
          AND_COMPL_HARD_REG_SET (union_set, no_unit_alloc_regs);
          for (i = 0; i < ira_important_classes_num; i++)
            {
              cl3 = ira_important_classes[i];
              COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[cl3]);
              AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
              if (hard_reg_set_subset_p (temp_hard_regset, intersection_set))
                {
                  COPY_HARD_REG_SET
                    (temp_set2,
                     reg_class_contents[(int)
                                        ira_reg_class_intersect[cl1][cl2]]);
                  AND_COMPL_HARD_REG_SET (temp_set2, no_unit_alloc_regs);
                  if (! hard_reg_set_subset_p (temp_hard_regset, temp_set2)
                      /* Ignore unavailable hard registers and prefer
                         smallest class for debugging purposes.  */
                      || (hard_reg_set_equal_p (temp_hard_regset, temp_set2)
                          && hard_reg_set_subset_p
                             (reg_class_contents[cl3],
                              reg_class_contents
                              [(int) ira_reg_class_intersect[cl1][cl2]])))
                    ira_reg_class_intersect[cl1][cl2] = (enum reg_class) cl3;
                }
              if (hard_reg_set_subset_p (temp_hard_regset, union_set))
                {
                  COPY_HARD_REG_SET
                    (temp_set2,
                     reg_class_contents[(int) ira_reg_class_union[cl1][cl2]]);
                  AND_COMPL_HARD_REG_SET (temp_set2, no_unit_alloc_regs);
                  if (ira_reg_class_union[cl1][cl2] == NO_REGS
                      || (hard_reg_set_subset_p (temp_set2, temp_hard_regset)
                      
                          && (! hard_reg_set_equal_p (temp_set2,
                                                      temp_hard_regset)
                              /* Ignore unavailable hard registers and
                                 prefer smallest class for debugging
                                 purposes.  */
                              || hard_reg_set_subset_p
                                 (reg_class_contents[cl3],
                                  reg_class_contents
                                  [(int) ira_reg_class_union[cl1][cl2]]))))
                    ira_reg_class_union[cl1][cl2] = (enum reg_class) cl3;
                }
            }
        }
    }
}

/* Output all cover classes and the translation map into file F.  */
static void
print_class_cover (FILE *f)
{
  static const char *const reg_class_names[] = REG_CLASS_NAMES;
  int i;

  fprintf (f, "Class cover:\n");
  for (i = 0; i < ira_reg_class_cover_size; i++)
    fprintf (f, " %s", reg_class_names[ira_reg_class_cover[i]]);
  fprintf (f, "\nClass translation:\n");
  for (i = 0; i < N_REG_CLASSES; i++)
    fprintf (f, " %s -> %s\n", reg_class_names[i],
             reg_class_names[ira_class_translate[i]]);
}

/* Output all cover classes and the translation map into
   stderr.  */
void
ira_debug_class_cover (void)
{
  print_class_cover (stderr);
}

/* Set up different arrays concerning class subsets, cover and
   important classes.  */
static void
find_reg_class_closure (void)
{
  setup_reg_subclasses ();
  setup_cover_and_important_classes ();
  setup_class_translate ();
  setup_reg_class_relations ();
}

\f

/* Map: hard register number -> cover class it belongs to.  If the
   corresponding class is NO_REGS, the hard register is not available
   for allocation.  */
enum reg_class ira_hard_regno_cover_class[FIRST_PSEUDO_REGISTER];

/* Set up the array above.  */
static void
setup_hard_regno_cover_class (void)
{
  int i, j;
  enum reg_class cl;

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
    {
      ira_hard_regno_cover_class[i] = NO_REGS;
      for (j = 0; j < ira_reg_class_cover_size; j++)
        {
          cl = ira_reg_class_cover[j];
          if (ira_class_hard_reg_index[cl][i] >= 0)
            {
              ira_hard_regno_cover_class[i] = cl;
              break;
            }
        }
            
    }
}

\f

/* Map: register class x machine mode -> number of hard registers of
   given class needed to store value of given mode.  If the number is
   different, the size will be negative.  */
int ira_reg_class_nregs[N_REG_CLASSES][MAX_MACHINE_MODE];

/* Maximal value of the previous array elements.  */
int ira_max_nregs;

/* Form IRA_REG_CLASS_NREGS map.  */
static void
setup_reg_class_nregs (void)
{
  int cl, m;

  ira_max_nregs = -1;
  for (cl = 0; cl < N_REG_CLASSES; cl++)
    for (m = 0; m < MAX_MACHINE_MODE; m++)
      {
        ira_reg_class_nregs[cl][m] = CLASS_MAX_NREGS ((enum reg_class) cl,
                                                      (enum machine_mode) m);
        if (ira_max_nregs < ira_reg_class_nregs[cl][m])
          ira_max_nregs = ira_reg_class_nregs[cl][m];
      }
}

\f

/* Array whose values are hard regset of hard registers available for
   the allocation of given register class whose HARD_REGNO_MODE_OK
   values for given mode are zero.  */
HARD_REG_SET prohibited_class_mode_regs[N_REG_CLASSES][NUM_MACHINE_MODES];

/* Set up PROHIBITED_CLASS_MODE_REGS.  */
static void
setup_prohibited_class_mode_regs (void)
{
  int i, j, k, hard_regno;
  enum reg_class cl;

  for (i = 0; i < ira_reg_class_cover_size; i++)
    {
      cl = ira_reg_class_cover[i];
      for (j = 0; j < NUM_MACHINE_MODES; j++)
        {
          CLEAR_HARD_REG_SET (prohibited_class_mode_regs[cl][j]);
          for (k = ira_class_hard_regs_num[cl] - 1; k >= 0; k--)
            {
              hard_regno = ira_class_hard_regs[cl][k];
              if (! HARD_REGNO_MODE_OK (hard_regno, (enum machine_mode) j))
                SET_HARD_REG_BIT (prohibited_class_mode_regs[cl][j],
                                  hard_regno);
            }
        }
    }
}

\f

/* Allocate and initialize IRA_REGISTER_MOVE_COST,
   IRA_MAY_MOVE_IN_COST, and IRA_MAY_MOVE_OUT_COST for MODE if it is
   not done yet.  */
void
ira_init_register_move_cost (enum machine_mode mode)
{
  int cl1, cl2;

  ira_assert (ira_register_move_cost[mode] == NULL
              && ira_may_move_in_cost[mode] == NULL
              && ira_may_move_out_cost[mode] == NULL);
  if (move_cost[mode] == NULL)
    init_move_cost (mode);
  ira_register_move_cost[mode] = move_cost[mode];
  /* Don't use ira_allocate because the tables exist out of scope of a
     IRA call.  */
  ira_may_move_in_cost[mode]
    = (move_table *) xmalloc (sizeof (move_table) * N_REG_CLASSES);
  memcpy (ira_may_move_in_cost[mode], may_move_in_cost[mode],
          sizeof (move_table) * N_REG_CLASSES);
  ira_may_move_out_cost[mode]
    = (move_table *) xmalloc (sizeof (move_table) * N_REG_CLASSES);
  memcpy (ira_may_move_out_cost[mode], may_move_out_cost[mode],
          sizeof (move_table) * N_REG_CLASSES);
  for (cl1 = 0; cl1 < N_REG_CLASSES; cl1++)
    {
      for (cl2 = 0; cl2 < N_REG_CLASSES; cl2++)
        {
          if (ira_class_subset_p[cl1][cl2])
            ira_may_move_in_cost[mode][cl1][cl2] = 0;
          if (ira_class_subset_p[cl2][cl1])
            ira_may_move_out_cost[mode][cl1][cl2] = 0;
        }
    }
}

\f

/* This is called once during compiler work.  It sets up
   different arrays whose values don't depend on the compiled
   function.  */
void
ira_init_once (void)
{
  enum machine_mode mode;

  for (mode = 0; mode < MAX_MACHINE_MODE; mode++)
    {
      ira_register_move_cost[mode] = NULL;
      ira_may_move_in_cost[mode] = NULL;
      ira_may_move_out_cost[mode] = NULL;
    }
  ira_init_costs_once ();
}

/* Free ira_register_move_cost, ira_may_move_in_cost, and
   ira_may_move_out_cost for each mode.  */
static void
free_register_move_costs (void)
{
  enum machine_mode mode;

  for (mode = 0; mode < MAX_MACHINE_MODE; mode++)
    {
      if (ira_may_move_in_cost[mode] != NULL)
        free (ira_may_move_in_cost[mode]);
      if (ira_may_move_out_cost[mode] != NULL)
        free (ira_may_move_out_cost[mode]);
      ira_register_move_cost[mode] = NULL;
      ira_may_move_in_cost[mode] = NULL;
      ira_may_move_out_cost[mode] = NULL;
    }
}

/* This is called every time when register related information is
   changed.  */
void
ira_init (void)
{
  free_register_move_costs ();
  setup_reg_mode_hard_regset ();
  setup_alloc_regs (flag_omit_frame_pointer != 0);
  setup_class_subset_and_memory_move_costs ();
  find_reg_class_closure ();
  setup_hard_regno_cover_class ();
  setup_reg_class_nregs ();
  setup_prohibited_class_mode_regs ();
  ira_init_costs ();
}

/* Function called once at the end of compiler work.  */
void
ira_finish_once (void)
{
  ira_finish_costs_once ();
  free_register_move_costs ();
}

\f

/* Array whose values are hard regset of hard registers for which
   move of the hard register in given mode into itself is
   prohibited.  */
HARD_REG_SET ira_prohibited_mode_move_regs[NUM_MACHINE_MODES];

/* Flag of that the above array has been initialized.  */
static bool ira_prohibited_mode_move_regs_initialized_p = false;

/* Set up IRA_PROHIBITED_MODE_MOVE_REGS.  */
static void
setup_prohibited_mode_move_regs (void)
{
  int i, j;
  rtx test_reg1, test_reg2, move_pat, move_insn;

  if (ira_prohibited_mode_move_regs_initialized_p)
    return;
  ira_prohibited_mode_move_regs_initialized_p = true;
  test_reg1 = gen_rtx_REG (VOIDmode, 0);
  test_reg2 = gen_rtx_REG (VOIDmode, 0);
  move_pat = gen_rtx_SET (VOIDmode, test_reg1, test_reg2);
  move_insn = gen_rtx_INSN (VOIDmode, 0, 0, 0, 0, 0, move_pat, -1, 0);
  for (i = 0; i < NUM_MACHINE_MODES; i++)
    {
      SET_HARD_REG_SET (ira_prohibited_mode_move_regs[i]);
      for (j = 0; j < FIRST_PSEUDO_REGISTER; j++)
        {
          if (! HARD_REGNO_MODE_OK (j, (enum machine_mode) i))
            continue;
          SET_REGNO (test_reg1, j);
          PUT_MODE (test_reg1, i);
          SET_REGNO (test_reg2, j);
          PUT_MODE (test_reg2, i);
          INSN_CODE (move_insn) = -1;
          recog_memoized (move_insn);
          if (INSN_CODE (move_insn) < 0)
            continue;
          extract_insn (move_insn);
          if (! constrain_operands (1))
            continue;
          CLEAR_HARD_REG_BIT (ira_prohibited_mode_move_regs[i], j);
        }
    }
}

\f

/* Function specific hard registers that can not be used for the
   register allocation.  */
HARD_REG_SET ira_no_alloc_regs;

/* Return TRUE if *LOC contains an asm.  */
static int
insn_contains_asm_1 (rtx *loc, void *data ATTRIBUTE_UNUSED)
{
  if ( !*loc)
    return FALSE;
  if (GET_CODE (*loc) == ASM_OPERANDS)
    return TRUE;
  return FALSE;
}


/* Return TRUE if INSN contains an ASM.  */
static bool
insn_contains_asm (rtx insn)
{
  return for_each_rtx (&insn, insn_contains_asm_1, NULL);
}

/* Set up regs_asm_clobbered.  */
static void
compute_regs_asm_clobbered (char *regs_asm_clobbered)
{
  basic_block bb;

  memset (regs_asm_clobbered, 0, sizeof (char) * FIRST_PSEUDO_REGISTER);
  
  FOR_EACH_BB (bb)
    {
      rtx insn;
      FOR_BB_INSNS_REVERSE (bb, insn)
        {
          df_ref *def_rec;

          if (insn_contains_asm (insn))
            for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
              {
                df_ref def = *def_rec;
                unsigned int dregno = DF_REF_REGNO (def);
                if (dregno < FIRST_PSEUDO_REGISTER)
                  {
                    unsigned int i;
                    enum machine_mode mode = GET_MODE (DF_REF_REAL_REG (def));
                    unsigned int end = dregno 
                      + hard_regno_nregs[dregno][mode] - 1;

                    for (i = dregno; i <= end; ++i)
                      regs_asm_clobbered[i] = 1;
                  }
              }
        }
    }
}


/* Set up ELIMINABLE_REGSET, IRA_NO_ALLOC_REGS, and REGS_EVER_LIVE.  */
static void
setup_eliminable_regset (void)
{
  /* Like regs_ever_live, but 1 if a reg is set or clobbered from an
     asm.  Unlike regs_ever_live, elements of this array corresponding
     to eliminable regs (like the frame pointer) are set if an asm
     sets them.  */
  char *regs_asm_clobbered
    = (char *) alloca (FIRST_PSEUDO_REGISTER * sizeof (char));
#ifdef ELIMINABLE_REGS
  int i;
  static const struct {const int from, to; } eliminables[] = ELIMINABLE_REGS;
#endif
  /* FIXME: If EXIT_IGNORE_STACK is set, we will not save and restore
     sp for alloca.  So we can't eliminate the frame pointer in that
     case.  At some point, we should improve this by emitting the
     sp-adjusting insns for this case.  */
  int need_fp
    = (! flag_omit_frame_pointer
       || (cfun->calls_alloca && EXIT_IGNORE_STACK)
       || crtl->accesses_prior_frames
       || crtl->stack_realign_needed
       || FRAME_POINTER_REQUIRED);

  frame_pointer_needed = need_fp;

  COPY_HARD_REG_SET (ira_no_alloc_regs, no_unit_alloc_regs);
  CLEAR_HARD_REG_SET (eliminable_regset);

  compute_regs_asm_clobbered (regs_asm_clobbered);
  /* Build the regset of all eliminable registers and show we can't
     use those that we already know won't be eliminated.  */
#ifdef ELIMINABLE_REGS
  for (i = 0; i < (int) ARRAY_SIZE (eliminables); i++)
    {
      bool cannot_elim
        = (! CAN_ELIMINATE (eliminables[i].from, eliminables[i].to)
           || (eliminables[i].to == STACK_POINTER_REGNUM && need_fp));

      if (! regs_asm_clobbered[eliminables[i].from])
        {
            SET_HARD_REG_BIT (eliminable_regset, eliminables[i].from);

            if (cannot_elim)
              SET_HARD_REG_BIT (ira_no_alloc_regs, eliminables[i].from);
        }
      else if (cannot_elim)
        error ("%s cannot be used in asm here",
               reg_names[eliminables[i].from]);
      else
        df_set_regs_ever_live (eliminables[i].from, true);
    }
#if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
  if (! regs_asm_clobbered[HARD_FRAME_POINTER_REGNUM])
    {
      SET_HARD_REG_BIT (eliminable_regset, HARD_FRAME_POINTER_REGNUM);
      if (need_fp)
        SET_HARD_REG_BIT (ira_no_alloc_regs, HARD_FRAME_POINTER_REGNUM);
    }
  else if (need_fp)
    error ("%s cannot be used in asm here",
           reg_names[HARD_FRAME_POINTER_REGNUM]);
  else
    df_set_regs_ever_live (HARD_FRAME_POINTER_REGNUM, true);
#endif

#else
  if (! regs_asm_clobbered[FRAME_POINTER_REGNUM])
    {
      SET_HARD_REG_BIT (eliminable_regset, FRAME_POINTER_REGNUM);
      if (need_fp)
        SET_HARD_REG_BIT (ira_no_alloc_regs, FRAME_POINTER_REGNUM);
    }
  else if (need_fp)
    error ("%s cannot be used in asm here", reg_names[FRAME_POINTER_REGNUM]);
  else
    df_set_regs_ever_live (FRAME_POINTER_REGNUM, true);
#endif
}

\f

/* The length of the following two arrays.  */
int ira_reg_equiv_len;

/* The element value is TRUE if the corresponding regno value is
   invariant.  */
bool *ira_reg_equiv_invariant_p;

/* The element value is equiv constant of given pseudo-register or
   NULL_RTX.  */
rtx *ira_reg_equiv_const;

/* Set up the two arrays declared above.  */
static void
find_reg_equiv_invariant_const (void)
{
  int i;
  bool invariant_p;
  rtx list, insn, note, constant, x;

  for (i = FIRST_PSEUDO_REGISTER; i < reg_equiv_init_size; i++)
    {
      constant = NULL_RTX;
      invariant_p = false;
      for (list = reg_equiv_init[i]; list != NULL_RTX; list = XEXP (list, 1))
        {
          insn = XEXP (list, 0);
          note = find_reg_note (insn, REG_EQUIV, NULL_RTX);
          
          if (note == NULL_RTX)
            continue;

          x = XEXP (note, 0);
          
          if (! function_invariant_p (x)
              || ! flag_pic
              /* A function invariant is often CONSTANT_P but may
                 include a register.  We promise to only pass CONSTANT_P
                 objects to LEGITIMATE_PIC_OPERAND_P.  */
              || (CONSTANT_P (x) && LEGITIMATE_PIC_OPERAND_P (x)))
            {
              /* It can happen that a REG_EQUIV note contains a MEM
                 that is not a legitimate memory operand.  As later
                 stages of the reload assume that all addresses found
                 in the reg_equiv_* arrays were originally legitimate,
                 we ignore such REG_EQUIV notes.  */
              if (memory_operand (x, VOIDmode))
                invariant_p = MEM_READONLY_P (x);
              else if (function_invariant_p (x))
                {
                  if (GET_CODE (x) == PLUS
                      || x == frame_pointer_rtx || x == arg_pointer_rtx)
                    invariant_p = true;
                  else
                    constant = x;
                }
            }
        }
      ira_reg_equiv_invariant_p[i] = invariant_p;
      ira_reg_equiv_const[i] = constant;
    }
}

\f

/* Vector of substitutions of register numbers,
   used to map pseudo regs into hardware regs.
   This is set up as a result of register allocation.
   Element N is the hard reg assigned to pseudo reg N,
   or is -1 if no hard reg was assigned.
   If N is a hard reg number, element N is N.  */
short *reg_renumber;

/* Set up REG_RENUMBER and CALLER_SAVE_NEEDED (used by reload) from
   the allocation found by IRA.  */
static void
setup_reg_renumber (void)
{
  int regno, hard_regno;
  ira_allocno_t a;
  ira_allocno_iterator ai;

  caller_save_needed = 0;
  FOR_EACH_ALLOCNO (a, ai)
    {
      /* There are no caps at this point.  */
      ira_assert (ALLOCNO_CAP_MEMBER (a) == NULL);
      if (! ALLOCNO_ASSIGNED_P (a))
        /* It can happen if A is not referenced but partially anticipated
           somewhere in a region.  */
        ALLOCNO_ASSIGNED_P (a) = true;
      ira_free_allocno_updated_costs (a);
      hard_regno = ALLOCNO_HARD_REGNO (a);
      regno = (int) REGNO (ALLOCNO_REG (a));
      reg_renumber[regno] = (hard_regno < 0 ? -1 : hard_regno);
      if (hard_regno >= 0 && ALLOCNO_CALLS_CROSSED_NUM (a) != 0
          && ! ira_hard_reg_not_in_set_p (hard_regno, ALLOCNO_MODE (a),
                                          call_used_reg_set))
        {
          ira_assert (!optimize || flag_caller_saves
                      || regno >= ira_reg_equiv_len
                      || ira_reg_equiv_const[regno]
                      || ira_reg_equiv_invariant_p[regno]);
          caller_save_needed = 1;
        }
    }
}

/* Set up allocno assignment flags for further allocation
   improvements.  */
static void
setup_allocno_assignment_flags (void)
{
  int hard_regno;
  ira_allocno_t a;
  ira_allocno_iterator ai;

  FOR_EACH_ALLOCNO (a, ai)
    {
      if (! ALLOCNO_ASSIGNED_P (a))
        /* It can happen if A is not referenced but partially anticipated
           somewhere in a region.  */
        ira_free_allocno_updated_costs (a);
      hard_regno = ALLOCNO_HARD_REGNO (a);
      /* Don't assign hard registers to allocnos which are destination
         of removed store at the end of loop.  It has no sense to keep
         the same value in different hard registers.  It is also
         impossible to assign hard registers correctly to such
         allocnos because the cost info and info about intersected
         calls are incorrect for them.  */
      ALLOCNO_ASSIGNED_P (a) = (hard_regno >= 0
                                || ALLOCNO_MEM_OPTIMIZED_DEST_P (a)
                                || (ALLOCNO_MEMORY_COST (a)
                                    - ALLOCNO_COVER_CLASS_COST (a)) < 0);
      ira_assert (hard_regno < 0
                  || ! ira_hard_reg_not_in_set_p (hard_regno, ALLOCNO_MODE (a),
                                                  reg_class_contents
                                                  [ALLOCNO_COVER_CLASS (a)]));
    }
}

/* Evaluate overall allocation cost and the costs for using hard
   registers and memory for allocnos.  */
static void
calculate_allocation_cost (void)
{
  int hard_regno, cost;
  ira_allocno_t a;
  ira_allocno_iterator ai;

  ira_overall_cost = ira_reg_cost = ira_mem_cost = 0;
  FOR_EACH_ALLOCNO (a, ai)
    {
      hard_regno = ALLOCNO_HARD_REGNO (a);
      ira_assert (hard_regno < 0
                  || ! ira_hard_reg_not_in_set_p
                       (hard_regno, ALLOCNO_MODE (a),
                        reg_class_contents[ALLOCNO_COVER_CLASS (a)])); 
      if (hard_regno < 0)
        {
          cost = ALLOCNO_MEMORY_COST (a);
          ira_mem_cost += cost;
        }
      else if (ALLOCNO_HARD_REG_COSTS (a) != NULL)
        {
          cost = (ALLOCNO_HARD_REG_COSTS (a)
                  [ira_class_hard_reg_index
                   [ALLOCNO_COVER_CLASS (a)][hard_regno]]);
          ira_reg_cost += cost;
        }
      else
        {
          cost = ALLOCNO_COVER_CLASS_COST (a);
          ira_reg_cost += cost;
        }
      ira_overall_cost += cost;
    }

  if (internal_flag_ira_verbose > 0 && ira_dump_file != NULL)
    {
      fprintf (ira_dump_file,
               "+++Costs: overall %d, reg %d, mem %d, ld %d, st %d, move %d\n",
               ira_overall_cost, ira_reg_cost, ira_mem_cost,
               ira_load_cost, ira_store_cost, ira_shuffle_cost);
      fprintf (ira_dump_file, "+++       move loops %d, new jumps %d\n",
               ira_move_loops_num, ira_additional_jumps_num);
    }

}

#ifdef ENABLE_IRA_CHECKING
/* Check the correctness of the allocation.  We do need this because
   of complicated code to transform more one region internal
   representation into one region representation.  */
static void
check_allocation (void)
{
  ira_allocno_t a, conflict_a;
  int hard_regno, conflict_hard_regno, nregs, conflict_nregs;
  ira_allocno_conflict_iterator aci;
  ira_allocno_iterator ai;

  FOR_EACH_ALLOCNO (a, ai)
    {
      if (ALLOCNO_CAP_MEMBER (a) != NULL
          || (hard_regno = ALLOCNO_HARD_REGNO (a)) < 0)
        continue;
      nregs = hard_regno_nregs[hard_regno][ALLOCNO_MODE (a)];
      FOR_EACH_ALLOCNO_CONFLICT (a, conflict_a, aci)
        if ((conflict_hard_regno = ALLOCNO_HARD_REGNO (conflict_a)) >= 0)
          {
            conflict_nregs
              = (hard_regno_nregs
                 [conflict_hard_regno][ALLOCNO_MODE (conflict_a)]);
            if ((conflict_hard_regno <= hard_regno
                 && hard_regno < conflict_hard_regno + conflict_nregs)
                || (hard_regno <= conflict_hard_regno
                    && conflict_hard_regno < hard_regno + nregs))
              {
                fprintf (stderr, "bad allocation for %d and %d\n",
                         ALLOCNO_REGNO (a), ALLOCNO_REGNO (conflict_a));
                gcc_unreachable ();
              }
          }
    }
}
#endif

/* Fix values of array REG_EQUIV_INIT after live range splitting done
   by IRA.  */
static void
fix_reg_equiv_init (void)
{
  int max_regno = max_reg_num ();
  int i, new_regno;
  rtx x, prev, next, insn, set;
  
  if (reg_equiv_init_size < max_regno)
    {
      reg_equiv_init
        = (rtx *) ggc_realloc (reg_equiv_init, max_regno * sizeof (rtx));
      while (reg_equiv_init_size < max_regno)
        reg_equiv_init[reg_equiv_init_size++] = NULL_RTX;
      for (i = FIRST_PSEUDO_REGISTER; i < reg_equiv_init_size; i++)
        for (prev = NULL_RTX, x = reg_equiv_init[i]; x != NULL_RTX; x = next)
          {
            next = XEXP (x, 1);
            insn = XEXP (x, 0);
            set = single_set (insn);
            ira_assert (set != NULL_RTX
                        && (REG_P (SET_DEST (set)) || REG_P (SET_SRC (set))));
            if (REG_P (SET_DEST (set))
                && ((int) REGNO (SET_DEST (set)) == i
                    || (int) ORIGINAL_REGNO (SET_DEST (set)) == i))
              new_regno = REGNO (SET_DEST (set));
            else if (REG_P (SET_SRC (set))
                     && ((int) REGNO (SET_SRC (set)) == i
                         || (int) ORIGINAL_REGNO (SET_SRC (set)) == i))
              new_regno = REGNO (SET_SRC (set));
            else
              gcc_unreachable ();
            if (new_regno == i)
              prev = x;
            else
              {
                if (prev == NULL_RTX)
                  reg_equiv_init[i] = next;
                else
                  XEXP (prev, 1) = next;
                XEXP (x, 1) = reg_equiv_init[new_regno];
                reg_equiv_init[new_regno] = x;
              }
          }
    }
}

#ifdef ENABLE_IRA_CHECKING
/* Print redundant memory-memory copies.  */
static void
print_redundant_copies (void)
{
  int hard_regno;
  ira_allocno_t a;
  ira_copy_t cp, next_cp;
  ira_allocno_iterator ai;
  
  FOR_EACH_ALLOCNO (a, ai)
    {
      if (ALLOCNO_CAP_MEMBER (a) != NULL)
        /* It is a cap. */
        continue;
      hard_regno = ALLOCNO_HARD_REGNO (a);
      if (hard_regno >= 0)
        continue;
      for (cp = ALLOCNO_COPIES (a); cp != NULL; cp = next_cp)
        if (cp->first == a)
          next_cp = cp->next_first_allocno_copy;
        else
          {
            next_cp = cp->next_second_allocno_copy;
            if (internal_flag_ira_verbose > 4 && ira_dump_file != NULL
                && cp->insn != NULL_RTX
                && ALLOCNO_HARD_REGNO (cp->first) == hard_regno)
              fprintf (ira_dump_file,
                       "        Redundant move from %d(freq %d):%d\n",
                       INSN_UID (cp->insn), cp->freq, hard_regno);
          }
    }
}
#endif

/* Setup preferred and alternative classes for new pseudo-registers
   created by IRA starting with START.  */
static void
setup_preferred_alternate_classes_for_new_pseudos (int start)
{
  int i, old_regno;
  int max_regno = max_reg_num ();

  for (i = start; i < max_regno; i++)
    {
      old_regno = ORIGINAL_REGNO (regno_reg_rtx[i]);
      ira_assert (i != old_regno); 
      setup_reg_classes (i, reg_preferred_class (old_regno),
                         reg_alternate_class (old_regno));
      if (internal_flag_ira_verbose > 2 && ira_dump_file != NULL)
        fprintf (ira_dump_file,
                 "    New r%d: setting preferred %s, alternative %s\n",
                 i, reg_class_names[reg_preferred_class (old_regno)],
                 reg_class_names[reg_alternate_class (old_regno)]);
    }
}

\f

/* Regional allocation can create new pseudo-registers.  This function
   expands some arrays for pseudo-registers.  */
static void
expand_reg_info (int old_size)
{
  int i;
  int size = max_reg_num ();

  resize_reg_info ();
  for (i = old_size; i < size; i++)
    {
      reg_renumber[i] = -1;
      setup_reg_classes (i, GENERAL_REGS, ALL_REGS);
    }
}

/* Return TRUE if there is too high register pressure in the function.
   It is used to decide when stack slot sharing is worth to do.  */
static bool
too_high_register_pressure_p (void)
{
  int i;
  enum reg_class cover_class;
  
  for (i = 0; i < ira_reg_class_cover_size; i++)
    {
      cover_class = ira_reg_class_cover[i];
      if (ira_loop_tree_root->reg_pressure[cover_class] > 10000)
        return true;
    }
  return false;
}

\f

/* Indicate that hard register number FROM was eliminated and replaced with
   an offset from hard register number TO.  The status of hard registers live
   at the start of a basic block is updated by replacing a use of FROM with
   a use of TO.  */

void
mark_elimination (int from, int to)
{
  basic_block bb;

  FOR_EACH_BB (bb)
    {
      /* We don't use LIVE info in IRA.  */
      regset r = DF_LR_IN (bb);

      if (REGNO_REG_SET_P (r, from))
        {
          CLEAR_REGNO_REG_SET (r, from);
          SET_REGNO_REG_SET (r, to);
        }
    }
}

\f

struct equivalence
{
  /* Set when a REG_EQUIV note is found or created.  Use to
     keep track of what memory accesses might be created later,
     e.g. by reload.  */
  rtx replacement;
  rtx *src_p;
  /* The list of each instruction which initializes this register.  */
  rtx init_insns;
  /* Loop depth is used to recognize equivalences which appear
     to be present within the same loop (or in an inner loop).  */
  int loop_depth;
  /* Nonzero if this had a preexisting REG_EQUIV note.  */
  int is_arg_equivalence;
  /* Set when an attempt should be made to replace a register
     with the associated src_p entry.  */
  char replace;
};

/* reg_equiv[N] (where N is a pseudo reg number) is the equivalence
   structure for that register.  */
static struct equivalence *reg_equiv;

/* Used for communication between the following two functions: contains
   a MEM that we wish to ensure remains unchanged.  */
static rtx equiv_mem;

/* Set nonzero if EQUIV_MEM is modified.  */
static int equiv_mem_modified;

/* If EQUIV_MEM is modified by modifying DEST, indicate that it is modified.
   Called via note_stores.  */
static void
validate_equiv_mem_from_store (rtx dest, const_rtx set ATTRIBUTE_UNUSED,
                               void *data ATTRIBUTE_UNUSED)
{
  if ((REG_P (dest)
       && reg_overlap_mentioned_p (dest, equiv_mem))
      || (MEM_P (dest)
          && true_dependence (dest, VOIDmode, equiv_mem, rtx_varies_p)))
    equiv_mem_modified = 1;
}

/* Verify that no store between START and the death of REG invalidates
   MEMREF.  MEMREF is invalidated by modifying a register used in MEMREF,
   by storing into an overlapping memory location, or with a non-const
   CALL_INSN.

   Return 1 if MEMREF remains valid.  */
static int
validate_equiv_mem (rtx start, rtx reg, rtx memref)
{
  rtx insn;
  rtx note;

  equiv_mem = memref;
  equiv_mem_modified = 0;

  /* If the memory reference has side effects or is volatile, it isn't a
     valid equivalence.  */
  if (side_effects_p (memref))
    return 0;

  for (insn = start; insn && ! equiv_mem_modified; insn = NEXT_INSN (insn))
    {
      if (! INSN_P (insn))
        continue;

      if (find_reg_note (insn, REG_DEAD, reg))
        return 1;

      if (CALL_P (insn) && ! MEM_READONLY_P (memref)
          && ! RTL_CONST_OR_PURE_CALL_P (insn))
        return 0;

      note_stores (PATTERN (insn), validate_equiv_mem_from_store, NULL);

      /* If a register mentioned in MEMREF is modified via an
         auto-increment, we lose the equivalence.  Do the same if one
         dies; although we could extend the life, it doesn't seem worth
         the trouble.  */

      for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
        if ((REG_NOTE_KIND (note) == REG_INC
             || REG_NOTE_KIND (note) == REG_DEAD)
            && REG_P (XEXP (note, 0))
            && reg_overlap_mentioned_p (XEXP (note, 0), memref))
          return 0;
    }

  return 0;
}

/* Returns zero if X is known to be invariant.  */
static int
equiv_init_varies_p (rtx x)
{
  RTX_CODE code = GET_CODE (x);
  int i;
  const char *fmt;

  switch (code)
    {
    case MEM:
      return !MEM_READONLY_P (x) || equiv_init_varies_p (XEXP (x, 0));

    case CONST:
    case CONST_INT:
    case CONST_DOUBLE:
    case CONST_FIXED:
    case CONST_VECTOR:
    case SYMBOL_REF:
    case LABEL_REF:
      return 0;

    case REG:
      return reg_equiv[REGNO (x)].replace == 0 && rtx_varies_p (x, 0);

    case ASM_OPERANDS:
      if (MEM_VOLATILE_P (x))
        return 1;

      /* Fall through.  */

    default:
      break;
    }

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    if (fmt[i] == 'e')
      {
        if (equiv_init_varies_p (XEXP (x, i)))
          return 1;
      }
    else if (fmt[i] == 'E')
      {
        int j;
        for (j = 0; j < XVECLEN (x, i); j++)
          if (equiv_init_varies_p (XVECEXP (x, i, j)))
            return 1;
      }

  return 0;
}

/* Returns nonzero if X (used to initialize register REGNO) is movable.
   X is only movable if the registers it uses have equivalent initializations
   which appear to be within the same loop (or in an inner loop) and movable
   or if they are not candidates for local_alloc and don't vary.  */
static int
equiv_init_movable_p (rtx x, int regno)
{
  int i, j;
  const char *fmt;
  enum rtx_code code = GET_CODE (x);

  switch (code)
    {
    case SET:
      return equiv_init_movable_p (SET_SRC (x), regno);

    case CC0:
    case CLOBBER:
      return 0;

    case PRE_INC:
    case PRE_DEC:
    case POST_INC:
    case POST_DEC:
    case PRE_MODIFY:
    case POST_MODIFY:
      return 0;

    case REG:
      return (reg_equiv[REGNO (x)].loop_depth >= reg_equiv[regno].loop_depth
              && reg_equiv[REGNO (x)].replace)
             || (REG_BASIC_BLOCK (REGNO (x)) < NUM_FIXED_BLOCKS && ! rtx_varies_p (x, 0));

    case UNSPEC_VOLATILE:
      return 0;

    case ASM_OPERANDS:
      if (MEM_VOLATILE_P (x))
        return 0;

      /* Fall through.  */

    default:
      break;
    }

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    switch (fmt[i])
      {
      case 'e':
        if (! equiv_init_movable_p (XEXP (x, i), regno))
          return 0;
        break;
      case 'E':
        for (j = XVECLEN (x, i) - 1; j >= 0; j--)
          if (! equiv_init_movable_p (XVECEXP (x, i, j), regno))
            return 0;
        break;
      }

  return 1;
}

/* TRUE if X uses any registers for which reg_equiv[REGNO].replace is true.  */
static int
contains_replace_regs (rtx x)
{
  int i, j;
  const char *fmt;
  enum rtx_code code = GET_CODE (x);

  switch (code)
    {
    case CONST_INT:
    case CONST:
    case LABEL_REF:
    case SYMBOL_REF:
    case CONST_DOUBLE:
    case CONST_FIXED:
    case CONST_VECTOR:
    case PC:
    case CC0:
    case HIGH:
      return 0;

    case REG:
      return reg_equiv[REGNO (x)].replace;

    default:
      break;
    }

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    switch (fmt[i])
      {
      case 'e':
        if (contains_replace_regs (XEXP (x, i)))
          return 1;
        break;
      case 'E':
        for (j = XVECLEN (x, i) - 1; j >= 0; j--)
          if (contains_replace_regs (XVECEXP (x, i, j)))
            return 1;
        break;
      }

  return 0;
}

/* TRUE if X references a memory location that would be affected by a store
   to MEMREF.  */
static int
memref_referenced_p (rtx memref, rtx x)
{
  int i, j;
  const char *fmt;
  enum rtx_code code = GET_CODE (x);

  switch (code)
    {
    case CONST_INT:
    case CONST:
    case LABEL_REF:
    case SYMBOL_REF:
    case CONST_DOUBLE:
    case CONST_FIXED:
    case CONST_VECTOR:
    case PC:
    case CC0:
    case HIGH:
    case LO_SUM:
      return 0;

    case REG:
      return (reg_equiv[REGNO (x)].replacement
              && memref_referenced_p (memref,
                                      reg_equiv[REGNO (x)].replacement));

    case MEM:
      if (true_dependence (memref, VOIDmode, x, rtx_varies_p))
        return 1;
      break;

    case SET:
      /* If we are setting a MEM, it doesn't count (its address does), but any
         other SET_DEST that has a MEM in it is referencing the MEM.  */
      if (MEM_P (SET_DEST (x)))
        {
          if (memref_referenced_p (memref, XEXP (SET_DEST (x), 0)))
            return 1;
        }
      else if (memref_referenced_p (memref, SET_DEST (x)))
        return 1;

      return memref_referenced_p (memref, SET_SRC (x));

    default:
      break;
    }

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    switch (fmt[i])
      {
      case 'e':
        if (memref_referenced_p (memref, XEXP (x, i)))
          return 1;
        break;
      case 'E':
        for (j = XVECLEN (x, i) - 1; j >= 0; j--)
          if (memref_referenced_p (memref, XVECEXP (x, i, j)))
            return 1;
        break;
      }

  return 0;
}

/* TRUE if some insn in the range (START, END] references a memory location
   that would be affected by a store to MEMREF.  */
static int
memref_used_between_p (rtx memref, rtx start, rtx end)
{
  rtx insn;

  for (insn = NEXT_INSN (start); insn != NEXT_INSN (end);
       insn = NEXT_INSN (insn))
    {
      if (!INSN_P (insn))
        continue;
      
      if (memref_referenced_p (memref, PATTERN (insn)))
        return 1;

      /* Nonconst functions may access memory.  */
      if (CALL_P (insn) && (! RTL_CONST_CALL_P (insn)))
        return 1;
    }

  return 0;
}

/* Mark REG as having no known equivalence.
   Some instructions might have been processed before and furnished
   with REG_EQUIV notes for this register; these notes will have to be
   removed.
   STORE is the piece of RTL that does the non-constant / conflicting
   assignment - a SET, CLOBBER or REG_INC note.  It is currently not used,
   but needs to be there because this function is called from note_stores.  */
static void
no_equiv (rtx reg, const_rtx store ATTRIBUTE_UNUSED, void *data ATTRIBUTE_UNUSED)
{
  int regno;
  rtx list;

  if (!REG_P (reg))
    return;
  regno = REGNO (reg);
  list = reg_equiv[regno].init_insns;
  if (list == const0_rtx)
    return;
  reg_equiv[regno].init_insns = const0_rtx;
  reg_equiv[regno].replacement = NULL_RTX;
  /* This doesn't matter for equivalences made for argument registers, we
     should keep their initialization insns.  */
  if (reg_equiv[regno].is_arg_equivalence)
    return;
  reg_equiv_init[regno] = NULL_RTX;
  for (; list; list =  XEXP (list, 1))
    {
      rtx insn = XEXP (list, 0);
      remove_note (insn, find_reg_note (insn, REG_EQUIV, NULL_RTX));
    }
}

/* Nonzero if we recorded an equivalence for a LABEL_REF.  */
static int recorded_label_ref;

/* Find registers that are equivalent to a single value throughout the
   compilation (either because they can be referenced in memory or are set once
   from a single constant).  Lower their priority for a register.

   If such a register is only referenced once, try substituting its value
   into the using insn.  If it succeeds, we can eliminate the register
   completely.

   Initialize the REG_EQUIV_INIT array of initializing insns.

   Return non-zero if jump label rebuilding should be done.  */
static int
update_equiv_regs (void)
{
  rtx insn;
  basic_block bb;
  int loop_depth;
  bitmap cleared_regs;
  
  /* We need to keep track of whether or not we recorded a LABEL_REF so
     that we know if the jump optimizer needs to be rerun.  */
  recorded_label_ref = 0;

  reg_equiv = XCNEWVEC (struct equivalence, max_regno);
  reg_equiv_init = GGC_CNEWVEC (rtx, max_regno);
  reg_equiv_init_size = max_regno;

  init_alias_analysis ();

  /* Scan the insns and find which registers have equivalences.  Do this
     in a separate scan of the insns because (due to -fcse-follow-jumps)
     a register can be set below its use.  */
  FOR_EACH_BB (bb)
    {
      loop_depth = bb->loop_depth;

      for (insn = BB_HEAD (bb);
           insn != NEXT_INSN (BB_END (bb));
           insn = NEXT_INSN (insn))
        {
          rtx note;
          rtx set;
          rtx dest, src;
          int regno;

          if (! INSN_P (insn))
            continue;

          for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
            if (REG_NOTE_KIND (note) == REG_INC)
              no_equiv (XEXP (note, 0), note, NULL);

          set = single_set (insn);

          /* If this insn contains more (or less) than a single SET,
             only mark all destinations as having no known equivalence.  */
          if (set == 0)
            {
              note_stores (PATTERN (insn), no_equiv, NULL);
              continue;
            }
          else if (GET_CODE (PATTERN (insn)) == PARALLEL)
            {
              int i;

              for (i = XVECLEN (PATTERN (insn), 0) - 1; i >= 0; i--)
                {
                  rtx part = XVECEXP (PATTERN (insn), 0, i);
                  if (part != set)
                    note_stores (part, no_equiv, NULL);
                }
            }

          dest = SET_DEST (set);
          src = SET_SRC (set);

          /* See if this is setting up the equivalence between an argument
             register and its stack slot.  */
          note = find_reg_note (insn, REG_EQUIV, NULL_RTX);
          if (note)
            {
              gcc_assert (REG_P (dest));
              regno = REGNO (dest);

              /* Note that we don't want to clear reg_equiv_init even if there
                 are multiple sets of this register.  */
              reg_equiv[regno].is_arg_equivalence = 1;

              /* Record for reload that this is an equivalencing insn.  */
              if (rtx_equal_p (src, XEXP (note, 0)))
                reg_equiv_init[regno]
                  = gen_rtx_INSN_LIST (VOIDmode, insn, reg_equiv_init[regno]);

              /* Continue normally in case this is a candidate for
                 replacements.  */
            }

          if (!optimize)
            continue;

          /* We only handle the case of a pseudo register being set
             once, or always to the same value.  */
          /* ??? The mn10200 port breaks if we add equivalences for
             values that need an ADDRESS_REGS register and set them equivalent
             to a MEM of a pseudo.  The actual problem is in the over-conservative
             handling of INPADDR_ADDRESS / INPUT_ADDRESS / INPUT triples in
             calculate_needs, but we traditionally work around this problem
             here by rejecting equivalences when the destination is in a register
             that's likely spilled.  This is fragile, of course, since the
             preferred class of a pseudo depends on all instructions that set
             or use it.  */

          if (!REG_P (dest)
              || (regno = REGNO (dest)) < FIRST_PSEUDO_REGISTER
              || reg_equiv[regno].init_insns == const0_rtx
              || (CLASS_LIKELY_SPILLED_P (reg_preferred_class (regno))
                  && MEM_P (src) && ! reg_equiv[regno].is_arg_equivalence))
            {
              /* This might be setting a SUBREG of a pseudo, a pseudo that is
                 also set somewhere else to a constant.  */
              note_stores (set, no_equiv, NULL);
              continue;
            }

          note = find_reg_note (insn, REG_EQUAL, NULL_RTX);

          /* cse sometimes generates function invariants, but doesn't put a
             REG_EQUAL note on the insn.  Since this note would be redundant,
             there's no point creating it earlier than here.  */
          if (! note && ! rtx_varies_p (src, 0))
            note = set_unique_reg_note (insn, REG_EQUAL, copy_rtx (src));

          /* Don't bother considering a REG_EQUAL note containing an EXPR_LIST
             since it represents a function call */
          if (note && GET_CODE (XEXP (note, 0)) == EXPR_LIST)
            note = NULL_RTX;

          if (DF_REG_DEF_COUNT (regno) != 1
              && (! note
                  || rtx_varies_p (XEXP (note, 0), 0)
                  || (reg_equiv[regno].replacement
                      && ! rtx_equal_p (XEXP (note, 0),
                                        reg_equiv[regno].replacement))))
            {
              no_equiv (dest, set, NULL);
              continue;
            }
          /* Record this insn as initializing this register.  */
          reg_equiv[regno].init_insns
            = gen_rtx_INSN_LIST (VOIDmode, insn, reg_equiv[regno].init_insns);

          /* If this register is known to be equal to a constant, record that
             it is always equivalent to the constant.  */
          if (DF_REG_DEF_COUNT (regno) == 1
              && note && ! rtx_varies_p (XEXP (note, 0), 0))
            {
              rtx note_value = XEXP (note, 0);
              remove_note (insn, note);
              set_unique_reg_note (insn, REG_EQUIV, note_value);
            }

          /* If this insn introduces a "constant" register, decrease the priority
             of that register.  Record this insn if the register is only used once
             more and the equivalence value is the same as our source.

             The latter condition is checked for two reasons:  First, it is an
             indication that it may be more efficient to actually emit the insn
             as written (if no registers are available, reload will substitute
             the equivalence).  Secondly, it avoids problems with any registers
             dying in this insn whose death notes would be missed.

             If we don't have a REG_EQUIV note, see if this insn is loading
             a register used only in one basic block from a MEM.  If so, and the
             MEM remains unchanged for the life of the register, add a REG_EQUIV
             note.  */

          note = find_reg_note (insn, REG_EQUIV, NULL_RTX);

          if (note == 0 && REG_BASIC_BLOCK (regno) >= NUM_FIXED_BLOCKS
              && MEM_P (SET_SRC (set))
              && validate_equiv_mem (insn, dest, SET_SRC (set)))
            note = set_unique_reg_note (insn, REG_EQUIV, copy_rtx (SET_SRC (set)));

          if (note)
            {
              int regno = REGNO (dest);
              rtx x = XEXP (note, 0);

              /* If we haven't done so, record for reload that this is an
                 equivalencing insn.  */
              if (!reg_equiv[regno].is_arg_equivalence)
                reg_equiv_init[regno]
                  = gen_rtx_INSN_LIST (VOIDmode, insn, reg_equiv_init[regno]);

              /* Record whether or not we created a REG_EQUIV note for a LABEL_REF.
                 We might end up substituting the LABEL_REF for uses of the
                 pseudo here or later.  That kind of transformation may turn an
                 indirect jump into a direct jump, in which case we must rerun the
                 jump optimizer to ensure that the JUMP_LABEL fields are valid.  */
              if (GET_CODE (x) == LABEL_REF
                  || (GET_CODE (x) == CONST
                      && GET_CODE (XEXP (x, 0)) == PLUS
                      && (GET_CODE (XEXP (XEXP (x, 0), 0)) == LABEL_REF)))
                recorded_label_ref = 1;

              reg_equiv[regno].replacement = x;
              reg_equiv[regno].src_p = &SET_SRC (set);
              reg_equiv[regno].loop_depth = loop_depth;

              /* Don't mess with things live during setjmp.  */
              if (REG_LIVE_LENGTH (regno) >= 0 && optimize)
                {
                  /* Note that the statement below does not affect the priority
                     in local-alloc!  */
                  REG_LIVE_LENGTH (regno) *= 2;

                  /* If the register is referenced exactly twice, meaning it is
                     set once and used once, indicate that the reference may be
                     replaced by the equivalence we computed above.  Do this
                     even if the register is only used in one block so that
                     dependencies can be handled where the last register is
                     used in a different block (i.e. HIGH / LO_SUM sequences)
                     and to reduce the number of registers alive across
                     calls.  */

                  if (REG_N_REFS (regno) == 2
                      && (rtx_equal_p (x, src)
                          || ! equiv_init_varies_p (src))
                      && NONJUMP_INSN_P (insn)
                      && equiv_init_movable_p (PATTERN (insn), regno))
                    reg_equiv[regno].replace = 1;
                }
            }
        }
    }

  if (!optimize)
    goto out;

  /* A second pass, to gather additional equivalences with memory.  This needs
     to be done after we know which registers we are going to replace.  */

  for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
    {
      rtx set, src, dest;
      unsigned regno;

      if (! INSN_P (insn))
        continue;

      set = single_set (insn);
      if (! set)
        continue;

      dest = SET_DEST (set);
      src = SET_SRC (set);

      /* If this sets a MEM to the contents of a REG that is only used
         in a single basic block, see if the register is always equivalent
         to that memory location and if moving the store from INSN to the
         insn that set REG is safe.  If so, put a REG_EQUIV note on the
         initializing insn.

         Don't add a REG_EQUIV note if the insn already has one.  The existing
         REG_EQUIV is likely more useful than the one we are adding.

         If one of the regs in the address has reg_equiv[REGNO].replace set,
         then we can't add this REG_EQUIV note.  The reg_equiv[REGNO].replace
         optimization may move the set of this register immediately before
         insn, which puts it after reg_equiv[REGNO].init_insns, and hence
         the mention in the REG_EQUIV note would be to an uninitialized
         pseudo.  */

      if (MEM_P (dest) && REG_P (src)
          && (regno = REGNO (src)) >= FIRST_PSEUDO_REGISTER
          && REG_BASIC_BLOCK (regno) >= NUM_FIXED_BLOCKS
          && DF_REG_DEF_COUNT (regno) == 1
          && reg_equiv[regno].init_insns != 0
          && reg_equiv[regno].init_insns != const0_rtx
          && ! find_reg_note (XEXP (reg_equiv[regno].init_insns, 0),
                              REG_EQUIV, NULL_RTX)
          && ! contains_replace_regs (XEXP (dest, 0)))
        {
          rtx init_insn = XEXP (reg_equiv[regno].init_insns, 0);
          if (validate_equiv_mem (init_insn, src, dest)
              && ! memref_used_between_p (dest, init_insn, insn)
              /* Attaching a REG_EQUIV note will fail if INIT_INSN has
                 multiple sets.  */
              && set_unique_reg_note (init_insn, REG_EQUIV, copy_rtx (dest)))
            {
              /* This insn makes the equivalence, not the one initializing
                 the register.  */
              reg_equiv_init[regno]
                = gen_rtx_INSN_LIST (VOIDmode, insn, NULL_RTX);
              df_notes_rescan (init_insn);
            }
        }
    }

  cleared_regs = BITMAP_ALLOC (NULL);
  /* Now scan all regs killed in an insn to see if any of them are
     registers only used that once.  If so, see if we can replace the
     reference with the equivalent form.  If we can, delete the
     initializing reference and this register will go away.  If we
     can't replace the reference, and the initializing reference is
     within the same loop (or in an inner loop), then move the register
     initialization just before the use, so that they are in the same
     basic block.  */
  FOR_EACH_BB_REVERSE (bb)
    {
      loop_depth = bb->loop_depth;
      for (insn = BB_END (bb);
           insn != PREV_INSN (BB_HEAD (bb));
           insn = PREV_INSN (insn))
        {
          rtx link;

          if (! INSN_P (insn))
            continue;

          /* Don't substitute into a non-local goto, this confuses CFG.  */
          if (JUMP_P (insn)
              && find_reg_note (insn, REG_NON_LOCAL_GOTO, NULL_RTX))
            continue;

          for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
            {
              if (REG_NOTE_KIND (link) == REG_DEAD
                  /* Make sure this insn still refers to the register.  */
                  && reg_mentioned_p (XEXP (link, 0), PATTERN (insn)))
                {
                  int regno = REGNO (XEXP (link, 0));
                  rtx equiv_insn;

                  if (! reg_equiv[regno].replace
                      || reg_equiv[regno].loop_depth < loop_depth)
                    continue;

                  /* reg_equiv[REGNO].replace gets set only when
                     REG_N_REFS[REGNO] is 2, i.e. the register is set
                     once and used once.  (If it were only set, but not used,
                     flow would have deleted the setting insns.)  Hence
                     there can only be one insn in reg_equiv[REGNO].init_insns.  */
                  gcc_assert (reg_equiv[regno].init_insns
                              && !XEXP (reg_equiv[regno].init_insns, 1));
                  equiv_insn = XEXP (reg_equiv[regno].init_insns, 0);

                  /* We may not move instructions that can throw, since
                     that changes basic block boundaries and we are not
                     prepared to adjust the CFG to match.  */
                  if (can_throw_internal (equiv_insn))
                    continue;

                  if (asm_noperands (PATTERN (equiv_insn)) < 0
                      && validate_replace_rtx (regno_reg_rtx[regno],
                                               *(reg_equiv[regno].src_p), insn))
                    {
                      rtx equiv_link;
                      rtx last_link;
                      rtx note;

                      /* Find the last note.  */
                      for (last_link = link; XEXP (last_link, 1);
                           last_link = XEXP (last_link, 1))
                        ;

                      /* Append the REG_DEAD notes from equiv_insn.  */
                      equiv_link = REG_NOTES (equiv_insn);
                      while (equiv_link)
                        {
                          note = equiv_link;
                          equiv_link = XEXP (equiv_link, 1);
                          if (REG_NOTE_KIND (note) == REG_DEAD)
                            {
                              remove_note (equiv_insn, note);
                              XEXP (last_link, 1) = note;
                              XEXP (note, 1) = NULL_RTX;
                              last_link = note;
                            }
                        }

                      remove_death (regno, insn);
                      SET_REG_N_REFS (regno, 0);
                      REG_FREQ (regno) = 0;
                      delete_insn (equiv_insn);

                      reg_equiv[regno].init_insns
                        = XEXP (reg_equiv[regno].init_insns, 1);

                      reg_equiv_init[regno] = NULL_RTX;
                      bitmap_set_bit (cleared_regs, regno);
                    }
                  /* Move the initialization of the register to just before
                     INSN.  Update the flow information.  */
                  else if (PREV_INSN (insn) != equiv_insn)
                    {
                      rtx new_insn;

                      new_insn = emit_insn_before (PATTERN (equiv_insn), insn);
                      REG_NOTES (new_insn) = REG_NOTES (equiv_insn);
                      REG_NOTES (equiv_insn) = 0;
                      /* Rescan it to process the notes.  */
                      df_insn_rescan (new_insn);

                      /* Make sure this insn is recognized before
                         reload begins, otherwise
                         eliminate_regs_in_insn will die.  */
                      INSN_CODE (new_insn) = INSN_CODE (equiv_insn);

                      delete_insn (equiv_insn);

                      XEXP (reg_equiv[regno].init_insns, 0) = new_insn;

                      REG_BASIC_BLOCK (regno) = bb->index;
                      REG_N_CALLS_CROSSED (regno) = 0;
                      REG_FREQ_CALLS_CROSSED (regno) = 0;
                      REG_N_THROWING_CALLS_CROSSED (regno) = 0;
                      REG_LIVE_LENGTH (regno) = 2;

                      if (insn == BB_HEAD (bb))
                        BB_HEAD (bb) = PREV_INSN (insn);

                      reg_equiv_init[regno]
                        = gen_rtx_INSN_LIST (VOIDmode, new_insn, NULL_RTX);
                      bitmap_set_bit (cleared_regs, regno);
                    }
                }
            }
        }
    }

  if (!bitmap_empty_p (cleared_regs))
    FOR_EACH_BB (bb)
      {
        bitmap_and_compl_into (DF_LIVE_IN (bb), cleared_regs);
        bitmap_and_compl_into (DF_LIVE_OUT (bb), cleared_regs);
        bitmap_and_compl_into (DF_LR_IN (bb), cleared_regs);
        bitmap_and_compl_into (DF_LR_OUT (bb), cleared_regs);
      }

  BITMAP_FREE (cleared_regs);

  out:
  /* Clean up.  */

  end_alias_analysis ();
  free (reg_equiv);
  return recorded_label_ref;
}

\f

/* Print chain C to FILE.  */
static void
print_insn_chain (FILE *file, struct insn_chain *c)
{
  fprintf (file, "insn=%d, ", INSN_UID(c->insn));
  bitmap_print (file, &c->live_throughout, "live_throughout: ", ", ");
  bitmap_print (file, &c->dead_or_set, "dead_or_set: ", "\n");
}


/* Print all reload_insn_chains to FILE.  */
static void
print_insn_chains (FILE *file)
{
  struct insn_chain *c;
  for (c = reload_insn_chain; c ; c = c->next)
    print_insn_chain (file, c);
}

/* Return true if pseudo REGNO should be added to set live_throughout
   or dead_or_set of the insn chains for reload consideration.  */
static bool
pseudo_for_reload_consideration_p (int regno)
{
  /* Consider spilled pseudos too for IRA because they still have a
     chance to get hard-registers in the reload when IRA is used.  */
  return (reg_renumber[regno] >= 0
          || (ira_conflicts_p && flag_ira_share_spill_slots));
}

/* Init LIVE_SUBREGS[ALLOCNUM] and LIVE_SUBREGS_USED[ALLOCNUM] using
   REG to the number of nregs, and INIT_VALUE to get the
   initialization.  ALLOCNUM need not be the regno of REG.  */
static void
init_live_subregs (bool init_value, sbitmap *live_subregs,
                   int *live_subregs_used, int allocnum, rtx reg)
{
  unsigned int regno = REGNO (SUBREG_REG (reg));
  int size = GET_MODE_SIZE (GET_MODE (regno_reg_rtx[regno]));

  gcc_assert (size > 0);

  /* Been there, done that.  */
  if (live_subregs_used[allocnum])
    return;

  /* Create a new one with zeros.  */
  if (live_subregs[allocnum] == NULL)
    live_subregs[allocnum] = sbitmap_alloc (size);

  /* If the entire reg was live before blasting into subregs, we need
     to init all of the subregs to ones else init to 0.  */
  if (init_value)
    sbitmap_ones (live_subregs[allocnum]);
  else 
    sbitmap_zero (live_subregs[allocnum]);

  /* Set the number of bits that we really want.  */
  live_subregs_used[allocnum] = size;
}

/* Walk the insns of the current function and build reload_insn_chain,
   and record register life information.  */
static void
build_insn_chain (void)
{
  unsigned int i;
  struct insn_chain **p = &reload_insn_chain;
  basic_block bb;
  struct insn_chain *c = NULL;
  struct insn_chain *next = NULL;
  bitmap live_relevant_regs = BITMAP_ALLOC (NULL);
  bitmap elim_regset = BITMAP_ALLOC (NULL);
  /* live_subregs is a vector used to keep accurate information about
     which hardregs are live in multiword pseudos.  live_subregs and
     live_subregs_used are indexed by pseudo number.  The live_subreg
     entry for a particular pseudo is only used if the corresponding
     element is non zero in live_subregs_used.  The value in
     live_subregs_used is number of bytes that the pseudo can
     occupy.  */
  sbitmap *live_subregs = XCNEWVEC (sbitmap, max_regno);
  int *live_subregs_used = XNEWVEC (int, max_regno);

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
    if (TEST_HARD_REG_BIT (eliminable_regset, i))
      bitmap_set_bit (elim_regset, i);
  FOR_EACH_BB_REVERSE (bb)
    {
      bitmap_iterator bi;
      rtx insn;
      
      CLEAR_REG_SET (live_relevant_regs);
      memset (live_subregs_used, 0, max_regno * sizeof (int));
      
      EXECUTE_IF_SET_IN_BITMAP (df_get_live_out (bb), 0, i, bi)
        {
          if (i >= FIRST_PSEUDO_REGISTER)
            break;
          bitmap_set_bit (live_relevant_regs, i);
        }

      EXECUTE_IF_SET_IN_BITMAP (df_get_live_out (bb),
                                FIRST_PSEUDO_REGISTER, i, bi)
        {
          if (pseudo_for_reload_consideration_p (i))
            bitmap_set_bit (live_relevant_regs, i);
        }

      FOR_BB_INSNS_REVERSE (bb, insn)
        {
          if (!NOTE_P (insn) && !BARRIER_P (insn))
            {
              unsigned int uid = INSN_UID (insn);
              df_ref *def_rec;
              df_ref *use_rec;

              c = new_insn_chain ();
              c->next = next;
              next = c;
              *p = c;
              p = &c->prev;
              
              c->insn = insn;
              c->block = bb->index;

              if (INSN_P (insn))
                for (def_rec = DF_INSN_UID_DEFS (uid); *def_rec; def_rec++)
                  {
                    df_ref def = *def_rec;
                    unsigned int regno = DF_REF_REGNO (def);
                    
                    /* Ignore may clobbers because these are generated
                       from calls. However, every other kind of def is
                       added to dead_or_set.  */
                    if (!DF_REF_FLAGS_IS_SET (def, DF_REF_MAY_CLOBBER))
                      {
                        if (regno < FIRST_PSEUDO_REGISTER)
                          {
                            if (!fixed_regs[regno])
                              bitmap_set_bit (&c->dead_or_set, regno);
                          }
                        else if (pseudo_for_reload_consideration_p (regno))
                          bitmap_set_bit (&c->dead_or_set, regno);
                      }

                    if ((regno < FIRST_PSEUDO_REGISTER
                         || reg_renumber[regno] >= 0
                         || ira_conflicts_p)
                        && (!DF_REF_FLAGS_IS_SET (def, DF_REF_CONDITIONAL)))
                      {
                        rtx reg = DF_REF_REG (def);

                        /* We can model subregs, but not if they are
                           wrapped in ZERO_EXTRACTS.  */
                        if (GET_CODE (reg) == SUBREG
                            && !DF_REF_FLAGS_IS_SET (def, DF_REF_ZERO_EXTRACT))
                          {
                            unsigned int start = SUBREG_BYTE (reg);
                            unsigned int last = start 
                              + GET_MODE_SIZE (GET_MODE (reg));

                            init_live_subregs
                              (bitmap_bit_p (live_relevant_regs, regno), 
                               live_subregs, live_subregs_used, regno, reg);

                            if (!DF_REF_FLAGS_IS_SET
                                (def, DF_REF_STRICT_LOW_PART))
                              {
                                /* Expand the range to cover entire words.
                                   Bytes added here are "don't care".  */
                                start
                                  = start / UNITS_PER_WORD * UNITS_PER_WORD;
                                last = ((last + UNITS_PER_WORD - 1)
                                        / UNITS_PER_WORD * UNITS_PER_WORD);
                              }

                            /* Ignore the paradoxical bits.  */
                            if ((int)last > live_subregs_used[regno])
                              last = live_subregs_used[regno];

                            while (start < last)
                              {
                                RESET_BIT (live_subregs[regno], start);
                                start++;
                              }
                            
                            if (sbitmap_empty_p (live_subregs[regno]))
                              {
                                live_subregs_used[regno] = 0;
                                bitmap_clear_bit (live_relevant_regs, regno);
                              }
                            else
                              /* Set live_relevant_regs here because
                                 that bit has to be true to get us to
                                 look at the live_subregs fields.  */
                              bitmap_set_bit (live_relevant_regs, regno);
                          }
                        else
                          {
                            /* DF_REF_PARTIAL is generated for
                               subregs, STRICT_LOW_PART, and
                               ZERO_EXTRACT.  We handle the subreg
                               case above so here we have to keep from
                               modeling the def as a killing def.  */
                            if (!DF_REF_FLAGS_IS_SET (def, DF_REF_PARTIAL))
                              {
                                bitmap_clear_bit (live_relevant_regs, regno);
                                live_subregs_used[regno] = 0;
                              }
                          }
                      }
                  }
          
              bitmap_and_compl_into (live_relevant_regs, elim_regset);
              bitmap_copy (&c->live_throughout, live_relevant_regs);

              if (INSN_P (insn))
                for (use_rec = DF_INSN_UID_USES (uid); *use_rec; use_rec++)
                  {
                    df_ref use = *use_rec;
                    unsigned int regno = DF_REF_REGNO (use);
                    rtx reg = DF_REF_REG (use);
                    
                    /* DF_REF_READ_WRITE on a use means that this use
                       is fabricated from a def that is a partial set
                       to a multiword reg.  Here, we only model the
                       subreg case that is not wrapped in ZERO_EXTRACT
                       precisely so we do not need to look at the
                       fabricated use. */
                    if (DF_REF_FLAGS_IS_SET (use, DF_REF_READ_WRITE) 
                        && !DF_REF_FLAGS_IS_SET (use, DF_REF_ZERO_EXTRACT) 
                        && DF_REF_FLAGS_IS_SET (use, DF_REF_SUBREG))
                      continue;
                    
                    /* Add the last use of each var to dead_or_set.  */
                    if (!bitmap_bit_p (live_relevant_regs, regno))
                      {
                        if (regno < FIRST_PSEUDO_REGISTER)
                          {
                            if (!fixed_regs[regno])
                              bitmap_set_bit (&c->dead_or_set, regno);
                          }
                        else if (pseudo_for_reload_consideration_p (regno))
                          bitmap_set_bit (&c->dead_or_set, regno);
                      }
                    
                    if (regno < FIRST_PSEUDO_REGISTER
                        || pseudo_for_reload_consideration_p (regno))
                      {
                        if (GET_CODE (reg) == SUBREG
                            && !DF_REF_FLAGS_IS_SET (use,
                                                     DF_REF_SIGN_EXTRACT
                                                     | DF_REF_ZERO_EXTRACT)) 
                          {
                            unsigned int start = SUBREG_BYTE (reg);
                            unsigned int last = start 
                              + GET_MODE_SIZE (GET_MODE (reg));
                            
                            init_live_subregs
                              (bitmap_bit_p (live_relevant_regs, regno), 
                               live_subregs, live_subregs_used, regno, reg);
                            
                            /* Ignore the paradoxical bits.  */
                            if ((int)last > live_subregs_used[regno])
                              last = live_subregs_used[regno];

                            while (start < last)
                              {
                                SET_BIT (live_subregs[regno], start);
                                start++;
                              }
                          }
                        else
                          /* Resetting the live_subregs_used is
                             effectively saying do not use the subregs
                             because we are reading the whole
                             pseudo.  */
                          live_subregs_used[regno] = 0;
                        bitmap_set_bit (live_relevant_regs, regno);
                      }
                  }
            }
        }

      /* FIXME!! The following code is a disaster.  Reload needs to see the
         labels and jump tables that are just hanging out in between
         the basic blocks.  See pr33676.  */
      insn = BB_HEAD (bb);
      
      /* Skip over the barriers and cruft.  */
      while (insn && (BARRIER_P (insn) || NOTE_P (insn) 
                      || BLOCK_FOR_INSN (insn) == bb))
        insn = PREV_INSN (insn);
      
      /* While we add anything except barriers and notes, the focus is
         to get the labels and jump tables into the
         reload_insn_chain.  */
      while (insn)
        {
          if (!NOTE_P (insn) && !BARRIER_P (insn))
            {
              if (BLOCK_FOR_INSN (insn))
                break;
              
              c = new_insn_chain ();
              c->next = next;
              next = c;
              *p = c;
              p = &c->prev;
              
              /* The block makes no sense here, but it is what the old
                 code did.  */
              c->block = bb->index;
              c->insn = insn;
              bitmap_copy (&c->live_throughout, live_relevant_regs);
            }     
          insn = PREV_INSN (insn);
        }
    }

  for (i = 0; i < (unsigned int) max_regno; i++)
    if (live_subregs[i])
      free (live_subregs[i]);

  reload_insn_chain = c;
  *p = NULL;

  free (live_subregs);
  free (live_subregs_used);
  BITMAP_FREE (live_relevant_regs);
  BITMAP_FREE (elim_regset);

  if (dump_file)
    print_insn_chains (dump_file);
}

\f

/* All natural loops.  */
struct loops ira_loops;

/* True if we have allocno conflicts.  It is false for non-optimized
   mode or when the conflict table is too big.  */
bool ira_conflicts_p;

/* This is the main entry of IRA.  */
static void
ira (FILE *f)
{
  int overall_cost_before, allocated_reg_info_size;
  bool loops_p;
  int max_regno_before_ira, ira_max_point_before_emit;
  int rebuild_p;
  int saved_flag_ira_share_spill_slots;
  basic_block bb;

  timevar_push (TV_IRA);

  if (flag_ira_verbose < 10)
    {
      internal_flag_ira_verbose = flag_ira_verbose;
      ira_dump_file = f;
    }
  else
    {
      internal_flag_ira_verbose = flag_ira_verbose - 10;
      ira_dump_file = stderr;
    }

  ira_conflicts_p = optimize > 0;
  setup_prohibited_mode_move_regs ();

  df_note_add_problem ();

  if (optimize == 1)
    {
      df_live_add_problem ();
      df_live_set_all_dirty ();
    }
#ifdef ENABLE_CHECKING
  df->changeable_flags |= DF_VERIFY_SCHEDULED;
#endif
  df_analyze ();
  df_clear_flags (DF_NO_INSN_RESCAN);
  regstat_init_n_sets_and_refs ();
  regstat_compute_ri ();

  /* If we are not optimizing, then this is the only place before
     register allocation where dataflow is done.  And that is needed
     to generate these warnings.  */
  if (warn_clobbered)
    generate_setjmp_warnings ();

  /* Determine if the current function is a leaf before running IRA
     since this can impact optimizations done by the prologue and
     epilogue thus changing register elimination offsets.  */
  current_function_is_leaf = leaf_function_p ();

  rebuild_p = update_equiv_regs ();

#ifndef IRA_NO_OBSTACK
  gcc_obstack_init (&ira_obstack);
#endif
  bitmap_obstack_initialize (&ira_bitmap_obstack);
  if (optimize)
    {      
      max_regno = max_reg_num ();
      ira_reg_equiv_len = max_regno;
      ira_reg_equiv_invariant_p
        = (bool *) ira_allocate (max_regno * sizeof (bool));
      memset (ira_reg_equiv_invariant_p, 0, max_regno * sizeof (bool));
      ira_reg_equiv_const = (rtx *) ira_allocate (max_regno * sizeof (rtx));
      memset (ira_reg_equiv_const, 0, max_regno * sizeof (rtx));
      find_reg_equiv_invariant_const ();
      if (rebuild_p)
        {
          timevar_push (TV_JUMP);
          rebuild_jump_labels (get_insns ());
          purge_all_dead_edges ();
          timevar_pop (TV_JUMP);
        }
    }

  max_regno_before_ira = allocated_reg_info_size = max_reg_num ();
  allocate_reg_info ();
  setup_eliminable_regset ();
      
  ira_overall_cost = ira_reg_cost = ira_mem_cost = 0;
  ira_load_cost = ira_store_cost = ira_shuffle_cost = 0;
  ira_move_loops_num = ira_additional_jumps_num = 0;
  
  ira_assert (current_loops == NULL);
  flow_loops_find (&ira_loops);
  current_loops = &ira_loops;
      
  if (internal_flag_ira_verbose > 0 && ira_dump_file != NULL)
    fprintf (ira_dump_file, "Building IRA IR\n");
  loops_p = ira_build (optimize
                       && (flag_ira_region == IRA_REGION_ALL
                           || flag_ira_region == IRA_REGION_MIXED));
  
  ira_assert (ira_conflicts_p || !loops_p);

  saved_flag_ira_share_spill_slots = flag_ira_share_spill_slots;
  if (too_high_register_pressure_p ())
    /* It is just wasting compiler's time to pack spilled pseudos into
       stack slots in this case -- prohibit it.  */ 
    flag_ira_share_spill_slots = FALSE;

  ira_color ();
      
  ira_max_point_before_emit = ira_max_point;
      
  ira_emit (loops_p);
  
  if (ira_conflicts_p)
    {
      max_regno = max_reg_num ();
      
      if (! loops_p)
        ira_initiate_assign ();
      else
        {
          expand_reg_info (allocated_reg_info_size);
          setup_preferred_alternate_classes_for_new_pseudos
            (allocated_reg_info_size);
          allocated_reg_info_size = max_regno;
          
          if (internal_flag_ira_verbose > 0 && ira_dump_file != NULL)
            fprintf (ira_dump_file, "Flattening IR\n");
          ira_flattening (max_regno_before_ira, ira_max_point_before_emit);
          /* New insns were generated: add notes and recalculate live
             info.  */
          df_analyze ();
          
          flow_loops_find (&ira_loops);
          current_loops = &ira_loops;

          setup_allocno_assignment_flags ();
          ira_initiate_assign ();
          ira_reassign_conflict_allocnos (max_regno);
        }
    }

  setup_reg_renumber ();
  
  calculate_allocation_cost ();
  
#ifdef ENABLE_IRA_CHECKING
  if (ira_conflicts_p)
    check_allocation ();
#endif
      
  delete_trivially_dead_insns (get_insns (), max_reg_num ());
  max_regno = max_reg_num ();
  
  /* And the reg_equiv_memory_loc array.  */
  VEC_safe_grow (rtx, gc, reg_equiv_memory_loc_vec, max_regno);
  memset (VEC_address (rtx, reg_equiv_memory_loc_vec), 0,
          sizeof (rtx) * max_regno);
  reg_equiv_memory_loc = VEC_address (rtx, reg_equiv_memory_loc_vec);

  if (max_regno != max_regno_before_ira)
    {
      regstat_free_n_sets_and_refs ();
      regstat_free_ri ();
      regstat_init_n_sets_and_refs ();
      regstat_compute_ri ();
    }

  allocate_initial_values (reg_equiv_memory_loc);

  overall_cost_before = ira_overall_cost;
  if (ira_conflicts_p)
    {
      fix_reg_equiv_init ();
      
#ifdef ENABLE_IRA_CHECKING
      print_redundant_copies ();
#endif

      ira_spilled_reg_stack_slots_num = 0;
      ira_spilled_reg_stack_slots
        = ((struct ira_spilled_reg_stack_slot *)
           ira_allocate (max_regno
                         * sizeof (struct ira_spilled_reg_stack_slot)));
      memset (ira_spilled_reg_stack_slots, 0,
              max_regno * sizeof (struct ira_spilled_reg_stack_slot));
    }
  
  timevar_pop (TV_IRA);

  timevar_push (TV_RELOAD);
  df_set_flags (DF_NO_INSN_RESCAN);
  build_insn_chain ();

  reload_completed = !reload (get_insns (), ira_conflicts_p);

  timevar_pop (TV_RELOAD);

  timevar_push (TV_IRA);

  if (ira_conflicts_p)
    {
      ira_free (ira_spilled_reg_stack_slots);
      
      ira_finish_assign ();
      
    }  
  if (internal_flag_ira_verbose > 0 && ira_dump_file != NULL
      && overall_cost_before != ira_overall_cost)
    fprintf (ira_dump_file, "+++Overall after reload %d\n", ira_overall_cost);
  ira_destroy ();
  
  flag_ira_share_spill_slots = saved_flag_ira_share_spill_slots;

  flow_loops_free (&ira_loops);
  free_dominance_info (CDI_DOMINATORS);
  FOR_ALL_BB (bb)
    bb->loop_father = NULL;
  current_loops = NULL;

  regstat_free_ri ();
  regstat_free_n_sets_and_refs ();
      
  if (optimize)
    {
      cleanup_cfg (CLEANUP_EXPENSIVE);
      
      ira_free (ira_reg_equiv_invariant_p);
      ira_free (ira_reg_equiv_const);
    }

  bitmap_obstack_release (&ira_bitmap_obstack);
#ifndef IRA_NO_OBSTACK
  obstack_free (&ira_obstack, NULL);
#endif

  /* The code after the reload has changed so much that at this point
     we might as well just rescan everything.  Not that
     df_rescan_all_insns is not going to help here because it does not
     touch the artificial uses and defs.  */
  df_finish_pass (true);
  if (optimize > 1)
    df_live_add_problem ();
  df_scan_alloc (NULL);
  df_scan_blocks ();

  if (optimize)
    df_analyze ();

  timevar_pop (TV_IRA);
}

\f

static bool
gate_ira (void)
{
  return true;
}

/* Run the integrated register allocator.  */
static unsigned int
rest_of_handle_ira (void)
{
  ira (dump_file);
  return 0;
}

struct rtl_opt_pass pass_ira =
{
 {
  RTL_PASS,
  "ira",                                /* name */
  gate_ira,                             /* gate */
  rest_of_handle_ira,                   /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_NONE,                              /* tv_id */
  0,                                    /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_dump_func |
  TODO_ggc_collect                      /* todo_flags_finish */
 }
};