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/* Allocate registers for pseudo-registers that span basic blocks.

   Copyright (C) 1987, 1988, 1991, 1994, 1996, 1997, 1998,

   1999, 2000, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.

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 2, 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 COPYING.  If not, write to the Free

Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "machmode.h"

#include "hard-reg-set.h"

#include "rtl.h"

#include "tm_p.h"

#include "flags.h"

#include "regs.h"

#include "function.h"

#include "insn-config.h"

#include "recog.h"

#include "reload.h"

#include "output.h"

#include "toplev.h"

#include "tree-pass.h"

#include "timevar.h"

/* This pass of the compiler performs global register allocation.

   It assigns hard register numbers to all the pseudo registers

   that were not handled in local_alloc.  Assignments are recorded

   in the vector reg_renumber, not by changing the rtl code.

   (Such changes are made by final).  The entry point is

   the function global_alloc.

   After allocation is complete, the reload pass is run as a subroutine

   of this pass, so that when a pseudo reg loses its hard reg due to

   spilling it is possible to make a second attempt to find a hard

   reg for it.  The reload pass is independent in other respects

   and it is run even when stupid register allocation is in use.

   1. Assign allocation-numbers (allocnos) to the pseudo-registers

   still needing allocations and to the pseudo-registers currently

   allocated by local-alloc which may be spilled by reload.

   Set up tables reg_allocno and allocno_reg to map

   reg numbers to allocnos and vice versa.

   max_allocno gets the number of allocnos in use.

   2. Allocate a max_allocno by max_allocno conflict bit matrix and clear it.

   Allocate a max_allocno by FIRST_PSEUDO_REGISTER conflict matrix

   for conflicts between allocnos and explicit hard register use

   (which includes use of pseudo-registers allocated by local_alloc).

   3. For each basic block

    walk forward through the block, recording which

    pseudo-registers and which hardware registers are live.

    Build the conflict matrix between the pseudo-registers

    and another of pseudo-registers versus hardware registers.

    Also record the preferred hardware registers

    for each pseudo-register.

   4. Sort a table of the allocnos into order of

   desirability of the variables.

   5. Allocate the variables in that order; each if possible into

   a preferred register, else into another register.  */

/* Number of pseudo-registers which are candidates for allocation.  */

static int max_allocno;

/* Indexed by (pseudo) reg number, gives the allocno, or -1

   for pseudo registers which are not to be allocated.  */

static int *reg_allocno;

struct allocno

{

  int reg;

  /* Gives the number of consecutive hard registers needed by that

     pseudo reg.  */

  int size;

  /* Number of calls crossed by each allocno.  */

  int calls_crossed;

  /* Number of calls that might throw crossed by each allocno.  */

  int throwing_calls_crossed;

  /* Number of refs to each allocno.  */

  int n_refs;

  /* Frequency of uses of each allocno.  */

  int freq;

  /* Guess at live length of each allocno.

     This is actually the max of the live lengths of the regs.  */

  int live_length;

  /* Set of hard regs conflicting with allocno N.  */

  HARD_REG_SET hard_reg_conflicts;

  /* Set of hard regs preferred by allocno N.

     This is used to make allocnos go into regs that are copied to or from them,

     when possible, to reduce register shuffling.  */

  HARD_REG_SET hard_reg_preferences;

  /* Similar, but just counts register preferences made in simple copy

     operations, rather than arithmetic.  These are given priority because

     we can always eliminate an insn by using these, but using a register

     in the above list won't always eliminate an insn.  */

  HARD_REG_SET hard_reg_copy_preferences;

  /* Similar to hard_reg_preferences, but includes bits for subsequent

     registers when an allocno is multi-word.  The above variable is used for

     allocation while this is used to build reg_someone_prefers, below.  */

  HARD_REG_SET hard_reg_full_preferences;

  /* Set of hard registers that some later allocno has a preference for.  */

  HARD_REG_SET regs_someone_prefers;

#ifdef STACK_REGS

  /* Set to true if allocno can't be allocated in the stack register.  */

  bool no_stack_reg;

#endif

};

static struct allocno *allocno;

/* A vector of the integers from 0 to max_allocno-1,

   sorted in the order of first-to-be-allocated first.  */

static int *allocno_order;

/* Indexed by (pseudo) reg number, gives the number of another

   lower-numbered pseudo reg which can share a hard reg with this pseudo

   *even if the two pseudos would otherwise appear to conflict*.  */

static int *reg_may_share;

/* Define the number of bits in each element of `conflicts' and what

   type that element has.  We use the largest integer format on the

   host machine.  */

#define INT_BITS HOST_BITS_PER_WIDE_INT

#define INT_TYPE HOST_WIDE_INT

/* max_allocno by max_allocno array of bits,

   recording whether two allocno's conflict (can't go in the same

   hardware register).

   `conflicts' is symmetric after the call to mirror_conflicts.  */

static INT_TYPE *conflicts;

/* Number of ints require to hold max_allocno bits.

   This is the length of a row in `conflicts'.  */

static int allocno_row_words;

/* Two macros to test or store 1 in an element of `conflicts'.  */

#define CONFLICTP(I, J) \

 (conflicts[(I) * allocno_row_words + (unsigned) (J) / INT_BITS]        \

  & ((INT_TYPE) 1 << ((unsigned) (J) % INT_BITS)))

/* For any allocno set in ALLOCNO_SET, set ALLOCNO to that allocno,

   and execute CODE.  */

#define EXECUTE_IF_SET_IN_ALLOCNO_SET(ALLOCNO_SET, ALLOCNO, CODE)       \

do {                                                                    \

  int i_;                                                               \

  int allocno_;                                                         \

  INT_TYPE *p_ = (ALLOCNO_SET);                                         \

                                                                        \

  for (i_ = allocno_row_words - 1, allocno_ = 0; i_ >= 0;         \

       i_--, allocno_ += INT_BITS)                                      \

    {                                                                   \

      unsigned INT_TYPE word_ = (unsigned INT_TYPE) *p_++;              \

                                                                        \

      for ((ALLOCNO) = allocno_; word_; word_ >>= 1, (ALLOCNO)++)       \

        {                                                               \

          if (word_ & 1)                                                \

            {CODE;}                                                     \

        }                                                               \

    }                                                                   \

} while (0)

/* This doesn't work for non-GNU C due to the way CODE is macro expanded.  */

#if 0

/* For any allocno that conflicts with IN_ALLOCNO, set OUT_ALLOCNO to

   the conflicting allocno, and execute CODE.  This macro assumes that

   mirror_conflicts has been run.  */

#define EXECUTE_IF_CONFLICT(IN_ALLOCNO, OUT_ALLOCNO, CODE)\

  EXECUTE_IF_SET_IN_ALLOCNO_SET (conflicts + (IN_ALLOCNO) * allocno_row_words,\

                                 OUT_ALLOCNO, (CODE))

#endif

/* Set of hard regs currently live (during scan of all insns).  */

static HARD_REG_SET hard_regs_live;

/* Set of registers that global-alloc isn't supposed to use.  */

static HARD_REG_SET no_global_alloc_regs;

/* Set of registers used so far.  */

static HARD_REG_SET regs_used_so_far;

/* Number of refs to each hard reg, as used by local alloc.

   It is zero for a reg that contains global pseudos or is explicitly used.  */

static int local_reg_n_refs[FIRST_PSEUDO_REGISTER];

/* Frequency of uses of given hard reg.  */

static int local_reg_freq[FIRST_PSEUDO_REGISTER];

/* Guess at live length of each hard reg, as used by local alloc.

   This is actually the sum of the live lengths of the specific regs.  */

static int local_reg_live_length[FIRST_PSEUDO_REGISTER];

/* Set to 1 a bit in a vector TABLE of HARD_REG_SETs, for vector

   element I, and hard register number J.  */

#define SET_REGBIT(TABLE, I, J)  SET_HARD_REG_BIT (allocno[I].TABLE, J)

/* Bit mask for allocnos live at current point in the scan.  */

static INT_TYPE *allocnos_live;

/* Test, set or clear bit number I in allocnos_live,

   a bit vector indexed by allocno.  */

#define SET_ALLOCNO_LIVE(I)                             \

  (allocnos_live[(unsigned) (I) / INT_BITS]             \

     |= ((INT_TYPE) 1 << ((unsigned) (I) % INT_BITS)))

#define CLEAR_ALLOCNO_LIVE(I)                           \

  (allocnos_live[(unsigned) (I) / INT_BITS]             \

     &= ~((INT_TYPE) 1 << ((unsigned) (I) % INT_BITS)))

/* This is turned off because it doesn't work right for DImode.

   (And it is only used for DImode, so the other cases are worthless.)

   The problem is that it isn't true that there is NO possibility of conflict;

   only that there is no conflict if the two pseudos get the exact same regs.

   If they were allocated with a partial overlap, there would be a conflict.

   We can't safely turn off the conflict unless we have another way to

   prevent the partial overlap.

   Idea: change hard_reg_conflicts so that instead of recording which

   hard regs the allocno may not overlap, it records where the allocno

   may not start.  Change both where it is used and where it is updated.

   Then there is a way to record that (reg:DI 108) may start at 10

   but not at 9 or 11.  There is still the question of how to record

   this semi-conflict between two pseudos.  */

#if 0

/* Reg pairs for which conflict after the current insn

   is inhibited by a REG_NO_CONFLICT note.

   If the table gets full, we ignore any other notes--that is conservative.  */

#define NUM_NO_CONFLICT_PAIRS 4

/* Number of pairs in use in this insn.  */

int n_no_conflict_pairs;

static struct { int allocno1, allocno2;}

  no_conflict_pairs[NUM_NO_CONFLICT_PAIRS];

#endif /* 0 */

/* Record all regs that are set in any one insn.

   Communication from mark_reg_{store,clobber} and global_conflicts.  */

static rtx *regs_set;

static int n_regs_set;

/* All registers that can be eliminated.  */

static HARD_REG_SET eliminable_regset;

static int allocno_compare (const void *, const void *);

static void global_conflicts (void);

static void mirror_conflicts (void);

static void expand_preferences (void);

static void prune_preferences (void);

static void find_reg (int, HARD_REG_SET, int, int, int);

static void record_one_conflict (int);

static void record_conflicts (int *, int);

static void mark_reg_store (rtx, rtx, void *);

static void mark_reg_clobber (rtx, rtx, void *);

static void mark_reg_conflicts (rtx);

static void mark_reg_death (rtx);

static void mark_reg_live_nc (int, enum machine_mode);

static void set_preference (rtx, rtx);

static void dump_conflicts (FILE *);

static void reg_becomes_live (rtx, rtx, void *);

static void reg_dies (int, enum machine_mode, struct insn_chain *);

static void allocate_bb_info (void);

static void free_bb_info (void);

static bool check_earlyclobber (rtx);

static void mark_reg_use_for_earlyclobber_1 (rtx *, void *);

static int mark_reg_use_for_earlyclobber (rtx *, void *);

static void calculate_local_reg_bb_info (void);

static void set_up_bb_rts_numbers (void);

static int rpost_cmp (const void *, const void *);

static void calculate_reg_pav (void);

static void modify_reg_pav (void);

static void make_accurate_live_analysis (void);

/* Perform allocation of pseudo-registers not allocated by local_alloc.

   FILE is a file to output debugging information on,

   or zero if such output is not desired.

   Return value is nonzero if reload failed

   and we must not do any more for this function.  */

int

global_alloc (FILE *file)

{

  int retval;

#ifdef ELIMINABLE_REGS

  static const struct {const int from, to; } eliminables[] = ELIMINABLE_REGS;

#endif

  int need_fp

    = (! flag_omit_frame_pointer

       || (current_function_calls_alloca && EXIT_IGNORE_STACK)

       || FRAME_POINTER_REQUIRED);

  size_t i;

  rtx x;

  make_accurate_live_analysis ();

  max_allocno = 0;

  /* A machine may have certain hard registers that

     are safe to use only within a basic block.  */

  CLEAR_HARD_REG_SET (no_global_alloc_regs);

  /* 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 < 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 (no_global_alloc_regs, eliminables[i].from);

        }

      else if (cannot_elim)

        error ("%s cannot be used in asm here",

               reg_names[eliminables[i].from]);

      else

        regs_ever_live[eliminables[i].from] = 1;

    }

#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 (no_global_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

    regs_ever_live[HARD_FRAME_POINTER_REGNUM] = 1;

#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 (no_global_alloc_regs, FRAME_POINTER_REGNUM);

    }

  else if (need_fp)

    error ("%s cannot be used in asm here", reg_names[FRAME_POINTER_REGNUM]);

  else

    regs_ever_live[FRAME_POINTER_REGNUM] = 1;

#endif

  /* Track which registers have already been used.  Start with registers

     explicitly in the rtl, then registers allocated by local register

     allocation.  */

  CLEAR_HARD_REG_SET (regs_used_so_far);

#ifdef LEAF_REGISTERS

  /* If we are doing the leaf function optimization, and this is a leaf

     function, it means that the registers that take work to save are those

     that need a register window.  So prefer the ones that can be used in

     a leaf function.  */

  {

    const char *cheap_regs;

    const char *const leaf_regs = LEAF_REGISTERS;

    if (only_leaf_regs_used () && leaf_function_p ())

      cheap_regs = leaf_regs;

    else

      cheap_regs = call_used_regs;

    for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)

      if (regs_ever_live[i] || cheap_regs[i])

        SET_HARD_REG_BIT (regs_used_so_far, i);

  }

#else

  /* We consider registers that do not have to be saved over calls as if

     they were already used since there is no cost in using them.  */

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)

    if (regs_ever_live[i] || call_used_regs[i])

      SET_HARD_REG_BIT (regs_used_so_far, i);

#endif

  for (i = FIRST_PSEUDO_REGISTER; i < (size_t) max_regno; i++)

    if (reg_renumber[i] >= 0)

      SET_HARD_REG_BIT (regs_used_so_far, reg_renumber[i]);

  /* Establish mappings from register number to allocation number

     and vice versa.  In the process, count the allocnos.  */

  reg_allocno = xmalloc (max_regno * sizeof (int));

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)

    reg_allocno[i] = -1;

  /* Initialize the shared-hard-reg mapping

     from the list of pairs that may share.  */

  reg_may_share = xcalloc (max_regno, sizeof (int));

  for (x = regs_may_share; x; x = XEXP (XEXP (x, 1), 1))

    {

      int r1 = REGNO (XEXP (x, 0));

      int r2 = REGNO (XEXP (XEXP (x, 1), 0));

      if (r1 > r2)

        reg_may_share[r1] = r2;

      else

        reg_may_share[r2] = r1;

    }

  for (i = FIRST_PSEUDO_REGISTER; i < (size_t) max_regno; i++)

    /* Note that reg_live_length[i] < 0 indicates a "constant" reg

       that we are supposed to refrain from putting in a hard reg.

       -2 means do make an allocno but don't allocate it.  */

    if (REG_N_REFS (i) != 0 && REG_LIVE_LENGTH (i) != -1

        /* Don't allocate pseudos that cross calls,

           if this function receives a nonlocal goto.  */

        && (! current_function_has_nonlocal_label

            || REG_N_CALLS_CROSSED (i) == 0))

      {

        if (reg_renumber[i] < 0

            && reg_may_share[i] && reg_allocno[reg_may_share[i]] >= 0)

          reg_allocno[i] = reg_allocno[reg_may_share[i]];

        else

          reg_allocno[i] = max_allocno++;

        gcc_assert (REG_LIVE_LENGTH (i));

      }

    else

      reg_allocno[i] = -1;

  allocno = xcalloc (max_allocno, sizeof (struct allocno));

  for (i = FIRST_PSEUDO_REGISTER; i < (size_t) max_regno; i++)

    if (reg_allocno[i] >= 0)

      {

        int num = reg_allocno[i];

        allocno[num].reg = i;

        allocno[num].size = PSEUDO_REGNO_SIZE (i);

        allocno[num].calls_crossed += REG_N_CALLS_CROSSED (i);

        allocno[num].throwing_calls_crossed

          += REG_N_THROWING_CALLS_CROSSED (i);

        allocno[num].n_refs += REG_N_REFS (i);

        allocno[num].freq += REG_FREQ (i);

        if (allocno[num].live_length < REG_LIVE_LENGTH (i))

          allocno[num].live_length = REG_LIVE_LENGTH (i);

      }

  /* Calculate amount of usage of each hard reg by pseudos

     allocated by local-alloc.  This is to see if we want to

     override it.  */

  memset (local_reg_live_length, 0, sizeof local_reg_live_length);

  memset (local_reg_n_refs, 0, sizeof local_reg_n_refs);

  memset (local_reg_freq, 0, sizeof local_reg_freq);

  for (i = FIRST_PSEUDO_REGISTER; i < (size_t) max_regno; i++)

    if (reg_renumber[i] >= 0)

      {

        int regno = reg_renumber[i];

        int endregno = regno + hard_regno_nregs[regno][PSEUDO_REGNO_MODE (i)];

        int j;

        for (j = regno; j < endregno; j++)

          {

            local_reg_n_refs[j] += REG_N_REFS (i);

            local_reg_freq[j] += REG_FREQ (i);

            local_reg_live_length[j] += REG_LIVE_LENGTH (i);

          }

      }

  /* We can't override local-alloc for a reg used not just by local-alloc.  */

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)

    if (regs_ever_live[i])

      local_reg_n_refs[i] = 0, local_reg_freq[i] = 0;

  allocno_row_words = (max_allocno + INT_BITS - 1) / INT_BITS;

  /* We used to use alloca here, but the size of what it would try to

     allocate would occasionally cause it to exceed the stack limit and

     cause unpredictable core dumps.  Some examples were > 2Mb in size.  */

  conflicts = xcalloc (max_allocno * allocno_row_words, sizeof (INT_TYPE));

  allocnos_live = xmalloc (allocno_row_words * sizeof (INT_TYPE));

  /* If there is work to be done (at least one reg to allocate),

     perform global conflict analysis and allocate the regs.  */

  if (max_allocno > 0)

    {

      /* Scan all the insns and compute the conflicts among allocnos

         and between allocnos and hard regs.  */

      global_conflicts ();

      mirror_conflicts ();

      /* Eliminate conflicts between pseudos and eliminable registers.  If

         the register is not eliminated, the pseudo won't really be able to

         live in the eliminable register, so the conflict doesn't matter.

         If we do eliminate the register, the conflict will no longer exist.

         So in either case, we can ignore the conflict.  Likewise for

         preferences.  */

      for (i = 0; i < (size_t) max_allocno; i++)

        {

          AND_COMPL_HARD_REG_SET (allocno[i].hard_reg_conflicts,

                                  eliminable_regset);

          AND_COMPL_HARD_REG_SET (allocno[i].hard_reg_copy_preferences,

                                  eliminable_regset);

          AND_COMPL_HARD_REG_SET (allocno[i].hard_reg_preferences,

                                  eliminable_regset);

        }

      /* Try to expand the preferences by merging them between allocnos.  */

      expand_preferences ();

      /* Determine the order to allocate the remaining pseudo registers.  */

      allocno_order = xmalloc (max_allocno * sizeof (int));

      for (i = 0; i < (size_t) max_allocno; i++)

        allocno_order[i] = i;

      /* Default the size to 1, since allocno_compare uses it to divide by.

         Also convert allocno_live_length of zero to -1.  A length of zero

         can occur when all the registers for that allocno have reg_live_length

         equal to -2.  In this case, we want to make an allocno, but not

         allocate it.  So avoid the divide-by-zero and set it to a low

         priority.  */

      for (i = 0; i < (size_t) max_allocno; i++)

        {

          if (allocno[i].size == 0)

            allocno[i].size = 1;

          if (allocno[i].live_length == 0)

            allocno[i].live_length = -1;

        }

      qsort (allocno_order, max_allocno, sizeof (int), allocno_compare);

      prune_preferences ();

      if (file)

        dump_conflicts (file);

      /* Try allocating them, one by one, in that order,

         except for parameters marked with reg_live_length[regno] == -2.  */

      for (i = 0; i < (size_t) max_allocno; i++)

        if (reg_renumber[allocno[allocno_order[i]].reg] < 0

            && REG_LIVE_LENGTH (allocno[allocno_order[i]].reg) >= 0)

          {

            /* If we have more than one register class,

               first try allocating in the class that is cheapest

               for this pseudo-reg.  If that fails, try any reg.  */

            if (N_REG_CLASSES > 1)

              {

                find_reg (allocno_order[i], 0, 0, 0, 0);

                if (reg_renumber[allocno[allocno_order[i]].reg] >= 0)

                  continue;

              }

            if (reg_alternate_class (allocno[allocno_order[i]].reg) != NO_REGS)

              find_reg (allocno_order[i], 0, 1, 0, 0);

          }

      free (allocno_order);

    }

  /* Do the reloads now while the allocno data still exist, so that we can

     try to assign new hard regs to any pseudo regs that are spilled.  */

#if 0 /* We need to eliminate regs even if there is no rtl code,

         for the sake of debugging information.  */

  if (n_basic_blocks > 0)

#endif

    {

      build_insn_chain (get_insns ());

      retval = reload (get_insns (), 1);

    }

  /* Clean up.  */

  free (reg_allocno);

  free (reg_may_share);

  free (allocno);

  free (conflicts);

  free (allocnos_live);

  return retval;

}

/* Sort predicate for ordering the allocnos.

   Returns -1 (1) if *v1 should be allocated before (after) *v2.  */

static int

allocno_compare (const void *v1p, const void *v2p)

{

  int v1 = *(const int *)v1p, v2 = *(const int *)v2p;

  /* Note that the quotient will never be bigger than

     the value of floor_log2 times the maximum number of

     times a register can occur in one insn (surely less than 100)

     weighted by the frequency (maximally REG_FREQ_MAX).

     Multiplying this by 10000/REG_FREQ_MAX can't overflow.  */

  int pri1

    = (((double) (floor_log2 (allocno[v1].n_refs) * allocno[v1].freq)

        / allocno[v1].live_length)

       * (10000 / REG_FREQ_MAX) * allocno[v1].size);

  int pri2

    = (((double) (floor_log2 (allocno[v2].n_refs) * allocno[v2].freq)

        / allocno[v2].live_length)

       * (10000 / REG_FREQ_MAX) * allocno[v2].size);

  if (pri2 - pri1)

    return pri2 - pri1;

  /* If regs are equally good, sort by allocno,

     so that the results of qsort leave nothing to chance.  */

  return v1 - v2;

}

/* Scan the rtl code and record all conflicts and register preferences in the

   conflict matrices and preference tables.  */

static void

global_conflicts (void)

{

  unsigned i;

  basic_block b;

  rtx insn;

  int *block_start_allocnos;

  /* Make a vector that mark_reg_{store,clobber} will store in.  */

  regs_set = xmalloc (max_parallel * sizeof (rtx) * 2);

  block_start_allocnos = xmalloc (max_allocno * sizeof (int));

  FOR_EACH_BB (b)

    {

      memset (allocnos_live, 0, allocno_row_words * sizeof (INT_TYPE));

      /* Initialize table of registers currently live

         to the state at the beginning of this basic block.

         This also marks the conflicts among hard registers

         and any allocnos that are live.

         For pseudo-regs, there is only one bit for each one

         no matter how many hard regs it occupies.

         This is ok; we know the size from PSEUDO_REGNO_SIZE.

         For explicit hard regs, we cannot know the size that way

         since one hard reg can be used with various sizes.

         Therefore, we must require that all the hard regs

         implicitly live as part of a multi-word hard reg

         be explicitly marked in basic_block_live_at_start.  */