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/* Register renaming for the GNU compiler.

   Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,

   2010 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 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/>.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "rtl.h"

#include "tm_p.h"

#include "insn-config.h"

#include "regs.h"

#include "addresses.h"

#include "hard-reg-set.h"

#include "basic-block.h"

#include "reload.h"

#include "output.h"

#include "function.h"

#include "recog.h"

#include "flags.h"

#include "toplev.h"

#include "obstack.h"

#include "timevar.h"

#include "tree-pass.h"

#include "df.h"

#if HOST_BITS_PER_WIDE_INT <= MAX_RECOG_OPERANDS

#error "Use a different bitmap implementation for untracked_operands."

#endif

/* We keep linked lists of DU_HEAD structures, each of which describes

   a chain of occurrences of a reg.  */

struct du_head

{

  /* The next chain.  */

  struct du_head *next_chain;

  /* The first and last elements of this chain.  */

  struct du_chain *first, *last;

  /* Describes the register being tracked.  */

  unsigned regno, nregs;

  /* A unique id to be used as an index into the conflicts bitmaps.  */

  unsigned id;

  /* A bitmap to record conflicts with other chains.  */

  bitmap_head conflicts;

  /* Conflicts with untracked hard registers.  */

  HARD_REG_SET hard_conflicts;

  /* Nonzero if the chain is finished; zero if it is still open.  */

  unsigned int terminated:1;

  /* Nonzero if the chain crosses a call.  */

  unsigned int need_caller_save_reg:1;

  /* Nonzero if the register is used in a way that prevents renaming,

     such as the SET_DEST of a CALL_INSN or an asm operand that used

     to be a hard register.  */

  unsigned int cannot_rename:1;

};

/* This struct describes a single occurrence of a register.  */

struct du_chain

{

  /* Links to the next occurrence of the register.  */

  struct du_chain *next_use;

  /* The insn where the register appears.  */

  rtx insn;

  /* The location inside the insn.  */

  rtx *loc;

  /* The register class required by the insn at this location.  */

  ENUM_BITFIELD(reg_class) cl : 16;

};

enum scan_actions

{

  terminate_write,

  terminate_dead,

  mark_all_read,

  mark_read,

  mark_write,

  /* mark_access is for marking the destination regs in

     REG_FRAME_RELATED_EXPR notes (as if they were read) so that the

     note is updated properly.  */

  mark_access

};

static const char * const scan_actions_name[] =

{

  "terminate_write",

  "terminate_dead",

  "mark_all_read",

  "mark_read",

  "mark_write",

  "mark_access"

};

static struct obstack rename_obstack;

static void do_replace (struct du_head *, int);

static void scan_rtx_reg (rtx, rtx *, enum reg_class,

                          enum scan_actions, enum op_type);

static void scan_rtx_address (rtx, rtx *, enum reg_class,

                              enum scan_actions, enum machine_mode);

static void scan_rtx (rtx, rtx *, enum reg_class, enum scan_actions,

                      enum op_type);

static struct du_head *build_def_use (basic_block);

static void dump_def_use_chain (struct du_head *);

typedef struct du_head *du_head_p;

DEF_VEC_P (du_head_p);

DEF_VEC_ALLOC_P (du_head_p, heap);

static VEC(du_head_p, heap) *id_to_chain;

static void

free_chain_data (void)

{

  int i;

  du_head_p ptr;

  for (i = 0; VEC_iterate(du_head_p, id_to_chain, i, ptr); i++)

    bitmap_clear (&ptr->conflicts);

  VEC_free (du_head_p, heap, id_to_chain);

}

/* For a def-use chain HEAD, find which registers overlap its lifetime and

   set the corresponding bits in *PSET.  */

static void

merge_overlapping_regs (HARD_REG_SET *pset, struct du_head *head)

{

  bitmap_iterator bi;

  unsigned i;

  IOR_HARD_REG_SET (*pset, head->hard_conflicts);

  EXECUTE_IF_SET_IN_BITMAP (&head->conflicts, 0, i, bi)

    {

      du_head_p other = VEC_index (du_head_p, id_to_chain, i);

      unsigned j = other->nregs;

      while (j-- > 0)

        SET_HARD_REG_BIT (*pset, other->regno + j);

    }

}

/* Perform register renaming on the current function.  */

static unsigned int

regrename_optimize (void)

{

  int tick[FIRST_PSEUDO_REGISTER];

  int this_tick = 0;

  basic_block bb;

  char *first_obj;

  df_set_flags (DF_LR_RUN_DCE);

  df_note_add_problem ();

  df_analyze ();

  df_set_flags (DF_DEFER_INSN_RESCAN);

  memset (tick, 0, sizeof tick);

  gcc_obstack_init (&rename_obstack);

  first_obj = XOBNEWVAR (&rename_obstack, char, 0);

  FOR_EACH_BB (bb)

    {

      struct du_head *all_chains = 0;

      HARD_REG_SET unavailable;

#if 0

      HARD_REG_SET regs_seen;

      CLEAR_HARD_REG_SET (regs_seen);

#endif

      id_to_chain = VEC_alloc (du_head_p, heap, 0);

      CLEAR_HARD_REG_SET (unavailable);

      if (dump_file)

        fprintf (dump_file, "\nBasic block %d:\n", bb->index);

      all_chains = build_def_use (bb);

      if (dump_file)

        dump_def_use_chain (all_chains);

      CLEAR_HARD_REG_SET (unavailable);

      /* Don't clobber traceback for noreturn functions.  */

      if (frame_pointer_needed)

        {

          add_to_hard_reg_set (&unavailable, Pmode, FRAME_POINTER_REGNUM);

#if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM

          add_to_hard_reg_set (&unavailable, Pmode, HARD_FRAME_POINTER_REGNUM);

#endif

        }

      while (all_chains)

        {

          int new_reg, best_new_reg, best_nregs;

          int n_uses;

          struct du_head *this_head = all_chains;

          struct du_chain *tmp;

          HARD_REG_SET this_unavailable;

          int reg = this_head->regno;

          int i;

          all_chains = this_head->next_chain;

          if (this_head->cannot_rename)

            continue;

          best_new_reg = reg;

          best_nregs = this_head->nregs;

#if 0 /* This just disables optimization opportunities.  */

          /* Only rename once we've seen the reg more than once.  */

          if (! TEST_HARD_REG_BIT (regs_seen, reg))

            {

              SET_HARD_REG_BIT (regs_seen, reg);

              continue;

            }

#endif

          if (fixed_regs[reg] || global_regs[reg]

#if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM

              || (frame_pointer_needed && reg == HARD_FRAME_POINTER_REGNUM)

#else

              || (frame_pointer_needed && reg == FRAME_POINTER_REGNUM)

#endif

              )

            continue;

          COPY_HARD_REG_SET (this_unavailable, unavailable);

          /* Count number of uses, and narrow the set of registers we can

             use for renaming.  */

          n_uses = 0;

          for (tmp = this_head->first; tmp; tmp = tmp->next_use)

            {

              if (DEBUG_INSN_P (tmp->insn))

                continue;

              n_uses++;

              IOR_COMPL_HARD_REG_SET (this_unavailable,

                                      reg_class_contents[tmp->cl]);

            }

          if (n_uses < 2)

            continue;

          if (this_head->need_caller_save_reg)

            IOR_HARD_REG_SET (this_unavailable, call_used_reg_set);

          merge_overlapping_regs (&this_unavailable, this_head);

          /* Now potential_regs is a reasonable approximation, let's

             have a closer look at each register still in there.  */

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

            {

              enum machine_mode mode = GET_MODE (*this_head->first->loc);

              int nregs = hard_regno_nregs[new_reg][mode];

              for (i = nregs - 1; i >= 0; --i)

                if (TEST_HARD_REG_BIT (this_unavailable, new_reg + i)

                    || fixed_regs[new_reg + i]

                    || global_regs[new_reg + i]

                    /* Can't use regs which aren't saved by the prologue.  */

                    || (! df_regs_ever_live_p (new_reg + i)

                        && ! call_used_regs[new_reg + i])

#ifdef LEAF_REGISTERS

                    /* We can't use a non-leaf register if we're in a

                       leaf function.  */

                    || (current_function_is_leaf

                        && !LEAF_REGISTERS[new_reg + i])

#endif

#ifdef HARD_REGNO_RENAME_OK

                    || ! HARD_REGNO_RENAME_OK (reg + i, new_reg + i)

#endif

                    )

                  break;

              if (i >= 0)

                continue;

              /* See whether it accepts all modes that occur in

                 definition and uses.  */

              for (tmp = this_head->first; tmp; tmp = tmp->next_use)

                if ((! HARD_REGNO_MODE_OK (new_reg, GET_MODE (*tmp->loc))

                     && ! DEBUG_INSN_P (tmp->insn))

                    || (this_head->need_caller_save_reg

                        && ! (HARD_REGNO_CALL_PART_CLOBBERED

                              (reg, GET_MODE (*tmp->loc)))

                        && (HARD_REGNO_CALL_PART_CLOBBERED

                            (new_reg, GET_MODE (*tmp->loc)))))

                  break;

              if (! tmp)

                {

                  if (tick[best_new_reg] > tick[new_reg])

                    {

                      best_new_reg = new_reg;

                      best_nregs = nregs;

                    }

                }

            }

          if (dump_file)

            {

              fprintf (dump_file, "Register %s in insn %d",

                       reg_names[reg], INSN_UID (this_head->first->insn));

              if (this_head->need_caller_save_reg)

                fprintf (dump_file, " crosses a call");

            }

          if (best_new_reg == reg)

            {

              tick[reg] = ++this_tick;

              if (dump_file)

                fprintf (dump_file, "; no available better choice\n");

              continue;

            }

          if (dump_file)

            fprintf (dump_file, ", renamed as %s\n", reg_names[best_new_reg]);

          do_replace (this_head, best_new_reg);

          this_head->regno = best_new_reg;

          this_head->nregs = best_nregs;

          tick[best_new_reg] = ++this_tick;

          df_set_regs_ever_live (best_new_reg, true);

        }

      free_chain_data ();

      obstack_free (&rename_obstack, first_obj);

    }

  obstack_free (&rename_obstack, NULL);

  if (dump_file)

    fputc ('\n', dump_file);

  return 0;

}

static void

do_replace (struct du_head *head, int reg)

{

  struct du_chain *chain;

  unsigned int base_regno = head->regno;

  bool found_note = false;

  gcc_assert (! DEBUG_INSN_P (head->first->insn));

  for (chain = head->first; chain; chain = chain->next_use)

    {

      unsigned int regno = ORIGINAL_REGNO (*chain->loc);

      struct reg_attrs *attr = REG_ATTRS (*chain->loc);

      int reg_ptr = REG_POINTER (*chain->loc);

      if (DEBUG_INSN_P (chain->insn) && REGNO (*chain->loc) != base_regno)

        INSN_VAR_LOCATION_LOC (chain->insn) = gen_rtx_UNKNOWN_VAR_LOC ();

      else

        {

          rtx note;

          *chain->loc = gen_raw_REG (GET_MODE (*chain->loc), reg);

          if (regno >= FIRST_PSEUDO_REGISTER)

            ORIGINAL_REGNO (*chain->loc) = regno;

          REG_ATTRS (*chain->loc) = attr;

          REG_POINTER (*chain->loc) = reg_ptr;

          for (note = REG_NOTES (chain->insn); note; note = XEXP (note, 1))

            {

              enum reg_note kind = REG_NOTE_KIND (note);

              if (kind == REG_DEAD || kind == REG_UNUSED)

                {

                  rtx reg = XEXP (note, 0);

                  gcc_assert (HARD_REGISTER_P (reg));

                  if (REGNO (reg) == base_regno)

                    {

                      found_note = true;

                      if (kind == REG_DEAD

                          && reg_set_p (*chain->loc, chain->insn))

                        remove_note (chain->insn, note);

                      else

                        XEXP (note, 0) = *chain->loc;

                      break;

                    }

                }

            }

        }

      df_insn_rescan (chain->insn);

    }

  if (!found_note)

    {

      /* If the chain's first insn is the same as the last, we should have

         found a REG_UNUSED note.  */

      gcc_assert (head->first->insn != head->last->insn);

      if (!reg_set_p (*head->last->loc, head->last->insn))

        add_reg_note (head->last->insn, REG_DEAD, *head->last->loc);

    }

}

/* Walk all chains starting with CHAINS and record that they conflict with

   another chain whose id is ID.  */

static void

mark_conflict (struct du_head *chains, unsigned id)

{

  while (chains)

    {

      bitmap_set_bit (&chains->conflicts, id);

      chains = chains->next_chain;

    }

}

/* True if we found a register with a size mismatch, which means that we

   can't track its lifetime accurately.  If so, we abort the current block

   without renaming.  */

static bool fail_current_block;

/* The id to be given to the next opened chain.  */

static unsigned current_id;

/* List of currently open chains, and closed chains that can be renamed.  */

static struct du_head *open_chains;

static struct du_head *closed_chains;

/* Bitmap of open chains.  The bits set always match the list found in

   open_chains.  */

static bitmap_head open_chains_set;

/* Record the registers being tracked in open_chains.  */

static HARD_REG_SET live_in_chains;

/* Record the registers that are live but not tracked.  The intersection

   between this and live_in_chains is empty.  */

static HARD_REG_SET live_hard_regs;

/* Return true if OP is a reg for which all bits are set in PSET, false

   if all bits are clear.

   In other cases, set fail_current_block and return false.  */

static bool

verify_reg_in_set (rtx op, HARD_REG_SET *pset)

{

  unsigned regno, nregs;

  bool all_live, all_dead;

  if (!REG_P (op))

    return false;

  regno = REGNO (op);

  nregs = hard_regno_nregs[regno][GET_MODE (op)];

  all_live = all_dead = true;

  while (nregs-- > 0)

    if (TEST_HARD_REG_BIT (*pset, regno + nregs))

      all_dead = false;

    else

      all_live = false;

  if (!all_dead && !all_live)

    {

      fail_current_block = true;

      return false;

    }

  return all_live;

}

/* Return true if OP is a reg that is being tracked already in some form.

   May set fail_current_block if it sees an unhandled case of overlap.  */

static bool

verify_reg_tracked (rtx op)

{

  return (verify_reg_in_set (op, &live_hard_regs)

          || verify_reg_in_set (op, &live_in_chains));

}

/* Called through note_stores.  DATA points to a rtx_code, either SET or

   CLOBBER, which tells us which kind of rtx to look at.  If we have a

   match, record the set register in live_hard_regs and in the hard_conflicts

   bitmap of open chains.  */

static void

note_sets_clobbers (rtx x, const_rtx set, void *data)

{

  enum rtx_code code = *(enum rtx_code *)data;

  struct du_head *chain;

  if (GET_CODE (x) == SUBREG)

    x = SUBREG_REG (x);

  if (!REG_P (x) || GET_CODE (set) != code)

    return;

  /* There must not be pseudos at this point.  */

  gcc_assert (HARD_REGISTER_P (x));

  add_to_hard_reg_set (&live_hard_regs, GET_MODE (x), REGNO (x));

  for (chain = open_chains; chain; chain = chain->next_chain)

    add_to_hard_reg_set (&chain->hard_conflicts, GET_MODE (x), REGNO (x));

}

/* Create a new chain for THIS_NREGS registers starting at THIS_REGNO,

   and record its occurrence in *LOC, which is being written to in INSN.

   This access requires a register of class CL.  */

static void

create_new_chain (unsigned this_regno, unsigned this_nregs, rtx *loc,

                  rtx insn, enum reg_class cl)

{

  struct du_head *head = XOBNEW (&rename_obstack, struct du_head);

  struct du_chain *this_du;

  int nregs;

  head->next_chain = open_chains;

  open_chains = head;

  head->regno = this_regno;

  head->nregs = this_nregs;

  head->need_caller_save_reg = 0;

  head->cannot_rename = 0;

  head->terminated = 0;

  VEC_safe_push (du_head_p, heap, id_to_chain, head);

  head->id = current_id++;

  bitmap_initialize (&head->conflicts, &bitmap_default_obstack);

  bitmap_copy (&head->conflicts, &open_chains_set);

  mark_conflict (open_chains, head->id);

  /* Since we're tracking this as a chain now, remove it from the

     list of conflicting live hard registers and track it in

     live_in_chains instead.  */

  nregs = head->nregs;

  while (nregs-- > 0)

    {

      SET_HARD_REG_BIT (live_in_chains, head->regno + nregs);

      CLEAR_HARD_REG_BIT (live_hard_regs, head->regno + nregs);

    }

  COPY_HARD_REG_SET (head->hard_conflicts, live_hard_regs);

  bitmap_set_bit (&open_chains_set, head->id);

  open_chains = head;

  if (dump_file)

    {

      fprintf (dump_file, "Creating chain %s (%d)",

               reg_names[head->regno], head->id);

      if (insn != NULL_RTX)

        fprintf (dump_file, " at insn %d", INSN_UID (insn));

      fprintf (dump_file, "\n");

    }

  if (insn == NULL_RTX)

    {

      head->first = head->last = NULL;

      return;

    }

  this_du = XOBNEW (&rename_obstack, struct du_chain);

  head->first = head->last = this_du;

  this_du->next_use = 0;

  this_du->loc = loc;

  this_du->insn = insn;

  this_du->cl = cl;

}

static void

scan_rtx_reg (rtx insn, rtx *loc, enum reg_class cl, enum scan_actions action,

              enum op_type type)

{

  struct du_head **p;

  rtx x = *loc;

  enum machine_mode mode = GET_MODE (x);

  unsigned this_regno = REGNO (x);

  unsigned this_nregs = hard_regno_nregs[this_regno][mode];

  if (action == mark_write)

    {

      if (type == OP_OUT)

        create_new_chain (this_regno, this_nregs, loc, insn, cl);

      return;

    }

  if ((type == OP_OUT) != (action == terminate_write || action == mark_access))

    return;

  for (p = &open_chains; *p;)

    {

      struct du_head *head = *p;

      struct du_head *next = head->next_chain;

      int exact_match = (head->regno == this_regno

                         && head->nregs == this_nregs);

      int superset = (this_regno <= head->regno

                      && this_regno + this_nregs >= head->regno + head->nregs);

      int subset = (this_regno >= head->regno

                      && this_regno + this_nregs <= head->regno + head->nregs);

      if (head->terminated

          || head->regno + head->nregs <= this_regno

          || this_regno + this_nregs <= head->regno)

        {

          p = &head->next_chain;

          continue;

        }

      if (action == mark_read || action == mark_access)

        {

          /* ??? Class NO_REGS can happen if the md file makes use of

             EXTRA_CONSTRAINTS to match registers.  Which is arguably

             wrong, but there we are.  */

          if (cl == NO_REGS || (!exact_match && !DEBUG_INSN_P (insn)))

            {

              if (dump_file)

                fprintf (dump_file,

                         "Cannot rename chain %s (%d) at insn %d (%s)\n",

                         reg_names[head->regno], head->id, INSN_UID (insn),

                         scan_actions_name[(int) action]);

              head->cannot_rename = 1;

              if (superset)

                {

                  unsigned nregs = this_nregs;

                  head->regno = this_regno;

                  head->nregs = this_nregs;

                  while (nregs-- > 0)

                    SET_HARD_REG_BIT (live_in_chains, head->regno + nregs);

                  if (dump_file)

                    fprintf (dump_file,

                             "Widening register in chain %s (%d) at insn %d\n",

                             reg_names[head->regno], head->id, INSN_UID (insn));

                }

              else if (!subset)

                {

                  fail_current_block = true;

                  if (dump_file)

                    fprintf (dump_file,

                             "Failing basic block due to unhandled overlap\n");

                }

            }

          else

            {

              struct du_chain *this_du;

              this_du = XOBNEW (&rename_obstack, struct du_chain);

              this_du->next_use = 0;

              this_du->loc = loc;

              this_du->insn = insn;

              this_du->cl = cl;

              if (head->first == NULL)

                head->first = this_du;

              else

                head->last->next_use = this_du;

              head->last = this_du;

            }

          /* Avoid adding the same location in a DEBUG_INSN multiple times,

             which could happen with non-exact overlap.  */

          if (DEBUG_INSN_P (insn))

            return;

          /* Otherwise, find any other chains that do not match exactly;

             ensure they all get marked unrenamable.  */

          p = &head->next_chain;

          continue;

        }

      /* Whether the terminated chain can be used for renaming

         depends on the action and this being an exact match.

         In either case, we remove this element from open_chains.  */

      if ((action == terminate_dead || action == terminate_write)

          && superset)

        {