text: /* Try to unroll loops, and split induction variables.
     Copyright (C) 1992, 1993, 1994, 1995, 1997, 1998, 1999, 2000, 2001, 2002
     Free Software Foundation, Inc.
     Contributed by James E. Wilson, Cygnus Support/UC Berkeley.
  
  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, 59 Temple Place - Suite 330, Boston, MA
  02111-1307, USA.  */
  
  /* Try to unroll a loop, and split induction variables.
  
     Loops for which the number of iterations can be calculated exactly are
     handled specially.  If the number of iterations times the insn_count is
     less than MAX_UNROLLED_INSNS, then the loop is unrolled completely.
     Otherwise, we try to unroll the loop a number of times modulo the number
     of iterations, so that only one exit test will be needed.  It is unrolled
     a number of times approximately equal to MAX_UNROLLED_INSNS divided by
     the insn count.
  
     Otherwise, if the number of iterations can be calculated exactly at
     run time, and the loop is always entered at the top, then we try to
     precondition the loop.  That is, at run time, calculate how many times
     the loop will execute, and then execute the loop body a few times so
     that the remaining iterations will be some multiple of 4 (or 2 if the
     loop is large).  Then fall through to a loop unrolled 4 (or 2) times,
     with only one exit test needed at the end of the loop.
  
     Otherwise, if the number of iterations can not be calculated exactly,
     not even at run time, then we still unroll the loop a number of times
     approximately equal to MAX_UNROLLED_INSNS divided by the insn count,
     but there must be an exit test after each copy of the loop body.
  
     For each induction variable, which is dead outside the loop (replaceable)
     or for which we can easily calculate the final value, if we can easily
     calculate its value at each place where it is set as a function of the
     current loop unroll count and the variable's value at loop entry, then
     the induction variable is split into `N' different variables, one for
     each copy of the loop body.  One variable is live across the backward
     branch, and the others are all calculated as a function of this variable.
     This helps eliminate data dependencies, and leads to further opportunities
     for cse.  */
  
  /* Possible improvements follow:  */
  
  /* ??? Add an extra pass somewhere to determine whether unrolling will
     give any benefit.  E.g. after generating all unrolled insns, compute the
     cost of all insns and compare against cost of insns in rolled loop.
  
     - On traditional architectures, unrolling a non-constant bound loop
       is a win if there is a giv whose only use is in memory addresses, the
       memory addresses can be split, and hence giv increments can be
       eliminated.
     - It is also a win if the loop is executed many times, and preconditioning
       can be performed for the loop.
     Add code to check for these and similar cases.  */
  
  /* ??? Improve control of which loops get unrolled.  Could use profiling
     info to only unroll the most commonly executed loops.  Perhaps have
     a user specifyable option to control the amount of code expansion,
     or the percent of loops to consider for unrolling.  Etc.  */
  
  /* ??? Look at the register copies inside the loop to see if they form a
     simple permutation.  If so, iterate the permutation until it gets back to
     the start state.  This is how many times we should unroll the loop, for
     best results, because then all register copies can be eliminated.
     For example, the lisp nreverse function should be unrolled 3 times
     while (this)
       {
         next = this->cdr;
         this->cdr = prev;
         prev = this;
         this = next;
       }
  
     ??? The number of times to unroll the loop may also be based on data
     references in the loop.  For example, if we have a loop that references
     x[i-1], x[i], and x[i+1], we should unroll it a multiple of 3 times.  */
  
  /* ??? Add some simple linear equation solving capability so that we can
     determine the number of loop iterations for more complex loops.
     For example, consider this loop from gdb
     #define SWAP_TARGET_AND_HOST(buffer,len)
       {
         char tmp;
         char *p = (char *) buffer;
         char *q = ((char *) buffer) + len - 1;
         int iterations = (len + 1) >> 1;
         int i;
         for (p; p < q; p++, q--;)
  	 {
  	   tmp = *q;
  	   *q = *p;
  	   *p = tmp;
  	 }
       }
     Note that:
       start value = p = &buffer + current_iteration
       end value   = q = &buffer + len - 1 - current_iteration
     Given the loop exit test of "p < q", then there must be "q - p" iterations,
     set equal to zero and solve for number of iterations:
       q - p = len - 1 - 2*current_iteration = 0
       current_iteration = (len - 1) / 2
     Hence, there are (len - 1) / 2 (rounded up to the nearest integer)
     iterations of this loop.  */
  
  /* ??? Currently, no labels are marked as loop invariant when doing loop
     unrolling.  This is because an insn inside the loop, that loads the address
     of a label inside the loop into a register, could be moved outside the loop
     by the invariant code motion pass if labels were invariant.  If the loop
     is subsequently unrolled, the code will be wrong because each unrolled
     body of the loop will use the same address, whereas each actually needs a
     different address.  A case where this happens is when a loop containing
     a switch statement is unrolled.
  
     It would be better to let labels be considered invariant.  When we
     unroll loops here, check to see if any insns using a label local to the
     loop were moved before the loop.  If so, then correct the problem, by
     moving the insn back into the loop, or perhaps replicate the insn before
     the loop, one copy for each time the loop is unrolled.  */
  
  #include "config.h"
  #include "system.h"
  #include "rtl.h"
  #include "tm_p.h"
  #include "insn-config.h"
  #include "integrate.h"
  #include "regs.h"
  #include "recog.h"
  #include "flags.h"
  #include "function.h"
  #include "expr.h"
  #include "loop.h"
  #include "toplev.h"
  #include "hard-reg-set.h"
  #include "basic-block.h"
  #include "predict.h"
  #include "params.h"
  
  /* The prime factors looked for when trying to unroll a loop by some
     number which is modulo the total number of iterations.  Just checking
     for these 4 prime factors will find at least one factor for 75% of
     all numbers theoretically.  Practically speaking, this will succeed
     almost all of the time since loops are generally a multiple of 2
     and/or 5.  */
  
  #define NUM_FACTORS 4
  
  static struct _factor { const int factor; int count; }
  factors[NUM_FACTORS] = { {2, 0}, {3, 0}, {5, 0}, {7, 0}};
  
  /* Describes the different types of loop unrolling performed.  */
  
  enum unroll_types
  {
    UNROLL_COMPLETELY,
    UNROLL_MODULO,
    UNROLL_NAIVE
  };
  
  /* Indexed by register number, if nonzero, then it contains a pointer
     to a struct induction for a DEST_REG giv which has been combined with
     one of more address givs.  This is needed because whenever such a DEST_REG
     giv is modified, we must modify the value of all split address givs
     that were combined with this DEST_REG giv.  */
  
  static struct induction **addr_combined_regs;
  
  /* Indexed by register number, if this is a splittable induction variable,
     then this will hold the current value of the register, which depends on the
     iteration number.  */
  
  static rtx *splittable_regs;
  
  /* Indexed by register number, if this is a splittable induction variable,
     then this will hold the number of instructions in the loop that modify
     the induction variable.  Used to ensure that only the last insn modifying
     a split iv will update the original iv of the dest.  */
  
  static int *splittable_regs_updates;
  
  /* Forward declarations.  */
  
  static rtx simplify_cmp_and_jump_insns PARAMS ((enum rtx_code,
  						enum machine_mode,
  						rtx, rtx, rtx));
  static void init_reg_map PARAMS ((struct inline_remap *, int));
  static rtx calculate_giv_inc PARAMS ((rtx, rtx, unsigned int));
  static rtx initial_reg_note_copy PARAMS ((rtx, struct inline_remap *));
  static void final_reg_note_copy PARAMS ((rtx *, struct inline_remap *));
  static void copy_loop_body PARAMS ((struct loop *, rtx, rtx,
  				    struct inline_remap *, rtx, int,
  				    enum unroll_types, rtx, rtx, rtx, rtx));
  static int find_splittable_regs PARAMS ((const struct loop *,
  					 enum unroll_types, int));
  static int find_splittable_givs PARAMS ((const struct loop *,
  					 struct iv_class *, enum unroll_types,
  					 rtx, int));
  static int reg_dead_after_loop PARAMS ((const struct loop *, rtx));
  static rtx fold_rtx_mult_add PARAMS ((rtx, rtx, rtx, enum machine_mode));
  static rtx remap_split_bivs PARAMS ((struct loop *, rtx));
  static rtx find_common_reg_term PARAMS ((rtx, rtx));
  static rtx subtract_reg_term PARAMS ((rtx, rtx));
  static rtx loop_find_equiv_value PARAMS ((const struct loop *, rtx));
  static rtx ujump_to_loop_cont PARAMS ((rtx, rtx));
  
  /* Try to unroll one loop and split induction variables in the loop.
  
     The loop is described by the arguments LOOP and INSN_COUNT.
     STRENGTH_REDUCTION_P indicates whether information generated in the
     strength reduction pass is available.
  
     This function is intended to be called from within `strength_reduce'
     in loop.c.  */
  
  void
  unroll_loop (loop, insn_count, strength_reduce_p)
       struct loop *loop;
       int insn_count;
       int strength_reduce_p;
  {
    struct loop_info *loop_info = LOOP_INFO (loop);
    struct loop_ivs *ivs = LOOP_IVS (loop);
    int i, j;
    unsigned int r;
    unsigned HOST_WIDE_INT temp;
    int unroll_number = 1;
    rtx copy_start, copy_end;
    rtx insn, sequence, pattern, tem;
    int max_labelno, max_insnno;
    rtx insert_before;
    struct inline_remap *map;
    char *local_label = NULL;
    char *local_regno;
    unsigned int max_local_regnum;
    unsigned int maxregnum;
    rtx exit_label = 0;
    rtx start_label;
    struct iv_class *bl;
    int splitting_not_safe = 0;
    enum unroll_types unroll_type = UNROLL_NAIVE;
    int loop_preconditioned = 0;
    rtx safety_label;
    /* This points to the last real insn in the loop, which should be either
       a JUMP_INSN (for conditional jumps) or a BARRIER (for unconditional
       jumps).  */
    rtx last_loop_insn;
    rtx loop_start = loop->start;
    rtx loop_end = loop->end;
  
    /* Don't bother unrolling huge loops.  Since the minimum factor is
       two, loops greater than one half of MAX_UNROLLED_INSNS will never
       be unrolled.  */
    if (insn_count > MAX_UNROLLED_INSNS / 2)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream, "Unrolling failure: Loop too big.\n");
        return;
      }
  
    /* Determine type of unroll to perform.  Depends on the number of iterations
       and the size of the loop.  */
  
    /* If there is no strength reduce info, then set
       loop_info->n_iterations to zero.  This can happen if
       strength_reduce can't find any bivs in the loop.  A value of zero
       indicates that the number of iterations could not be calculated.  */
  
    if (! strength_reduce_p)
      loop_info->n_iterations = 0;
  
    if (loop_dump_stream && loop_info->n_iterations > 0)
      {
        fputs ("Loop unrolling: ", loop_dump_stream);
        fprintf (loop_dump_stream, HOST_WIDE_INT_PRINT_DEC,
  	       loop_info->n_iterations);
        fputs (" iterations.\n", loop_dump_stream);
      }
  
    /* Find and save a pointer to the last nonnote insn in the loop.  */
  
    last_loop_insn = prev_nonnote_insn (loop_end);
  
    /* Calculate how many times to unroll the loop.  Indicate whether or
       not the loop is being completely unrolled.  */
  
    if (loop_info->n_iterations == 1)
      {
        /* Handle the case where the loop begins with an unconditional
  	 jump to the loop condition.  Make sure to delete the jump
  	 insn, otherwise the loop body will never execute.  */
  
        /* FIXME this actually checks for a jump to the continue point, which
  	 is not the same as the condition in a for loop.  As a result, this
  	 optimization fails for most for loops.  We should really use flow
  	 information rather than instruction pattern matching.  */
        rtx ujump = ujump_to_loop_cont (loop->start, loop->cont);
  
        /* If number of iterations is exactly 1, then eliminate the compare and
  	 branch at the end of the loop since they will never be taken.
  	 Then return, since no other action is needed here.  */
  
        /* If the last instruction is not a BARRIER or a JUMP_INSN, then
  	 don't do anything.  */
  
        if (GET_CODE (last_loop_insn) == BARRIER)
  	{
  	  /* Delete the jump insn.  This will delete the barrier also.  */
  	  last_loop_insn = PREV_INSN (last_loop_insn);
  	}
  
        if (ujump && GET_CODE (last_loop_insn) == JUMP_INSN)
  	{
  #ifdef HAVE_cc0
  	  rtx prev = PREV_INSN (last_loop_insn);
  #endif
  	  delete_related_insns (last_loop_insn);
  #ifdef HAVE_cc0
  	  /* The immediately preceding insn may be a compare which must be
  	     deleted.  */
  	  if (only_sets_cc0_p (prev))
  	    delete_related_insns (prev);
  #endif
  
  	  delete_related_insns (ujump);
  
  	  /* Remove the loop notes since this is no longer a loop.  */
  	  if (loop->vtop)
  	    delete_related_insns (loop->vtop);
  	  if (loop->cont)
  	    delete_related_insns (loop->cont);
  	  if (loop_start)
  	    delete_related_insns (loop_start);
  	  if (loop_end)
  	    delete_related_insns (loop_end);
  
  	  return;
  	}
      }
  
    if (loop_info->n_iterations > 0
        /* Avoid overflow in the next expression.  */
        && loop_info->n_iterations < (unsigned) MAX_UNROLLED_INSNS
        && loop_info->n_iterations * insn_count < (unsigned) MAX_UNROLLED_INSNS)
      {
        unroll_number = loop_info->n_iterations;
        unroll_type = UNROLL_COMPLETELY;
      }
    else if (loop_info->n_iterations > 0)
      {
        /* Try to factor the number of iterations.  Don't bother with the
  	 general case, only using 2, 3, 5, and 7 will get 75% of all
  	 numbers theoretically, and almost all in practice.  */
  
        for (i = 0; i < NUM_FACTORS; i++)
  	factors[i].count = 0;
  
        temp = loop_info->n_iterations;
        for (i = NUM_FACTORS - 1; i >= 0; i--)
  	while (temp % factors[i].factor == 0)
  	  {
  	    factors[i].count++;
  	    temp = temp / factors[i].factor;
  	  }
  
        /* Start with the larger factors first so that we generally
  	 get lots of unrolling.  */
  
        unroll_number = 1;
        temp = insn_count;
        for (i = 3; i >= 0; i--)
  	while (factors[i].count--)
  	  {
  	    if (temp * factors[i].factor < (unsigned) MAX_UNROLLED_INSNS)
  	      {
  		unroll_number *= factors[i].factor;
  		temp *= factors[i].factor;
  	      }
  	    else
  	      break;
  	  }
  
        /* If we couldn't find any factors, then unroll as in the normal
  	 case.  */
        if (unroll_number == 1)
  	{
  	  if (loop_dump_stream)
  	    fprintf (loop_dump_stream, "Loop unrolling: No factors found.\n");
  	}
        else
  	unroll_type = UNROLL_MODULO;
      }
  
    /* Default case, calculate number of times to unroll loop based on its
       size.  */
    if (unroll_type == UNROLL_NAIVE)
      {
        if (8 * insn_count < MAX_UNROLLED_INSNS)
  	unroll_number = 8;
        else if (4 * insn_count < MAX_UNROLLED_INSNS)
  	unroll_number = 4;
        else
  	unroll_number = 2;
      }
  
    /* Now we know how many times to unroll the loop.  */
  
    if (loop_dump_stream)
      fprintf (loop_dump_stream, "Unrolling loop %d times.\n", unroll_number);
  
    if (unroll_type == UNROLL_COMPLETELY || unroll_type == UNROLL_MODULO)
      {
        /* Loops of these types can start with jump down to the exit condition
  	 in rare circumstances.
  
  	 Consider a pair of nested loops where the inner loop is part
  	 of the exit code for the outer loop.
  
  	 In this case jump.c will not duplicate the exit test for the outer
  	 loop, so it will start with a jump to the exit code.
  
  	 Then consider if the inner loop turns out to iterate once and
  	 only once.  We will end up deleting the jumps associated with
  	 the inner loop.  However, the loop notes are not removed from
  	 the instruction stream.
  
  	 And finally assume that we can compute the number of iterations
  	 for the outer loop.
  
  	 In this case unroll may want to unroll the outer loop even though
  	 it starts with a jump to the outer loop's exit code.
  
  	 We could try to optimize this case, but it hardly seems worth it.
  	 Just return without unrolling the loop in such cases.  */
  
        insn = loop_start;
        while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
  	insn = NEXT_INSN (insn);
        if (GET_CODE (insn) == JUMP_INSN)
  	return;
      }
  
    if (unroll_type == UNROLL_COMPLETELY)
      {
        /* Completely unrolling the loop:  Delete the compare and branch at
  	 the end (the last two instructions).   This delete must done at the
  	 very end of loop unrolling, to avoid problems with calls to
  	 back_branch_in_range_p, which is called by find_splittable_regs.
  	 All increments of splittable bivs/givs are changed to load constant
  	 instructions.  */
  
        copy_start = loop_start;
  
        /* Set insert_before to the instruction immediately after the JUMP_INSN
  	 (or BARRIER), so that any NOTEs between the JUMP_INSN and the end of
  	 the loop will be correctly handled by copy_loop_body.  */
        insert_before = NEXT_INSN (last_loop_insn);
  
        /* Set copy_end to the insn before the jump at the end of the loop.  */
        if (GET_CODE (last_loop_insn) == BARRIER)
  	copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
        else if (GET_CODE (last_loop_insn) == JUMP_INSN)
  	{
  	  copy_end = PREV_INSN (last_loop_insn);
  #ifdef HAVE_cc0
  	  /* The instruction immediately before the JUMP_INSN may be a compare
  	     instruction which we do not want to copy.  */
  	  if (sets_cc0_p (PREV_INSN (copy_end)))
  	    copy_end = PREV_INSN (copy_end);
  #endif
  	}
        else
  	{
  	  /* We currently can't unroll a loop if it doesn't end with a
  	     JUMP_INSN.  There would need to be a mechanism that recognizes
  	     this case, and then inserts a jump after each loop body, which
  	     jumps to after the last loop body.  */
  	  if (loop_dump_stream)
  	    fprintf (loop_dump_stream,
  		     "Unrolling failure: loop does not end with a JUMP_INSN.\n");
  	  return;
  	}
      }
    else if (unroll_type == UNROLL_MODULO)
      {
        /* Partially unrolling the loop:  The compare and branch at the end
  	 (the last two instructions) must remain.  Don't copy the compare
  	 and branch instructions at the end of the loop.  Insert the unrolled
  	 code immediately before the compare/branch at the end so that the
  	 code will fall through to them as before.  */
  
        copy_start = loop_start;
  
        /* Set insert_before to the jump insn at the end of the loop.
  	 Set copy_end to before the jump insn at the end of the loop.  */
        if (GET_CODE (last_loop_insn) == BARRIER)
  	{
  	  insert_before = PREV_INSN (last_loop_insn);
  	  copy_end = PREV_INSN (insert_before);
  	}
        else if (GET_CODE (last_loop_insn) == JUMP_INSN)
  	{
  	  insert_before = last_loop_insn;
  #ifdef HAVE_cc0
  	  /* The instruction immediately before the JUMP_INSN may be a compare
  	     instruction which we do not want to copy or delete.  */
  	  if (sets_cc0_p (PREV_INSN (insert_before)))
  	    insert_before = PREV_INSN (insert_before);
  #endif
  	  copy_end = PREV_INSN (insert_before);
  	}
        else
  	{
  	  /* We currently can't unroll a loop if it doesn't end with a
  	     JUMP_INSN.  There would need to be a mechanism that recognizes
  	     this case, and then inserts a jump after each loop body, which
  	     jumps to after the last loop body.  */
  	  if (loop_dump_stream)
  	    fprintf (loop_dump_stream,
  		     "Unrolling failure: loop does not end with a JUMP_INSN.\n");
  	  return;
  	}
      }
    else
      {
        /* Normal case: Must copy the compare and branch instructions at the
  	 end of the loop.  */
  
        if (GET_CODE (last_loop_insn) == BARRIER)
  	{
  	  /* Loop ends with an unconditional jump and a barrier.
  	     Handle this like above, don't copy jump and barrier.
  	     This is not strictly necessary, but doing so prevents generating
  	     unconditional jumps to an immediately following label.
  
  	     This will be corrected below if the target of this jump is
  	     not the start_label.  */
  
  	  insert_before = PREV_INSN (last_loop_insn);
  	  copy_end = PREV_INSN (insert_before);
  	}
        else if (GET_CODE (last_loop_insn) == JUMP_INSN)
  	{
  	  /* Set insert_before to immediately after the JUMP_INSN, so that
  	     NOTEs at the end of the loop will be correctly handled by
  	     copy_loop_body.  */
  	  insert_before = NEXT_INSN (last_loop_insn);
  	  copy_end = last_loop_insn;
  	}
        else
  	{
  	  /* We currently can't unroll a loop if it doesn't end with a
  	     JUMP_INSN.  There would need to be a mechanism that recognizes
  	     this case, and then inserts a jump after each loop body, which
  	     jumps to after the last loop body.  */
  	  if (loop_dump_stream)
  	    fprintf (loop_dump_stream,
  		     "Unrolling failure: loop does not end with a JUMP_INSN.\n");
  	  return;
  	}
  
        /* If copying exit test branches because they can not be eliminated,
  	 then must convert the fall through case of the branch to a jump past
  	 the end of the loop.  Create a label to emit after the loop and save
  	 it for later use.  Do not use the label after the loop, if any, since
  	 it might be used by insns outside the loop, or there might be insns
  	 added before it later by final_[bg]iv_value which must be after
  	 the real exit label.  */
        exit_label = gen_label_rtx ();
  
        insn = loop_start;
        while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
  	insn = NEXT_INSN (insn);
  
        if (GET_CODE (insn) == JUMP_INSN)
  	{
  	  /* The loop starts with a jump down to the exit condition test.
  	     Start copying the loop after the barrier following this
  	     jump insn.  */
  	  copy_start = NEXT_INSN (insn);
  
  	  /* Splitting induction variables doesn't work when the loop is
  	     entered via a jump to the bottom, because then we end up doing
  	     a comparison against a new register for a split variable, but
  	     we did not execute the set insn for the new register because
  	     it was skipped over.  */
  	  splitting_not_safe = 1;
  	  if (loop_dump_stream)
  	    fprintf (loop_dump_stream,
  		     "Splitting not safe, because loop not entered at top.\n");
  	}
        else
  	copy_start = loop_start;
      }
  
    /* This should always be the first label in the loop.  */
    start_label = NEXT_INSN (copy_start);
    /* There may be a line number note and/or a loop continue note here.  */
    while (GET_CODE (start_label) == NOTE)
      start_label = NEXT_INSN (start_label);
    if (GET_CODE (start_label) != CODE_LABEL)
      {
        /* This can happen as a result of jump threading.  If the first insns in
  	 the loop test the same condition as the loop's backward jump, or the
  	 opposite condition, then the backward jump will be modified to point
  	 to elsewhere, and the loop's start label is deleted.
  
  	 This case currently can not be handled by the loop unrolling code.  */
  
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Unrolling failure: unknown insns between BEG note and loop label.\n");
        return;
      }
    if (LABEL_NAME (start_label))
      {
        /* The jump optimization pass must have combined the original start label
  	 with a named label for a goto.  We can't unroll this case because
  	 jumps which go to the named label must be handled differently than
  	 jumps to the loop start, and it is impossible to differentiate them
  	 in this case.  */
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Unrolling failure: loop start label is gone\n");
        return;
      }
  
    if (unroll_type == UNROLL_NAIVE
        && GET_CODE (last_loop_insn) == BARRIER
        && GET_CODE (PREV_INSN (last_loop_insn)) == JUMP_INSN
        && start_label != JUMP_LABEL (PREV_INSN (last_loop_insn)))
      {
        /* In this case, we must copy the jump and barrier, because they will
  	 not be converted to jumps to an immediately following label.  */
  
        insert_before = NEXT_INSN (last_loop_insn);
        copy_end = last_loop_insn;
      }
  
    if (unroll_type == UNROLL_NAIVE
        && GET_CODE (last_loop_insn) == JUMP_INSN
        && start_label != JUMP_LABEL (last_loop_insn))
      {
        /* ??? The loop ends with a conditional branch that does not branch back
  	 to the loop start label.  In this case, we must emit an unconditional
  	 branch to the loop exit after emitting the final branch.
  	 copy_loop_body does not have support for this currently, so we
  	 give up.  It doesn't seem worthwhile to unroll anyways since
  	 unrolling would increase the number of branch instructions
  	 executed.  */
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Unrolling failure: final conditional branch not to loop start\n");
        return;
      }
  
    /* Allocate a translation table for the labels and insn numbers.
       They will be filled in as we copy the insns in the loop.  */
  
    max_labelno = max_label_num ();
    max_insnno = get_max_uid ();
  
    /* Various paths through the unroll code may reach the "egress" label
       without initializing fields within the map structure.
  
       To be safe, we use xcalloc to zero the memory.  */
    map = (struct inline_remap *) xcalloc (1, sizeof (struct inline_remap));
  
    /* Allocate the label map.  */
  
    if (max_labelno > 0)
      {
        map->label_map = (rtx *) xcalloc (max_labelno, sizeof (rtx));
        local_label = (char *) xcalloc (max_labelno, sizeof (char));
      }
  
    /* Search the loop and mark all local labels, i.e. the ones which have to
       be distinct labels when copied.  For all labels which might be
       non-local, set their label_map entries to point to themselves.
       If they happen to be local their label_map entries will be overwritten
       before the loop body is copied.  The label_map entries for local labels
       will be set to a different value each time the loop body is copied.  */
  
    for (insn = copy_start; insn != loop_end; insn = NEXT_INSN (insn))
      {
        rtx note;
  
        if (GET_CODE (insn) == CODE_LABEL)
  	local_label[CODE_LABEL_NUMBER (insn)] = 1;
        else if (GET_CODE (insn) == JUMP_INSN)
  	{
  	  if (JUMP_LABEL (insn))
  	    set_label_in_map (map,
  			      CODE_LABEL_NUMBER (JUMP_LABEL (insn)),
  			      JUMP_LABEL (insn));
  	  else if (GET_CODE (PATTERN (insn)) == ADDR_VEC
  		   || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
  	    {
  	      rtx pat = PATTERN (insn);
  	      int diff_vec_p = GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC;
  	      int len = XVECLEN (pat, diff_vec_p);
  	      rtx label;
  
  	      for (i = 0; i < len; i++)
  		{
  		  label = XEXP (XVECEXP (pat, diff_vec_p, i), 0);
  		  set_label_in_map (map, CODE_LABEL_NUMBER (label), label);
  		}
  	    }
  	}
        if ((note = find_reg_note (insn, REG_LABEL, NULL_RTX)))
  	set_label_in_map (map, CODE_LABEL_NUMBER (XEXP (note, 0)),
  			  XEXP (note, 0));
      }
  
    /* Allocate space for the insn map.  */
  
    map->insn_map = (rtx *) xmalloc (max_insnno * sizeof (rtx));
  
    /* Set this to zero, to indicate that we are doing loop unrolling,
       not function inlining.  */
    map->inline_target = 0;
  
    /* The register and constant maps depend on the number of registers
       present, so the final maps can't be created until after
       find_splittable_regs is called.  However, they are needed for
       preconditioning, so we create temporary maps when preconditioning
       is performed.  */
  
    /* The preconditioning code may allocate two new pseudo registers.  */
    maxregnum = max_reg_num ();
  
    /* local_regno is only valid for regnos < max_local_regnum.  */
    max_local_regnum = maxregnum;
  
    /* Allocate and zero out the splittable_regs and addr_combined_regs
       arrays.  These must be zeroed here because they will be used if
       loop preconditioning is performed, and must be zero for that case.
  
       It is safe to do this here, since the extra registers created by the
       preconditioning code and find_splittable_regs will never be used
       to access the splittable_regs[] and addr_combined_regs[] arrays.  */
  
    splittable_regs = (rtx *) xcalloc (maxregnum, sizeof (rtx));
    splittable_regs_updates = (int *) xcalloc (maxregnum, sizeof (int));
    addr_combined_regs
      = (struct induction **) xcalloc (maxregnum, sizeof (struct induction *));
    local_regno = (char *) xcalloc (maxregnum, sizeof (char));
  
    /* Mark all local registers, i.e. the ones which are referenced only
       inside the loop.  */
    if (INSN_UID (copy_end) < max_uid_for_loop)
      {
        int copy_start_luid = INSN_LUID (copy_start);
        int copy_end_luid = INSN_LUID (copy_end);
  
        /* If a register is used in the jump insn, we must not duplicate it
  	 since it will also be used outside the loop.  */
        if (GET_CODE (copy_end) == JUMP_INSN)
  	copy_end_luid--;
  
        /* If we have a target that uses cc0, then we also must not duplicate
  	 the insn that sets cc0 before the jump insn, if one is present.  */
  #ifdef HAVE_cc0
        if (GET_CODE (copy_end) == JUMP_INSN
  	  && sets_cc0_p (PREV_INSN (copy_end)))
  	copy_end_luid--;
  #endif
  
        /* If copy_start points to the NOTE that starts the loop, then we must
  	 use the next luid, because invariant pseudo-regs moved out of the loop
  	 have their lifetimes modified to start here, but they are not safe
  	 to duplicate.  */
        if (copy_start == loop_start)
  	copy_start_luid++;
  
        /* If a pseudo's lifetime is entirely contained within this loop, then we
  	 can use a different pseudo in each unrolled copy of the loop.  This
  	 results in better code.  */
        /* We must limit the generic test to max_reg_before_loop, because only
  	 these pseudo registers have valid regno_first_uid info.  */
        for (r = FIRST_PSEUDO_REGISTER; r < max_reg_before_loop; ++r)
  	if (REGNO_FIRST_UID (r) > 0 && REGNO_FIRST_UID (r) < max_uid_for_loop
  	    && REGNO_FIRST_LUID (r) >= copy_start_luid
  	    && REGNO_LAST_UID (r) > 0 && REGNO_LAST_UID (r) < max_uid_for_loop
  	    && REGNO_LAST_LUID (r) <= copy_end_luid)
  	  {
  	    /* However, we must also check for loop-carried dependencies.
  	       If the value the pseudo has at the end of iteration X is
  	       used by iteration X+1, then we can not use a different pseudo
  	       for each unrolled copy of the loop.  */
  	    /* A pseudo is safe if regno_first_uid is a set, and this
  	       set dominates all instructions from regno_first_uid to
  	       regno_last_uid.  */
  	    /* ??? This check is simplistic.  We would get better code if
  	       this check was more sophisticated.  */
  	    if (set_dominates_use (r, REGNO_FIRST_UID (r), REGNO_LAST_UID (r),
  				   copy_start, copy_end))
  	      local_regno[r] = 1;
  
  	    if (loop_dump_stream)
  	      {
  		if (local_regno[r])
  		  fprintf (loop_dump_stream, "Marked reg %d as local\n", r);
  		else
  		  fprintf (loop_dump_stream, "Did not mark reg %d as local\n",
  			   r);
  	      }
  	  }
      }
  
    /* If this loop requires exit tests when unrolled, check to see if we
       can precondition the loop so as to make the exit tests unnecessary.
       Just like variable splitting, this is not safe if the loop is entered
       via a jump to the bottom.  Also, can not do this if no strength
       reduce info, because precondition_loop_p uses this info.  */
  
    /* Must copy the loop body for preconditioning before the following
       find_splittable_regs call since that will emit insns which need to
       be after the preconditioned loop copies, but immediately before the
       unrolled loop copies.  */
  
    /* Also, it is not safe to split induction variables for the preconditioned
       copies of the loop body.  If we split induction variables, then the code
       assumes that each induction variable can be represented as a function
       of its initial value and the loop iteration number.  This is not true
       in this case, because the last preconditioned copy of the loop body
       could be any iteration from the first up to the `unroll_number-1'th,
       depending on the initial value of the iteration variable.  Therefore
       we can not split induction variables here, because we can not calculate
       their value.  Hence, this code must occur before find_splittable_regs
       is called.  */
  
    if (unroll_type == UNROLL_NAIVE && ! splitting_not_safe && strength_reduce_p)
      {
        rtx initial_value, final_value, increment;
        enum machine_mode mode;
  
        if (precondition_loop_p (loop,
  			       &initial_value, &final_value, &increment,
  			       &mode))
  	{
  	  rtx diff, insn;
  	  rtx *labels;
  	  int abs_inc, neg_inc;
  	  enum rtx_code cc = loop_info->comparison_code;
  	  int less_p     = (cc == LE  || cc == LEU || cc == LT  || cc == LTU);
  	  int unsigned_p = (cc == LEU || cc == GEU || cc == LTU || cc == GTU);
  
  	  map->reg_map = (rtx *) xmalloc (maxregnum * sizeof (rtx));
  
  	  VARRAY_CONST_EQUIV_INIT (map->const_equiv_varray, maxregnum,
  				   "unroll_loop_precondition");
  	  global_const_equiv_varray = map->const_equiv_varray;
  
  	  init_reg_map (map, maxregnum);
  
  	  /* Limit loop unrolling to 4, since this will make 7 copies of
  	     the loop body.  */
  	  if (unroll_number > 4)
  	    unroll_number = 4;
  
  	  /* Save the absolute value of the increment, and also whether or
  	     not it is negative.  */
  	  neg_inc = 0;
  	  abs_inc = INTVAL (increment);
  	  if (abs_inc < 0)
  	    {
  	      abs_inc = -abs_inc;
  	      neg_inc = 1;
  	    }
  
  	  start_sequence ();
  
  	  /* We must copy the final and initial values here to avoid
  	     improperly shared rtl.  */
  	  final_value = copy_rtx (final_value);
  	  initial_value = copy_rtx (initial_value);
  
  	  /* Final value may have form of (PLUS val1 const1_rtx).  We need
  	     to convert it into general operand, so compute the real value.  */
  
  	  final_value = force_operand (final_value, NULL_RTX);
  	  if (!nonmemory_operand (final_value, VOIDmode))
  	    final_value = force_reg (mode, final_value);
  
  	  /* Calculate the difference between the final and initial values.
  	     Final value may be a (plus (reg x) (const_int 1)) rtx.
  
  	     We have to deal with for (i = 0; --i < 6;) type loops.
  	     For such loops the real final value is the first time the
  	     loop variable overflows, so the diff we calculate is the
  	     distance from the overflow value.  This is 0 or ~0 for
  	     unsigned loops depending on the direction, or INT_MAX,
  	     INT_MAX+1 for signed loops.  We really do not need the
  	     exact value, since we are only interested in the diff
  	     modulo the increment, and the increment is a power of 2,
  	     so we can pretend that the overflow value is 0/~0.  */
  
  	  if (cc == NE || less_p != neg_inc)
  	    diff = simplify_gen_binary (MINUS, mode, final_value,
  					initial_value);
  	  else
  	    diff = simplify_gen_unary (neg_inc ? NOT : NEG, mode,
  				       initial_value, mode);
  	  diff = force_operand (diff, NULL_RTX);
  
  	  /* Now calculate (diff % (unroll * abs (increment))) by using an
  	     and instruction.  */
  	  diff = simplify_gen_binary (AND, mode, diff,
  				      GEN_INT (unroll_number*abs_inc - 1));
  	  diff = force_operand (diff, NULL_RTX);
  
  	  /* Now emit a sequence of branches to jump to the proper precond
  	     loop entry point.  */
  
  	  labels = (rtx *) xmalloc (sizeof (rtx) * unroll_number);
  	  for (i = 0; i < unroll_number; i++)
  	    labels[i] = gen_label_rtx ();
  
  	  /* Check for the case where the initial value is greater than or
  	     equal to the final value.  In that case, we want to execute
  	     exactly one loop iteration.  The code below will fail for this
  	     case.  This check does not apply if the loop has a NE
  	     comparison at the end.  */
  
  	  if (cc != NE)
  	    {
  	      rtx incremented_initval;
  	      enum rtx_code cmp_code;
  
  	      incremented_initval
  		= simplify_gen_binary (PLUS, mode, initial_value, increment);
  	      incremented_initval
  		= force_operand (incremented_initval, NULL_RTX);
  
  	      cmp_code = (less_p
  			  ? (unsigned_p ? GEU : GE)
  			  : (unsigned_p ? LEU : LE));
  
  	      insn = simplify_cmp_and_jump_insns (cmp_code, mode,
  						  incremented_initval,
  						  final_value, labels[1]);
  	      if (insn)
  	        predict_insn_def (insn, PRED_LOOP_CONDITION, TAKEN);
  	    }
  
  	  /* Assuming the unroll_number is 4, and the increment is 2, then
  	     for a negative increment:	for a positive increment:
  	     diff = 0,1   precond 0	diff = 0,7   precond 0
  	     diff = 2,3   precond 3     diff = 1,2   precond 1
  	     diff = 4,5   precond 2     diff = 3,4   precond 2
  	     diff = 6,7   precond 1     diff = 5,6   precond 3  */
  
  	  /* We only need to emit (unroll_number - 1) branches here, the
  	     last case just falls through to the following code.  */
  
  	  /* ??? This would give better code if we emitted a tree of branches
  	     instead of the current linear list of branches.  */
  
  	  for (i = 0; i < unroll_number - 1; i++)
  	    {
  	      int cmp_const;
  	      enum rtx_code cmp_code;
  
  	      /* For negative increments, must invert the constant compared
  		 against, except when comparing against zero.  */
  	      if (i == 0)
  		{
  		  cmp_const = 0;
  		  cmp_code = EQ;
  		}
  	      else if (neg_inc)
  		{
  		  cmp_const = unroll_number - i;
  		  cmp_code = GE;
  		}
  	      else
  		{
  		  cmp_const = i;
  		  cmp_code = LE;
  		}
  
  	      insn = simplify_cmp_and_jump_insns (cmp_code, mode, diff,
  						  GEN_INT (abs_inc*cmp_const),
  						  labels[i]);
  	      if (insn)
  	        predict_insn (insn, PRED_LOOP_PRECONDITIONING,
  			      REG_BR_PROB_BASE / (unroll_number - i));
  	    }
  
  	  /* If the increment is greater than one, then we need another branch,
  	     to handle other cases equivalent to 0.  */
  
  	  /* ??? This should be merged into the code above somehow to help
  	     simplify the code here, and reduce the number of branches emitted.
  	     For the negative increment case, the branch here could easily
  	     be merged with the `0' case branch above.  For the positive
  	     increment case, it is not clear how this can be simplified.  */
  
  	  if (abs_inc != 1)
  	    {
  	      int cmp_const;
  	      enum rtx_code cmp_code;
  
  	      if (neg_inc)
  		{
  		  cmp_const = abs_inc - 1;
  		  cmp_code = LE;
  		}
  	      else
  		{
  		  cmp_const = abs_inc * (unroll_number - 1) + 1;
  		  cmp_code = GE;
  		}
  
  	      simplify_cmp_and_jump_insns (cmp_code, mode, diff,
  					   GEN_INT (cmp_const), labels[0]);
  	    }
  
  	  sequence = get_insns ();
  	  end_sequence ();
  	  loop_insn_hoist (loop, sequence);
  
  	  /* Only the last copy of the loop body here needs the exit
  	     test, so set copy_end to exclude the compare/branch here,
  	     and then reset it inside the loop when get to the last
  	     copy.  */
  
  	  if (GET_CODE (last_loop_insn) == BARRIER)
  	    copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
  	  else if (GET_CODE (last_loop_insn) == JUMP_INSN)
  	    {
  	      copy_end = PREV_INSN (last_loop_insn);
  #ifdef HAVE_cc0
  	      /* The immediately preceding insn may be a compare which
  		 we do not want to copy.  */
  	      if (sets_cc0_p (PREV_INSN (copy_end)))
  		copy_end = PREV_INSN (copy_end);
  #endif
  	    }
  	  else
  	    abort ();
  
  	  for (i = 1; i < unroll_number; i++)
  	    {
  	      emit_label_after (labels[unroll_number - i],
  				PREV_INSN (loop_start));
  
  	      memset ((char *) map->insn_map, 0, max_insnno * sizeof (rtx));
  	      memset ((char *) &VARRAY_CONST_EQUIV (map->const_equiv_varray, 0),
  		      0, (VARRAY_SIZE (map->const_equiv_varray)
  			  * sizeof (struct const_equiv_data)));
  	      map->const_age = 0;
  
  	      for (j = 0; j < max_labelno; j++)
  		if (local_label[j])
  		  set_label_in_map (map, j, gen_label_rtx ());
  
  	      for (r = FIRST_PSEUDO_REGISTER; r < max_local_regnum; r++)
  		if (local_regno[r])
  		  {
  		    map->reg_map[r]
  		      = gen_reg_rtx (GET_MODE (regno_reg_rtx[r]));
  		    record_base_value (REGNO (map->reg_map[r]),
  				       regno_reg_rtx[r], 0);
  		  }
  	      /* The last copy needs the compare/branch insns at the end,
  		 so reset copy_end here if the loop ends with a conditional
  		 branch.  */
  
  	      if (i == unroll_number - 1)
  		{
  		  if (GET_CODE (last_loop_insn) == BARRIER)
  		    copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
  		  else
  		    copy_end = last_loop_insn;
  		}
  
  	      /* None of the copies are the `last_iteration', so just
  		 pass zero for that parameter.  */
  	      copy_loop_body (loop, copy_start, copy_end, map, exit_label, 0,
  			      unroll_type, start_label, loop_end,
  			      loop_start, copy_end);
  	    }
  	  emit_label_after (labels[0], PREV_INSN (loop_start));
  
  	  if (GET_CODE (last_loop_insn) == BARRIER)
  	    {
  	      insert_before = PREV_INSN (last_loop_insn);
  	      copy_end = PREV_INSN (insert_before);
  	    }
  	  else
  	    {
  	      insert_before = last_loop_insn;
  #ifdef HAVE_cc0
  	      /* The instruction immediately before the JUMP_INSN may
  		 be a compare instruction which we do not want to copy
  		 or delete.  */
  	      if (sets_cc0_p (PREV_INSN (insert_before)))
  		insert_before = PREV_INSN (insert_before);
  #endif
  	      copy_end = PREV_INSN (insert_before);
  	    }
  
  	  /* Set unroll type to MODULO now.  */
  	  unroll_type = UNROLL_MODULO;
  	  loop_preconditioned = 1;
  
  	  /* Clean up.  */
  	  free (labels);
  	}
      }
  
    /* If reach here, and the loop type is UNROLL_NAIVE, then don't unroll
       the loop unless all loops are being unrolled.  */
    if (unroll_type == UNROLL_NAIVE && ! flag_unroll_all_loops)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Unrolling failure: Naive unrolling not being done.\n");
        goto egress;
      }
  
    /* At this point, we are guaranteed to unroll the loop.  */
  
    /* Keep track of the unroll factor for the loop.  */
    loop_info->unroll_number = unroll_number;
  
    /* And whether the loop has been preconditioned.  */
    loop_info->preconditioned = loop_preconditioned;
  
    /* Remember whether it was preconditioned for the second loop pass.  */
    NOTE_PRECONDITIONED (loop->end) = loop_preconditioned;
  
    /* For each biv and giv, determine whether it can be safely split into
       a different variable for each unrolled copy of the loop body.
       We precalculate and save this info here, since computing it is
       expensive.
  
       Do this before deleting any instructions from the loop, so that
       back_branch_in_range_p will work correctly.  */
  
    if (splitting_not_safe)
      temp = 0;
    else
      temp = find_splittable_regs (loop, unroll_type, unroll_number);
  
    /* find_splittable_regs may have created some new registers, so must
       reallocate the reg_map with the new larger size, and must realloc
       the constant maps also.  */
  
    maxregnum = max_reg_num ();
    map->reg_map = (rtx *) xmalloc (maxregnum * sizeof (rtx));
  
    init_reg_map (map, maxregnum);
  
    if (map->const_equiv_varray == 0)
      VARRAY_CONST_EQUIV_INIT (map->const_equiv_varray,
  			     maxregnum + temp * unroll_number * 2,
  			     "unroll_loop");
    global_const_equiv_varray = map->const_equiv_varray;
  
    /* Search the list of bivs and givs to find ones which need to be remapped
       when split, and set their reg_map entry appropriately.  */
  
    for (bl = ivs->list; bl; bl = bl->next)
      {
        if (REGNO (bl->biv->src_reg) != bl->regno)
  	map->reg_map[bl->regno] = bl->biv->src_reg;
  #if 0
        /* Currently, non-reduced/final-value givs are never split.  */
        for (v = bl->giv; v; v = v->next_iv)
  	if (REGNO (v->src_reg) != bl->regno)
  	  map->reg_map[REGNO (v->dest_reg)] = v->src_reg;
  #endif
      }
  
    /* Use our current register alignment and pointer flags.  */
    map->regno_pointer_align = cfun->emit->regno_pointer_align;
    map->x_regno_reg_rtx = cfun->emit->x_regno_reg_rtx;
  
    /* If the loop is being partially unrolled, and the iteration variables
       are being split, and are being renamed for the split, then must fix up
       the compare/jump instruction at the end of the loop to refer to the new
       registers.  This compare isn't copied, so the registers used in it
       will never be replaced if it isn't done here.  */
  
    if (unroll_type == UNROLL_MODULO)
      {
        insn = NEXT_INSN (copy_end);
        if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
  	PATTERN (insn) = remap_split_bivs (loop, PATTERN (insn));
      }
  
    /* For unroll_number times, make a copy of each instruction
       between copy_start and copy_end, and insert these new instructions
       before the end of the loop.  */
  
    for (i = 0; i < unroll_number; i++)
      {
        memset ((char *) map->insn_map, 0, max_insnno * sizeof (rtx));
        memset ((char *) &VARRAY_CONST_EQUIV (map->const_equiv_varray, 0), 0,
  	      VARRAY_SIZE (map->const_equiv_varray) * sizeof (struct const_equiv_data));
        map->const_age = 0;
  
        for (j = 0; j < max_labelno; j++)
  	if (local_label[j])
  	  set_label_in_map (map, j, gen_label_rtx ());
  
        for (r = FIRST_PSEUDO_REGISTER; r < max_local_regnum; r++)
  	if (local_regno[r])
  	  {
  	    map->reg_map[r] = gen_reg_rtx (GET_MODE (regno_reg_rtx[r]));
  	    record_base_value (REGNO (map->reg_map[r]),
  			       regno_reg_rtx[r], 0);
  	  }
  
        /* If loop starts with a branch to the test, then fix it so that
  	 it points to the test of the first unrolled copy of the loop.  */
        if (i == 0 && loop_start != copy_start)
  	{
  	  insn = PREV_INSN (copy_start);
  	  pattern = PATTERN (insn);
  
  	  tem = get_label_from_map (map,
  				    CODE_LABEL_NUMBER
  				    (XEXP (SET_SRC (pattern), 0)));
  	  SET_SRC (pattern) = gen_rtx_LABEL_REF (VOIDmode, tem);
  
  	  /* Set the jump label so that it can be used by later loop unrolling
  	     passes.  */
  	  JUMP_LABEL (insn) = tem;
  	  LABEL_NUSES (tem)++;
  	}
  
        copy_loop_body (loop, copy_start, copy_end, map, exit_label,
  		      i == unroll_number - 1, unroll_type, start_label,
  		      loop_end, insert_before, insert_before);
      }
  
    /* Before deleting any insns, emit a CODE_LABEL immediately after the last
       insn to be deleted.  This prevents any runaway delete_insn call from
       more insns that it should, as it always stops at a CODE_LABEL.  */
  
    /* Delete the compare and branch at the end of the loop if completely
       unrolling the loop.  Deleting the backward branch at the end also
       deletes the code label at the start of the loop.  This is done at
       the very end to avoid problems with back_branch_in_range_p.  */
  
    if (unroll_type == UNROLL_COMPLETELY)
      safety_label = emit_label_after (gen_label_rtx (), last_loop_insn);
    else
      safety_label = emit_label_after (gen_label_rtx (), copy_end);
  
    /* Delete all of the original loop instructions.  Don't delete the
       LOOP_BEG note, or the first code label in the loop.  */
  
    insn = NEXT_INSN (copy_start);
    while (insn != safety_label)
      {
        /* ??? Don't delete named code labels.  They will be deleted when the
  	 jump that references them is deleted.  Otherwise, we end up deleting
  	 them twice, which causes them to completely disappear instead of turn
  	 into NOTE_INSN_DELETED_LABEL notes.  This in turn causes aborts in
  	 dwarfout.c/dwarf2out.c.  We could perhaps fix the dwarf*out.c files
  	 to handle deleted labels instead.  Or perhaps fix DECL_RTL of the
  	 associated LABEL_DECL to point to one of the new label instances.  */
        /* ??? Likewise, we can't delete a NOTE_INSN_DELETED_LABEL note.  */
        if (insn != start_label
  	  && ! (GET_CODE (insn) == CODE_LABEL && LABEL_NAME (insn))
  	  && ! (GET_CODE (insn) == NOTE
  		&& NOTE_LINE_NUMBER (insn) == NOTE_INSN_DELETED_LABEL))
  	insn = delete_related_insns (insn);
        else
  	insn = NEXT_INSN (insn);
      }
  
    /* Can now delete the 'safety' label emitted to protect us from runaway
       delete_related_insns calls.  */
    if (INSN_DELETED_P (safety_label))
      abort ();
    delete_related_insns (safety_label);
  
    /* If exit_label exists, emit it after the loop.  Doing the emit here
       forces it to have a higher INSN_UID than any insn in the unrolled loop.
       This is needed so that mostly_true_jump in reorg.c will treat jumps
       to this loop end label correctly, i.e. predict that they are usually
       not taken.  */
    if (exit_label)
      emit_label_after (exit_label, loop_end);
  
   egress:
    if (unroll_type == UNROLL_COMPLETELY)
      {
        /* Remove the loop notes since this is no longer a loop.  */
        if (loop->vtop)
  	delete_related_insns (loop->vtop);
        if (loop->cont)
  	delete_related_insns (loop->cont);
        if (loop_start)
  	delete_related_insns (loop_start);
        if (loop_end)
  	delete_related_insns (loop_end);
      }
  
    if (map->const_equiv_varray)
      VARRAY_FREE (map->const_equiv_varray);
    if (map->label_map)
      {
        free (map->label_map);
        free (local_label);
      }
    free (map->insn_map);
    free (splittable_regs);
    free (splittable_regs_updates);
    free (addr_combined_regs);
    free (local_regno);
    if (map->reg_map)
      free (map->reg_map);
    free (map);
  }
  
  /* A helper function for unroll_loop.  Emit a compare and branch to 
     satisfy (CMP OP1 OP2), but pass this through the simplifier first.
     If the branch turned out to be conditional, return it, otherwise
     return NULL.  */
  
  static rtx
  simplify_cmp_and_jump_insns (code, mode, op0, op1, label)
       enum rtx_code code;
       enum machine_mode mode;
       rtx op0, op1, label;
  {
    rtx t, insn;
  
    t = simplify_relational_operation (code, mode, op0, op1);
    if (!t)
      {
        enum rtx_code scode = signed_condition (code);
        emit_cmp_and_jump_insns (op0, op1, scode, NULL_RTX, mode,
  			       code != scode, label);
        insn = get_last_insn ();
  
        JUMP_LABEL (insn) = label;
        LABEL_NUSES (label) += 1;
  
        return insn;
      }
    else if (t == const_true_rtx)
      {
        insn = emit_jump_insn (gen_jump (label));
        emit_barrier ();
        JUMP_LABEL (insn) = label;
        LABEL_NUSES (label) += 1;
      }
  
    return NULL_RTX;
  }
  
  /* Return true if the loop can be safely, and profitably, preconditioned
     so that the unrolled copies of the loop body don't need exit tests.
  
     This only works if final_value, initial_value and increment can be
     determined, and if increment is a constant power of 2.
     If increment is not a power of 2, then the preconditioning modulo
     operation would require a real modulo instead of a boolean AND, and this
     is not considered `profitable'.  */
  
  /* ??? If the loop is known to be executed very many times, or the machine
     has a very cheap divide instruction, then preconditioning is a win even
     when the increment is not a power of 2.  Use RTX_COST to compute
     whether divide is cheap.
     ??? A divide by constant doesn't actually need a divide, look at
     expand_divmod.  The reduced cost of this optimized modulo is not
     reflected in RTX_COST.  */
  
  int
  precondition_loop_p (loop, initial_value, final_value, increment, mode)
       const struct loop *loop;
       rtx *initial_value, *final_value, *increment;
       enum machine_mode *mode;
  {
    rtx loop_start = loop->start;
    struct loop_info *loop_info = LOOP_INFO (loop);
  
    if (loop_info->n_iterations > 0)
      {
        if (INTVAL (loop_info->increment) > 0)
  	{
  	  *initial_value = const0_rtx;
  	  *increment = const1_rtx;
  	  *final_value = GEN_INT (loop_info->n_iterations);
  	}
        else
  	{
  	  *initial_value = GEN_INT (loop_info->n_iterations);
  	  *increment = constm1_rtx;
  	  *final_value = const0_rtx;
  	}
        *mode = word_mode;
  
        if (loop_dump_stream)
  	{
  	  fputs ("Preconditioning: Success, number of iterations known, ",
  		 loop_dump_stream);
  	  fprintf (loop_dump_stream, HOST_WIDE_INT_PRINT_DEC,
  		   loop_info->n_iterations);
  	  fputs (".\n", loop_dump_stream);
  	}
        return 1;
      }
  
    if (loop_info->iteration_var == 0)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Preconditioning: Could not find iteration variable.\n");
        return 0;
      }
    else if (loop_info->initial_value == 0)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Preconditioning: Could not find initial value.\n");
        return 0;
      }
    else if (loop_info->increment == 0)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Preconditioning: Could not find increment value.\n");
        return 0;
      }
    else if (GET_CODE (loop_info->increment) != CONST_INT)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Preconditioning: Increment not a constant.\n");
        return 0;
      }
    else if ((exact_log2 (INTVAL (loop_info->increment)) < 0)
  	   && (exact_log2 (-INTVAL (loop_info->increment)) < 0))
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Preconditioning: Increment not a constant power of 2.\n");
        return 0;
      }
  
    /* Unsigned_compare and compare_dir can be ignored here, since they do
       not matter for preconditioning.  */
  
    if (loop_info->final_value == 0)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Preconditioning: EQ comparison loop.\n");
        return 0;
      }
  
    /* Must ensure that final_value is invariant, so call
       loop_invariant_p to check.  Before doing so, must check regno
       against max_reg_before_loop to make sure that the register is in
       the range covered by loop_invariant_p.  If it isn't, then it is
       most likely a biv/giv which by definition are not invariant.  */
    if ((GET_CODE (loop_info->final_value) == REG
         && REGNO (loop_info->final_value) >= max_reg_before_loop)
        || (GET_CODE (loop_info->final_value) == PLUS
  	  && REGNO (XEXP (loop_info->final_value, 0)) >= max_reg_before_loop)
        || ! loop_invariant_p (loop, loop_info->final_value))
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Preconditioning: Final value not invariant.\n");
        return 0;
      }
  
    /* Fail for floating point values, since the caller of this function
       does not have code to deal with them.  */
    if (GET_MODE_CLASS (GET_MODE (loop_info->final_value)) == MODE_FLOAT
        || GET_MODE_CLASS (GET_MODE (loop_info->initial_value)) == MODE_FLOAT)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Preconditioning: Floating point final or initial value.\n");
        return 0;
      }
  
    /* Fail if loop_info->iteration_var is not live before loop_start,
       since we need to test its value in the preconditioning code.  */
  
    if (REGNO_FIRST_LUID (REGNO (loop_info->iteration_var))
        > INSN_LUID (loop_start))
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Preconditioning: Iteration var not live before loop start.\n");
        return 0;
      }
  
    /* Note that loop_iterations biases the initial value for GIV iterators
       such as "while (i-- > 0)" so that we can calculate the number of
       iterations just like for BIV iterators.
  
       Also note that the absolute values of initial_value and
       final_value are unimportant as only their difference is used for
       calculating the number of loop iterations.  */
    *initial_value = loop_info->initial_value;
    *increment = loop_info->increment;
    *final_value = loop_info->final_value;
  
    /* Decide what mode to do these calculations in.  Choose the larger
       of final_value's mode and initial_value's mode, or a full-word if
       both are constants.  */
    *mode = GET_MODE (*final_value);
    if (*mode == VOIDmode)
      {
        *mode = GET_MODE (*initial_value);
        if (*mode == VOIDmode)
  	*mode = word_mode;
      }
    else if (*mode != GET_MODE (*initial_value)
  	   && (GET_MODE_SIZE (*mode)
  	       < GET_MODE_SIZE (GET_MODE (*initial_value))))
      *mode = GET_MODE (*initial_value);
  
    /* Success!  */
    if (loop_dump_stream)
      fprintf (loop_dump_stream, "Preconditioning: Successful.\n");
    return 1;
  }
  
  /* All pseudo-registers must be mapped to themselves.  Two hard registers
     must be mapped, VIRTUAL_STACK_VARS_REGNUM and VIRTUAL_INCOMING_ARGS_
     REGNUM, to avoid function-inlining specific conversions of these
     registers.  All other hard regs can not be mapped because they may be
     used with different
     modes.  */
  
  static void
  init_reg_map (map, maxregnum)
       struct inline_remap *map;
       int maxregnum;
  {
    int i;
  
    for (i = maxregnum - 1; i > LAST_VIRTUAL_REGISTER; i--)
      map->reg_map[i] = regno_reg_rtx[i];
    /* Just clear the rest of the entries.  */
    for (i = LAST_VIRTUAL_REGISTER; i >= 0; i--)
      map->reg_map[i] = 0;
  
    map->reg_map[VIRTUAL_STACK_VARS_REGNUM]
      = regno_reg_rtx[VIRTUAL_STACK_VARS_REGNUM];
    map->reg_map[VIRTUAL_INCOMING_ARGS_REGNUM]
      = regno_reg_rtx[VIRTUAL_INCOMING_ARGS_REGNUM];
  }
  
  /* Strength-reduction will often emit code for optimized biv/givs which
     calculates their value in a temporary register, and then copies the result
     to the iv.  This procedure reconstructs the pattern computing the iv;
     verifying that all operands are of the proper form.
  
     PATTERN must be the result of single_set.
     The return value is the amount that the giv is incremented by.  */
  
  static rtx
  calculate_giv_inc (pattern, src_insn, regno)
       rtx pattern, src_insn;
       unsigned int regno;
  {
    rtx increment;
    rtx increment_total = 0;
    int tries = 0;
  
   retry:
    /* Verify that we have an increment insn here.  First check for a plus
       as the set source.  */
    if (GET_CODE (SET_SRC (pattern)) != PLUS)
      {
        /* SR sometimes computes the new giv value in a temp, then copies it
  	 to the new_reg.  */
        src_insn = PREV_INSN (src_insn);
        pattern = single_set (src_insn);
        if (GET_CODE (SET_SRC (pattern)) != PLUS)
  	abort ();
  
        /* The last insn emitted is not needed, so delete it to avoid confusing
  	 the second cse pass.  This insn sets the giv unnecessarily.  */
        delete_related_insns (get_last_insn ());
      }
  
    /* Verify that we have a constant as the second operand of the plus.  */
    increment = XEXP (SET_SRC (pattern), 1);
    if (GET_CODE (increment) != CONST_INT)
      {
        /* SR sometimes puts the constant in a register, especially if it is
  	 too big to be an add immed operand.  */
        increment = find_last_value (increment, &src_insn, NULL_RTX, 0);
  
        /* SR may have used LO_SUM to compute the constant if it is too large
  	 for a load immed operand.  In this case, the constant is in operand
  	 one of the LO_SUM rtx.  */
        if (GET_CODE (increment) == LO_SUM)
  	increment = XEXP (increment, 1);
  
        /* Some ports store large constants in memory and add a REG_EQUAL
  	 note to the store insn.  */
        else if (GET_CODE (increment) == MEM)
  	{
  	  rtx note = find_reg_note (src_insn, REG_EQUAL, 0);
  	  if (note)
  	    increment = XEXP (note, 0);
  	}
  
        else if (GET_CODE (increment) == IOR
  	       || GET_CODE (increment) == PLUS
  	       || GET_CODE (increment) == ASHIFT
  	       || GET_CODE (increment) == LSHIFTRT)
  	{
  	  /* The rs6000 port loads some constants with IOR.
  	     The alpha port loads some constants with ASHIFT and PLUS.
  	     The sparc64 port loads some constants with LSHIFTRT.  */
  	  rtx second_part = XEXP (increment, 1);
  	  enum rtx_code code = GET_CODE (increment);
  
  	  increment = find_last_value (XEXP (increment, 0),
  				       &src_insn, NULL_RTX, 0);
  	  /* Don't need the last insn anymore.  */
  	  delete_related_insns (get_last_insn ());
  
  	  if (GET_CODE (second_part) != CONST_INT
  	      || GET_CODE (increment) != CONST_INT)
  	    abort ();
  
  	  if (code == IOR)
  	    increment = GEN_INT (INTVAL (increment) | INTVAL (second_part));
  	  else if (code == PLUS)
  	    increment = GEN_INT (INTVAL (increment) + INTVAL (second_part));
  	  else if (code == ASHIFT)
  	    increment = GEN_INT (INTVAL (increment) << INTVAL (second_part));
  	  else
  	    increment = GEN_INT ((unsigned HOST_WIDE_INT) INTVAL (increment) >> INTVAL (second_part));
  	}
  
        if (GET_CODE (increment) != CONST_INT)
  	abort ();
  
        /* The insn loading the constant into a register is no longer needed,
  	 so delete it.  */
        delete_related_insns (get_last_insn ());
      }
  
    if (increment_total)
      increment_total = GEN_INT (INTVAL (increment_total) + INTVAL (increment));
    else
      increment_total = increment;
  
    /* Check that the source register is the same as the register we expected
       to see as the source.  If not, something is seriously wrong.  */
    if (GET_CODE (XEXP (SET_SRC (pattern), 0)) != REG
        || REGNO (XEXP (SET_SRC (pattern), 0)) != regno)
      {
        /* Some machines (e.g. the romp), may emit two add instructions for
  	 certain constants, so lets try looking for another add immediately
  	 before this one if we have only seen one add insn so far.  */
  
        if (tries == 0)
  	{
  	  tries++;
  
  	  src_insn = PREV_INSN (src_insn);
  	  pattern = single_set (src_insn);
  
  	  delete_related_insns (get_last_insn ());
  
  	  goto retry;
  	}
  
        abort ();
      }
  
    return increment_total;
  }
  
  /* Copy REG_NOTES, except for insn references, because not all insn_map
     entries are valid yet.  We do need to copy registers now though, because
     the reg_map entries can change during copying.  */
  
  static rtx
  initial_reg_note_copy (notes, map)
       rtx notes;
       struct inline_remap *map;
  {
    rtx copy;
  
    if (notes == 0)
      return 0;
  
    copy = rtx_alloc (GET_CODE (notes));
    PUT_REG_NOTE_KIND (copy, REG_NOTE_KIND (notes));
  
    if (GET_CODE (notes) == EXPR_LIST)
      XEXP (copy, 0) = copy_rtx_and_substitute (XEXP (notes, 0), map, 0);
    else if (GET_CODE (notes) == INSN_LIST)
      /* Don't substitute for these yet.  */
      XEXP (copy, 0) = copy_rtx (XEXP (notes, 0));
    else
      abort ();
  
    XEXP (copy, 1) = initial_reg_note_copy (XEXP (notes, 1), map);
  
    return copy;
  }
  
  /* Fixup insn references in copied REG_NOTES.  */
  
  static void
  final_reg_note_copy (notesp, map)
       rtx *notesp;
       struct inline_remap *map;
  {
    while (*notesp)
      {
        rtx note = *notesp;
  
        if (GET_CODE (note) == INSN_LIST)
  	{
  	  /* Sometimes, we have a REG_WAS_0 note that points to a
  	     deleted instruction.  In that case, we can just delete the
  	     note.  */
  	  if (REG_NOTE_KIND (note) == REG_WAS_0)
  	    {
  	      *notesp = XEXP (note, 1);
  	      continue;
  	    }
  	  else
  	    {
  	      rtx insn = map->insn_map[INSN_UID (XEXP (note, 0))];
  
  	      /* If we failed to remap the note, something is awry.
  		 Allow REG_LABEL as it may reference label outside
  		 the unrolled loop.  */
  	      if (!insn)
  		{
  		  if (REG_NOTE_KIND (note) != REG_LABEL)
  		    abort ();
  		}
  	      else
  	        XEXP (note, 0) = insn;
  	    }
  	}
  
        notesp = &XEXP (note, 1);
      }
  }
  
  /* Copy each instruction in the loop, substituting from map as appropriate.
     This is very similar to a loop in expand_inline_function.  */
  
  static void
  copy_loop_body (loop, copy_start, copy_end, map, exit_label, last_iteration,
  		unroll_type, start_label, loop_end, insert_before,
  		copy_notes_from)
       struct loop *loop;
       rtx copy_start, copy_end;
       struct inline_remap *map;
       rtx exit_label;
       int last_iteration;
       enum unroll_types unroll_type;
       rtx start_label, loop_end, insert_before, copy_notes_from;
  {
    struct loop_ivs *ivs = LOOP_IVS (loop);
    rtx insn, pattern;
    rtx set, tem, copy = NULL_RTX;
    int dest_reg_was_split, i;
  #ifdef HAVE_cc0
    rtx cc0_insn = 0;
  #endif
    rtx final_label = 0;
    rtx giv_inc, giv_dest_reg, giv_src_reg;
  
    /* If this isn't the last iteration, then map any references to the
       start_label to final_label.  Final label will then be emitted immediately
       after the end of this loop body if it was ever used.
  
       If this is the last iteration, then map references to the start_label
       to itself.  */
    if (! last_iteration)
      {
        final_label = gen_label_rtx ();
        set_label_in_map (map, CODE_LABEL_NUMBER (start_label), final_label);
      }
    else
      set_label_in_map (map, CODE_LABEL_NUMBER (start_label), start_label);
  
    start_sequence ();
  
    insn = copy_start;
    do
      {
        insn = NEXT_INSN (insn);
  
        map->orig_asm_operands_vector = 0;
  
        switch (GET_CODE (insn))
  	{
  	case INSN:
  	  pattern = PATTERN (insn);
  	  copy = 0;
  	  giv_inc = 0;
  
  	  /* Check to see if this is a giv that has been combined with
  	     some split address givs.  (Combined in the sense that
  	     `combine_givs' in loop.c has put two givs in the same register.)
  	     In this case, we must search all givs based on the same biv to
  	     find the address givs.  Then split the address givs.
  	     Do this before splitting the giv, since that may map the
  	     SET_DEST to a new register.  */
  
  	  if ((set = single_set (insn))
  	      && GET_CODE (SET_DEST (set)) == REG
  	      && addr_combined_regs[REGNO (SET_DEST (set))])
  	    {
  	      struct iv_class *bl;
  	      struct induction *v, *tv;
  	      unsigned int regno = REGNO (SET_DEST (set));
  
  	      v = addr_combined_regs[REGNO (SET_DEST (set))];
  	      bl = REG_IV_CLASS (ivs, REGNO (v->src_reg));
  
  	      /* Although the giv_inc amount is not needed here, we must call
  		 calculate_giv_inc here since it might try to delete the
  		 last insn emitted.  If we wait until later to call it,
  		 we might accidentally delete insns generated immediately
  		 below by emit_unrolled_add.  */
  
  	      giv_inc = calculate_giv_inc (set, insn, regno);
  
  	      /* Now find all address giv's that were combined with this
  		 giv 'v'.  */
  	      for (tv = bl->giv; tv; tv = tv->next_iv)
  		if (tv->giv_type == DEST_ADDR && tv->same == v)
  		  {
  		    int this_giv_inc;
  
  		    /* If this DEST_ADDR giv was not split, then ignore it.  */
  		    if (*tv->location != tv->dest_reg)
  		      continue;
  
  		    /* Scale this_giv_inc if the multiplicative factors of
  		       the two givs are different.  */
  		    this_giv_inc = INTVAL (giv_inc);
  		    if (tv->mult_val != v->mult_val)
  		      this_giv_inc = (this_giv_inc / INTVAL (v->mult_val)
  				      * INTVAL (tv->mult_val));
  
  		    tv->dest_reg = plus_constant (tv->dest_reg, this_giv_inc);
  		    *tv->location = tv->dest_reg;
  
  		    if (last_iteration && unroll_type != UNROLL_COMPLETELY)
  		      {
  			/* Must emit an insn to increment the split address
  			   giv.  Add in the const_adjust field in case there
  			   was a constant eliminated from the address.  */
  			rtx value, dest_reg;
  
  			/* tv->dest_reg will be either a bare register,
  			   or else a register plus a constant.  */
  			if (GET_CODE (tv->dest_reg) == REG)
  			  dest_reg = tv->dest_reg;
  			else
  			  dest_reg = XEXP (tv->dest_reg, 0);
  
  			/* Check for shared address givs, and avoid
  			   incrementing the shared pseudo reg more than
  			   once.  */
  			if (! tv->same_insn && ! tv->shared)
  			  {
  			    /* tv->dest_reg may actually be a (PLUS (REG)
  			       (CONST)) here, so we must call plus_constant
  			       to add the const_adjust amount before calling
  			       emit_unrolled_add below.  */
  			    value = plus_constant (tv->dest_reg,
  						   tv->const_adjust);
  
  			    if (GET_CODE (value) == PLUS)
  			      {
  				/* The constant could be too large for an add
  				   immediate, so can't directly emit an insn
  				   here.  */
  				emit_unrolled_add (dest_reg, XEXP (value, 0),
  						   XEXP (value, 1));
  			      }
  			  }
  
  			/* Reset the giv to be just the register again, in case
  			   it is used after the set we have just emitted.
  			   We must subtract the const_adjust factor added in
  			   above.  */
  			tv->dest_reg = plus_constant (dest_reg,
  						      -tv->const_adjust);
  			*tv->location = tv->dest_reg;
  		      }
  		  }
  	    }
  
  	  /* If this is a setting of a splittable variable, then determine
  	     how to split the variable, create a new set based on this split,
  	     and set up the reg_map so that later uses of the variable will
  	     use the new split variable.  */
  
  	  dest_reg_was_split = 0;
  
  	  if ((set = single_set (insn))
  	      && GET_CODE (SET_DEST (set)) == REG
  	      && splittable_regs[REGNO (SET_DEST (set))])
  	    {
  	      unsigned int regno = REGNO (SET_DEST (set));
  	      unsigned int src_regno;
  
  	      dest_reg_was_split = 1;
  
  	      giv_dest_reg = SET_DEST (set);
  	      giv_src_reg = giv_dest_reg;
  	      /* Compute the increment value for the giv, if it wasn't
  		 already computed above.  */
  	      if (giv_inc == 0)
  		giv_inc = calculate_giv_inc (set, insn, regno);
  
  	      src_regno = REGNO (giv_src_reg);
  
  	      if (unroll_type == UNROLL_COMPLETELY)
  		{
  		  /* Completely unrolling the loop.  Set the induction
  		     variable to a known constant value.  */
  
  		  /* The value in splittable_regs may be an invariant
  		     value, so we must use plus_constant here.  */
  		  splittable_regs[regno]
  		    = plus_constant (splittable_regs[src_regno],
  				     INTVAL (giv_inc));
  
  		  if (GET_CODE (splittable_regs[regno]) == PLUS)
  		    {
  		      giv_src_reg = XEXP (splittable_regs[regno], 0);
  		      giv_inc = XEXP (splittable_regs[regno], 1);
  		    }
  		  else
  		    {
  		      /* The splittable_regs value must be a REG or a
  			 CONST_INT, so put the entire value in the giv_src_reg
  			 variable.  */
  		      giv_src_reg = splittable_regs[regno];
  		      giv_inc = const0_rtx;
  		    }
  		}
  	      else
  		{
  		  /* Partially unrolling loop.  Create a new pseudo
  		     register for the iteration variable, and set it to
  		     be a constant plus the original register.  Except
  		     on the last iteration, when the result has to
  		     go back into the original iteration var register.  */
  
  		  /* Handle bivs which must be mapped to a new register
  		     when split.  This happens for bivs which need their
  		     final value set before loop entry.  The new register
  		     for the biv was stored in the biv's first struct
  		     induction entry by find_splittable_regs.  */
  
  		  if (regno < ivs->n_regs
  		      && REG_IV_TYPE (ivs, regno) == BASIC_INDUCT)
  		    {
  		      giv_src_reg = REG_IV_CLASS (ivs, regno)->biv->src_reg;
  		      giv_dest_reg = giv_src_reg;
  		    }
  
  #if 0
  		  /* If non-reduced/final-value givs were split, then
  		     this would have to remap those givs also.  See
  		     find_splittable_regs.  */
  #endif
  
  		  splittable_regs[regno]
  		    = simplify_gen_binary (PLUS, GET_MODE (giv_src_reg),
  					   giv_inc,
  					   splittable_regs[src_regno]);
  		  giv_inc = splittable_regs[regno];
  
  		  /* Now split the induction variable by changing the dest
  		     of this insn to a new register, and setting its
  		     reg_map entry to point to this new register.
  
  		     If this is the last iteration, and this is the last insn
  		     that will update the iv, then reuse the original dest,
  		     to ensure that the iv will have the proper value when
  		     the loop exits or repeats.
  
  		     Using splittable_regs_updates here like this is safe,
  		     because it can only be greater than one if all
  		     instructions modifying the iv are always executed in
  		     order.  */
  
  		  if (! last_iteration
  		      || (splittable_regs_updates[regno]-- != 1))
  		    {
  		      tem = gen_reg_rtx (GET_MODE (giv_src_reg));
  		      giv_dest_reg = tem;
  		      map->reg_map[regno] = tem;
  		      record_base_value (REGNO (tem),
  					 giv_inc == const0_rtx
  					 ? giv_src_reg
  					 : gen_rtx_PLUS (GET_MODE (giv_src_reg),
  							 giv_src_reg, giv_inc),
  					 1);
  		    }
  		  else
  		    map->reg_map[regno] = giv_src_reg;
  		}
  
  	      /* The constant being added could be too large for an add
  		 immediate, so can't directly emit an insn here.  */
  	      emit_unrolled_add (giv_dest_reg, giv_src_reg, giv_inc);
  	      copy = get_last_insn ();
  	      pattern = PATTERN (copy);
  	    }
  	  else
  	    {
  	      pattern = copy_rtx_and_substitute (pattern, map, 0);
  	      copy = emit_insn (pattern);
  	    }
  	  REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
  	  INSN_SCOPE (copy) = INSN_SCOPE (insn);
  
  	  /* If there is a REG_EQUAL note present whose value
  	     is not loop invariant, then delete it, since it
  	     may cause problems with later optimization passes.  */
  	  if ((tem = find_reg_note (copy, REG_EQUAL, NULL_RTX))
  	      && !loop_invariant_p (loop, XEXP (tem, 0)))
  	    remove_note (copy, tem);
  
  #ifdef HAVE_cc0
  	  /* If this insn is setting CC0, it may need to look at
  	     the insn that uses CC0 to see what type of insn it is.
  	     In that case, the call to recog via validate_change will
  	     fail.  So don't substitute constants here.  Instead,
  	     do it when we emit the following insn.
  
  	     For example, see the pyr.md file.  That machine has signed and
  	     unsigned compares.  The compare patterns must check the
  	     following branch insn to see which what kind of compare to
  	     emit.
  
  	     If the previous insn set CC0, substitute constants on it as
  	     well.  */
  	  if (sets_cc0_p (PATTERN (copy)) != 0)
  	    cc0_insn = copy;
  	  else
  	    {
  	      if (cc0_insn)
  		try_constants (cc0_insn, map);
  	      cc0_insn = 0;
  	      try_constants (copy, map);
  	    }
  #else
  	  try_constants (copy, map);
  #endif
  
  	  /* Make split induction variable constants `permanent' since we
  	     know there are no backward branches across iteration variable
  	     settings which would invalidate this.  */
  	  if (dest_reg_was_split)
  	    {
  	      int regno = REGNO (SET_DEST (set));
  
  	      if ((size_t) regno < VARRAY_SIZE (map->const_equiv_varray)
  		  && (VARRAY_CONST_EQUIV (map->const_equiv_varray, regno).age
  		      == map->const_age))
  		VARRAY_CONST_EQUIV (map->const_equiv_varray, regno).age = -1;
  	    }
  	  break;
  
  	case JUMP_INSN:
  	  pattern = copy_rtx_and_substitute (PATTERN (insn), map, 0);
  	  copy = emit_jump_insn (pattern);
  	  REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
  	  INSN_SCOPE (copy) = INSN_SCOPE (insn);
  
  	  if (JUMP_LABEL (insn))
  	    {
  	      JUMP_LABEL (copy) = get_label_from_map (map,
  						      CODE_LABEL_NUMBER
  						      (JUMP_LABEL (insn)));
  	      LABEL_NUSES (JUMP_LABEL (copy))++;
  	    }
  	  if (JUMP_LABEL (insn) == start_label && insn == copy_end
  	      && ! last_iteration)
  	    {
  
  	      /* This is a branch to the beginning of the loop; this is the
  		 last insn being copied; and this is not the last iteration.
  		 In this case, we want to change the original fall through
  		 case to be a branch past the end of the loop, and the
  		 original jump label case to fall_through.  */
  
  	      if (!invert_jump (copy, exit_label, 0))
  		{
  		  rtx jmp;
  		  rtx lab = gen_label_rtx ();
  		  /* Can't do it by reversing the jump (probably because we
  		     couldn't reverse the conditions), so emit a new
  		     jump_insn after COPY, and redirect the jump around
  		     that.  */
  		  jmp = emit_jump_insn_after (gen_jump (exit_label), copy);
  		  JUMP_LABEL (jmp) = exit_label;
  		  LABEL_NUSES (exit_label)++;
  		  jmp = emit_barrier_after (jmp);
  		  emit_label_after (lab, jmp);
  		  LABEL_NUSES (lab) = 0;
  		  if (!redirect_jump (copy, lab, 0))
  		    abort ();
  		}
  	    }
  
  #ifdef HAVE_cc0
  	  if (cc0_insn)
  	    try_constants (cc0_insn, map);
  	  cc0_insn = 0;
  #endif
  	  try_constants (copy, map);
  
  	  /* Set the jump label of COPY correctly to avoid problems with
  	     later passes of unroll_loop, if INSN had jump label set.  */
  	  if (JUMP_LABEL (insn))
  	    {
  	      rtx label = 0;
  
  	      /* Can't use the label_map for every insn, since this may be
  		 the backward branch, and hence the label was not mapped.  */
  	      if ((set = single_set (copy)))
  		{
  		  tem = SET_SRC (set);
  		  if (GET_CODE (tem) == LABEL_REF)
  		    label = XEXP (tem, 0);
  		  else if (GET_CODE (tem) == IF_THEN_ELSE)
  		    {
  		      if (XEXP (tem, 1) != pc_rtx)
  			label = XEXP (XEXP (tem, 1), 0);
  		      else
  			label = XEXP (XEXP (tem, 2), 0);
  		    }
  		}
  
  	      if (label && GET_CODE (label) == CODE_LABEL)
  		JUMP_LABEL (copy) = label;
  	      else
  		{
  		  /* An unrecognizable jump insn, probably the entry jump
  		     for a switch statement.  This label must have been mapped,
  		     so just use the label_map to get the new jump label.  */
  		  JUMP_LABEL (copy)
  		    = get_label_from_map (map,
  					  CODE_LABEL_NUMBER (JUMP_LABEL (insn)));
  		}
  
  	      /* If this is a non-local jump, then must increase the label
  		 use count so that the label will not be deleted when the
  		 original jump is deleted.  */
  	      LABEL_NUSES (JUMP_LABEL (copy))++;
  	    }
  	  else if (GET_CODE (PATTERN (copy)) == ADDR_VEC
  		   || GET_CODE (PATTERN (copy)) == ADDR_DIFF_VEC)
  	    {
  	      rtx pat = PATTERN (copy);
  	      int diff_vec_p = GET_CODE (pat) == ADDR_DIFF_VEC;
  	      int len = XVECLEN (pat, diff_vec_p);
  	      int i;
  
  	      for (i = 0; i < len; i++)
  		LABEL_NUSES (XEXP (XVECEXP (pat, diff_vec_p, i), 0))++;
  	    }
  
  	  /* If this used to be a conditional jump insn but whose branch
  	     direction is now known, we must do something special.  */
  	  if (any_condjump_p (insn) && onlyjump_p (insn) && map->last_pc_value)
  	    {
  #ifdef HAVE_cc0
  	      /* If the previous insn set cc0 for us, delete it.  */
  	      if (only_sets_cc0_p (PREV_INSN (copy)))
  		delete_related_insns (PREV_INSN (copy));
  #endif
  
  	      /* If this is now a no-op, delete it.  */
  	      if (map->last_pc_value == pc_rtx)
  		{
  		  delete_insn (copy);
  		  copy = 0;
  		}
  	      else
  		/* Otherwise, this is unconditional jump so we must put a
  		   BARRIER after it.  We could do some dead code elimination
  		   here, but jump.c will do it just as well.  */
  		emit_barrier ();
  	    }
  	  break;
  
  	case CALL_INSN:
  	  pattern = copy_rtx_and_substitute (PATTERN (insn), map, 0);
  	  copy = emit_call_insn (pattern);
  	  REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
  	  INSN_SCOPE (copy) = INSN_SCOPE (insn);
  	  SIBLING_CALL_P (copy) = SIBLING_CALL_P (insn);
  	  CONST_OR_PURE_CALL_P (copy) = CONST_OR_PURE_CALL_P (insn);
  
  	  /* Because the USAGE information potentially contains objects other
  	     than hard registers, we need to copy it.  */
  	  CALL_INSN_FUNCTION_USAGE (copy)
  	    = copy_rtx_and_substitute (CALL_INSN_FUNCTION_USAGE (insn),
  				       map, 0);
  
  #ifdef HAVE_cc0
  	  if (cc0_insn)
  	    try_constants (cc0_insn, map);
  	  cc0_insn = 0;
  #endif
  	  try_constants (copy, map);
  
  	  /* Be lazy and assume CALL_INSNs clobber all hard registers.  */
  	  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
  	    VARRAY_CONST_EQUIV (map->const_equiv_varray, i).rtx = 0;
  	  break;
  
  	case CODE_LABEL:
  	  /* If this is the loop start label, then we don't need to emit a
  	     copy of this label since no one will use it.  */
  
  	  if (insn != start_label)
  	    {
  	      copy = emit_label (get_label_from_map (map,
  						     CODE_LABEL_NUMBER (insn)));
  	      map->const_age++;
  	    }
  	  break;
  
  	case BARRIER:
  	  copy = emit_barrier ();
  	  break;
  
  	case NOTE:
  	  /* VTOP and CONT notes are valid only before the loop exit test.
  	     If placed anywhere else, loop may generate bad code.  */
  	  /* BASIC_BLOCK notes exist to stabilize basic block structures with
  	     the associated rtl.  We do not want to share the structure in
  	     this new block.  */
  
  	  if (NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED
  	      && NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED_LABEL
  	      && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK
  	      && ((NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_VTOP
  		   && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_CONT)
  		  || (last_iteration && unroll_type != UNROLL_COMPLETELY)))
  	    copy = emit_note (NOTE_SOURCE_FILE (insn),
  			      NOTE_LINE_NUMBER (insn));
  	  else
  	    copy = 0;
  	  break;
  
  	default:
  	  abort ();
  	}
  
        map->insn_map[INSN_UID (insn)] = copy;
      }
    while (insn != copy_end);
  
    /* Now finish coping the REG_NOTES.  */
    insn = copy_start;
    do
      {
        insn = NEXT_INSN (insn);
        if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN
  	   || GET_CODE (insn) == CALL_INSN)
  	  && map->insn_map[INSN_UID (insn)])
  	final_reg_note_copy (&REG_NOTES (map->insn_map[INSN_UID (insn)]), map);
      }
    while (insn != copy_end);
  
    /* There may be notes between copy_notes_from and loop_end.  Emit a copy of
       each of these notes here, since there may be some important ones, such as
       NOTE_INSN_BLOCK_END notes, in this group.  We don't do this on the last
       iteration, because the original notes won't be deleted.
  
       We can't use insert_before here, because when from preconditioning,
       insert_before points before the loop.  We can't use copy_end, because
       there may be insns already inserted after it (which we don't want to
       copy) when not from preconditioning code.  */
  
    if (! last_iteration)
      {
        for (insn = copy_notes_from; insn != loop_end; insn = NEXT_INSN (insn))
  	{
  	  /* VTOP notes are valid only before the loop exit test.
  	     If placed anywhere else, loop may generate bad code.
  	     Although COPY_NOTES_FROM will be at most one or two (for cc0)
  	     instructions before the last insn in the loop, COPY_NOTES_FROM
  	     can be a NOTE_INSN_LOOP_CONT note if there is no VTOP note,
  	     as in a do .. while loop.  */
  	  if (GET_CODE (insn) == NOTE
  	      && NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED
  	      && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK
  	      && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_VTOP
  	      && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_CONT)
  	    emit_note (NOTE_SOURCE_FILE (insn), NOTE_LINE_NUMBER (insn));
  	}
      }
  
    if (final_label && LABEL_NUSES (final_label) > 0)
      emit_label (final_label);
  
    tem = get_insns ();
    end_sequence ();
    loop_insn_emit_before (loop, 0, insert_before, tem);
  }
  
  /* Emit an insn, using the expand_binop to ensure that a valid insn is
     emitted.  This will correctly handle the case where the increment value
     won't fit in the immediate field of a PLUS insns.  */
  
  void
  emit_unrolled_add (dest_reg, src_reg, increment)
       rtx dest_reg, src_reg, increment;
  {
    rtx result;
  
    result = expand_simple_binop (GET_MODE (dest_reg), PLUS, src_reg, increment,
  				dest_reg, 0, OPTAB_LIB_WIDEN);
  
    if (dest_reg != result)
      emit_move_insn (dest_reg, result);
  }
  
  /* Searches the insns between INSN and LOOP->END.  Returns 1 if there
     is a backward branch in that range that branches to somewhere between
     LOOP->START and INSN.  Returns 0 otherwise.  */
  
  /* ??? This is quadratic algorithm.  Could be rewritten to be linear.
     In practice, this is not a problem, because this function is seldom called,
     and uses a negligible amount of CPU time on average.  */
  
  int
  back_branch_in_range_p (loop, insn)
       const struct loop *loop;
       rtx insn;
  {
    rtx p, q, target_insn;
    rtx loop_start = loop->start;
    rtx loop_end = loop->end;
    rtx orig_loop_end = loop->end;
  
    /* Stop before we get to the backward branch at the end of the loop.  */
    loop_end = prev_nonnote_insn (loop_end);
    if (GET_CODE (loop_end) == BARRIER)
      loop_end = PREV_INSN (loop_end);
  
    /* Check in case insn has been deleted, search forward for first non
       deleted insn following it.  */
    while (INSN_DELETED_P (insn))
      insn = NEXT_INSN (insn);
  
    /* Check for the case where insn is the last insn in the loop.  Deal
       with the case where INSN was a deleted loop test insn, in which case
       it will now be the NOTE_LOOP_END.  */
    if (insn == loop_end || insn == orig_loop_end)
      return 0;
  
    for (p = NEXT_INSN (insn); p != loop_end; p = NEXT_INSN (p))
      {
        if (GET_CODE (p) == JUMP_INSN)
  	{
  	  target_insn = JUMP_LABEL (p);
  
  	  /* Search from loop_start to insn, to see if one of them is
  	     the target_insn.  We can't use INSN_LUID comparisons here,
  	     since insn may not have an LUID entry.  */
  	  for (q = loop_start; q != insn; q = NEXT_INSN (q))
  	    if (q == target_insn)
  	      return 1;
  	}
      }
  
    return 0;
  }
  
  /* Try to generate the simplest rtx for the expression
     (PLUS (MULT mult1 mult2) add1).  This is used to calculate the initial
     value of giv's.  */
  
  static rtx
  fold_rtx_mult_add (mult1, mult2, add1, mode)
       rtx mult1, mult2, add1;
       enum machine_mode mode;
  {
    rtx temp, mult_res;
    rtx result;
  
    /* The modes must all be the same.  This should always be true.  For now,
       check to make sure.  */
    if ((GET_MODE (mult1) != mode && GET_MODE (mult1) != VOIDmode)
        || (GET_MODE (mult2) != mode && GET_MODE (mult2) != VOIDmode)
        || (GET_MODE (add1) != mode && GET_MODE (add1) != VOIDmode))
      abort ();
  
    /* Ensure that if at least one of mult1/mult2 are constant, then mult2
       will be a constant.  */
    if (GET_CODE (mult1) == CONST_INT)
      {
        temp = mult2;
        mult2 = mult1;
        mult1 = temp;
      }
  
    mult_res = simplify_binary_operation (MULT, mode, mult1, mult2);
    if (! mult_res)
      mult_res = gen_rtx_MULT (mode, mult1, mult2);
  
    /* Again, put the constant second.  */
    if (GET_CODE (add1) == CONST_INT)
      {
        temp = add1;
        add1 = mult_res;
        mult_res = temp;
      }
  
    result = simplify_binary_operation (PLUS, mode, add1, mult_res);
    if (! result)
      result = gen_rtx_PLUS (mode, add1, mult_res);
  
    return result;
  }
  
  /* Searches the list of induction struct's for the biv BL, to try to calculate
     the total increment value for one iteration of the loop as a constant.
  
     Returns the increment value as an rtx, simplified as much as possible,
     if it can be calculated.  Otherwise, returns 0.  */
  
  rtx
  biv_total_increment (bl)
       const struct iv_class *bl;
  {
    struct induction *v;
    rtx result;
  
    /* For increment, must check every instruction that sets it.  Each
       instruction must be executed only once each time through the loop.
       To verify this, we check that the insn is always executed, and that
       there are no backward branches after the insn that branch to before it.
       Also, the insn must have a mult_val of one (to make sure it really is
       an increment).  */
  
    result = const0_rtx;
    for (v = bl->biv; v; v = v->next_iv)
      {
        if (v->always_computable && v->mult_val == const1_rtx
  	  && ! v->maybe_multiple
  	  && SCALAR_INT_MODE_P (v->mode))
  	{
  	  /* If we have already counted it, skip it.  */
  	  if (v->same)
  	    continue;
  
  	  result = fold_rtx_mult_add (result, const1_rtx, v->add_val, v->mode);
  	}
        else
  	return 0;
      }
  
    return result;
  }
  
  /* For each biv and giv, determine whether it can be safely split into
     a different variable for each unrolled copy of the loop body.  If it
     is safe to split, then indicate that by saving some useful info
     in the splittable_regs array.
  
     If the loop is being completely unrolled, then splittable_regs will hold
     the current value of the induction variable while the loop is unrolled.
     It must be set to the initial value of the induction variable here.
     Otherwise, splittable_regs will hold the difference between the current
     value of the induction variable and the value the induction variable had
     at the top of the loop.  It must be set to the value 0 here.
  
     Returns the total number of instructions that set registers that are
     splittable.  */
  
  /* ?? If the loop is only unrolled twice, then most of the restrictions to
     constant values are unnecessary, since we can easily calculate increment
     values in this case even if nothing is constant.  The increment value
     should not involve a multiply however.  */
  
  /* ?? Even if the biv/giv increment values aren't constant, it may still
     be beneficial to split the variable if the loop is only unrolled a few
     times, since multiplies by small integers (1,2,3,4) are very cheap.  */
  
  static int
  find_splittable_regs (loop, unroll_type, unroll_number)
       const struct loop *loop;
       enum unroll_types unroll_type;
       int unroll_number;
  {
    struct loop_ivs *ivs = LOOP_IVS (loop);
    struct iv_class *bl;
    struct induction *v;
    rtx increment, tem;
    rtx biv_final_value;
    int biv_splittable;
    int result = 0;
  
    for (bl = ivs->list; bl; bl = bl->next)
      {
        /* Biv_total_increment must return a constant value,
  	 otherwise we can not calculate the split values.  */
  
        increment = biv_total_increment (bl);
        if (! increment || GET_CODE (increment) != CONST_INT)
  	continue;
  
        /* The loop must be unrolled completely, or else have a known number
  	 of iterations and only one exit, or else the biv must be dead
  	 outside the loop, or else the final value must be known.  Otherwise,
  	 it is unsafe to split the biv since it may not have the proper
  	 value on loop exit.  */
  
        /* loop_number_exit_count is nonzero if the loop has an exit other than
  	 a fall through at the end.  */
  
        biv_splittable = 1;
        biv_final_value = 0;
        if (unroll_type != UNROLL_COMPLETELY
  	  && (loop->exit_count || unroll_type == UNROLL_NAIVE)
  	  && (REGNO_LAST_LUID (bl->regno) >= INSN_LUID (loop->end)
  	      || ! bl->init_insn
  	      || INSN_UID (bl->init_insn) >= max_uid_for_loop
  	      || (REGNO_FIRST_LUID (bl->regno)
  		  < INSN_LUID (bl->init_insn))
  	      || reg_mentioned_p (bl->biv->dest_reg, SET_SRC (bl->init_set)))
  	  && ! (biv_final_value = final_biv_value (loop, bl)))
  	biv_splittable = 0;
  
        /* If any of the insns setting the BIV don't do so with a simple
  	 PLUS, we don't know how to split it.  */
        for (v = bl->biv; biv_splittable && v; v = v->next_iv)
  	if ((tem = single_set (v->insn)) == 0
  	    || GET_CODE (SET_DEST (tem)) != REG
  	    || REGNO (SET_DEST (tem)) != bl->regno
  	    || GET_CODE (SET_SRC (tem)) != PLUS)
  	  biv_splittable = 0;
  
        /* If final value is nonzero, then must emit an instruction which sets
  	 the value of the biv to the proper value.  This is done after
  	 handling all of the givs, since some of them may need to use the
  	 biv's value in their initialization code.  */
  
        /* This biv is splittable.  If completely unrolling the loop, save
  	 the biv's initial value.  Otherwise, save the constant zero.  */
  
        if (biv_splittable == 1)
  	{
  	  if (unroll_type == UNROLL_COMPLETELY)
  	    {
  	      /* If the initial value of the biv is itself (i.e. it is too
  		 complicated for strength_reduce to compute), or is a hard
  		 register, or it isn't invariant, then we must create a new
  		 pseudo reg to hold the initial value of the biv.  */
  
  	      if (GET_CODE (bl->initial_value) == REG
  		  && (REGNO (bl->initial_value) == bl->regno
  		      || REGNO (bl->initial_value) < FIRST_PSEUDO_REGISTER
  		      || ! loop_invariant_p (loop, bl->initial_value)))
  		{
  		  rtx tem = gen_reg_rtx (bl->biv->mode);
  
  		  record_base_value (REGNO (tem), bl->biv->add_val, 0);
  		  loop_insn_hoist (loop,
  				   gen_move_insn (tem, bl->biv->src_reg));
  
  		  if (loop_dump_stream)
  		    fprintf (loop_dump_stream,
  			     "Biv %d initial value remapped to %d.\n",
  			     bl->regno, REGNO (tem));
  
  		  splittable_regs[bl->regno] = tem;
  		}
  	      else
  		splittable_regs[bl->regno] = bl->initial_value;
  	    }
  	  else
  	    splittable_regs[bl->regno] = const0_rtx;
  
  	  /* Save the number of instructions that modify the biv, so that
  	     we can treat the last one specially.  */
  
  	  splittable_regs_updates[bl->regno] = bl->biv_count;
  	  result += bl->biv_count;
  
  	  if (loop_dump_stream)
  	    fprintf (loop_dump_stream,
  		     "Biv %d safe to split.\n", bl->regno);
  	}
  
        /* Check every giv that depends on this biv to see whether it is
  	 splittable also.  Even if the biv isn't splittable, givs which
  	 depend on it may be splittable if the biv is live outside the
  	 loop, and the givs aren't.  */
  
        result += find_splittable_givs (loop, bl, unroll_type, increment,
  				      unroll_number);
  
        /* If final value is nonzero, then must emit an instruction which sets
  	 the value of the biv to the proper value.  This is done after
  	 handling all of the givs, since some of them may need to use the
  	 biv's value in their initialization code.  */
        if (biv_final_value)
  	{
  	  /* If the loop has multiple exits, emit the insns before the
  	     loop to ensure that it will always be executed no matter
  	     how the loop exits.  Otherwise emit the insn after the loop,
  	     since this is slightly more efficient.  */
  	  if (! loop->exit_count)
  	    loop_insn_sink (loop, gen_move_insn (bl->biv->src_reg,
  						 biv_final_value));
  	  else
  	    {
  	      /* Create a new register to hold the value of the biv, and then
  		 set the biv to its final value before the loop start.  The biv
  		 is set to its final value before loop start to ensure that
  		 this insn will always be executed, no matter how the loop
  		 exits.  */
  	      rtx tem = gen_reg_rtx (bl->biv->mode);
  	      record_base_value (REGNO (tem), bl->biv->add_val, 0);
  
  	      loop_insn_hoist (loop, gen_move_insn (tem, bl->biv->src_reg));
  	      loop_insn_hoist (loop, gen_move_insn (bl->biv->src_reg,
  						    biv_final_value));
  
  	      if (loop_dump_stream)
  		fprintf (loop_dump_stream, "Biv %d mapped to %d for split.\n",
  			 REGNO (bl->biv->src_reg), REGNO (tem));
  
  	      /* Set up the mapping from the original biv register to the new
  		 register.  */
  	      bl->biv->src_reg = tem;
  	    }
  	}
      }
    return result;
  }
  
  /* For every giv based on the biv BL, check to determine whether it is
     splittable.  This is a subroutine to find_splittable_regs ().
  
     Return the number of instructions that set splittable registers.  */
  
  static int
  find_splittable_givs (loop, bl, unroll_type, increment, unroll_number)
       const struct loop *loop;
       struct iv_class *bl;
       enum unroll_types unroll_type;
       rtx increment;
       int unroll_number ATTRIBUTE_UNUSED;
  {
    struct loop_ivs *ivs = LOOP_IVS (loop);
    struct induction *v, *v2;
    rtx final_value;
    rtx tem;
    int result = 0;
  
    /* Scan the list of givs, and set the same_insn field when there are
       multiple identical givs in the same insn.  */
    for (v = bl->giv; v; v = v->next_iv)
      for (v2 = v->next_iv; v2; v2 = v2->next_iv)
        if (v->insn == v2->insn && rtx_equal_p (v->new_reg, v2->new_reg)
  	  && ! v2->same_insn)
  	v2->same_insn = v;
  
    for (v = bl->giv; v; v = v->next_iv)
      {
        rtx giv_inc, value;
  
        /* Only split the giv if it has already been reduced, or if the loop is
  	 being completely unrolled.  */
        if (unroll_type != UNROLL_COMPLETELY && v->ignore)
  	continue;
  
        /* The giv can be split if the insn that sets the giv is executed once
  	 and only once on every iteration of the loop.  */
        /* An address giv can always be split.  v->insn is just a use not a set,
  	 and hence it does not matter whether it is always executed.  All that
  	 matters is that all the biv increments are always executed, and we
  	 won't reach here if they aren't.  */
        if (v->giv_type != DEST_ADDR
  	  && (! v->always_computable
  	      || back_branch_in_range_p (loop, v->insn)))
  	continue;
  
        /* The giv increment value must be a constant.  */
        giv_inc = fold_rtx_mult_add (v->mult_val, increment, const0_rtx,
  				   v->mode);
        if (! giv_inc || GET_CODE (giv_inc) != CONST_INT)
  	continue;
  
        /* The loop must be unrolled completely, or else have a known number of
  	 iterations and only one exit, or else the giv must be dead outside
  	 the loop, or else the final value of the giv must be known.
  	 Otherwise, it is not safe to split the giv since it may not have the
  	 proper value on loop exit.  */
  
        /* The used outside loop test will fail for DEST_ADDR givs.  They are
  	 never used outside the loop anyways, so it is always safe to split a
  	 DEST_ADDR giv.  */
  
        final_value = 0;
        if (unroll_type != UNROLL_COMPLETELY
  	  && (loop->exit_count || unroll_type == UNROLL_NAIVE)
  	  && v->giv_type != DEST_ADDR
  	  /* The next part is true if the pseudo is used outside the loop.
  	     We assume that this is true for any pseudo created after loop
  	     starts, because we don't have a reg_n_info entry for them.  */
  	  && (REGNO (v->dest_reg) >= max_reg_before_loop
  	      || (REGNO_FIRST_UID (REGNO (v->dest_reg)) != INSN_UID (v->insn)
  		  /* Check for the case where the pseudo is set by a shift/add
  		     sequence, in which case the first insn setting the pseudo
  		     is the first insn of the shift/add sequence.  */
  		  && (! (tem = find_reg_note (v->insn, REG_RETVAL, NULL_RTX))
  		      || (REGNO_FIRST_UID (REGNO (v->dest_reg))
  			  != INSN_UID (XEXP (tem, 0)))))
  	      /* Line above always fails if INSN was moved by loop opt.  */
  	      || (REGNO_LAST_LUID (REGNO (v->dest_reg))
  		  >= INSN_LUID (loop->end)))
  	  && ! (final_value = v->final_value))
  	continue;
  
  #if 0
        /* Currently, non-reduced/final-value givs are never split.  */
        /* Should emit insns after the loop if possible, as the biv final value
  	 code below does.  */
  
        /* If the final value is nonzero, and the giv has not been reduced,
  	 then must emit an instruction to set the final value.  */
        if (final_value && !v->new_reg)
  	{
  	  /* Create a new register to hold the value of the giv, and then set
  	     the giv to its final value before the loop start.  The giv is set
  	     to its final value before loop start to ensure that this insn
  	     will always be executed, no matter how we exit.  */
  	  tem = gen_reg_rtx (v->mode);
  	  loop_insn_hoist (loop, gen_move_insn (tem, v->dest_reg));
  	  loop_insn_hoist (loop, gen_move_insn (v->dest_reg, final_value));
  
  	  if (loop_dump_stream)
  	    fprintf (loop_dump_stream, "Giv %d mapped to %d for split.\n",
  		     REGNO (v->dest_reg), REGNO (tem));
  
  	  v->src_reg = tem;
  	}
  #endif
  
        /* This giv is splittable.  If completely unrolling the loop, save the
  	 giv's initial value.  Otherwise, save the constant zero for it.  */
  
        if (unroll_type == UNROLL_COMPLETELY)
  	{
  	  /* It is not safe to use bl->initial_value here, because it may not
  	     be invariant.  It is safe to use the initial value stored in
  	     the splittable_regs array if it is set.  In rare cases, it won't
  	     be set, so then we do exactly the same thing as
  	     find_splittable_regs does to get a safe value.  */
  	  rtx biv_initial_value;
  
  	  if (splittable_regs[bl->regno])
  	    biv_initial_value = splittable_regs[bl->regno];
  	  else if (GET_CODE (bl->initial_value) != REG
  		   || (REGNO (bl->initial_value) != bl->regno
  		       && REGNO (bl->initial_value) >= FIRST_PSEUDO_REGISTER))
  	    biv_initial_value = bl->initial_value;
  	  else
  	    {
  	      rtx tem = gen_reg_rtx (bl->biv->mode);
  
  	      record_base_value (REGNO (tem), bl->biv->add_val, 0);
  	      loop_insn_hoist (loop, gen_move_insn (tem, bl->biv->src_reg));
  	      biv_initial_value = tem;
  	    }
  	  biv_initial_value = extend_value_for_giv (v, biv_initial_value);
  	  value = fold_rtx_mult_add (v->mult_val, biv_initial_value,
  				     v->add_val, v->mode);
  	}
        else
  	value = const0_rtx;
  
        if (v->new_reg)
  	{
  	  /* If a giv was combined with another giv, then we can only split
  	     this giv if the giv it was combined with was reduced.  This
  	     is because the value of v->new_reg is meaningless in this
  	     case.  */
  	  if (v->same && ! v->same->new_reg)
  	    {
  	      if (loop_dump_stream)
  		fprintf (loop_dump_stream,
  			 "giv combined with unreduced giv not split.\n");
  	      continue;
  	    }
  	  /* If the giv is an address destination, it could be something other
  	     than a simple register, these have to be treated differently.  */
  	  else if (v->giv_type == DEST_REG)
  	    {
  	      /* If value is not a constant, register, or register plus
  		 constant, then compute its value into a register before
  		 loop start.  This prevents invalid rtx sharing, and should
  		 generate better code.  We can use bl->initial_value here
  		 instead of splittable_regs[bl->regno] because this code
  		 is going before the loop start.  */
  	      if (unroll_type == UNROLL_COMPLETELY
  		  && GET_CODE (value) != CONST_INT
  		  && GET_CODE (value) != REG
  		  && (GET_CODE (value) != PLUS
  		      || GET_CODE (XEXP (value, 0)) != REG
  		      || GET_CODE (XEXP (value, 1)) != CONST_INT))
  		{
  		  rtx tem = gen_reg_rtx (v->mode);
  		  record_base_value (REGNO (tem), v->add_val, 0);
  		  loop_iv_add_mult_hoist (loop, 
  				extend_value_for_giv (v, bl->initial_value), 
  				v->mult_val, v->add_val, tem);
  		  value = tem;
  		}
  
  	      splittable_regs[reg_or_subregno (v->new_reg)] = value;
  	    }
  	  else
  	    continue;
  	}
        else
  	{
  #if 0
  	  /* Currently, unreduced giv's can't be split.  This is not too much
  	     of a problem since unreduced giv's are not live across loop
  	     iterations anyways.  When unrolling a loop completely though,
  	     it makes sense to reduce&split givs when possible, as this will
  	     result in simpler instructions, and will not require that a reg
  	     be live across loop iterations.  */
  
  	  splittable_regs[REGNO (v->dest_reg)] = value;
  	  fprintf (stderr, "Giv %d at insn %d not reduced\n",
  		   REGNO (v->dest_reg), INSN_UID (v->insn));
  #else
  	  continue;
  #endif
  	}
  
        /* Unreduced givs are only updated once by definition.  Reduced givs
  	 are updated as many times as their biv is.  Mark it so if this is
  	 a splittable register.  Don't need to do anything for address givs
  	 where this may not be a register.  */
  
        if (GET_CODE (v->new_reg) == REG)
  	{
  	  int count = 1;
  	  if (! v->ignore)
  	    count = REG_IV_CLASS (ivs, REGNO (v->src_reg))->biv_count;
  
  	  splittable_regs_updates[reg_or_subregno (v->new_reg)] = count;
  	}
  
        result++;
  
        if (loop_dump_stream)
  	{
  	  int regnum;
  
  	  if (GET_CODE (v->dest_reg) == CONST_INT)
  	    regnum = -1;
  	  else if (GET_CODE (v->dest_reg) != REG)
  	    regnum = REGNO (XEXP (v->dest_reg, 0));
  	  else
  	    regnum = REGNO (v->dest_reg);
  	  fprintf (loop_dump_stream, "Giv %d at insn %d safe to split.\n",
  		   regnum, INSN_UID (v->insn));
  	}
      }
  
    return result;
  }
  
  /* Try to prove that the register is dead after the loop exits.  Trace every
     loop exit looking for an insn that will always be executed, which sets
     the register to some value, and appears before the first use of the register
     is found.  If successful, then return 1, otherwise return 0.  */
  
  /* ?? Could be made more intelligent in the handling of jumps, so that
     it can search past if statements and other similar structures.  */
  
  static int
  reg_dead_after_loop (loop, reg)
       const struct loop *loop;
       rtx reg;
  {
    rtx insn, label;
    enum rtx_code code;
    int jump_count = 0;
    int label_count = 0;
  
    /* In addition to checking all exits of this loop, we must also check
       all exits of inner nested loops that would exit this loop.  We don't
       have any way to identify those, so we just give up if there are any
       such inner loop exits.  */
  
    for (label = loop->exit_labels; label; label = LABEL_NEXTREF (label))
      label_count++;
  
    if (label_count != loop->exit_count)
      return 0;
  
    /* HACK: Must also search the loop fall through exit, create a label_ref
       here which points to the loop->end, and append the loop_number_exit_labels
       list to it.  */
    label = gen_rtx_LABEL_REF (VOIDmode, loop->end);
    LABEL_NEXTREF (label) = loop->exit_labels;
  
    for (; label; label = LABEL_NEXTREF (label))
      {
        /* Succeed if find an insn which sets the biv or if reach end of
  	 function.  Fail if find an insn that uses the biv, or if come to
  	 a conditional jump.  */
  
        insn = NEXT_INSN (XEXP (label, 0));
        while (insn)
  	{
  	  code = GET_CODE (insn);
  	  if (GET_RTX_CLASS (code) == 'i')
  	    {
  	      rtx set, note;
  
  	      if (reg_referenced_p (reg, PATTERN (insn)))
  		return 0;
  
  	      note = find_reg_equal_equiv_note (insn);
  	      if (note && reg_overlap_mentioned_p (reg, XEXP (note, 0)))
  		return 0;
  
  	      set = single_set (insn);
  	      if (set && rtx_equal_p (SET_DEST (set), reg))
  		break;
  	    }
  
  	  if (code == JUMP_INSN)
  	    {
  	      if (GET_CODE (PATTERN (insn)) == RETURN)
  		break;
  	      else if (!any_uncondjump_p (insn)
  		       /* Prevent infinite loop following infinite loops.  */
  		       || jump_count++ > 20)
  		return 0;
  	      else
  		insn = JUMP_LABEL (insn);
  	    }
  
  	  insn = NEXT_INSN (insn);
  	}
      }
  
    /* Success, the register is dead on all loop exits.  */
    return 1;
  }
  
  /* Try to calculate the final value of the biv, the value it will have at
     the end of the loop.  If we can do it, return that value.  */
  
  rtx
  final_biv_value (loop, bl)
       const struct loop *loop;
       struct iv_class *bl;
  {
    unsigned HOST_WIDE_INT n_iterations = LOOP_INFO (loop)->n_iterations;
    rtx increment, tem;
  
    /* ??? This only works for MODE_INT biv's.  Reject all others for now.  */
  
    if (GET_MODE_CLASS (bl->biv->mode) != MODE_INT)
      return 0;
  
    /* The final value for reversed bivs must be calculated differently than
       for ordinary bivs.  In this case, there is already an insn after the
       loop which sets this biv's final value (if necessary), and there are
       no other loop exits, so we can return any value.  */
    if (bl->reversed)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Final biv value for %d, reversed biv.\n", bl->regno);
  
        return const0_rtx;
      }
  
    /* Try to calculate the final value as initial value + (number of iterations
       * increment).  For this to work, increment must be invariant, the only
       exit from the loop must be the fall through at the bottom (otherwise
       it may not have its final value when the loop exits), and the initial
       value of the biv must be invariant.  */
  
    if (n_iterations != 0
        && ! loop->exit_count
        && loop_invariant_p (loop, bl->initial_value))
      {
        increment = biv_total_increment (bl);
  
        if (increment && loop_invariant_p (loop, increment))
  	{
  	  /* Can calculate the loop exit value, emit insns after loop
  	     end to calculate this value into a temporary register in
  	     case it is needed later.  */
  
  	  tem = gen_reg_rtx (bl->biv->mode);
  	  record_base_value (REGNO (tem), bl->biv->add_val, 0);
  	  loop_iv_add_mult_sink (loop, increment, GEN_INT (n_iterations),
  				 bl->initial_value, tem);
  
  	  if (loop_dump_stream)
  	    fprintf (loop_dump_stream,
  		     "Final biv value for %d, calculated.\n", bl->regno);
  
  	  return tem;
  	}
      }
  
    /* Check to see if the biv is dead at all loop exits.  */
    if (reg_dead_after_loop (loop, bl->biv->src_reg))
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Final biv value for %d, biv dead after loop exit.\n",
  		 bl->regno);
  
        return const0_rtx;
      }
  
    return 0;
  }
  
  /* Try to calculate the final value of the giv, the value it will have at
     the end of the loop.  If we can do it, return that value.  */
  
  rtx
  final_giv_value (loop, v)
       const struct loop *loop;
       struct induction *v;
  {
    struct loop_ivs *ivs = LOOP_IVS (loop);
    struct iv_class *bl;
    rtx insn;
    rtx increment, tem;
    rtx seq;
    rtx loop_end = loop->end;
    unsigned HOST_WIDE_INT n_iterations = LOOP_INFO (loop)->n_iterations;
  
    bl = REG_IV_CLASS (ivs, REGNO (v->src_reg));
  
    /* The final value for givs which depend on reversed bivs must be calculated
       differently than for ordinary givs.  In this case, there is already an
       insn after the loop which sets this giv's final value (if necessary),
       and there are no other loop exits, so we can return any value.  */
    if (bl->reversed)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Final giv value for %d, depends on reversed biv\n",
  		 REGNO (v->dest_reg));
        return const0_rtx;
      }
  
    /* Try to calculate the final value as a function of the biv it depends
       upon.  The only exit from the loop must be the fall through at the bottom
       and the insn that sets the giv must be executed on every iteration
       (otherwise the giv may not have its final value when the loop exits).  */
  
    /* ??? Can calculate the final giv value by subtracting off the
       extra biv increments times the giv's mult_val.  The loop must have
       only one exit for this to work, but the loop iterations does not need
       to be known.  */
  
    if (n_iterations != 0
        && ! loop->exit_count
        && v->always_executed)
      {
        /* ?? It is tempting to use the biv's value here since these insns will
  	 be put after the loop, and hence the biv will have its final value
  	 then.  However, this fails if the biv is subsequently eliminated.
  	 Perhaps determine whether biv's are eliminable before trying to
  	 determine whether giv's are replaceable so that we can use the
  	 biv value here if it is not eliminable.  */
  
        /* We are emitting code after the end of the loop, so we must make
  	 sure that bl->initial_value is still valid then.  It will still
  	 be valid if it is invariant.  */
  
        increment = biv_total_increment (bl);
  
        if (increment && loop_invariant_p (loop, increment)
  	  && loop_invariant_p (loop, bl->initial_value))
  	{
  	  /* Can calculate the loop exit value of its biv as
  	     (n_iterations * increment) + initial_value */
  
  	  /* The loop exit value of the giv is then
  	     (final_biv_value - extra increments) * mult_val + add_val.
  	     The extra increments are any increments to the biv which
  	     occur in the loop after the giv's value is calculated.
  	     We must search from the insn that sets the giv to the end
  	     of the loop to calculate this value.  */
  
  	  /* Put the final biv value in tem.  */
  	  tem = gen_reg_rtx (v->mode);
  	  record_base_value (REGNO (tem), bl->biv->add_val, 0);
  	  loop_iv_add_mult_sink (loop, extend_value_for_giv (v, increment),
  				 GEN_INT (n_iterations),
  				 extend_value_for_giv (v, bl->initial_value),
  				 tem);
  
  	  /* Subtract off extra increments as we find them.  */
  	  for (insn = NEXT_INSN (v->insn); insn != loop_end;
  	       insn = NEXT_INSN (insn))
  	    {
  	      struct induction *biv;
  
  	      for (biv = bl->biv; biv; biv = biv->next_iv)
  		if (biv->insn == insn)
  		  {
  		    start_sequence ();
  		    tem = expand_simple_binop (GET_MODE (tem), MINUS, tem,
  					       biv->add_val, NULL_RTX, 0,
  					       OPTAB_LIB_WIDEN);
  		    seq = get_insns ();
  		    end_sequence ();
  		    loop_insn_sink (loop, seq);
  		  }
  	    }
  
  	  /* Now calculate the giv's final value.  */
  	  loop_iv_add_mult_sink (loop, tem, v->mult_val, v->add_val, tem);
  
  	  if (loop_dump_stream)
  	    fprintf (loop_dump_stream,
  		     "Final giv value for %d, calc from biv's value.\n",
  		     REGNO (v->dest_reg));
  
  	  return tem;
  	}
      }
  
    /* Replaceable giv's should never reach here.  */
    if (v->replaceable)
      abort ();
  
    /* Check to see if the biv is dead at all loop exits.  */
    if (reg_dead_after_loop (loop, v->dest_reg))
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Final giv value for %d, giv dead after loop exit.\n",
  		 REGNO (v->dest_reg));
  
        return const0_rtx;
      }
  
    return 0;
  }
  
  /* Look back before LOOP->START for the insn that sets REG and return
     the equivalent constant if there is a REG_EQUAL note otherwise just
     the SET_SRC of REG.  */
  
  static rtx
  loop_find_equiv_value (loop, reg)
       const struct loop *loop;
       rtx reg;
  {
    rtx loop_start = loop->start;
    rtx insn, set;
    rtx ret;
  
    ret = reg;
    for (insn = PREV_INSN (loop_start); insn; insn = PREV_INSN (insn))
      {
        if (GET_CODE (insn) == CODE_LABEL)
  	break;
  
        else if (INSN_P (insn) && reg_set_p (reg, insn))
  	{
  	  /* We found the last insn before the loop that sets the register.
  	     If it sets the entire register, and has a REG_EQUAL note,
  	     then use the value of the REG_EQUAL note.  */
  	  if ((set = single_set (insn))
  	      && (SET_DEST (set) == reg))
  	    {
  	      rtx note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
  
  	      /* Only use the REG_EQUAL note if it is a constant.
  		 Other things, divide in particular, will cause
  		 problems later if we use them.  */
  	      if (note && GET_CODE (XEXP (note, 0)) != EXPR_LIST
  		  && CONSTANT_P (XEXP (note, 0)))
  		ret = XEXP (note, 0);
  	      else
  		ret = SET_SRC (set);
  
  	      /* We cannot do this if it changes between the
  		 assignment and loop start though.  */
  	      if (modified_between_p (ret, insn, loop_start))
  		ret = reg;
  	    }
  	  break;
  	}
      }
    return ret;
  }
  
  /* Return a simplified rtx for the expression OP - REG.
  
     REG must appear in OP, and OP must be a register or the sum of a register
     and a second term.
  
     Thus, the return value must be const0_rtx or the second term.
  
     The caller is responsible for verifying that REG appears in OP and OP has
     the proper form.  */
  
  static rtx
  subtract_reg_term (op, reg)
       rtx op, reg;
  {
    if (op == reg)
      return const0_rtx;
    if (GET_CODE (op) == PLUS)
      {
        if (XEXP (op, 0) == reg)
  	return XEXP (op, 1);
        else if (XEXP (op, 1) == reg)
  	return XEXP (op, 0);
      }
    /* OP does not contain REG as a term.  */
    abort ();
  }
  
  /* Find and return register term common to both expressions OP0 and
     OP1 or NULL_RTX if no such term exists.  Each expression must be a
     REG or a PLUS of a REG.  */
  
  static rtx
  find_common_reg_term (op0, op1)
       rtx op0, op1;
  {
    if ((GET_CODE (op0) == REG || GET_CODE (op0) == PLUS)
        && (GET_CODE (op1) == REG || GET_CODE (op1) == PLUS))
      {
        rtx op00;
        rtx op01;
        rtx op10;
        rtx op11;
  
        if (GET_CODE (op0) == PLUS)
  	op01 = XEXP (op0, 1), op00 = XEXP (op0, 0);
        else
  	op01 = const0_rtx, op00 = op0;
  
        if (GET_CODE (op1) == PLUS)
  	op11 = XEXP (op1, 1), op10 = XEXP (op1, 0);
        else
  	op11 = const0_rtx, op10 = op1;
  
        /* Find and return common register term if present.  */
        if (REG_P (op00) && (op00 == op10 || op00 == op11))
  	return op00;
        else if (REG_P (op01) && (op01 == op10 || op01 == op11))
  	return op01;
      }
  
    /* No common register term found.  */
    return NULL_RTX;
  }
  
  /* Determine the loop iterator and calculate the number of loop
     iterations.  Returns the exact number of loop iterations if it can
     be calculated, otherwise returns zero.  */
  
  unsigned HOST_WIDE_INT
  loop_iterations (loop)
       struct loop *loop;
  {
    struct loop_info *loop_info = LOOP_INFO (loop);
    struct loop_ivs *ivs = LOOP_IVS (loop);
    rtx comparison, comparison_value;
    rtx iteration_var, initial_value, increment, final_value;
    enum rtx_code comparison_code;
    HOST_WIDE_INT inc;
    unsigned HOST_WIDE_INT abs_inc;
    unsigned HOST_WIDE_INT abs_diff;
    int off_by_one;
    int increment_dir;
    int unsigned_p, compare_dir, final_larger;
    rtx last_loop_insn;
    rtx reg_term;
    struct iv_class *bl;
  
    loop_info->n_iterations = 0;
    loop_info->initial_value = 0;
    loop_info->initial_equiv_value = 0;
    loop_info->comparison_value = 0;
    loop_info->final_value = 0;
    loop_info->final_equiv_value = 0;
    loop_info->increment = 0;
    loop_info->iteration_var = 0;
    loop_info->unroll_number = 1;
    loop_info->iv = 0;
  
    /* We used to use prev_nonnote_insn here, but that fails because it might
       accidentally get the branch for a contained loop if the branch for this
       loop was deleted.  We can only trust branches immediately before the
       loop_end.  */
    last_loop_insn = PREV_INSN (loop->end);
  
    /* ??? We should probably try harder to find the jump insn
       at the end of the loop.  The following code assumes that
       the last loop insn is a jump to the top of the loop.  */
    if (GET_CODE (last_loop_insn) != JUMP_INSN)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Loop iterations: No final conditional branch found.\n");
        return 0;
      }
  
    /* If there is a more than a single jump to the top of the loop
       we cannot (easily) determine the iteration count.  */
    if (LABEL_NUSES (JUMP_LABEL (last_loop_insn)) > 1)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Loop iterations: Loop has multiple back edges.\n");
        return 0;
      }
  
    /* If there are multiple conditionalized loop exit tests, they may jump
       back to differing CODE_LABELs.  */
    if (loop->top && loop->cont)
      {
        rtx temp = PREV_INSN (last_loop_insn);
  
        do
  	{
  	  if (GET_CODE (temp) == JUMP_INSN)
  	    {
  	      /* There are some kinds of jumps we can't deal with easily.  */
  	      if (JUMP_LABEL (temp) == 0)
  		{
  		  if (loop_dump_stream)
  		    fprintf
  		      (loop_dump_stream,
  		       "Loop iterations: Jump insn has null JUMP_LABEL.\n");
  		  return 0;
  		}
  
  	      if (/* Previous unrolling may have generated new insns not
  		     covered by the uid_luid array.  */
  		  INSN_UID (JUMP_LABEL (temp)) < max_uid_for_loop
  		  /* Check if we jump back into the loop body.  */
  		  && INSN_LUID (JUMP_LABEL (temp)) > INSN_LUID (loop->top)
  		  && INSN_LUID (JUMP_LABEL (temp)) < INSN_LUID (loop->cont))
  		{
  		  if (loop_dump_stream)
  		    fprintf
  		      (loop_dump_stream,
  		       "Loop iterations: Loop has multiple back edges.\n");
  		  return 0;
  		}
  	    }
  	}
        while ((temp = PREV_INSN (temp)) != loop->cont);
      }
  
    /* Find the iteration variable.  If the last insn is a conditional
       branch, and the insn before tests a register value, make that the
       iteration variable.  */
  
    comparison = get_condition_for_loop (loop, last_loop_insn);
    if (comparison == 0)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Loop iterations: No final comparison found.\n");
        return 0;
      }
  
    /* ??? Get_condition may switch position of induction variable and
       invariant register when it canonicalizes the comparison.  */
  
    comparison_code = GET_CODE (comparison);
    iteration_var = XEXP (comparison, 0);
    comparison_value = XEXP (comparison, 1);
  
    if (GET_CODE (iteration_var) != REG)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Loop iterations: Comparison not against register.\n");
        return 0;
      }
  
    /* The only new registers that are created before loop iterations
       are givs made from biv increments or registers created by
       load_mems.  In the latter case, it is possible that try_copy_prop
       will propagate a new pseudo into the old iteration register but
       this will be marked by having the REG_USERVAR_P bit set.  */
  
    if ((unsigned) REGNO (iteration_var) >= ivs->n_regs
        && ! REG_USERVAR_P (iteration_var))
      abort ();
  
    /* Determine the initial value of the iteration variable, and the amount
       that it is incremented each loop.  Use the tables constructed by
       the strength reduction pass to calculate these values.  */
  
    /* Clear the result values, in case no answer can be found.  */
    initial_value = 0;
    increment = 0;
  
    /* The iteration variable can be either a giv or a biv.  Check to see
       which it is, and compute the variable's initial value, and increment
       value if possible.  */
  
    /* If this is a new register, can't handle it since we don't have any
       reg_iv_type entry for it.  */
    if ((unsigned) REGNO (iteration_var) >= ivs->n_regs)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Loop iterations: No reg_iv_type entry for iteration var.\n");
        return 0;
      }
  
    /* Reject iteration variables larger than the host wide int size, since they
       could result in a number of iterations greater than the range of our
       `unsigned HOST_WIDE_INT' variable loop_info->n_iterations.  */
    else if ((GET_MODE_BITSIZE (GET_MODE (iteration_var))
  	    > HOST_BITS_PER_WIDE_INT))
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Loop iterations: Iteration var rejected because mode too large.\n");
        return 0;
      }
    else if (GET_MODE_CLASS (GET_MODE (iteration_var)) != MODE_INT)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Loop iterations: Iteration var not an integer.\n");
        return 0;
      }
    else if (REG_IV_TYPE (ivs, REGNO (iteration_var)) == BASIC_INDUCT)
      {
        if (REGNO (iteration_var) >= ivs->n_regs)
  	abort ();
  
        /* Grab initial value, only useful if it is a constant.  */
        bl = REG_IV_CLASS (ivs, REGNO (iteration_var));
        initial_value = bl->initial_value;
        if (!bl->biv->always_executed || bl->biv->maybe_multiple)
  	{
  	  if (loop_dump_stream)
  	    fprintf (loop_dump_stream,
  		     "Loop iterations: Basic induction var not set once in each iteration.\n");
  	  return 0;
  	}
  
        increment = biv_total_increment (bl);
      }
    else if (REG_IV_TYPE (ivs, REGNO (iteration_var)) == GENERAL_INDUCT)
      {
        HOST_WIDE_INT offset = 0;
        struct induction *v = REG_IV_INFO (ivs, REGNO (iteration_var));
        rtx biv_initial_value;
  
        if (REGNO (v->src_reg) >= ivs->n_regs)
  	abort ();
  
        if (!v->always_executed || v->maybe_multiple)
  	{
  	  if (loop_dump_stream)
  	    fprintf (loop_dump_stream,
  		     "Loop iterations: General induction var not set once in each iteration.\n");
  	  return 0;
  	}
  
        bl = REG_IV_CLASS (ivs, REGNO (v->src_reg));
  
        /* Increment value is mult_val times the increment value of the biv.  */
  
        increment = biv_total_increment (bl);
        if (increment)
  	{
  	  struct induction *biv_inc;
  
  	  increment = fold_rtx_mult_add (v->mult_val,
  					 extend_value_for_giv (v, increment),
  					 const0_rtx, v->mode);
  	  /* The caller assumes that one full increment has occurred at the
  	     first loop test.  But that's not true when the biv is incremented
  	     after the giv is set (which is the usual case), e.g.:
  	     i = 6; do {;} while (i++ < 9) .
  	     Therefore, we bias the initial value by subtracting the amount of
  	     the increment that occurs between the giv set and the giv test.  */
  	  for (biv_inc = bl->biv; biv_inc; biv_inc = biv_inc->next_iv)
  	    {
  	      if (loop_insn_first_p (v->insn, biv_inc->insn))
  		{
  		  if (REG_P (biv_inc->add_val))
  		    {
  		      if (loop_dump_stream)
  			fprintf (loop_dump_stream,
  				 "Loop iterations: Basic induction var add_val is REG %d.\n",
  				 REGNO (biv_inc->add_val));
  			return 0;
  		    }
  
  		  /* If we have already counted it, skip it.  */
  		  if (biv_inc->same)
  		    continue;
  
  		  offset -= INTVAL (biv_inc->add_val);
  		}
  	    }
  	}
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Loop iterations: Giv iterator, initial value bias %ld.\n",
  		 (long) offset);
  
        /* Initial value is mult_val times the biv's initial value plus
  	 add_val.  Only useful if it is a constant.  */
        biv_initial_value = extend_value_for_giv (v, bl->initial_value);
        initial_value
  	= fold_rtx_mult_add (v->mult_val,
  			     plus_constant (biv_initial_value, offset),
  			     v->add_val, v->mode);
      }
    else
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Loop iterations: Not basic or general induction var.\n");
        return 0;
      }
  
    if (initial_value == 0)
      return 0;
  
    unsigned_p = 0;
    off_by_one = 0;
    switch (comparison_code)
      {
      case LEU:
        unsigned_p = 1;
      case LE:
        compare_dir = 1;
        off_by_one = 1;
        break;
      case GEU:
        unsigned_p = 1;
      case GE:
        compare_dir = -1;
        off_by_one = -1;
        break;
      case EQ:
        /* Cannot determine loop iterations with this case.  */
        compare_dir = 0;
        break;
      case LTU:
        unsigned_p = 1;
      case LT:
        compare_dir = 1;
        break;
      case GTU:
        unsigned_p = 1;
      case GT:
        compare_dir = -1;
      case NE:
        compare_dir = 0;
        break;
      default:
        abort ();
      }
  
    /* If the comparison value is an invariant register, then try to find
       its value from the insns before the start of the loop.  */
  
    final_value = comparison_value;
    if (GET_CODE (comparison_value) == REG
        && loop_invariant_p (loop, comparison_value))
      {
        final_value = loop_find_equiv_value (loop, comparison_value);
  
        /* If we don't get an invariant final value, we are better
  	 off with the original register.  */
        if (! loop_invariant_p (loop, final_value))
  	final_value = comparison_value;
      }
  
    /* Calculate the approximate final value of the induction variable
       (on the last successful iteration).  The exact final value
       depends on the branch operator, and increment sign.  It will be
       wrong if the iteration variable is not incremented by one each
       time through the loop and (comparison_value + off_by_one -
       initial_value) % increment != 0.
       ??? Note that the final_value may overflow and thus final_larger
       will be bogus.  A potentially infinite loop will be classified
       as immediate, e.g. for (i = 0x7ffffff0; i <= 0x7fffffff; i++)  */
    if (off_by_one)
      final_value = plus_constant (final_value, off_by_one);
  
    /* Save the calculated values describing this loop's bounds, in case
       precondition_loop_p will need them later.  These values can not be
       recalculated inside precondition_loop_p because strength reduction
       optimizations may obscure the loop's structure.
  
       These values are only required by precondition_loop_p and insert_bct
       whenever the number of iterations cannot be computed at compile time.
       Only the difference between final_value and initial_value is
       important.  Note that final_value is only approximate.  */
    loop_info->initial_value = initial_value;
    loop_info->comparison_value = comparison_value;
    loop_info->final_value = plus_constant (comparison_value, off_by_one);
    loop_info->increment = increment;
    loop_info->iteration_var = iteration_var;
    loop_info->comparison_code = comparison_code;
    loop_info->iv = bl;
  
    /* Try to determine the iteration count for loops such
       as (for i = init; i < init + const; i++).  When running the
       loop optimization twice, the first pass often converts simple
       loops into this form.  */
  
    if (REG_P (initial_value))
      {
        rtx reg1;
        rtx reg2;
        rtx const2;
  
        reg1 = initial_value;
        if (GET_CODE (final_value) == PLUS)
  	reg2 = XEXP (final_value, 0), const2 = XEXP (final_value, 1);
        else
  	reg2 = final_value, const2 = const0_rtx;
  
        /* Check for initial_value = reg1, final_value = reg2 + const2,
  	 where reg1 != reg2.  */
        if (REG_P (reg2) && reg2 != reg1)
  	{
  	  rtx temp;
  
  	  /* Find what reg1 is equivalent to.  Hopefully it will
  	     either be reg2 or reg2 plus a constant.  */
  	  temp = loop_find_equiv_value (loop, reg1);
  
  	  if (find_common_reg_term (temp, reg2))
  	    initial_value = temp;
  	  else if (loop_invariant_p (loop, reg2))
  	    {
  	      /* Find what reg2 is equivalent to.  Hopefully it will
  		 either be reg1 or reg1 plus a constant.  Let's ignore
  		 the latter case for now since it is not so common.  */
  	      temp = loop_find_equiv_value (loop, reg2);
  
  	      if (temp == loop_info->iteration_var)
  		temp = initial_value;
  	      if (temp == reg1)
  		final_value = (const2 == const0_rtx)
  		  ? reg1 : gen_rtx_PLUS (GET_MODE (reg1), reg1, const2);
  	    }
  	}
        else if (loop->vtop && GET_CODE (reg2) == CONST_INT)
  	{
  	  rtx temp;
  
  	  /* When running the loop optimizer twice, check_dbra_loop
  	     further obfuscates reversible loops of the form:
  	     for (i = init; i < init + const; i++).  We often end up with
  	     final_value = 0, initial_value = temp, temp = temp2 - init,
  	     where temp2 = init + const.  If the loop has a vtop we
  	     can replace initial_value with const.  */
  
  	  temp = loop_find_equiv_value (loop, reg1);
  
  	  if (GET_CODE (temp) == MINUS && REG_P (XEXP (temp, 0)))
  	    {
  	      rtx temp2 = loop_find_equiv_value (loop, XEXP (temp, 0));
  
  	      if (GET_CODE (temp2) == PLUS
  		  && XEXP (temp2, 0) == XEXP (temp, 1))
  		initial_value = XEXP (temp2, 1);
  	    }
  	}
      }
  
    /* If have initial_value = reg + const1 and final_value = reg +
       const2, then replace initial_value with const1 and final_value
       with const2.  This should be safe since we are protected by the
       initial comparison before entering the loop if we have a vtop.
       For example, a + b < a + c is not equivalent to b < c for all a
       when using modulo arithmetic.
  
       ??? Without a vtop we could still perform the optimization if we check
       the initial and final values carefully.  */
    if (loop->vtop
        && (reg_term = find_common_reg_term (initial_value, final_value)))
      {
        initial_value = subtract_reg_term (initial_value, reg_term);
        final_value = subtract_reg_term (final_value, reg_term);
      }
  
    loop_info->initial_equiv_value = initial_value;
    loop_info->final_equiv_value = final_value;
  
    /* For EQ comparison loops, we don't have a valid final value.
       Check this now so that we won't leave an invalid value if we
       return early for any other reason.  */
    if (comparison_code == EQ)
      loop_info->final_equiv_value = loop_info->final_value = 0;
  
    if (increment == 0)
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream,
  		 "Loop iterations: Increment value can't be calculated.\n");
        return 0;
      }
  
    if (GET_CODE (increment) != CONST_INT)
      {
        /* If we have a REG, check to see if REG holds a constant value.  */
        /* ??? Other RTL, such as (neg (reg)) is possible here, but it isn't
  	 clear if it is worthwhile to try to handle such RTL.  */
        if (GET_CODE (increment) == REG || GET_CODE (increment) == SUBREG)
  	increment = loop_find_equiv_value (loop, increment);
  
        if (GET_CODE (increment) != CONST_INT)
  	{
  	  if (loop_dump_stream)
  	    {
  	      fprintf (loop_dump_stream,
  		       "Loop iterations: Increment value not constant ");
  	      print_simple_rtl (loop_dump_stream, increment);
  	      fprintf (loop_dump_stream, ".\n");
  	    }
  	  return 0;
  	}
        loop_info->increment = increment;
      }
  
    if (GET_CODE (initial_value) != CONST_INT)
      {
        if (loop_dump_stream)
  	{
  	  fprintf (loop_dump_stream,
  		   "Loop iterations: Initial value not constant ");
  	  print_simple_rtl (loop_dump_stream, initial_value);
  	  fprintf (loop_dump_stream, ".\n");
  	}
        return 0;
      }
    else if (GET_CODE (final_value) != CONST_INT)
      {
        if (loop_dump_stream)
  	{
  	  fprintf (loop_dump_stream,
  		   "Loop iterations: Final value not constant ");
  	  print_simple_rtl (loop_dump_stream, final_value);
  	  fprintf (loop_dump_stream, ".\n");
  	}
        return 0;
      }
    else if (comparison_code == EQ)
      {
        rtx inc_once;
  
        if (loop_dump_stream)
  	fprintf (loop_dump_stream, "Loop iterations: EQ comparison loop.\n");
  
        inc_once = gen_int_mode (INTVAL (initial_value) + INTVAL (increment),
  			       GET_MODE (iteration_var));
  
        if (inc_once == final_value)
  	{
  	  /* The iterator value once through the loop is equal to the
  	     comparision value.  Either we have an infinite loop, or
  	     we'll loop twice.  */
  	  if (increment == const0_rtx)
  	    return 0;
  	  loop_info->n_iterations = 2;
  	}
        else
  	loop_info->n_iterations = 1;
  
        if (GET_CODE (loop_info->initial_value) == CONST_INT)
  	loop_info->final_value
  	  = gen_int_mode ((INTVAL (loop_info->initial_value)
  			   + loop_info->n_iterations * INTVAL (increment)),
  			  GET_MODE (iteration_var));
        else
  	loop_info->final_value
  	  = plus_constant (loop_info->initial_value,
  			   loop_info->n_iterations * INTVAL (increment));
        loop_info->final_equiv_value
  	= gen_int_mode ((INTVAL (initial_value)
  			 + loop_info->n_iterations * INTVAL (increment)),
  			GET_MODE (iteration_var));
        return loop_info->n_iterations;
      }
  
    /* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1.  */
    if (unsigned_p)
      final_larger
        = ((unsigned HOST_WIDE_INT) INTVAL (final_value)
  	 > (unsigned HOST_WIDE_INT) INTVAL (initial_value))
  	- ((unsigned HOST_WIDE_INT) INTVAL (final_value)
  	   < (unsigned HOST_WIDE_INT) INTVAL (initial_value));
    else
      final_larger = (INTVAL (final_value) > INTVAL (initial_value))
        - (INTVAL (final_value) < INTVAL (initial_value));
  
    if (INTVAL (increment) > 0)
      increment_dir = 1;
    else if (INTVAL (increment) == 0)
      increment_dir = 0;
    else
      increment_dir = -1;
  
    /* There are 27 different cases: compare_dir = -1, 0, 1;
       final_larger = -1, 0, 1; increment_dir = -1, 0, 1.
       There are 4 normal cases, 4 reverse cases (where the iteration variable
       will overflow before the loop exits), 4 infinite loop cases, and 15
       immediate exit (0 or 1 iteration depending on loop type) cases.
       Only try to optimize the normal cases.  */
  
    /* (compare_dir/final_larger/increment_dir)
       Normal cases: (0/-1/-1), (0/1/1), (-1/-1/-1), (1/1/1)
       Reverse cases: (0/-1/1), (0/1/-1), (-1/-1/1), (1/1/-1)
       Infinite loops: (0/-1/0), (0/1/0), (-1/-1/0), (1/1/0)
       Immediate exit: (0/0/X), (-1/0/X), (-1/1/X), (1/0/X), (1/-1/X) */
  
    /* ?? If the meaning of reverse loops (where the iteration variable
       will overflow before the loop exits) is undefined, then could
       eliminate all of these special checks, and just always assume
       the loops are normal/immediate/infinite.  Note that this means
       the sign of increment_dir does not have to be known.  Also,
       since it does not really hurt if immediate exit loops or infinite loops
       are optimized, then that case could be ignored also, and hence all
       loops can be optimized.
  
       According to ANSI Spec, the reverse loop case result is undefined,
       because the action on overflow is undefined.
  
       See also the special test for NE loops below.  */
  
    if (final_larger == increment_dir && final_larger != 0
        && (final_larger == compare_dir || compare_dir == 0))
      /* Normal case.  */
      ;
    else
      {
        if (loop_dump_stream)
  	fprintf (loop_dump_stream, "Loop iterations: Not normal loop.\n");
        return 0;
      }
  
    /* Calculate the number of iterations, final_value is only an approximation,
       so correct for that.  Note that abs_diff and n_iterations are
       unsigned, because they can be as large as 2^n - 1.  */
  
    inc = INTVAL (increment);
    if (inc > 0)
      {
        abs_diff = INTVAL (final_value) - INTVAL (initial_value);
        abs_inc = inc;
      }
    else if (inc < 0)
      {
        abs_diff = INTVAL (initial_value) - INTVAL (final_value);
        abs_inc = -inc;
      }
    else
      abort ();
  
    /* Given that iteration_var is going to iterate over its own mode,
       not HOST_WIDE_INT, disregard higher bits that might have come
       into the picture due to sign extension of initial and final
       values.  */
    abs_diff &= ((unsigned HOST_WIDE_INT) 1
  	       << (GET_MODE_BITSIZE (GET_MODE (iteration_var)) - 1)
  	       << 1) - 1;
  
    /* For NE tests, make sure that the iteration variable won't miss
       the final value.  If abs_diff mod abs_incr is not zero, then the
       iteration variable will overflow before the loop exits, and we
       can not calculate the number of iterations.  */
    if (compare_dir == 0 && (abs_diff % abs_inc) != 0)
      return 0;
  
    /* Note that the number of iterations could be calculated using
       (abs_diff + abs_inc - 1) / abs_inc, provided care was taken to
       handle potential overflow of the summation.  */
    loop_info->n_iterations = abs_diff / abs_inc + ((abs_diff % abs_inc) != 0);
    return loop_info->n_iterations;
  }
  
  /* Replace uses of split bivs with their split pseudo register.  This is
     for original instructions which remain after loop unrolling without
     copying.  */
  
  static rtx
  remap_split_bivs (loop, x)
       struct loop *loop;
       rtx x;
  {
    struct loop_ivs *ivs = LOOP_IVS (loop);
    enum rtx_code code;
    int i;
    const char *fmt;
  
    if (x == 0)
      return x;
  
    code = GET_CODE (x);
    switch (code)
      {
      case SCRATCH:
      case PC:
      case CC0:
      case CONST_INT:
      case CONST_DOUBLE:
      case CONST:
      case SYMBOL_REF:
      case LABEL_REF:
        return x;
  
      case REG:
  #if 0
        /* If non-reduced/final-value givs were split, then this would also
  	 have to remap those givs also.  */
  #endif
        if (REGNO (x) < ivs->n_regs
  	  && REG_IV_TYPE (ivs, REGNO (x)) == BASIC_INDUCT)
  	return REG_IV_CLASS (ivs, REGNO (x))->biv->src_reg;
        break;
  
      default:
        break;
      }
  
    fmt = GET_RTX_FORMAT (code);
    for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
      {
        if (fmt[i] == 'e')
  	XEXP (x, i) = remap_split_bivs (loop, XEXP (x, i));
        else if (fmt[i] == 'E')
  	{
  	  int j;
  	  for (j = 0; j < XVECLEN (x, i); j++)
  	    XVECEXP (x, i, j) = remap_split_bivs (loop, XVECEXP (x, i, j));
  	}
      }
    return x;
  }
  
  /* If FIRST_UID is a set of REGNO, and FIRST_UID dominates LAST_UID (e.g.
     FIST_UID is always executed if LAST_UID is), then return 1.  Otherwise
     return 0.  COPY_START is where we can start looking for the insns
     FIRST_UID and LAST_UID.  COPY_END is where we stop looking for these
     insns.
  
     If there is no JUMP_INSN between LOOP_START and FIRST_UID, then FIRST_UID
     must dominate LAST_UID.
  
     If there is a CODE_LABEL between FIRST_UID and LAST_UID, then FIRST_UID
     may not dominate LAST_UID.
  
     If there is no CODE_LABEL between FIRST_UID and LAST_UID, then FIRST_UID
     must dominate LAST_UID.  */
  
  int
  set_dominates_use (regno, first_uid, last_uid, copy_start, copy_end)
       int regno;
       int first_uid;
       int last_uid;
       rtx copy_start;
       rtx copy_end;
  {
    int passed_jump = 0;
    rtx p = NEXT_INSN (copy_start);
  
    while (INSN_UID (p) != first_uid)
      {
        if (GET_CODE (p) == JUMP_INSN)
  	passed_jump = 1;
        /* Could not find FIRST_UID.  */
        if (p == copy_end)
  	return 0;
        p = NEXT_INSN (p);
      }
  
    /* Verify that FIRST_UID is an insn that entirely sets REGNO.  */
    if (! INSN_P (p) || ! dead_or_set_regno_p (p, regno))
      return 0;
  
    /* FIRST_UID is always executed.  */
    if (passed_jump == 0)
      return 1;
  
    while (INSN_UID (p) != last_uid)
      {
        /* If we see a CODE_LABEL between FIRST_UID and LAST_UID, then we
  	 can not be sure that FIRST_UID dominates LAST_UID.  */
        if (GET_CODE (p) == CODE_LABEL)
  	return 0;
        /* Could not find LAST_UID, but we reached the end of the loop, so
  	 it must be safe.  */
        else if (p == copy_end)
  	return 1;
        p = NEXT_INSN (p);
      }
  
    /* FIRST_UID is always executed if LAST_UID is executed.  */
    return 1;
  }
  
  /* This routine is called when the number of iterations for the unrolled
     loop is one.   The goal is to identify a loop that begins with an
     unconditional branch to the loop continuation note (or a label just after).
     In this case, the unconditional branch that starts the loop needs to be
     deleted so that we execute the single iteration.  */
  
  static rtx
  ujump_to_loop_cont (loop_start, loop_cont)
       rtx loop_start;
       rtx loop_cont;
  {
    rtx x, label, label_ref;
  
    /* See if loop start, or the next insn is an unconditional jump.  */
    loop_start = next_nonnote_insn (loop_start);
  
    x = pc_set (loop_start);
    if (!x)
      return NULL_RTX;
  
    label_ref = SET_SRC (x);
    if (!label_ref)
      return NULL_RTX;
  
    /* Examine insn after loop continuation note.  Return if not a label.  */
    label = next_nonnote_insn (loop_cont);
    if (label == 0 || GET_CODE (label) != CODE_LABEL)
      return NULL_RTX;
  
    /* Return the loop start if the branch label matches the code label.  */
    if (CODE_LABEL_NUMBER (label) == CODE_LABEL_NUMBER (XEXP (label_ref, 0)))
      return loop_start;
    else
      return NULL_RTX;
  }
  