GCC 4.2.0 release.

1 files changed, 331 insertions, 1218 deletions

diff --git a/contrib/gcc/cfgloopanal.c b/contrib/gcc/cfgloopanal.c
index 6cc8f66..da54583 100644
--- a/contrib/gcc/cfgloopanal.c
+++ b/contrib/gcc/cfgloopanal.c
@@ -1,5 +1,5 @@
 /* Natural loop analysis code for GNU compiler.
-   Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
 
 This file is part of GCC.
 
@@ -15,8 +15,8 @@ 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.  */
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA.  */
 
 #include "config.h"
 #include "system.h"
@@ -24,57 +24,16 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA
 #include "tm.h"
 #include "rtl.h"
 #include "hard-reg-set.h"
+#include "obstack.h"
 #include "basic-block.h"
 #include "cfgloop.h"
 #include "expr.h"
 #include "output.h"
-/* Needed for doloop_condition_get().  */
-#include "loop.h"
-
-struct unmark_altered_insn_data;
-static void unmark_altered (rtx, rtx, regset);
-static void blocks_invariant_registers (basic_block *, int, regset);
-static void unmark_altered_insn (rtx, rtx, struct unmark_altered_insn_data *);
-static void blocks_single_set_registers (basic_block *, int, rtx *);
-static int invariant_rtx_wrto_regs_p_helper (rtx *, regset);
-static bool invariant_rtx_wrto_regs_p (rtx, regset);
-static rtx test_for_iteration (struct loop_desc *desc, unsigned HOST_WIDE_INT);
-static bool constant_iterations (struct loop_desc *, unsigned HOST_WIDE_INT *,
-				 bool *);
-static bool simple_loop_exit_p (struct loop *, edge, regset,
-				rtx *, struct loop_desc *);
-static rtx variable_initial_value (rtx, regset, rtx, rtx *, enum machine_mode);
-static rtx variable_initial_values (edge, rtx, enum machine_mode);
-static bool simple_condition_p (struct loop *, rtx, regset,
-				struct loop_desc *);
-static basic_block simple_increment (struct loop *, rtx *, struct loop_desc *);
-static rtx count_strange_loop_iterations (rtx, rtx, enum rtx_code,
-					  int, rtx, enum machine_mode,
-					  enum machine_mode);
-static unsigned HOST_WIDEST_INT inverse (unsigned HOST_WIDEST_INT, int);
-static bool fits_in_mode_p (enum machine_mode mode, rtx expr);
-
-/* Computes inverse to X modulo (1 << MOD).  */
-static unsigned HOST_WIDEST_INT
-inverse (unsigned HOST_WIDEST_INT x, int mod)
-{
-  unsigned HOST_WIDEST_INT mask =
-	  ((unsigned HOST_WIDEST_INT) 1 << (mod - 1) << 1) - 1;
-  unsigned HOST_WIDEST_INT rslt = 1;
-  int i;
-
-  for (i = 0; i < mod - 1; i++)
-    {
-      rslt = (rslt * x) & mask;
-      x = (x * x) & mask;
-    }
-
-  return rslt;
-}
 
 /* Checks whether BB is executed exactly once in each LOOP iteration.  */
+
 bool
-just_once_each_iteration_p (struct loop *loop, basic_block bb)
+just_once_each_iteration_p (const struct loop *loop, basic_block bb)
 {
   /* It must be executed at least once each iteration.  */
   if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb))
@@ -91,1038 +50,207 @@ just_once_each_iteration_p (struct loop *loop, basic_block bb)
   return true;
 }
 
+/* Structure representing edge of a graph.  */
 
-/* Unmarks modified registers; helper to blocks_invariant_registers.  */
-static void
-unmark_altered (rtx what, rtx by ATTRIBUTE_UNUSED, regset regs)
+struct edge
 {
-  if (GET_CODE (what) == SUBREG)
-    what = SUBREG_REG (what);
-  if (!REG_P (what))
-    return;
-  CLEAR_REGNO_REG_SET (regs, REGNO (what));
-}
+  int src, dest;	/* Source and destination.  */
+  struct edge *pred_next, *succ_next;
+			/* Next edge in predecessor and successor lists.  */
+  void *data;		/* Data attached to the edge.  */
+};
 
-/* Marks registers that are invariant inside blocks BBS.  */
-static void
-blocks_invariant_registers (basic_block *bbs, int nbbs, regset regs)
+/* Structure representing vertex of a graph.  */
+
+struct vertex
 {
-  rtx insn;
-  int i;
+  struct edge *pred, *succ;
+			/* Lists of predecessors and successors.  */
+  int component;	/* Number of dfs restarts before reaching the
+			   vertex.  */
+  int post;		/* Postorder number.  */
+};
 
-  for (i = 0; i < max_reg_num (); i++)
-    SET_REGNO_REG_SET (regs, i);
-  for (i = 0; i < nbbs; i++)
-    for (insn = BB_HEAD (bbs[i]);
-	 insn != NEXT_INSN (BB_END (bbs[i]));
-	 insn = NEXT_INSN (insn))
-      if (INSN_P (insn))
-	note_stores (PATTERN (insn),
-		     (void (*) (rtx, rtx, void *)) unmark_altered,
-		     regs);
-}
+/* Structure representing a graph.  */
 
-/* Unmarks modified registers; helper to blocks_single_set_registers.  */
-struct unmark_altered_insn_data
+struct graph
 {
-  rtx *regs;
-  rtx insn;
+  int n_vertices;	/* Number of vertices.  */
+  struct vertex *vertices;
+			/* The vertices.  */
 };
 
-static void
-unmark_altered_insn (rtx what, rtx by ATTRIBUTE_UNUSED,
-		     struct unmark_altered_insn_data *data)
-{
-  int rn;
+/* Dumps graph G into F.  */
 
-  if (GET_CODE (what) == SUBREG)
-    what = SUBREG_REG (what);
-  if (!REG_P (what))
-    return;
-  rn = REGNO (what);
-  if (data->regs[rn] == data->insn)
-    return;
-  data->regs[rn] = NULL;
-}
+extern void dump_graph (FILE *, struct graph *);
 
-/* Marks registers that have just single simple set in BBS; the relevant
-   insn is returned in REGS.  */
-static void
-blocks_single_set_registers (basic_block *bbs, int nbbs, rtx *regs)
+void
+dump_graph (FILE *f, struct graph *g)
 {
-  rtx insn;
   int i;
-  struct unmark_altered_insn_data data;
+  struct edge *e;
 
-  for (i = 0; i < max_reg_num (); i++)
-    regs[i] = NULL;
-
-  for (i = 0; i < nbbs; i++)
-    for (insn = BB_HEAD (bbs[i]);
-	 insn != NEXT_INSN (BB_END (bbs[i]));
-	 insn = NEXT_INSN (insn))
-      {
-	rtx set = single_set (insn);
-
-	if (!set && is_bct_cond (insn))
-	  set = get_var_set_from_bct(insn);
-
-	if (!set)
-	  continue;
-	if (!REG_P (SET_DEST (set)))
-	  continue;
-	regs[REGNO (SET_DEST (set))] = insn;
-      }
+  for (i = 0; i < g->n_vertices; i++)
+    {
+      if (!g->vertices[i].pred
+	  && !g->vertices[i].succ)
+	continue;
 
-  data.regs = regs;
-  for (i = 0; i < nbbs; i++)
-    for (insn = BB_HEAD (bbs[i]);
-	 insn != NEXT_INSN (BB_END (bbs[i]));
-	 insn = NEXT_INSN (insn))
-      {
-        if (!INSN_P (insn))
-	  continue;
-	data.insn = insn;
-	note_stores (PATTERN (insn),
-	    (void (*) (rtx, rtx, void *)) unmark_altered_insn,
-	    &data);
-      }
-}
+      fprintf (f, "%d (%d)\t<-", i, g->vertices[i].component);
+      for (e = g->vertices[i].pred; e; e = e->pred_next)
+	fprintf (f, " %d", e->src);
+      fprintf (f, "\n");
 
-/* Helper for invariant_rtx_wrto_regs_p.  */
-static int
-invariant_rtx_wrto_regs_p_helper (rtx *expr, regset invariant_regs)
-{
-  switch (GET_CODE (*expr))
-    {
-    case CC0:
-    case PC:
-    case UNSPEC_VOLATILE:
-      return 1;
-
-    case CONST_INT:
-    case CONST_DOUBLE:
-    case CONST:
-    case SYMBOL_REF:
-    case LABEL_REF:
-      return 0;
-
-    case ASM_OPERANDS:
-      return MEM_VOLATILE_P (*expr);
-
-    case MEM:
-      /* If the memory is not constant, assume it is modified.  If it is
-	 constant, we still have to check the address.  */
-      return !RTX_UNCHANGING_P (*expr);
-
-    case REG:
-      return !REGNO_REG_SET_P (invariant_regs, REGNO (*expr));
-
-    default:
-      return 0;
+      fprintf (f, "\t->");
+      for (e = g->vertices[i].succ; e; e = e->succ_next)
+	fprintf (f, " %d", e->dest);
+      fprintf (f, "\n");
     }
 }
 
-/* Checks that EXPR is invariant provided that INVARIANT_REGS are invariant.  */
-static bool
-invariant_rtx_wrto_regs_p (rtx expr, regset invariant_regs)
-{
-  return !for_each_rtx (&expr, (rtx_function) invariant_rtx_wrto_regs_p_helper,
-			invariant_regs);
-}
+/* Creates a new graph with N_VERTICES vertices.  */
 
-/* Checks whether CONDITION is a simple comparison in that one of operands
-   is register and the other one is invariant in the LOOP. Fills var, lim
-   and cond fields in DESC.  */
-static bool
-simple_condition_p (struct loop *loop ATTRIBUTE_UNUSED, rtx condition,
-		    regset invariant_regs, struct loop_desc *desc)
+static struct graph *
+new_graph (int n_vertices)
 {
-  rtx op0, op1;
-
-  /* Check condition.  */
-  switch (GET_CODE (condition))
-    {
-      case EQ:
-      case NE:
-      case LE:
-      case LT:
-      case GE:
-      case GT:
-      case GEU:
-      case GTU:
-      case LEU:
-      case LTU:
-	break;
-      default:
-	return false;
-    }
+  struct graph *g = XNEW (struct graph);
 
-  /* Of integers or pointers.  */
-  if (GET_MODE_CLASS (GET_MODE (XEXP (condition, 0))) != MODE_INT
-      && GET_MODE_CLASS (GET_MODE (XEXP (condition, 0))) != MODE_PARTIAL_INT)
-    return false;
+  g->n_vertices = n_vertices;
+  g->vertices = XCNEWVEC (struct vertex, n_vertices);
 
-  /* One of operands must be a simple register.  */
-  op0 = XEXP (condition, 0);
-  op1 = XEXP (condition, 1);
-
-  /* One of operands must be invariant.  */
-  if (invariant_rtx_wrto_regs_p (op0, invariant_regs))
-    {
-      /* And the other one must be a register.  */
-      if (!REG_P (op1))
-	return false;
-      desc->var = op1;
-      desc->lim = op0;
-
-      desc->cond = swap_condition (GET_CODE (condition));
-      if (desc->cond == UNKNOWN)
-	return false;
-      return true;
-    }
-
-  /* Check the other operand.  */
-  if (!invariant_rtx_wrto_regs_p (op1, invariant_regs))
-    return false;
-  if (!REG_P (op0))
-    return false;
-
-  desc->var = op0;
-  desc->lim = op1;
-
-  desc->cond = GET_CODE (condition);
-
-  return true;
+  return g;
 }
 
-/* Checks whether DESC->var is incremented/decremented exactly once each
-   iteration.  Fills in DESC->stride and returns block in that DESC->var is
-   modified.  */
-static basic_block
-simple_increment (struct loop *loop, rtx *simple_increment_regs,
-		  struct loop_desc *desc)
-{
-  rtx mod_insn, mod_insn1, set, set_src, set_add;
-  basic_block mod_bb, mod_bb1;
-
-  /* Find insn that modifies var.  */
-  mod_insn = simple_increment_regs[REGNO (desc->var)];
-  if (!mod_insn)
-    return NULL;
-  mod_bb = BLOCK_FOR_INSN (mod_insn);
-
-  /* Check that it is executed exactly once each iteration.  */
-  if (!just_once_each_iteration_p (loop, mod_bb))
-    return NULL;
-
-  /* mod_insn must be a simple increment/decrement.  */
-  set = single_set (mod_insn);
-
-  if (!set && is_bct_cond (mod_insn))
-    set = get_var_set_from_bct(mod_insn);
+/* Adds an edge from F to T to graph G, with DATA attached.  */
 
-  if (!set)
-    abort ();
-  if (!rtx_equal_p (SET_DEST (set), desc->var))
-    abort ();
-
-  set_src = find_reg_equal_equiv_note (mod_insn);
-  if (!set_src)
-    set_src = SET_SRC (set);
-
-  /* Check for variables that iterate in narrower mode.  */
-  if (GET_CODE (set_src) == SIGN_EXTEND
-      || GET_CODE (set_src) == ZERO_EXTEND)
-    {
-      /* If we are sign extending variable that is then compared unsigned
-	 or vice versa, there is something weird happening.  */
-      if (desc->cond != EQ
-	  && desc->cond != NE
-	  && ((desc->cond == LEU
-	       || desc->cond == LTU
-	       || desc->cond == GEU
-	       || desc->cond == GTU)
-	      ^ (GET_CODE (set_src) == ZERO_EXTEND)))
-	return NULL;
-
-      if (GET_CODE (XEXP (set_src, 0)) != SUBREG
-	  || SUBREG_BYTE (XEXP (set_src, 0)) != 0
-	  || GET_MODE (SUBREG_REG (XEXP (set_src, 0))) != GET_MODE (desc->var))
-	return NULL;
-
-      desc->inner_mode = GET_MODE (XEXP (set_src, 0));
-      desc->extend = GET_CODE (set_src);
-      set_src = SUBREG_REG (XEXP (set_src, 0));
-
-      if (GET_CODE (set_src) != REG)
-	return NULL;
-
-      /* Find where the reg is set.  */
-      mod_insn1 = simple_increment_regs[REGNO (set_src)];
-      if (!mod_insn1)
-	return NULL;
-
-      mod_bb1 = BLOCK_FOR_INSN (mod_insn1);
-      if (!dominated_by_p (CDI_DOMINATORS, mod_bb, mod_bb1))
-	return NULL;
-      if (mod_bb1 == mod_bb)
-	{
-	  for (;
-	       mod_insn != PREV_INSN (BB_HEAD (mod_bb));
-	       mod_insn = PREV_INSN (mod_insn))
-	    if (mod_insn == mod_insn1)
-	      break;
-
-	  if (mod_insn == PREV_INSN (BB_HEAD (mod_bb)))
-	    return NULL;
-	}
-
-      /* Replace the source with the possible place of increment.  */
-      set = single_set (mod_insn1);
-      if (!set)
-	abort ();
-      if (!rtx_equal_p (SET_DEST (set), set_src))
-	abort ();
-
-      set_src = find_reg_equal_equiv_note (mod_insn1);
-      if (!set_src)
-	set_src = SET_SRC (set);
-    }
-  else
-    {
-      desc->inner_mode = GET_MODE (desc->var);
-      desc->extend = NIL;
-    }
-
-  if (GET_CODE (set_src) != PLUS)
-    return NULL;
-  if (!rtx_equal_p (XEXP (set_src, 0), desc->var))
-    return NULL;
-
-  /* Set desc->stride.  */
-  set_add = XEXP (set_src, 1);
-  if (CONSTANT_P (set_add))
-    desc->stride = set_add;
-  else
-    return NULL;
-
-  return mod_bb;
-}
-
-/* Tries to find initial value of VAR in INSN.  This value must be invariant
-   wrto INVARIANT_REGS.  If SET_INSN is not NULL, insn in that var is set is
-   placed here.  INNER_MODE is mode in that induction variable VAR iterates.  */
-static rtx
-variable_initial_value (rtx insn, regset invariant_regs,
-			rtx var, rtx *set_insn, enum machine_mode inner_mode)
+static void
+add_edge (struct graph *g, int f, int t, void *data)
 {
-  basic_block bb;
-  rtx set;
-  rtx ret = NULL;
-
-  /* Go back through cfg.  */
-  bb = BLOCK_FOR_INSN (insn);
-  while (1)
-    {
-      for (; insn != BB_HEAD (bb); insn = PREV_INSN (insn))
-	{
-	  if (INSN_P (insn))
-	    note_stores (PATTERN (insn),
-		(void (*) (rtx, rtx, void *)) unmark_altered,
-		invariant_regs);
-	  if (modified_between_p (var, PREV_INSN (insn), NEXT_INSN (insn)))
-	    break;
-	}
+  struct edge *e = xmalloc (sizeof (struct edge));
 
-      if (insn != BB_HEAD (bb))
-	{
-	  /* We found place where var is set.  */
-	  rtx set_dest;
-	  rtx val;
-	  rtx note;
-
-	  set = single_set (insn);
-	  if (!set)
-	    return NULL;
-	  set_dest = SET_DEST (set);
-	  if (!rtx_equal_p (set_dest, var))
-	    return NULL;
-
-	  note = find_reg_equal_equiv_note (insn);
-	  if (note && GET_CODE (XEXP (note, 0)) != EXPR_LIST)
-	    val = XEXP (note, 0);
-	  else
-	    val = SET_SRC (set);
-
-	  /* If we know that the initial value is indeed in range of
-	     the inner mode, record the fact even in case the value itself
-	     is useless.  */
-	  if ((GET_CODE (val) == SIGN_EXTEND
-	       || GET_CODE (val) == ZERO_EXTEND)
-	      && GET_MODE (XEXP (val, 0)) == inner_mode)
-	    ret = gen_rtx_fmt_e (GET_CODE (val),
-				 GET_MODE (var),
-				 gen_rtx_fmt_ei (SUBREG,
-						 inner_mode,
-						 var, 0));
-
-	  if (!invariant_rtx_wrto_regs_p (val, invariant_regs))
-	    return ret;
-
-	  if (set_insn)
-	    *set_insn = insn;
-	  return val;
-	}
+  e->src = f;
+  e->dest = t;
+  e->data = data;
 
+  e->pred_next = g->vertices[t].pred;
+  g->vertices[t].pred = e;
 
-      if (bb->pred->pred_next || bb->pred->src == ENTRY_BLOCK_PTR)
-	return NULL;
-
-      bb = bb->pred->src;
-      insn = BB_END (bb);
-    }
-
-  return NULL;
+  e->succ_next = g->vertices[f].succ;
+  g->vertices[f].succ = e;
 }
 
-/* Returns list of definitions of initial value of VAR at edge E.  INNER_MODE
-   is mode in that induction variable VAR really iterates.  */
-static rtx
-variable_initial_values (edge e, rtx var, enum machine_mode inner_mode)
-{
-  rtx set_insn, list;
-  regset invariant_regs;
-  regset_head invariant_regs_head;
-  int i;
+/* Runs dfs search over vertices of G, from NQ vertices in queue QS.
+   The vertices in postorder are stored into QT.  If FORWARD is false,
+   backward dfs is run.  */
 
-  invariant_regs = INITIALIZE_REG_SET (invariant_regs_head);
-  for (i = 0; i < max_reg_num (); i++)
-    SET_REGNO_REG_SET (invariant_regs, i);
-
-  list = alloc_EXPR_LIST (0, copy_rtx (var), NULL);
-
-  if (e->src == ENTRY_BLOCK_PTR)
-    return list;
-
-  set_insn = BB_END (e->src);
-  while (REG_P (var)
-	 && (var = variable_initial_value (set_insn, invariant_regs, var,
-					   &set_insn, inner_mode)))
-    list = alloc_EXPR_LIST (0, copy_rtx (var), list);
-
-  FREE_REG_SET (invariant_regs);
-  return list;
-}
-
-/* Counts constant number of iterations of the loop described by DESC;
-   returns false if impossible.  */
-static bool
-constant_iterations (struct loop_desc *desc, unsigned HOST_WIDE_INT *niter,
-		     bool *may_be_zero)
+static void
+dfs (struct graph *g, int *qs, int nq, int *qt, bool forward)
 {
-  rtx test, expr;
-  rtx ainit, alim;
+  int i, tick = 0, v, comp = 0, top;
+  struct edge *e;
+  struct edge **stack = xmalloc (sizeof (struct edge *) * g->n_vertices);
 
-  test = test_for_iteration (desc, 0);
-  if (test == const0_rtx)
+  for (i = 0; i < g->n_vertices; i++)
     {
-      *niter = 0;
-      *may_be_zero = false;
-      return true;
+      g->vertices[i].component = -1;
+      g->vertices[i].post = -1;
     }
 
-  *may_be_zero = (test != const_true_rtx);
+#define FST_EDGE(V) (forward ? g->vertices[(V)].succ : g->vertices[(V)].pred)
+#define NEXT_EDGE(E) (forward ? (E)->succ_next : (E)->pred_next)
+#define EDGE_SRC(E) (forward ? (E)->src : (E)->dest)
+#define EDGE_DEST(E) (forward ? (E)->dest : (E)->src)
 
-  /* It would make a little sense to check every with every when we
-     know that all but the first alternative are simply registers.  */
-  for (ainit = desc->var_alts; ainit; ainit = XEXP (ainit, 1))
-    {
-      alim = XEXP (desc->lim_alts, 0);
-      if (!(expr = count_loop_iterations (desc, XEXP (ainit, 0), alim)))
-	continue;
-      if (GET_CODE (expr) == CONST_INT)
-	{
-	  *niter = INTVAL (expr);
-	  return true;
-	}
-    }
-  for (alim = XEXP (desc->lim_alts, 1); alim; alim = XEXP (alim, 1))
+  for (i = 0; i < nq; i++)
     {
-      ainit = XEXP (desc->var_alts, 0);
-      if (!(expr = count_loop_iterations (desc, ainit, XEXP (alim, 0))))
+      v = qs[i];
+      if (g->vertices[v].post != -1)
 	continue;
-      if (GET_CODE (expr) == CONST_INT)
-	{
-	  *niter = INTVAL (expr);
-	  return true;
-	}
-    }
-
-  return false;
-}
-
-/* Attempts to determine a number of iterations of a "strange" loop.
-   Its induction variable starts with value INIT, is compared by COND
-   with LIM.  If POSTINCR, it is incremented after the test.  It is incremented
-   by STRIDE each iteration, has mode MODE but iterates in INNER_MODE.
-
-   By "strange" we mean loops where induction variable increases in the wrong
-   direction wrto comparison, i.e. for (i = 6; i > 5; i++).  */
-static rtx
-count_strange_loop_iterations (rtx init, rtx lim, enum rtx_code cond,
-			       int postincr, rtx stride, enum machine_mode mode,
-			       enum machine_mode inner_mode)
-{
-  rtx rqmt, n_to_wrap, before_wrap, after_wrap;
-  rtx mode_min, mode_max;
-  int size;
-
-  /* This could be handled, but it is not important enough to lose time with
-     it just now.  */
-  if (mode != inner_mode)
-    return NULL_RTX;
-
-  if (!postincr)
-    init = simplify_gen_binary (PLUS, mode, init, stride);
 
-  /* If we are able to prove that we don't pass the first test, we are
-     done.  */
-  rqmt = simplify_relational_operation (cond, mode, init, lim);
-  if (rqmt == const0_rtx)
-    return const0_rtx;
+      g->vertices[v].component = comp++;
+      e = FST_EDGE (v);
+      top = 0;
 
-  /* And if we don't know we pass it, the things are too complicated for us.  */
-  if (rqmt != const_true_rtx)
-    return NULL_RTX;
-
-  switch (cond)
-    {
-    case GE:
-    case GT:
-    case LE:
-    case LT:
-      size = GET_MODE_BITSIZE (mode);
-      mode_min = gen_int_mode (-((unsigned HOST_WIDEST_INT) 1 << (size - 1)),
-			       mode);
-      mode_max = gen_int_mode (((unsigned HOST_WIDEST_INT) 1 << (size - 1)) - 1,
-			       mode);
-			      
-      break;
-
-    case GEU:
-    case GTU:
-    case LEU:
-    case LTU:
-    case EQ:
-      mode_min = const0_rtx;
-      mode_max = simplify_gen_binary (MINUS, mode, const0_rtx, const1_rtx);
-      break;
-
-    default:
-      abort ();
-    }
-
-  switch (cond)
-    {
-    case EQ:
-      /* This iterates once, as init == lim.  */
-      return const1_rtx;
-
-      /* The behavior is undefined in signed cases.  Never mind, we still
-	 try to behave sanely.  */
-    case GE:
-    case GT:
-    case GEU:
-    case GTU:
-      if (INTVAL (stride) <= 0)
-	abort ();
-      n_to_wrap = simplify_gen_binary (MINUS, mode, mode_max, copy_rtx (init));
-      n_to_wrap = simplify_gen_binary (UDIV, mode, n_to_wrap, stride);
-      before_wrap = simplify_gen_binary (MULT, mode,
-					 copy_rtx (n_to_wrap), stride);
-      before_wrap = simplify_gen_binary (PLUS, mode,
-					 before_wrap, copy_rtx (init));
-      after_wrap = simplify_gen_binary (PLUS, mode,
-					before_wrap, stride);
-      if (GET_CODE (after_wrap) != CONST_INT)
+      while (1)
 	{
-	  after_wrap = simplify_gen_binary (PLUS, mode, mode_min, stride);
-	  after_wrap = simplify_gen_binary (MINUS, mode, after_wrap, const1_rtx);
-	}
-      break;
-
-    case LE:
-    case LT:
-    case LEU:
-    case LTU:
-      if (INTVAL (stride) >= 0)
-	abort ();
-      stride = simplify_gen_unary (NEG, mode, stride, mode);
-      n_to_wrap = simplify_gen_binary (MINUS, mode, copy_rtx (init), mode_min);
-      n_to_wrap = simplify_gen_binary (UDIV, mode, n_to_wrap, stride);
-      before_wrap = simplify_gen_binary (MULT, mode,
-					 copy_rtx (n_to_wrap), stride);
-      before_wrap = simplify_gen_binary (MINUS, mode,
-					 copy_rtx (init), before_wrap);
-      after_wrap = simplify_gen_binary (MINUS, mode,
-					before_wrap, stride);
-      if (GET_CODE (after_wrap) != CONST_INT)
-	{
-	  after_wrap = simplify_gen_binary (MINUS, mode, mode_max, stride);
-	  after_wrap = simplify_gen_binary (PLUS, mode, after_wrap, const1_rtx);
-	}
-      break;
-    default:
-      abort ();
-    }
-
-  /* If this is const_true_rtx and we did not take a conservative approximation
-     of after_wrap above, we might iterate the calculation (but of course we
-     would have to take care about infinite cases).  Ignore this for now.  */
-  rqmt = simplify_relational_operation (cond, mode, after_wrap, lim);
-  if (rqmt != const0_rtx)
-    return NULL_RTX;
+	  while (e && g->vertices[EDGE_DEST (e)].component != -1)
+	    e = NEXT_EDGE (e);
 
-  return simplify_gen_binary (PLUS, mode, n_to_wrap, const1_rtx);
-}
+	  if (!e)
+	    {
+	      if (qt)
+		qt[tick] = v;
+	      g->vertices[v].post = tick++;
 
-/* Checks whether value of EXPR fits into range of MODE.  */
-static bool
-fits_in_mode_p (enum machine_mode mode, rtx expr)
-{
-  unsigned HOST_WIDEST_INT val;
-  int n_bits = 0;
+	      if (!top)
+		break;
 
-  if (GET_CODE (expr) == CONST_INT)
-    {
-      for (val = INTVAL (expr); val; val >>= 1)
-	n_bits++;
+	      e = stack[--top];
+	      v = EDGE_SRC (e);
+	      e = NEXT_EDGE (e);
+	      continue;
+	    }
 
-      return n_bits <= GET_MODE_BITSIZE (mode);
+	  stack[top++] = e;
+	  v = EDGE_DEST (e);
+	  e = FST_EDGE (v);
+	  g->vertices[v].component = comp - 1;
+	}
     }
 
-  if (GET_CODE (expr) == SIGN_EXTEND
-      || GET_CODE (expr) == ZERO_EXTEND)
-    return GET_MODE (XEXP (expr, 0)) == mode;
-
-  return false;
+  free (stack);
 }
 
-/* Return RTX expression representing number of iterations of loop as bounded
-   by test described by DESC (in the case loop really has multiple exit
-   edges, fewer iterations may happen in the practice).
-
-   Return NULL if it is unknown.  Additionally the value may be invalid for
-   paradoxical loop (lets define paradoxical loops as loops whose test is
-   failing at -1th iteration, for instance "for (i=5;i<1;i++);").
-
-   These cases needs to be either cared by copying the loop test in the front
-   of loop or keeping the test in first iteration of loop.
+/* Marks the edge E in graph G irreducible if it connects two vertices in the
+   same scc.  */
 
-   When INIT/LIM are set, they are used instead of var/lim of DESC.  */
-rtx
-count_loop_iterations (struct loop_desc *desc, rtx init, rtx lim)
+static void
+check_irred (struct graph *g, struct edge *e)
 {
-  enum rtx_code cond = desc->cond;
-  rtx stride = desc->stride;
-  rtx mod, exp, ainit, bound;
-  rtx overflow_check, mx, mxp;
-  enum machine_mode mode = GET_MODE (desc->var);
-  unsigned HOST_WIDEST_INT s, size, d;
-
-  /* Give up on floating point modes and friends.  It can be possible to do
-     the job for constant loop bounds, but it is probably not worthwhile.  */
-  if (!INTEGRAL_MODE_P (mode))
-    return NULL;
-
-  init = copy_rtx (init ? init : desc->var);
-  lim = copy_rtx (lim ? lim : desc->lim);
-
-  /* Ensure that we always handle the condition to stay inside loop.  */
-  if (desc->neg)
-    cond = reverse_condition (cond);
-
-  if (desc->inner_mode != mode)
-    {
-      /* We have a case when the variable in fact iterates in the narrower
-	 mode.  This has following consequences:
-	 
-	 For induction variable itself, if !desc->postincr, it does not mean
-	 anything too special, since we know the variable is already in range
-	 of the inner mode when we compare it (so it is just needed to shorten
-	 it into the mode before calculations are done, so that we don't risk
-	 wrong results).  More complicated case is when desc->postincr; then
-	 the first two iterations are special (the first one because the value
-	 may be out of range, the second one because after shortening it to the
-	 range it may have absolutely any value), and we do not handle this in
-	 unrolling.  So if we aren't able to prove that the initial value is in
-	 the range, we fail in this case.
-	 
-	 Step is just moduled to fit into inner mode.
-
-	 If lim is out of range, then either the loop is infinite (and then
-	 we may unroll however we like to), or exits in the first iteration
-	 (this is also ok, since we handle it specially for this case anyway).
-	 So we may safely assume that it fits into the inner mode.  */
-
-      for (ainit = desc->var_alts; ainit; ainit = XEXP (ainit, 1))
-	if (fits_in_mode_p (desc->inner_mode, XEXP (ainit, 0)))
-	  break;
-
-      if (!ainit)
-	{
-	  if (desc->postincr)
-	    return NULL_RTX;
-
-	  init = simplify_gen_unary (desc->extend,
-				     mode,
-				     simplify_gen_subreg (desc->inner_mode,
-							  init,
-							  mode,
-							  0),
-				     desc->inner_mode);
-	}
-
-      stride = simplify_gen_subreg (desc->inner_mode, stride, mode, 0);
-      if (stride == const0_rtx)
-	return NULL_RTX;
-    }
-
-  /* Prepare condition to verify that we do not risk overflow.  */
-  if (stride == const1_rtx
-      || stride == constm1_rtx
-      || cond == NE
-      || cond == EQ)
-    {
-      /* Overflow at NE conditions does not occur.  EQ condition
-	 is weird and is handled in count_strange_loop_iterations.
-	 If stride is 1, overflow may occur only for <= and >= conditions,
-	 and then they are infinite, so it does not bother us.  */
-      overflow_check = const0_rtx;
-    }
-  else
-    {
-      if (cond == LT || cond == LTU)
-	mx = simplify_gen_binary (MINUS, mode, lim, const1_rtx);
-      else if (cond == GT || cond == GTU)
-	mx = simplify_gen_binary (PLUS, mode, lim, const1_rtx);
-      else
-	mx = lim;
-      if (mode != desc->inner_mode)
-	mxp = simplify_gen_subreg (desc->inner_mode, mx, mode, 0);
-      else
-	mxp = mx;
-      mxp = simplify_gen_binary (PLUS, desc->inner_mode, mxp, stride);
-      if (mode != desc->inner_mode)
-	mxp = simplify_gen_unary (desc->extend, mode, mxp, desc->inner_mode);
-      overflow_check = simplify_gen_relational (cond, SImode, mode, mx, mxp);
-    }
-    
-  /* Compute absolute value of the difference of initial and final value.  */
-  if (INTVAL (stride) > 0)
-    {
-      /* Handle strange tests specially.  */
-      if (cond == EQ || cond == GE || cond == GT || cond == GEU
-	  || cond == GTU)
-	return count_strange_loop_iterations (init, lim, cond, desc->postincr,
-					      stride, mode, desc->inner_mode);
-      exp = simplify_gen_binary (MINUS, mode, lim, init);
-    }
-  else
-    {
-      if (cond == EQ || cond == LE || cond == LT || cond == LEU
-	  || cond == LTU)
-	return count_strange_loop_iterations (init, lim, cond, desc->postincr,
-					      stride, mode, desc->inner_mode);
-      exp = simplify_gen_binary (MINUS, mode, init, lim);
-      stride = simplify_gen_unary (NEG, mode, stride, mode);
-    }
-
-  /* If there is a risk of overflow (i.e. when we increment value satisfying
-     a condition, we may again obtain a value satisfying the condition),
-     fail.  */
-  if (overflow_check != const0_rtx)
-    return NULL_RTX;
-
-  /* Normalize difference so the value is always first examined
-     and later incremented.  Do not do this for a loop ending with a branch 
-     and count register.  */
-  if (!is_bct_cond (BB_END (desc->out_edge->src)) && (!desc->postincr))
-     exp = simplify_gen_binary (MINUS, mode, exp, stride);
-
-  /* Determine delta caused by exit condition.  */
-  switch (cond)
-    {
-    case NE:
-      /* NE tests are easy to handle, because we just perform simple
-	 arithmetics modulo power of 2.  Let's use the fact to compute the
-	 number of iterations exactly.  We are now in situation when we want to
-	 solve an equation stride * i = c (mod size of inner_mode).
-	 Let nsd (stride, size of mode) = d.  If d does not divide c, the
-	 loop is infinite.  Otherwise, the number of iterations is
-	 (inverse(s/d) * (c/d)) mod (size of mode/d).  */
-      size = GET_MODE_BITSIZE (desc->inner_mode);
-      s = INTVAL (stride);
-      d = 1;
-      while (s % 2 != 1)
-	{
-	  s /= 2;
-	  d *= 2;
-	  size--;
-	}
-      bound = gen_int_mode (((unsigned HOST_WIDEST_INT) 1 << (size - 1 ) << 1) - 1,
-			    mode);
-      exp = simplify_gen_binary (UDIV, mode, exp, gen_int_mode (d, mode));
-      exp = simplify_gen_binary (MULT, mode,
-				 exp, gen_int_mode (inverse (s, size), mode));
-      exp = simplify_gen_binary (AND, mode, exp, bound);
-      break;
-
-    case LT:
-    case GT:
-    case LTU:
-    case GTU:
-      break;
-    case LE:
-    case GE:
-    case LEU:
-    case GEU:
-      exp = simplify_gen_binary (PLUS, mode, exp, const1_rtx);
-      break;
-    default:
-      abort ();
-    }
-
-  if (cond != NE && stride != const1_rtx)
-    {
-      /* Number of iterations is now (EXP + STRIDE - 1 / STRIDE),
-	 but we need to take care for overflows.  */
-
-      mod = simplify_gen_binary (UMOD, mode, exp, stride);
-
-      /* This is dirty trick.  When we can't compute number of iterations
-	 to be constant, we simply ignore the possible overflow, as
-	 runtime unroller always use power of 2 amounts and does not
-	 care about possible lost bits.  */
-
-      if (GET_CODE (mod) != CONST_INT)
-	{
-	  rtx stridem1 = simplify_gen_binary (PLUS, mode, stride, constm1_rtx);
-	  exp = simplify_gen_binary (PLUS, mode, exp, stridem1);
-	  exp = simplify_gen_binary (UDIV, mode, exp, stride);
-	}
-      else
-	{
-	  exp = simplify_gen_binary (UDIV, mode, exp, stride);
-	  if (mod != const0_rtx)
-	    exp = simplify_gen_binary (PLUS, mode, exp, const1_rtx);
-	}
-    }
+  edge real = e->data;
 
-  if (rtl_dump_file)
-    {
-      fprintf (rtl_dump_file, ";  Number of iterations: ");
-      print_simple_rtl (rtl_dump_file, exp);
-      fprintf (rtl_dump_file, "\n");
-    }
+  /* All edges should lead from a component with higher number to the
+     one with lower one.  */
+  gcc_assert (g->vertices[e->src].component >= g->vertices[e->dest].component);
 
-  return exp;
-}
-
-/* Return simplified RTX expression representing the value of test
-   described of DESC at given iteration of loop.  */
+  if (g->vertices[e->src].component != g->vertices[e->dest].component)
+    return;
 
-static rtx
-test_for_iteration (struct loop_desc *desc, unsigned HOST_WIDE_INT iter)
-{
-  enum rtx_code cond = desc->cond;
-  rtx exp = XEXP (desc->var_alts, 0);
-  rtx addval;
-
-  /* Give up on floating point modes and friends.  It can be possible to do
-     the job for constant loop bounds, but it is probably not worthwhile.  */
-  if (!INTEGRAL_MODE_P (GET_MODE (desc->var)))
-    return NULL;
-
-  /* Ensure that we always handle the condition to stay inside loop.  */
-  if (desc->neg)
-    cond = reverse_condition (cond);
-
-  /* Compute the value of induction variable.  */
-  addval = simplify_gen_binary (MULT, GET_MODE (desc->var),
-				desc->stride,
-				gen_int_mode (desc->postincr
-					      ? iter : iter + 1,
-					      GET_MODE (desc->var)));
-  exp = simplify_gen_binary (PLUS, GET_MODE (desc->var), exp, addval);
-  /* Test at given condition.  */
-  exp = simplify_gen_relational (cond, SImode,
-				 GET_MODE (desc->var), exp, desc->lim);
-
-  if (rtl_dump_file)
-    {
-      fprintf (rtl_dump_file, ";  Conditional to continue loop at "
-	       HOST_WIDE_INT_PRINT_UNSIGNED "th iteration: ", iter);
-      print_simple_rtl (rtl_dump_file, exp);
-      fprintf (rtl_dump_file, "\n");
-    }
-  return exp;
+  real->flags |= EDGE_IRREDUCIBLE_LOOP;
+  if (flow_bb_inside_loop_p (real->src->loop_father, real->dest))
+    real->src->flags |= BB_IRREDUCIBLE_LOOP;
 }
 
+/* Runs CALLBACK for all edges in G.  */
 
-/* Tests whether exit at EXIT_EDGE from LOOP is simple.  Returns simple loop
-   description joined to it in in DESC.  INVARIANT_REGS and SINGLE_SET_REGS
-   are results of blocks_{invariant,single_set}_regs over BODY.  */
-static bool
-simple_loop_exit_p (struct loop *loop, edge exit_edge,
-		    regset invariant_regs, rtx *single_set_regs,
-		    struct loop_desc *desc)
+static void
+for_each_edge (struct graph *g,
+	       void (callback) (struct graph *, struct edge *))
 {
-  basic_block mod_bb, exit_bb;
-  int fallthru_out;
-  rtx condition;
-  edge ei, e;
-
-  exit_bb = exit_edge->src;
-
-  fallthru_out = (exit_edge->flags & EDGE_FALLTHRU);
-
-  if (!exit_bb)
-    return false;
-
-  /* It must be tested (at least) once during any iteration.  */
-  if (!dominated_by_p (CDI_DOMINATORS, loop->latch, exit_bb))
-    return false;
-
-  /* It must end in a simple conditional jump.  */
-  if (!any_condjump_p (BB_END (exit_bb)))
-    return false;
-
-  ei = exit_bb->succ;
-  if (ei == exit_edge)
-    ei = ei->succ_next;
-
-  desc->out_edge = exit_edge;
-  desc->in_edge = ei;
-
-  /* Condition must be a simple comparison in that one of operands
-     is register and the other one is invariant.  */
-  if (!(condition = get_condition (BB_END (exit_bb), NULL, false)))
-    return false;
-
-  if (!simple_condition_p (loop, condition, invariant_regs, desc))
-    return false;
-
-  /*  Var must be simply incremented or decremented in exactly one insn that
-     is executed just once every iteration.  */
-  if (!(mod_bb = simple_increment (loop, single_set_regs, desc)))
-    return false;
-
-  /* OK, it is simple loop.  Now just fill in remaining info.  */
-  desc->postincr = !dominated_by_p (CDI_DOMINATORS, exit_bb, mod_bb);
-  desc->neg = !fallthru_out;
-
-  /* Find initial value of var and alternative values for lim.  */
-  e = loop_preheader_edge (loop);
-  desc->var_alts = variable_initial_values (e, desc->var, desc->inner_mode);
-  desc->lim_alts = variable_initial_values (e, desc->lim, desc->inner_mode);
+  struct edge *e;
+  int i;
 
-  /* Number of iterations.  */
-  desc->const_iter =
-    constant_iterations (desc, &desc->niter, &desc->may_be_zero);
-  if (!desc->const_iter && !count_loop_iterations (desc, NULL, NULL))
-    return false;
-  return true;
+  for (i = 0; i < g->n_vertices; i++)
+    for (e = g->vertices[i].succ; e; e = e->succ_next)
+      callback (g, e);
 }
 
-/* Tests whether LOOP is simple for loop.  Returns simple loop description
-   in DESC.  */
-bool
-simple_loop_p (struct loop *loop, struct loop_desc *desc)
-{
-  unsigned i;
-  basic_block *body;
-  edge e;
-  struct loop_desc act;
-  bool any = false;
-  regset invariant_regs;
-  regset_head invariant_regs_head;
-  rtx *single_set_regs;
-  int n_branches;
-
-  body = get_loop_body (loop);
-
-  invariant_regs = INITIALIZE_REG_SET (invariant_regs_head);
-  single_set_regs = xmalloc (max_reg_num () * sizeof (rtx));
+/* Releases the memory occupied by G.  */
 
-  blocks_invariant_registers (body, loop->num_nodes, invariant_regs);
-  blocks_single_set_registers (body, loop->num_nodes, single_set_regs);
-
-  n_branches = 0;
-  for (i = 0; i < loop->num_nodes; i++)
-    {
-      for (e = body[i]->succ; e; e = e->succ_next)
-	if (!flow_bb_inside_loop_p (loop, e->dest)
-	    && simple_loop_exit_p (loop, e,
-		   invariant_regs, single_set_regs, &act))
-	  {
-	    /* Prefer constant iterations; the less the better.  */
-	    if (!any)
-	      any = true;
-	    else if (!act.const_iter
-		     || (desc->const_iter && act.niter >= desc->niter))
-	      continue;
-	    *desc = act;
-	  }
-
-      if (body[i]->succ && body[i]->succ->succ_next)
-	n_branches++;
-    }
-  desc->n_branches = n_branches;
-
-  if (rtl_dump_file && any)
-    {
-      fprintf (rtl_dump_file, "; Simple loop %i\n", loop->num);
-      if (desc->postincr)
-	fprintf (rtl_dump_file,
-		 ";  does postincrement after loop exit condition\n");
-
-      fprintf (rtl_dump_file, ";  Induction variable:");
-      print_simple_rtl (rtl_dump_file, desc->var);
-      fputc ('\n', rtl_dump_file);
-
-      fprintf (rtl_dump_file, ";  Initial values:");
-      print_simple_rtl (rtl_dump_file, desc->var_alts);
-      fputc ('\n', rtl_dump_file);
-
-      fprintf (rtl_dump_file, ";  Stride:");
-      print_simple_rtl (rtl_dump_file, desc->stride);
-      fputc ('\n', rtl_dump_file);
-
-      fprintf (rtl_dump_file, ";  Compared with:");
-      print_simple_rtl (rtl_dump_file, desc->lim);
-      fputc ('\n', rtl_dump_file);
-
-      fprintf (rtl_dump_file, ";  Alternative values:");
-      print_simple_rtl (rtl_dump_file, desc->lim_alts);
-      fputc ('\n', rtl_dump_file);
-
-      fprintf (rtl_dump_file, ";  Exit condition:");
-      if (desc->neg)
-	fprintf (rtl_dump_file, "(negated)");
-      fprintf (rtl_dump_file, "%s\n", GET_RTX_NAME (desc->cond));
-
-      fprintf (rtl_dump_file, ";  Number of branches:");
-      fprintf (rtl_dump_file, "%d\n", desc->n_branches);
-
-      fputc ('\n', rtl_dump_file);
-    }
+static void
+free_graph (struct graph *g)
+{
+  struct edge *e, *n;
+  int i;
 
-  free (body);
-  FREE_REG_SET (invariant_regs);
-  free (single_set_regs);
-  return any;
+  for (i = 0; i < g->n_vertices; i++)
+    for (e = g->vertices[i].succ; e; e = n)
+      {
+	n = e->succ_next;
+	free (e);
+      }
+  free (g->vertices);
+  free (g);
 }
 
 /* Marks blocks and edges that are part of non-recognized loops; i.e. we
@@ -1130,196 +258,102 @@ simple_loop_p (struct loop *loop, struct loop_desc *desc)
    Everything is a bit complicated due to fact we do not want to do this
    for parts of cycles that only "pass" through some loop -- i.e. for
    each cycle, we want to mark blocks that belong directly to innermost
-   loop containing the whole cycle.  */
+   loop containing the whole cycle.
+
+   LOOPS is the loop tree.  */
+
+#define LOOP_REPR(LOOP) ((LOOP)->num + last_basic_block)
+#define BB_REPR(BB) ((BB)->index + 1)
+
 void
 mark_irreducible_loops (struct loops *loops)
 {
-  int *dfs_in, *closed, *mr, *mri, *n_edges, *stack;
-  unsigned i;
-  edge **edges, e;
-  edge *estack;
   basic_block act;
-  int stack_top, tick, depth;
+  edge e;
+  edge_iterator ei;
+  int i, src, dest;
+  struct graph *g;
+  int *queue1 = XNEWVEC (int, last_basic_block + loops->num);
+  int *queue2 = XNEWVEC (int, last_basic_block + loops->num);
+  int nq, depth;
   struct loop *cloop;
 
   /* Reset the flags.  */
   FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
     {
       act->flags &= ~BB_IRREDUCIBLE_LOOP;
-      for (e = act->succ; e; e = e->succ_next)
+      FOR_EACH_EDGE (e, ei, act->succs)
 	e->flags &= ~EDGE_IRREDUCIBLE_LOOP;
     }
 
-  /* The first last_basic_block + 1 entries are for real blocks (including
-     entry); then we have loops->num - 1 fake blocks for loops to that we
-     assign edges leading from loops (fake loop 0 is not interesting).  */
-  dfs_in = xmalloc ((last_basic_block + loops->num) * sizeof (int));
-  closed = xmalloc ((last_basic_block + loops->num) * sizeof (int));
-  mr = xmalloc ((last_basic_block + loops->num) * sizeof (int));
-  mri = xmalloc ((last_basic_block + loops->num) * sizeof (int));
-  n_edges = xmalloc ((last_basic_block + loops->num) * sizeof (int));
-  edges = xmalloc ((last_basic_block + loops->num) * sizeof (edge *));
-  stack = xmalloc ((n_basic_blocks + loops->num) * sizeof (int));
-  estack = xmalloc ((n_basic_blocks + loops->num) * sizeof (edge));
-
   /* Create the edge lists.  */
-  for (i = 0; i < last_basic_block + loops->num; i++)
-    n_edges[i] = 0;
+  g = new_graph (last_basic_block + loops->num);
+
   FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
-    for (e = act->succ; e; e = e->succ_next)
+    FOR_EACH_EDGE (e, ei, act->succs)
       {
-        /* Ignore edges to exit.  */
-        if (e->dest == EXIT_BLOCK_PTR)
+	/* Ignore edges to exit.  */
+	if (e->dest == EXIT_BLOCK_PTR)
 	  continue;
+
 	/* And latch edges.  */
 	if (e->dest->loop_father->header == e->dest
 	    && e->dest->loop_father->latch == act)
 	  continue;
+
 	/* Edges inside a single loop should be left where they are.  Edges
 	   to subloop headers should lead to representative of the subloop,
-	   but from the same place.  */
-	if (act->loop_father == e->dest->loop_father
-	    || act->loop_father == e->dest->loop_father->outer)
-	  {
-	    n_edges[act->index + 1]++;
-	    continue;
-	  }
-	/* Edges exiting loops remain.  They should lead from representative
+	   but from the same place.
+
+	   Edges exiting loops should lead from representative
 	   of the son of nearest common ancestor of the loops in that
 	   act lays.  */
-	depth = find_common_loop (act->loop_father, e->dest->loop_father)->depth + 1;
-	if (depth == act->loop_father->depth)
-	  cloop = act->loop_father;
-	else
-	  cloop = act->loop_father->pred[depth];
-	n_edges[cloop->num + last_basic_block]++;
-      }
 
-  for (i = 0; i < last_basic_block + loops->num; i++)
-    {
-      edges[i] = xmalloc (n_edges[i] * sizeof (edge));
-      n_edges[i] = 0;
-    }
+	src = BB_REPR (act);
+	dest = BB_REPR (e->dest);
 
-  FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
-    for (e = act->succ; e; e = e->succ_next)
-      {
-        if (e->dest == EXIT_BLOCK_PTR)
-	  continue;
-	if (e->dest->loop_father->header == e->dest
-	    && e->dest->loop_father->latch == act)
-	  continue;
-	if (act->loop_father == e->dest->loop_father
-	    || act->loop_father == e->dest->loop_father->outer)
+	if (e->dest->loop_father->header == e->dest)
+	  dest = LOOP_REPR (e->dest->loop_father);
+
+	if (!flow_bb_inside_loop_p (act->loop_father, e->dest))
 	  {
-	    edges[act->index + 1][n_edges[act->index + 1]++] = e;
-	    continue;
+	    depth = find_common_loop (act->loop_father,
+				      e->dest->loop_father)->depth + 1;
+	    if (depth == act->loop_father->depth)
+	      cloop = act->loop_father;
+	    else
+	      cloop = act->loop_father->pred[depth];
+
+	    src = LOOP_REPR (cloop);
 	  }
-	depth = find_common_loop (act->loop_father, e->dest->loop_father)->depth + 1;
-	if (depth == act->loop_father->depth)
-	  cloop = act->loop_father;
-	else
-	  cloop = act->loop_father->pred[depth];
-	i = cloop->num + last_basic_block;
-	edges[i][n_edges[i]++] = e;
+
+	add_edge (g, src, dest, e);
       }
 
-  /* Compute dfs numbering, starting from loop headers, and mark found
-     loops.  */
-  tick = 0;
-  for (i = 0; i < last_basic_block + loops->num; i++)
+  /* Find the strongly connected components.  Use the algorithm of Tarjan --
+     first determine the postorder dfs numbering in reversed graph, then
+     run the dfs on the original graph in the order given by decreasing
+     numbers assigned by the previous pass.  */
+  nq = 0;
+  FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
     {
-      dfs_in[i] = -1;
-      closed[i] = 0;
-      mr[i] = last_basic_block + loops->num;
-      mri[i] = -1;
+      queue1[nq++] = BB_REPR (act);
     }
-
-  stack_top = 0;
-  for (i = 0; i < loops->num; i++)
+  for (i = 1; i < (int) loops->num; i++)
     if (loops->parray[i])
-      {
-	stack[stack_top] = loops->parray[i]->header->index + 1;
-	estack[stack_top] = NULL;
-	stack_top++;
-      }
+      queue1[nq++] = LOOP_REPR (loops->parray[i]);
+  dfs (g, queue1, nq, queue2, false);
+  for (i = 0; i < nq; i++)
+    queue1[i] = queue2[nq - i - 1];
+  dfs (g, queue1, nq, NULL, true);
 
-  while (stack_top)
-    {
-      int idx, sidx;
-
-      idx = stack[stack_top - 1];
-      if (dfs_in[idx] < 0)
-	dfs_in[idx] = tick++;
-
-      while (n_edges[idx])
-	{
-	  e = edges[idx][--n_edges[idx]];
-	  sidx = e->dest->loop_father->header == e->dest
-	           ? e->dest->loop_father->num + last_basic_block
-	           : e->dest->index + 1;
-          if (closed[sidx])
-	    {
-	      if (mri[sidx] != -1 && !closed[mri[sidx]])
-		{
-		  if (mr[sidx] < mr[idx])
-		    {
-		      mr[idx] = mr[sidx];
-		      mri[idx] = mri[sidx];
-		    }
-
-		  if (mr[sidx] <= dfs_in[idx])
-		    e->flags |= EDGE_IRREDUCIBLE_LOOP;
-		}
-	      continue;
-	    }
-	  if (dfs_in[sidx] < 0)
-	    {
-	      stack[stack_top] = sidx;
-	      estack[stack_top] = e;
-	      stack_top++;
-	      goto next;
-	    }
-	  if (dfs_in[sidx] < mr[idx])
-	    {
-	      mr[idx] = dfs_in[sidx];
-	      mri[idx] = sidx;
-	    }
-	  e->flags |= EDGE_IRREDUCIBLE_LOOP;
-	}
+  /* Mark the irreducible loops.  */
+  for_each_edge (g, check_irred);
 
-      /* Return back.  */
-      closed[idx] = 1;
-      e = estack[stack_top - 1];
-      stack_top--;
-      if (e)
-        {
-	  /* Propagate information back.  */
-	  sidx = stack[stack_top - 1];
-	  if (mr[sidx] > mr[idx])
-	    {
-	      mr[sidx] = mr[idx];
-	      mri[sidx] = mri[idx];
-	    }
-	  if (mr[idx] <= dfs_in[sidx])
-	    e->flags |= EDGE_IRREDUCIBLE_LOOP;
-	}
-      /* Mark the block if relevant.  */
-      if (idx && idx <= last_basic_block && mr[idx] <= dfs_in[idx])
-        BASIC_BLOCK (idx - 1)->flags |= BB_IRREDUCIBLE_LOOP;
-next:;
-    }
+  free_graph (g);
+  free (queue1);
+  free (queue2);
 
-  free (stack);
-  free (estack);
-  free (dfs_in);
-  free (closed);
-  free (mr);
-  free (mri);
-  for (i = 0; i < last_basic_block + loops->num; i++)
-    free (edges[i]);
-  free (edges);
-  free (n_edges);
   loops->state |= LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS;
 }
 
@@ -1385,24 +419,25 @@ unsigned
 expected_loop_iterations (const struct loop *loop)
 {
   edge e;
+  edge_iterator ei;
 
-  if (loop->header->count)
+  if (loop->latch->count || loop->header->count)
     {
       gcov_type count_in, count_latch, expected;
 
       count_in = 0;
       count_latch = 0;
 
-      for (e = loop->header->pred; e; e = e->pred_next)
+      FOR_EACH_EDGE (e, ei, loop->header->preds)
 	if (e->src == loop->latch)
 	  count_latch = e->count;
 	else
 	  count_in += e->count;
 
       if (count_in == 0)
-	return 0;
-
-      expected = (count_latch + count_in - 1) / count_in;
+	expected = count_latch * 2;
+      else
+	expected = (count_latch + count_in - 1) / count_in;
 
       /* Avoid overflows.  */
       return (expected > REG_BR_PROB_BASE ? REG_BR_PROB_BASE : expected);
@@ -1414,69 +449,147 @@ expected_loop_iterations (const struct loop *loop)
       freq_in = 0;
       freq_latch = 0;
 
-      for (e = loop->header->pred; e; e = e->pred_next)
+      FOR_EACH_EDGE (e, ei, loop->header->preds)
 	if (e->src == loop->latch)
 	  freq_latch = EDGE_FREQUENCY (e);
 	else
 	  freq_in += EDGE_FREQUENCY (e);
 
       if (freq_in == 0)
-	return 0;
+	return freq_latch * 2;
 
       return (freq_latch + freq_in - 1) / freq_in;
     }
 }
 
-/* This function checks if an instruction is a branch and count instruction
-   no matter if the flag HAVE_doloop_end is enabled or not.  An alternative 
-   would be the modification of doloop_condition_get function itself.  */ 
-bool
-is_bct_cond (rtx insn) 
-{
-  if (GET_CODE (insn) != JUMP_INSN)
-    return false;
+/* Returns the maximum level of nesting of subloops of LOOP.  */
 
-#ifdef HAVE_doloop_end
-  if (!doloop_condition_get (PATTERN(insn)))
-    return false;
-#else
-  return false;
-#endif
+unsigned
+get_loop_level (const struct loop *loop)
+{
+  const struct loop *ploop;
+  unsigned mx = 0, l;
 
-  return true;
+  for (ploop = loop->inner; ploop; ploop = ploop->next)
+    {
+      l = get_loop_level (ploop);
+      if (l >= mx)
+	mx = l + 1;
+    }
+  return mx;
 }
 
-/* Extract the increment of the count register from the branch and count
-   instruction.  */ 
-rtx
-get_var_set_from_bct (rtx insn)
+/* Returns estimate on cost of computing SEQ.  */
+
+static unsigned
+seq_cost (rtx seq)
 {
-  rtx rhs, lhs, cond;
-  rtx pattern;
+  unsigned cost = 0;
   rtx set;
-  pattern = PATTERN (insn);
-
-  if (!is_bct_cond (insn))
-    abort ();
-
-  set = XVECEXP (pattern, 0, 1);
-
-  /* IA64 has the decrement conditional, i.e. done only when the loop does not 
-     end.  We match (set (x (if_then_else (ne x 0) (plus x -1) x))) here.  */
-
-  lhs = XEXP (set, 0);
-  rhs = XEXP (set, 1);
-  if (GET_CODE (set) != IF_THEN_ELSE)
-    return set;
- 
-  cond = XEXP (rhs, 0);
-  if (GET_CODE (cond) != NE
-      || !rtx_equal_p (XEXP (cond, 0), lhs)
-      || !rtx_equal_p (XEXP (cond, 1), const0_rtx))
-         return set;
-
-  rhs = XEXP (rhs, 1);
- 
-  return gen_rtx_SET (GET_MODE (lhs), lhs, rhs);
+
+  for (; seq; seq = NEXT_INSN (seq))
+    {
+      set = single_set (seq);
+      if (set)
+	cost += rtx_cost (set, SET);
+      else
+	cost++;
+    }
+
+  return cost;
+}
+
+/* The properties of the target.  */
+
+unsigned target_avail_regs;	/* Number of available registers.  */
+unsigned target_res_regs;	/* Number of reserved registers.  */
+unsigned target_small_cost;	/* The cost for register when there is a free one.  */
+unsigned target_pres_cost;	/* The cost for register when there are not too many
+				   free ones.  */
+unsigned target_spill_cost;	/* The cost for register when we need to spill.  */
+
+/* Initialize the constants for computing set costs.  */
+
+void
+init_set_costs (void)
+{
+  rtx seq;
+  rtx reg1 = gen_raw_REG (SImode, FIRST_PSEUDO_REGISTER);
+  rtx reg2 = gen_raw_REG (SImode, FIRST_PSEUDO_REGISTER + 1);
+  rtx addr = gen_raw_REG (Pmode, FIRST_PSEUDO_REGISTER + 2);
+  rtx mem = validize_mem (gen_rtx_MEM (SImode, addr));
+  unsigned i;
+
+  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+    if (TEST_HARD_REG_BIT (reg_class_contents[GENERAL_REGS], i)
+	&& !fixed_regs[i])
+      target_avail_regs++;
+
+  target_res_regs = 3;
+
+  /* These are really just heuristic values.  */
+
+  start_sequence ();
+  emit_move_insn (reg1, reg2);
+  seq = get_insns ();
+  end_sequence ();
+  target_small_cost = seq_cost (seq);
+  target_pres_cost = 2 * target_small_cost;
+
+  start_sequence ();
+  emit_move_insn (mem, reg1);
+  emit_move_insn (reg2, mem);
+  seq = get_insns ();
+  end_sequence ();
+  target_spill_cost = seq_cost (seq);
+}
+
+/* Calculates cost for having SIZE new loop global variables.  REGS_USED is the
+   number of global registers used in loop.  N_USES is the number of relevant
+   variable uses.  */
+
+unsigned
+global_cost_for_size (unsigned size, unsigned regs_used, unsigned n_uses)
+{
+  unsigned regs_needed = regs_used + size;
+  unsigned cost = 0;
+
+  if (regs_needed + target_res_regs <= target_avail_regs)
+    cost += target_small_cost * size;
+  else if (regs_needed <= target_avail_regs)
+    cost += target_pres_cost * size;
+  else
+    {
+      cost += target_pres_cost * size;
+      cost += target_spill_cost * n_uses * (regs_needed - target_avail_regs) / regs_needed;
+    }
+
+  return cost;
+}
+
+/* Sets EDGE_LOOP_EXIT flag for all exits of LOOPS.  */
+
+void
+mark_loop_exit_edges (struct loops *loops)
+{
+  basic_block bb;
+  edge e;
+
+  if (loops->num <= 1)
+    return;
+
+  FOR_EACH_BB (bb)
+    {
+      edge_iterator ei;
+
+      FOR_EACH_EDGE (e, ei, bb->succs)
+	{
+	  if (bb->loop_father->outer
+	      && loop_exit_edge_p (bb->loop_father, e))
+	    e->flags |= EDGE_LOOP_EXIT;
+	  else
+	    e->flags &= ~EDGE_LOOP_EXIT;
+	}
+    }
 }