Use range-based for loops for traversing loops

This patch follows Martin's suggestion here[1], to support
range based loop for iterating loops, analogously to the
patch for vec[2].

For example, use below range-based for loop

    for (auto loop : loops_list (cfun, 0))

to replace the previous macro FOR_EACH_LOOP

    FOR_EACH_LOOP (loop, 0)

[1] https://gcc.gnu.org/pipermail/gcc-patches/2021-June/573424.html
[2] https://gcc.gnu.org/pipermail/gcc-patches/2021-June/572315.html

gcc/ChangeLog:

	* cfgloop.h (as_const): New function.
	(class loop_iterator): Rename to ...
	(class loops_list): ... this.
	(loop_iterator::next): Rename to ...
	(loops_list::Iter::fill_curr_loop): ... this and adjust.
	(loop_iterator::loop_iterator): Rename to ...
	(loops_list::loops_list): ... this and adjust.
	(loops_list::Iter): New class.
	(loops_list::iterator): New type.
	(loops_list::const_iterator): New type.
	(loops_list::begin): New function.
	(loops_list::end): Likewise.
	(loops_list::begin const): Likewise.
	(loops_list::end const): Likewise.
	(FOR_EACH_LOOP): Remove.
	(FOR_EACH_LOOP_FN): Remove.
	* cfgloop.c (flow_loops_dump): Adjust FOR_EACH_LOOP* with range-based
	for loop with loops_list instance.
	(sort_sibling_loops): Likewise.
	(disambiguate_loops_with_multiple_latches): Likewise.
	(verify_loop_structure): Likewise.
	* cfgloopmanip.c (create_preheaders): Likewise.
	(force_single_succ_latches): Likewise.
	* config/aarch64/falkor-tag-collision-avoidance.c
	(execute_tag_collision_avoidance): Likewise.
	* config/mn10300/mn10300.c (mn10300_scan_for_setlb_lcc): Likewise.
	* config/s390/s390.c (s390_adjust_loops): Likewise.
	* doc/loop.texi: Likewise.
	* gimple-loop-interchange.cc (pass_linterchange::execute): Likewise.
	* gimple-loop-jam.c (tree_loop_unroll_and_jam): Likewise.
	* gimple-loop-versioning.cc (loop_versioning::analyze_blocks): Likewise.
	(loop_versioning::make_versioning_decisions): Likewise.
	* gimple-ssa-split-paths.c (split_paths): Likewise.
	* graphite-isl-ast-to-gimple.c (graphite_regenerate_ast_isl): Likewise.
	* graphite.c (canonicalize_loop_form): Likewise.
	(graphite_transform_loops): Likewise.
	* ipa-fnsummary.c (analyze_function_body): Likewise.
	* ipa-pure-const.c (analyze_function): Likewise.
	* loop-doloop.c (doloop_optimize_loops): Likewise.
	* loop-init.c (loop_optimizer_finalize): Likewise.
	(fix_loop_structure): Likewise.
	* loop-invariant.c (calculate_loop_reg_pressure): Likewise.
	(move_loop_invariants): Likewise.
	* loop-unroll.c (decide_unrolling): Likewise.
	(unroll_loops): Likewise.
	* modulo-sched.c (sms_schedule): Likewise.
	* predict.c (predict_loops): Likewise.
	(pass_profile::execute): Likewise.
	* profile.c (branch_prob): Likewise.
	* sel-sched-ir.c (sel_finish_pipelining): Likewise.
	(sel_find_rgns): Likewise.
	* tree-cfg.c (replace_loop_annotate): Likewise.
	(replace_uses_by): Likewise.
	(move_sese_region_to_fn): Likewise.
	* tree-if-conv.c (pass_if_conversion::execute): Likewise.
	* tree-loop-distribution.c (loop_distribution::execute): Likewise.
	* tree-parloops.c (parallelize_loops): Likewise.
	* tree-predcom.c (tree_predictive_commoning): Likewise.
	* tree-scalar-evolution.c (scev_initialize): Likewise.
	(scev_reset): Likewise.
	* tree-ssa-dce.c (find_obviously_necessary_stmts): Likewise.
	* tree-ssa-live.c (remove_unused_locals): Likewise.
	* tree-ssa-loop-ch.c (ch_base::copy_headers): Likewise.
	* tree-ssa-loop-im.c (analyze_memory_references): Likewise.
	(tree_ssa_lim_initialize): Likewise.
	* tree-ssa-loop-ivcanon.c (canonicalize_induction_variables): Likewise.
	* tree-ssa-loop-ivopts.c (tree_ssa_iv_optimize): Likewise.
	* tree-ssa-loop-manip.c (get_loops_exits): Likewise.
	* tree-ssa-loop-niter.c (estimate_numbers_of_iterations): Likewise.
	(free_numbers_of_iterations_estimates): Likewise.
	* tree-ssa-loop-prefetch.c (tree_ssa_prefetch_arrays): Likewise.
	* tree-ssa-loop-split.c (tree_ssa_split_loops): Likewise.
	* tree-ssa-loop-unswitch.c (tree_ssa_unswitch_loops): Likewise.
	* tree-ssa-loop.c (gate_oacc_kernels): Likewise.
	(pass_scev_cprop::execute): Likewise.
	* tree-ssa-propagate.c (clean_up_loop_closed_phi): Likewise.
	* tree-ssa-sccvn.c (do_rpo_vn): Likewise.
	* tree-ssa-threadupdate.c
	(jump_thread_path_registry::thread_through_all_blocks): Likewise.
	* tree-vectorizer.c (vectorize_loops): Likewise.
	* tree-vrp.c (vrp_asserts::find_assert_locations): Likewise.

46 files changed, 194 insertions, 195 deletions

diff --git a/gcc/cfgloop.c b/gcc/cfgloop.c
index f094538..6284ae2 100644
--- a/gcc/cfgloop.c
+++ b/gcc/cfgloop.c
@@ -162,14 +162,12 @@ flow_loop_dump (const class loop *loop, FILE *file,
 void
 flow_loops_dump (FILE *file, void (*loop_dump_aux) (const class loop *, FILE *, int), int verbose)
 {
-  class loop *loop;
-
   if (!current_loops || ! file)
     return;
 
   fprintf (file, ";; %d loops found\n", number_of_loops (cfun));
 
-  FOR_EACH_LOOP (loop, LI_INCLUDE_ROOT)
+  for (auto loop : loops_list (cfun, LI_INCLUDE_ROOT))
     {
       flow_loop_dump (loop, file, loop_dump_aux, verbose);
     }
@@ -559,8 +557,7 @@ sort_sibling_loops (function *fn)
   free (rc_order);
 
   auto_vec<loop_p, 3> siblings;
-  loop_p loop;
-  FOR_EACH_LOOP_FN (fn, loop, LI_INCLUDE_ROOT)
+  for (auto loop : loops_list (fn, LI_INCLUDE_ROOT))
     if (loop->inner && loop->inner->next)
       {
 	loop_p sibling = loop->inner;
@@ -836,9 +833,7 @@ disambiguate_multiple_latches (class loop *loop)
 void
 disambiguate_loops_with_multiple_latches (void)
 {
-  class loop *loop;
-
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     {
       if (!loop->latch)
 	disambiguate_multiple_latches (loop);
@@ -1457,7 +1452,7 @@ verify_loop_structure (void)
   auto_sbitmap visited (last_basic_block_for_fn (cfun));
   bitmap_clear (visited);
   bbs = XNEWVEC (basic_block, n_basic_blocks_for_fn (cfun));
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       unsigned n;
 
@@ -1503,7 +1498,7 @@ verify_loop_structure (void)
   free (bbs);
 
   /* Check headers and latches.  */
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     {
       i = loop->num;
       if (loop->header == NULL)
@@ -1629,7 +1624,7 @@ verify_loop_structure (void)
     }
 
   /* Check the recorded loop exits.  */
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     {
       if (!loop->exits || loop->exits->e != NULL)
 	{
@@ -1723,7 +1718,7 @@ verify_loop_structure (void)
 	  err = 1;
 	}
 
-      FOR_EACH_LOOP (loop, 0)
+      for (auto loop : loops_list (cfun, 0))
 	{
 	  eloops = 0;
 	  for (exit = loop->exits->next; exit->e; exit = exit->next)
diff --git a/gcc/cfgloop.h b/gcc/cfgloop.h
index 5c2b98d..885632b 100644
--- a/gcc/cfgloop.h
+++ b/gcc/cfgloop.h
@@ -658,55 +658,141 @@ enum li_flags
   LI_ONLY_INNERMOST = 4		/* Iterate only over innermost loops.  */
 };
 
-/* The iterator for loops.  */
+/* Provide the functionality of std::as_const to support range-based for
+   to use const iterator.  (We can't use std::as_const itself because it's
+   a C++17 feature.)  */
+template <typename T>
+constexpr const T &
+as_const (T &t)
+{
+  return t;
+}
+
+/* A list for visiting loops, which contains the loop numbers instead of
+   the loop pointers.  The scope is restricted in function FN and the
+   visiting order is specified by FLAGS.  */
 
-class loop_iterator
+class loops_list
 {
 public:
-  loop_iterator (function *fn, loop_p *loop, unsigned flags);
+  loops_list (function *fn, unsigned flags);
+
+  template <typename T> class Iter
+  {
+  public:
+    Iter (const loops_list &l, unsigned idx) : list (l), curr_idx (idx)
+    {
+      fill_curr_loop ();
+    }
+
+    T operator* () const { return curr_loop; }
+
+    Iter &
+    operator++ ()
+    {
+      if (curr_idx < list.to_visit.length ())
+	{
+	  /* Bump the index and fill a new one.  */
+	  curr_idx++;
+	  fill_curr_loop ();
+	}
+      else
+	gcc_assert (!curr_loop);
+
+      return *this;
+    }
+
+    bool
+    operator!= (const Iter &rhs) const
+    {
+      return this->curr_idx != rhs.curr_idx;
+    }
+
+  private:
+    /* Fill the current loop starting from the current index.  */
+    void fill_curr_loop ();
+
+    /* Reference to the loop list to visit.  */
+    const loops_list &list;
+
+    /* The current index in the list to visit.  */
+    unsigned curr_idx;
 
-  inline loop_p next ();
+    /* The loop implied by the current index.  */
+    class loop *curr_loop;
+  };
 
+  using iterator = Iter<class loop *>;
+  using const_iterator = Iter<const class loop *>;
+
+  iterator
+  begin ()
+  {
+    return iterator (*this, 0);
+  }
+
+  iterator
+  end ()
+  {
+    return iterator (*this, to_visit.length ());
+  }
+
+  const_iterator
+  begin () const
+  {
+    return const_iterator (*this, 0);
+  }
+
+  const_iterator
+  end () const
+  {
+    return const_iterator (*this, to_visit.length ());
+  }
+
+private:
   /* The function we are visiting.  */
   function *fn;
 
   /* The list of loops to visit.  */
   auto_vec<int, 16> to_visit;
-
-  /* The index of the actual loop.  */
-  unsigned idx;
 };
 
-inline loop_p
-loop_iterator::next ()
+/* Starting from current index CURR_IDX (inclusive), find one index
+   which stands for one valid loop and fill the found loop as CURR_LOOP,
+   if we can't find one, set CURR_LOOP as null.  */
+
+template <typename T>
+inline void
+loops_list::Iter<T>::fill_curr_loop ()
 {
   int anum;
 
-  while (this->to_visit.iterate (this->idx, &anum))
+  while (this->list.to_visit.iterate (this->curr_idx, &anum))
     {
-      this->idx++;
-      loop_p loop = get_loop (fn, anum);
+      class loop *loop = get_loop (this->list.fn, anum);
       if (loop)
-	return loop;
+	{
+	  curr_loop = loop;
+	  return;
+	}
+      this->curr_idx++;
     }
 
-  return NULL;
+  curr_loop = nullptr;
 }
 
-inline
-loop_iterator::loop_iterator (function *fn, loop_p *loop, unsigned flags)
+/* Set up the loops list to visit according to the specified
+   function scope FN and iterating order FLAGS.  */
+
+inline loops_list::loops_list (function *fn, unsigned flags)
 {
   class loop *aloop;
   unsigned i;
   int mn;
 
-  this->idx = 0;
   this->fn = fn;
   if (!loops_for_fn (fn))
-    {
-      *loop = NULL;
-      return;
-    }
+    return;
 
   this->to_visit.reserve_exact (number_of_loops (fn));
   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
@@ -766,20 +852,8 @@ loop_iterator::loop_iterator (function *fn, loop_p *loop, unsigned flags)
 	    }
 	}
     }
-
-  *loop = this->next ();
 }
 
-#define FOR_EACH_LOOP(LOOP, FLAGS) \
-  for (loop_iterator li(cfun, &(LOOP), FLAGS); \
-       (LOOP); \
-       (LOOP) = li.next ())
-
-#define FOR_EACH_LOOP_FN(FN, LOOP, FLAGS) \
-  for (loop_iterator li(FN, &(LOOP), FLAGS); \
-       (LOOP); \
-       (LOOP) = li.next ())
-
 /* The properties of the target.  */
 struct target_cfgloop {
   /* Number of available registers.  */
diff --git a/gcc/cfgloopmanip.c b/gcc/cfgloopmanip.c
index 2af59fe..82c242d 100644
--- a/gcc/cfgloopmanip.c
+++ b/gcc/cfgloopmanip.c
@@ -1572,12 +1572,10 @@ create_preheader (class loop *loop, int flags)
 void
 create_preheaders (int flags)
 {
-  class loop *loop;
-
   if (!current_loops)
     return;
 
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     create_preheader (loop, flags);
   loops_state_set (LOOPS_HAVE_PREHEADERS);
 }
@@ -1587,10 +1585,9 @@ create_preheaders (int flags)
 void
 force_single_succ_latches (void)
 {
-  class loop *loop;
   edge e;
 
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     {
       if (loop->latch != loop->header && single_succ_p (loop->latch))
 	continue;
diff --git a/gcc/config/aarch64/falkor-tag-collision-avoidance.c b/gcc/config/aarch64/falkor-tag-collision-avoidance.c
index de214e4..6c8e02a 100644
--- a/gcc/config/aarch64/falkor-tag-collision-avoidance.c
+++ b/gcc/config/aarch64/falkor-tag-collision-avoidance.c
@@ -808,8 +808,6 @@ record_loads (tag_map_t &tag_map, struct loop *loop)
 void
 execute_tag_collision_avoidance ()
 {
-  struct loop *loop;
-
   df_set_flags (DF_RD_PRUNE_DEAD_DEFS);
   df_chain_add_problem (DF_UD_CHAIN);
   df_compute_regs_ever_live (true);
@@ -824,7 +822,7 @@ execute_tag_collision_avoidance ()
   calculate_dominance_info (CDI_DOMINATORS);
   loop_optimizer_init (AVOID_CFG_MODIFICATIONS);
 
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       tag_map_t tag_map (512);
 
diff --git a/gcc/config/mn10300/mn10300.c b/gcc/config/mn10300/mn10300.c
index 6f842a3..aeb5d04 100644
--- a/gcc/config/mn10300/mn10300.c
+++ b/gcc/config/mn10300/mn10300.c
@@ -3234,8 +3234,6 @@ mn10300_loop_contains_call_insn (loop_p loop)
 static void
 mn10300_scan_for_setlb_lcc (void)
 {
-  loop_p loop;
-
   DUMP ("Looking for loops that can use the SETLB insn", NULL_RTX);
 
   df_analyze ();
@@ -3248,7 +3246,7 @@ mn10300_scan_for_setlb_lcc (void)
      if an inner loop is not suitable for use with the SETLB/Lcc insns, it may
      be the case that its parent loop is suitable.  Thus we should check all
      loops, but work from the innermost outwards.  */
-  FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_ONLY_INNERMOST))
     {
       const char * reason = NULL;
 
diff --git a/gcc/config/s390/s390.c b/gcc/config/s390/s390.c
index b1d3b99..8c7d366 100644
--- a/gcc/config/s390/s390.c
+++ b/gcc/config/s390/s390.c
@@ -14479,15 +14479,13 @@ s390_adjust_loop_scan_osc (struct loop* loop)
 static void
 s390_adjust_loops ()
 {
-  struct loop *loop = NULL;
-
   df_analyze ();
   compute_bb_for_insn ();
 
   /* Find the loops.  */
   loop_optimizer_init (AVOID_CFG_MODIFICATIONS);
 
-  FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_ONLY_INNERMOST))
     {
       if (dump_file)
 	{
diff --git a/gcc/doc/loop.texi b/gcc/doc/loop.texi
index a135656..94eed67 100644
--- a/gcc/doc/loop.texi
+++ b/gcc/doc/loop.texi
@@ -79,14 +79,15 @@ and its subloops in the numbering.  The index of a loop never changes.
 
 The entries of the @code{larray} field should not be accessed directly.
 The function @code{get_loop} returns the loop description for a loop with
-the given index.  @code{number_of_loops} function returns number of
-loops in the function.  To traverse all loops, use @code{FOR_EACH_LOOP}
-macro.  The @code{flags} argument of the macro is used to determine
-the direction of traversal and the set of loops visited.  Each loop is
+the given index.  @code{number_of_loops} function returns number of loops
+in the function.  To traverse all loops, use a range-based for loop with
+class @code{loops_list} instance. The @code{flags} argument passed to the
+constructor function of class @code{loops_list} is used to determine the
+direction of traversal and the set of loops visited.  Each loop is
 guaranteed to be visited exactly once, regardless of the changes to the
 loop tree, and the loops may be removed during the traversal.  The newly
-created loops are never traversed, if they need to be visited, this
-must be done separately after their creation.
+created loops are never traversed, if they need to be visited, this must
+be done separately after their creation.
 
 Each basic block contains the reference to the innermost loop it belongs
 to (@code{loop_father}).  For this reason, it is only possible to have
diff --git a/gcc/gimple-loop-interchange.cc b/gcc/gimple-loop-interchange.cc
index 7a88faa..ccd5083 100644
--- a/gcc/gimple-loop-interchange.cc
+++ b/gcc/gimple-loop-interchange.cc
@@ -2089,8 +2089,7 @@ pass_linterchange::execute (function *fun)
     return 0;
 
   bool changed_p = false;
-  class loop *loop;
-  FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_ONLY_INNERMOST))
     {
       vec<loop_p> loop_nest = vNULL;
       vec<data_reference_p> datarefs = vNULL;
diff --git a/gcc/gimple-loop-jam.c b/gcc/gimple-loop-jam.c
index 544ad77..d212e39 100644
--- a/gcc/gimple-loop-jam.c
+++ b/gcc/gimple-loop-jam.c
@@ -487,13 +487,12 @@ adjust_unroll_factor (class loop *inner, struct data_dependence_relation *ddr,
 static unsigned int
 tree_loop_unroll_and_jam (void)
 {
-  class loop *loop;
   unsigned int todo = 0;
 
   gcc_assert (scev_initialized_p ());
 
   /* Go through all innermost loops.  */
-  FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_ONLY_INNERMOST))
     {
       class loop *outer = loop_outer (loop);
 
diff --git a/gcc/gimple-loop-versioning.cc b/gcc/gimple-loop-versioning.cc
index 4b70c5a..114a22f 100644
--- a/gcc/gimple-loop-versioning.cc
+++ b/gcc/gimple-loop-versioning.cc
@@ -1428,8 +1428,7 @@ loop_versioning::analyze_blocks ()
      versioning at that level could be useful in some cases.  */
   get_loop_info (get_loop (m_fn, 0)).rejected_p = true;
 
-  class loop *loop;
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       loop_info &linfo = get_loop_info (loop);
 
@@ -1650,8 +1649,7 @@ loop_versioning::make_versioning_decisions ()
   AUTO_DUMP_SCOPE ("make_versioning_decisions",
 		   dump_user_location_t::from_function_decl (m_fn->decl));
 
-  class loop *loop;
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       loop_info &linfo = get_loop_info (loop);
       if (decide_whether_loop_is_versionable (loop))
diff --git a/gcc/gimple-ssa-split-paths.c b/gcc/gimple-ssa-split-paths.c
index 2dd953d..04ad9c0 100644
--- a/gcc/gimple-ssa-split-paths.c
+++ b/gcc/gimple-ssa-split-paths.c
@@ -473,13 +473,12 @@ static bool
 split_paths ()
 {
   bool changed = false;
-  loop_p loop;
 
   loop_optimizer_init (LOOPS_NORMAL | LOOPS_HAVE_RECORDED_EXITS);
   initialize_original_copy_tables ();
   calculate_dominance_info (CDI_DOMINATORS);
 
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       /* Only split paths if we are optimizing this loop for speed.  */
       if (!optimize_loop_for_speed_p (loop))
diff --git a/gcc/graphite-isl-ast-to-gimple.c b/gcc/graphite-isl-ast-to-gimple.c
index c202213..1ad68a1 100644
--- a/gcc/graphite-isl-ast-to-gimple.c
+++ b/gcc/graphite-isl-ast-to-gimple.c
@@ -1535,9 +1535,8 @@ graphite_regenerate_ast_isl (scop_p scop)
       if_region->false_region->region.entry->flags |= EDGE_FALLTHRU;
       /* remove_edge_and_dominated_blocks marks loops for removal but
 	 doesn't actually remove them (fix that...).  */
-      loop_p loop;
-      FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
-	if (! loop->header)
+      for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
+	if (!loop->header)
 	  delete_loop (loop);
     }
 
diff --git a/gcc/graphite.c b/gcc/graphite.c
index 6c4fb42..0060cae 100644
--- a/gcc/graphite.c
+++ b/gcc/graphite.c
@@ -377,8 +377,7 @@ canonicalize_loop_closed_ssa (loop_p loop, edge e)
 static void
 canonicalize_loop_form (void)
 {
-  loop_p loop;
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       edge e = single_exit (loop);
       if (!e || (e->flags & (EDGE_COMPLEX|EDGE_FAKE)))
@@ -494,10 +493,9 @@ graphite_transform_loops (void)
 
   if (dump_file && (dump_flags & TDF_DETAILS))
     {
-      loop_p loop;
       int num_no_dependency = 0;
 
-      FOR_EACH_LOOP (loop, 0)
+      for (auto loop : loops_list (cfun, 0))
 	if (loop->can_be_parallel)
 	  num_no_dependency++;
 
diff --git a/gcc/ipa-fnsummary.c b/gcc/ipa-fnsummary.c
index cf80ce3..2470937 100644
--- a/gcc/ipa-fnsummary.c
+++ b/gcc/ipa-fnsummary.c
@@ -2923,7 +2923,7 @@ analyze_function_body (struct cgraph_node *node, bool early)
       if (dump_file && (dump_flags & TDF_DETAILS))
 	flow_loops_dump (dump_file, NULL, 0);
       scev_initialize ();
-      FOR_EACH_LOOP (loop, 0)
+      for (auto loop : loops_list (cfun, 0))
 	{
 	  predicate loop_iterations = true;
 	  sreal header_freq;
diff --git a/gcc/ipa-pure-const.c b/gcc/ipa-pure-const.c
index f045108..a84a4eb7 100644
--- a/gcc/ipa-pure-const.c
+++ b/gcc/ipa-pure-const.c
@@ -1087,9 +1087,8 @@ end:
 	    }
 	  else
 	    {
-	      class loop *loop;
 	      scev_initialize ();
-	      FOR_EACH_LOOP (loop, 0)
+	      for (auto loop : loops_list (cfun, 0))
 		if (!finite_loop_p (loop))
 		  {
 		    if (dump_file)
diff --git a/gcc/loop-doloop.c b/gcc/loop-doloop.c
index dda7b9e..c3a4523 100644
--- a/gcc/loop-doloop.c
+++ b/gcc/loop-doloop.c
@@ -789,18 +789,14 @@ doloop_optimize (class loop *loop)
 void
 doloop_optimize_loops (void)
 {
-  class loop *loop;
-
   if (optimize == 1)
     {
       df_live_add_problem ();
       df_live_set_all_dirty ();
     }
 
-  FOR_EACH_LOOP (loop, 0)
-    {
-      doloop_optimize (loop);
-    }
+  for (auto loop : loops_list (cfun, 0))
+    doloop_optimize (loop);
 
   if (optimize == 1)
     df_remove_problem (df_live);
diff --git a/gcc/loop-init.c b/gcc/loop-init.c
index 1fde0ed..04054ef 100644
--- a/gcc/loop-init.c
+++ b/gcc/loop-init.c
@@ -137,7 +137,6 @@ loop_optimizer_init (unsigned flags)
 void
 loop_optimizer_finalize (struct function *fn, bool clean_loop_closed_phi)
 {
-  class loop *loop;
   basic_block bb;
 
   timevar_push (TV_LOOP_FINI);
@@ -167,7 +166,7 @@ loop_optimizer_finalize (struct function *fn, bool clean_loop_closed_phi)
       goto loop_fini_done;
     }
 
-  FOR_EACH_LOOP_FN (fn, loop, 0)
+  for (auto loop : loops_list (fn, 0))
     free_simple_loop_desc (loop);
 
   /* Clean up.  */
@@ -229,7 +228,7 @@ fix_loop_structure (bitmap changed_bbs)
      loops, so that when we remove the loops, we know that the loops inside
      are preserved, and do not waste time relinking loops that will be
      removed later.  */
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       /* Detect the case that the loop is no longer present even though
          it wasn't marked for removal.
diff --git a/gcc/loop-invariant.c b/gcc/loop-invariant.c
index bdc7b59..fca0c2b 100644
--- a/gcc/loop-invariant.c
+++ b/gcc/loop-invariant.c
@@ -2136,7 +2136,7 @@ calculate_loop_reg_pressure (void)
   rtx link;
   class loop *loop, *parent;
 
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     if (loop->aux == NULL)
       {
 	loop->aux = xcalloc (1, sizeof (class loop_data));
@@ -2203,7 +2203,7 @@ calculate_loop_reg_pressure (void)
   bitmap_release (&curr_regs_live);
   if (flag_ira_region == IRA_REGION_MIXED
       || flag_ira_region == IRA_REGION_ALL)
-    FOR_EACH_LOOP (loop, 0)
+    for (auto loop : loops_list (cfun, 0))
       {
 	EXECUTE_IF_SET_IN_BITMAP (&LOOP_DATA (loop)->regs_live, 0, j, bi)
 	  if (! bitmap_bit_p (&LOOP_DATA (loop)->regs_ref, j))
@@ -2217,7 +2217,7 @@ calculate_loop_reg_pressure (void)
       }
   if (dump_file == NULL)
     return;
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     {
       parent = loop_outer (loop);
       fprintf (dump_file, "\n  Loop %d (parent %d, header bb%d, depth %d)\n",
@@ -2251,8 +2251,6 @@ calculate_loop_reg_pressure (void)
 void
 move_loop_invariants (void)
 {
-  class loop *loop;
-
   if (optimize == 1)
     df_live_add_problem ();
   /* ??? This is a hack.  We should only need to call df_live_set_all_dirty
@@ -2271,7 +2269,7 @@ move_loop_invariants (void)
     }
   df_set_flags (DF_EQ_NOTES + DF_DEFER_INSN_RESCAN);
   /* Process the loops, innermost first.  */
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       curr_loop = loop;
       /* move_single_loop_invariants for very large loops is time consuming
@@ -2284,10 +2282,8 @@ move_loop_invariants (void)
 	move_single_loop_invariants (loop);
     }
 
-  FOR_EACH_LOOP (loop, 0)
-    {
+  for (auto loop : loops_list (cfun, 0))
       free_loop_data (loop);
-    }
 
   if (flag_ira_loop_pressure)
     /* There is no sense to keep this info because it was most
diff --git a/gcc/loop-unroll.c b/gcc/loop-unroll.c
index 66d9348..2b31faf 100644
--- a/gcc/loop-unroll.c
+++ b/gcc/loop-unroll.c
@@ -214,10 +214,8 @@ report_unroll (class loop *loop, dump_location_t locus)
 static void
 decide_unrolling (int flags)
 {
-  class loop *loop;
-
   /* Scan the loops, inner ones first.  */
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       loop->lpt_decision.decision = LPT_NONE;
       dump_user_location_t locus = get_loop_location (loop);
@@ -278,14 +276,13 @@ decide_unrolling (int flags)
 void
 unroll_loops (int flags)
 {
-  class loop *loop;
   bool changed = false;
 
   /* Now decide rest of unrolling.  */
   decide_unrolling (flags);
 
   /* Scan the loops, inner ones first.  */
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       /* And perform the appropriate transformations.  */
       switch (loop->lpt_decision.decision)
diff --git a/gcc/modulo-sched.c b/gcc/modulo-sched.c
index e72e46d..1c1b459 100644
--- a/gcc/modulo-sched.c
+++ b/gcc/modulo-sched.c
@@ -1353,7 +1353,6 @@ sms_schedule (void)
   int maxii, max_asap;
   partial_schedule_ptr ps;
   basic_block bb = NULL;
-  class loop *loop;
   basic_block condition_bb = NULL;
   edge latch_edge;
   HOST_WIDE_INT trip_count, max_trip_count;
@@ -1397,7 +1396,7 @@ sms_schedule (void)
 
   /* Build DDGs for all the relevant loops and hold them in G_ARR
      indexed by the loop index.  */
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     {
       rtx_insn *head, *tail;
       rtx count_reg;
@@ -1543,7 +1542,7 @@ sms_schedule (void)
   }
 
   /* We don't want to perform SMS on new loops - created by versioning.  */
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     {
       rtx_insn *head, *tail;
       rtx count_reg;
diff --git a/gcc/predict.c b/gcc/predict.c
index d751e6c..d9c7249 100644
--- a/gcc/predict.c
+++ b/gcc/predict.c
@@ -1949,7 +1949,7 @@ predict_loops (void)
 
   /* Try to predict out blocks in a loop that are not part of a
      natural loop.  */
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       basic_block bb, *bbs;
       unsigned j, n_exits = 0;
@@ -4111,8 +4111,7 @@ pass_profile::execute (function *fun)
     profile_status_for_fn (fun) = PROFILE_GUESSED;
  if (dump_file && (dump_flags & TDF_DETAILS))
    {
-     class loop *loop;
-     FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+     for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
        if (loop->header->count.initialized_p ())
          fprintf (dump_file, "Loop got predicted %d to iterate %i times.\n",
        	   loop->num,
diff --git a/gcc/profile.c b/gcc/profile.c
index 1fa4196..c33c833 100644
--- a/gcc/profile.c
+++ b/gcc/profile.c
@@ -1466,13 +1466,12 @@ branch_prob (bool thunk)
   if (flag_branch_probabilities
       && (profile_status_for_fn (cfun) == PROFILE_READ))
     {
-      class loop *loop;
       if (dump_file && (dump_flags & TDF_DETAILS))
 	report_predictor_hitrates ();
 
       /* At this moment we have precise loop iteration count estimates.
 	 Record them to loop structure before the profile gets out of date. */
-      FOR_EACH_LOOP (loop, 0)
+      for (auto loop : loops_list (cfun, 0))
 	if (loop->header->count > 0 && loop->header->count.reliable_p ())
 	  {
 	    gcov_type nit = expected_loop_iterations_unbounded (loop);
diff --git a/gcc/sel-sched-ir.c b/gcc/sel-sched-ir.c
index eef9d69..48965bf 100644
--- a/gcc/sel-sched-ir.c
+++ b/gcc/sel-sched-ir.c
@@ -6247,10 +6247,8 @@ make_regions_from_the_rest (void)
 /* Free data structures used in pipelining of loops.  */
 void sel_finish_pipelining (void)
 {
-  class loop *loop;
-
   /* Release aux fields so we don't free them later by mistake.  */
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     loop->aux = NULL;
 
   loop_optimizer_finalize ();
@@ -6271,11 +6269,11 @@ sel_find_rgns (void)
 
   if (current_loops)
     {
-      loop_p loop;
+      unsigned flags = flag_sel_sched_pipelining_outer_loops
+			 ? LI_FROM_INNERMOST
+			 : LI_ONLY_INNERMOST;
 
-      FOR_EACH_LOOP (loop, (flag_sel_sched_pipelining_outer_loops
-			    ? LI_FROM_INNERMOST
-			    : LI_ONLY_INNERMOST))
+      for (auto loop : loops_list (cfun, flags))
 	make_regions_from_loop_nest (loop);
     }
 
diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index c8b0f7b..48ee8c0 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -312,12 +312,11 @@ replace_loop_annotate_in_block (basic_block bb, class loop *loop)
 static void
 replace_loop_annotate (void)
 {
-  class loop *loop;
   basic_block bb;
   gimple_stmt_iterator gsi;
   gimple *stmt;
 
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     {
       /* First look into the header.  */
       replace_loop_annotate_in_block (loop->header, loop);
@@ -2027,12 +2026,8 @@ replace_uses_by (tree name, tree val)
   /* Also update the trees stored in loop structures.  */
   if (current_loops)
     {
-      class loop *loop;
-
-      FOR_EACH_LOOP (loop, 0)
-	{
+      for (auto loop : loops_list (cfun, 0))
 	  substitute_in_loop_info (loop, name, val);
-	}
     }
 }
 
@@ -7752,9 +7747,9 @@ move_sese_region_to_fn (struct function *dest_cfun, basic_block entry_bb,
 
   /* Fix up orig_loop_num.  If the block referenced in it has been moved
      to dest_cfun, update orig_loop_num field, otherwise clear it.  */
-  class loop *dloop;
+  class loop *dloop = NULL;
   signed char *moved_orig_loop_num = NULL;
-  FOR_EACH_LOOP_FN (dest_cfun, dloop, 0)
+  for (class loop *dloop : loops_list (dest_cfun, 0))
     if (dloop->orig_loop_num)
       {
 	if (moved_orig_loop_num == NULL)
diff --git a/gcc/tree-if-conv.c b/gcc/tree-if-conv.c
index 49e89cf..d7b7b30 100644
--- a/gcc/tree-if-conv.c
+++ b/gcc/tree-if-conv.c
@@ -3300,14 +3300,13 @@ pass_if_conversion::gate (function *fun)
 unsigned int
 pass_if_conversion::execute (function *fun)
 {
-  class loop *loop;
   unsigned todo = 0;
 
   if (number_of_loops (fun) <= 1)
     return 0;
 
   auto_vec<gimple *> preds;
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     if (flag_tree_loop_if_convert == 1
 	|| ((flag_tree_loop_vectorize || loop->force_vectorize)
 	    && !loop->dont_vectorize))
diff --git a/gcc/tree-loop-distribution.c b/gcc/tree-loop-distribution.c
index a984d21..2df762c 100644
--- a/gcc/tree-loop-distribution.c
+++ b/gcc/tree-loop-distribution.c
@@ -3315,7 +3315,7 @@ loop_distribution::execute (function *fun)
 
   /* We can at the moment only distribute non-nested loops, thus restrict
      walking to innermost loops.  */
-  FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_ONLY_INNERMOST))
     {
       /* Don't distribute multiple exit edges loop, or cold loop when
          not doing pattern detection.  */
diff --git a/gcc/tree-parloops.c b/gcc/tree-parloops.c
index 4d40c96..5e64d5e 100644
--- a/gcc/tree-parloops.c
+++ b/gcc/tree-parloops.c
@@ -3990,7 +3990,6 @@ parallelize_loops (bool oacc_kernels_p)
 {
   unsigned n_threads;
   bool changed = false;
-  class loop *loop;
   class loop *skip_loop = NULL;
   class tree_niter_desc niter_desc;
   struct obstack parloop_obstack;
@@ -4021,7 +4020,7 @@ parallelize_loops (bool oacc_kernels_p)
 
   calculate_dominance_info (CDI_DOMINATORS);
 
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     {
       if (loop == skip_loop)
 	{
diff --git a/gcc/tree-predcom.c b/gcc/tree-predcom.c
index cf85517..bed30d2 100644
--- a/gcc/tree-predcom.c
+++ b/gcc/tree-predcom.c
@@ -3419,11 +3419,10 @@ pcom_worker::tree_predictive_commoning_loop (bool allow_unroll_p)
 unsigned
 tree_predictive_commoning (bool allow_unroll_p)
 {
-  class loop *loop;
   unsigned ret = 0, changed = 0;
 
   initialize_original_copy_tables ();
-  FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_ONLY_INNERMOST))
     if (optimize_loop_for_speed_p (loop))
       {
 	pcom_worker w(loop);
diff --git a/gcc/tree-scalar-evolution.c b/gcc/tree-scalar-evolution.c
index b22d49a..dbdfe8f 100644
--- a/gcc/tree-scalar-evolution.c
+++ b/gcc/tree-scalar-evolution.c
@@ -2977,16 +2977,12 @@ gather_stats_on_scev_database (void)
 void
 scev_initialize (void)
 {
-  class loop *loop;
-
   gcc_assert (! scev_initialized_p ());
 
   scalar_evolution_info = hash_table<scev_info_hasher>::create_ggc (100);
 
-  FOR_EACH_LOOP (loop, 0)
-    {
-      loop->nb_iterations = NULL_TREE;
-    }
+  for (auto loop : loops_list (cfun, 0))
+    loop->nb_iterations = NULL_TREE;
 }
 
 /* Return true if SCEV is initialized.  */
@@ -3015,14 +3011,10 @@ scev_reset_htab (void)
 void
 scev_reset (void)
 {
-  class loop *loop;
-
   scev_reset_htab ();
 
-  FOR_EACH_LOOP (loop, 0)
-    {
-      loop->nb_iterations = NULL_TREE;
-    }
+  for (auto loop : loops_list (cfun, 0))
+    loop->nb_iterations = NULL_TREE;
 }
 
 /* Return true if the IV calculation in TYPE can overflow based on the knowledge
diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index e2d3b63..0778eb9 100644
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -417,7 +417,6 @@ find_obviously_necessary_stmts (bool aggressive)
   /* Prevent the empty possibly infinite loops from being removed.  */
   if (aggressive)
     {
-      class loop *loop;
       if (mark_irreducible_loops ())
 	FOR_EACH_BB_FN (bb, cfun)
 	  {
@@ -433,7 +432,7 @@ find_obviously_necessary_stmts (bool aggressive)
 		}
 	  }
 
-      FOR_EACH_LOOP (loop, 0)
+      for (auto loop : loops_list (cfun, 0))
 	if (!finite_loop_p (loop))
 	  {
 	    if (dump_file)
diff --git a/gcc/tree-ssa-live.c b/gcc/tree-ssa-live.c
index a2aab25..3d5fa8d 100644
--- a/gcc/tree-ssa-live.c
+++ b/gcc/tree-ssa-live.c
@@ -908,8 +908,7 @@ remove_unused_locals (void)
 
   if (cfun->has_simduid_loops)
     {
-      class loop *loop;
-      FOR_EACH_LOOP (loop, 0)
+      for (auto loop : loops_list (cfun, 0))
 	if (loop->simduid && !is_used_p (loop->simduid))
 	  loop->simduid = NULL_TREE;
     }
diff --git a/gcc/tree-ssa-loop-ch.c b/gcc/tree-ssa-loop-ch.c
index dfa5dc8..b4e09f9 100644
--- a/gcc/tree-ssa-loop-ch.c
+++ b/gcc/tree-ssa-loop-ch.c
@@ -348,7 +348,6 @@ protected:
 unsigned int
 ch_base::copy_headers (function *fun)
 {
-  class loop *loop;
   basic_block header;
   edge exit, entry;
   basic_block *bbs, *copied_bbs;
@@ -365,7 +364,7 @@ ch_base::copy_headers (function *fun)
 
   auto_vec<std::pair<edge, loop_p> > copied;
 
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     {
       int initial_limit = param_max_loop_header_insns;
       int remaining_limit = initial_limit;
diff --git a/gcc/tree-ssa-loop-im.c b/gcc/tree-ssa-loop-im.c
index dfb3984..d9f75d5 100644
--- a/gcc/tree-ssa-loop-im.c
+++ b/gcc/tree-ssa-loop-im.c
@@ -1662,7 +1662,7 @@ analyze_memory_references (bool store_motion)
 {
   gimple_stmt_iterator bsi;
   basic_block bb, *bbs;
-  class loop *loop, *outer;
+  class loop *outer;
   unsigned i, n;
 
   /* Collect all basic-blocks in loops and sort them after their
@@ -1706,7 +1706,7 @@ analyze_memory_references (bool store_motion)
 
   /* Propagate the information about accessed memory references up
      the loop hierarchy.  */
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       /* Finalize the overall touched references (including subloops).  */
       bitmap_ior_into (&memory_accesses.all_refs_stored_in_loop[loop->num],
@@ -3133,7 +3133,6 @@ fill_always_executed_in (void)
 static void
 tree_ssa_lim_initialize (bool store_motion)
 {
-  class loop *loop;
   unsigned i;
 
   bitmap_obstack_initialize (&lim_bitmap_obstack);
@@ -3177,7 +3176,7 @@ tree_ssa_lim_initialize (bool store_motion)
      its postorder index.  */
   i = 0;
   bb_loop_postorder = XNEWVEC (unsigned, number_of_loops (cfun));
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     bb_loop_postorder[loop->num] = i++;
 }
 
diff --git a/gcc/tree-ssa-loop-ivcanon.c b/gcc/tree-ssa-loop-ivcanon.c
index b1971f8..8d8791f 100644
--- a/gcc/tree-ssa-loop-ivcanon.c
+++ b/gcc/tree-ssa-loop-ivcanon.c
@@ -1285,14 +1285,13 @@ canonicalize_loop_induction_variables (class loop *loop,
 unsigned int
 canonicalize_induction_variables (void)
 {
-  class loop *loop;
   bool changed = false;
   bool irred_invalidated = false;
   bitmap loop_closed_ssa_invalidated = BITMAP_ALLOC (NULL);
 
   estimate_numbers_of_iterations (cfun);
 
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       changed |= canonicalize_loop_induction_variables (loop,
 							true, UL_SINGLE_ITER,
diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c
index 47b867f..4a498ab 100644
--- a/gcc/tree-ssa-loop-ivopts.c
+++ b/gcc/tree-ssa-loop-ivopts.c
@@ -8131,14 +8131,13 @@ finish:
 void
 tree_ssa_iv_optimize (void)
 {
-  class loop *loop;
   struct ivopts_data data;
   auto_bitmap toremove;
 
   tree_ssa_iv_optimize_init (&data);
 
   /* Optimize the loops starting with the innermost ones.  */
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       if (!dbg_cnt (ivopts_loop))
 	continue;
diff --git a/gcc/tree-ssa-loop-manip.c b/gcc/tree-ssa-loop-manip.c
index 41f9872..c7a2f67 100644
--- a/gcc/tree-ssa-loop-manip.c
+++ b/gcc/tree-ssa-loop-manip.c
@@ -362,11 +362,10 @@ add_exit_phis (bitmap names_to_rename, bitmap *use_blocks, bitmap *loop_exits)
 static void
 get_loops_exits (bitmap *loop_exits)
 {
-  class loop *loop;
   unsigned j;
   edge e;
 
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     {
       auto_vec<edge> exit_edges = get_loop_exit_edges (loop);
       loop_exits[loop->num] = BITMAP_ALLOC (&loop_renamer_obstack);
diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
index 1b5605c..466158a 100644
--- a/gcc/tree-ssa-loop-niter.c
+++ b/gcc/tree-ssa-loop-niter.c
@@ -4559,13 +4559,11 @@ estimated_stmt_executions (class loop *loop, widest_int *nit)
 void
 estimate_numbers_of_iterations (function *fn)
 {
-  class loop *loop;
-
   /* We don't want to issue signed overflow warnings while getting
      loop iteration estimates.  */
   fold_defer_overflow_warnings ();
 
-  FOR_EACH_LOOP_FN (fn, loop, 0)
+  for (auto loop : loops_list (fn, 0))
     estimate_numbers_of_iterations (loop);
 
   fold_undefer_and_ignore_overflow_warnings ();
@@ -5031,9 +5029,7 @@ free_numbers_of_iterations_estimates (class loop *loop)
 void
 free_numbers_of_iterations_estimates (function *fn)
 {
-  class loop *loop;
-
-  FOR_EACH_LOOP_FN (fn, loop, 0)
+  for (auto loop : loops_list (fn, 0))
     free_numbers_of_iterations_estimates (loop);
 }
 
diff --git a/gcc/tree-ssa-loop-prefetch.c b/gcc/tree-ssa-loop-prefetch.c
index 98062eb..85977e2 100644
--- a/gcc/tree-ssa-loop-prefetch.c
+++ b/gcc/tree-ssa-loop-prefetch.c
@@ -1980,7 +1980,6 @@ fail:
 unsigned int
 tree_ssa_prefetch_arrays (void)
 {
-  class loop *loop;
   bool unrolled = false;
   int todo_flags = 0;
 
@@ -2025,7 +2024,7 @@ tree_ssa_prefetch_arrays (void)
       set_builtin_decl (BUILT_IN_PREFETCH, decl, false);
     }
 
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       if (dump_file && (dump_flags & TDF_DETAILS))
 	fprintf (dump_file, "Processing loop %d:\n", loop->num);
diff --git a/gcc/tree-ssa-loop-split.c b/gcc/tree-ssa-loop-split.c
index 3a09bbc..3f6ad04 100644
--- a/gcc/tree-ssa-loop-split.c
+++ b/gcc/tree-ssa-loop-split.c
@@ -1598,18 +1598,17 @@ split_loop_on_cond (struct loop *loop)
 static unsigned int
 tree_ssa_split_loops (void)
 {
-  class loop *loop;
   bool changed = false;
 
   gcc_assert (scev_initialized_p ());
 
   calculate_dominance_info (CDI_POST_DOMINATORS);
 
-  FOR_EACH_LOOP (loop, LI_INCLUDE_ROOT)
+  for (auto loop : loops_list (cfun, LI_INCLUDE_ROOT))
     loop->aux = NULL;
 
   /* Go through all loops starting from innermost.  */
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       if (loop->aux)
 	{
@@ -1630,7 +1629,7 @@ tree_ssa_split_loops (void)
 	}
     }
 
-  FOR_EACH_LOOP (loop, LI_INCLUDE_ROOT)
+  for (auto loop : loops_list (cfun, LI_INCLUDE_ROOT))
     loop->aux = NULL;
 
   clear_aux_for_blocks ();
diff --git a/gcc/tree-ssa-loop-unswitch.c b/gcc/tree-ssa-loop-unswitch.c
index 04d4553..fe4dacc 100644
--- a/gcc/tree-ssa-loop-unswitch.c
+++ b/gcc/tree-ssa-loop-unswitch.c
@@ -90,11 +90,10 @@ static tree get_vop_from_header (class loop *);
 unsigned int
 tree_ssa_unswitch_loops (void)
 {
-  class loop *loop;
   bool changed = false;
 
   /* Go through all loops starting from innermost.  */
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       if (!loop->inner)
 	/* Unswitch innermost loop.  */
diff --git a/gcc/tree-ssa-loop.c b/gcc/tree-ssa-loop.c
index 957ac0f..0cc4b3b 100644
--- a/gcc/tree-ssa-loop.c
+++ b/gcc/tree-ssa-loop.c
@@ -157,8 +157,7 @@ gate_oacc_kernels (function *fn)
   if (!lookup_attribute ("oacc kernels", DECL_ATTRIBUTES (fn->decl)))
     return false;
 
-  class loop *loop;
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     if (loop->in_oacc_kernels_region)
       return true;
 
@@ -455,12 +454,11 @@ public:
 unsigned
 pass_scev_cprop::execute (function *)
 {
-  class loop *loop;
   bool any = false;
 
   /* Perform final value replacement in loops, in case the replacement
      expressions are cheap.  */
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     any |= final_value_replacement_loop (loop);
 
   return any ? TODO_cleanup_cfg | TODO_update_ssa_only_virtuals : 0;
diff --git a/gcc/tree-ssa-propagate.c b/gcc/tree-ssa-propagate.c
index d93ec90..6d19410 100644
--- a/gcc/tree-ssa-propagate.c
+++ b/gcc/tree-ssa-propagate.c
@@ -1262,7 +1262,6 @@ clean_up_loop_closed_phi (function *fun)
   tree rhs;
   tree lhs;
   gphi_iterator gsi;
-  struct loop *loop;
 
   /* Avoid possibly quadratic work when scanning for loop exits across
    all loops of a nest.  */
@@ -1274,7 +1273,7 @@ clean_up_loop_closed_phi (function *fun)
   calculate_dominance_info  (CDI_DOMINATORS);
 
   /* Walk over loop in function.  */
-  FOR_EACH_LOOP_FN (fun, loop, 0)
+  for (auto loop : loops_list (fun, 0))
     {
       /* Check each exit edege of loop.  */
       auto_vec<edge> exits = get_loop_exit_edges (loop);
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index f6f900c..01fffcd 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -7651,9 +7651,8 @@ do_rpo_vn (function *fn, edge entry, bitmap exit_bbs,
      loops and the outermost one optimistically.  */
   if (iterate)
     {
-      loop_p loop;
       unsigned max_depth = param_rpo_vn_max_loop_depth;
-      FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
+      for (auto loop : loops_list (cfun, LI_ONLY_INNERMOST))
 	if (loop_depth (loop) > max_depth)
 	  for (unsigned i = 2;
 	       i < loop_depth (loop) - max_depth; ++i)
diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c
index 29cf010..d08e7d3 100644
--- a/gcc/tree-ssa-threadupdate.c
+++ b/gcc/tree-ssa-threadupdate.c
@@ -2562,7 +2562,6 @@ jump_thread_path_registry::thread_through_all_blocks
 {
   bool retval = false;
   unsigned int i;
-  class loop *loop;
   auto_bitmap threaded_blocks;
   hash_set<edge> visited_starting_edges;
 
@@ -2703,7 +2702,7 @@ jump_thread_path_registry::thread_through_all_blocks
   /* Then perform the threading through loop headers.  We start with the
      innermost loop, so that the changes in cfg we perform won't affect
      further threading.  */
-  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
+  for (auto loop : loops_list (cfun, LI_FROM_INNERMOST))
     {
       if (!loop->header
 	  || !bitmap_bit_p (threaded_blocks, loop->header->index))
diff --git a/gcc/tree-vectorizer.c b/gcc/tree-vectorizer.c
index f1035a8..b9709a6 100644
--- a/gcc/tree-vectorizer.c
+++ b/gcc/tree-vectorizer.c
@@ -1194,7 +1194,7 @@ vectorize_loops (void)
   /* If some loop was duplicated, it gets bigger number
      than all previously defined loops.  This fact allows us to run
      only over initial loops skipping newly generated ones.  */
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     if (loop->dont_vectorize)
       {
 	any_ifcvt_loops = true;
@@ -1213,7 +1213,7 @@ vectorize_loops (void)
 		  loop4 (copy of loop2)
 		else
 		  loop5 (copy of loop4)
-	   If FOR_EACH_LOOP gives us loop3 first (which has
+	   If loops' iteration gives us loop3 first (which has
 	   dont_vectorize set), make sure to process loop1 before loop4;
 	   so that we can prevent vectorization of loop4 if loop1
 	   is successfully vectorized.  */
diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index d1b6910..26e71e7 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -3337,8 +3337,7 @@ vrp_asserts::find_assert_locations (void)
   /* Pre-seed loop latch liveness from loop header PHI nodes.  Due to
      the order we compute liveness and insert asserts we otherwise
      fail to insert asserts into the loop latch.  */
-  loop_p loop;
-  FOR_EACH_LOOP (loop, 0)
+  for (auto loop : loops_list (cfun, 0))
     {
       i = loop->latch->index;
       unsigned int j = single_succ_edge (loop->latch)->dest_idx;