X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=ir%2Fana%2Fircfscc.c;h=b573c1f94d8241f3ec2536a7f4832fcacdd2df79;hb=3ea053779e18f3a0a2fcead621f7d610de8531c1;hp=bc1d7121e152906e64e3044f1f6da588982aece3;hpb=dddcc630819f338c3b45e2bc646233e6872d5bb6;p=libfirm

diff --git a/ir/ana/ircfscc.c b/ir/ana/ircfscc.c
index bc1d7121e..b573c1f94 100644
--- a/ir/ana/ircfscc.c
+++ b/ir/ana/ircfscc.c
@@ -17,7 +17,9 @@
 #include "config.h"
 #endif
 
+#ifdef HAVE_STRING_H
 #include <string.h>
+#endif
 
 #include "irloop_t.h"
 #include "irnode_t.h"
@@ -28,15 +30,19 @@
 #include "irprog_t.h"
 #include "irdump.h"
 
+#define NO_CFLOOPS_WITHOUT_HEAD 1
+
 static ir_graph *outermost_ir_graph;      /* The outermost graph the scc is computed
                       for */
 static ir_loop *current_loop;      /* Current cfloop construction is working
                       on. */
 static int loop_node_cnt = 0;      /* Counts the number of allocated cfloop nodes.
-                      Each cfloop node gets a unique number.
-                      What for? ev. remove. @@@ */
+				      Each cfloop node gets a unique number.
+				      What for? ev. remove. @@@ */
 static int current_dfn = 1;        /* Counter to generate depth first numbering
-                      of visited nodes.  */
+				      of visited nodes.  */
+
+static int max_loop_depth = 0;
 
 void link_to_reg_end (ir_node *n, void *env);
 
@@ -48,88 +54,122 @@ void link_to_reg_end (ir_node *n, void *env);
 /* Node attributes needed for the construction.                      **/
 /**********************************************************************/
 
+/**
+ * The SCC info. Additional fields for an ir-node needed for the
+ * construction.
+ */
 typedef struct scc_info {
-  bool in_stack;         /* Marks whether node is on the stack. */
-  int dfn;               /* Depth first search number. */
-  int uplink;            /* dfn number of ancestor. */
+  int in_stack;          /**< Marks whether node is on the stack. */
+  int dfn;               /**< Depth first search number. */
+  int uplink;            /**< dfn number of ancestor. */
 } scc_info;
 
-static INLINE scc_info* new_scc_info(void) {
+/** Allocate a new scc_info on the obstack of the outermost graph */
+static INLINE scc_info *new_scc_info(void) {
   scc_info *info = obstack_alloc (outermost_ir_graph->obst, sizeof (scc_info));
   memset (info, 0, sizeof (scc_info));
   return info;
 }
 
+/**
+ * Marks the node n to be on the stack.
+ */
 static INLINE void
 mark_irn_in_stack (ir_node *n) {
-  assert(get_irn_link(n));
-  ((scc_info *)n->link)->in_stack = true;
+  scc_info *info = get_irn_link(n);
+  info->in_stack = 1;
 }
 
+/**
+ * Marks the node n to be not on the stack.
+ */
 static INLINE void
 mark_irn_not_in_stack (ir_node *n) {
-  assert(get_irn_link(n));
-  ((scc_info *)n->link)->in_stack = false;
+  scc_info *info = get_irn_link(n);
+  info->in_stack = 0;
 }
 
-static INLINE bool
+/**
+ * Returns whether node n is on the stack.
+ */
+static INLINE int
 irn_is_in_stack (ir_node *n) {
-  assert(get_irn_link(n));
-  return ((scc_info *)n->link)->in_stack;
+  scc_info *info = get_irn_link(n);
+  return info->in_stack;
 }
 
+/**
+ * Sets node n uplink value.
+ */
 static INLINE void
 set_irn_uplink (ir_node *n, int uplink) {
-  assert(get_irn_link(n));
-  ((scc_info *)n->link)->uplink = uplink;
+  scc_info *info = get_irn_link(n);
+  info->uplink = uplink;
 }
 
+/**
+ * Return node n uplink value.
+ */
 static INLINE int
 get_irn_uplink (ir_node *n) {
-  assert(get_irn_link(n));
-  return ((scc_info *)n->link)->uplink;
+  scc_info *info = get_irn_link(n);
+  return info->uplink;
 }
 
+/**
+ * Sets node n dfn value.
+ */
 static INLINE void
 set_irn_dfn (ir_node *n, int dfn) {
-  assert(get_irn_link(n));
-  ((scc_info *)n->link)->dfn = dfn;
+  scc_info *info = get_irn_link(n);
+  info->dfn = dfn;
 }
 
+/**
+ * Returns node n dfn value.
+ */
 static INLINE int
 get_irn_dfn (ir_node *n) {
-  assert(get_irn_link(n));
-  return ((scc_info *)n->link)->dfn;
+  scc_info *info = get_irn_link(n);
+  return info->dfn;
 }
 
 /**********************************************************************/
 /* A stack.                                                          **/
 /**********************************************************************/
 
-static ir_node **stack = NULL;
-static int tos = 0;                /* top of stack */
+static ir_node **stack = NULL;     /**< An IR-node stack */
+static int tos = 0;                /**< The top (index) of the IR-node stack */
 
+/**
+ * Initializes the IR-node stack
+ */
 static INLINE void init_stack(void) {
   if (stack) {
-    ARR_RESIZE (ir_node *, stack, 1000);
+    ARR_RESIZE(ir_node *, stack, 1000);
   } else {
-    stack = NEW_ARR_F (ir_node *, 1000);
+    stack = NEW_ARR_F(ir_node *, 1000);
   }
   tos = 0;
 }
 
-
+/**
+ * Push a node n onto the IR-node stack.
+ */
 static INLINE void
 push (ir_node *n)
 {
-  if (tos == ARR_LEN (stack)) {
-    int nlen = ARR_LEN (stack) * 2;
-    ARR_RESIZE (ir_node *, stack, nlen);
+  if (tos == ARR_LEN(stack)) {
+    int nlen = ARR_LEN(stack) * 2;
+    ARR_RESIZE(ir_node *, stack, nlen);
   }
-  stack [tos++] = n;
+  stack[tos++] = n;
   mark_irn_in_stack(n);
 }
 
+/**
+ * Pop a node from the IR-node stack and return it.
+ */
 static INLINE ir_node *
 pop (void)
 {
@@ -138,10 +178,12 @@ pop (void)
   return n;
 }
 
-/* The nodes up to n belong to the current loop.
-   Removes them from the stack and adds them to the current loop. */
+/**
+ * The nodes from tos up to n belong to the current loop.
+ * Removes them from the stack and adds them to the current loop.
+ */
 static INLINE void
-pop_scc_to_loop (ir_node *n)
+pop_scc_to_loop(ir_node *n)
 {
   ir_node *m;
 
@@ -183,48 +225,54 @@ static void close_loop (ir_loop *l)
   current_loop = l;
 }
 
-/* Removes and unmarks all nodes up to n from the stack.
-   The nodes must be visited once more to assign them to a scc. */
+/**
+ * Removes and unmarks all nodes up to n from the stack.
+ * The nodes must be visited once more to assign them to a scc.
+ */
 static INLINE void
 pop_scc_unmark_visit (ir_node *n)
 {
-  ir_node *m = NULL;
+  ir_node *m;
 
-  while (m != n) {
+  do {
     m = pop();
     set_irn_visited(m, 0);
-  }
+  } while (m != n);
 }
 
 /**********************************************************************/
 /* The loop datastructure.                                           **/
 /**********************************************************************/
 
-/* Allocates a new loop as son of current_loop.  Sets current_loop
-   to the new loop and returns the father. */
+/**
+ * Allocates a new loop as son of current_loop.  Sets current_loop
+ * to the new loop and returns its father.
+ */
 static ir_loop *new_loop (void) {
   ir_loop *father, *son;
 
   father = current_loop;
 
-  son = (ir_loop *) obstack_alloc (outermost_ir_graph->obst, sizeof (ir_loop));
-  memset (son, 0, sizeof (ir_loop));
-  son->kind = k_ir_loop;
-  son->children = NEW_ARR_F (loop_element, 0);
-  son->n_nodes = 0;
-  son->n_sons=0;
+  son = obstack_alloc(outermost_ir_graph->obst, sizeof(*son));
+  memset(son, 0, sizeof(*son));
+  son->kind     = k_ir_loop;
+  son->children = NEW_ARR_F(loop_element, 0);
+  son->n_nodes  = 0;
+  son->n_sons   = 0;
   if (father) {
     son->outer_loop = father;
     add_loop_son(father, son);
     son->depth = father->depth+1;
-  } else {  /* The root loop */
+    if (son->depth > max_loop_depth) max_loop_depth = son->depth;
+  }
+  else {  /* The root loop */
     son->outer_loop = son;
-    son->depth = 0;
+    son->depth      = 0;
   }
 
 #ifdef DEBUG_libfirm
   son->loop_nr = get_irp_new_node_nr();
-  son->link = NULL;
+  son->link    = NULL;
 #endif
 
   current_loop = son;
@@ -237,6 +285,11 @@ static ir_loop *new_loop (void) {
 
 /* Initialization steps. **********************************************/
 
+/**
+ * Allocates a scc_info for every Block node n.
+ * Clear the backedges for all nodes.
+ * Called from a walker.
+ */
 static INLINE void
 init_node (ir_node *n, void *env) {
   if (is_Block(n))
@@ -244,19 +297,29 @@ init_node (ir_node *n, void *env) {
   clear_backedges(n);
 }
 
+/**
+ * Initializes the common global settings for the scc algorithm
+ */
 static INLINE void
 init_scc_common (void) {
-  current_dfn = 1;
+  current_dfn   = 1;
   loop_node_cnt = 0;
   init_stack();
 }
 
+/**
+ * Initializes the scc algorithm for the intraprocedural case.
+ * Add scc info to every block node.
+ */
 static INLINE void
 init_scc (ir_graph *irg) {
   init_scc_common();
-  irg_walk_graph (irg, init_node, NULL, NULL);
+  irg_walk_graph(irg, init_node, NULL, NULL);
 }
 
+/**
+ * Initializes the scc algorithm for the interprocedural case.
+ */
 static INLINE void
 init_ip_scc (void) {
   init_scc_common();
@@ -267,25 +330,29 @@ init_ip_scc (void) {
 #endif
 }
 
-/* Condition for breaking the recursion. */
-static bool is_outermost_StartBlock(ir_node *n) {
+/**
+ * Condition for breaking the recursion: n is the block
+ * that gets the initial control flow from the Start node.
+ */
+static int is_outermost_StartBlock(ir_node *n) {
   /* Test whether this is the outermost Start node.  If so
      recursion must end. */
   assert(is_Block(n));
   if ((get_Block_n_cfgpreds(n) == 1)  &&
       (get_irn_op(skip_Proj(get_Block_cfgpred(n, 0))) == op_Start) &&
       (get_nodes_block(skip_Proj(get_Block_cfgpred(n, 0))) == n)) {
-    return true;
+    return 1;
   }
-  return false;
+  return 0;
 }
 
-/** Returns true if n is a loop header, i.e., it is a Block node
+/** Returns non-zero if n is a loop header, i.e., it is a Block node
  *  and has predecessors within the cfloop and out of the cfloop.
  *
- *  @param root: only needed for assertion.
+ *  @param n     the block node to check
+ *  @param root  only needed for assertion.
  */
-static bool
+static int
 is_head (ir_node *n, ir_node *root)
 {
   int i, arity;
@@ -299,21 +366,60 @@ is_head (ir_node *n, ir_node *root)
       ir_node *pred = get_nodes_block(skip_Proj(get_irn_n(n, i)));
       if (is_backedge(n, i)) continue;
       if (!irn_is_in_stack(pred)) {
-	some_outof_loop = 1;
+        some_outof_loop = 1;
       } else {
-	if (get_irn_uplink(pred) < get_irn_uplink(root))  {
-	  DDMN(pred); DDMN(root);
-	  assert(get_irn_uplink(pred) >= get_irn_uplink(root));
-	}
-	some_in_loop = 1;
+        if (get_irn_uplink(pred) < get_irn_uplink(root))  {
+          DDMN(pred); DDMN(root);
+          assert(get_irn_uplink(pred) >= get_irn_uplink(root));
+        }
+        some_in_loop = 1;
       }
     }
   }
-  return some_outof_loop && some_in_loop;
+  return some_outof_loop & some_in_loop;
 }
 
-/* Returns index of the predecessor with the smallest dfn number
-   greater-equal than limit. */
+
+/**
+ * Returns non-zero if n is possible loop head of an endless loop.
+ * I.e., it is a Block, Phi or Filter node and has only predecessors
+ * within the loop.
+ *
+ * @param n     the block node to check
+ * @param root  only needed for assertion.
+ */
+static int
+is_endless_head (ir_node *n, ir_node *root)
+{
+  int i, arity;
+  int some_outof_loop = 0, some_in_loop = 0;
+
+  assert(is_Block(n));
+  /* Test for legal loop header: Block, Phi, ... */
+  if (!is_outermost_StartBlock(n)) {
+    arity = get_irn_arity(n);
+    for (i = 0; i < arity; i++) {
+      ir_node *pred = get_nodes_block(skip_Proj(get_irn_n(n, i)));
+      assert(pred);
+      if (is_backedge(n, i)) { continue; }
+      if (!irn_is_in_stack(pred)) {
+	      some_outof_loop = 1; //printf(" some out of loop ");
+      } else {
+	      if(get_irn_uplink(pred) < get_irn_uplink(root)) {
+	        DDMN(pred); DDMN(root);
+	        assert(get_irn_uplink(pred) >= get_irn_uplink(root));
+	      }
+	      some_in_loop = 1;
+      }
+    }
+  }
+  return !some_outof_loop && some_in_loop;
+}
+
+/**
+ * Returns index of the predecessor with the smallest dfn number
+ * greater-equal than limit.
+ */
 static int
 smallest_dfn_pred (ir_node *n, int limit)
 {
@@ -323,17 +429,20 @@ smallest_dfn_pred (ir_node *n, int limit)
     int arity = get_irn_arity(n);
     for (i = 0; i < arity; i++) {
       ir_node *pred = get_nodes_block(skip_Proj(get_irn_n(n, i)));
-      if (is_backedge(n, i) || !irn_is_in_stack(pred)) continue;
+      if (is_backedge(n, i) || !irn_is_in_stack(pred))
+        continue;
       if (get_irn_dfn(pred) >= limit && (min == -1 || get_irn_dfn(pred) < min)) {
-	index = i;
-	min = get_irn_dfn(pred);
+	      index = i;
+	      min = get_irn_dfn(pred);
       }
     }
   }
   return index;
 }
 
-/* Returns index of the predecessor with the largest dfn number. */
+/**
+ * Returns index of the predecessor with the largest dfn number.
+ */
 static int
 largest_dfn_pred (ir_node *n)
 {
@@ -343,43 +452,74 @@ largest_dfn_pred (ir_node *n)
     int arity = get_irn_arity(n);
     for (i = 0; i < arity; i++) {
       ir_node *pred = get_nodes_block(skip_Proj(get_irn_n(n, i)));
-      if (is_backedge (n, i) || !irn_is_in_stack(pred)) continue;
+      if (is_backedge (n, i) || !irn_is_in_stack(pred))
+        continue;
       if (get_irn_dfn(pred) > max) {
-	index = i;
-	max = get_irn_dfn(pred);
+	      index = i;
+	      max = get_irn_dfn(pred);
       }
     }
   }
   return index;
 }
 
-/* Searches the stack for possible loop heads.  Tests these for backedges.
-   If it finds a head with an unmarked backedge it marks this edge and
-   returns the tail of the loop.
-   If it finds no backedge returns NULL.
-   ("disable_backedge" in fiasco) */
+/**
+ * Searches the stack for possible loop heads.  Tests these for backedges.
+ * If it finds a head with an unmarked backedge it marks this edge and
+ * returns the tail of the loop.
+ * If it finds no backedge returns NULL.
+ */
 static ir_node *
 find_tail (ir_node *n) {
   ir_node *m;
   int i, res_index = -2;
 
   m = stack[tos-1];  /* tos = top of stack */
-  if (is_head (m, n)) {
+  if (is_head(m, n)) {
     res_index = smallest_dfn_pred(m, 0);
     if ((res_index == -2) &&  /* no smallest dfn pred found. */
-	(n ==  m))
+	      (n ==  m))
       return NULL;
   } else {
     if (m == n) return NULL;
-    for (i = tos-2; ; --i) {
+    for (i = tos-2; i >= 0; --i) {
+
       m = stack[i];
       if (is_head (m, n)) {
-	res_index = smallest_dfn_pred (m, get_irn_dfn(m) + 1);
-	if (res_index == -2)  /* no smallest dfn pred found. */
-	  res_index = largest_dfn_pred (m);
-	break;
+	      res_index = smallest_dfn_pred (m, get_irn_dfn(m) + 1);
+	      if (res_index == -2)  /* no smallest dfn pred found. */
+	        res_index = largest_dfn_pred (m);
+
+	      if ((m == n) && (res_index == -2)) {
+	        i = -1;
+	      }
+	      break;
+      }
+
+
+      /* We should not walk past our selves on the stack:  The upcoming nodes
+	       are not in this loop. We assume a loop not reachable from Start. */
+      if (m == n) {
+	      i = -1;
+	      break;
+      }
+    }
+
+    if (i < 0) {
+      /* A dead loop not reachable from Start. */
+      for (i = tos-2; i >= 0; --i) {
+	      m = stack[i];
+	      if (is_endless_head (m, n)) {
+	        res_index = smallest_dfn_pred (m, get_irn_dfn(m) + 1);
+	        if (res_index == -2)  /* no smallest dfn pred found. */
+	          res_index = largest_dfn_pred (m);
+	        break;
+	      }
+	      if (m == n) break;   /* It's not an unreachable loop, either. */
       }
+      //assert(0 && "no head found on stack");
     }
+
   }
   assert (res_index > -2);
 
@@ -387,11 +527,21 @@ find_tail (ir_node *n) {
   return is_outermost_StartBlock(n) ? NULL : get_nodes_block(skip_Proj(get_irn_n(m, res_index)));
 }
 
+/**
+ * returns non.zero if l is the outermost loop.
+ */
+INLINE static int
+is_outermost_loop(ir_loop *l) {
+  return l == get_loop_outer_loop(l);
+}
+
 /*-----------------------------------------------------------*
  *                   The core algorithm.                     *
  *-----------------------------------------------------------*/
 
-
+/**
+ * Walks over all blocks of a graph
+ */
 static void cfscc (ir_node *n) {
   int i;
 
@@ -404,27 +554,25 @@ static void cfscc (ir_node *n) {
   set_irn_dfn(n, current_dfn);      /* Depth first number for this node */
   set_irn_uplink(n, current_dfn);   /* ... is default uplink. */
   set_irn_loop(n, NULL);
-  current_dfn ++;
+  ++current_dfn;
   push(n);
 
-  /* AS: get_start_index might return -1 for Control Flow Nodes, and thus a negative
-     array index would be passed to is_backedge(). But CFG Nodes dont't have a backedge array,
-     so is_backedge does not access array[-1] but correctly returns false! */
-
   if (!is_outermost_StartBlock(n)) {
     int arity = get_irn_arity(n);
 
     for (i = 0; i < arity; i++) {
       ir_node *m;
-      if (is_backedge(n, i)) continue;
+
+      if (is_backedge(n, i))
+        continue;
       m = get_nodes_block(skip_Proj(get_irn_n(n, i)));
 
-      cfscc (m);
+      cfscc(m);
       if (irn_is_in_stack(m)) {
-	/* Uplink of m is smaller if n->m is a backedge.
-	   Propagate the uplink to mark the cfloop. */
-	if (get_irn_uplink(m) < get_irn_uplink(n))
-	  set_irn_uplink(n, get_irn_uplink(m));
+	      /* Uplink of m is smaller if n->m is a backedge.
+	         Propagate the uplink to mark the cfloop. */
+	      if (get_irn_uplink(m) < get_irn_uplink(n))
+	        set_irn_uplink(n, get_irn_uplink(m));
       }
     }
   }
@@ -444,12 +592,10 @@ static void cfscc (ir_node *n) {
     ir_node *tail = find_tail(n);
     if (tail) {
       /* We have a cfloop, that is no straight line code,
-	 because we found a cfloop head!
-	 Next actions: Open a new cfloop on the cfloop tree and
-	               try to find inner cfloops */
-
+         because we found a cfloop head!
+         Next actions: Open a new cfloop on the cfloop tree and
+         try to find inner cfloops */
 
-#define NO_CFLOOPS_WITHOUT_HEAD 1
 #if NO_CFLOOPS_WITHOUT_HEAD
 
       /* This is an adaption of the algorithm from fiasco / optscc to
@@ -461,12 +607,12 @@ static void cfscc (ir_node *n) {
 
       ir_loop *l;
       int close;
-      if (get_loop_n_elements(current_loop) > 0) {
-	l = new_loop();
-	close = 1;
+      if ((get_loop_n_elements(current_loop) > 0) || (is_outermost_loop(current_loop))) {
+	      l = new_loop();
+	      close = 1;
       } else {
-	l = current_loop;
-	close = 0;
+	      l = current_loop;
+	      close = 0;
       }
 
 #else
@@ -479,9 +625,9 @@ static void cfscc (ir_node *n) {
       pop_scc_unmark_visit (n);
 
       /* The current backedge has been marked, that is temporarily eliminated,
-	 by find tail. Start the scc algorithm
-	 anew on the subgraph thats left (the current cfloop without the backedge)
-	 in order to find more inner cfloops. */
+	       by find tail. Start the scc algorithm
+	       anew on the subgraph thats left (the current cfloop without the backedge)
+	       in order to find more inner cfloops. */
 
       cfscc (tail);
 
@@ -489,28 +635,28 @@ static void cfscc (ir_node *n) {
 #if NO_CFLOOPS_WITHOUT_HEAD
       if (close)
 #endif
-	close_loop(l);
+        close_loop(l);
     }
-    else
-      {
-	/* AS: No cfloop head was found, that is we have straightline code.
-	       Pop all nodes from the stack to the current cfloop. */
+    else {
+	    /* AS: No cfloop head was found, that is we have straight line code.
+	           Pop all nodes from the stack to the current cfloop. */
       pop_scc_to_loop(n);
     }
   }
 }
 
-/* Constructs backedge information for irg. */
-void construct_cf_backedges(ir_graph *irg) {
+/* Constructs control flow backedge information for irg. */
+int construct_cf_backedges(ir_graph *irg) {
   ir_graph *rem = current_ir_graph;
   ir_loop *head_rem;
   ir_node *end = get_irg_end(irg);
   int i;
 
-  assert(!interprocedural_view &&
-     "use construct_ip_backedges");
+  assert(!get_interprocedural_view() &&
+     "use construct_ip_cf_backedges()");
+  max_loop_depth = 0;
 
-  current_ir_graph = irg;
+  current_ir_graph   = irg;
   outermost_ir_graph = irg;
 
   init_scc(current_ir_graph);
@@ -521,6 +667,7 @@ void construct_cf_backedges(ir_graph *irg) {
 
   inc_irg_visited(current_ir_graph);
 
+  /* walk over all blocks of the graph, including keep alives */
   cfscc(get_irg_end_block(current_ir_graph));
   for (i = 0; i < get_End_n_keepalives(end); i++) {
     ir_node *el = get_End_keepalive(end, i);
@@ -533,23 +680,24 @@ void construct_cf_backedges(ir_graph *irg) {
   assert(get_irg_loop(current_ir_graph)->kind == k_ir_loop);
 
   current_ir_graph = rem;
+  return max_loop_depth;
 }
 
 
-void construct_ip_cf_backedges (void) {
+int construct_ip_cf_backedges (void) {
   ir_graph *rem = current_ir_graph;
-  int rem_ipv = interprocedural_view;
+  int rem_ipv = get_interprocedural_view();
   int i;
 
   assert(get_irp_ip_view_state() == ip_view_valid);
-
+  max_loop_depth = 0;
   outermost_ir_graph = get_irp_main_irg();
 
   init_ip_scc();
 
   current_loop = NULL;
   new_loop();  /* sets current_loop */
-  interprocedural_view = 1;
+  set_interprocedural_view(1);
 
   inc_max_irg_visited();
   for (i = 0; i < get_irp_n_irgs(); i++)
@@ -565,7 +713,7 @@ void construct_ip_cf_backedges (void) {
     sb = get_irg_start_block(current_ir_graph);
 
     if ((get_Block_n_cfgpreds(sb) > 1) ||
-	(get_nodes_block(get_Block_cfgpred(sb, 0)) != sb)) continue;
+      	(get_nodes_block(get_Block_cfgpred(sb, 0)) != sb)) continue;
 
     cfscc(get_irg_end_block(current_ir_graph));
   }
@@ -593,8 +741,8 @@ void construct_ip_cf_backedges (void) {
       int j;
       /* Don't visit the End node. */
       for (j = 0; j < get_End_n_keepalives(e); j++) {
-	ir_node *el = get_End_keepalive(e, j);
-	if (is_Block(el)) cfscc(el);
+	      ir_node *el = get_End_keepalive(e, j);
+	      if (is_Block(el)) cfscc(el);
       }
     }
   }
@@ -604,20 +752,30 @@ void construct_ip_cf_backedges (void) {
   assert(get_irg_loop(outermost_ir_graph)->kind == k_ir_loop);
 
   current_ir_graph = rem;
-  interprocedural_view = rem_ipv;
+  set_interprocedural_view(rem_ipv);
+  return max_loop_depth;
 }
 
-
-static void reset_backedges(ir_node *n) {
-  assert(is_Block(n));
-  int rem = interprocedural_view;
-  interprocedural_view = 1;
-  clear_backedges(n);
-  interprocedural_view = 0;
-  clear_backedges(n);
-  interprocedural_view = rem;
+/**
+ * Clear the intra- and the interprocedural
+ * backedge information pf a block.
+ */
+static void reset_backedges(ir_node *block) {
+  int rem = get_interprocedural_view();
+
+  assert(is_Block(block));
+  set_interprocedural_view(1);
+  clear_backedges(block);
+  set_interprocedural_view(0);
+  clear_backedges(block);
+  set_interprocedural_view(rem);
 }
 
+/**
+ * Reset all backedges of the first block of
+ * a loop as well as all loop info for all nodes of this loop.
+ * Recurse into all nested loops.
+ */
 static void loop_reset_backedges(ir_loop *l) {
   int i;
   reset_backedges(get_loop_node(l, 0));
@@ -634,17 +792,17 @@ void free_cfloop_information(ir_graph *irg) {
   if (get_irg_loop(irg))
     loop_reset_backedges(get_irg_loop(irg));
   set_irg_loop(irg, NULL);
-  set_irg_loopinfo_state(current_ir_graph, loopinfo_none);
+  set_irg_loopinfo_state(irg, loopinfo_none);
   /* We cannot free the cfloop nodes, they are on the obstack. */
 }
 
 
 void free_all_cfloop_information (void) {
   int i;
-  int rem = interprocedural_view;
-  interprocedural_view = 1;  /* To visit all filter nodes */
-  for (i = 0; i < get_irp_n_irgs(); i++) {
+  int rem = get_interprocedural_view();
+  set_interprocedural_view(1);  /* To visit all filter nodes */
+  for (i = get_irp_n_irgs() - 1; i >= 0; --i) {
     free_cfloop_information(get_irp_irg(i));
   }
-  interprocedural_view = rem;
+  set_interprocedural_view(rem);
 }