Re: [patch] O(1) PHI argument look-up - Part 1/n

[Kazu Hirata <kazu at cs dot umass dot edu>]

Hi Diego,

> > Can I go with the original patch except that I address the comment
> > issues above?
> > 
> Sure.

Here is the final patch that I committed.

Kazu Hirata

2004-11-19  Kazu Hirata  <kazu@cs.umass.edu>

	* basic-block.h (edge_def): Add dest_idx.
	* cfg.c (unchecked_make_edge): Initialize dest_idx.
	(remove_edge): Simplify the disconnection of an edge from its
	destination.
	(redirect_edge_succ): Likewise.
	* cfghooks.c (verify_flow_info): Check the consistency of
	dest_idx for each edge.

Index: basic-block.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/basic-block.h,v
retrieving revision 1.227
diff -u -d -p -r1.227 basic-block.h
--- basic-block.h	17 Nov 2004 22:05:58 -0000	1.227
+++ basic-block.h	19 Nov 2004 22:06:58 -0000
@@ -154,6 +154,10 @@ struct edge_def GTY(())
   int probability;		/* biased by REG_BR_PROB_BASE */
   gcov_type count;		/* Expected number of executions calculated
 				   in profile.c  */
+
+  /* The index number corresponding to this edge in the edge vector
+     dest->preds.  */
+  unsigned int dest_idx;
 };
 
 typedef struct edge_def *edge;
Index: cfg.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cfg.c,v
retrieving revision 1.73
diff -u -d -p -r1.73 cfg.c
--- cfg.c	9 Nov 2004 04:21:49 -0000	1.73
+++ cfg.c	19 Nov 2004 22:06:58 -0000
@@ -276,6 +276,7 @@ unchecked_make_edge (basic_block src, ba
   e->src = src;
   e->dest = dst;
   e->flags = flags;
+  e->dest_idx = EDGE_COUNT (dst->preds) - 1;
 
   return e;
 }
@@ -355,11 +356,13 @@ remove_edge (edge e)
 {
   edge tmp;
   basic_block src, dest;
+  unsigned int dest_idx;
   bool found = false;
   edge_iterator ei;
 
   src = e->src;
   dest = e->dest;
+  dest_idx = e->dest_idx;
 
   for (ei = ei_start (src->succs); (tmp = ei_safe_edge (ei)); )
     {
@@ -375,20 +378,12 @@ remove_edge (edge e)
 
   gcc_assert (found);
 
-  found = false;
-  for (ei = ei_start (dest->preds); (tmp = ei_safe_edge (ei)); )
-    {
-      if (tmp == e)
-	{
-	  VEC_unordered_remove (edge, dest->preds, ei.index);
-	  found = true;
-	  break;
-	}
-      else
-	ei_next (&ei);
-    }
+  VEC_unordered_remove (edge, dest->preds, dest_idx);
 
-  gcc_assert (found);
+  /* If we removed an edge in the middle of the edge vector, we need
+     to update dest_idx of the edge that moved into the "hole".  */
+  if (dest_idx < EDGE_COUNT (dest->preds))
+    EDGE_PRED (dest, dest_idx)->dest_idx = dest_idx;
 
   free_edge (e);
 }
@@ -398,28 +393,20 @@ remove_edge (edge e)
 void
 redirect_edge_succ (edge e, basic_block new_succ)
 {
-  edge tmp;
-  edge_iterator ei;
-  bool found = false;
+  basic_block dest = e->dest;
+  unsigned int dest_idx = e->dest_idx;
 
-  /* Disconnect the edge from the old successor block.  */
-  for (ei = ei_start (e->dest->preds); (tmp = ei_safe_edge (ei)); )
-    {
-      if (tmp == e)
-	{
-	  VEC_unordered_remove (edge, e->dest->preds, ei.index);
-	  found = true;
-	  break;
-	}
-      else
-	ei_next (&ei);
-    }
+  VEC_unordered_remove (edge, dest->preds, dest_idx);
 
-  gcc_assert (found);
+  /* If we removed an edge in the middle of the edge vector, we need
+     to update dest_idx of the edge that moved into the "hole".  */
+  if (dest_idx < EDGE_COUNT (dest->preds))
+    EDGE_PRED (dest, dest_idx)->dest_idx = dest_idx;
 
   /* Reconnect the edge to the new successor block.  */
   VEC_safe_push (edge, new_succ->preds, e);
   e->dest = new_succ;
+  e->dest_idx = EDGE_COUNT (new_succ->preds) - 1;
 }
 
 /* Like previous but avoid possible duplicate edge.  */
Index: cfghooks.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cfghooks.c,v
retrieving revision 1.18
diff -u -d -p -r1.18 cfghooks.c
--- cfghooks.c	4 Nov 2004 22:02:55 -0000	1.18
+++ cfghooks.c	19 Nov 2004 22:06:58 -0000
@@ -178,6 +178,20 @@ verify_flow_info (void)
 	      fputc ('\n', stderr);
 	      err = 1;
 	    }
+
+	  if (ei.index != e->dest_idx)
+	    {
+	      error ("basic block %d pred edge is corrupted", bb->index);
+	      error ("its dest_idx should be %d, not %d",
+		     ei.index, e->dest_idx);
+	      fputs ("Predecessor: ", stderr);
+	      dump_edge_info (stderr, e, 0);
+	      fputs ("\nSuccessor: ", stderr);
+	      dump_edge_info (stderr, e, 1);
+	      fputc ('\n', stderr);
+	      err = 1;
+	    }
+
 	  edge_checksum[e->dest->index + 2] -= (size_t) e;
 	}
     }