re PR tree-optimization/22615 (ICE in first_vi_for_offset, at tree-ssa-structalias.c:2858)

2005-08-14  Daniel Berlin  <dberlin@dberlin.org>

	Fix PR tree-optimization/22615

	* tree-ssa-structalias.c (solution_set_add): Handle
	first_vi_for_offset returning NULL.
	(do_da_constraint): Ditto.
	(do_sd_constraint): Ditto.
	(do_ds_constraint): Ditto
	(find_func_aliases): Ditto.
	(build_constraint_graph): RHS is allowed be ANYTHING.
	(first_vi_for_offset): Return NULL if we couldn't find anything at
	the offset.

From-SVN: r103083

gcc/ChangeLog

+2005-08-14  Daniel Berlin  <dberlin@dberlin.org>
+
+	Fix PR tree-optimization/22615
+	
+	* tree-ssa-structalias.c (solution_set_add): Handle
+	first_vi_for_offset returning NULL. 
+	(do_da_constraint): Ditto.
+	(do_sd_constraint): Ditto.
+	(do_ds_constraint): Ditto
+	(find_func_aliases): Ditto.
+	(build_constraint_graph): RHS is allowed be ANYTHING.
+	(first_vi_for_offset): Return NULL if we couldn't find anything at
+	the offset.
+	
 2005-08-14  Ulrich Weigand  <uweigand@de.ibm.com>
 
 	* config/s390/s390.c (s390_canonicalize_comparison): Prefer register

gcc/testsuite/g++.dg/tree-ssa/pr22615.C

+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+/* Ensure that we don't crash when people decide to return the address of padding.  */
+
+struct A
+{
+    char c;
+      int i;
+};
+
+A a;
+
+struct B
+{
+    char c, d;
+};
+
+union C
+{
+    A *p;
+      B *q;
+
+        C() : p(&a) {}
+	  char& foo() { return q->d; }
+};
+void bar() { C().foo() = 0; }
+

gcc/tree-ssa-structalias.c

@@ -612,6 +612,8 @@ solution_set_add (bitmap set, unsigned HOST_WIDE_INT offset)
 	{
 	  unsigned HOST_WIDE_INT fieldoffset = get_varinfo (i)->offset + offset;
 	  varinfo_t v = first_vi_for_offset (get_varinfo (i), fieldoffset);
+	  if (!v)
+	    continue;
 	  bitmap_set_bit (result, v->id);
 	}
       else if (get_varinfo (i)->is_artificial_var 
@@ -997,7 +999,7 @@ build_constraint_graph (void)
 	  /* x = &y */
 	  bitmap_set_bit (get_varinfo (lhs.var)->solution, rhs.var);
 	}
-      else if (rhs.var > anything_id && lhs.var > anything_id)
+      else if (lhs.var > anything_id)
 	{
 	  /* Ignore 0 weighted self edges, as they can't possibly contribute
 	     anything */
@@ -1332,6 +1334,8 @@ do_da_constraint (constraint_graph_t graph ATTRIBUTE_UNUSED,
 	  unsigned HOST_WIDE_INT fieldoffset = get_varinfo (j)->offset + offset;
 
 	  v = first_vi_for_offset (get_varinfo (j), fieldoffset);
+	  if (!v)
+	    continue;
 	  t = v->node;
 	  sol = get_varinfo (t)->solution;
 	  if (!bitmap_bit_p (sol, rhs))
@@ -1375,6 +1379,8 @@ do_sd_constraint (constraint_graph_t graph, constraint_t c,
 	  unsigned int t;
 
 	  v = first_vi_for_offset (get_varinfo (j), fieldoffset);	  
+	  if (!v)
+	    continue;
 	  t = v->node;
 	  if (int_add_graph_edge (graph, lhs, t, 0))
 	    flag |= bitmap_ior_into (sol, get_varinfo (t)->solution);	  
@@ -1419,6 +1425,8 @@ do_ds_constraint (constraint_graph_t graph, constraint_t c, bitmap delta)
 	  unsigned HOST_WIDE_INT fieldoffset = get_varinfo (j)->offset + loff;
 
 	  v = first_vi_for_offset (get_varinfo (j), fieldoffset);
+	  if (!v)
+	    continue;
 	  t = v->node;
 	  if (int_add_graph_edge (graph, t, rhs, roff))
 	    {
@@ -2878,7 +2886,7 @@ find_func_aliases (tree t, struct alias_info *ai)
    OFFSET.
    Effectively, walk the chain of fields for the variable START to find the
    first field that overlaps with OFFSET.
-   Abort if we can't find one.  */
+   Return NULL if we can't find one.  */
 
 static varinfo_t 
 first_vi_for_offset (varinfo_t start, unsigned HOST_WIDE_INT offset)
@@ -2894,8 +2902,7 @@ first_vi_for_offset (varinfo_t start, unsigned HOST_WIDE_INT offset)
 	return curr;
       curr = curr->next;
     }
-
-  gcc_unreachable ();
+  return NULL;
 }