re PR target/69551 (Wrong code with single element vector insert)

2016-02-26  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/69551
	* tree-ssa-structalias.c (get_constraint_for_ssa_var): When
	looking through aliases adjust DECL_PT_UID to refer to the
	ultimate alias target.

	* gcc.dg/torture/pr69951.c: New testcase.

From-SVN: r233734

gcc/ChangeLog

+2016-02-26  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/69551
+	* tree-ssa-structalias.c (get_constraint_for_ssa_var): When
+	looking through aliases adjust DECL_PT_UID to refer to the
+	ultimate alias target.
+
 2016-02-25  Martin Liska  <mliska@suse.cz>
 
 	PR middle-end/69919

gcc/testsuite/ChangeLog

+2016-02-26  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/69551
+	* gcc.dg/torture/pr69951.c: New testcase.
+
 2016-02-25  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/48795

gcc/testsuite/gcc.dg/torture/pr69951.c

+/* { dg-do run } */
+/* { dg-require-alias "" } */
+
+extern void abort (void);
+
+int a = 1, c = 1;
+extern int b __attribute__((alias("a")));
+extern int d __attribute__((alias("c")));
+int main(int argc)
+{
+  int *p, *q;
+  if (argc)
+    p = &c, q = &d;
+  else
+    p = &b, q = &d;
+  *p = 1;
+  *q = 2;
+  if (*p == 1)
+    abort();
+  return 0;
+}

gcc/tree-ssa-structalias.c

@@ -2943,6 +2943,14 @@ get_constraint_for_ssa_var (tree t, vec<ce_s> *results, bool address_p)
       if (node && node->alias && node->analyzed)
 	{
 	  node = node->ultimate_alias_target ();
+	  /* Canonicalize the PT uid of all aliases to the ultimate target.
+	     ???  Hopefully the set of aliases can't change in a way that
+	     changes the ultimate alias target.  */
+	  gcc_assert ((! DECL_PT_UID_SET_P (node->decl)
+		       || DECL_PT_UID (node->decl) == DECL_UID (node->decl))
+		      && (! DECL_PT_UID_SET_P (t)
+			  || DECL_PT_UID (t) == DECL_UID (node->decl)));
+	  DECL_PT_UID (t) = DECL_UID (node->decl);
 	  t = node->decl;
 	}
     }