re PR middle-end/30636 (incorrect array bounds warning on multi-dimensional arrays)

2007-02-04  Richard Guenther  <rguenther@suse.de>

	PR middle-end/30636
	* fold-const.c (try_move_mult_to_index): Make sure to not
	overflow one dimension of a multi-dimensional array access.

	* g++.dg/warn/pr30636.C: New testcase.
	* g++.dg/tree-ssa/tmmti-2.C: XFAIL parts.

From-SVN: r121575

gcc/ChangeLog

+2007-02-04  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/30636
+	* fold-const.c (try_move_mult_to_index): Make sure to not
+	overflow one dimension of a multi-dimensional array access.
+
 2007-02-04  Jan Hubicka  <jh@suse.cz>
 
 	* passes.c (init_optimization_passes): Reindent.

gcc/fold-const.c

@@ -6642,6 +6642,7 @@ try_move_mult_to_index (enum tree_code code, tree addr, tree op1)
   tree ref = TREE_OPERAND (addr, 0), pref;
   tree ret, pos;
   tree itype;
+  bool mdim = false;
 
   /* Canonicalize op1 into a possibly non-constant delta
      and an INTEGER_CST s.  */
@@ -6681,6 +6682,10 @@ try_move_mult_to_index (enum tree_code code, tree addr, tree op1)
     {
       if (TREE_CODE (ref) == ARRAY_REF)
 	{
+	  /* Remember if this was a multi-dimensional array.  */
+	  if (TREE_CODE (TREE_OPERAND (ref, 0)) == ARRAY_REF)
+	    mdim = true;
+
 	  itype = TYPE_DOMAIN (TREE_TYPE (TREE_OPERAND (ref, 0)));
 	  if (! itype)
 	    continue;
@@ -6703,8 +6708,32 @@ try_move_mult_to_index (enum tree_code code, tree addr, tree op1)
 	      delta = tmp;
 	    }
 
+	  /* Only fold here if we can verify we do not overflow one
+	     dimension of a multi-dimensional array.  */
+	  if (mdim)
+	    {
+	      tree tmp;
+
+	      if (TREE_CODE (TREE_OPERAND (ref, 1)) != INTEGER_CST
+		  || !INTEGRAL_TYPE_P (itype)
+		  || !TYPE_MAX_VALUE (itype)
+		  || TREE_CODE (TYPE_MAX_VALUE (itype)) != INTEGER_CST)
+		continue;
+
+	      tmp = fold_binary (code, itype,
+				 fold_convert (itype,
+					       TREE_OPERAND (ref, 1)),
+				 fold_convert (itype, delta));
+	      if (!tmp
+		  || TREE_CODE (tmp) != INTEGER_CST
+		  || tree_int_cst_lt (TYPE_MAX_VALUE (itype), tmp))
+		continue;
+	    }
+
 	  break;
 	}
+      else
+	mdim = false;
 
       if (!handled_component_p (ref))
 	return NULL_TREE;

gcc/testsuite/ChangeLog

+2007-02-04  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/30636
+	* g++.dg/warn/pr30636.C: New testcase.
+	* g++.dg/tree-ssa/tmmti-2.C: XFAIL parts.
+
 2007-02-03  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR middle-end/30667

gcc/testsuite/g++.dg/tree-ssa/tmmti-2.C

@@ -17,6 +17,6 @@ double bar(int i)
 	return *(&b[0].x + i*2); // b[i].x
 }
 
-/* { dg-final { scan-tree-dump "a\\\[.*i.*\\\]\\\[0\\\]" "optimized" } } */
+/* { dg-final { scan-tree-dump "a\\\[.*i.*\\\]\\\[0\\\]" "optimized" { xfail *-*-* } } } */
 /* { dg-final { scan-tree-dump "b\\\[.*i.*\\\].x" "optimized" } } */
 /* { dg-final { cleanup-tree-dump "optimized" } } */

gcc/testsuite/g++.dg/warn/pr30636.C

+/* { dg-do compile } */
+/* { dg-options "-O2 -Warray-bounds" } */
+
+typedef char one_buffer[512];
+static one_buffer emergency_buffer[4];
+
+void free_exception (void *vptr)
+{
+  char *base = (char *) &emergency_buffer[0][0];
+  char *ptr = (char *) vptr;
+  if (ptr >= base && ptr < base + sizeof (emergency_buffer)) /* { dg-bogus "subscript" } */
+    {
+      /* Do something. */
+      __builtin_exit (0);
+    }
+}
+