re PR tree-optimization/31885 (Not removing empty loop, scev not finding the correct result)

	PR tree-optimization/31885
	* tree-chrec.c (chrec_contains_undetermined): Do not consider NULL_TREE
	to be undetermined.
	(automatically_generated_chrec_p): Return false for NULL.

	* gcc.dg/tree-ssa/loop-29.c: New test.

From-SVN: r124602

gcc/ChangeLog

+2007-05-10  Zdenek Dvorak  <dvorakz@suse.cz>
+
+	PR tree-optimization/31885
+	* tree-chrec.c (chrec_contains_undetermined): Do not consider NULL_TREE
+	to be undetermined.
+	(automatically_generated_chrec_p): Return false for NULL.
+
 2007-05-08  Bernd Schmidt  <bernd.schmidt@analog.com>
 
 	* config/bfin/bfin.h (MOVE_RATIO): Define.

gcc/testsuite/ChangeLog

+2007-05-10  Zdenek Dvorak  <dvorakz@suse.cz>
+
+	PR tree-optimization/31885
+	* gcc.dg/tree-ssa/loop-29.c: New test.
+
 2007-05-10 Dominique d'Humires <dominiq@lps.ens.fr>
 
 	* assumed_dummy_1.f90: Fix dg directive.

gcc/testsuite/gcc.dg/tree-ssa/loop-29.c

+/* PR 31885 */
+
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-empty" } */
+
+struct s {
+    int *blah;
+};
+
+static struct s array[] = { { 0 } };
+
+void
+foo (struct s *p)
+{
+  struct s *q = &array[1];
+  while (p < q)
+    p++;
+}
+
+/* { dg-final { scan-tree-dump-times "Removing empty loop" 1 "empty" } } */
+/* { dg-final { cleanup-tree-dump "empty" } } */

gcc/tree-chrec.c

@@ -888,11 +888,12 @@ chrec_contains_undetermined (tree chrec)
 {
   int i, n;
 
-  if (chrec == chrec_dont_know
-      || chrec == chrec_not_analyzed_yet
-      || chrec == NULL_TREE)
+  if (chrec == chrec_dont_know)
     return true;
 
+  if (chrec == NULL_TREE)
+    return false;
+
   n = TREE_OPERAND_LENGTH (chrec);
   for (i = 0; i < n; i++)
     if (chrec_contains_undetermined (TREE_OPERAND (chrec, i)))

gcc/tree-chrec.h

@@ -36,8 +36,7 @@ extern GTY(()) tree chrec_known;
 static inline bool
 automatically_generated_chrec_p (tree chrec)
 {
-  return (chrec == chrec_not_analyzed_yet 
-	  || chrec == chrec_dont_know
+  return (chrec == chrec_dont_know
 	  || chrec == chrec_known);
 }