re PR tree-optimization/26213 (new (within last few days) infinite loop with -O1)

	PR tree-optimization/26213
	* tree-ssa-threadedge.c (simplify_control_stmt_condition): Do not
	loop trying to follow SSA_NAME_VALUE chains.

	* gcc.c-torture/compile/pr26213.c: New test.

From-SVN: r110846

gcc/ChangeLog

+2006-02-10  Jeff Law  <law@redhat.com>
+
+	PR tree-optimization/26213
+	* tree-ssa-threadedge.c (simplify_control_stmt_condition): Do not
+	loop trying to follow SSA_NAME_VALUE chains.
+
 2006-02-10  Richard Guenther  <rguenther@suse.de>
 
 	* tree-dfa.c (get_ref_base_and_extent): When computing maxsize

gcc/testsuite/ChangeLog

+2006-02-10  Jeff Law  <law@redhat.com>
+
+	* gcc.c-torture/compile/pr26213.c: New test.
+
 2006-02-10  Steven G. Kargl  <kargls@comcast.net>
 
 	gfortran.dg/null_1.f90: New test.

gcc/testsuite/gcc.c-torture/compile/pr26213.c

+void
+xnanosleep (_Bool overflow)
+{
+  struct { int tv_nsec; } ts_sleep;
+  if (0 <= ts_sleep.tv_nsec)
+    overflow |= 1;
+
+  for (;;)
+    {
+      if (overflow)
+        ts_sleep.tv_nsec = 0;
+      if (foo (ts_sleep))
+        break;
+    }
+}

gcc/tree-ssa-threadedge.c

@@ -441,10 +441,14 @@ simplify_control_stmt_condition (edge e,
     {
       cached_lhs = cond;
 
-      /* Get the variable's current value from the equivalency chains.  */
-      while (cached_lhs
-	     && TREE_CODE (cached_lhs) == SSA_NAME
-	     && SSA_NAME_VALUE (cached_lhs))
+      /* Get the variable's current value from the equivalency chains.
+
+	 It is possible to get loops in the SSA_NAME_VALUE chains
+	 (consider threading the backedge of a loop where we have
+	 a loop invariant SSA_NAME used in the condition.  */
+      if (cached_lhs
+	  && TREE_CODE (cached_lhs) == SSA_NAME
+	  && SSA_NAME_VALUE (cached_lhs))
 	cached_lhs = SSA_NAME_VALUE (cached_lhs);
 
       /* If we're dominated by a suitable ASSERT_EXPR, then