re PR tree-optimization/21847 (misscompiling of the following java code)

	PR tree-optimization/21847
	* tree-ssa-dce.c (mark_stmt_if_obviously_necessary): With
	-fnon-call-exceptions, also mark statements inherently
	necessary if they may throw.

From-SVN: r100714

gcc/ChangeLog

+2005-06-07  Steven Bosscher  <stevenb@suse.de>
+
+	PR tree-optimization/21847
+	* tree-ssa-dce.c (mark_stmt_if_obviously_necessary): With
+	-fnon-call-exceptions, also mark statements inherently
+	necessary if they may throw.
+
 2005-06-07  Adrian Straetling  <straetling@de.ibm.com>
 
 	* config/s390/s390.md: ("UNSPECV_MB", "UNSPECV_CAS"): New constants.

gcc/tree-ssa-dce.c

@@ -279,6 +279,15 @@ mark_stmt_if_obviously_necessary (tree stmt, bool aggressive)
   tree op, def;
   ssa_op_iter iter;
 
+  /* With non-call exceptions, we have to assume that all statements could
+     throw.  If a statement may throw, it is inherently necessary.  */
+  if (flag_non_call_exceptions
+      && tree_could_throw_p (stmt))
+    {
+      mark_stmt_necessary (stmt, true);
+      return;
+    }
+
   /* Statements that are implicitly live.  Most function calls, asm and return
      statements are required.  Labels and BIND_EXPR nodes are kept because
      they are control flow, and we have no way of knowing whether they can be