reg-stack.c (straighten_stack): Do nothing if the virtual stack is empty or has a single entry.

        * reg-stack.c (straighten_stack): Do nothing if the virtual stack is
        empty or has a single entry.

From-SVN: r22376

gcc/ChangeLog

 Thu Sep 10 01:38:05 1998  Jeffrey A Law  (law@cygnus.com)
 
+	* reg-stack.c (straighten_stack): Do nothing if the virtual stack is
+	empty or has a single entry.
+
 	* toplev.c (rest_of_compilation): Open up the dump file for reg-stack
 	before calling reg_to_stack.
 

gcc/reg-stack.c

@@ -309,6 +309,13 @@ straighten_stack (insn, regstack)
   struct stack_def temp_stack;
   int top;
 
+  /* If there is only a single register on the stack, then the stack is
+     already in increasing order and no reorganization is needed.
+
+     Similarly if the stack is empty.  */
+  if (regstack->top <= 0)
+    return;
+
   temp_stack.reg_set = regstack->reg_set;
 
   for (top = temp_stack.top = regstack->top; top >= 0; top--)