[ARM] Fix bogus -fstack-usage warning on naked functions

[Eric Botcazou]

Hi,

-fstack-usage issues the "not supported by this target" warning on naked 
functions because the prologue routines do an early return for them.

Tested on arm-eabi, may I apply it on all active branches?


2016-05-16  Eric Botcazou  <ebotca...@adacore.com>

        * config/arm/arm.c (arm_expand_prologue): Set the stack usage to 0
        for naked functions.
        (thumb1_expand_prologue): Likewise.

-- 
Eric Botcazou
Index: config/arm/arm.c
===================================================================
--- config/arm/arm.c	(revision 236264)
+++ config/arm/arm.c	(working copy)
@@ -21467,7 +21467,11 @@ arm_expand_prologue (void)
 
   /* Naked functions don't have prologues.  */
   if (IS_NAKED (func_type))
-    return;
+    {
+      if (flag_stack_usage_info)
+	current_function_static_stack_size = 0;
+      return;
+    }
 
   /* Make a copy of c_f_p_a_s as we may need to modify it locally.  */
   args_to_push = crtl->args.pretend_args_size;
@@ -24721,7 +24725,11 @@ thumb1_expand_prologue (void)
 
   /* Naked functions don't have prologues.  */
   if (IS_NAKED (func_type))
-    return;
+    {
+      if (flag_stack_usage_info)
+	current_function_static_stack_size = 0;
+      return;
+    }
 
   if (IS_INTERRUPT (func_type))
     {