Fix comment for cmse_nonsecure_call_clear_caller_saved

2017-05-17  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    gcc/
    * config/arm/arm.c (cmse_nonsecure_call_clear_caller_saved): Refer
    readers to __gnu_cmse_nonsecure_call libcall for saving, clearing and
    restoring of callee-saved registers.

From-SVN: r248142

gcc/ChangeLog

+2017-05-17  Thomas Preud'homme  <thomas.preudhomme@arm.com>
+
+	* config/arm/arm.c (cmse_nonsecure_call_clear_caller_saved): Refer
+	readers to __gnu_cmse_nonsecure_call libcall for saving, clearing and
+	restoring of callee-saved registers.
+
 2017-05-17  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* compare-elim.c (equivalent_reg_at_start): Adjust outdated comment.

gcc/config/arm/arm.c

@@ -16909,9 +16909,10 @@ compute_not_to_clear_mask (tree arg_type, rtx arg_rtx, int regno,
   return not_to_clear_mask;
 }
 
-/* Saves callee saved registers, clears callee saved registers and caller saved
-   registers not used to pass arguments before a cmse_nonsecure_call.  And
-   restores the callee saved registers after.  */
+/* Clears caller saved registers not used to pass arguments before a
+   cmse_nonsecure_call.  Saving, clearing and restoring of callee saved
+   registers is done in __gnu_cmse_nonsecure_call libcall.
+   See libgcc/config/arm/cmse_nonsecure_call.S.  */
 
 static void
 cmse_nonsecure_call_clear_caller_saved (void)