(arm_volatile_func): Add comment describing purpose.

From-SVN: r9180

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index cff93d2608e3f319c5d382b8917c85f908f51f12..9995b060ee705e698b94a956ce80a96e7f44acf5 100644 (file)
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -2719,6 +2719,13 @@ output_return_instruction (operand, really_return)
   return "";
 }
 
+/* Return nonzero if optimizing and the current function is volatile
+   (ie: `noreturn').
+   Since such functions don't return call-saved registers don't need to
+   be saved.  Making such an optimization may seem dubious at first glance.
+   It was put in for a particular user who was using them to do context
+   switching and obviously wanted it to be fast.  */
+
 int
 arm_volatile_func ()
 {