ada: Exception-raising loop incorrectly eliminated

If the body of a loop includes a raise statement then the loop should not be
considered to be free of side-effects and therefore eligible for elimination
by the compiler.

gcc/ada/ChangeLog:

	* sem_util.adb
	(Side_Effect_Free_Statements): Return False if the statement list
	includes an explicit (i.e. Comes_From_Source) raise statement.
diff --git a/gcc/ada/sem_util.adb b/gcc/ada/sem_util.adb
index b833b35..7757e04 100644
--- a/gcc/ada/sem_util.adb
+++ b/gcc/ada/sem_util.adb
@@ -12425,9 +12425,14 @@
 
       while Present (Node) loop
          case Nkind (Node) is
-            when N_Null_Statement | N_Call_Marker | N_Raise_xxx_Error =>
+            when N_Null_Statement | N_Call_Marker =>
                null;
 
+            when N_Raise_xxx_Error =>
+               if Comes_From_Source (Node) then
+                  return False;
+               end if;
+
             when N_Object_Declaration =>
                if Present (Expression (Node))
                  and then not Side_Effect_Free (Expression (Node))