perf probe: Correct error message for non-structure type

perf probe outputs incorrect error message when it is called with
non-existent field on a non-data structure local variable.

<Before>
 # perf probe vfs_read 'count.hoge'
  Fatal: Structure on a register is not supported yet.
 # perf probe vfs_read 'count->hoge'
  Fatal: Semantic error: hoge must be referred by '.'

This corrects the messsage.

<After>
 # perf probe vfs_read 'count.hoge'
  Fatal: count is not a data structure.
 # perf probe vfs_read 'count->hoge'
  Fatal: count is not a data structure.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
LKML-Reference: <20100402165052.23551.75866.stgit@localhost6.localdomain6>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/util/probe-finder.c

@@ -429,23 +429,27 @@ static void convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
 		if (die_get_real_type(&type, &type) == NULL)
 			die("Failed to get a type information of %s.", varname);
 
+		/* Verify it is a data structure  */
+		if (dwarf_tag(&type) != DW_TAG_structure_type)
+			die("%s is not a data structure.", varname);
+
 		ref = xzalloc(sizeof(struct kprobe_trace_arg_ref));
 		if (*ref_ptr)
 			(*ref_ptr)->next = ref;
 		else
 			*ref_ptr = ref;
 	} else {
+		/* Verify it is a data structure  */
+		if (dwarf_tag(&type) != DW_TAG_structure_type)
+			die("%s is not a data structure.", varname);
+
 		if (field->ref)
 			die("Semantic error: %s must be referred by '.'",
 			    field->name);
 		if (!ref)
 			die("Structure on a register is not supported yet.");
 	}
 
-	/* Verify it is a data structure  */
-	if (dwarf_tag(&type) != DW_TAG_structure_type)
-		die("%s is not a data structure.", varname);
-
 	if (die_find_member(&type, field->name, &member) == NULL)
 		die("%s(tyep:%s) has no member %s.", varname,
 		    dwarf_diename(&type), field->name);