perf bench: fix assert when NDEBUG is defined

When NDEBUG is defined, the assert macro will be expanded to nothing.
Some assert calls used in perf are also including some functionality
(e.g. system calls), not only validity checks. Therefore, if NDEBUG is
defined, this functionality will be removed along with the assert.  Perf
also defines BUG_ON based on assert, so it has the same problem.

Define BUG_ON so that the condition will be executed when NDEBUG is
defined.  Replace the assert statements that have these side effects
with BUG_ON.

For defining BUG_ON, use "if (cond) {}" insted of "if (cond) ;" because
in the latter case build fails with "error: suggest braces around empty
body in an ‘if’ statement [-Werror=empty-body]"

Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1347082551-2394-1-git-send-email-irina.tirdea@intel.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>