Macro timed_span 

macro_rules! timed_span {
    ($entry:expr, $counters:expr $(,)?) => { ... };
}

Starts a timed span and returns its guard.

The first argument is an enum variant that can be cast to an index. The second is an indexable collection whose entries implement TimingCounter. Bind the returned guard for the scope to measure. When dropped, it adds the elapsed measurement, even if the scope returns early or unwinds. On x86, x86_64, and aarch64 the elapsed value is a processor-counter tick count; on other architectures it is elapsed nanoseconds.