It doesn't cost much, but it's used _a lot_, so optimizing it makes sense.
name old time/op new time/op delta
TxHash-8 4.89ns ± 5% 0.54ns ± 2% -88.86% (p=0.008 n=5+5)
name old alloc/op new alloc/op delta
TxHash-8 0.00B 0.00B ~ (all equal)
name old allocs/op new allocs/op delta
TxHash-8 0.00 0.00 ~ (all equal)
ffeb3b8473