The use of register keyword in bash source code

[Peng Yu]

Hi,

I see many variables are declared with the "register" keyword. I know
its purpose is to tell compile always access the corresponding memory
without assuming the previously accessed values are preserved. This is
usually to deal with some external devices.

But I don't understand why it is useful in bash. Could anybody help
explain? Thanks.

-- 
Regards,
Peng