Is a bit field any more efficient (computationally) than masking bits and extracting the data by hand?

Question

I have a numerous small pieces of data that I want to be able to shove into one larger data type. Let\'s say that, hypothetically, this is a date and time. The obvious method is

Answer 1

Those will probably compile the the same machine code, but if it really matters, benchmark it. Or, better yet, just use the bitfield because it's easier!

Quickly testing gcc yields:

shrq    $6, %rdi             ; using bit field
movl    %edi, %eax
andl    $31, %eax

vs.

andl    $130023424, %edi     ; by-hand
shrl    $21, %edi
movl    %edi, %eax

This is a little-endian machine, so the numbers are different, but the three instructions are nearly same.