Using &LABEL

[Vincent Manis]

The decision as to whether to use jump tables
rather than a linear scan of a value/address table
is certainly a fairly trivial thing for any compiler
to do, and one should most certainly not expect programmers
to have to think about it. The BCPL/370 compiler written at
Cambridge about 1970 did that properly, and I can see no
reason why any C compiler would find it hard to do.

Essentially, you measure the "packing factor" of an indexed jump 
table, and if it is lower than some figure (say 50%, but it
would depend on how precious address space and CPU cycles are),
you select the linear scan, and if the packing factor is greater 
than 50% you use the indexed jump.

The packing factor is computed by determining the range
(max case value-min case value) and dividing by the number
of entries.

I personally can see absolutely no use whatsoever for &label, 
(&function, on the other hand is extremely useful), and would
be quite happy to see its existence deferred indefinitely.