Re: Switch statement code generation

"Joshua Cranmer" <Pidgeot18@verizon.invalid> wrote in message
news:09-11-009@comp.compilers...
> On 11/04/2009 12:27 AM, glen herrmannsfeldt wrote:
>> I believe that JVM also has a special instruction for this
>> operation, as the above likely don't work there.
>
> Actually two special bytecodes, lookupswitch and tableswitch. These are
> the linear scan and the jump table methods, respectively. The upcoming
> string switch appears to use a hash routine.


Hey, that's what I use.. invented independently of course.


'switch' for an indexed jump table, for case values in the range of 500 or
1000 (between minimum and maximum values).
'cswitch' for other case values, which just does a linear search.


Since these implement 'Switch' for an interpreted language, with the cswitch
bytecode implemented in tight assembler, opting for a linear search doesn't
have as much impact as it would do in a compiled language, especially if the
most common cases appear first.


However, with a big enough table size then I guess a proper lookup is called
for.


--
Bartc

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