jsr instructions in OpenJDK 6 classes

[Joe Darcy]

On 02/02/2012 08:59 AM, Andrew Haley wrote:
> On 02/02/2012 04:52 PM, Joe Darcy wrote:
>> stackmaps are used.
>>
>> I haven't delved into the OpenJDK 6 build before writing this email, but
>> I suspect some of the classes in rt.jar are compiled with -target 5, but
>> javac in OpenJDK 6 defaults to -target 6 so you wouldn't see jsr
>> instructions from a stock compile.
> Well, I'm using the same compile command so that doesn't quite explain it,
> but never mind.
>
> Why are some of the classes in rt.jar are compiled with -target 5 ?
> Would it hurt simply to remove that?
>
> Andrew.

I haven't had to poke around this part of the system for a while, but 
some classes were compiled as part of bootstrapping under the previous 
platform version language level.

I don't recall offhand the earliest system OpenJDK 6 supports using as a 
bootstrap.  I don't think compiling the classes in rt.jar with -target 5 
or -target 6 should make much difference, but probably wouldn't offer 
much benefit either.  (The classes in rt.jar aren't verified anyway so 
the faster verifier doesn't help.)

-Joe