jsr instructions in OpenJDK 6 classes (original) (raw)

Joe Darcy joe.darcy at oracle.com
Thu Feb 2 17:08:10 UTC 2012

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

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