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

Kelly O'Hair kelly.ohair at oracle.com
Thu Feb 2 21:29:11 UTC 2012

On Feb 2, 2012, at 8:59 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.

Not sure about OpenJDK6.

But I thought ALL the classes in JDK6 were compiled with -target 5.

As I recall the big issue was the StackMapTable attributes in -target 6 classes. Many of the classfile reader/writers had issues having to re-create the StackMaptable attribute and I vaguely recall some performance issues, and maybe some rt.jar size issues, and maybe some pack200 issues, etc. etc.

It was, how do you say it..... a 'can o worms' ???:^(

-kto

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