jsr instructions in OpenJDK 6 classes

[Andrew Haley]

I'm sorry for the cross-post, but I don't know exactly who to
address this to.

Just to save you time reading all this: the javac in OpenJDK 6
generates jsr instructions, but only if you compile a great many
source files in one go.  This affects rt.jar.  I'm trying to find
out why.

If you build OpenJDK6 and do this:

happy:jdk6 $ javap -c -bootclasspath build/linux-amd64/classes/ -classpath build/linux-amd64/classes/ java.util.concurrent/PriorityBlockingQueue | grep jsr
   48:  jsr     62
   56:  jsr     62
   17:  jsr     28
   23:  jsr     28
   74:  jsr     87
 ...

you'll see lots of jsr instructions.  Why is this?  It seems that if
you compile the .java file this doesn't happen:

happy:jdk6 $ ./build/linux-amd64/j2sdk-image/jre/bin/java -Xmx896m -Xms128m -XX:PermSize=32m -XX:MaxPermSize=160m -Xbootclasspath/p:./build/linux-amd64/langtools/dist/bootstrap/lib/javac.jar -jar ./build/linux-amd64/langtools/dist/bootstrap/lib/javac.jar -g -source 1.5 -target 5 -encoding ascii -Xbootclasspath:/local/openjdk/jdk6/build/linux-amd64/classes -sourcepath /local/openjdk/jdk6/build/linux-amd64/gensrc:/local/openjdk/jdk6/jdk/src/solaris/classes:/local/openjdk/jdk6/jdk/src/share/classes -d /tmp
/local/openjdk/jdk6/jdk/src/share/classes/java/util/concurrent/PriorityBlockingQueue.java

happy:jdk6 $  javap -c -bootclasspath /tmp -classpath /tmp java.util.concurrent/PriorityBlockingQueue | grep jsr

No jsr instructions this time.

So, I try the compile again, but with the full list of classes in .classes.list:

 $  $ /local/openjdk/jdk6/build/linux-amd64/j2sdk-image/jre/bin/java -Xmx896m -Xms128m -XX:PermSize=32m -XX:MaxPermSize=160m -Xbootclasspath/p:/local/openjdk/jdk6/build/linux-amd64/langtools/dist/bootstrap/lib/javac.jar -jar /local/openjdk/jdk6/build/linux-amd64/langtools/dist/bootstrap/lib/javac.jar -g -source 1.5 -target 5 -encoding ascii -Xbootclasspath:/local/openjdk/jdk6/build/linux-amd64/classes -sourcepath
/local/openjdk/jdk6/build/linux-amd64/gensrc:/local/openjdk/jdk6/jdk/src/solaris/classes:/local/openjdk/jdk6/jdk/src/share/classes -d /tmp @/local/openjdk/jdk6/build/linux-amd64/tmp/java/java.lang/java/.classes.list

 $  javap -c -bootclasspath /tmp -classpath /tmp java.util.concurrent/PriorityBlockingQueue | grep jsr | head -5
   48:  jsr     62
   56:  jsr     62
   17:  jsr     28
   23:  jsr     28
   74:  jsr     87

Lots of jsrs.

Now the really weird bit: if I edit classes.list to contain only a
small subset of the files and run the command again,

 $ grep java.util.concurrent /local/openjdk/jdk6/build/linux-amd64/tmp/java/java.lang/java/.classes.list > classes.concurrent

 $ /local/openjdk/jdk6/build/linux-amd64/j2sdk-image/jre/bin/java -Xmx896m -Xms128m -XX:PermSize=32m -XX:MaxPermSize=160m -Xbootclasspath/p:/local/openjdk/jdk6/build/linux-amd64/langtools/dist/bootstrap/lib/javac.jar -jar /local/openjdk/jdk6/build/linux-amd64/langtools/dist/bootstrap/lib/javac.jar -g -source 1.5 -target 5 -encoding ascii -Xbootclasspath:/local/openjdk/jdk6/build/linux-amd64/classes -sourcepath
/local/openjdk/jdk6/build/linux-amd64/gensrc:/local/openjdk/jdk6/jdk/src/solaris/classes:/local/openjdk/jdk6/jdk/src/share/classes -d /tmp @classes.concurrent

 $  javap -c -bootclasspath /tmp -classpath /tmp java.util.concurrent/PriorityBlockingQueue | grep jsr | head -5

... no jsr instructions.

I realize that OpenJDK 6 is nearing EOL, but this behaviour is so bizarre
that I'd appreciate some input!

Thanks,
Andrew.