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

Andrew Haley aph at redhat.com
Thu Feb 2 12:46:48 UTC 2012

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.

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