Adopting JEP 303 (Intrinsics for LDC and INVOKEDYNAMIC) into Amber

[Brian Goetz]

The primitive fields (Constables.VOID and friends) are not yet hooked 
up; for the time being, replace with ClassConstant.of("V").

On 4/18/2017 2:17 AM, Tagir Valeev wrote:
> Hello!
>
> I tried to play with this, but still no success. Fresh build from
> constant-folding branch. I tried to compile the following files:
>
> // MH.java
>
> import java.lang.invoke.*;
> import java.lang.invoke.Constables.*;
> import java.lang.reflect.*;
>
> public class MH {
>    private static void test() {
>      System.out.println("Hello");
>    }
>
>
>    public static void main(String[] args) throws Throwable {
>      final MethodHandle handle = Intrinsics.ldc(
>       MethodHandleConstant.ofStatic(ClassConstant.of(MH.class), "test",
> MethodTypeConstant.of(Constables.VOID)));
>      handle.invokeExact();
>    }
>
> }
>
> // VH.java
> import java.lang.invoke.*;
> import java.lang.invoke.Constables.*;
> import java.lang.reflect.*;
>
> public class VH {
>    private static volatile int counter;
>
>    private static final VarHandle COUNTER = Intrinsics.ldc(
>       VarHandleConstant.ofStaticField(ClassConstant.of(VH.class), "counter",
> Constables.INT));
>
>    public static void main(String[] args) {
>      System.out.println(COUNTER.getAndAdd(1));
>      System.out.println(COUNTER.getAndAdd(1));
>    }
> }
>
> Building with "javac -XDdoConstantFold=true MH.java" or "javac
> -XDdoConstantFold=true VH.java",
> javac silently exists without producing .class file or reporting any error.
> Tried with -verbose, the output ends like this:
>
> [loading /modules/java.base/java/lang/annotation/RetentionPolicy.class]
> [loading /modules/java.base/java/lang/annotation/Target.class]
> [loading /modules/java.base/java/lang/annotation/ElementType.class]
> [checking VH]
> [loading /modules/java.base/java/io/Serializable.class]
> [loading /modules/java.base/java/lang/AutoCloseable.class]
> [loading /modules/java.base/java/lang/Class.class]
> [loading /modules/java.base/java/lang/invoke/Constable.class]
> [loading /modules/java.base/java/lang/invoke/Intrinsics.class]
> [total 1484ms]
>
> Without  -XDdoConstantFold=true the class file is produced and dies like
>
> Exception in thread "main" java.lang.UnsupportedOperationException: no
> reflective access
> at java.base/java.lang.invoke.Intrinsics.ldc(Intrinsics.java:42)
> at MH.main(MH.java:12)
>
> Which is expected behavior, I guess.
>
> Am I doing something wrong? Could you compile these files on your side?
> Sorry if my tries look lame: I'm very new to this.
>
> With best regards,
> Tagir Valeev.
>
> On Tue, Apr 18, 2017 at 9:07 AM, Vicente Romero <vicente.romero at oracle.com>
> wrote:
>
>> Hi,
>>
>> Support for JEP 303 has been pushed in the amber repo [1, 2] (branch name
>> is 'constant-folding'). The development is mature although there are some
>> fresh areas like using reflection for accessing the API methods. Reflection
>> is needed as the classes defined in the API see [1] are not available in
>> the boot JDK. There is still some ongoing research so some changes to the
>> API and the code are to be expected in the near future,
>>
>> Thanks,
>> Vicente
>>
>>
>> [1] http://hg.openjdk.java.net/amber/amber/jdk/rev/2eeb80b82c9c
>> [2] http://hg.openjdk.java.net/amber/amber/langtools/rev/7be70b52c760
>>
>>
>> On 04/17/2017 04:22 PM, Brian Goetz wrote:
>>
>>> JEP 303 (Intrinsics for LDC and INVOKEDYNAMIC) is hereby adopted into
>>> Project Amber.
>>>
>>> A first draft of the API can be found at:
>>>
>>>      http://cr.openjdk.java.net/~briangoetz/JDK-8178320/webrev/
>>>
>>> Prototype implementation coming soon.
>>>
>>>
>>>