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

[Vicente Romero]

Hi all,

I have just pushed a patch that converts class literals into a poly 
expression. Meaning that now you can pass a class literal where a 
ClassConstant is expected. This will simplify the use of the API making 
the user code less verbose. Taking as an example the test case sent by 
Tagir, it could be now rewritten as:

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(MH.class, "test", 
MethodTypeConstant.of(void.class)));
     handle.invokeExact();
   }
}

Thanks,
Vicente


On 04/18/2017 11:14 PM, Tagir Valeev wrote:
> Thank you for the hint! It also seems that ClassConstant.of(MH.class) 
> does not work either and VarHandles are not supported yet. However the 
> following sample finally worked for me:
>
>
> 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("LMH;"), "test", 
> MethodTypeConstant.of(ClassConstant.of("V"))));
>     handle.invokeExact();
>   }
> }
>
> With best regards,
> Tagir Valeev.
>
>
> On Tue, Apr 18, 2017 at 9:13 PM, Brian Goetz <brian.goetz at oracle.com 
> <mailto:brian.goetz at oracle.com>> wrote:
>
>     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.Int
>         <http://java.lang.invoke.Int>rinsics.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 <mailto: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
>             <http://hg.openjdk.java.net/amber/amber/jdk/rev/2eeb80b82c9c>
>             [2]
>             http://hg.openjdk.java.net/amber/amber/langtools/rev/7be70b52c760
>             <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/
>                 <http://cr.openjdk.java.net/%7Ebriangoetz/JDK-8178320/webrev/>
>
>                 Prototype implementation coming soon.
>
>
>
>
>