Bug in MethodHandles.convertArguments

[Rémi Forax]

Le 11/05/2010 09:31, Raffaello Giulietti a écrit :
> Yes, this seems a bug to me, too.
>
> What about converting to Integer.class instead of int.class and letting
> the boxing duties to the language compiler?
>
> Raffaello
>    

This code is extracted from a bigger code that try to avoid boxing
if not necessary.

echo a + 3
is compiled:
aload (a)
iconst_3
invokedynamic plus(Object,int)Object

and at runtime if 'a' contains an Integer, I install a fast path
that checks if 'a' is an Integer and calls int+int.
So the fast path doesn't need to box '3'.
The slow path, box the int and call a method that will modify
the fast path.

I am currently not a able to call that method because converting
an int to an object doesn't work.

I see two workarounds:
- have one slow path by signatures:
   (int,Object), (double, Object), (Object, int) (Object, double), etc.
- don't rely on convert and use filterArguments.


Rémi

>
> On 2010-05-10 21:11, Rémi Forax wrote:
>    
>> For me it's a new bug.
>> I have checked with jdk7 latest binaries
>> I will check with the mlvm repository sources when I will be at my
>> office with a fast connection.
>>
>> public class ConvertBug {
>>     public static Object foo(Object o1, Object o2) {
>>       return null;
>>     }
>>
>>     public static void main(String[] args) {
>>       MethodHandle mh =
>> MethodHandles.lookup().findStatic(ConvertBug.class, "foo",
>>           MethodType.methodType( Object.class, Object.class, Object.class));
>>       mh = MethodHandles.convertArguments(mh,
>>           MethodType.methodType(Object.class, int.class, Object.class));
>>       System.out.println("print mh "+mh);
>>     }
>> }
>>
>> Exception in thread "main" java.lang.IllegalArgumentException:
>> mismatched parameter count
>>       at sun.dyn.MemberName.newIllegalArgumentException(MemberName.java:409)
>>       at sun.dyn.MethodHandleImpl.convertArguments(MethodHandleImpl.java:654)
>>       at sun.dyn.ToGeneric.<init>(ToGeneric.java:102)
>>       at sun.dyn.ToGeneric.of(ToGeneric.java:257)
>>       at sun.dyn.ToGeneric.make(ToGeneric.java:249)
>>       at sun.dyn.MethodHandleImpl.convertArguments(MethodHandleImpl.java:671)
>>       at java.dyn.MethodHandles.convertArguments(MethodHandles.java:811)
>>       at ConvertBug.main(ConvertBug.java:15)
>>
>>
>> and I don't see any workaround :(
>>
>> Rémi
>> _______________________________________________
>> mlvm-dev mailing list
>> mlvm-dev at openjdk.java.net
>> http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev
>>      
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