Re: RFR(XS): 8143127: InvokerBytecodeGenerator emitConst should handle Byte, Short, Character

[Aleksey Shipilev]

On 11/18/2015 01:08 AM, Claes Redestad wrote:
> On 2015-11-17 22:13, Remi Forax wrote:
>> Hi Claes,
>> I fail to see how this code will not throw a CCE at runtime
>>    if (con instanceof Integer || con instanceof Byte || con instanceof
>> Short || con instanceof Character) {
>>       emitIconstInsn((int) con);
>>       ...
>>
>> (int)con is translated by the compiler to ((Integer)con).intValue()
>>
>> you have to write something like that
>>    (con instanceof Character)? (char)con: ((Number)con).intValue()
> 
> Well, this is embarrassing. I was fooled by my own sanity testing since
> javac makes the unboxing+cast work when type is known:
> 
> Character c = 'a';
> System.out.println((int)c);
> 
> but not when going through an Object reference:
> 
> Object o = 'a';
> System.out.println((int)o);
> 
> This works better:
> 
>         if (con instanceof Integer) {
>             emitIconstInsn((int) con);
>             return;
>         }
>         if (con instanceof Byte) {
>             emitIconstInsn((int)(byte)con);
>             return;
>         }
>         if (con instanceof Short) {
>             emitIconstInsn((int)(short)con);
>             return;
>         }
>         if (con instanceof Character) {
>             emitIconstInsn((int)(char)con);
>             return;
>         }

By the way, I see there is a cleaner way to implement emitIconstInsn,
see java.lang.invoke.TypeConvertingMethodAdapter.iconst:

    void iconst(final int cst) {
        if (cst >= -1 && cst <= 5) {
            mv.visitInsn(Opcodes.ICONST_0 + cst);
        } else if (cst >= Byte.MIN_VALUE && cst <= Byte.MAX_VALUE) {
            mv.visitIntInsn(Opcodes.BIPUSH, cst);
        } else if (cst >= Short.MIN_VALUE && cst <= Short.MAX_VALUE) {
            mv.visitIntInsn(Opcodes.SIPUSH, cst);
        } else {
            mv.visitLdcInsn(cst);
        }
    }

http://hg.openjdk.java.net/jdk9/dev/jdk/file/aa9e8b3916ae/src/java.base/share/classes/java/lang/invoke/TypeConvertingMethodAdapter.java#l285

Thanks,
-Aleksey