hg: valhalla/valhalla/langtools: Add support for tracking 'any'-related opcodes

John Rose john.r.rose at oracle.com
Mon Jul 28 23:02:50 UTC 2014

On Jul 28, 2014, at 3:09 PM, Remi Forax <forax at univ-mlv.fr> wrote:

> I suppose that value types will not use several slots, otherwise if you change a value type to add a field,
> you will need to recompile all codes that use that value type.
> So either the interpreter will treat value type as objects or it will use a double indirection ?
> (the stack will contains an index to a stack location inside the current stack frame containing all the values of the value type).

It would be unworkable to have values occupy a variable amount of interpreter (JVM state) space.  The only reasonable choice is 1 slot, which means (yes) some amount of slop and/or extra indirections.

It also means that we ought to consider deprecating and removing the double-slot pattern in a suitable version of the JVM.

— John

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