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

John Rose john.r.rose at oracle.com
Mon Jul 28 23:26:30 UTC 2014

On Jul 28, 2014, at 4:09 PM, Remi Forax <forax at univ-mlv.fr> wrote:

> yes, if you do local var slot renaming for value type when parsing the bytecode,
> you can use the same mechanism for double.

Here is a concrete suggestion, to get rid of double slots completely in the setting of value types:

Deprecate and remove [ld][a]?load* and [ld][a]?store* opcodes.

In generated bytecodes, replace them by the corresponding v* opcodes (which would apply to long and double primitive values, as well as non-primitive, non-reference values).

A few other opcodes (d2i, etc.) are kept as-is, but the slot-pair semantics are removed for them also.

Later, repurpose those opcode points for other things.  (This will free the d* or l* series of instructions for later use.)

For compatibility, old class file versions would continue to use slot-pairs (and will not recognize v* bytecodes).
New class file versions would refuse (at least some of) the [dl]* bytecodes.

— John

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