InterpreterProxy>>signed64BitIntegerFor: badly broken

Hi Guys -

I don't know if you ever used the above method but it's horribly,
horribly broken. I wrote a little test primitive (see below) that simply
used signed64BitIntegerFor(signed64BitValueOf(oop)) and then a loop like
here:

        0 to: 63 do:[:i|
                n := 1 bitShift: i.
                (self test64BitInt: n) = n ifFalse:[self halt: i].
        ].

Starting from i = 31 Every. Last. Result. Is Wrong. Can you imagine?

It gets even better, since it's broken in different ways: For i=31 the
result is negated, for everything beyound 31 the resulting large integer
is non-normalized (and therefore not comparing correctly).

Any ideas?

   - Andreas

PS. The primitive:

TestPlugin>>testSigned64BitInt
        | oop |
        self export: true.
        interpreterProxy methodArgumentCount = 1
                ifFalse:[^interpreterProxy primitiveFail].
        oop := interpreterProxy stackValue: 0.
        oop := interpreterProxy signed64BitIntegerFor: (interpreterProxy
signed64BitValueOf: oop).
        interpreterProxy failed ifFalse:[
                interpreterProxy pop: 2 thenPush: oop.
        ].