[Vm-dev] VM Maker: VMMaker.oscog-eem.2602.mcz

[Eliot Miranda]

Thanks, Henry!

On Fri, Dec 6, 2019 at 1:53 AM Henrik Sperre Johansen <
henrik.s.johansen at veloxit.no> wrote:

>
> commits-2 wrote
> > ARMv8 has an amazingly exotic scheme for encoding bitfields as immediates
> > in logical operations.  Copy LLVM's encoder.  So far this is unverified
> > because I cannot make sense of
> >       immN:NOT(imms)
> > in
> >               len = HighestSetBit(immN:NOT(imms));
> > in DecodeBitMasks on page J1-7389 of the Arm ARM.
> > If you can make sense of this either consider fully implementing
> > CogARMv8Compiler>>decodeBitMasksN:imms:immr: or explaining to me what is
> > meant by "immN:NOT(imms)" (via email to OpenSMalltalk-VM ?).
> >
> > AdvThanksance.
>
> Is line 91 of
>
> https://github.com/NationalSecurityAgency/ghidra/blob/master/Ghidra/Processors/AARCH64/src/main/java/DecodeBitMasks.java
> of any help?
>
> Iow,
> : -> concatenate bits
> NOT -> ... not
>

In the end no.  I found other more concise code to study.  But thanks fir
the heads up.  Clever, though, isn't it?  I think I would never have come
up with a similar scheme myself.

_,,,^..^,,,_
best, Eliot
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