[Vm-dev] Re: Accelerating LargeIntegersPlugin phase 2

[Nicolas Cellier]

I've now added support for BigEndian machine to LargeIntegersPlugin
v2.0 (32 bits digits)
On such machine, LargeIntegers (Positive or Negative) will be stored
in big-endian (native) 32 bits words.
If course, images will be saved with that peculiar byteOrder by a new VM.
I used bit 7 (1<<6=64) of image headerFlags to flag the peculiarity.
Eliot, let me know if you have bigger plan for that bit, and if so,
please assign another one to my experiments.
It will be easy to add reverse support to make an image readable by an
old VM, if ever...

Of course, I've got no such BigEndian machine.
So it's up to a good soul to test it for me... (or a CI machine?)
To produce a StackInterpreter VM, load VMMaker.oscog-nice.275 from the
SmalltalkHub repository, then follow usual cog svn branch instructions
to generate, compile, ...

Before using the new VM on a BigEndian machine, a pre-requisite is to
load/merge Kernel-nice.734 because it contains a definitions of
#digitAt: #digitAt:put: and #digitLength compatible across different
VM.

There might be some nasty side effect if you try to copy
LargeInt<->ByteArray with available primitives (I know some packages
do it). When we are cheating (by letting LargeInt variable-byte) there
must be a price to pay... Maybe I'll try to address this known
limitation later.

That's all for now, my VM hacking are mostly late-night, and I need a
little rest.
Let me know if you ever try the adventure of using dangerous early
hour coding ;)

Nicolas

2013/1/19 Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com>:
> I published code on SmalltalkHub (nice occasion to test it, and I did
> not want to pollute source.squeak.org with experimental) in sync with
> .oscog branch.
> MCHttpRepository
>         location: 'http://smalltalkhub.com/mc/nice/NiceVMExperiments/main'
>         user: 'nice'
>         password: ''
>
> I also blogged about it
> http://smallissimo.blogspot.fr/2013/01/update-on-squeak-largeinteger-32-bits.html
>
> I didn't take any care to make the code 64bits friendly. This will
> require a review...
>
> Nicolas