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* The Mono runtime
The Mono runtime will implement the JIT engine (and a byte
code interpreter for quickly porting to new systems), the
class loader, the garbage collector, threading system and
metadata access libraries.
We currently have two runtimes:
<ul>
* <b>mint:</b> The Mono interpreter. This is an
easy-to-port runtime engine.
* <b>mono:</b> The Just In Time compiler implemented
using a BURS instruction selector
</ul>
Currently both runtimes are missing garbage collection. We
are planning on using the ORP GC engine and deploy it by
middle January.
* COM and XPCOM
We plan on adding support for XPCOM on Unix and COM on Microsoft
Windows later in our development process.
** Executing MSIL/CIL images
The code will load an executable and map the references to
external assemblies to our own version of the assemblies on
Linux.
Our roadmap looks like this, this has been updated as of
<b>Dec 18, 2001</b>:
<ul>
* Milestone 1: <b>Done</b> Fully read and parse all CIL byte-codes
and metadata tokens (ie, a disassembler).
* Milestone 2: <b>Done</b> Complete an interpreter for CIL byte
codes. This interpreter can be used temporarly to
run CIL byte code on a system where no JIT is
available.
* Milestone 3: <b>Done</b>Define an <i>lburg</i>-like
instruction selector for the JITer for Intel.
* Milestone 4: <b>Done</b> Implement JITer. This is where our
current efforts are focused on, the JITer currently runs
all of the code we have tested on it. The major limitation
is that our class libraries are not complete, and hence not
every application can be ran.
* Milestone 5: Port of the JITer to non IA32 systems.
</ul>
A setup similar to the Kaffe JIT engine will be used to
layout the code to support non-IA32 architectures. Our work
will be focused on getting a IA32 version running first.
The JIT engine should work on Linux and Win32, although you
will need to install the CygWin32 development tools to get a
Unix-like compilation environment (mostly we use GNU make in
a few of the makefiles).
** JIT Engine (<b>updated, Dec 18th, 2001</b>)
The JIT engine uses a code-generator generator approach for
compilation. Given the properties of CIL byte codes, we can
take full advantage of a real instruction selector for our
code generator.
There are a couple of books that deal with this technique: "A
Retargetable C Compiler" and "Advanced Compiler Design and
Implementation" are good references. You can also get a
technical description of <a
href="http://research.microsoft.com/copyright/accept.asp?path=http://www.research.microsoft.com/~drh/pubs/iburg.pdf&pub=ACM">lbrug</a>.
A few papers that describe the instruction selector:
<ul>
* <a href="http://research.microsoft.com/copyright/accept.asp?path=http://www.research.microsoft.com/~drh/pubs/interface.pdf&pub=wiley">A code generation interface for ANSI C</a>
* <a href="http://research.microsoft.com/copyright/accept.asp?path=http://www.research.microsoft.com/~drh/pubs/iburg.pdf&pub=ACM">Engineering efficient code generators using tree matching and dynamic programming.</a>
</ul>
** Garbage Collection
We will be using the Intel ORP GC engine as it provides a precise
garbage collector engine, similar to what is available on the
.NET environment.
Although using a conservative garbage collector like Bohem's
would work, all the type information is available at runtime,
so we can actually implement a better collector than a
conservative collector.
<ul>
* Garbage collection list and FAQ:<br>
<a href="http://www.iecc.com/gclist/">http://www.iecc.com/gclist/</a>
* "GC points in a Threaded Environment":<br>
<a href="http://research.sun.com/techrep/1998/abstract-70.html">
http://research.sun.com/techrep/1998/abstract-70.html</a>
* "A Generational Mostly-concurrent Garbage Collector":
<a href="http://research.sun.com/techrep/2000/abstract-88.html">
http://research.sun.com/techrep/2000/abstract-88.html</a>
* Details on The Microsoft .NET Garbage Collection Implementation:<br>
<a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnmag00/html/GCI.asp">http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnmag00/html/GCI.asp</a>
<a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnmag00/html/GCI2.asp">http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnmag00/html/GCI2.asp</a>
</ul>
** IO and threading
The ECMA runtime and the .NET runtime assume an IO model and a
threading model that is very similar to the Win32 API.
Dick Porter has been working on the Mono abstraction layer
that allows our runtime to execute code that depend on this
behaviour.
** Useful links
Paolo Molaro found a few interesting links:
<ul>
* On compilation of stack-based languages:<br>
<a href="http://www.complang.tuwien.ac.at/projects/rafts.html">
http://www.complang.tuwien.ac.at/projects/rafts.html</a>
* A paper on fast JIT compilation of a stack-based language:<br>
<a href="http://www.research.microsoft.com/~cwfraser/pldi99codegen.pdf">
http://www.research.microsoft.com/~cwfraser/pldi99codegen.pdf</a>
* Vmgen generates much of the code for efficient virtual machine (VM)
interpreters from simple descriptions of the VM instructions:<br>
<a href="http://www.complang.tuwien.ac.at/anton/vmgen/">
http://www.complang.tuwien.ac.at/anton/vmgen</a>
</ul>
** PInvoke
PInvoke is the mechanism we are using to wrap Unix API calls
as well as talking to system libraries.
Initially we used libffi, but it was fairly slow, so we have
reused parts of the JIT work to create efficient PInvoke trampolines.
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