3 The Mono runtime implements a JIT engine for the CIL virtual
4 machine (as well as a byte code interpreter, this is to
5 quickly port it to new systems), the class loader, the garbage
6 collector, threading system and metadata access libraries.
8 We currently have two runtimes:
11 * <b>mono:</b> The Just In Time compiler implemented
12 using a BURS instruction selector. We only support
13 x86 machines in the JIT engine at this point.
15 * <b>mint:</b> The Mono interpreter. This is an
16 easy-to-port runtime engine.
19 Currently we are using the Bohem conservative garbage
22 The Mono runtime can be used as a stand-alone process, or it
23 can be <a href="embedded-api">embedded into applications</a> (see
24 the documentation in mono/samples/embed for more details).
26 Embedding the Mono runtime allows applications to be extended
27 in C# while reusing all of the existing C and C++ code.
29 Paolo Molaro did a presentation on the current JIT engine and
30 the new JIT engine. You can find his <a
31 href="http://primates.ximian.com/~lupus/slides/jit/">slides
34 ** Current JIT Engine (<b>updated, July 8th, 2002</b>)
36 The JIT engine uses a code-generator generator approach for
37 compilation. Given the properties of CIL byte codes, we can
38 take full advantage of a real instruction selector for our
41 The JIT engine implements a number of optimizations:
44 * Opcode cost estimates (our architecture allows
45 us to generate different code paths depending
46 on the target CPU dynamically).
52 Although compilers typically do
53 constant folding, the combination of inlining with
54 constant folding gives some very good results.
56 * Linear scan register allocation. In the past,
57 register allocation was our achilles heel, but now
58 we have left this problem behind.
61 There are a couple of books that deal with this technique: "A
62 Retargetable C Compiler" and "Advanced Compiler Design and
63 Implementation" are good references. You can also get a
64 technical description of <a
65 href="http://research.microsoft.com/copyright/accept.asp?path=http://www.research.microsoft.com/~drh/pubs/iburg.pdf&pub=ACM">lbrug</a>.
67 A few papers that describe the instruction selector:
70 * <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>
73 * <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>
79 We are working on a new JIT engine. The new JIT engine
80 focuses on portability and in two intermediate representations
81 that simplify the development of optimizations. This together
82 with the Ahead-of-Time compilation will allow developers to
83 deploy applications that match the speed of natively compiled code.
87 Currently we are using the Boehm conservative GC. Although our plans
88 are to move to the Intel ORP GC engine, our plans on a next generation
89 dual-JIT engine have to be taken into account.
91 We will be using the Intel ORP GC engine as it provides a precise
92 garbage collector engine, similar to what is available on the
95 Although using a conservative garbage collector like Bohem's
96 would work, all the type information is available at runtime,
97 so we can actually implement a better collector than a
98 conservative collector.
101 * Garbage collection list and FAQ:<br>
102 <a href="http://www.iecc.com/gclist/">http://www.iecc.com/gclist/</a>
104 * "GC points in a Threaded Environment":<br>
105 <a href="http://research.sun.com/techrep/1998/abstract-70.html">
106 http://research.sun.com/techrep/1998/abstract-70.html</a>
108 * "A Generational Mostly-concurrent Garbage Collector":
109 <a href="http://research.sun.com/techrep/2000/abstract-88.html">
110 http://research.sun.com/techrep/2000/abstract-88.html</a>
112 * Details on The Microsoft .NET Garbage Collection Implementation:<br>
113 <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>
114 <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>
119 The ECMA runtime and the .NET runtime assume an IO model and a
120 threading model that is very similar to the Win32 API.
122 Dick Porter has been working on the Mono abstraction layer
123 that allows our runtime to execute code that depend on this
128 Paolo Molaro found a few interesting links:
131 * On compilation of stack-based languages:<br>
132 <a href="http://www.complang.tuwien.ac.at/projects/rafts.html">
133 http://www.complang.tuwien.ac.at/projects/rafts.html</a>
135 * A paper on fast JIT compilation of a stack-based language:<br>
136 <a href="http://www.research.microsoft.com/~cwfraser/pldi99codegen.pdf">
137 http://www.research.microsoft.com/~cwfraser/pldi99codegen.pdf</a>
139 * Vmgen generates much of the code for efficient virtual machine (VM)
140 interpreters from simple descriptions of the VM instructions:<br>
141 <a href="http://www.complang.tuwien.ac.at/anton/vmgen/">
142 http://www.complang.tuwien.ac.at/anton/vmgen</a>
147 PInvoke is the mechanism we are using to wrap Unix API calls
148 as well as talking to system libraries.
150 Initially we used libffi, but it was fairly slow, so we have
151 reused parts of the JIT work to create efficient PInvoke trampolines.
155 Mono has support for remoting and proxy objects, just like
156 .NET does. The runtime provides these facilities.
160 If you are interested in porting the Mono runtime to other
161 platforms, you might find the pre-compiled <a
162 href="archive/mono-tests.tar.gz">Mono regression test
163 suite</a> useful to debug your implementation.
167 We plan on adding support for XPCOM on Unix and COM on Microsoft
168 Windows later in our development process.