The implementation of new programming languages benefits from
interpretation because it is simple, flexible and portable. The only
downside is speed of execution, as there remains a large performance
gap between even efficient interpreters and systems that include a
just-in-time (JIT) compiler. Augmenting an interpreter with a JIT,
however, is not a small task. Today, Java JITs are typically
method-based. To compile whole methods, the JIT must re-implement
much functionality already provided by the interpreter, leading to a ``big
bang'' development effort before the JIT can be deployed. Adding a
JIT to an interpreter would be easier if we could more gradually shift
from dispatching virtual instructions bodies implemented for the interpreter
to running instructions compiled into native code by the JIT.
We show that virtual instructions implemented as lightweight callable
routines can form the basis for a very efficient interpreter. Our new
technique, interpreted traces, identifies hot paths, or traces, as a
virtual program is interpreted. By exploiting the way traces predict
branch destinations our technique markedly reduces branch
mispredictions caused by dispatch. Interpreted traces are a
high-performance technique, running about 25% faster than direct
threading.
We show that interpreted traces are a good starting point for a
trace-based JIT. We extend our interpreter so traces may contain a
mixture of compiled code for some virtual instructions and calls to
virtual instruction bodies for others. By compiling about 50 integer
and object virtual instructions to machine code we improve performance
by about 30% over interpreted traces, running about twice as fast as
the direct threaded system with which we started.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/11282 |
| Date | 01 August 2008 |
| Creators | Zaleski, Mathew |
| Contributors | Demke Brown, Angela |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
| Format | 893461 bytes, application/pdf |
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