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From Apache Wiki <wikidi...@apache.org>
Subject [Harmony Wiki] Update of "Jitrino OPT/edge instrument" by Mikhail Fursov
Date Tue, 13 May 2008 08:37:54 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Harmony Wiki" for change notification.

The following page has been changed by Mikhail Fursov:
http://wiki.apache.org/harmony/Jitrino_OPT/edge_instrument

New page:
''' 'edge_instrument' ''' - instruments HIR with extra instructions to collect edge profile
information
[[BR]][[BR]]
The optimization creates a map of counters and inserts counter increment instructions for
every edge in Control Flow Graph. 
[[BR]]
The resulted map of counters is registered in [http://harmony.apache.org/subcomponents/drlvm/EM.html#PC
edge profile collector].
[[BR]]
Once profile collector decides that method profile is ready it initiates method recompilation
process.
[[BR]]
[[BR]]
There are 2 ways of mapping of profile information to the methods IR:
[[BR]]
1) IR based profile mapping
[[BR]]
2) Bytecode based profile mapping
[[BR]][[BR]]
To use IR based profile mapping compiler must ensure that the IR of the method is the same
during instrumentation and [:Jitrino_OPT/edge_annotate: annotation] phases
[[BR]][[BR]]
Bytecode based profile mapping is compiler independent. The 'key' for a counter is a 32-bit
value composed from 16-bit offsets in bytecode: jump-offset and target-offset. 

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