optimize array instrumentation
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Key: CDV-788
URL: https://jira.terracotta.org/jira//browse/CDV-788
Project: Community Development
Issue Type: New Feature
Components: Byte Code Transform
Reporter: Tim Eck
Assignee: Issue Review Board
inspiration: http://forums.terracotta.org/forums/posts/list/1150.page
The basic idea of this feature request to make sure code that uses arrays
doesn't pay any extra instrumentation overhead. Array instrumentation is not
particularly fast since we have to check a map to figure if a given array
reference is managed or not. Given that arrays naturally lend themselves to
tight code loops, the cost of the check really adds up. Code that works with
multi-dimensional arrays get taxed even more.
A first optimization would be do to static analysis on methods that contain
array instructions to prove that given references on the stack cannot possibly
be managed (thus all TC instrumentation need not be added). An example is array
reference that is new'd within the scope of the method and is neither assigned
to any fields and/or passed to any methods. In this case there is no
opportunity for it to become shared.
Another possibility is to discover loops and determine if the "isManaged" check
can be done once instead of every time through the loop.
This type of analysis is challenging and tricky for sure, but it is possible
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