Summary
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Enabling JVMTI `SingleStep` events do not enforce `interp-only` execution mode anymore.

Problem
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Enforcing the `interp-only` execution mode to support JVMTI `SingleStep` events causes significant execution slowdown (~20X).

Solution
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Do not enforce interp-only` execution mode to support v JVMTI `SingleStep` events. Instead, just deoptimize target frame and disable OSR (On Stack Replacement) optimization on it, so that it is kept interpreted. This allows to execute in a compiled mode other methods recursively called from this frame.


Specification
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N/A - the specification has not been changed.
This may need a Release Note.