Compiler controls are essential for performance testing and benchmarking. JMH uses compiler controls extensively to provide a reliable benchmarking environment. As the part of performance studies for compiler control project, we would need to see that proposed implementation does not regress current compiler control mechanisms, as well as provides a consistent performance for it.
a) The functionality of -XX:CompileCommand=... and -XX:CompileCommandFile=...; both are used by JMH, mostly with inline/dontinline modes.
b) The performance of -XX:CompileCommand=... and -XX:CompileCommandFile=...; there is already known issues (JDK-8057169) that should not get worse with this change.