RFR: 8245717: VM option "-XX:EnableJVMCIProduct" could not be repetitively enabled

[Xiaohong Gong]

Hi,

Could you please help to review this simple patch? It fixes the issue that JVM crashes
in debug mode when the vm option "-XX:EnableJVMCIProduct" is enabled repetitively.

JBS: https://bugs.openjdk.java.net/browse/JDK-8245717
Webrev: http://cr.openjdk.java.net/~xgong/rfr/8245717/webrev.00/

Repetitively enabling the vm option "-XX:+EnableJVMCIProduct" in the command
line makes the assertion fail in debug mode: "assert(is_experimental(), sanity)".

It happens when the VM iteratively parses the options from command line. When the
matched option is "-XX:+EnableJVMCIProduct", the original experimental JVMCI flags
will be converted to product mode, with the above assertion before it. So if all
the JVMCI flags have been converted to the product mode at the first time parsing
"-XX:+EnableJVMCIProduct", the assertion will fail at the second time it is parsed.

A simple fix is to just ignoring the conversion if this option has been parsed.

Testing:
Tested jtreg hotspot::hotspot_all_no_apps,jdk::jdk_core,langtools::tier1
and jcstress:tests-custom, and all tests pass without new failure.

Thanks,
Xiaohong Gong