RFR: 8251462: Remove legacy compilation policy [v4]

[Vladimir Kozlov]

On Fri, 22 Jan 2021 18:26:43 GMT, Igor Veresov <iveresov at openjdk.org> wrote:

>> Hmm, may be we don't need these funxctions.
>> Seems is_c1_only() will be true only when JVMCI is off. Right? We can also reinforce it to exclude AOT too.
>> And AOT and JVMCI are disabled with -Xint.
>
> It's not so easy. You can have AOT or JVMCI enabled with -Xint. JVMCI code installs can be initiated not only as a result of method going through the compiler broker. Remember that you can run Graal in "host" mode, where it is a normal C1/C2 system (or may be just an interpreter); Truffle can work in a mode like that. And you can totally run with AOT and interpreter (without any JIT).

I don't think so:
> java -Xint -XX:+UnlockExperimentalVMOptions -XX:+EnableJVMCI -version
Java HotSpot(TM) 64-Bit Server VM warning: JVMCI Compiler disabled due to -Xint.

> java -Xint -XX:+UnlockExperimentalVMOptions -XX:+UseAOT -XX:+PrintAOT -version
Java HotSpot(TM) 64-Bit Server VM warning: -Xint is not compatible with AOT (switching AOT off)

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PR: https://git.openjdk.java.net/jdk/pull/1985