RFR: 8251462: Remove legacy compilation policy [v3]

[Igor Veresov]

On Fri, 22 Jan 2021 17:32:09 GMT, Igor Veresov <iveresov at openjdk.org> wrote:

>> src/hotspot/share/compiler/compileBroker.cpp line 972:
>> 
>>> 970: 
>>> 971:   // Initialize the compilation queue
>>> 972:   if (_c2_count > 0) {
>> 
>> Is ZERO treated as `is_interpreter_only()` ? How this change works with ZERO?
>
> I forgot why I removed that. Let me put it back and run it through testing again.

So the reason for that was an awkward possibility of ending up with 0 compilers. That was because during the argument check in ```CompilerConfig::check_args_consistency()``` We checked for ```Arguments::is_interpreter_only()``` instead  of ```CompilerConfig::is_interpreter_only()```. The former doesn't check if ```TieredStopAtLevel=0``` is present. Anyways, I fixed the check and reverted this change.

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