RFR: 8241232: -XX:+BootstrapJVMCI is not compatible with TieredStopAtLevel < CompLevel_full_optimization

[jiefu(傅杰)]

Hi all,

JBS:    https://bugs.openjdk.java.net/browse/JDK-8241232
Webrev: http://cr.openjdk.java.net/~jiefu/8241232/webrev.00/

An assert [1] was fired with -XX:+BootstrapJVMCI and TieredStopAtLevel<4.
The reason is that for -XX:+BootstrapJVMCI the VM is hardcoded using CompLevel_full_optimization [2].
So -XX:+BootstrapJVMCI seems not compatible with TieredStopAtLevel < 4.
It might be better to fix it.

Testing:
  - hotspot:tier1 on macosx with server-release/fastdebug

Please review it and give me some advice.

Thanks a lot.
Best regards,
Jie

[1] http://hg.openjdk.java.net/jdk/jdk/file/c1fdb04213e9/src/hotspot/share/compiler/compileBroker.cpp#l1246
[2] http://hg.openjdk.java.net/jdk/jdk/file/743c9071c317/src/hotspot/share/jvmci/jvmciCompiler.cpp#l74