RFR: 8255718: Zero: VM should know it runs in interpreter-only mode

[Aleksey Shipilev]

There are many tests in tier1 that fail with Zero, because they supply -XX:+TieredCompilation, and that makes VM code believe it runs in "mixed" mode. 

Can be reproduced trivially by running anything with -XX:+TieredCompilation. Then Zero fails when runtime asks it to produce a native wrapper for MH intrinsics. That code is normally protected by Arguments::is_interpreter_only.

Method* SystemDictionary::find_method_handle_intrinsic(vmIntrinsics::ID iid,
                                                       Symbol* signature,
                                                       TRAPS) {
    ...
    if (!Arguments::is_interpreter_only()) {  // <--- checks here
      // Generate a compiled form of the MH intrinsic.
      AdapterHandlerLibrary::create_native_wrapper(m); // <--- fails through here
    }

Then in `sharedRuntime_zero.cpp`:

nmethod *SharedRuntime::generate_native_wrapper(MacroAssembler *masm,
                                                const methodHandle& method,
                                                int compile_id,
                                                BasicType *sig_bt,
                                                VMRegPair *regs,
                                                BasicType ret_type,
                                                address critical_entry) {
  ShouldNotCallThis();  // <--- crashes here
  return NULL;
}

...so:

$ build/linux-x86_64-zero-fastdebug/images/jdk/bin/java -XX:+TieredCompilation 
OpenJDK 64-Bit Zero VM warning: -XX:+TieredCompilation not supported in this VM
# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc:  SuppressErrorAt=/sharedRuntime_zero.cpp:80
#
# A fatal error has been detected by the Java Runtime Environment:
#
#  Internal Error (/home/shade/trunks/jdk/src/hotspot/cpu/zero/sharedRuntime_zero.cpp:80), pid=404967, tid=404968
#  Error: ShouldNotCall()

Additional testing:
 - [x] ad-hoc Hello World runs with Linux x86_64 Zero
 - [x] re-run some failed `tier1` tests with Linux x86_64 Zero, now passing

-------------

Commit messages:
 - 8255718: Zero: VM should know it runs in interpreter-only mode

Changes: https://git.openjdk.java.net/jdk/pull/985/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=985&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255718
  Stats: 5 lines in 1 file changed: 5 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/985.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/985/head:pull/985

PR: https://git.openjdk.java.net/jdk/pull/985