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

[Andrew John Hughes]

On Sun, 1 Nov 2020 17:24:44 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> 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

Seems sensible to me.

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

Marked as reviewed by andrew (Reviewer).

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