RFR: 8253795: Implementation of JEP 391: macOS/AArch64 Port [v8]

[Andrew Haley]

On Sun, 31 Jan 2021 20:14:01 GMT, Anton Kozlov <akozlov at openjdk.org> wrote:

>> Please review the implementation of JEP 391: macOS/AArch64 Port.
>> 
>> It's heavily based on existing ports to linux/aarch64, macos/x86_64, and windows/aarch64. 
>> 
>> Major changes are in:
>> * src/hotspot/cpu/aarch64: support of the new calling convention (subtasks JDK-8253817, JDK-8253818)
>> * src/hotspot/os_cpu/bsd_aarch64: copy of os_cpu/linux_aarch64 with necessary adjustments (JDK-8253819)
>> * src/hotspot/share, test/hotspot/gtest: support of write-xor-execute (W^X), required on macOS/AArch64 platform. It's implemented with pthread_jit_write_protect_np provided by Apple. The W^X mode is local to a thread, so W^X mode change relates to the java thread state change (for java threads). In most cases, JVM executes in write-only mode, except when calling a generated stub like SafeFetch, which requires a temporary switch to execute-only mode. The same execute-only mode is enabled when a java thread executes in java or native states. This approach of managing W^X mode turned out to be simple and efficient enough.
>> * src/jdk.hotspot.agent: serviceability agent implementation (JDK-8254941)
>
> Anton Kozlov has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 62 commits:
> 
>  - Merge branch 'master' into jdk-macos
>  - Update copyright year for BsdAARCH64ThreadContext.java
>  - Fix inclusing of StubRoutines header
>  - Redo buildsys fix
>  - Revert harfbuzz changes, disable warnings for it
>  - Little adjustement of SlowSignatureHandler
>  - Partially bring previous commit
>  - Revert "Address feedback for signature generators"
>    
>    This reverts commit 50b55f6684cd21f8b532fa979b7b6fbb4613266d.
>  - Refactor CDS disabling
>  - Redo builsys support for aarch64-darwin
>  - ... and 52 more: https://git.openjdk.java.net/jdk/compare/8a9004da...b421e0b4

src/hotspot/cpu/aarch64/interpreterRT_aarch64.cpp line 84:

> 82: // on stack. Natural alignment for types are still in place,
> 83: // for example double/long should be 8 bytes alligned
> 84: 

This comment is a bit confusing because it's no longer #ifdef APPLE. Better move it up to Line 41.

src/hotspot/cpu/aarch64/interpreterRT_aarch64.cpp line 352:

> 350: 
> 351: #ifdef __APPLE__
> 352:   virtual void pass_byte()

Please remove ```#ifdef __APPLE__``` around this region.

src/hotspot/cpu/aarch64/sharedRuntime_aarch64.cpp line 839:

> 837:           // The code unable to handle this, bailout.
> 838:           return -1;
> 839: #endif

This looks like a bug to me. The caller doesn't necessarily check the return value. See CallRuntimeNode::calling_convention.

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PR: https://git.openjdk.java.net/jdk/pull/2200