RFR: 8286360: ARM32: Fix crashes after JDK-8284161 (Virtual Threads)

[Dmitry Samersoff]

On Tue, 10 May 2022 15:51:10 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Virtual Threads are not fully implemented on ARM32, but there is a fallback implementation that can be used. Still, there is some VM code that is executed unconditionally anyway, crashing the VM on some tests. This improves the ARM32 code to the point that VM is able to build itself and pass tests. This adds the scaffolding for full implementation too.
> 
> Additional testing:
>  - [x] Linux arm32 fastdebug build
>  - [x] Linux arm32 fastdebug, `jdk_loom  hotspot_loom` pass

Marked as reviewed by dsamersoff (Reviewer).

src/hotspot/cpu/arm/frame_arm.inline.hpp line 47:

> 45: }
> 46: 
> 47: inline frame::frame(intptr_t* sp) {

Will AArch64 code work?

inline frame::frame(intptr_t* sp) : frame(sp, sp, *(intptr_t**)(sp - frame::sender_sp_offset), *(address*)(sp - 1)) {}

src/hotspot/cpu/arm/stubGenerator_arm.cpp line 3106:

> 3104:       generate_phase1();
> 3105:     } else {
> 3106:       generate_all();

It might be better to check for phases explicitly:
  
     } else if (phase == 2) {
       generate_all();
     } else {
        ShouldNotReachHere();
     }

src/hotspot/share/runtime/arguments.cpp line 4208:

> 4206: #endif // COMPILER2
> 4207: 
> 4208: 

Unnecessary changes, that bring one more file to diff list. 
Please fix.

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

PR: https://git.openjdk.java.net/jdk/pull/8634