RFR: 8286808: Loom: Simplify generate_cont_thaw by passing thaw_kind directly [v2]

[Robbin Ehn]

On Mon, 16 May 2022 11:29:06 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> I was staring at this code for x86_32 port, and it seems `exception` implies `return_barrier`. This mostly irks me because we are passing `2` to `Continuation::prepare_thaw` and implicitly coercing it to `bool` during the call. We can instead call with `1` when `return_barrier`.
>> 
>> Further cleanup makes the change more obvious; we can pass `thaw_kind` directly to `generate_cont_thaw`, and thus simplify the code. Unused x86_32 and PPC64 stubs are just deleted without refactoring the args; this is supposed to produce a cleaner merge problem for current porting work.
>> 
>> Additional testing:
>>  - [x] `java/lang/Thread/virtual` on Linux x86_64 fastdebug
>>  - [x] `java/lang/Thread/virtual` on Linux AArch64 fastdebug
>>  - [x] Build Linux x86_32
>>  - [x] Build Linux PPC64
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove unused generate_cont_thaw stubs too

Looks good.

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Marked as reviewed by rehn (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/8725