RFR: Make Loom buildable on x86_32 [v3]

[Aleksey Shipilev]

On Tue, 5 Oct 2021 10:01:49 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> This PRs make Loom workspace at least buildable on x86_32. 
>> 
>> Since jlink/jmod run build JDK, the JDK itself has to start well, without touching Loom code. Current patch passes `make images` and `tier1` on `x86_32`, with predictable test failures on Loom-specific tests. I shall continue with the actual x86_32 support in another PR. Meanwhile, this PR should make x86_32 builds (e.g. in GHA) and the rest of non-Loom-specific tests happy. This would also protect from introducing more 32-bit uncleanliness in shared code.
>> 
>> Additional testing:
>>  - [x] 10x `CONF=linux-x86-server-fastdebug make clean-images images`
>>  - [x] Linux x86_32 `tier1` passes (with Loom-specific test failures)
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision:
> 
>  - Fix another register clash on x86_32 (rcx is used later as rthread)
>  - Merge branch 'fibers' into basic-x86-32-builds
>  - Merge branch 'fibers' into basic-x86-32-builds
>  - More accurate register saving
>  - More precise post_call_nops
>  - Select the register better
>  - Linux x86_32 builds fine

Any comments? I would like to have it integrated.

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

PR: https://git.openjdk.java.net/loom/pull/65