Integrated: 8353174: Clean up thread register handling after 32-bit x86 removal

[Aleksey Shipilev]

On Mon, 31 Mar 2025 10:19:57 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Various `MacroAssembler` methods have this code to support passing the thread register, and getting it if `noreg` is passed:
> 
> 
>   // determine java_thread register
>   if (!java_thread->is_valid()) {
> #ifdef _LP64
>     java_thread = r15_thread;
> #else
>     java_thread = rdi;
>     get_thread(java_thread);
> #endif // LP64
>   }
> 
> 
> This never happens after 32-bit x86 removal. x86_64 always uses r15_thread. We can clean those up.
> 
> These are also the only major users of `MacroAssembler::get_thread` that we want to remove/rename to avoid falling into traps like [JDK-8353176](https://bugs.openjdk.org/browse/JDK-8353176).
> 
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `all`

This pull request has now been integrated.

Changeset: 6df34c36
Author:    Aleksey Shipilev <shade at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/6df34c361e0d1b6fe90ca97c1aaa56e57a86d12c
Stats:     233 lines in 15 files changed: 16 ins; 98 del; 119 mod

8353174: Clean up thread register handling after 32-bit x86 removal

Reviewed-by: cslucas, kvn, vlivanov

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PR: https://git.openjdk.org/jdk/pull/24323