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

[shipilev]

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.

Additional testing:

• Linux x86_64 server fastdebug, all

---

Progress

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Issue

• JDK-8353174: Clean up thread register handling after 32-bit x86 removal (Sub-task - P4)

Reviewers

• Cesar Soares Lucas (@JohnTortugo - Author)
• Vladimir Kozlov (@vnkozlov - Reviewer)
• Vladimir Ivanov (@iwanowww - Reviewer)

Reviewing

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[openjdk]

@shipilev This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

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

Reviewed-by: cslucas, kvn, vlivanov

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At the time when this comment was updated there had been 25 new commits pushed to the master branch:

• b4ab964: 8353218: Shenandoah: Out of date comment references Brooks pointers
• 63fa255: 8354061: Update copyright in NameFormat.java fix after JDK-8349890
• 5b42c46: 8353757: Log class should have a proper clear() method
• ... and 22 more: https://git.openjdk.org/jdk/compare/9844c1c52b9b7b6959d4e5cc626495c83f4aa9d4...master

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[mlbridge]

Webrevs

• 00: Full (02e29a7f)

[JohnTortugo]

LGTM

[vnkozlov]

Good.

[iwanowww]

Looks good.

[shipilev]

Thanks all! I have re-merged with master locally, and there are no evident problems. So I am integrating.

/integrate

[openjdk]

Going to push as commit 6df34c3.
Since your change was applied there have been 34 commits pushed to the master branch:

• 0f70aae: 8353841: [jittester] Fix JITTester build after asm removal
• 3340e13: 8352994: ZGC: Fix regression introduced in JDK-8350572
• b045e3f: 8352681: C2 compilation hits asserts "must set the initial type just once"
• ... and 31 more: https://git.openjdk.org/jdk/compare/9844c1c52b9b7b6959d4e5cc626495c83f4aa9d4...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 6df34c3.

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