8357981: [PPC64] Remove old instructions from VM_Version::determine_features()

[TheRealMDoerr]

Simple cleanup after JDK-8331859. The old instructions are always available and don't need to be tried in VM_Version::determine_features().

On Power10:

--------------------------------------------------------------------------------
Decoding cpu-feature detection stub at 0x000079b9203c0380 after execution:
--------------------------------------------------------------------------------
  0x000079b9203c0380:   darn    r7,1
  0x000079b9203c0384:   brw     r5,r6
  0x000079b9203c0388:   blr     bo=0b10100,bh=0b00[subroutine_return]
  0x000079b9203c038c:   dcbz    0,r3
  0x000079b9203c0390:   blr     bo=0b10100,bh=0b00[subroutine_return]

Also tested on older processors: On Power9, brw gets zeroed out. On Power8, darn also gets zeroed out.

---

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Issue

• JDK-8357981: [PPC64] Remove old instructions from VM_Version::determine_features() (Sub-task - P4)

Reviewers

• David Briemann (@dbriemann - Author)
• Matthias Baesken (@MBaesken - Reviewer)

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[openjdk]

@TheRealMDoerr 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:

8357981: [PPC64] Remove old instructions from VM_Version::determine_features()

Reviewed-by: dbriemann, mbaesken

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At the time when this comment was updated there had been 86 new commits pushed to the master branch:

• eb9badd: 8358169: Shenandoah/JVMCI: Export GC state constants
• a9e7a74: 8357109: Parallel: Fix typo in YoungedGeneration
• ba9f44c: 8357793: [PPC64] VM crashes with -XX:-UseSIGTRAP -XX:-ImplicitNullChecks
• ... and 83 more: https://git.openjdk.org/jdk/compare/c9e6c4d0171ff6f419344f9341747c71416d4ec9...master

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[mlbridge]

Webrevs

• 00: Full (9d86e495)

[dbriemann]

LGTM, Thank you!

[TheRealMDoerr]

Thanks for the reviews!
/integrate

[openjdk]

Going to push as commit 612f2c0.
Since your change was applied there have been 86 commits pushed to the master branch:

• eb9badd: 8358169: Shenandoah/JVMCI: Export GC state constants
• a9e7a74: 8357109: Parallel: Fix typo in YoungedGeneration
• ba9f44c: 8357793: [PPC64] VM crashes with -XX:-UseSIGTRAP -XX:-ImplicitNullChecks
• ... and 83 more: https://git.openjdk.org/jdk/compare/c9e6c4d0171ff6f419344f9341747c71416d4ec9...master

Your commit was automatically rebased without conflicts.

[openjdk]

@TheRealMDoerr Pushed as commit 612f2c0.

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