8370031: Make RegMask copy constructor explicit and replace RegMask operator= with named function

[dlunde]

Issue Summary

The RegMask copy constructor is currently non-explicit. We should make it explicit so that we do not unintentionally copy register masks.

Additionally, we currently overload operator= in RegMask to do a deep copy. It is preferable to use an explicit named function instead, according to the HotSpot coding style.

Changeset

• Make the RegMask copy constructor explicit.
• Fix compilation errors as a result of the now explicit constructor. Specifically, the methods Matcher::divI_proj_mask, Matcher::modI_proj_mask, Matcher::divL_proj_mask, and Matcher::modL_proj_mask all use implicit copy construction (likely unintended). Change the methods to return const RegMask& instead of RegMask and correspondingly change the return value from RegMask() to RegMask::Empty on some platforms.
• Rename the old method RegMask::copy to RegMask::assignFrom to better describe its functionality, and make it public instead of private.
• Delete RegMask copy assignment (operator=) and change all uses to the named function assignFrom instead.
• Fix various syntax issues at lines touched by the changeset.

Testing

• GitHub Actions
• tier1 to tier4 (and additional Oracle-internal testing) on Windows x64, Linux x64, Linux aarch64, macOS x64, and macOS aarch64.

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8370031: Make RegMask copy constructor explicit and replace RegMask operator= with named function (Enhancement - P4)

Reviewers

• Manuel Hässig (@mhaessig - Committer)
• Roberto Castañeda Lozano (@robcasloz - Reviewer)

Reviewing

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[bridgekeeper]

👋 Welcome back dlunden! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@dlunde 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:

8370031: Make RegMask copy constructor explicit and replace RegMask operator= with named function

Reviewed-by: mhaessig, rcastanedalo

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At the time when this comment was updated there had been 16 new commits pushed to the master branch:

• 2be273f: 8346005: Parallel: Incorrect page size calculation with UseLargePages
• ec13c28: 8366829: Add java.time.Duration constants MIN and MAX
• 430041d: 8367499: Refactor exhaustiveness computation from Flow into a separate class
• ... and 13 more: https://git.openjdk.org/jdk/compare/73923601d8db9032b904cabb18b16a8cb9dd76c1...master

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[openjdk]

@dlunde The following label will be automatically applied to this pull request:

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[mlbridge]

Webrevs

• 01: Full (0c0af8b8)
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[mhaessig]

Thank you for cleaning this up, @dlunde. Your changes look good to me.

[robcasloz]

Looks good, thanks.

[dlunde]

Thanks for the reviews @mhaessig and @robcasloz! Sanity pre-integration tests look good, so integrating now.

/integrate

[openjdk]

Going to push as commit 2af4d20.
Since your change was applied there have been 20 commits pushed to the master branch:

• 517d543: 8370234: Remove CardTableBarrierSet::write_region
• d4c0239: 8370240: [PPC64] jhsdb jstack cannot handle continuation stub
• ea7186a: 8020207: jconsole fails connecting over SSL using service:jmx:rmi://...jndi...
• ... and 17 more: https://git.openjdk.org/jdk/compare/73923601d8db9032b904cabb18b16a8cb9dd76c1...master

Your commit was automatically rebased without conflicts.

[openjdk]

@dlunde Pushed as commit 2af4d20.

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