8282414: x86: Enhance the assembler to generate more compact instructions

[merykitty]

Hi, this patch enhances the x86 assembler to emit more compact code for some popular instructions.

For common arithmetic instructions against immediates, if the immediate requires more than 1 byte to encode, we can still shave off 1 byte if the register operand is rax.

For test instruction, since the operation does not write the result, we can downgrade a long to an int and an int to a byte instruction if the immediate is positive and encodable using a smaller amount of bytes.

Thank you very much.

---

Progress

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Issue

• JDK-8282414: x86: Enhance the assembler to generate more compact instructions

Reviewers

• Tobias Hartmann (@TobiHartmann - Reviewer)
• Sandhya Viswanathan (@sviswa7 - Reviewer)

Reviewing

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Update a local copy of the PR:
$ git checkout pull/7628
$ git pull https://git.openjdk.java.net/jdk pull/7628/head

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Checkout this PR locally:
$ git pr checkout 7628

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https://git.openjdk.java.net/jdk/pull/7628.diff

[bridgekeeper]

👋 Welcome back merykitty! 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]

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

• hotspot-compiler

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[mlbridge]

Webrevs

• 03: Full - Incremental (1bdc273b)
• 02: Full - Incremental (d9db9b8f)
• 01: Full - Incremental (2c6dc08e)
• 00: Full (05a0e707)

[TobiHartmann]

Looks reasonable to me and all tests pass. @sviswa7 could you have a look at this as well?

[TobiHartmann]

/reviewers 2

[openjdk]

@merykitty 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:

8282414: x86: Enhance the assembler to generate more compact instructions

Reviewed-by: thartmann, sviswanathan

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 235 new commits pushed to the master branch:

• 1465ea9: 8282355: compiler/arguments/TestCodeEntryAlignment.java failed "guarantee(sect->end() <= tend) failed: sanity"
• ac06bdb: 8282507: Add a separate license file for hsdis
• 32f8437: 8283075: Bad IllegalArgumentException message for out of range rank from ClassDesc.arrayType(int)
• 12dca36: 8283189: Bad copyright header in UnsafeCopyMemory.java
• 05a83e0: 8283124: Add constant for tau to Math and StrictMath
• 671b6ef: 8283143: Use minimal-length literals to initialize PI and E constants
• f43ffe2: 8282633: jarsigner output does not explain why an EC key is disabled if its curve has been disabled
• 4de7201: 8283122: [AIX, s390] UnsafeCopyMemory 'Mismatched' Tests Fail on Big Endian Systems
• 2cddf3f: 8282887: Potential memory leak in sun.util.locale.provider.HostLocaleProviderAdapterImpl.getNumberPattern() on Windows
• 710653c: 8254786: java/net/httpclient/CancelRequestTest.java failing intermittently
• ... and 225 more: https://git.openjdk.java.net/jdk/compare/d7f31d0d53bfec627edc83ceb75fc6202891e186...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@TobiHartmann, @sviswa7) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

[openjdk]

@TobiHartmann
The number of required reviews for this PR is now set to 2 (with at least 1 of role reviewers).

[sviswa7]

Looks good to me.

[merykitty]

Thank you very much for the testings and reviews.
/integrate

[openjdk]

@merykitty
Your change (at version 1bdc273) is now ready to be sponsored by a Committer.

[sviswa7]

/sponsor

[openjdk]

Going to push as commit bacfaa3.
Since your change was applied there have been 235 commits pushed to the master branch:

• 1465ea9: 8282355: compiler/arguments/TestCodeEntryAlignment.java failed "guarantee(sect->end() <= tend) failed: sanity"
• ac06bdb: 8282507: Add a separate license file for hsdis
• 32f8437: 8283075: Bad IllegalArgumentException message for out of range rank from ClassDesc.arrayType(int)
• 12dca36: 8283189: Bad copyright header in UnsafeCopyMemory.java
• 05a83e0: 8283124: Add constant for tau to Math and StrictMath
• 671b6ef: 8283143: Use minimal-length literals to initialize PI and E constants
• f43ffe2: 8282633: jarsigner output does not explain why an EC key is disabled if its curve has been disabled
• 4de7201: 8283122: [AIX, s390] UnsafeCopyMemory 'Mismatched' Tests Fail on Big Endian Systems
• 2cddf3f: 8282887: Potential memory leak in sun.util.locale.provider.HostLocaleProviderAdapterImpl.getNumberPattern() on Windows
• 710653c: 8254786: java/net/httpclient/CancelRequestTest.java failing intermittently
• ... and 225 more: https://git.openjdk.java.net/jdk/compare/d7f31d0d53bfec627edc83ceb75fc6202891e186...master

Your commit was automatically rebased without conflicts.

[openjdk]

@sviswa7 @merykitty Pushed as commit bacfaa3.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.