8258790: C2: Crash on empty macro node list

[iwanowww]

The fix for 8257624 is incomplete: it doesn't cover the case when macro node array becomes empty as a result of multiple nodes removal. In such case, the out-of-bounds access still takes place (at index "-1").

Proposed fix is to adjust the index before performing "i > 0" check.

Testing:

• failing tests
• hs-precheckin-comp, hs-tier1, hs-tier2

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed

Issue

• JDK-8258790: C2: Crash on empty macro node list

Reviewers

• Vladimir Kozlov (@vnkozlov - Reviewer) ⚠️ Review applies to 174e988
• Christian Hagedorn (@chhagedorn - Reviewer)

Download

$ git fetch https://git.openjdk.java.net/jdk16 pull/56/head:pull/56
$ git checkout pull/56

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[openjdk]

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[mlbridge]

Webrevs

• 01: Full - Incremental (b94ba8f)
• 00: Full (174e988)

[openjdk]

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

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

8258790: C2: Crash on empty macro node list

Reviewed-by: kvn, chagedorn

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[chhagedorn]

Looks good to me!

[iwanowww]

Thanks for the reviews, Vladimir and Christian.

[iwanowww]

/integrate

[openjdk]

@iwanowww Pushed as commit 772addf.

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