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8262128: [lworld] C1's ValueNumbering optimization does not correctly handle delayed accesses #345

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@TobiHartmann TobiHartmann commented Feb 22, 2021

C1's ValueNumbering optimization replaces an array+field load array[0].intArray by another non-equivalent array+field load array[0].floatArray because it does not handle delayed accesses. The hash value of LoadIndexed needs to take delayed accesses into account.

Best regards,
Tobias


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  • Change must not contain extraneous whitespace

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  • JDK-8262128: [lworld] C1's ValueNumbering optimization does not correctly handle delayed accesses

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$ git fetch https://git.openjdk.java.net/valhalla pull/345/head:pull/345
$ git checkout pull/345

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@bridgekeeper bridgekeeper bot commented Feb 22, 2021

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

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@openjdk openjdk bot commented Feb 22, 2021

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

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

8262128: [lworld] C1's ValueNumbering optimization does not correctly handle delayed accesses

Reviewed-by: fparain

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@mlbridge mlbridge bot commented Feb 22, 2021

Webrevs

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@fparain fparain commented Feb 22, 2021

Hi Tobias,

Thank you for fixing this.
However, the fix seems to have an issue. The hash_inline_access() method encapsulates the additional offset from the delayed access into a hash value, this encapsulation prevents the is_equal(Value v) method (from the the HASHING macro) to see all individual arguments of the hash function and could cause the method return an incorrect result.

Fred

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@TobiHartmann TobiHartmann commented Feb 22, 2021

Hi Fred,

thanks for looking at this, you are right.

Best regards,
Tobias

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@TobiHartmann TobiHartmann commented Feb 22, 2021

As we've discussed offline, I've disabled ValueNumbering for delayed accesses for now and filed https://bugs.openjdk.java.net/browse/JDK-8262136 to re-enable it later.

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@fparain fparain left a comment

Looks good to me.

Fred

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@TobiHartmann TobiHartmann commented Feb 23, 2021

Thanks, Fred!

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@TobiHartmann TobiHartmann commented Feb 23, 2021

/integrate

@openjdk openjdk bot closed this Feb 23, 2021
@openjdk openjdk bot added integrated and removed ready rfr labels Feb 23, 2021
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@openjdk openjdk bot commented Feb 23, 2021

@TobiHartmann Pushed as commit 1c9a7a9.

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

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