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

[Tobias Hartmann]

On Mon, 22 Feb 2021 15:03:53 GMT, Frederic Parain <fparain at openjdk.org> wrote:

>> 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
>
> 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

Hi Fred,

thanks for looking at this, you are right.

Best regards,
Tobias

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PR: https://git.openjdk.java.net/valhalla/pull/345