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Hi Remi,</div>
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I think this is probably due to these fields being added too early - the stable on string byte array is also added lately.</div>
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That said, I don't think adding stable on both fields completely resolves the constant folding issues around string hash code. The current code can only constant fold non-zero hash; a zero hash is folded to a read to hash field, which cannot fold further because
it's a read of the default value from a stable field.</div>
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A solution may be to change <code>hashIsZero</code> to a byte field indicating 3 states - hash unset (0), hash computed to field, hash computed and is zero. This allows the zero hash to constant fold as well at the cost of non-constant hash access performance,
as now there are two reads.</div>
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Also this reminds me of <a href="https://bugs.openjdk.org/browse/JDK-8332249">https://bugs.openjdk.org/browse/JDK-8332249</a> - maybe Method::hashCode was hot because the string hash code could not fold.</div>
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Regards, Chen</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> core-libs-dev <core-libs-dev-retn@openjdk.org> on behalf of Remi Forax <forax@univ-mlv.fr><br>
<b>Sent:</b> Thursday, April 10, 2025 4:18 AM<br>
<b>To:</b> core-libs-dev <core-libs-dev@openjdk.java.net><br>
<b>Subject:</b> java.lang.String hashCode and @Stable ?</font>
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<div class="PlainText">Question,<br>
why String.hash and String.hashIsZero are not declared @Stable ?<br>
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regards,<br>
Rémi<br>
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