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I think the problem is that when valhalla arrives, we can no longer ensure the array of objects we pass to create such a vector has an all-reference layout; in addition, we don't want to expose the size and layout of reference pointers to Java code. Maybe a
dedicated method in java.util.Arrays is better for this purpose.</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> forax@univ-mlv.fr <forax@univ-mlv.fr><br>
<b>Sent:</b> Thursday, May 8, 2025 10:43 AM<br>
<b>To:</b> Chen Liang <chen.l.liang@oracle.com><br>
<b>Cc:</b> panama-dev <panama-dev@openjdk.org><br>
<b>Subject:</b> [External] : Re: ObjectVector</font>
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<b>From: </b>"Chen Liang" <chen.l.liang@oracle.com><br>
<b>To: </b>"Remi Forax" <forax@univ-mlv.fr>, "panama-dev" <panama-dev@openjdk.org><br>
<b>Sent: </b>Thursday, May 8, 2025 5:37:14 PM<br>
<b>Subject: </b>Re: ObjectVector<br>
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Hi Remi, where do you plan to use such a vector? Reading from an array of references?</div>
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<div>yes, read/write,</div>
<div>as an example, if we have something like ObjectVector, ArrayList.contains(null) can be implemented by reading the array of elements into a vector register and then use eq(null) to get a VectorMask.
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Regards, Chen</div>
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<div>regards,</div>
<div>Rémi</div>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> panama-dev <panama-dev-retn@openjdk.org> on behalf of Remi Forax <forax@univ-mlv.fr><br>
<b>Sent:</b> Thursday, May 8, 2025 10:31 AM<br>
<b>To:</b> panama-dev@openjdk.org <panama-dev@openjdk.org><br>
<b>Subject:</b> ObjectVector</font>
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<div class="x_PlainText">Hello,<br>
in java, unlike in C, references are opaque so a lot of operations on the value of the reference are not allowed,<br>
but some still exist like checking if the value is null or not.<br>
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Is there a way to create an ObjectVector that would only implement those simple operations ?<br>
<br>
Or is it a stupid idea given that both ZGC and shenandoah use read-barrier ?<br>
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regards,<br>
Rémi<br>
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