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<p class="MsoNormal"><span style="font-family:"Courier New"">> With current API, it seems that if one want to get the lanes with highest bit set, one can use Vector::compare(LT, 0).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">I assume the final goal is to gather the highest bits of each lane to an Integer value, while it’s going to be allocated to a general-purpose register on a certain hardware.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">```<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">long imm = va.compare(LT, 0).toLong();
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">```<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">> In the backend, this seems to be translated to something like vpcmpgtb followed by vpmovmskb. However, Gather the highest bit on x86 only need a movemask operation.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">I’m not familiar with x86. I assume the input of vpmovmskb is a predicate register, while in your case the original input was a Vector object which should be allocated in vector register.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">- Eric<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
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<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b>From:</b> panama-dev <panama-dev-retn@openjdk.org> <b>On Behalf Of
</b>Zhu, Yifan<br>
<b>Sent:</b> Saturday, January 7, 2023 8:01 AM<br>
<b>To:</b> panama-dev@openjdk.org<br>
<b>Subject:</b> [VectorAPI] Expose direct move mask operation?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span class="elementtoproof"><span style="font-size:12.0pt;color:black;background:white">Sorry if this was previously discussed. I am new to the list.</span></span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span class="elementtoproof"><span style="font-size:12.0pt;color:black;background:white">With current API, it seems that if one want to get the lanes with highest bit set, one can use Vector::compare(LT, 0). In the backend, this seems to
be translated to something like vpcmpgtb followed by vpmovmskb. However, Gather the highest bit on x86 only need a movemask operation.
</span></span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<li class="elementtoproof1" style="color:black;mso-list:l2 level1 lfo1"><span class="elementtoproof"><span style="font-size:12.0pt;background:white">I wonder if such operations can be optimized if the given constant is special (such as 0)</span></span><span style="font-size:12.0pt"><o:p></o:p></span></li><li class="elementtoproof1" style="color:black;mso-list:l2 level1 lfo1"><span class="elementtoproof"><span style="font-size:12.0pt;background:white">Or if we can finally have a
</span></span><code><span style="font-size:10.0pt;background:white">gatherBits()</span></code><span class="elementtoproof"><span style="font-size:12.0pt;background:white"> operation. I know that movemask operations are not available on platforms like aarch64,
but libraries like SIMDE has given some examples on how to emulate these operations on other platforms.</span></span><span style="font-size:12.0pt"><o:p></o:p></span></li></ul>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><img width="119" height="29" style="width:1.2361in;height:.3055in" id="Picture_x0020_1" src="cid:image001.png@01D932FF.02C9D010"></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;font-family:"Calibri Light",sans-serif;color:black">Schrodinger ZHU Yifan, Ph.D. Student</span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;font-family:"Calibri Light",sans-serif;color:black">Computer Science Department, University of Rochester</span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><b><span style="font-size:10.0pt;font-family:"Calibri Light",sans-serif;color:black">Personal Email:</span></b><span style="font-size:10.0pt;font-family:"Calibri Light",sans-serif;color:black">
<a href="mailto:i@zhuyi.fan">i@zhuyi.fan</a></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><b><span style="font-size:10.0pt;font-family:"Calibri Light",sans-serif;color:black">Work Email:</span></b><span style="font-size:10.0pt;font-family:"Calibri Light",sans-serif;color:black">
<a href="mailto:yifanzhu@rochester.edu">yifanzhu@rochester.edu</a></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><b><span style="font-size:10.0pt;font-family:"Calibri Light",sans-serif;color:black">Website:</span></b><span style="font-size:10.0pt;font-family:"Calibri Light",sans-serif;color:black">
<a href="https://www.cs.rochester.edu/~yzhu104/Main.html">https://www.cs.rochester.edu/~yzhu104/Main.html</a></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><b><span style="font-size:10.0pt;font-family:"Calibri Light",sans-serif;color:black">Github:</span></b><span style="font-size:10.0pt;font-family:"Calibri Light",sans-serif;color:black"> SchrodingerZhu</span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><b><span style="font-size:10.0pt;font-family:"Calibri Light",sans-serif;color:black">GPG Fingerprint:</span></b><span style="font-size:10.0pt;font-family:"Calibri Light",sans-serif;color:black"> BA02CBEB8CB5D8181E9368304D2CC545A78DBCC3</span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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