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Count Instruction Extension - Revision history
2026-05-25T06:04:46Z
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2019-08-29T18:25:48Z
<p>Imported from http://web.archive.org/web/20110529090708/http://www.alphalinux.org/wiki/index.php?title=Count_Instruction_Extension&action=edit</p>
<p><b>New page</b></p><div>Initially implemented in the [[Processors#EV67|EV67]] processor, the Count Instruction Extension adds three instructions to count bits.<br />
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== Added Instructions ==<br />
<br />
{| class="wikitable" style="font-size:97%;"<br />
! Mnemonic<br />
! Description<br />
|-<br />
! ctlz<br />
| Count Leading Zeros<br />
|-<br />
! ctpop<br />
| Count Population (Count number of 1's)<br />
|-<br />
! cttz<br />
| Count Trailing Zeros<br />
|}<br />
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== Determining Presence ==<br />
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To determine the presence of CIX, use the [[amask]] instruction.<br />
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== Latency and Slotting ==<br />
The CIX instructions are slotted U0 and have a latency of 3 cycles. <ref>{{cite web|url=http://h18002.www1.hp.com/alphaserver/technology/literature/cmpwrgd.pdf|title=Compiler Writer’s Guide for the Alpha 21264|year=1999|month=June|format=PDF|publisher=Compaq Computer Corporation|pages=35-38}}</ref>.<br />
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== References ==<br />
<references/><br />
<br />
[[Category:Programming]]</div>
Gareth