<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div><br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class="">All of my measurements indicate that it is actually more than one cycle in practice. =/ It is actually a huge hit on AMD chips, and even on Intel, I've seen code that really fluctuated its performance around this.</div></div></div></div></div></blockquote><div><br class=""></div><div>Darnit, I had almost escaped the “having to care about performance on AMD” train ;-)</div><br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class=""><br class=""></div><div class="">The other reason I'm not worried about it is that xorps X, X should only take up space in the decode buffer, etc. the register renamer and such handles those AFAICT with essentially zero execution cost.</div><div class=""> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> that doesn’t really feel worth it at all. Plus I’m not even sure those particular instructions have that delay (it’s only specific combinations, I think…?)<br class=""></blockquote><div class=""><br class=""></div><div class="">That may well be true. I would certainly hope that they get decoded to something less crazy.</div><div class=""> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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It’s not my fault x86 has weirdly non-orthogonal vector instructions ;-)</blockquote></div><br class="">;] But without them, the vector shuffle lowering wouldn't be *nearly* so much fun.</div></div>
</div></blockquote></div><br class=""><div class="">Heehee, indeed. Anyways, I think this is getting slightly off-topic from the original thread!</div><div class=""><br class=""></div><div class="">Fiona</div></body></html>