<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="">+llvm-commits as well<div class=""><br class=""></div><div class=""><div><blockquote type="cite" class=""><div class="">On Jun 3, 2015, at 7:40 PM, Owen Anderson <<a href="mailto:resistor@mac.com" class="">resistor@mac.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><br class=""></div><div class=""><blockquote type="cite" class=""><div class="">On Jun 3, 2015, at 5:52 PM, Chandler Carruth <<a href="mailto:chandlerc@gmail.com" class="">chandlerc@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">Anyone there?<br class=""><br class="">I'm still really unhappy at this going in, I don't think it's necessarily<br class="">the right tradeoff at all.<br class=""><br class=""><br class="">REPOSITORY<br class=""> rL LLVM<br class=""><br class=""><a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__reviews.llvm.org_D10173&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=mQ4LZ2PUj9hpadE3cDHZnIdEwhEBrbAstXeMaFoB9tg&m=heaDUSAuFCv4ke4EIcKpXa8p8X9Etuige-k5ViTEJB0&s=Y-M4xdFnCpIqTU1s9ufucW3P8BRKov-AWxGoVHAtBS4&e=" class="">http://reviews.llvm.org/D10173</a><br class=""><br class="">EMAIL PREFERENCES<br class=""> <a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__reviews.llvm.org_settings_panel_emailpreferences_&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=mQ4LZ2PUj9hpadE3cDHZnIdEwhEBrbAstXeMaFoB9tg&m=heaDUSAuFCv4ke4EIcKpXa8p8X9Etuige-k5ViTEJB0&s=iFYHadoKm5qoaFsoarrkjCFo04z0OPp6K9wOu94UoPg&e=" class="">http://reviews.llvm.org/settings/panel/emailpreferences/</a><br class=""></div></blockquote></div><div class=""><br class=""></div>I replied to the message ~45 minutes after you sent it. I’ve reproduced it below. I’ll add that since then Benny Kramer expressed support for the change on llvm-commits.<div class=""><br class=""></div><div class="">—Owen</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><blockquote type="cite" class=""><blockquote type="cite" class="">On Jun 1, 2015, at 4:15 PM, Chandler Carruth <<a href="mailto:chandlerc@gmail.com" class="">chandlerc@gmail.com</a>> wrote:<br class=""><br class="">Uh, folks, please discuss this more widely before just committing. This is<br class="">a really significant change and has implications you're not really<br class="">addressing at all. Clang is not the only frontend and not the only producer<br class="">of value names. With this change you'll likely cause a significant compile<br class="">time hit for many folks.<br class=""></blockquote><br class="">I would strongly argue that anyone using named Values doesn’t care about compile time, or else they would already have stopped using named Values.<br class=""><br class="">That said, I did some measurements for completeness. I took the same stress IR file and used opt -metarenamer to add names to every value. I measured opt -O2, best result out of five runs for each:<br class=""><br class="">With my patch<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>No names<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>18.852s<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>Names<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>19.453s<br class="">Without my patch<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>No names<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>18.834s<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>Names<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>19.059s<br class=""><br class="">In summary, the performance with names enabled degrades by approximately 2%, meaning that the degradation is approximately 1:1 with the memory savings in the not-advised-if-you-care-about-compile-time case. In the without-names scenario, I would need to do more thorough measurement to be confident that I can even reliably distinguish any change.<br class=""><br class="">—Owen</blockquote><br class=""></div></div></div></blockquote></div><br class=""></div></body></html>