<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><br><div><div>On Feb 7, 2014, at 3:39 AM, Chandler Carruth <<a href="mailto:chandlerc@gmail.com">chandlerc@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><blockquote class="gmail_quote" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><div id=":542" style="overflow: hidden;">(1) We're forcing a significant analysis to run between passes to make it easier to update SSA after transformation. But we don't even know if any transformations are needed. I would prefer to use SSAUpdater to handle the transformations as they occur. We could save 1-2% of opt time [1].<br></div></blockquote><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br></div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Do you have any measurement of this? I have no evidence that LCSSA is a remotely significant optimization time cost, but I've not gone looking.</div></blockquote><br></div><div>1-2% is the time I measured when I wrote that email. But that doesn’t account for any speedups we might get by being in LCSSA for (I’m speculating that calls to SSAUpdater might be faster).</div><div><br></div><div>I don’t think it’s a problem now, or will ever be for the standard -O2 pipeline. Just saying that an on-demand SSA updater is better if all else is equal.</div><div><br></div><div>-Andy</div></body></html>