<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 Dec 16, 2013, at 4:26 PM, Hal Finkel <<a href="mailto:hfinkel@anl.gov">hfinkel@anl.gov</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><blockquote type="cite" 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;">At the end of each iteration, quality of generated code is estimated<br>by<br>executing newly introduced target dependent pass. Based on results<br>path for<br>the following iteration is calculated. At the moment, this has been<br>proved<br>for MIPS only and it is based on code size.<br></blockquote><br 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;"><span 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; float: none; display: inline !important;">I think that, in general, we ought to be able to get an overall latency estimate from the instruction scheduler.</span></blockquote></div><br><div>This is somewhat tangential to the thread… I think it would be great to have a static performance estimator. I’m thinking of an MI-level library that simulates a loop using the machine model until it settles on an average number of cycles per iteration. A simple tool could handle the most probable path through the loop. It could be extended to handle averaging across a small number of paths if needed. Estimating in-order cycles is easy enough. I also developed simplified model for estimating OOO core cycles—I don’t have working code any more, as it doesn’t serve any purpose in the code base.</div><div><br></div><div>-Andy</div></body></html>