<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"><base href="x-msg://10814/"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On Oct 16, 2012, at 1:43 PM, Sergei Larin <<a href="mailto:slarin@codeaurora.org">slarin@codeaurora.org</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div lang="EN-US" link="blue" vlink="purple" style="font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div class="WordSection1" style="page: WordSection1; "><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Andy,<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> This is less of a question but rather a status quo verification…<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> We currently have certain indeterminism in MI scheduler DAG construction – it is introduces by the use of std::map/std::set during edge traversal.<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Result – a random variation in SUnit edge order (which will remain fixed thereafter). Logically, it is the same DAG, but topologically it is a slightly different one, and if some algorithm is dependent on the order of edge traversal, we can have performance and debugging indeterminism. The way I have discovered it – VLIW scheduler can produce identical cost function for a pair of SUs, making visitation order the tie breaker, which is not deterministic per above discussion. For me it is trivial to fix, but I wonder if this might become a source of well hidden issues in the future.<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> I am at this time not proposing anything – a fix is definitely possible, but I wonder what people think about it before I even consider this a bug.</span></div></div></div></blockquote><br></div><div>This looks like a bug. The edge order could even affect some heuristics and influence codegen.</div><div><br></div><div>I don't have a better idea than using SetVector/MapVector for Value* keys. For SUnits we could just key on NodeNum. Go ahead and file a bug and/or submit a patch.</div><div><br></div><div>Thanks!</div><div>-Andy</div></body></html>