
<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 class="">LLVM has multiple intermediate representations. Before register allocation llvm IR is translated into the representation most often called machine IR (MIR) which is in strict SSA form for some passes but is then lowered to non SSA form in the PHIElimination and TwoAddressInstruction passes.</div><div class=""><br class=""></div><div class="">- Matthias</div><br class=""><div><blockquote type="cite" class=""><div class="">On Sep 3, 2015, at 10:45 AM, Natanael Ramos via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Hello to all LLVM Developers.<br class=""><br class=""></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">The LLVM IR is in strict SSA form (i.e. every variable is defined before it is used along every path from the entry to exit point)?<div id="gt-src-p" class=""><span id="result_box" class="" lang="en"><span class="">According to the</span> <span class="">documentation</span><span class="">,</span> <span class="">currently the</span> <span class="">LLVM</span> <span class="">IR</span> <span class="">is</span> <span class="">in the</span> <span class="">SSA</span><span class=""> form, but I don't see</span> additional <span class="">information</span> <span class="">about <b class="">strict</b> SSA form</span><span class="">.<br class=""><br class=""></span></span></div><div id="gt-src-p" class=""><span id="result_box" class="" lang="en"><span class="">The strict SSA form provide opportunities of optimization in register allocation, because is proved that all interference graphs of the IR in <b class="">strict</b> SSA form are chordal and</span></span><span id="result_box" class="" lang="en"><span class=""> for those</span><span class="">, there are</span> <span class="">polynomial algorithms</span> <span class="">for the</span> <span class="">graph coloring</span><span class=""> (<a href="http://web.cs.ucla.edu/~palsberg/paper/aplas05.pdf" class="">http://web.cs.ucla.edu/~palsberg/paper/aplas05.pdf</a>).</span></span><span id="result_box" class="" lang="en"><span class=""></span></span></div></div><br class="">-- <br class=""><div class="gmail_signature">Natanael Ramos <br class="">Membro do corpo discente de Ciência da Computação pelo Instituto Federal de <br class="">Minas Gerais - Campus Formiga<br class=""><br class=""></div>

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