<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="">Hi Sanjay,</div><br class=""><div><blockquote type="cite" class=""><div class="">On Jan 19, 2015, at 4:38 PM, Sanjay Patel <<a href="mailto:spatel@rotateright.com" class="">spatel@rotateright.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="">Are there any LLVM guidelines / documentation for handling larger-than-legal data types (either scalars or vectors)?<br class=""><br class=""></div>Currently, the backend may crash [1], miscompile [2], or make a big mess [3] when presented with data types that are bigger than native. <br class=""><br class="">In the case of [3], is it a bug in the vectorizer to produce a non-legal vector type (<16 x i64>) or should the backend be able to handle that more reasonably? In that particular case, things are further complicated because -loop-unroll is able to completely remove the loop and the large vector type disappears.<br class=""></div></div></blockquote><div><br class=""></div><div>I’d say it is legal for the vectorizer to produce non-legal types as long as the expected codegen cost is smaller than the scalar version. That being said, this is possible there is a bug in the vectorizer cost model or the use of this cost model!</div><div><br class=""></div><div>Cheers,</div><div>-Quentin</div><br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><br class="">[1] <a href="http://llvm.org/bugs/show_bug.cgi?id=19797" class="">http://llvm.org/bugs/show_bug.cgi?id=19797</a><br class="">[2] <a href="http://llvm.org/bugs/show_bug.cgi?id=21184" class="">http://llvm.org/bugs/show_bug.cgi?id=21184</a><br class="">[3] <a href="http://llvm.org/bugs/show_bug.cgi?id=20225" class="">http://llvm.org/bugs/show_bug.cgi?id=20225</a><br class=""></div>
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