<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Tue, Dec 8, 2015 at 11:18 AM, Richard Smith <span dir="ltr"><<a href="mailto:richard@metafoo.co.uk" target="_blank">richard@metafoo.co.uk</a>></span> wrote:<br><blockquote class="gmail_quote" style="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 dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class="">On Tue, Dec 8, 2015 at 10:59 AM, Robinson, Paul <span dir="ltr"><<a href="mailto:Paul_Robinson@playstation.sony.com" target="_blank">Paul_Robinson@playstation.sony.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">





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<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Okay, I'll bite:  so what *does* UINT128_MAX actually convert to?</span></p></div></div></blockquote><div><br></div></span><div>$ echo 'unsigned __int128 max = -1; float f = max;' | ~/clang-8/build/bin/clang -x c++ - -emit-llvm -S -o - -O3 | grep @f</div><div>@f = global float undef, align 4</div></div></div></div></blockquote><div><br></div><div>And at runtime, on some targets, we use this:</div><div><br></div><div>  <a href="https://llvm.org/svn/llvm-project/compiler-rt/trunk/lib/builtins/floatuntisf.c">https://llvm.org/svn/llvm-project/compiler-rt/trunk/lib/builtins/floatuntisf.c</a><br></div><div><br></div><div>... which gives a NaN in this case.</div><div><br></div><blockquote class="gmail_quote" style="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 dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class=""><blockquote class="gmail_quote" style="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 lang="EN-US" link="blue" vlink="purple"><div>
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<p class="MsoNormal"><b><span style="font-size:10pt;font-family:Tahoma,sans-serif">From:</span></b><span style="font-size:10pt;font-family:Tahoma,sans-serif"> cfe-commits [mailto:<a href="mailto:cfe-commits-bounces@lists.llvm.org" target="_blank">cfe-commits-bounces@lists.llvm.org</a>]
<b>On Behalf Of </b>Richard Smith via cfe-commits<br>
<b>Sent:</b> Tuesday, December 08, 2015 10:52 AM<br>
<b>To:</b> Joerg Sonnenberger; cfe-commits<br>
<b>Subject:</b> Re: r254574 - PR17381: Treat undefined behavior during expression evaluation as an unmodeled<u></u><u></u></span></p>
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<p class="MsoNormal">On Tue, Dec 8, 2015 at 2:13 AM, Joerg Sonnenberger via cfe-commits <<a href="mailto:cfe-commits@lists.llvm.org" target="_blank">cfe-commits@lists.llvm.org</a>> wrote:<u></u><u></u></p>
<p class="MsoNormal">On Mon, Dec 07, 2015 at 01:32:14PM -0800, Richard Smith via cfe-commits wrote:<br>
> C11 <a href="http://6.3.1.5/1" target="_blank">6.3.1.5/1</a>: "If the value being converted is outside the range of values<br>
> that can be represented, the behavior is undefined."<br>
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The value of 1e100 can be represented as +inf, even if not precisely.<u></u><u></u></p>
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<p class="MsoNormal">Only if +inf is in the range of representable values, which, as already noted, is problematic.<u></u><u></u></p>
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<p class="MsoNormal">This is a bit different from non-IEEE math like VAX, that doesn't have<br>
infinities.<u></u><u></u></p>
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Joerg<br>
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