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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D">OK.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D">Then I think the clear choice ought to be to canonicalize to the same sized int representation to account for architectures<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D">whose FP may not exactly match LLVMs assumptions. Even when fp exceptions are masked, X87 load changes bit pattern of SNan to<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D">QNan, so it is going to be generally incorrect to convert an integer load to an FP load, as that won’t properly preserve the all possible bit patterns<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D">of the integer, unless great pains are taken not to use fld instruction to implement FP load, which just seems wrong as well.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D">Kevin Smith<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> chandlerc@google.com [mailto:chandlerc@google.com]
<b>On Behalf Of </b>Chandler Carruth<br>
<b>Sent:</b> Wednesday, January 21, 2015 3:34 PM<br>
<b>To:</b> Smith, Kevin B<br>
<b>Cc:</b> Chandler Carruth; LLVM Developers Mailing List<br>
<b>Subject:</b> Re: [LLVMdev] RFC: Missing canonicalization in LLVM<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Wed, Jan 21, 2015 at 3:06 PM, Smith, Kevin B <<a href="mailto:kevin.b.smith@intel.com" target="_blank">kevin.b.smith@intel.com</a>> wrote:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D">I don’t think these are equivalent representations. The one with the float loads and stores has the
potential of FP exceptions</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D">both during the load and during the store</span><o:p></o:p></p>
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LLVM explicitly doesn't support FP exceptions on loads and stores. And it would break the world to add it.<o:p></o:p></p>
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