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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I have no opinion on whether it is "worth" working on fixed-point. I'm not aware of any discussion or effort in that direction, aside from the email discussions
you already found.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Non-saturating fixed-point can readily be handled using existing LLVM integer types and tracking the scale factor in the front-end. Languages that support
these types (PL/I, COBOL) have done that pretty successfully in other compilers I've worked with. There's no real need for new types to handle these cases.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">It's the saturating operations that are the problem, and my recollection (reinforced by your links, thanks!) is that inventing new types would be a real problem
for people. You are probably best off implementing saturating operations with new LLVM intrinsics, which would (correctly) be avoided by optimization passes, unless you chose to teach a particular pass about the new intrinsics. If this works out, and saturating
fixed-point is demonstrably useful and successful, then it would be time to talk about adding new IR types and instructions.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--paulr<o:p></o:p></span></p>
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<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""> llvm-dev [mailto:llvm-dev-bounces@lists.llvm.org]
<b>On Behalf Of </b>Fabio Gritti via llvm-dev<br>
<b>Sent:</b> Tuesday, November 10, 2015 1:54 PM<br>
<b>To:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> [llvm-dev] FIXED POINT NOTATION<o:p></o:p></span></p>
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<p class="MsoNormal">Hi, we are trying to implement in the LLVM framework the fixed point notation as specified in the ISO/IEC TR 18037 (<a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1169.pdf">http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1169.pdf</a>
).<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">We've read some old discussions on the mailing list ( f.i. <a href="http://lists.cs.uiuc.edu/pipermail/llvmdev/2010-November/036674.html">
http://lists.cs.uiuc.edu/pipermail/llvmdev/2010-November/036674.html</a> , <a href="http://lists.llvm.org/pipermail/llvm-dev/2013-December/068473.html">
http://lists.llvm.org/pipermail/llvm-dev/2013-December/068473.html</a> ), and it seems that some people don't agree on their implementation as a completely new type. <o:p></o:p></p>
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<p class="MsoNormal">Do you think that today it is worth to implement them or not? Are there anybody working on this? <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">If nobody is already working on this, and the dev community think that it can be a good idea we have a couple of questions: <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">1- we are following this main guidelines ( <a href="http://llvm.org/docs/ExtendingLLVM.html">
http://llvm.org/docs/ExtendingLLVM.html</a> ) in order to add a new type, do you think that it's better a fundamental type or a derived one? <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">2- Do you have any advice or additional tutorial to suggest in order to implement a new data type?<o:p></o:p></p>
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<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">Thank you very much <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Best regards<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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