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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">You may need implement these two functions in your runtime environment<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">'__gnu_f2h_ieee' and '__gnu_h2f_ieee'</span><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"><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""> llvmdev-bounces@cs.uiuc.edu [mailto:llvmdev-bounces@cs.uiuc.edu]
<b>On Behalf Of </b>yalong@multicorewareinc.com<br>
<b>Sent:</b> Friday, July 11, 2014 6:49 AM<br>
<b>To:</b> Andrea Di Biagio; Matt Arsenault<br>
<b>Cc:</b> llvmdev<br>
<b>Subject:</b> Re: [LLVMdev] Help!!!!Help!!!! " LLVM ERROR: Cannot select: 0x9fc9680: i32 = fp32_to_fp16 0x9fc0750 [ID=16] " problem!!!!!!!!!!!!!!!!!!<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">Hi Andrea<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"> Thank you your replying.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"> I do like your letter. Add following to line to <span style="background:white">MipsISelLowering.cpp. As your words, @llvm.convert.to.fp16 can compile
successfully. However, the runtime is not right.</span><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">+ setOperationAction(ISD::FP16_TO_FP32, MVT::f32, Expand);<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">+ setOperationAction(ISD::FP32_TO_FP16, MVT::i32, Expand);<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">Robin<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif";color:black"><a href="mailto:yalong@multicorewareinc.com">yalong@multicorewareinc.com</a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:#EFEFEF"><b><span style="font-size:9.0pt;font-family:"Tahoma","sans-serif";color:black">From:</span></b><span style="font-size:9.0pt;font-family:"Tahoma","sans-serif";color:black"> <a href="mailto:andrea.dibiagio@gmail.com">Andrea
Di Biagio</a><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:#EFEFEF"><b><span style="font-size:9.0pt;font-family:"Tahoma","sans-serif";color:black">Date:</span></b><span style="font-size:9.0pt;font-family:"Tahoma","sans-serif";color:black"> 2014-07-09 14:20<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:#EFEFEF"><b><span style="font-size:9.0pt;font-family:"Tahoma","sans-serif";color:black">To:</span></b><span style="font-size:9.0pt;font-family:"Tahoma","sans-serif";color:black"> <a href="mailto:Matthew.Arsenault@amd.com">Matt
Arsenault</a><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:#EFEFEF"><b><span style="font-size:9.0pt;font-family:"Tahoma","sans-serif";color:black">CC:</span></b><span style="font-size:9.0pt;font-family:"Tahoma","sans-serif";color:black"> <a href="mailto:yalong@multicorewareinc.com">yalong@multicorewareinc.com</a>;
<a href="mailto:kevinqindev@gmail.com">Kevin Qin</a>; <a href="mailto:llvmdev@cs.uiuc.edu">
llvmdev</a><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:#EFEFEF"><b><span style="font-size:9.0pt;font-family:"Tahoma","sans-serif";color:black">Subject:</span></b><span style="font-size:9.0pt;font-family:"Tahoma","sans-serif";color:black"> Re: [LLVMdev] Help!!!!Help!!!! " LLVM
ERROR: Cannot select: 0x9fc9680: i32 = fp32_to_fp16 0x9fc0750 [ID=16] " problem!!!!!!!!!!!!!!!!!!<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">Not sure if this can help, but<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">if you really really want to have minimal half float support on Mips,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">then one thing you could try to do is to hack MipsISelLowering.cpp<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">adding rules to expand float-half conversion SDNodes into library<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">calls.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">+ setOperationAction(ISD::FP16_TO_FP32, MVT::f32, Expand);<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">+ setOperationAction(ISD::FP32_TO_FP16, MVT::i32, Expand);<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">(The MVT::i32 on the second rule is required because type i16 is<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">promoted to i32).<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">If you then convert every occurrence of 'fptrunc' from float to half<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">with calls to @llvm.convert.to.fp16, then you should be able to<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">compile (hopefully) with no errors.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">That means, in your original example you would convert the following<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">IR statement:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"> %Vt3_1 = fptrunc float %Vt_2 to half<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">into<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"> %Vt3_1 = call i16 @llvm.convert.to.fp16(float %Vt_2)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">The downside is that you will have to add definitions for<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">'__gnu_f2h_ieee' and '__gnu_h2f_ieee' in the compiler runtime. That is<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">because the backend will expand all the float-half conversions into<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">library calls...<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">This workaround should work assuming that a) you can hack the backend,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">and b) it is acceptable (i.e. a reasonable solution in your case) to<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">have a library call for every float-half conversion in your code.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">On Wed, Jul 9, 2014 at 8:51 PM, Matt Arsenault<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"><<a href="mailto:Matthew.Arsenault@amd.com">Matthew.Arsenault@amd.com</a>> wrote:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">> I think that support for the half type is only implemented for ARM. Last I<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">> tried to use it, I found that none of it works even on x86, and the current<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">> handling of the half conversion SDNodes seem to rely on ARM specific<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">> assumptions<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">Just for the record,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">since revision 212293 (committed only five days ago), the x86 backend<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">supports float half conversions.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">On x86, if the target has F16C, there are ISel patterns to map<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">float-half conversions to specific instructions. If there is no F16C<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">support, then the backend expands float-half conversions into runtime<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">library calls.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">Cheers,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Segoe UI","sans-serif";color:black">Andrea<o:p></o:p></span></p>
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