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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The canonical way to do it would be to load into a scalar, and then broadcast the scalar using a shufflevector.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hopefully, the backend will be smart enough to match this as a single load+broadcast, if the platform has such an instruction.<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">(The trick you’re suggesting with getelementptr will probably possible soon, now that gather intrinsics are being introduced, but it probably will create worse
code, not better.)<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">Michael<o:p></o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></a></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""> llvmdev-bounces@cs.uiuc.edu [mailto:llvmdev-bounces@cs.uiuc.edu]
<b>On Behalf Of </b>zhi chen<br>
<b>Sent:</b> Monday, May 04, 2015 10:59<br>
<b>To:</b> LLVM Dev<br>
<b>Subject:</b> [LLVMdev] Load value and broadcast in LLVM<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="line-height:115%">Is it possible to load a value into a vector register and broadcast it in LLVM?<o:p></o:p></p>
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<p class="MsoNormal" style="line-height:115%"><o:p> </o:p></p>
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<p class="MsoNormal" style="line-height:115%">For example, for the following address %x<o:p></o:p></p>
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<p class="MsoNormal" style="line-height:115%"><o:p> </o:p></p>
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<p class="MsoNormal" style="line-height:115%"> %x = getelementptr inbounds %struct._Ray* %ray, i32 0, i32 0, i32 0<o:p></o:p></p>
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<p class="MsoNormal" style="line-height:115%"><o:p> </o:p></p>
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<p class="MsoNormal" style="line-height:115%">instead of loading the value at %x into a scalar register %0:<o:p></o:p></p>
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<p class="MsoNormal" style="line-height:115%">%0 = load double* %x, align 4, !tbaa !0<o:p></o:p></p>
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<p class="MsoNormal" style="line-height:115%"><o:p> </o:p></p>
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<p class="MsoNormal" style="line-height:115%">I want to load it into a <2 x double> vector register %1 and make both of the two elements in %1 be the value at %x.<o:p></o:p></p>
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<p class="MsoNormal" style="line-height:115%"><o:p> </o:p></p>
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<p class="MsoNormal" style="line-height:115%">I guess one way to do this is to make getelementptr return a <2 x i32>* address, where the two addresses in <2 X 32> are the same. But I don't know if it is possible to do this in LLVM. <o:p></o:p></p>
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<p class="MsoNormal" style="line-height:115%"><o:p> </o:p></p>
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<p class="MsoNormal" style="line-height:115%">Any help would be appreciated.<o:p></o:p></p>
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<p class="MsoNormal" style="line-height:115%"><o:p> </o:p></p>
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<p class="MsoNormal" style="line-height:115%">Best,<o:p></o:p></p>
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<p class="MsoNormal" style="line-height:115%">Zhi<o:p></o:p></p>
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<p class="MsoNormal" style="line-height:115%"><o:p> </o:p></p>
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