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<p class="MsoNormal">> We should also support loading and storing pointer values. <o:p></o:p></p>
<p class="MsoNormal">Does it mean that on vectorizer stage we don’t know size of pointer?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I think that masked load / store / gather / scatter should handle the same data types.<o:p></o:p></p>
<p class="MsoNormal">I’m not against supporting vector of pointers in all intrinsics.<o:p></o:p></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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<![if !supportLists]><span style="font-family:"Calibri","sans-serif";color:#31849B"><span style="mso-list:Ignore">-<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span dir="LTR"></span><b><i><span style="color:#31849B"> Elena<o:p></o:p></span></i></b></p>
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<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""> Demikhovsky, Elena
<br>
<b>Sent:</b> Thursday, December 18, 2014 23:38<br>
<b>To:</b> Nadav Rotem<br>
<b>Cc:</b> llvmdev@cs.uiuc.edu; dag@cray.com; Zaks, Ayal; Khasanov, Robert; Adam Nemet (anemet@apple.com); Hal Finkel (hfinkel@anl.gov); Chandler Carruth (chandlerc@gmail.com); Arnold Schwaighofer<br>
<b>Subject:</b> RE: Indexed Load and Store Intrinsics - proposal<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi Nadav,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><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">It looks like the proposed intrinsic is very specific to the x86 implementation of gather/scatter. Would it be possible to remove the PassThrough value from the intrinsic and define the masked-out value to be undef? You would still be
able to pattern match it if you use a maskedload + select. <o:p></o:p></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">[Demikhovsky, Elena] We have PassThrough value in masked load. We want to be consistent in all intrinsics.</span></i></b><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"><o:p> </o:p></p>
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<p class="MsoNormal">Can we remove the masked version of the intrinsic altogether and pattern match it using the non-masked version somehow?<o:p></o:p></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">[Demikhovsky, Elena] on the contrary, we can remove non-masked and use masked somehow. Using non-masked+select is not safe for gather and meaningless
for scatter. That’s why we added masked load/store intrinsics.</span></i></b><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"><o:p> </o:p></p>
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<p class="MsoNormal">Can we infer the scale value based on the loaded element type?<o:p></o:p></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">[Demikhovsky, Elena]
<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">In this case we need two different intrinsics: one with non-zero base and vector of indices (index is relative to base) and implicit scale based, as you
say, on element type.<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">And the second one without base, without scale, just vector of pointers.<o:p></o:p></span></i></b></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Semantics:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">For i=0,1,…,N-1: if (Mask[i]) {VectorValue[i] = *(BaseAddr + VectorOfIndices[i]*Scale) else VectorValue[i]=PassThruVal[i];}<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">void @llvm.sindex.store (BaseAddr, VectorValue, VectorOfIndices, Scale)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">void @llvm.uindex.store (BaseAddr, VectorValue, VectorOfIndices, Scale)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">void @llvm.sindex.masked.store (BaseAddr, VectorValue, VectorOfIndices, Scale, Mask)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">void @llvm.uindex.masked.store (BaseAddr, VectorValue, VectorOfIndices, Scale, Mask)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Semantics:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">For i=0,1,…,N-1: if (Mask[i]) {*(BaseAddr + VectorOfIndices[i]*Scale) = VectorValue[i];}<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">VectorValue: any float or integer vector type.<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">We should also support loading and storing pointer values. <o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">BaseAddr: a pointer; may be zero if full address is placed in the index.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">VectorOfIndices: a vector of i32 or i64 signed or unsigned integer values.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Scale: a compile time constant 1, 2, 4 or 8.<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">Why do we need to limit the scale values?<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">VectorValue, VectorOfIndices and Mask must have the same vector width.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">An indexed store instruction with complete or partial overlap in memory (i.e., two indices with same or close values) will provide the result equivalent to serial scalar
stores from least to most significant vector elements.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <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">Thanks,<o:p></o:p></p>
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<p class="MsoNormal">Nadav<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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