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Hello Ashutosh,</div>
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Thank you for the answer, however, the "compute" function is intended to be compiled in a library, so it cannot be inlined. As you said, it's weird that the first loop vectorizes without the "cannot identify array bounds" problem, which makes us think that
it's a bug. We have already written more complex code that vectorizes, thus showing us the potential of the auto-vectorizer, which we really need for our project.</div>
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Regards,</div>
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Emmanouil<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>Από:</b> Nema, Ashutosh <Ashutosh.Nema@amd.com><br>
<b>Στάλθηκε:</b> Δευτέρα, 26 Αυγούστου 2019 7:53 πμ<br>
<b>Προς:</b> manolis mi <manolismih@windowslive.com><br>
<b>Κοιν.:</b> Stephan Hageboeck <stephan.hageboeck@cern.ch>; llvm-dev <llvm-dev@lists.llvm.org><br>
<b>Θέμα:</b> RE: Vectorization fails when dealing with a lot of for loops.</font>
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<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri",sans-serif">Hi
</span><span style="font-family:"Calibri",sans-serif; color:black">Emmanouil,</span></p>
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<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">Seems like when you comment out a loop in “compute” function, it gets inlined, this helps LV by finding the bounds and vectorizes it.</span></p>
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<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">With the presence of all the loops LAA is not able to identify the bounds for the accesses:</span></p>
<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">LAA: Can't find bounds for ptr: %arrayidx.i159 = getelementptr inbounds double, double* %30, i64 %and.i158, !dbg !46</span></p>
<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">LAA: Can't find bounds for ptr: %arrayidx.i155 = getelementptr inbounds double, double* %36, i64 %and.i154, !dbg !66</span></p>
<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">LAA: Can't find bounds for ptr: %arrayidx.i151 = getelementptr inbounds double, double* %42, i64 %and.i150, !dbg !91</span></p>
<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">Its bit strange as its able to identify the bounds correctly for the first loop.</span></p>
<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black"> </span></p>
<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">Without commenting the loop, if you make the “compute” function inline, it gets vectorize:</span></p>
<p class="x_MsoNormal" style="text-indent:.5in"><span style="font-family:"Calibri",sans-serif; color:black">- void compute( size_t batchSize,</span></p>
<p class="x_MsoNormal" style="text-indent:.5in"><span style="font-family:"Calibri",sans-serif; color:black">+ void inline compute( size_t batchSize,</span></p>
<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black"> </span></p>
<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">Regards,</span></p>
<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">Ashutosh</span></p>
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<p class="x_MsoNormal"><b><span style="font-size:11.0pt; font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt; font-family:"Calibri",sans-serif"> llvm-dev <llvm-dev-bounces@lists.llvm.org>
<b>On Behalf Of </b>manolis mi via llvm-dev<br>
<b>Sent:</b> Friday, August 23, 2019 9:13 PM<br>
<b>To:</b> via llvm-dev <llvm-dev@lists.llvm.org><br>
<b>Cc:</b> Stephan Hageboeck <stephan.hageboeck@cern.ch><br>
<b>Subject:</b> [llvm-dev] Vectorization fails when dealing with a lot of for loops.</span></p>
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<p class="x_MsoNormal">[CAUTION: External Email] </p>
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<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">Hello, could you please have a look at this code posted on godbolt.org:</span></p>
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<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black"><a href="https://godbolt.org/z/O-O-Q7">https://godbolt.org/z/O-O-Q7</a></span></p>
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<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">The problem is that inside the compute function, only the first loop vectorizes while the rest copies of it don't. But if I remove any of the for loops, then the rest vectorize
successfully. Could you please confirm that this is a bug, otherwise give me more insight on why the vectorization fails? The message "Cannot identify array bounds" is not helpful.</span></p>
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<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">Thank you for your time,</span></p>
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<p class="x_MsoNormal"><span style="font-family:"Calibri",sans-serif; color:black">Emmanouil Michalainas, CERN</span></p>
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