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<p class="MsoNormal"><span lang="EN-US">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">For the following loop represented in llvm IR:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">for.body.lr.ph: ; preds = %if.end19<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> %conv23 = zext i8 %conv2 to i32<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> <span style="color:#0070C0">%3 = zext i8 %ucInputNum.addr.0 to i64<o:p></o:p></span></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#0070C0"> %4 = shl i64 %3, 2<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> br label %for.body<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">for.body: ; preds = %for.body, %for.body.lr.ph<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> %lsr.iv = phi i64 [ %lsr.iv.next, %for.body ], [ 0, %for.body.lr.ph ]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> %ulTemp.0101 = phi i32 [ 0, %for.body.lr.ph ], [ %phitmp, %for.body ]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ……<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> %not.cmp39 = xor i1 %cmp39, true<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> %cond48 = zext i1 %not.cmp39 to i32<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> %add49 = add nuw nsw i32 %ulTemp.0101, %cond48<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> <span style="color:red">%phitmp = and i32 %add49, 65535 <------ A</span><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> %lsr.iv.next = add nuw nsw i64 %lsr.iv, 4<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> %tmp = trunc i64 %lsr.iv.next to i32<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> %tmp106 = trunc i64 <span style="color:#0070C0">
%4</span> to i32<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> %exitcond = icmp eq i32 <span style="color:#0070C0">
%tmp106</span>, %tmp<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> br i1 %exitcond, label %for.end, label %for.body<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">for.end:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ……<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The instruction A: <span style="color:red">%phitmp = and i32 %add49, 65535
</span>is redundant and can be removed, because the trip count is at most 10 bits, and %add49 (from 0) is incremented by at most 1 per iteration. That is %add49 is at most 10 bits and there is no need for the 16-bit mask of and operation.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Where and how should this optimization implemented?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thanks.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Best,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Ning<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:8.0pt;font-family:"Akkurat Pro";color:#1F497D"><o:p> </o:p></span></b></p>
<p class="MsoNormal"><b><span lang="EN-US" style="font-size:8.0pt;font-family:"Akkurat Pro";color:#1F497D">Ning Xie<o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span lang="EN-US" style="font-size:8.0pt;font-family:"Akkurat Pro";color:#1F497D"><o:p> </o:p></span></b></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:8.0pt;font-family:"Akkurat Pro Light";color:#7B7B7B">Huawei Canada Research Centre<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:8.0pt;font-family:"Akkurat Pro Light";color:#7B7B7B">O. +1 905-944-5000 ext. 7587<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:8.0pt;font-family:"Akkurat Pro Light";color:#7B7B7B">Email:
</span><a href="mailto:ning.xie@huawei.com"><span lang="EN-US" style="font-size:8.0pt;font-family:"Akkurat Pro Light"">ning.xie@huawei.com</span></a><span lang="EN-US" style="font-size:8.0pt;font-family:"Akkurat Pro Light";color:#7B7B7B">
<o:p></o:p></span></p>
<p class="MsoNormal"><a href="http://www.huawei.ca/"><b><span lang="EN-US" style="font-size:8.0pt;font-family:"Akkurat Pro Light";color:#7B7B7B">www.huawei.ca</span></b></a><b><span lang="EN-US" style="font-size:8.0pt;font-family:"Akkurat Pro Light";color:#7B7B7B"><o:p></o:p></span></b></p>
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<p class="MsoNormal" style="text-align:justify"><span lang="EN-US" style="font-size:6.0pt;font-family:"FrutigerNext LT Regular";color:#C9C9C9"><o:p> </o:p></span></p>
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