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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang fails to optimise loop invariant when function accesses class members"
href="https://bugs.llvm.org/show_bug.cgi?id=48038">48038</a>
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<th>Summary</th>
<td>Clang fails to optimise loop invariant when function accesses class members
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<th>Product</th>
<td>new-bugs
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<th>Version</th>
<td>unspecified
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>new bugs
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>robin.christ@gmx.de
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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<pre>Repro is here:
<a href="https://godbolt.org/z/Y8397j">https://godbolt.org/z/Y8397j</a>
Essentially we're seeing a division in every loop iteration for the trivial
HanningWindow::prepare1 case.
If we cache the flow_ and fhigh_ class members (HanningWindow::prepare2), the
invariant gets optimised.
Same if we extract the function (prepareExternal)
prepare1 => .LBB1_2: doesn't get optimised
prepare2 => .LBB2_2: works as expected
prepareExternal => .LBB3_2 works as expected
Any ideas why this happens? Is this something that can be fixed?</pre>
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