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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [X86] Should we use ExeDepsFix to optimize unused input to gather instructions?"
href="https://bugs.llvm.org/show_bug.cgi?id=32255">32255</a>
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<th>Summary</th>
<td>[X86] Should we use ExeDepsFix to optimize unused input to gather instructions?
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<th>Product</th>
<td>libraries
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>All
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<th>OS</th>
<td>All
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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>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>craig.topper@gmail.com
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<p>
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<pre>If the gather mask is all ones or the input is undef, we force the input to a
zero vector during lowering. It may be better to instead force the input to
undef and let ExeDepsFix handle clearance checking.
We need to be careful though because I think ExeDepsFix will first try to tie
the input to the VSIB index register since that's already an input. We would
need to teach ExeDepsFix about the early clobber restriction on the source
register that makes that illegal.</pre>
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