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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Suboptimal lowering of `mul x, 0b111....` when using SelectionDAG"
href="https://bugs.llvm.org/show_bug.cgi?id=49244">49244</a>
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<th>Summary</th>
<td>Suboptimal lowering of `mul x, 0b111....` when using SelectionDAG
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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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>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: M68k
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>minyihh@uci.edu
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<th>CC</th>
<td>glaubitz@physik.fu-berlin.de, llvm-bugs@lists.llvm.org, minyihh@uci.edu
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<p>
<div>
<pre>As described in test/CodeGen/M68k/ASM/Arith/imul-neg.ll, when multiplying value
`x` with 2^n - 1 integer, the result will be `-x`, which is preferred to be
lowered to `neg x` instruction. However, SelectionDAG ISel will generate `sub
0, x` (FastISel doesn't have this problem though).</pre>
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