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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [AArch64] shufflevector with constants uses 4 ext instructions"
href="https://llvm.org/bugs/show_bug.cgi?id=29125">29125</a>
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<th>Summary</th>
<td>[AArch64] shufflevector with constants uses 4 ext instructions
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: AArch64
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>spatel+llvm@rotateright.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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</tr>
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<th>Classification</th>
<td>Unclassified
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</tr></table>
<p>
<div>
<pre>I don't know AArch, but this doesn't look good:
define <4 x float> @goo(<4 x float> %x) {
%shuf = shufflevector <4 x float> %x, <4 x float> <float undef, float 1.0,
float 2.0, float undef>, <4 x i32><i32 0, i32 5, i32 6, i32 3>
ret <4 x float> %shuf
}
$ ./llc -o - min.ll -mtriple=aarch64
adrp x8, .LCPI1_0
ldr q1, [x8, :lo12:.LCPI1_0]
ext v1.16b, v0.16b, v1.16b, #12
ext v0.16b, v1.16b, v0.16b, #4
ext v1.16b, v1.16b, v1.16b, #8
ext v0.16b, v0.16b, v1.16b, #12
ret
--------------------------------------------------------------------------
Should this be 'bsl'?
Or 2 inserts?
fmov s1, #1.00000000
ins v0.s[1], v1.s[0]
fmov s1, #2.00000000
ins v0.s[2], v1.s[0]
ret</pre>
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