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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Cortex-A5 codegen suboptimal?"
href="https://llvm.org/bugs/show_bug.cgi?id=26135">26135</a>
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<th>Summary</th>
<td>Cortex-A5 codegen suboptimal?
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>3.7
</td>
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<th>Hardware</th>
<td>Other
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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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: ARM
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>tulipawn@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>It seems code generation for Cortex-A5 and armv7 doesn't provide much benefit,
sometimes even coming out a little slower (compared to default and v6
respectively).
Firstly, our old friend from issue #26106, w/o NEON and unrolling:
default cpu - v7, v6:
test sum_deque ... bench: 5,219 ns/iter (+/- 56), 4,967 ns/iter (+/-
50)
test sum_deque_2 ... bench: 3,272 ns/iter (+/- 40), 3,112 ns/iter (+/-
22)
It seems v6 code is faster on this cpu.
Secondly a few benchmarks, where the cortex-a5 target is either equal or
slower. (4-core)
Spectral-norm benchmark, v7:
$ time ./spectral 5500
default cpu cortex-a5
real 0m9.106s real 0m9.051s
user 0m34.110s user 0m34.240s
sys 0m0.040s sys 0m0.020s
Fannkuch benchmark:
$ time ./fannkuch 12
real 0m30.017s real 0m30.645s
user 1m55.570s user 1m56.350s
sys 0m0.030s sys 0m0.010s
Command used to compile:
rustc -C opt-level=3 -C target-feature=+v7 -C target-cpu=cortex-a5
Those were just a few examples off the top of my head, probably not the best
ones. I'm sure I've also seen an example or two benefiting from the cortex-a5
target but can't remember which.</pre>
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