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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [llvm-exegesis] Latency varies depending on selected register."
href="https://bugs.llvm.org/show_bug.cgi?id=37563">37563</a>
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<th>Summary</th>
<td>[llvm-exegesis] Latency varies depending on selected register.
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>new bugs
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>courbet@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>./bin/llvm-exegesis -mode=latency -opcode-name=MPSADBWrri
has latency 7 or 6 depending on the time of day.
We should select registers in a deterministic way for a given operand sequence
so that we can compare instructions together (for example, right now alalysis
find inconsistencies between VMPSADBWrri and MPSADBWrri but they are the same).
This is orthogonal to exploring the register assignments and/or values).
---
key:
opcode_name: MPSADBWrri
mode: latency
config: ''
cpu_name: haswell
llvm_triple: x86_64-unknown-linux-gnu
num_repetitions: 10000
measurements:
- { key: latency, value: 7.0057, debug_string: '' }
error: ''
info: 'explicit self cycles, selecting one aliasing configuration.
Snippet:
MPSADBWrri XMM11, XMM11, XMM11, 1
'
...
---
key:
opcode_name: MPSADBWrri
mode: latency
config: ''
cpu_name: haswell
llvm_triple: x86_64-unknown-linux-gnu
num_repetitions: 10000
measurements:
- { key: latency, value: 6.0057, debug_string: '' }
error: ''
info: 'explicit self cycles, selecting one aliasing configuration.
Snippet:
MPSADBWrri XMM15, XMM15, XMM13, 1
'
...</pre>
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