<html>
<head>
<base href="https://bugs.llvm.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [llvm-mca] How to model "result bus bubbles"?"
href="https://bugs.llvm.org/show_bug.cgi?id=42300">42300</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[llvm-mca] How to model "result bus bubbles"?
</td>
</tr>
<tr>
<th>Product</th>
<td>tools
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>llvm-mca
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>lebedev.ri@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>andrea.dibiagio@gmail.com, llvm-bugs@lists.llvm.org, matthew.davis@sony.com
</td>
</tr></table>
<p>
<div>
<pre>"AMD Software Optimization Guide for AMD Family 10h and 12h Processors", page
250 of PDF:
"Multiplication operations always issue to integer pipe 0, and the issue logic
creates result bus bubbles for the multiplier in integer pipes 0 and 1 by
preventing non-multiply micro-ops from issuing at the appropriate time."
So in other words, as far as i understand it when "Integer Multiplier" is
occupied,
no microops may be issued to the pipe 0 and/or 1, and ALU/AGU units in those
pipes
are unoccupied.
I'm not quite sure how to model that correctly.
I did see comments for "BufferSize = 0", but i'm not sure how to limit that to
only
certain pipes/ProcResource's, since the pipe3 (it's alu/agu units) and fpu
pipes
should not be affected.
Any hints, please? :)</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>