<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 - Bad time complexity in Straight Line Strength Reduce ?"
href="https://bugs.llvm.org/show_bug.cgi?id=50223">50223</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Bad time complexity in Straight Line Strength Reduce ?
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</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>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>mikael.holmen@ericsson.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=24826" name="attach_24826" title="bbi-55824.ll reproducer">attachment 24826</a> <a href="attachment.cgi?id=24826&action=edit" title="bbi-55824.ll reproducer">[details]</a></span>
bbi-55824.ll reproducer
It looks like something in slsr has bad time complexity, where increasing the
size of a basic block with 6 instructions makes the execution time increase
with a factor 4.
Reproducer:
opt -slsr -o /dev/null bbi-55824.ll
The reproducer above seems too hang, but perhaps it finishes at some point.
However, in the input file I've made a few comments:
; 3s
; 12s
; 45s
; 3m
; 12m
If commenting out all instructions (except the ending "rets") after the "3s"
comment, execution time is roughly 3 seconds on my machine. If instead
commenting out everything after "12s" it takes 12 seconds etc.
So it looks like every 6 new instructions makes the execution time increase
with a factor 4.</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>