<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 - [InstCombine] reduce logic-of-compares with limit constant"
href="https://bugs.llvm.org/show_bug.cgi?id=45618">45618</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[InstCombine] reduce logic-of-compares with limit constant
</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>All
</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>spatel+llvm@rotateright.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>This might be the generalization that I was looking for in <a class="bz_bug_link
bz_status_NEW "
title="NEW - Failure to optimize certain kind of always-true comparisons"
href="show_bug.cgi?id=45510">bug 45510</a>:
define i1 @src(i8 %x, i8 %y) {
%cmpeq = icmp eq i8 %x, 0
%cmp = icmp sgt i8 %x, %y
%r = and i1 %cmp, %cmpeq
ret i1 %r
}
define i1 @tgt(i8 %x, i8 %y) {
%cmpeq = icmp eq i8 %x, 0
%cmp = icmp sgt i8 0, %y
%r = and i1 %cmp, %cmpeq
ret i1 %r
}
<a href="http://volta.cs.utah.edu:8080/z/xh7J4T">http://volta.cs.utah.edu:8080/z/xh7J4T</a>
See D78430 for the large number of potential variations on this pattern:
<a href="https://reviews.llvm.org/D78430">https://reviews.llvm.org/D78430</a>
In that patch, we are focused on the instsimplify-able cases, but if we think
about this as an equal value constant substitution into the non-equality
compare, it applies to more (all?) predicates and constants, and some
combinations "simplify" while others just "combine".</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>