<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 - [Regression] MemorySSA DSE fails to remove redundant memcpy"
href="https://bugs.llvm.org/show_bug.cgi?id=50339">50339</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[Regression] MemorySSA DSE fails to remove redundant memcpy
</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>Windows NT
</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>david.bolvansky@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>extern char a[32];
void f (const void *s)
{
char *p = (char*)__builtin_memcpy (a, s, 16) + 16;
__builtin_memcpy (p - 16, s, 16);
}
Regressed with LLVM 12.
Current IR:
@a = external dso_local local_unnamed_addr global [32 x i8], align 16
define dso_local void @_Z1fPKv(i8* nocapture readonly %0) local_unnamed_addr #0
{
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* nonnull align 16
dereferenceable(16) getelementptr inbounds ([32 x i8], [32 x i8]* @a, i64 0,
i64 0), i8* nonnull align 1 dereferenceable(16) %0, i64 16, i1 false)
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* nonnull align 16
dereferenceable(16) getelementptr inbounds ([32 x i8], [32 x i8]* @a, i64 0,
i64 0), i8* nonnull align 1 dereferenceable(16) %0, i64 16, i1 false)
ret void
}
<a href="https://godbolt.org/z/vdTGjdTvn">https://godbolt.org/z/vdTGjdTvn</a></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>