<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 - [X86] or/add-like mismatch in uchar 'splat' to uint"
href="https://bugs.llvm.org/show_bug.cgi?id=49055">49055</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[X86] or/add-like mismatch in uchar 'splat' to uint
</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>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>craig.topper@gmail.com, lebedev.ri@gmail.com, llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com
</td>
</tr></table>
<p>
<div>
<pre><a href="https://simd.godbolt.org/z/E15MrP">https://simd.godbolt.org/z/E15MrP</a>
void loop_add(const unsigned char* __restrict pIn, unsigned int* __restrict
pOut, int s) {
for (int i = 0; i < s; i++) {
unsigned int pixelChar = pIn[i];
unsigned int pixel = pixelChar + (pixelChar << 8) + (pixelChar << 16) +
(255 << 24);
pOut[i] = pixel;
}
}
This successfully combines to a zext+mul+add (I think technically it could be
zext+mul+or)?
But this:
void loop_or(const unsigned char* __restrict pIn, unsigned int* __restrict
pOut, int s) {
for (int i = 0; i < s; i++) {
unsigned int pixelChar = pIn[i];
unsigned int pixel = pixelChar | (pixelChar << 8) | (pixelChar << 16) |
(255 << 24);
pOut[i] = pixel;
}
}
completely fails and we end up with a long shift+or chain.</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>