<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 - Signed division with power of two - eliminate test instruction"
href="https://bugs.llvm.org/show_bug.cgi?id=44346">44346</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Signed division with power of two - eliminate test instruction
</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>Backend: X86
</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>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
</td>
</tr></table>
<p>
<div>
<pre>After PR43197, we have a better codegen for signed division with power of two,
but it could be improved a bit.
int al2(int x) {
return ((x + 3 )/4) *4;
}
We have:
al2(int): # @al2(int)
lea eax, [rdi + 3]
add edi, 6
test eax, eax
cmovs eax, edi
and eax, -4
ret
But test instruction could be eliminated, like GCC does:
al2(int):
lea eax, [rdi+6]
add edi, 3
cmovns eax, edi
and eax, -4
ret
<a href="https://godbolt.org/z/C9ij3Y">https://godbolt.org/z/C9ij3Y</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>