<html>
<head>
<base href="http://llvm.org/bugs/" />
</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 --- - failure to remove trivially dead loop"
href="http://llvm.org/bugs/show_bug.cgi?id=20568">20568</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>failure to remove trivially dead loop
</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>normal
</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>richard-llvm@metafoo.co.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>From
<a href="http://stackoverflow.com/questions/25151508/why-dont-modern-c-compilers-optimize-away-simple-loops-like-this-clang-msv">http://stackoverflow.com/questions/25151508/why-dont-modern-c-compilers-optimize-away-simple-loops-like-this-clang-msv</a>
LLVM does not remove the loops in this code:
#include <stdio.h>
#include <time.h>
static int const N = 0x8000;
int main()
{
clock_t const start = clock();
for (int i = 0; i < N; ++i)
{
int a[N]; // Never used outside of this block, but not optimized
away
for (int j = 0; j < N; ++j)
{
++a[j]; // This is undefined behavior too, but Clang doesn't see
it
}
}
clock_t const finish = clock();
fprintf(stderr, "%u ms\n",
static_cast<unsigned int>((finish - start) * 1000 / CLOCKS_PER_SEC));
return 0;
}
(See also PR13050; this seems like a different problem, though.)</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>