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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [GVN] Should be able to PRE a load from memset"
href="https://llvm.org/bugs/show_bug.cgi?id=25559">25559</a>
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<th>Summary</th>
<td>[GVN] Should be able to PRE a load from memset
</td>
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<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>mcrosier@codeaurora.org
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Currently, GVN can pre loads from calloc like functions. For example, in the
below test case the store to 'res' will be converted from a load into a
constant zero.
#include <strings.h>
#include <stdlib.h>
int *test_calloc(int n, int *res)
{
if (n == 0)
return 0;
int *ptr = (int *)calloc(n, sizeof(int));
*res = ptr[n-1];
return ptr;
}
However, PRE falls apart with this example:
int *test_malloc_memset_zero(int n, int *res)
{
if (n == 0)
return 0;
int *ptr = (int *)malloc(n * sizeof(int));
bzero(ptr, n * sizeof(int));
*res = ptr[n-1];
return ptr;
}</pre>
</div>
</p>
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