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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - miscompilation: segfault with -O2"
href="https://bugs.llvm.org/show_bug.cgi?id=38670">38670</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>miscompilation: segfault with -O2
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</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>
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<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>C++
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>ohh.epicfail@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Using clang version 8.0.0 (trunk 340324) the following program crashes with
segfault with -O2. It looks like incorrect vectorization in asm. The problem
causes hand-made loop 'peeling' in example3 function. Also, clang 6.0.0 compile
this code incorrectly
#define N 1024
#define ALIGNED16 __attribute__((aligned(16)))
int ia[N] ALIGNED16;
int ib[N] ALIGNED16;
void init_memory(void *start, void *end) {
unsigned char state = 1;
while (start != end) {
state *= 7;
state ^= 0x27;
state += 1;
*((unsigned char *)start) = state;
start = ((char *)start) + 1;
}
}
typedef int aint __attribute__((__aligned__(16)));
__attribute__((noinline)) void example3(int n, aint *__restrict__ p,
aint *__restrict q) {
n--;
*p++ = *q++;
while (n--) {
*p++ = *q++;
}
}
int main() {
init_memory(&ia[0], &ia[N]);
init_memory(&ib[0], &ib[N]);
example3(N, ia, ib);
return 0;
}</pre>
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