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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - 8-byte loop not vectorized"
href="https://bugs.llvm.org/show_bug.cgi?id=47491">47491</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>8-byte loop not vectorized
</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>Loop Optimizer
</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>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>void pr(char* restrict r, char* restrict a){
#pragma clang loop vectorize(enable)
for (int i = 0; i < 8; i++){
r[i] += a[i];
}
}
Clang -O3:
pr: # @pr
mov al, byte ptr [rsi]
add byte ptr [rdi], al
mov al, byte ptr [rsi + 1]
add byte ptr [rdi + 1], al
mov al, byte ptr [rsi + 2]
add byte ptr [rdi + 2], al
mov al, byte ptr [rsi + 3]
add byte ptr [rdi + 3], al
mov al, byte ptr [rsi + 4]
add byte ptr [rdi + 4], al
mov al, byte ptr [rsi + 5]
add byte ptr [rdi + 5], al
mov al, byte ptr [rsi + 6]
add byte ptr [rdi + 6], al
mov al, byte ptr [rsi + 7]
add byte ptr [rdi + 7], al
ret
ICC or GCC -O3 (without any pragma):
pr:
movq xmm1, QWORD PTR [rdi] #3.9
movq xmm0, QWORD PTR [rsi] #3.17
paddb xmm1, xmm0 #3.9
movq QWORD PTR [rdi], xmm1 #3.9
ret</pre>
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