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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missed chance for auto vectorization"
href="https://bugs.llvm.org/show_bug.cgi?id=38242">38242</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missed chance for auto vectorization
</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>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>Code:
typedef struct {
int *arr;
unsigned size;
} attr_t;
int foo(attr_t *e, int x) {
int s = e->size;
for (unsigned i = 0; i < s; ++i) {
e->arr[i] = i + x;
}
};
Clang -O3
foo(attr_t*, int):
mov rax, qword ptr [rdi]
xor ecx, ecx
.LBB0_1:
lea edx, [rsi + rcx]
mov edi, ecx
mov dword ptr [rax + 4*rdi], edx
add ecx, 1
jmp .LBB0_1
GCC can vectorize it well.
Godbolt:
<a href="https://godbolt.org/g/ytE3UW">https://godbolt.org/g/ytE3UW</a></pre>
</div>
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