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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 - [11 regression] No elimination of conditional addition of zero"
href="https://bugs.llvm.org/show_bug.cgi?id=47730">47730</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[11 regression] No elimination of conditional addition of zero
</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>
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<th>OS</th>
<td>Windows NT
</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>
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<th>Component</th>
<td>Scalar Optimizations
</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>struct vector {
int *data;
unsigned long size;
};
int *vector_end_zero_add(struct vector *vec)
{
if (vec->size == 0)
return vec->data;
return vec->data + vec->size;
}
Trunk:
vector_end_zero_add(vector*): # @vector_end_zero_add(vector*)
mov rcx, qword ptr [rdi]
mov rax, qword ptr [rdi + 8]
test rax, rax
lea rax, [rcx + 4*rax]
cmove rax, rcx
ret
10.0.1:
vector_end_zero_add(vector*): # @vector_end_zero_add(vector*)
mov rax, qword ptr [rdi + 8]
shl rax, 2
add rax, qword ptr [rdi]
ret
What is really weird, with "unsigned size;", even Clang 10.0.1 cannot optimize
it.
Current codegen:
<a href="https://godbolt.org/z/1Pr43K">https://godbolt.org/z/1Pr43K</a></pre>
</div>
</p>
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