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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->12 regression] Improper assignment fusion"
href="https://bugs.llvm.org/show_bug.cgi?id=50635">50635</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[11->12 regression] Improper assignment fusion
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</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>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>blubban@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>To reproduce:
#include <stdint.h>
struct S1 {
uint8_t val1;
uint8_t this_gets_clobbered;
uint16_t val2;
};
void test(S1 src, S1* dest) {
dest->val1 = src.val1;
dest->val2 = src.val2;
}
Compile with -O1 or higher, with Clang 12.0.0 or higher (codegen is proper on
11.0.1).
Expected result:
test(S1, S1*): # @test(S1, S1*)
mov byte ptr [rsi], dil
shr edi, 16
mov word ptr [rsi + 2], di
ret
Actual result:
test(S1, S1*): # @test(S1, S1*)
mov dword ptr [rsi], edi
ret
Compiler Explorer: <a href="https://godbolt.org/z/1W1oKdfcG">https://godbolt.org/z/1W1oKdfcG</a>
Found by user @fifty#1323 on Discord.</pre>
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</p>
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