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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 - aarch64 inline asm: miscompilation depending on function parameters order"
href="https://bugs.llvm.org/show_bug.cgi?id=49343">49343</a>
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<th>Summary</th>
<td>aarch64 inline asm: miscompilation depending on function parameters order
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>Other
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>-New Bugs
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>jacob.benoit.1@gmail.com
</td>
</tr>
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>compiler explorer link: <a href="https://godbolt.org/z/e9n49n">https://godbolt.org/z/e9n49n</a>
code:
#include <arm_neon.h>
// output:
// smlal v0.4s, v1.4h, v2.4h
int32x4_t good(int32x4_t acc, int16x4_t x, int16x4_t y) {
asm("smlal %[acc].4s, %[x].4h, %[y].4h"
: [acc]"=w"(acc)
: [x]"w"(x),
[y]"w"(y)
:);
return acc;
}
// output:
// smlal v0.4s, v0.4h, v1.4h
// bug: v0 is used for both x and y arguments!
int32x4_t bad(int16x4_t x, int16x4_t y, int32x4_t acc) {
asm("smlal %[acc].4s, %[x].4h, %[y].4h"
: [acc]"=w"(acc)
: [x]"w"(x),
[y]"w"(y)
:);
return acc;
}</pre>
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