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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [SIMD] shuffle + convert doesn't lower to f64x2.promote_low_f32x4"
href="https://bugs.llvm.org/show_bug.cgi?id=50232">50232</a>
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<th>Summary</th>
<td>[SIMD] shuffle + convert doesn't lower to f64x2.promote_low_f32x4
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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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>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: WebAssembly
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>clang@evan.coeusgroup.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>LLVM misses an opportunity to emit f64x2.promote_low_f32x4. Instead, it
extracts each lane, runs f64.promote_f32 on the extracted value, then inserts
the result.
Test case:
#include <wasm_simd128.h>
v128_t
alt_f64x2_promote_low_f32x4(v128_t __a) {
return (v128_t)
__builtin_convertvector(
__builtin_shufflevector((__f32x4) __a, (__f32x4) __a, 0, 1),
__f64x2
);
// return (v128_t)__builtin_wasm_promote_low_f32x4_f64x2((__f32x4)__a);
}
On Compiler Explorer: <a href="https://godbolt.org/z/xx68PfoTd">https://godbolt.org/z/xx68PfoTd</a></pre>
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