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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [SIMD] pattern for i32x4.dot_i16x8_s not recognized"
href="https://bugs.llvm.org/show_bug.cgi?id=50810">50810</a>
</td>
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<th>Summary</th>
<td>[SIMD] pattern for i32x4.dot_i16x8_s not recognized
</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>
<tr>
<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>Backend: WebAssembly
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<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>With -msimd128 -O3, the compiler wont't recognize the following snippet as an
i32x4.dot_i16x8_s.
It also scalarizes a lot of stuff; the WASM backend seems to have a lot of
trouble with non-128-bit vectors. Even if this wasn't recognized as a dot
product, I'd hope to see some extmuls (or at least i16x8.extend_low/high and
i32x4.mul) and shuffles for this. I can file another bug for that if you want.
Anyways, here is the example (Compiler Explorer:
<a href="https://godbolt.org/z/an4jKTnf5">https://godbolt.org/z/an4jKTnf5</a>):
#include <stdint.h>
typedef int16_t i16x8 __attribute__((__vector_size__(16)));
typedef int32_t i32x4 __attribute__((__vector_size__(16)));
i32x4
dot(i16x8 a, i16x8 b) {
int32_t prod __attribute__((__vector_size__(32))) =
__builtin_convertvector(a, __typeof__(prod)) *
__builtin_convertvector(b, __typeof__(prod));
return
__builtin_shufflevector(prod, prod, 0, 2, 4, 6) +
__builtin_shufflevector(prod, prod, 1, 3, 5, 7);
}</pre>
</div>
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