<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/154911>154911</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Headers][X86] Convert bf16 to f32 conversions to generic constexpr implementations
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            good first issue,
            backend:X86,
            clang:frontend,
            clang:headers,
            constexpr
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          RKSimon
      </td>
    </tr>
</table>

<pre>
    Now that we have the __bf16 type, the BF16 intrinsics can be converted to use standard conversions instead of bit twiddling that interferes with fp optimisations:
e.g.
```
static __inline__ float __DEFAULT_FN_ATTRS _mm_cvtsbh_ss(__bf16 __A) {
  return __builtin_ia32_cvtsbf162ss_32(__A); // remove __builtin_ia32_cvtsbf162ss_32
}
```
-->
```
static __inline__ float __DEFAULT_FN_ATTRS_CONSTEXPR _mm_cvtsbh_ss(__bf16 __A) {
  return (float)(__A);
}
```
and
```
static __inline__ __m512 __DEFAULT_FN_ATTRS512 _mm512_cvtpbh_ps(__m256bh __A) {
  return _mm512_castsi512_ps((__m512i)_mm512_slli_epi32(
 (__m512i)_mm512_cvtepi16_epi32((__m256i)__A), 16));
}
```
-->
```
static __inline__ __m512 __DEFAULT_FN_ATTRS512_CONSTEXPR _mm512_cvtpbh_ps(__m256bh __A) {
  return (__m512)__builtin_convertvector(__A, __v16sf);
}
```
All the mask/maskz cvtpbh variants in avx512bf16intrin.h and avx512vlbf16intrin.h can be updated similarly
</pre>
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