[clang] [Headers][X86] Allow SSE2/AVX2/AVX512F/AVX512BW/AVX512DQ integer arithmetic intrinsics to be used in constexpr (PR #157582)

[Simon Pilgrim via cfe-commits]

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@@ -2060,7 +2060,7 @@ static __inline__ void __DEFAULT_FN_ATTRS _mm_storel_pd(double *__dp,
 ///    A 128-bit vector of [16 x i8].
 /// \returns A 128-bit vector of [16 x i8] containing the sums of both
 ///    parameters.
-static __inline__ __m128i __DEFAULT_FN_ATTRS _mm_add_epi8(__m128i __a,
+static __inline__ __m128i __DEFAULT_FN_ATTRS _mm_add_epi8_CONSTEXPR(__m128i __a,
                                                           __m128i __b) {
   return (__m128i)((__v16qu)__a + (__v16qu)__b);
 }
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RKSimon wrote:

clang-format these changed lines (not the whole file though!)

https://github.com/llvm/llvm-project/pull/157582