[clang] [Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - add MMX/SSE/AVX/AVX512 PMULHRSW intrinsics to be used in constexpr (PR #160636)

[Simon Pilgrim via cfe-commits]

================
@@ -544,7 +544,7 @@ _mm_maddubs_pi16(__m64 __a, __m64 __b) {
 ///    A 128-bit vector of [8 x i16] containing one of the source operands.
 /// \returns A 128-bit vector of [8 x i16] containing the rounded and scaled
 ///    products of both operands.
-static __inline__ __m128i __DEFAULT_FN_ATTRS _mm_mulhrs_epi16(__m128i __a,
+static __inline__ __m128i __DEFAULT_FN_ATTRS_CONSTEXPR _mm_mulhrs_epi16(__m128i __a,
                                                               __m128i __b) {
----------------
RKSimon wrote:

clang-format:
```c
static __inline__ __m128i __DEFAULT_FN_ATTRS_CONSTEXPR
_mm_mulhrs_epi16(__m128i __a, __m128i __b) {
   return (__m128i)__builtin_ia32_pmulhrsw128((__v8hi)__a, (__v8hi)__b);
}
```

https://github.com/llvm/llvm-project/pull/160636