[clang] [Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - allow AVX/AVX512 subvector insertion intrinsics to be used in constexpr #157709 (PR #158778)

[Simon Pilgrim via cfe-commits]

================
@@ -513,6 +510,12 @@ let Features = "avx", Attributes = [NoThrow, Const, RequiredVectorWidth<256>] in
   def roundps256 : X86Builtin<"_Vector<8, float>(_Vector<8, float>, _Constant int)">;
 }
 
+let Features = "avx", Attributes = [NoThrow, Const, Constexpr, RequiredVectorWidth<256>] in {
+  def vinsertf128_pd256 : X86Builtin<"_Vector<4, double>(_Vector<4, double>, _Vector<2, double>, _Constant int)">;
+  def vinsertf128_ps256 : X86Builtin<"_Vector<8, float>(_Vector<8, float>, _Vector<4, float>, _Constant int)">;
+  def vinsertf128_si256 : X86Builtin<"_Vector<8, int>(_Vector<8, int>, _Vector<4, int>, _Constant int)">;
----------------
RKSimon wrote:

maybe move these to be with blendpd256 etc?

https://github.com/llvm/llvm-project/pull/158778