[clang] [Clang] Add __builtin_selectvector and use it for AVX512 intrinsics (PR #91306)

[Phoebe Wang via cfe-commits]

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@@ -3744,6 +3744,12 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     return RValue::get(Result);
   }
 
+  case Builtin::BI__builtin_selectvector: {
+    return RValue::get(Builder.CreateSelect(EmitScalarExpr(E->getArg(2)),
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phoebewang wrote:

Should we check all one (or all zero) like we did in `EmitX86Select`?

https://github.com/llvm/llvm-project/pull/91306