[AST][SVE] Treat built-in SVE types as trivial

[rsandifo-arm]

Summary

Built-in SVE types are trivial, since they're trivially copyable
and support default construction.

[efriedma]

LGTM.

clang/lib/AST/Type.cpp

bool QualType::isTrivialType(const ASTContext &Context) const {
   // We return false for that case. Except for incomplete arrays of PODs, which
   // are PODs according to the standard.
   if (isNull())
     return false;
 
   if ((*this)->isArrayType())
     return Context.getBaseElementType(*this).isTrivialType(Context);
 
+  if ((*this)->isSizelessBuiltinType())
+    return true;
+
   // Return false for incomplete types after skipping any incomplete array
   // types which are expressly allowed by the standard and thus our API.
   if ((*this)->isIncompleteType())
     return false;
 
   if (hasNonTrivialObjCLifetime())
     return false;
 

clang/test/SemaCXX/sizeless-1.cpp

#endif
   _Static_assert(__is_convertible_to(svint8_t, svint8_t), "");
   _Static_assert(!__is_convertible_to(svint8_t, svint16_t), "");
   _Static_assert(!__is_empty(svint8_t), "");
   _Static_assert(!__is_enum(svint8_t), "");
   _Static_assert(!__is_final(svint8_t), "");
   _Static_assert(!__is_literal(svint8_t), "");
   _Static_assert(__is_pod(svint8_t), "");
   _Static_assert(!__is_polymorphic(svint8_t), "");
+  _Static_assert(__is_trivial(svint8_t), "");
   _Static_assert(__is_object(svint8_t), "");
   _Static_assert(!__is_arithmetic(svint8_t), "");
   _Static_assert(!__is_floating_point(svint8_t), "");
   _Static_assert(!__is_integral(svint8_t), "");
   _Static_assert(!__is_void(svint8_t), "");
   _Static_assert(!__is_array(svint8_t), "");
   _Static_assert(!__is_function(svint8_t), "");
   _Static_assert(!__is_reference(svint8_t), "");