[AST][SVE] Treat built-in SVE types as trivially copyable

[rsandifo-arm]

Summary

SVE types are trivially copyable: they can be copied simply
by reproducing the byte representation of the source object.

[efriedma]

LGTM

clang/lib/AST/Type.cpp

bool QualType::isTriviallyCopyableType(const ASTContext &Context) const {
   //   Scalar types, trivially copyable class types, arrays of such types, and
   //   cv-qualified versions of these types are collectively
   //   called trivially copyable types.
 
   QualType CanonicalType = getCanonicalType();
   if (CanonicalType->isDependentType())
     return false;
 
+  if (CanonicalType->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 (CanonicalType->isIncompleteType())
     return false;
 
   // As an extension, Clang treats vector types as Scalar types.
   if (CanonicalType->isScalarType() || CanonicalType->isVectorType())
     return true;

clang/test/SemaCXX/sizeless-1.cpp

 #endif
 
   (void)typeid(__SVInt8_t);
   (void)typeid(__SVInt8_t *);
   (void)typeid(local_int8);
   (void)typeid(ref_int8);
   (void)typeid(static_int8_ptr);
 
+  _Static_assert(__is_trivially_copyable(svint8_t), "");
   _Static_assert(__is_trivially_destructible(svint8_t), "");
   _Static_assert(!__is_nothrow_assignable(svint8_t, svint8_t), "");
   _Static_assert(__is_nothrow_assignable(svint8_t &, svint8_t), "");
   _Static_assert(!__is_nothrow_assignable(svint8_t &, svint16_t), "");
   _Static_assert(__is_constructible(svint8_t), "");
   _Static_assert(__is_constructible(svint8_t, svint8_t), "");
   _Static_assert(!__is_constructible(svint8_t, svint8_t, svint8_t), "");
   _Static_assert(!__is_constructible(svint8_t, svint16_t), "");
#endif
   for (auto x : local_int8) { // expected-error {{no viable 'begin' function available}}
   }
   for (auto x : wrapper<svint8_t>()) {
     (void)x;
   }
   for (const svint8_t &x : wrapper<svint8_t>()) { // expected-warning {{loop variable 'x' binds to a temporary value produced by a range of type 'wrapper<svint8_t>'}} expected-note {{use non-reference type}}
     (void)x;
   }
-  // This warning is bogus and will be removed by a later patch.
-  // The point is to show that it's being removed for the right reasons.
-  for (const svint8_t x : wrapper<const svint8_t &>()) { // expected-warning {{loop variable 'x' creates a copy from type 'const svint8_t'}} expected-note {{use reference type}}
+  for (const svint8_t x : wrapper<const svint8_t &>()) {
     (void)x;
   }
 #endif
 }
 
 #if __cplusplus >= 201103L
 svint8_t ret_bad_conv() { return explicit_conv(); } // expected-error {{no viable conversion from returned value of type 'explicit_conv' to function return type 'svint8_t'}}
 #endif