Only call class invariant if one provably exists in any base classes

[ibuclaw]

This is an interesting optimization that turns:

if (this != 0B)
  {
    _D9invariant12_d_invariantFC6ObjectZv (this);
  }

Into:

  if (this != 0B)
    {
      if (**(struct TypeInfo_Class * * *) this == (struct TypeInfo_Class *) &MyClass.__Class)
        {
          (void) 0;
        }
      else
        {
          _D9invariant12_d_invariantFC6ObjectZv (this);
        }
    }

If the given MyClass object has no invariants found in it's vtable.

In some contrived benchmarks, I found this to achieve 2% better runtime results in non-release builds vs. turning off invariants altogether with -fno-invariants (with -O2, I should try non-optimized builds too).

Just waiting to here back if there are any thoughts in the community on this, but I can't think of a problem on my end.

[ibuclaw]

Discussion here: http://forum.dlang.org/post/[email protected]

[dnadlinger]

Do you handle static arrays correctly?

[ibuclaw]

@klickverbot - Unless that's a recent thing. No. The virtual invariant calls are created in the frontend (see func.c for addPreInvariant/addPostInvariant)

[ibuclaw]

Unless you mean:

NoInvariantClass[42] arr;
assert(arr[0]);

Which will do a test for classinfo equality before calling _d_invariant