Add some alignment info where LLVM might otherwise be more pessimistic. In particular, %.nest_arg is always aligned even though it's bitcast from i8*. Pointers in vtables are also guaranteed to be stored at aligned addresses.

module complex4;

void main()
{
    cfloat c = 2f + 3fi;
    float r = cast(float)c;
    ifloat i = cast(ifloat)c;
}