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 bug64;

void main()
{
    float f;
    float* p = &f;
    float* end1 = p+1;
    float* end2 = 1+p;
    assert(end1 is end2);
}