Re: Unexpected interval comparison

I wrote:
> Looking at what we've got here, it's already a substantial fraction of
> what would be needed to provide a compiler-independent implementation
> of the int128-based aggregate logic in numeric.c.  With that in mind,
> I propose that we extract the relevant stuff into a new header file
> that is designed as general-purpose int128 support.  Something like the
> attached.  I also attach the test program I put together to verify it.

Here's a fleshed-out patch for the original problem based on that.
I found that direct int64-to-int128 coercions were also needed to
handle some of the steps in timestamp.c, so I added those to int128.h.

I think it would be reasonable to back-patch this, although it would
need some adjustments for the back branches since we only recently
got rid of the float-timestamp option.  Also I'd not be inclined to
depend on native int128 any further back than it was already in use.

			regards, tom lane