anonymou5 (no.delete@this.spam.com) on August 21, 2013 6:27 pm wrote:
> David Kanter (dkanter.delete@this.realworldtech.com) on August 21, 2013 1:34 pm wrote:
> > Yes, I would have eliminated x87 from long mode.
>
> Would you have added 80-bit EP support to XMM/SSE though?

So I understand there are real benefits to the extra precision. In particular, it makes performance vs. accuracy a much more smooth trade-off. E.g., if you only need a few calculations in higher precision (say a final accumulate), you can get that accuracy without a huge penalty in performance.

However, I don't like it at all since it makes things numerically unstable depending on whether you need to spill to memory or not. It also makes validation and verification a pain.

Just to be clear, my long term goal would be to eliminate x87 entirely (and as many other nasty historical artifacts as possible). It's something that might not pay dividends immediately, but if the cost is low, the benefits in 5-10 years could be significant.

Deprecating old and nasty stuff like x87 is fine, but you still end up with lots of control logic, microcode and other complexity in your design.

David