[llvm-commits] Speeding up instruction selection

[Roman Levenstein]

2008/4/2, Evan Cheng <evan.cheng at apple.com>:
>
>  On Apr 2, 2008, at 12:55 AM, Roman Levenstein wrote:
>
>  > Hi Evan,
>  >
>  > 2008/4/1, Evan Cheng <evan.cheng at apple.com>:
>  >> Please hold off checking it in for a bit. llvm tot is having some
>  >> problems and I'd like to get to the bottom of it first.
>  >
>  > OK.
>  >
>  >> Also, the tie breaker is less than ideal. I think we need a tie-
>  >> breaker that is "the SUnit that's added to the queue is preferred".
>  >> That means it prefers nodes which are closer to the end of block.
>  >> What
>  >> do you think?
>  >
>  > Do you actually mean "the SUnit that's added to the queue LAST (or
>  > FIRST) is preferred"? I'll think about it.
>
>
> Yep "first".  Basically, if all else being equal, let the node that's
>  ready first be scheduled first. We can add a order id to SUnit which
>  gets set when it's pushed into the ready queue. What do you think?

Makes sense. The queue should have a global "current id" counter. Its
current value is assigned to each node being inserted into the ready
queue and then incremented. When the node is removed from the queue
for any reason, its queue order id is reset. It should be rather easy
to implement.

BTW, do you really want this queue order id in the SUnit or in a
separate array indexed by SUnit unique ids?

-Roman