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> out-of-order cores which dynamically schedule at runtime. OOO architectures don't reschedule dynamically - that's impossible - they just have multiple instru

> out-of-order cores which dynamically schedule at runtime. OOO architectures don't reschedule dynamically - that's impossible - they just have multiple instruction buffers that can issue the instructions. So scheduling is still important for OOO it's just at the level of DDG instead of literally linear order in the binary. Edit: just want to emphasize > It's only going to be useful if you're writing code for some machine that doesn't do that There is no architecture for which instruction scheduling isn't crucial.

ajb 2y ago
If you're talking about modifying the DDG, I would not call that scheduling. Because then you need to do serious work to prove that your code is actually doing the same thing. But I haven't spent a lot of time in the compiler world, so maybe they do call it that. Perhaps you could give your definition?
- dzaima 2y ago
  Needing to do serious work would correlate with Exo having multiple publications about its design. It's a broader sense of scheduling than "reorder trivially-independent instructions", but, if you remove the "trivially-" part and replace "instructions" with "operations", it's the same concept of doing transformations that only move around when certain things happen.
achierius 2y ago
> There is no architecture for which instruction scheduling isn't crucial. In my experience doing back-end compiler work, it's definitely last on the list of major concerns. Obviously you can't ignore it, but it's not where any significant gains are coming from, and anything 'fancy' you do there is likely to be picked up by future generations of hardware.
- almostgotcaught 2y ago
  > but it's not where any significant gains are coming from i have no clue what you're saying here - if your scheduler fucks up your pipelining you're gonna have a bad time (conversely if you're scheduler recognizes pipelining opportunities you're gonna have a good time). as usual anyone who says something like "in my experience it's not a big deal" simply does not have enough experience.
  - ForTheKidz 2y ago
    Yes, clearly we should have spent more time trying to coax our cpus into fucking up pipelining.

ajb 2y ago

If you're talking about modifying the DDG, I would not call that scheduling. Because then you need to do serious work to prove that your code is actually doing the same thing. But I haven't spent a lot of time in the compiler world, so maybe they do call it that. Perhaps you could give your definition?

dzaima 2y ago
Needing to do serious work would correlate with Exo having multiple publications about its design. It's a broader sense of scheduling than "reorder trivially-independent instructions", but, if you remove the "trivially-" part and replace "instructions" with "operations", it's the same concept of doing transformations that only move around when certain things happen.

achierius 2y ago

> There is no architecture for which instruction scheduling isn't crucial. In my experience doing back-end compiler work, it's definitely last on the list of major concerns. Obviously you can't ignore it, but it's not where any significant gains are coming from, and anything 'fancy' you do there is likely to be picked up by future generations of hardware.

almostgotcaught 2y ago
> but it's not where any significant gains are coming from i have no clue what you're saying here - if your scheduler fucks up your pipelining you're gonna have a bad time (conversely if you're scheduler recognizes pipelining opportunities you're gonna have a good time). as usual anyone who says something like "in my experience it's not a big deal" simply does not have enough experience.
- ForTheKidz 2y ago
  Yes, clearly we should have spent more time trying to coax our cpus into fucking up pipelining.