[PATCH] D65506: [MachineScheduler] improve reuse of 'releaseNode'method

[Lorenzo Casalino via Phabricator via llvm-commits]

DoktorC added a comment.

> It is because you are splitting the template declaration and definition into header and cpp. Usually, you need to add the explicit template instantiation in the cpp. However, I am not sure if it is a good idea to use template ... BTW, it compiles clean if with clang.

You are totally right about explicit instantiation.

Regarding the usage of a template argument, instead of a function parameter, lies in the fact that the scheduler is aware whether
a node is in the `Pending` queue or not, when calling `releaseNode`.
Indeed, such method is invoked in two occasions

- a node is scheduled: successors/predecessors are released; thus, they're known to be not in the `Pending` queue.
- moving nodes from pending to available state; the nodes are known to be in the `Pending` queue.

As a consequence, part of the operations perfomed by 'releaseNode' may be actively skipped, avoiding the
overheads of control instructions. (Yes, modern architectures are endowed with branch predictors; but I do not
think that such an argument saves us from correctly employ known invariants in the algorithms.)


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https://reviews.llvm.org/D65506