[all-commits] [llvm/llvm-project] 7e0923: [CodeGen][MISched] Handle empty sized resource usa...

[Michael Maitland via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7e09239e24b339f45f63a670e2e831150826bf70
      https://github.com/llvm/llvm-project/commit/7e09239e24b339f45f63a670e2e831150826bf70
  Author: Michael Maitland <michaeltmaitland at gmail.com>
  Date:   2024-01-24 (Wed, 24 Jan 2024)

  Changed paths:
    M llvm/lib/CodeGen/MachineScheduler.cpp
    M llvm/unittests/CodeGen/SchedBoundary.cpp

  Log Message:
  -----------
  [CodeGen][MISched] Handle empty sized resource usage. (#75951)

TargetSchedule.td explicitly allows the usage of a ProcResource for zero
cycles, in order to represent that the ProcResource must be available
but is not consumed by the instruction. On the other hand,
ResourceSegments explicitly does not allow for a zero sized interval. In
order to remedy this, this patch handles the special case of when there
is an empty interval usage of a resource by not adding an empty
interval.

We ran into this issue downstream, but it makes sense to have
this upstream since it is explicitly allowed by TargetSchedule.td.