[llvm] TargetSchedule: correct latency by cycles elapsed from def to use (PR #74088)

[Jay Foad via llvm-commits]

jayfoad wrote:

> Is the idea behind the patch sound?

In my opinion - no. I think the result of `computeOperandLatency` should not depend on the current position of `DefMI` and `UseMI`. It should just tell you how many cycles must elapse after `DefMI` is issued, until `UseMI` could be issued without stalling.

Anything to do with the current position of the instructions should be handled by the caller (presumably MachineScheduler or some other scheduler implementation).

https://github.com/llvm/llvm-project/pull/74088