[llvm] r210390 - Fix the MachineScheduler's logic for updating ready times for in-order.

[WenHan Gu (谷汶翰)]

Hi Andrew,

AFAIK, ReadyCycle - CurrCycle is not always >= 0,  (I use assert
(ReadyCycle>= CurrCycle) to check)
but these are unsigned types so will be underflow. (Sometimes, I got 2^32-x
on MaxObservedStall)

I suggest maybe we should use signed temp var for this calculation?
Thanks!


>  void SchedBoundary::releaseNode(SUnit *SU, unsigned ReadyCycle) {
> +  assert(SU->getInstr() && "Scheduled SUnit must have instr");
> +
> +#ifndef NDEBUG
> +  MaxObservedStall = std::max(ReadyCycle - CurrCycle, MaxObservedStall);
> +#endif
> +
>    if (ReadyCycle < MinReadyCycle)
>      MinReadyCycle = ReadyCycle;
>
>
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