[LLVMdev] MC Register mapping question (MCRegUnitIterator )

[Arnold Schwaighofer]

The code in collectRanges() does:

      // Collect ranges for register units. These live ranges are computed on
      // demand, so just skip any that haven't been computed yet.
      if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
        for (MCRegUnitIterator Units(Reg, &TRI); Units.isValid(); ++Units)
          if (LiveInterval *LI = LIS.getCachedRegUnit(*Units))
            collectRanges(MO, LI, Entering, Internal, Exiting, OldIdx);
      } else {
        // Collect ranges for individual virtual registers.
        collectRanges(MO, &LIS.getInterval(Reg),
                      Entering, Internal, Exiting, OldIdx);
      }

As an experiment, you could replace getCachedRegUnit with getRegUnit
(the uncached version) to make verify we don't have a stale state in
the cache.


On Thu, Aug 30, 2012 at 3:01 PM, Sergei Larin <slarin at codeaurora.org> wrote:
> Arnold,
>
>    It is not my code per say - this is what is done in
> LiveIntervalAnalysis.cpp collectRanges(), it wants to iterate over "units"
> of D1 (whatever they are assumed to be), but right there it associates them
> with actual physical register live ranges (see the tread below), and it does
> it wrongly. I was trying to pinpoint exactly to where the issue is, but
> there are too many  interdependent links in this chain, so I am seeking some
> domain knowledge :)