[llvm-commits] PATCH: Fix quadratic behavior in PR12652

[Chandler Carruth]

FYI, done. ;] I'll save attaching a brand new patch.


On Fri, Jul 6, 2012 at 1:57 AM, Benjamin Kramer <benny.kra at gmail.com> wrote:

>
> On 06.07.2012, at 10:28, Chandler Carruth wrote:
>
> > diff --git a/lib/CodeGen/LiveInterval.cpp b/lib/CodeGen/LiveInterval.cpp
> > index 3d34c08..54d120a 100644
> > --- a/lib/CodeGen/LiveInterval.cpp
> > +++ b/lib/CodeGen/LiveInterval.cpp
> > @@ -458,44 +458,94 @@ void LiveInterval::join(LiveInterval &Other,
> >    }
> >  }
> >
> > +/// \brief Helper function for merging in another LiveInterval's ranges.
> > +///
> > +/// This is a helper routine implementing an efficient merge of another
> > +/// LiveIntervals ranges into the current interval. It accepts an
> optional
> > +/// value number constraint for the RHS, and a new value number to
> assign to
> > +/// each range merged into the interval.
> > +void LiveInterval::mergeIntervalRanges(const LiveInterval &RHS,
> > +                                       VNInfo *LHSValNo,
> > +                                       const VNInfo *RHSValNo) {
> > +  if (RHS.begin() == RHS.end())
> > +    return;
> > +
> > +  SmallVector<LiveRange, 4> NewRanges;
> > +  const_iterator LI = begin(), LE = end(), RI = RHS.begin(), RE =
> RHS.end();
> > +  while (true) {
> > +    if (LI == LE) {
> > +      for (; RI != RE; ++RI)
> > +        if (!RHSValNo || RI->valno == RHSValNo) {
> > +          NewRanges.push_back(*RI);
> > +          NewRanges.back().valno = LHSValNo;
> > +        }
> > +      break;
> > +    }
> > +    if (RI == RE) {
> > +      std::copy(LI, LE, std::back_inserter(NewRanges));
>
> NewRanges.append(LI, LE) would be cleaner.
>
> - Ben
>
> > +      break;
> > +    }
> > +    assert(LI != LE && RI != RE);
> > +
> > +    // Skip incoming ranges with the wrong value.
> > +    if (RHSValNo && RI->valno != RHSValNo) {
> > +      ++RI;
> > +      continue;
> > +    }
> > +
> > +    // Select the first range. We pick the earliest start point, and
> then the
> > +    // largest range.
> > +    bool MergeRight = *RI < *LI;
> > +    LiveRange R = MergeRight ? *RI : *LI;
> > +    if (MergeRight)
> > +      R.valno = LHSValNo;
> > +    ++(MergeRight ? RI : LI);
> > +
> > +    // Check if we have any ranges that this one might merge with.
> > +    if (!NewRanges.empty()) {
> > +      LiveRange &LastR = NewRanges.back();
> > +      if (R.valno == LastR.valno) {
> > +        // Try to merge this range into the last one.
> > +        if (R.start <= LastR.end) {
> > +          LastR.end = std::max(LastR.end, R.end);
> > +          continue;
> > +        }
> > +      } else {
> > +        // We can't merge ranges across a value number.
> > +        assert(R.start >= LastR.end &&
> > +               "Cannot overlap two LiveRanges with differing ValID's"
> > +               " (did you def the same reg twice in a MachineInstr?)");
> > +      }
> > +    }
> > +
> > +    // If all else fails, just append the range.
> > +    NewRanges.push_back(R);
> > +  }
> > +
> > +  // Swap the new ranges with our current ranges.
> > +  NewRanges.swap(ranges);
> > +}
> > +
>
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