verify();
}
-/// MergeRangesInAsValue - Merge all of the intervals in RHS into this live
-/// interval as the specified value number. The LiveRanges in RHS are
-/// allowed to overlap with LiveRanges in the current interval, but only if
-/// the overlapping LiveRanges have the specified value number.
-void LiveInterval::MergeRangesInAsValue(const LiveInterval &RHS,
- VNInfo *LHSValNo) {
+/// \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.
+///
+/// \param LHSValNo Set as the new value number for every range from RHS which
+/// is merged into the LHS.
+/// \param RHSValNo If non-NULL, then only ranges in RHS whose original value
+/// number maches this value number will be merged into LHS.
+void LiveInterval::mergeIntervalRanges(const LiveInterval &RHS,
+ VNInfo *LHSValNo,
+ const VNInfo *RHSValNo) {
+ if (RHS.empty())
+ return;
+
+ // Ensure we're starting with valid ranges.
verify();
RHS.verify();
- // TODO: Make this more efficient.
- iterator InsertPos = begin();
- for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
- // Map the valno in the other live range to the current live range.
- LiveRange Tmp = *I;
- Tmp.valno = LHSValNo;
- InsertPos = addRangeFrom(Tmp, InsertPos);
+ // The strategy for merging these efficiently is as follows:
+ //
+ // 1) Find the beginning of the impacted ranges in the LHS.
+ // 2) Create a new, merged sub-squence of ranges merging from the position in
+ // #1 until either LHS or RHS is exhausted. Any part of LHS between RHS
+ // entries being merged will be copied into this new range.
+ // 3) Replace the relevant section in LHS with these newly merged ranges.
+ // 4) Append any remaning ranges from RHS if LHS is exhausted in #2.
+ //
+ // We don't follow the typical in-place merge strategy for sorted ranges of
+ // appending the new ranges to the back and then using std::inplace_merge
+ // because one step of the merge can both mutate the original elements and
+ // remove elements from the original. Essentially, because the merge includes
+ // collapsing overlapping ranges, a more complex approach is required.
+
+ // We do an initial binary search to optimize for a common pattern: a large
+ // LHS, and a very small RHS.
+ const_iterator RI = RHS.begin(), RE = RHS.end();
+ iterator LE = end(), LI = std::upper_bound(begin(), LE, *RI);
+
+ // Merge into NewRanges until one of the ranges is exhausted.
+ SmallVector<LiveRange, 4> NewRanges;
+
+ // Keep track of where to begin the replacement.
+ iterator ReplaceI = LI;
+
+ // If there are preceding ranges in the LHS, put the last one into NewRanges
+ // so we can optionally extend it. Adjust the replacement point accordingly.
+ if (LI != begin()) {
+ ReplaceI = llvm::prior(LI);
+ NewRanges.push_back(*ReplaceI);
}
+ // Now loop over the mergable portions of both LHS and RHS, merging into
+ // NewRanges.
+ while (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.
+ LiveRange R = *LI;
+ if (*RI < R) {
+ R = *RI;
+ ++RI;
+ R.valno = LHSValNo;
+ } else {
+ ++LI;
+ }
+
+ if (NewRanges.empty()) {
+ NewRanges.push_back(R);
+ continue;
+ }
+
+ 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");
+ }
+
+ // If all else fails, just append the range.
+ NewRanges.push_back(R);
+ }
+ assert(RI == RE || LI == LE);
+
+ // Check for being able to merge into the trailing sequence of ranges on the LHS.
+ if (!NewRanges.empty())
+ for (; LI != LE && (LI->valno == NewRanges.back().valno &&
+ LI->start <= NewRanges.back().end);
+ ++LI)
+ NewRanges.back().end = std::max(NewRanges.back().end, LI->end);
+
+ // Replace the ranges in the LHS with the newly merged ones. It would be
+ // really nice if there were a move-supporting 'replace' directly in
+ // SmallVector, but as there is not, we pay the price of copies to avoid
+ // wasted memory allocations.
+ SmallVectorImpl<LiveRange>::iterator NRI = NewRanges.begin(),
+ NRE = NewRanges.end();
+ for (; ReplaceI != LI && NRI != NRE; ++ReplaceI, ++NRI)
+ *ReplaceI = *NRI;
+ if (NRI == NRE)
+ ranges.erase(ReplaceI, LI);
+ else
+ ranges.insert(LI, NRI, NRE);
+
+ // And finally insert any trailing end of RHS (if we have one).
+ for (; RI != RE; ++RI)
+ if (ranges.back().valno == LHSValNo && RI->start <= ranges.back().end) {
+ ranges.back().end = std::max(ranges.back().end, RI->end);
+ } else {
+ ranges.push_back(*RI);
+ ranges.back().valno = LHSValNo;
+ }
+
+ // Ensure we finished with a valid new sequence of ranges.
verify();
}
+/// MergeRangesInAsValue - Merge all of the intervals in RHS into this live
+/// interval as the specified value number. The LiveRanges in RHS are
+/// allowed to overlap with LiveRanges in the current interval, but only if
+/// the overlapping LiveRanges have the specified value number.
+void LiveInterval::MergeRangesInAsValue(const LiveInterval &RHS,
+ VNInfo *LHSValNo) {
+ mergeIntervalRanges(RHS, LHSValNo);
+}
/// MergeValueInAsValue - Merge all of the live ranges of a specific val#
/// in RHS into this live interval as the specified value number.
/// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
/// current interval, it will replace the value numbers of the overlaped
/// live ranges with the specified value number.
-void LiveInterval::MergeValueInAsValue(
- const LiveInterval &RHS,
- const VNInfo *RHSValNo, VNInfo *LHSValNo) {
- verify();
- RHS.verify();
-
- // TODO: Make this more efficient.
- iterator InsertPos = begin();
- for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
- if (I->valno != RHSValNo)
- continue;
- // Map the valno in the other live range to the current live range.
- LiveRange Tmp = *I;
- Tmp.valno = LHSValNo;
- InsertPos = addRangeFrom(Tmp, InsertPos);
- }
-
- verify();
+void LiveInterval::MergeValueInAsValue(const LiveInterval &RHS,
+ const VNInfo *RHSValNo,
+ VNInfo *LHSValNo) {
+ mergeIntervalRanges(RHS, LHSValNo, RHSValNo);
}
-
/// MergeValueNumberInto - This method is called when two value nubmers
/// are found to be equivalent. This eliminates V1, replacing all
/// LiveRanges with the V1 value number with the V2 value number. This can
projects / oota-llvm.git / commitdiff