#define DEBUG_TYPE "regalloc"
#include "LiveIntervalUnion.h"
+#include "llvm/ADT/SparseBitVector.h"
+#include "llvm/CodeGen/MachineLoopRanges.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+
#include <algorithm>
+
using namespace llvm;
+
// Merge a LiveInterval's segments. Guarantee no overlaps.
-//
-// Consider coalescing adjacent segments to save space, even though it makes
-// extraction more complicated.
-void LiveIntervalUnion::unify(LiveInterval &lvr) {
- // Add this live virtual register to the union
- LiveVirtRegs::iterator pos = std::upper_bound(lvrs_.begin(), lvrs_.end(),
- &lvr, less_ptr<LiveInterval>());
- assert((pos == lvrs_.end() || *pos != &lvr) && "duplicate LVR insertion");
- lvrs_.insert(pos, &lvr);
- // Insert each of the virtual register's live segments into the map
- SegmentIter segPos = segments_.begin();
- for (LiveInterval::iterator lvrI = lvr.begin(), lvrEnd = lvr.end();
- lvrI != lvrEnd; ++lvrI ) {
- LiveSegment segment(lvrI->start, lvrI->end, lvr);
- segPos = segments_.insert(segPos, segment);
- assert(*segPos == segment && "need equal val for equal key");
-#ifndef NDEBUG
- // check for overlap (inductively)
- if (segPos != segments_.begin()) {
- SegmentIter prevPos = segPos;
- --prevPos;
- assert(prevPos->end <= segment.start && "overlapping segments" );
- }
- SegmentIter nextPos = segPos;
- ++nextPos;
- if (nextPos != segments_.end())
- assert(segment.end <= nextPos->start && "overlapping segments" );
-#endif // NDEBUG
+void LiveIntervalUnion::unify(LiveInterval &VirtReg) {
+ if (VirtReg.empty())
+ return;
+ ++Tag;
+
+ // Insert each of the virtual register's live segments into the map.
+ LiveInterval::iterator RegPos = VirtReg.begin();
+ LiveInterval::iterator RegEnd = VirtReg.end();
+ SegmentIter SegPos = Segments.find(RegPos->start);
+
+ while (SegPos.valid()) {
+ SegPos.insert(RegPos->start, RegPos->end, &VirtReg);
+ if (++RegPos == RegEnd)
+ return;
+ SegPos.advanceTo(RegPos->start);
}
+
+ // We have reached the end of Segments, so it is no longer necessary to search
+ // for the insertion position.
+ // It is faster to insert the end first.
+ --RegEnd;
+ SegPos.insert(RegEnd->start, RegEnd->end, &VirtReg);
+ for (; RegPos != RegEnd; ++RegPos, ++SegPos)
+ SegPos.insert(RegPos->start, RegPos->end, &VirtReg);
}
-// Low-level helper to find the first segment in the range [segI,segEnd) that
-// intersects with a live virtual register segment, or segI.start >= lvr.end
-//
-// This logic is tied to the underlying LiveSegments data structure. For now, we
-// use a binary search within the vector to find the nearest starting position,
-// then reverse iterate to find the first overlap.
-//
-// Upon entry we have segI.start < lvrSeg.end
-// seg |--...
-// \ .
-// lvr ...-|
-//
-// After binary search, we have segI.start >= lvrSeg.start:
-// seg |--...
-// /
-// lvr |--...
-//
-// Assuming intervals are disjoint, if an intersection exists, it must be the
-// segment found or immediately behind it. We continue reverse iterating to
-// return the first overlap.
-typedef LiveIntervalUnion::SegmentIter SegmentIter;
-static SegmentIter upperBound(SegmentIter segBegin,
- SegmentIter segEnd,
- const LiveRange &lvrSeg) {
- assert(lvrSeg.end > segBegin->start && "segment iterator precondition");
- // get the next LIU segment such that setg.start is not less than
- // lvrSeg.start
- SegmentIter segI = std::upper_bound(segBegin, segEnd, lvrSeg.start);
- while (segI != segBegin) {
- --segI;
- if (lvrSeg.start >= segI->end)
- return ++segI;
+// Remove a live virtual register's segments from this union.
+void LiveIntervalUnion::extract(LiveInterval &VirtReg) {
+ if (VirtReg.empty())
+ return;
+ ++Tag;
+
+ // Remove each of the virtual register's live segments from the map.
+ LiveInterval::iterator RegPos = VirtReg.begin();
+ LiveInterval::iterator RegEnd = VirtReg.end();
+ SegmentIter SegPos = Segments.find(RegPos->start);
+
+ for (;;) {
+ assert(SegPos.value() == &VirtReg && "Inconsistent LiveInterval");
+ SegPos.erase();
+ if (!SegPos.valid())
+ return;
+
+ // Skip all segments that may have been coalesced.
+ RegPos = VirtReg.advanceTo(RegPos, SegPos.start());
+ if (RegPos == RegEnd)
+ return;
+
+ SegPos.advanceTo(RegPos->start);
}
- return segI;
}
-// Private interface accessed by Query.
+void
+LiveIntervalUnion::print(raw_ostream &OS, const TargetRegisterInfo *TRI) const {
+ OS << "LIU " << PrintReg(RepReg, TRI);
+ if (empty()) {
+ OS << " empty\n";
+ return;
+ }
+ for (LiveSegments::const_iterator SI = Segments.begin(); SI.valid(); ++SI) {
+ OS << " [" << SI.start() << ' ' << SI.stop() << "):"
+ << PrintReg(SI.value()->reg, TRI);
+ }
+ OS << '\n';
+}
+
+#ifndef NDEBUG
+// Verify the live intervals in this union and add them to the visited set.
+void LiveIntervalUnion::verify(LiveVirtRegBitSet& VisitedVRegs) {
+ for (SegmentIter SI = Segments.begin(); SI.valid(); ++SI)
+ VisitedVRegs.set(SI.value()->reg);
+}
+#endif //!NDEBUG
+
+// Scan the vector of interfering virtual registers in this union. Assume it's
+// quite small.
+bool LiveIntervalUnion::Query::isSeenInterference(LiveInterval *VirtReg) const {
+ SmallVectorImpl<LiveInterval*>::const_iterator I =
+ std::find(InterferingVRegs.begin(), InterferingVRegs.end(), VirtReg);
+ return I != InterferingVRegs.end();
+}
+
+// Collect virtual registers in this union that interfere with this
+// query's live virtual register.
//
-// Find a pair of segments that intersect, one in the live virtual register
-// (LiveInterval), and the other in this LiveIntervalUnion. The caller (Query)
-// is responsible for advancing the LiveIntervalUnion segments to find a
-// "notable" intersection, which requires query-specific logic.
-//
-// This design assumes only a fast mechanism for intersecting a single live
-// virtual register segment with a set of LiveIntervalUnion segments. This may
-// be ok since most LVRs have very few segments. If we had a data
-// structure that optimizd MxN intersection of segments, then we would bypass
-// the loop that advances within the LiveInterval.
+// The query state is one of:
//
-// If no intersection exists, set lvrI = lvrEnd, and set segI to the first
-// segment whose start point is greater than LiveInterval's end point.
+// 1. CheckedFirstInterference == false: Iterators are uninitialized.
+// 2. SeenAllInterferences == true: InterferingVRegs complete, iterators unused.
+// 3. Iterators left at the last seen intersection.
//
-// Assumes that segments are sorted by start position in both
-// LiveInterval and LiveSegments.
-void LiveIntervalUnion::Query::findIntersection(InterferenceResult &ir) const {
- LiveInterval::iterator lvrEnd = lvr_.end();
- SegmentIter liuEnd = liu_.end();
- while (ir.liuSegI_ != liuEnd) {
- // Slowly advance the live virtual reg iterator until we surpass the next
- // segment in this union. If this is ever used for coalescing of fixed
- // registers and we have a LiveInterval with thousands of segments, then use
- // upper bound instead.
- while (ir.lvrSegI_ != lvrEnd && ir.lvrSegI_->end <= ir.liuSegI_->start)
- ++ir.lvrSegI_;
- if (ir.lvrSegI_ == lvrEnd)
- break;
- // lvrSegI_ may have advanced far beyond liuSegI_,
- // do a fast intersection test to "catch up"
- ir.liuSegI_ = upperBound(ir.liuSegI_, liuEnd, *ir.lvrSegI_);
- // Check if no liuSegI_ exists with lvrSegI_->start < liuSegI_.end
- if (ir.liuSegI_ == liuEnd)
- break;
- if (ir.liuSegI_->start < ir.lvrSegI_->end) {
- assert(overlap(*ir.lvrSegI_, *ir.liuSegI_) && "upperBound postcondition");
- break;
+unsigned LiveIntervalUnion::Query::
+collectInterferingVRegs(unsigned MaxInterferingRegs) {
+ // Fast path return if we already have the desired information.
+ if (SeenAllInterferences || InterferingVRegs.size() >= MaxInterferingRegs)
+ return InterferingVRegs.size();
+
+ // Set up iterators on the first call.
+ if (!CheckedFirstInterference) {
+ CheckedFirstInterference = true;
+
+ // Quickly skip interference check for empty sets.
+ if (VirtReg->empty() || LiveUnion->empty()) {
+ SeenAllInterferences = true;
+ return 0;
}
+
+ // In most cases, the union will start before VirtReg.
+ VirtRegI = VirtReg->begin();
+ LiveUnionI.setMap(LiveUnion->getMap());
+ LiveUnionI.find(VirtRegI->start);
}
- if (ir.liuSegI_ == liuEnd)
- ir.lvrSegI_ = lvrEnd;
-}
-// Find the first intersection, and cache interference info
-// (retain segment iterators into both lvr_ and liu_).
-LiveIntervalUnion::InterferenceResult
-LiveIntervalUnion::Query::firstInterference() {
- if (firstInterference_ != LiveIntervalUnion::InterferenceResult()) {
- return firstInterference_;
+ LiveInterval::iterator VirtRegEnd = VirtReg->end();
+ LiveInterval *RecentReg = 0;
+ while (LiveUnionI.valid()) {
+ assert(VirtRegI != VirtRegEnd && "Reached end of VirtReg");
+
+ // Check for overlapping interference.
+ while (VirtRegI->start < LiveUnionI.stop() &&
+ VirtRegI->end > LiveUnionI.start()) {
+ // This is an overlap, record the interfering register.
+ LiveInterval *VReg = LiveUnionI.value();
+ if (VReg != RecentReg && !isSeenInterference(VReg)) {
+ RecentReg = VReg;
+ InterferingVRegs.push_back(VReg);
+ if (InterferingVRegs.size() >= MaxInterferingRegs)
+ return InterferingVRegs.size();
+ }
+ // This LiveUnion segment is no longer interesting.
+ if (!(++LiveUnionI).valid()) {
+ SeenAllInterferences = true;
+ return InterferingVRegs.size();
+ }
+ }
+
+ // The iterators are now not overlapping, LiveUnionI has been advanced
+ // beyond VirtRegI.
+ assert(VirtRegI->end <= LiveUnionI.start() && "Expected non-overlap");
+
+ // Advance the iterator that ends first.
+ VirtRegI = VirtReg->advanceTo(VirtRegI, LiveUnionI.start());
+ if (VirtRegI == VirtRegEnd)
+ break;
+
+ // Detect overlap, handle above.
+ if (VirtRegI->start < LiveUnionI.stop())
+ continue;
+
+ // Still not overlapping. Catch up LiveUnionI.
+ LiveUnionI.advanceTo(VirtRegI->start);
}
- firstInterference_ = InterferenceResult(lvr_.begin(), liu_.begin());
- findIntersection(firstInterference_);
- return firstInterference_;
+ SeenAllInterferences = true;
+ return InterferingVRegs.size();
}
-// Treat the result as an iterator and advance to the next interfering pair
-// of segments. This is a plain iterator with no filter.
-bool LiveIntervalUnion::Query::nextInterference(InterferenceResult &ir) const {
- assert(isInterference(ir) && "iteration past end of interferences");
- // Advance either the lvr or liu segment to ensure that we visit all unique
- // overlapping pairs.
- if (ir.lvrSegI_->end < ir.liuSegI_->end) {
- if (++ir.lvrSegI_ == lvr_.end())
+bool LiveIntervalUnion::Query::checkLoopInterference(MachineLoopRange *Loop) {
+ // VirtReg is likely live throughout the loop, so start by checking LIU-Loop
+ // overlaps.
+ IntervalMapOverlaps<LiveIntervalUnion::Map, MachineLoopRange::Map>
+ Overlaps(LiveUnion->getMap(), Loop->getMap());
+ if (!Overlaps.valid())
+ return false;
+
+ // The loop is overlapping an LIU assignment. Check VirtReg as well.
+ LiveInterval::iterator VRI = VirtReg->find(Overlaps.start());
+
+ for (;;) {
+ if (VRI == VirtReg->end())
return false;
- }
- else {
- if (++ir.liuSegI_ == liu_.end()) {
- ir.lvrSegI_ = lvr_.end();
+ if (VRI->start < Overlaps.stop())
+ return true;
+
+ Overlaps.advanceTo(VRI->start);
+ if (!Overlaps.valid())
return false;
- }
+ if (Overlaps.start() < VRI->end)
+ return true;
+
+ VRI = VirtReg->advanceTo(VRI, Overlaps.start());
}
- if (overlap(*ir.lvrSegI_, *ir.liuSegI_))
- return true;
- // find the next intersection
- findIntersection(ir);
- return isInterference(ir);
}