//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "regalloc"
-#include "LiveIntervalUnion.h"
+#include "llvm/CodeGen/LiveIntervalUnion.h"
#include "llvm/ADT/SparseBitVector.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetRegisterInfo.h"
#include <algorithm>
+
using namespace llvm;
-// Find the first segment in the range [segBegin,segments_.end()) that
-// intersects with seg. If no intersection is found, return the first segI
-// such that segI.start >= seg.end
-//
-// This logic is tied to the underlying LiveSegments data structure. For now, we
-// use set::upper_bound to find the nearest starting position,
-// then reverse iterate to find the first overlap.
-//
-// Upon entry we have segBegin.start < seg.end
-// seg |--...
-// \ .
-// lvr ...-|
-//
-// After set::upper_bound, we have segI.start >= seg.start:
-// seg |--...
-// /
-// lvr |--...
-//
-// Assuming intervals are disjoint, if an intersection exists, it must be the
-// segment found or the one immediately preceeding it. We continue reverse
-// iterating to return the first overlapping segment.
-LiveIntervalUnion::SegmentIter
-LiveIntervalUnion::upperBound(SegmentIter segBegin,
- const LiveSegment &seg) {
- assert(seg.end > segBegin->start && "segment iterator precondition");
- // get the next LIU segment such that segI->start is not less than seg.start
- //
- // FIXME: Once we have a B+tree, we can make good use of segBegin as a hint to
- // upper_bound. For now, we're forced to search again from the root each time.
- SegmentIter segI = segments_.upper_bound(seg);
- while (segI != segBegin) {
- --segI;
- if (seg.start >= segI->end)
- return ++segI;
- }
- return segI;
-}
+#define DEBUG_TYPE "regalloc"
+
// 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) {
- // 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()) {
- assert(llvm::prior(segPos)->end <= segment.start &&
- "overlapping segments" );
- }
- SegmentIter nextPos = llvm::next(segPos);
- if (nextPos != segments_.end())
- assert(segment.end <= nextPos->start && "overlapping segments" );
-#endif // NDEBUG
+void LiveIntervalUnion::unify(LiveInterval &VirtReg, const LiveRange &Range) {
+ if (Range.empty())
+ return;
+ ++Tag;
+
+ // Insert each of the virtual register's live segments into the map.
+ LiveRange::const_iterator RegPos = Range.begin();
+ LiveRange::const_iterator RegEnd = Range.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);
}
// Remove a live virtual register's segments from this union.
-void LiveIntervalUnion::extract(const LiveInterval &lvr) {
+void LiveIntervalUnion::extract(LiveInterval &VirtReg, const LiveRange &Range) {
+ if (Range.empty())
+ return;
+ ++Tag;
+
// Remove each of the virtual register's live segments from the map.
- SegmentIter segPos = segments_.begin();
- for (LiveInterval::const_iterator lvrI = lvr.begin(), lvrEnd = lvr.end();
- lvrI != lvrEnd; ++lvrI) {
- LiveSegment seg(lvrI->start, lvrI->end, const_cast<LiveInterval*>(&lvr));
- segPos = upperBound(segPos, seg);
- assert(segPos != segments_.end() && "missing lvr segment");
- segments_.erase(segPos++);
- }
-}
+ LiveRange::const_iterator RegPos = Range.begin();
+ LiveRange::const_iterator RegEnd = Range.end();
+ SegmentIter SegPos = Segments.find(RegPos->start);
-raw_ostream& llvm::operator<<(raw_ostream& os, const LiveSegment &ls) {
- return os << '[' << ls.start << ',' << ls.end << ':' <<
- ls.liveVirtReg->reg << ")";
-}
+ for (;;) {
+ assert(SegPos.value() == &VirtReg && "Inconsistent LiveInterval");
+ SegPos.erase();
+ if (!SegPos.valid())
+ return;
+
+ // Skip all segments that may have been coalesced.
+ RegPos = Range.advanceTo(RegPos, SegPos.start());
+ if (RegPos == RegEnd)
+ return;
-void LiveSegment::dump() const {
- dbgs() << *this << "\n";
+ SegPos.advanceTo(RegPos->start);
+ }
}
void
-LiveIntervalUnion::print(raw_ostream &os,
- const AbstractRegisterDescription *rdesc) const {
- os << "LIU ";
- if (rdesc != NULL)
- os << rdesc->getName(repReg_);
- else {
- os << repReg_;
+LiveIntervalUnion::print(raw_ostream &OS, const TargetRegisterInfo *TRI) const {
+ if (empty()) {
+ OS << " empty\n";
+ return;
}
- for (LiveSegments::const_iterator segI = segments_.begin(),
- segEnd = segments_.end(); segI != segEnd; ++segI) {
- dbgs() << " " << *segI;
+ for (LiveSegments::const_iterator SI = Segments.begin(); SI.valid(); ++SI) {
+ OS << " [" << SI.start() << ' ' << SI.stop() << "):"
+ << PrintReg(SI.value()->reg, TRI);
}
- os << "\n";
-}
-
-void LiveIntervalUnion::dump(const AbstractRegisterDescription *rdesc) const {
- print(dbgs(), rdesc);
+ OS << '\n';
}
#ifndef NDEBUG
// Verify the live intervals in this union and add them to the visited set.
-void LiveIntervalUnion::verify(LvrBitSet& visitedVRegs) {
- SegmentIter segI = segments_.begin();
- SegmentIter segEnd = segments_.end();
- if (segI == segEnd) return;
- visitedVRegs.set(segI->liveVirtReg->reg);
- for (++segI; segI != segEnd; ++segI) {
- visitedVRegs.set(segI->liveVirtReg->reg);
- assert(llvm::prior(segI)->end <= segI->start && "overlapping segments" );
- }
+void LiveIntervalUnion::verify(LiveVirtRegBitSet& VisitedVRegs) {
+ for (SegmentIter SI = Segments.begin(); SI.valid(); ++SI)
+ VisitedVRegs.set(SI.value()->reg);
}
#endif //!NDEBUG
-// Private interface accessed by Query.
+// 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"
- LiveSegment seg(ir.lvrSegI_->start, ir.lvrSegI_->end, lvr_);
- ir.liuSegI_ = liu_->upperBound(ir.liuSegI_, seg);
- // 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;
}
- }
- 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_;
+ // In most cases, the union will start before VirtReg.
+ VirtRegI = VirtReg->begin();
+ LiveUnionI.setMap(LiveUnion->getMap());
+ LiveUnionI.find(VirtRegI->start);
}
- firstInterference_ = InterferenceResult(lvr_->begin(), liu_->begin());
- findIntersection(firstInterference_);
- return firstInterference_;
-}
-// 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())
- return false;
- }
- else {
- if (++ir.liuSegI_ == liu_->end()) {
- ir.lvrSegI_ = lvr_->end();
- return false;
+ LiveInterval::iterator VirtRegEnd = VirtReg->end();
+ LiveInterval *RecentReg = nullptr;
+ 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);
}
- if (overlap(*ir.lvrSegI_, *ir.liuSegI_))
- return true;
- // find the next intersection
- findIntersection(ir);
- return isInterference(ir);
+ SeenAllInterferences = true;
+ return InterferingVRegs.size();
+}
+
+void LiveIntervalUnion::Array::init(LiveIntervalUnion::Allocator &Alloc,
+ unsigned NSize) {
+ // Reuse existing allocation.
+ if (NSize == Size)
+ return;
+ clear();
+ Size = NSize;
+ LIUs = static_cast<LiveIntervalUnion*>(
+ malloc(sizeof(LiveIntervalUnion)*NSize));
+ for (unsigned i = 0; i != Size; ++i)
+ new(LIUs + i) LiveIntervalUnion(Alloc);
+}
+
+void LiveIntervalUnion::Array::clear() {
+ if (!LIUs)
+ return;
+ for (unsigned i = 0; i != Size; ++i)
+ LIUs[i].~LiveIntervalUnion();
+ free(LIUs);
+ Size = 0;
+ LIUs = nullptr;
}
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