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//===-- LiveInterval.cpp - Live Interval Representation -------------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements the LiveRange and LiveInterval classes. Given some // numbering of each the machine instructions an interval [i, j) is said to be a // live interval for register v if there is no instruction with number j' > j // such that v is live at j' and there is no instruction with number i' < i such // that v is live at i'. In this implementation intervals can have holes, // i.e. an interval might look like [1,20), [50,65), [1000,1001). Each // individual range is represented as an instance of LiveRange, and the whole // interval is represented as an instance of LiveInterval. // //===----------------------------------------------------------------------===// #include "llvm/CodeGen/LiveInterval.h" #include "llvm/CodeGen/LiveIntervalAnalysis.h" #include "llvm/CodeGen/MachineRegisterInfo.h" #include "llvm/ADT/DenseMap.h" #include "llvm/ADT/SmallSet.h" #include "llvm/ADT/STLExtras.h" #include "llvm/Support/Debug.h" #include "llvm/Support/raw_ostream.h" #include "llvm/Target/TargetRegisterInfo.h" #include <algorithm> using namespace llvm; LiveInterval::iterator LiveInterval::find(SlotIndex Pos) { // This algorithm is basically std::upper_bound. // Unfortunately, std::upper_bound cannot be used with mixed types until we // adopt C++0x. Many libraries can do it, but not all. if (empty() || Pos >= endIndex()) return end(); iterator I = begin(); size_t Len = ranges.size(); do { size_t Mid = Len >> 1; if (Pos < I[Mid].end) Len = Mid; else I += Mid + 1, Len -= Mid + 1; } while (Len); return I; } /// killedInRange - Return true if the interval has kills in [Start,End). bool LiveInterval::killedInRange(SlotIndex Start, SlotIndex End) const { Ranges::const_iterator r = std::lower_bound(ranges.begin(), ranges.end(), End); // Now r points to the first interval with start >= End, or ranges.end(). if (r == ranges.begin()) return false; --r; // Now r points to the last interval with end <= End. // r->end is the kill point. return r->end >= Start && r->end < End; } // overlaps - Return true if the intersection of the two live intervals is // not empty. // // An example for overlaps(): // // 0: A = ... // 4: B = ... // 8: C = A + B ;; last use of A // // The live intervals should look like: // // A = [3, 11) // B = [7, x) // C = [11, y) // // A->overlaps(C) should return false since we want to be able to join // A and C. // bool LiveInterval::overlapsFrom(const LiveInterval& other, const_iterator StartPos) const { assert(!empty() && "empty interval"); const_iterator i = begin(); const_iterator ie = end(); const_iterator j = StartPos; const_iterator je = other.end(); assert((StartPos->start <= i->start || StartPos == other.begin()) && StartPos != other.end() && "Bogus start position hint!"); if (i->start < j->start) { i = std::upper_bound(i, ie, j->start); if (i != ranges.begin()) --i; } else if (j->start < i->start) { ++StartPos; if (StartPos != other.end() && StartPos->start <= i->start) { assert(StartPos < other.end() && i < end()); j = std::upper_bound(j, je, i->start); if (j != other.ranges.begin()) --j; } } else { return true; } if (j == je) return false; while (i != ie) { if (i->start > j->start) { std::swap(i, j); std::swap(ie, je); } if (i->end > j->start) return true; ++i; } return false; } /// overlaps - Return true if the live interval overlaps a range specified /// by [Start, End). bool LiveInterval::overlaps(SlotIndex Start, SlotIndex End) const { assert(Start < End && "Invalid range"); const_iterator I = std::lower_bound(begin(), end(), End); return I != begin() && (--I)->end > Start; } /// ValNo is dead, remove it. If it is the largest value number, just nuke it /// (and any other deleted values neighboring it), otherwise mark it as ~1U so /// it can be nuked later. void LiveInterval::markValNoForDeletion(VNInfo *ValNo) { if (ValNo->id == getNumValNums()-1) { do { valnos.pop_back(); } while (!valnos.empty() && valnos.back()->isUnused()); } else { ValNo->setIsUnused(true); } } /// RenumberValues - Renumber all values in order of appearance and delete the /// remaining unused values. void LiveInterval::RenumberValues(LiveIntervals &lis) { SmallPtrSet<VNInfo*, 8> Seen; valnos.clear(); for (const_iterator I = begin(), E = end(); I != E; ++I) { VNInfo *VNI = I->valno; if (!Seen.insert(VNI)) continue; assert(!VNI->isUnused() && "Unused valno used by live range"); VNI->id = (unsigned)valnos.size(); valnos.push_back(VNI); } } /// extendIntervalEndTo - This method is used when we want to extend the range /// specified by I to end at the specified endpoint. To do this, we should /// merge and eliminate all ranges that this will overlap with. The iterator is /// not invalidated. void LiveInterval::extendIntervalEndTo(Ranges::iterator I, SlotIndex NewEnd) { assert(I != ranges.end() && "Not a valid interval!"); VNInfo *ValNo = I->valno; // Search for the first interval that we can't merge with. Ranges::iterator MergeTo = llvm::next(I); for (; MergeTo != ranges.end() && NewEnd >= MergeTo->end; ++MergeTo) { assert(MergeTo->valno == ValNo && "Cannot merge with differing values!"); } // If NewEnd was in the middle of an interval, make sure to get its endpoint. I->end = std::max(NewEnd, prior(MergeTo)->end); // Erase any dead ranges. ranges.erase(llvm::next(I), MergeTo); // If the newly formed range now touches the range after it and if they have // the same value number, merge the two ranges into one range. Ranges::iterator Next = llvm::next(I); if (Next != ranges.end() && Next->start <= I->end && Next->valno == ValNo) { I->end = Next->end; ranges.erase(Next); } } /// extendIntervalStartTo - This method is used when we want to extend the range /// specified by I to start at the specified endpoint. To do this, we should /// merge and eliminate all ranges that this will overlap with. LiveInterval::Ranges::iterator LiveInterval::extendIntervalStartTo(Ranges::iterator I, SlotIndex NewStart) { assert(I != ranges.end() && "Not a valid interval!"); VNInfo *ValNo = I->valno; // Search for the first interval that we can't merge with. Ranges::iterator MergeTo = I; do { if (MergeTo == ranges.begin()) { I->start = NewStart; ranges.erase(MergeTo, I); return I; } assert(MergeTo->valno == ValNo && "Cannot merge with differing values!"); --MergeTo; } while (NewStart <= MergeTo->start); // If we start in the middle of another interval, just delete a range and // extend that interval. if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) { MergeTo->end = I->end; } else { // Otherwise, extend the interval right after. ++MergeTo; MergeTo->start = NewStart; MergeTo->end = I->end; } ranges.erase(llvm::next(MergeTo), llvm::next(I)); return MergeTo; } LiveInterval::iterator LiveInterval::addRangeFrom(LiveRange LR, iterator From) { SlotIndex Start = LR.start, End = LR.end; iterator it = std::upper_bound(From, ranges.end(), Start); // If the inserted interval starts in the middle or right at the end of // another interval, just extend that interval to contain the range of LR. if (it != ranges.begin()) { iterator B = prior(it); if (LR.valno == B->valno) { if (B->start <= Start && B->end >= Start) { extendIntervalEndTo(B, End); return B; } } else { // Check to make sure that we are not overlapping two live ranges with // different valno's. assert(B->end <= Start && "Cannot overlap two LiveRanges with differing ValID's" " (did you def the same reg twice in a MachineInstr?)"); } } // Otherwise, if this range ends in the middle of, or right next to, another // interval, merge it into that interval. if (it != ranges.end()) { if (LR.valno == it->valno) { if (it->start <= End) { it = extendIntervalStartTo(it, Start); // If LR is a complete superset of an interval, we may need to grow its // endpoint as well. if (End > it->end) extendIntervalEndTo(it, End); return it; } } else { // Check to make sure that we are not overlapping two live ranges with // different valno's. assert(it->start >= End && "Cannot overlap two LiveRanges with differing ValID's"); } } // Otherwise, this is just a new range that doesn't interact with anything. // Insert it. return ranges.insert(it, LR); } /// extendInBlock - If this interval is live before Kill in the basic /// block that starts at StartIdx, extend it to be live up to Kill and return /// the value. If there is no live range before Kill, return NULL. VNInfo *LiveInterval::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) { if (empty()) return 0; iterator I = std::upper_bound(begin(), end(), Kill.getPrevSlot()); if (I == begin()) return 0; --I; if (I->end <= StartIdx) return 0; if (I->end < Kill) extendIntervalEndTo(I, Kill); return I->valno; } /// removeRange - Remove the specified range from this interval. Note that /// the range must be in a single LiveRange in its entirety. void LiveInterval::removeRange(SlotIndex Start, SlotIndex End, bool RemoveDeadValNo) { // Find the LiveRange containing this span. Ranges::iterator I = find(Start); assert(I != ranges.end() && "Range is not in interval!"); assert(I->containsRange(Start, End) && "Range is not entirely in interval!"); // If the span we are removing is at the start of the LiveRange, adjust it. VNInfo *ValNo = I->valno; if (I->start == Start) { if (I->end == End) { if (RemoveDeadValNo) { // Check if val# is dead. bool isDead = true; for (const_iterator II = begin(), EE = end(); II != EE; ++II) if (II != I && II->valno == ValNo) { isDead = false; break; } if (isDead) { // Now that ValNo is dead, remove it. markValNoForDeletion(ValNo); } } ranges.erase(I); // Removed the whole LiveRange. } else I->start = End; return; } // Otherwise if the span we are removing is at the end of the LiveRange, // adjust the other way. if (I->end == End) { I->end = Start; return; } // Otherwise, we are splitting the LiveRange into two pieces. SlotIndex OldEnd = I->end; I->end = Start; // Trim the old interval. // Insert the new one. ranges.insert(llvm::next(I), LiveRange(End, OldEnd, ValNo)); } /// removeValNo - Remove all the ranges defined by the specified value#. /// Also remove the value# from value# list. void LiveInterval::removeValNo(VNInfo *ValNo) { if (empty()) return; Ranges::iterator I = ranges.end(); Ranges::iterator E = ranges.begin(); do { --I; if (I->valno == ValNo) ranges.erase(I); } while (I != E); // Now that ValNo is dead, remove it. markValNoForDeletion(ValNo); } /// findDefinedVNInfo - Find the VNInfo defined by the specified /// index (register interval). VNInfo *LiveInterval::findDefinedVNInfoForRegInt(SlotIndex Idx) const { for (LiveInterval::const_vni_iterator i = vni_begin(), e = vni_end(); i != e; ++i) { if ((*i)->def == Idx) return *i; } return 0; } /// join - Join two live intervals (this, and other) together. This applies /// mappings to the value numbers in the LHS/RHS intervals as specified. If /// the intervals are not joinable, this aborts. void LiveInterval::join(LiveInterval &Other, const int *LHSValNoAssignments, const int *RHSValNoAssignments, SmallVector<VNInfo*, 16> &NewVNInfo, MachineRegisterInfo *MRI) { // Determine if any of our live range values are mapped. This is uncommon, so // we want to avoid the interval scan if not. bool MustMapCurValNos = false; unsigned NumVals = getNumValNums(); unsigned NumNewVals = NewVNInfo.size(); for (unsigned i = 0; i != NumVals; ++i) { unsigned LHSValID = LHSValNoAssignments[i]; if (i != LHSValID || (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) { MustMapCurValNos = true; break; } } // If we have to apply a mapping to our base interval assignment, rewrite it // now. if (MustMapCurValNos) { // Map the first live range. iterator OutIt = begin(); OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]]; for (iterator I = next(OutIt), E = end(); I != E; ++I) { VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]]; assert(nextValNo != 0 && "Huh?"); // If this live range has the same value # as its immediate predecessor, // and if they are neighbors, remove one LiveRange. This happens when we // have [0,4:0)[4,7:1) and map 0/1 onto the same value #. if (OutIt->valno == nextValNo && OutIt->end == I->start) { OutIt->end = I->end; } else { // Didn't merge. Move OutIt to the next interval, ++OutIt; OutIt->valno = nextValNo; if (OutIt != I) { OutIt->start = I->start; OutIt->end = I->end; } } } // If we merge some live ranges, chop off the end. ++OutIt; ranges.erase(OutIt, end()); } // Remember assignements because val# ids are changing. SmallVector<unsigned, 16> OtherAssignments; for (iterator I = Other.begin(), E = Other.end(); I != E; ++I) OtherAssignments.push_back(RHSValNoAssignments[I->valno->id]); // Update val# info. Renumber them and make sure they all belong to this // LiveInterval now. Also remove dead val#'s. unsigned NumValNos = 0; for (unsigned i = 0; i < NumNewVals; ++i) { VNInfo *VNI = NewVNInfo[i]; if (VNI) { if (NumValNos >= NumVals) valnos.push_back(VNI); else valnos[NumValNos] = VNI; VNI->id = NumValNos++; // Renumber val#. } } if (NumNewVals < NumVals) valnos.resize(NumNewVals); // shrinkify // Okay, now insert the RHS live ranges into the LHS. iterator InsertPos = begin(); unsigned RangeNo = 0; for (iterator I = Other.begin(), E = Other.end(); I != E; ++I, ++RangeNo) { // Map the valno in the other live range to the current live range. I->valno = NewVNInfo[OtherAssignments[RangeNo]]; assert(I->valno && "Adding a dead range?"); InsertPos = addRangeFrom(*I, InsertPos); } ComputeJoinedWeight(Other); } /// 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) { // 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); } } /// 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) { // 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); } } /// 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 /// cause merging of V1/V2 values numbers and compaction of the value space. VNInfo* LiveInterval::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) { assert(V1 != V2 && "Identical value#'s are always equivalent!"); // This code actually merges the (numerically) larger value number into the // smaller value number, which is likely to allow us to compactify the value // space. The only thing we have to be careful of is to preserve the // instruction that defines the result value. // Make sure V2 is smaller than V1. if (V1->id < V2->id) { V1->copyFrom(*V2); std::swap(V1, V2); } // Merge V1 live ranges into V2. for (iterator I = begin(); I != end(); ) { iterator LR = I++; if (LR->valno != V1) continue; // Not a V1 LiveRange. // Okay, we found a V1 live range. If it had a previous, touching, V2 live // range, extend it. if (LR != begin()) { iterator Prev = LR-1; if (Prev->valno == V2 && Prev->end == LR->start) { Prev->end = LR->end; // Erase this live-range. ranges.erase(LR); I = Prev+1; LR = Prev; } } // Okay, now we have a V1 or V2 live range that is maximally merged forward. // Ensure that it is a V2 live-range. LR->valno = V2; // If we can merge it into later V2 live ranges, do so now. We ignore any // following V1 live ranges, as they will be merged in subsequent iterations // of the loop. if (I != end()) { if (I->start == LR->end && I->valno == V2) { LR->end = I->end; ranges.erase(I); I = LR+1; } } } // Merge the relevant flags. V2->mergeFlags(V1); // Now that V1 is dead, remove it. markValNoForDeletion(V1); return V2; } void LiveInterval::Copy(const LiveInterval &RHS, MachineRegisterInfo *MRI, VNInfo::Allocator &VNInfoAllocator) { ranges.clear(); valnos.clear(); std::pair<unsigned, unsigned> Hint = MRI->getRegAllocationHint(RHS.reg); MRI->setRegAllocationHint(reg, Hint.first, Hint.second); weight = RHS.weight; for (unsigned i = 0, e = RHS.getNumValNums(); i != e; ++i) { const VNInfo *VNI = RHS.getValNumInfo(i); createValueCopy(VNI, VNInfoAllocator); } for (unsigned i = 0, e = RHS.ranges.size(); i != e; ++i) { const LiveRange &LR = RHS.ranges[i]; addRange(LiveRange(LR.start, LR.end, getValNumInfo(LR.valno->id))); } } unsigned LiveInterval::getSize() const { unsigned Sum = 0; for (const_iterator I = begin(), E = end(); I != E; ++I) Sum += I->start.distance(I->end); return Sum; } /// ComputeJoinedWeight - Set the weight of a live interval Joined /// after Other has been merged into it. void LiveInterval::ComputeJoinedWeight(const LiveInterval &Other) { // If either of these intervals was spilled, the weight is the // weight of the non-spilled interval. This can only happen with // iterative coalescers. if (Other.weight != HUGE_VALF) { weight += Other.weight; } else if (weight == HUGE_VALF && !TargetRegisterInfo::isPhysicalRegister(reg)) { // Remove this assert if you have an iterative coalescer assert(0 && "Joining to spilled interval"); weight = Other.weight; } else { // Otherwise the weight stays the same // Remove this assert if you have an iterative coalescer assert(0 && "Joining from spilled interval"); } } raw_ostream& llvm::operator<<(raw_ostream& os, const LiveRange &LR) { return os << '[' << LR.start << ',' << LR.end << ':' << LR.valno->id << ")"; } void LiveRange::dump() const { dbgs() << *this << "\n"; } void LiveInterval::print(raw_ostream &OS, const TargetRegisterInfo *TRI) const { OS << PrintReg(reg, TRI); if (weight != 0) OS << ',' << weight; if (empty()) OS << " EMPTY"; else { OS << " = "; for (LiveInterval::Ranges::const_iterator I = ranges.begin(), E = ranges.end(); I != E; ++I) { OS << *I; assert(I->valno == getValNumInfo(I->valno->id) && "Bad VNInfo"); } } // Print value number info. if (getNumValNums()) { OS << " "; unsigned vnum = 0; for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e; ++i, ++vnum) { const VNInfo *vni = *i; if (vnum) OS << " "; OS << vnum << "@"; if (vni->isUnused()) { OS << "x"; } else { OS << vni->def; if (vni->isPHIDef()) OS << "-phidef"; if (vni->hasPHIKill()) OS << "-phikill"; } } } } void LiveInterval::dump() const { dbgs() << *this << "\n"; } void LiveRange::print(raw_ostream &os) const { os << *this; } unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) { // Create initial equivalence classes. EqClass.clear(); EqClass.grow(LI->getNumValNums()); const VNInfo *used = 0, *unused = 0; // Determine connections. for (LiveInterval::const_vni_iterator I = LI->vni_begin(), E = LI->vni_end(); I != E; ++I) { const VNInfo *VNI = *I; // Group all unused values into one class. if (VNI->isUnused()) { if (unused) EqClass.join(unused->id, VNI->id); unused = VNI; continue; } used = VNI; if (VNI->isPHIDef()) { const MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def); assert(MBB && "Phi-def has no defining MBB"); // Connect to values live out of predecessors. for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(), PE = MBB->pred_end(); PI != PE; ++PI) if (const VNInfo *PVNI = LI->getVNInfoBefore(LIS.getMBBEndIdx(*PI))) EqClass.join(VNI->id, PVNI->id); } else { // Normal value defined by an instruction. Check for two-addr redef. // FIXME: This could be coincidental. Should we really check for a tied // operand constraint? // Note that VNI->def may be a use slot for an early clobber def. if (const VNInfo *UVNI = LI->getVNInfoBefore(VNI->def)) EqClass.join(VNI->id, UVNI->id); } } // Lump all the unused values in with the last used value. if (used && unused) EqClass.join(used->id, unused->id); EqClass.compress(); return EqClass.getNumClasses(); } void ConnectedVNInfoEqClasses::Distribute(LiveInterval *LIV[], MachineRegisterInfo &MRI) { assert(LIV[0] && "LIV[0] must be set"); LiveInterval &LI = *LIV[0]; // Rewrite instructions. for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg), RE = MRI.reg_end(); RI != RE;) { MachineOperand &MO = RI.getOperand(); MachineInstr *MI = MO.getParent(); ++RI; if (MO.isUse() && MO.isUndef()) continue; // DBG_VALUE instructions should have been eliminated earlier. SlotIndex Idx = LIS.getInstructionIndex(MI); Idx = Idx.getRegSlot(MO.isUse()); const VNInfo *VNI = LI.getVNInfoAt(Idx); assert(VNI && "Interval not live at use."); MO.setReg(LIV[getEqClass(VNI)]->reg); } // Move runs to new intervals. LiveInterval::iterator J = LI.begin(), E = LI.end(); while (J != E && EqClass[J->valno->id] == 0) ++J; for (LiveInterval::iterator I = J; I != E; ++I) { if (unsigned eq = EqClass[I->valno->id]) { assert((LIV[eq]->empty() || LIV[eq]->expiredAt(I->start)) && "New intervals should be empty"); LIV[eq]->ranges.push_back(*I); } else *J++ = *I; } LI.ranges.erase(J, E); // Transfer VNInfos to their new owners and renumber them. unsigned j = 0, e = LI.getNumValNums(); while (j != e && EqClass[j] == 0) ++j; for (unsigned i = j; i != e; ++i) { VNInfo *VNI = LI.getValNumInfo(i); if (unsigned eq = EqClass[i]) { VNI->id = LIV[eq]->getNumValNums(); LIV[eq]->valnos.push_back(VNI); } else { VNI->id = j; LI.valnos[j++] = VNI; } } LI.valnos.resize(j); }