//===-- 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 range 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 ranges can have holes,
// i.e. a range might look like [1,20), [50,65), [1000,1001). Each
// individual segment is represented as an instance of LiveRange::Segment,
// and the whole range is represented as an instance of LiveRange.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/LiveInterval.h"
#include "RegisterCoalescer.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include <algorithm>
using namespace llvm;
namespace {
//===----------------------------------------------------------------------===//
// Implementation of various methods necessary for calculation of live ranges.
// The implementation of the methods abstracts from the concrete type of the
// segment collection.
//
// Implementation of the class follows the Template design pattern. The base
// class contains generic algorithms that call collection-specific methods,
// which are provided in concrete subclasses. In order to avoid virtual calls
// these methods are provided by means of C++ template instantiation.
// The base class calls the methods of the subclass through method impl(),
// which casts 'this' pointer to the type of the subclass.
//
//===----------------------------------------------------------------------===//
template <typename ImplT, typename IteratorT, typename CollectionT>
class CalcLiveRangeUtilBase {
protected:
LiveRange *LR;
protected:
CalcLiveRangeUtilBase(LiveRange *LR) : LR(LR) {}
public:
typedef LiveRange::Segment Segment;
typedef IteratorT iterator;
VNInfo *createDeadDef(SlotIndex Def, VNInfo::Allocator &VNInfoAllocator) {
assert(!Def.isDead() && "Cannot define a value at the dead slot");
iterator I = impl().find(Def);
if (I == segments().end()) {
VNInfo *VNI = LR->getNextValue(Def, VNInfoAllocator);
impl().insertAtEnd(Segment(Def, Def.getDeadSlot(), VNI));
return VNI;
}
Segment *S = segmentAt(I);
if (SlotIndex::isSameInstr(Def, S->start)) {
assert(S->valno->def == S->start && "Inconsistent existing value def");
// It is possible to have both normal and early-clobber defs of the same
// register on an instruction. It doesn't make a lot of sense, but it is
// possible to specify in inline assembly.
//
// Just convert everything to early-clobber.
Def = std::min(Def, S->start);
if (Def != S->start)
S->start = S->valno->def = Def;
return S->valno;
}
assert(SlotIndex::isEarlierInstr(Def, S->start) && "Already live at def");
VNInfo *VNI = LR->getNextValue(Def, VNInfoAllocator);
segments().insert(I, Segment(Def, Def.getDeadSlot(), VNI));
return VNI;
}
VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Use) {
if (segments().empty())
return nullptr;
iterator I =
impl().findInsertPos(Segment(Use.getPrevSlot(), Use, nullptr));
if (I == segments().begin())
return nullptr;
--I;
if (I->end <= StartIdx)
return nullptr;
if (I->end < Use)
extendSegmentEndTo(I, Use);
return I->valno;
}
/// This method is used when we want to extend the segment specified
/// by I to end at the specified endpoint. To do this, we should
/// merge and eliminate all segments that this will overlap
/// with. The iterator is not invalidated.
void extendSegmentEndTo(iterator I, SlotIndex NewEnd) {
assert(I != segments().end() && "Not a valid segment!");
Segment *S = segmentAt(I);
VNInfo *ValNo = I->valno;
// Search for the first segment that we can't merge with.
iterator MergeTo = std::next(I);
for (; MergeTo != segments().end() && NewEnd >= MergeTo->end; ++MergeTo)
assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
// If NewEnd was in the middle of a segment, make sure to get its endpoint.
S->end = std::max(NewEnd, std::prev(MergeTo)->end);
// If the newly formed segment now touches the segment after it and if they
// have the same value number, merge the two segments into one segment.
if (MergeTo != segments().end() && MergeTo->start <= I->end &&
MergeTo->valno == ValNo) {
S->end = MergeTo->end;
++MergeTo;
}
// Erase any dead segments.
segments().erase(std::next(I), MergeTo);
}
/// This method is used when we want to extend the segment specified
/// by I to start at the specified endpoint. To do this, we should
/// merge and eliminate all segments that this will overlap with.
iterator extendSegmentStartTo(iterator I, SlotIndex NewStart) {
assert(I != segments().end() && "Not a valid segment!");
Segment *S = segmentAt(I);
VNInfo *ValNo = I->valno;
// Search for the first segment that we can't merge with.
iterator MergeTo = I;
do {
if (MergeTo == segments().begin()) {
S->start = NewStart;
segments().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 segment, just delete a range and
// extend that segment.
if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
segmentAt(MergeTo)->end = S->end;
} else {
// Otherwise, extend the segment right after.
++MergeTo;
Segment *MergeToSeg = segmentAt(MergeTo);
MergeToSeg->start = NewStart;
MergeToSeg->end = S->end;
}
segments().erase(std::next(MergeTo), std::next(I));
return MergeTo;
}
iterator addSegment(Segment S) {
SlotIndex Start = S.start, End = S.end;
iterator I = impl().findInsertPos(S);
// If the inserted segment starts in the middle or right at the end of
// another segment, just extend that segment to contain the segment of S.
if (I != segments().begin()) {
iterator B = std::prev(I);
if (S.valno == B->valno) {
if (B->start <= Start && B->end >= Start) {
extendSegmentEndTo(B, End);
return B;
}
} else {
// Check to make sure that we are not overlapping two live segments with
// different valno's.
assert(B->end <= Start &&
"Cannot overlap two segments with differing ValID's"
" (did you def the same reg twice in a MachineInstr?)");
}
}
// Otherwise, if this segment ends in the middle of, or right next
// to, another segment, merge it into that segment.
if (I != segments().end()) {
if (S.valno == I->valno) {
if (I->start <= End) {
I = extendSegmentStartTo(I, Start);
// If S is a complete superset of a segment, we may need to grow its
// endpoint as well.
if (End > I->end)
extendSegmentEndTo(I, End);
return I;
}
} else {
// Check to make sure that we are not overlapping two live segments with
// different valno's.
assert(I->start >= End &&
"Cannot overlap two segments with differing ValID's");
}
}
// Otherwise, this is just a new segment that doesn't interact with
// anything.
// Insert it.
return segments().insert(I, S);
}
private:
ImplT &impl() { return *static_cast<ImplT *>(this); }
CollectionT &segments() { return impl().segmentsColl(); }
Segment *segmentAt(iterator I) { return const_cast<Segment *>(&(*I)); }
};
//===----------------------------------------------------------------------===//
// Instantiation of the methods for calculation of live ranges
// based on a segment vector.
//===----------------------------------------------------------------------===//
class CalcLiveRangeUtilVector;
typedef CalcLiveRangeUtilBase<CalcLiveRangeUtilVector, LiveRange::iterator,
LiveRange::Segments> CalcLiveRangeUtilVectorBase;
class CalcLiveRangeUtilVector : public CalcLiveRangeUtilVectorBase {
public:
CalcLiveRangeUtilVector(LiveRange *LR) : CalcLiveRangeUtilVectorBase(LR) {}
private:
friend CalcLiveRangeUtilVectorBase;
LiveRange::Segments &segmentsColl() { return LR->segments; }
void insertAtEnd(const Segment &S) { LR->segments.push_back(S); }
iterator find(SlotIndex Pos) { return LR->find(Pos); }
iterator findInsertPos(Segment S) {
return std::upper_bound(LR->begin(), LR->end(), S.start);
}
};
//===----------------------------------------------------------------------===//
// Instantiation of the methods for calculation of live ranges
// based on a segment set.
//===----------------------------------------------------------------------===//
class CalcLiveRangeUtilSet;
typedef CalcLiveRangeUtilBase<CalcLiveRangeUtilSet,
LiveRange::SegmentSet::iterator,
LiveRange::SegmentSet> CalcLiveRangeUtilSetBase;
class CalcLiveRangeUtilSet : public CalcLiveRangeUtilSetBase {
public:
CalcLiveRangeUtilSet(LiveRange *LR) : CalcLiveRangeUtilSetBase(LR) {}
private:
friend CalcLiveRangeUtilSetBase;
LiveRange::SegmentSet &segmentsColl() { return *LR->segmentSet; }
void insertAtEnd(const Segment &S) {
LR->segmentSet->insert(LR->segmentSet->end(), S);
}
iterator find(SlotIndex Pos) {
iterator I =
LR->segmentSet->upper_bound(Segment(Pos, Pos.getNextSlot(), nullptr));
if (I == LR->segmentSet->begin())
return I;
iterator PrevI = std::prev(I);
if (Pos < (*PrevI).end)
return PrevI;
return I;
}
iterator findInsertPos(Segment S) {
iterator I = LR->segmentSet->upper_bound(S);
if (I != LR->segmentSet->end() && !(S.start < *I))
++I;
return I;
}
};
} // namespace
//===----------------------------------------------------------------------===//
// LiveRange methods
//===----------------------------------------------------------------------===//
LiveRange::iterator LiveRange::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 = 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;
}
VNInfo *LiveRange::createDeadDef(SlotIndex Def,
VNInfo::Allocator &VNInfoAllocator) {
// Use the segment set, if it is available.
if (segmentSet != nullptr)
return CalcLiveRangeUtilSet(this).createDeadDef(Def, VNInfoAllocator);
// Otherwise use the segment vector.
return CalcLiveRangeUtilVector(this).createDeadDef(Def, VNInfoAllocator);
}
// overlaps - Return true if the intersection of the two live ranges is
// not empty.
//
// An example for overlaps():
//
// 0: A = ...
// 4: B = ...
// 8: C = A + B ;; last use of A
//
// The live ranges 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 LiveRange::overlapsFrom(const LiveRange& other,
const_iterator StartPos) const {
assert(!empty() && "empty range");
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 != 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.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;
}
bool LiveRange::overlaps(const LiveRange &Other, const CoalescerPair &CP,
const SlotIndexes &Indexes) const {
assert(!empty() && "empty range");
if (Other.empty())
return false;
// Use binary searches to find initial positions.
const_iterator I = find(Other.beginIndex());
const_iterator IE = end();
if (I == IE)
return false;
const_iterator J = Other.find(I->start);
const_iterator JE = Other.end();
if (J == JE)
return false;
for (;;) {
// J has just been advanced to satisfy:
assert(J->end >= I->start);
// Check for an overlap.
if (J->start < I->end) {
// I and J are overlapping. Find the later start.
SlotIndex Def = std::max(I->start, J->start);
// Allow the overlap if Def is a coalescable copy.
if (Def.isBlock() ||
!CP.isCoalescable(Indexes.getInstructionFromIndex(Def)))
return true;
}
// Advance the iterator that ends first to check for more overlaps.
if (J->end > I->end) {
std::swap(I, J);
std::swap(IE, JE);
}
// Advance J until J->end >= I->start.
do
if (++J == JE)
return false;
while (J->end < I->start);
}
}
/// overlaps - Return true if the live range overlaps an interval specified
/// by [Start, End).
bool LiveRange::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;
}
bool LiveRange::covers(const LiveRange &Other) const {
if (empty())
return Other.empty();
const_iterator I = begin();
for (const Segment &O : Other.segments) {
I = advanceTo(I, O.start);
if (I == end() || I->start > O.start)
return false;
// Check adjacent live segments and see if we can get behind O.end.
while (I->end < O.end) {
const_iterator Last = I;
// Get next segment and abort if it was not adjacent.
++I;
if (I == end() || Last->end != I->start)
return false;
}
}
return true;
}
/// 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 LiveRange::markValNoForDeletion(VNInfo *ValNo) {
if (ValNo->id == getNumValNums()-1) {
do {
valnos.pop_back();
} while (!valnos.empty() && valnos.back()->isUnused());
} else {
ValNo->markUnused();
}
}
/// RenumberValues - Renumber all values in order of appearance and delete the
/// remaining unused values.
void LiveRange::RenumberValues() {
SmallPtrSet<VNInfo*, 8> Seen;
valnos.clear();
for (const Segment &S : segments) {
VNInfo *VNI = S.valno;
if (!Seen.insert(VNI).second)
continue;
assert(!VNI->isUnused() && "Unused valno used by live segment");
VNI->id = (unsigned)valnos.size();
valnos.push_back(VNI);
}
}
void LiveRange::addSegmentToSet(Segment S) {
CalcLiveRangeUtilSet(this).addSegment(S);
}
LiveRange::iterator LiveRange::addSegment(Segment S) {
// Use the segment set, if it is available.
if (segmentSet != nullptr) {
addSegmentToSet(S);
return end();
}
// Otherwise use the segment vector.
return CalcLiveRangeUtilVector(this).addSegment(S);
}
void LiveRange::append(const Segment S) {
// Check that the segment belongs to the back of the list.
assert(segments.empty() || segments.back().end <= S.start);
segments.push_back(S);
}
/// extendInBlock - If this range 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 *LiveRange::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) {
// Use the segment set, if it is available.
if (segmentSet != nullptr)
return CalcLiveRangeUtilSet(this).extendInBlock(StartIdx, Kill);
// Otherwise use the segment vector.
return CalcLiveRangeUtilVector(this).extendInBlock(StartIdx, Kill);
}
/// Remove the specified segment from this range. Note that the segment must
/// be in a single Segment in its entirety.
void LiveRange::removeSegment(SlotIndex Start, SlotIndex End,
bool RemoveDeadValNo) {
// Find the Segment containing this span.
iterator I = find(Start);
assert(I != end() && "Segment is not in range!");
assert(I->containsInterval(Start, End)
&& "Segment is not entirely in range!");
// If the span we are removing is at the start of the Segment, 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);
}
}
segments.erase(I); // Removed the whole Segment.
} else
I->start = End;
return;
}
// Otherwise if the span we are removing is at the end of the Segment,
// adjust the other way.
if (I->end == End) {
I->end = Start;
return;
}
// Otherwise, we are splitting the Segment into two pieces.
SlotIndex OldEnd = I->end;
I->end = Start; // Trim the old segment.
// Insert the new one.
segments.insert(std::next(I), Segment(End, OldEnd, ValNo));
}
/// removeValNo - Remove all the segments defined by the specified value#.
/// Also remove the value# from value# list.
void LiveRange::removeValNo(VNInfo *ValNo) {
if (empty()) return;
segments.erase(std::remove_if(begin(), end(), [ValNo](const Segment &S) {
return S.valno == ValNo;
}), end());
// Now that ValNo is dead, remove it.
markValNoForDeletion(ValNo);
}
void LiveRange::join(LiveRange &Other,
const int *LHSValNoAssignments,
const int *RHSValNoAssignments,
SmallVectorImpl<VNInfo *> &NewVNInfo) {
verify();
// Determine if any of our values are mapped. This is uncommon, so we want
// to avoid the range 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 range assignment, rewrite it now.
if (MustMapCurValNos && !empty()) {
// Map the first live range.
iterator OutIt = begin();
OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
for (iterator I = std::next(OutIt), E = end(); I != E; ++I) {
VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
assert(nextValNo && "Huh?");
// If this live range has the same value # as its immediate predecessor,
// and if they are neighbors, remove one Segment. 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 segment,
++OutIt;
OutIt->valno = nextValNo;
if (OutIt != I) {
OutIt->start = I->start;
OutIt->end = I->end;
}
}
}
// If we merge some segments, chop off the end.
++OutIt;
segments.erase(OutIt, end());
}
// Rewrite Other values before changing the VNInfo ids.
// This can leave Other in an invalid state because we're not coalescing
// touching segments that now have identical values. That's OK since Other is
// not supposed to be valid after calling join();
for (Segment &S : Other.segments)
S.valno = NewVNInfo[RHSValNoAssignments[S.valno->id]];
// Update val# info. Renumber them and make sure they all belong to this
// LiveRange 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 segments into the LHS.
LiveRangeUpdater Updater(this);
for (Segment &S : Other.segments)
Updater.add(S);
}
/// Merge all of the segments in RHS into this live range as the specified
/// value number. The segments in RHS are allowed to overlap with segments in
/// the current range, but only if the overlapping segments have the
/// specified value number.
void LiveRange::MergeSegmentsInAsValue(const LiveRange &RHS,
VNInfo *LHSValNo) {
LiveRangeUpdater Updater(this);
for (const Segment &S : RHS.segments)
Updater.add(S.start, S.end, LHSValNo);
}
/// MergeValueInAsValue - Merge all of the live segments of a specific val#
/// in RHS into this live range as the specified value number.
/// The segments in RHS are allowed to overlap with segments in the
/// current range, it will replace the value numbers of the overlaped
/// segments with the specified value number.
void LiveRange::MergeValueInAsValue(const LiveRange &RHS,
const VNInfo *RHSValNo,
VNInfo *LHSValNo) {
LiveRangeUpdater Updater(this);
for (const Segment &S : RHS.segments)
if (S.valno == RHSValNo)
Updater.add(S.start, S.end, LHSValNo);
}
/// MergeValueNumberInto - This method is called when two value nubmers
/// are found to be equivalent. This eliminates V1, replacing all
/// segments 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 *LiveRange::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 segments into V2.
for (iterator I = begin(); I != end(); ) {
iterator S = I++;
if (S->valno != V1) continue; // Not a V1 Segment.
// Okay, we found a V1 live range. If it had a previous, touching, V2 live
// range, extend it.
if (S != begin()) {
iterator Prev = S-1;
if (Prev->valno == V2 && Prev->end == S->start) {
Prev->end = S->end;
// Erase this live-range.
segments.erase(S);
I = Prev+1;
S = Prev;
}
}
// Okay, now we have a V1 or V2 live range that is maximally merged forward.
// Ensure that it is a V2 live-range.
S->valno = V2;
// If we can merge it into later V2 segments, do so now. We ignore any
// following V1 segments, as they will be merged in subsequent iterations
// of the loop.
if (I != end()) {
if (I->start == S->end && I->valno == V2) {
S->end = I->end;
segments.erase(I);
I = S+1;
}
}
}
// Now that V1 is dead, remove it.
markValNoForDeletion(V1);
return V2;
}
void LiveRange::flushSegmentSet() {
assert(segmentSet != nullptr && "segment set must have been created");
assert(
segments.empty() &&
"segment set can be used only initially before switching to the array");
segments.append(segmentSet->begin(), segmentSet->end());
segmentSet = nullptr;
verify();
}
void LiveInterval::freeSubRange(SubRange *S) {
S->~SubRange();
// Memory was allocated with BumpPtr allocator and is not freed here.
}
void LiveInterval::removeEmptySubRanges() {
SubRange **NextPtr = &SubRanges;
SubRange *I = *NextPtr;
while (I != nullptr) {
if (!I->empty()) {
NextPtr = &I->Next;
I = *NextPtr;
continue;
}
// Skip empty subranges until we find the first nonempty one.
do {
SubRange *Next = I->Next;
freeSubRange(I);
I = Next;
} while (I != nullptr && I->empty());
*NextPtr = I;
}
}
void LiveInterval::clearSubRanges() {
for (SubRange *I = SubRanges, *Next; I != nullptr; I = Next) {
Next = I->Next;
freeSubRange(I);
}
SubRanges = nullptr;
}
/// Helper function for constructMainRangeFromSubranges(): Search the CFG
/// backwards until we find a place covered by a LiveRange segment that actually
/// has a valno set.
static VNInfo *searchForVNI(const SlotIndexes &Indexes, LiveRange &LR,
const MachineBasicBlock *MBB,
SmallPtrSetImpl<const MachineBasicBlock*> &Visited) {
// We start the search at the end of MBB.
SlotIndex EndIdx = Indexes.getMBBEndIdx(MBB);
// In our use case we can't live the area covered by the live segments without
// finding an actual VNI def.
LiveRange::iterator I = LR.find(EndIdx.getPrevSlot());
assert(I != LR.end());
LiveRange::Segment &S = *I;
if (S.valno != nullptr)
return S.valno;
VNInfo *VNI = nullptr;
// Continue at predecessors (we could even go to idom with domtree available).
for (const MachineBasicBlock *Pred : MBB->predecessors()) {
// Avoid going in circles.
if (!Visited.insert(Pred).second)
continue;
VNI = searchForVNI(Indexes, LR, Pred, Visited);
if (VNI != nullptr) {
S.valno = VNI;
break;
}
}
return VNI;
}
static void determineMissingVNIs(const SlotIndexes &Indexes, LiveInterval &LI) {
SmallPtrSet<const MachineBasicBlock*, 5> Visited;
LiveRange::iterator OutIt;
VNInfo *PrevValNo = nullptr;
for (LiveRange::iterator I = LI.begin(), E = LI.end(); I != E; ++I) {
LiveRange::Segment &S = *I;
// Determine final VNI if necessary.
if (S.valno == nullptr) {
// This can only happen at the begin of a basic block.
assert(S.start.isBlock() && "valno should only be missing at block begin");
Visited.clear();
const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(S.start);
for (const MachineBasicBlock *Pred : MBB->predecessors()) {
VNInfo *VNI = searchForVNI(Indexes, LI, Pred, Visited);
if (VNI != nullptr) {
S.valno = VNI;
break;
}
}
assert(S.valno != nullptr && "could not determine valno");
}
// Merge with previous segment if it has the same VNI.
if (PrevValNo == S.valno && OutIt->end == S.start) {
OutIt->end = S.end;
} else {
// Didn't merge. Move OutIt to next segment.
if (PrevValNo == nullptr)
OutIt = LI.begin();
else
++OutIt;
if (OutIt != I)
*OutIt = *I;
PrevValNo = S.valno;
}
}
// If we merged some segments chop off the end.
++OutIt;
LI.segments.erase(OutIt, LI.end());
}
void LiveInterval::constructMainRangeFromSubranges(
const SlotIndexes &Indexes, VNInfo::Allocator &VNIAllocator) {
// The basic observations on which this algorithm is based:
// - Each Def/ValNo in a subrange must have a corresponding def on the main
// range, but not further defs/valnos are necessary.
// - If any of the subranges is live at a point the main liverange has to be
// live too, conversily if no subrange is live the main range mustn't be
// live either.
// We do this by scanning through all the subranges simultaneously creating new
// segments in the main range as segments start/ends come up in the subranges.
assert(hasSubRanges() && "expected subranges to be present");
assert(segments.empty() && valnos.empty() && "expected empty main range");
// Collect subrange, iterator pairs for the walk and determine first and last
// SlotIndex involved.
SmallVector<std::pair<const SubRange*, const_iterator>, 4> SRs;
SlotIndex First;
SlotIndex Last;
for (const SubRange &SR : subranges()) {
if (SR.empty())
continue;
SRs.push_back(std::make_pair(&SR, SR.begin()));
if (!First.isValid() || SR.segments.front().start < First)
First = SR.segments.front().start;
if (!Last.isValid() || SR.segments.back().end > Last)
Last = SR.segments.back().end;
}
// Walk over all subranges simultaneously.
Segment CurrentSegment;
bool ConstructingSegment = false;
bool NeedVNIFixup = false;
LaneBitmask ActiveMask = 0;
SlotIndex Pos = First;
while (true) {
SlotIndex NextPos = Last;
enum {
NOTHING,
BEGIN_SEGMENT,
END_SEGMENT,
} Event = NOTHING;
// Which subregister lanes are affected by the current event.
LaneBitmask EventMask = 0;
// Whether a BEGIN_SEGMENT is also a valno definition point.
bool IsDef = false;
// Find the next begin or end of a subrange segment. Combine masks if we
// have multiple begins/ends at the same position. Ends take precedence over
// Begins.
for (auto &SRP : SRs) {
const SubRange &SR = *SRP.first;
const_iterator &I = SRP.second;
// Advance iterator of subrange to a segment involving Pos; the earlier
// segments are already merged at this point.
while (I != SR.end() &&
(I->end < Pos ||
(I->end == Pos && (ActiveMask & SR.LaneMask) == 0)))
++I;
if (I == SR.end())
continue;
if ((ActiveMask & SR.LaneMask) == 0 &&
Pos <= I->start && I->start <= NextPos) {
// Merge multiple begins at the same position.
if (I->start == NextPos && Event == BEGIN_SEGMENT) {
EventMask |= SR.LaneMask;
IsDef |= I->valno->def == I->start;
} else if (I->start < NextPos || Event != END_SEGMENT) {
Event = BEGIN_SEGMENT;
NextPos = I->start;
EventMask = SR.LaneMask;
IsDef = I->valno->def == I->start;
}
}
if ((ActiveMask & SR.LaneMask) != 0 &&
Pos <= I->end && I->end <= NextPos) {
// Merge multiple ends at the same position.
if (I->end == NextPos && Event == END_SEGMENT)
EventMask |= SR.LaneMask;
else {
Event = END_SEGMENT;
NextPos = I->end;
EventMask = SR.LaneMask;
}
}
}
// Advance scan position.
Pos = NextPos;
if (Event == BEGIN_SEGMENT) {
if (ConstructingSegment && IsDef) {
// Finish previous segment because we have to start a new one.
CurrentSegment.end = Pos;
append(CurrentSegment);
ConstructingSegment = false;
}
// Start a new segment if necessary.
if (!ConstructingSegment) {
// Determine value number for the segment.
VNInfo *VNI;
if (IsDef) {
VNI = getNextValue(Pos, VNIAllocator);
} else {
// We have to reuse an existing value number, if we are lucky
// then we already passed one of the predecessor blocks and determined
// its value number (with blocks in reverse postorder this would be
// always true but we have no such guarantee).
assert(Pos.isBlock());
const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(Pos);
// See if any of the predecessor blocks has a lower number and a VNI
for (const MachineBasicBlock *Pred : MBB->predecessors()) {
SlotIndex PredEnd = Indexes.getMBBEndIdx(Pred);
VNI = getVNInfoBefore(PredEnd);
if (VNI != nullptr)
break;
}
// Def will come later: We have to do an extra fixup pass.
if (VNI == nullptr)
NeedVNIFixup = true;
}
// In rare cases we can produce adjacent segments with the same value
// number (if they come from different subranges, but happen to have
// the same defining instruction). VNIFixup will fix those cases.
if (!empty() && segments.back().end == Pos &&
segments.back().valno == VNI)
NeedVNIFixup = true;
CurrentSegment.start = Pos;
CurrentSegment.valno = VNI;
ConstructingSegment = true;
}
ActiveMask |= EventMask;
} else if (Event == END_SEGMENT) {
assert(ConstructingSegment);
// Finish segment if no lane is active anymore.
ActiveMask &= ~EventMask;
if (ActiveMask == 0) {
CurrentSegment.end = Pos;
append(CurrentSegment);
ConstructingSegment = false;
}
} else {
// We reached the end of the last subranges and can stop.
assert(Event == NOTHING);
break;
}
}
// We might not be able to assign new valnos for all segments if the basic
// block containing the definition comes after a segment using the valno.
// Do a fixup pass for this uncommon case.
if (NeedVNIFixup)
determineMissingVNIs(Indexes, *this);
assert(ActiveMask == 0 && !ConstructingSegment && "all segments ended");
verify();
}
unsigned LiveInterval::getSize() const {
unsigned Sum = 0;
for (const Segment &S : segments)
Sum += S.start.distance(S.end);
return Sum;
}
raw_ostream& llvm::operator<<(raw_ostream& os, const LiveRange::Segment &S) {
return os << '[' << S.start << ',' << S.end << ':' << S.valno->id << ")";
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void LiveRange::Segment::dump() const {
dbgs() << *this << "\n";
}
#endif
void LiveRange::print(raw_ostream &OS) const {
if (empty())
OS << "EMPTY";
else {
for (const Segment &S : segments) {
OS << S;
assert(S.valno == getValNumInfo(S.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 << "-phi";
}
}
}
}
void LiveInterval::print(raw_ostream &OS) const {
OS << PrintReg(reg) << ' ';
super::print(OS);
// Print subranges
for (const SubRange &SR : subranges()) {
OS << " L" << PrintLaneMask(SR.LaneMask) << ' ' << SR;
}
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void LiveRange::dump() const {
dbgs() << *this << "\n";
}
void LiveInterval::dump() const {
dbgs() << *this << "\n";
}
#endif
#ifndef NDEBUG
void LiveRange::verify() const {
for (const_iterator I = begin(), E = end(); I != E; ++I) {
assert(I->start.isValid());
assert(I->end.isValid());
assert(I->start < I->end);
assert(I->valno != nullptr);
assert(I->valno->id < valnos.size());
assert(I->valno == valnos[I->valno->id]);
if (std::next(I) != E) {
assert(I->end <= std::next(I)->start);
if (I->end == std::next(I)->start)
assert(I->valno != std::next(I)->valno);
}
}
}
void LiveInterval::verify(const MachineRegisterInfo *MRI) const {
super::verify();
// Make sure SubRanges are fine and LaneMasks are disjunct.
LaneBitmask Mask = 0;
LaneBitmask MaxMask = MRI != nullptr ? MRI->getMaxLaneMaskForVReg(reg) : ~0u;
for (const SubRange &SR : subranges()) {
// Subrange lanemask should be disjunct to any previous subrange masks.
assert((Mask & SR.LaneMask) == 0);
Mask |= SR.LaneMask;
// subrange mask should not contained in maximum lane mask for the vreg.
assert((Mask & ~MaxMask) == 0);
// empty subranges must be removed.
assert(!SR.empty());
SR.verify();
// Main liverange should cover subrange.
assert(covers(SR));
}
}
#endif
//===----------------------------------------------------------------------===//
// LiveRangeUpdater class
//===----------------------------------------------------------------------===//
//
// The LiveRangeUpdater class always maintains these invariants:
//
// - When LastStart is invalid, Spills is empty and the iterators are invalid.
// This is the initial state, and the state created by flush().
// In this state, isDirty() returns false.
//
// Otherwise, segments are kept in three separate areas:
//
// 1. [begin; WriteI) at the front of LR.
// 2. [ReadI; end) at the back of LR.
// 3. Spills.
//
// - LR.begin() <= WriteI <= ReadI <= LR.end().
// - Segments in all three areas are fully ordered and coalesced.
// - Segments in area 1 precede and can't coalesce with segments in area 2.
// - Segments in Spills precede and can't coalesce with segments in area 2.
// - No coalescing is possible between segments in Spills and segments in area
// 1, and there are no overlapping segments.
//
// The segments in Spills are not ordered with respect to the segments in area
// 1. They need to be merged.
//
// When they exist, Spills.back().start <= LastStart,
// and WriteI[-1].start <= LastStart.
void LiveRangeUpdater::print(raw_ostream &OS) const {
if (!isDirty()) {
if (LR)
OS << "Clean updater: " << *LR << '\n';
else
OS << "Null updater.\n";
return;
}
assert(LR && "Can't have null LR in dirty updater.");
OS << " updater with gap = " << (ReadI - WriteI)
<< ", last start = " << LastStart
<< ":\n Area 1:";
for (const auto &S : make_range(LR->begin(), WriteI))
OS << ' ' << S;
OS << "\n Spills:";
for (unsigned I = 0, E = Spills.size(); I != E; ++I)
OS << ' ' << Spills[I];
OS << "\n Area 2:";
for (const auto &S : make_range(ReadI, LR->end()))
OS << ' ' << S;
OS << '\n';
}
void LiveRangeUpdater::dump() const
{
print(errs());
}
// Determine if A and B should be coalesced.
static inline bool coalescable(const LiveRange::Segment &A,
const LiveRange::Segment &B) {
assert(A.start <= B.start && "Unordered live segments.");
if (A.end == B.start)
return A.valno == B.valno;
if (A.end < B.start)
return false;
assert(A.valno == B.valno && "Cannot overlap different values");
return true;
}
void LiveRangeUpdater::add(LiveRange::Segment Seg) {
assert(LR && "Cannot add to a null destination");
// Fall back to the regular add method if the live range
// is using the segment set instead of the segment vector.
if (LR->segmentSet != nullptr) {
LR->addSegmentToSet(Seg);
return;
}
// Flush the state if Start moves backwards.
if (!LastStart.isValid() || LastStart > Seg.start) {
if (isDirty())
flush();
// This brings us to an uninitialized state. Reinitialize.
assert(Spills.empty() && "Leftover spilled segments");
WriteI = ReadI = LR->begin();
}
// Remember start for next time.
LastStart = Seg.start;
// Advance ReadI until it ends after Seg.start.
LiveRange::iterator E = LR->end();
if (ReadI != E && ReadI->end <= Seg.start) {
// First try to close the gap between WriteI and ReadI with spills.
if (ReadI != WriteI)
mergeSpills();
// Then advance ReadI.
if (ReadI == WriteI)
ReadI = WriteI = LR->find(Seg.start);
else
while (ReadI != E && ReadI->end <= Seg.start)
*WriteI++ = *ReadI++;
}
assert(ReadI == E || ReadI->end > Seg.start);
// Check if the ReadI segment begins early.
if (ReadI != E && ReadI->start <= Seg.start) {
assert(ReadI->valno == Seg.valno && "Cannot overlap different values");
// Bail if Seg is completely contained in ReadI.
if (ReadI->end >= Seg.end)
return;
// Coalesce into Seg.
Seg.start = ReadI->start;
++ReadI;
}
// Coalesce as much as possible from ReadI into Seg.
while (ReadI != E && coalescable(Seg, *ReadI)) {
Seg.end = std::max(Seg.end, ReadI->end);
++ReadI;
}
// Try coalescing Spills.back() into Seg.
if (!Spills.empty() && coalescable(Spills.back(), Seg)) {
Seg.start = Spills.back().start;
Seg.end = std::max(Spills.back().end, Seg.end);
Spills.pop_back();
}
// Try coalescing Seg into WriteI[-1].
if (WriteI != LR->begin() && coalescable(WriteI[-1], Seg)) {
WriteI[-1].end = std::max(WriteI[-1].end, Seg.end);
return;
}
// Seg doesn't coalesce with anything, and needs to be inserted somewhere.
if (WriteI != ReadI) {
*WriteI++ = Seg;
return;
}
// Finally, append to LR or Spills.
if (WriteI == E) {
LR->segments.push_back(Seg);
WriteI = ReadI = LR->end();
} else
Spills.push_back(Seg);
}
// Merge as many spilled segments as possible into the gap between WriteI
// and ReadI. Advance WriteI to reflect the inserted instructions.
void LiveRangeUpdater::mergeSpills() {
// Perform a backwards merge of Spills and [SpillI;WriteI).
size_t GapSize = ReadI - WriteI;
size_t NumMoved = std::min(Spills.size(), GapSize);
LiveRange::iterator Src = WriteI;
LiveRange::iterator Dst = Src + NumMoved;
LiveRange::iterator SpillSrc = Spills.end();
LiveRange::iterator B = LR->begin();
// This is the new WriteI position after merging spills.
WriteI = Dst;
// Now merge Src and Spills backwards.
while (Src != Dst) {
if (Src != B && Src[-1].start > SpillSrc[-1].start)
*--Dst = *--Src;
else
*--Dst = *--SpillSrc;
}
assert(NumMoved == size_t(Spills.end() - SpillSrc));
Spills.erase(SpillSrc, Spills.end());
}
void LiveRangeUpdater::flush() {
if (!isDirty())
return;
// Clear the dirty state.
LastStart = SlotIndex();
assert(LR && "Cannot add to a null destination");
// Nothing to merge?
if (Spills.empty()) {
LR->segments.erase(WriteI, ReadI);
LR->verify();
return;
}
// Resize the WriteI - ReadI gap to match Spills.
size_t GapSize = ReadI - WriteI;
if (GapSize < Spills.size()) {
// The gap is too small. Make some room.
size_t WritePos = WriteI - LR->begin();
LR->segments.insert(ReadI, Spills.size() - GapSize, LiveRange::Segment());
// This also invalidated ReadI, but it is recomputed below.
WriteI = LR->begin() + WritePos;
} else {
// Shrink the gap if necessary.
LR->segments.erase(WriteI + Spills.size(), ReadI);
}
ReadI = WriteI + Spills.size();
mergeSpills();
LR->verify();
}
unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) {
// Create initial equivalence classes.
EqClass.clear();
EqClass.grow(LI->getNumValNums());
const VNInfo *used = nullptr, *unused = nullptr;
// Determine connections.
for (const VNInfo *VNI : LI->valnos) {
// 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();
}
template<typename LiveRangeT, typename EqClassesT>
static void DistributeRange(LiveRangeT &LR, LiveRangeT *SplitLRs[],
EqClassesT VNIClasses) {
// Move segments to new intervals.
LiveRange::iterator J = LR.begin(), E = LR.end();
while (J != E && VNIClasses[J->valno->id] == 0)
++J;
for (LiveRange::iterator I = J; I != E; ++I) {
if (unsigned eq = VNIClasses[I->valno->id]) {
assert((SplitLRs[eq-1]->empty() || SplitLRs[eq-1]->expiredAt(I->start)) &&
"New intervals should be empty");
SplitLRs[eq-1]->segments.push_back(*I);
} else
*J++ = *I;
}
LR.segments.erase(J, E);
// Transfer VNInfos to their new owners and renumber them.
unsigned j = 0, e = LR.getNumValNums();
while (j != e && VNIClasses[j] == 0)
++j;
for (unsigned i = j; i != e; ++i) {
VNInfo *VNI = LR.getValNumInfo(i);
if (unsigned eq = VNIClasses[i]) {
VNI->id = SplitLRs[eq-1]->getNumValNums();
SplitLRs[eq-1]->valnos.push_back(VNI);
} else {
VNI->id = j;
LR.valnos[j++] = VNI;
}
}
LR.valnos.resize(j);
}
void ConnectedVNInfoEqClasses::Distribute(LiveInterval &LI, LiveInterval *LIV[],
MachineRegisterInfo &MRI) {
// Rewrite instructions.
for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg),
RE = MRI.reg_end(); RI != RE;) {
MachineOperand &MO = *RI;
MachineInstr *MI = RI->getParent();
++RI;
// DBG_VALUE instructions don't have slot indexes, so get the index of the
// instruction before them.
// Normally, DBG_VALUE instructions are removed before this function is
// called, but it is not a requirement.
SlotIndex Idx;
if (MI->isDebugValue())
Idx = LIS.getSlotIndexes()->getIndexBefore(MI);
else
Idx = LIS.getInstructionIndex(MI);
LiveQueryResult LRQ = LI.Query(Idx);
const VNInfo *VNI = MO.readsReg() ? LRQ.valueIn() : LRQ.valueDefined();
// In the case of an <undef> use that isn't tied to any def, VNI will be
// NULL. If the use is tied to a def, VNI will be the defined value.
if (!VNI)
continue;
if (unsigned EqClass = getEqClass(VNI))
MO.setReg(LIV[EqClass-1]->reg);
}
// Distribute subregister liveranges.
if (LI.hasSubRanges()) {
unsigned NumComponents = EqClass.getNumClasses();
SmallVector<unsigned, 8> VNIMapping;
SmallVector<LiveInterval::SubRange*, 8> SubRanges;
BumpPtrAllocator &Allocator = LIS.getVNInfoAllocator();
for (LiveInterval::SubRange &SR : LI.subranges()) {
// Create new subranges in the split intervals and construct a mapping
// for the VNInfos in the subrange.
unsigned NumValNos = SR.valnos.size();
VNIMapping.clear();
VNIMapping.reserve(NumValNos);
SubRanges.clear();
SubRanges.resize(NumComponents-1, nullptr);
for (unsigned I = 0; I < NumValNos; ++I) {
const VNInfo &VNI = *SR.valnos[I];
const VNInfo *MainRangeVNI = LI.getVNInfoAt(VNI.def);
assert(MainRangeVNI != nullptr
&& "SubRange def must have corresponding main range def");
unsigned ComponentNum = getEqClass(MainRangeVNI);
VNIMapping.push_back(ComponentNum);
if (ComponentNum > 0 && SubRanges[ComponentNum-1] == nullptr) {
SubRanges[ComponentNum-1]
= LIV[ComponentNum-1]->createSubRange(Allocator, SR.LaneMask);
}
}
DistributeRange(SR, SubRanges.data(), VNIMapping);
}
LI.removeEmptySubRanges();
}
// Distribute main liverange.
DistributeRange(LI, LIV, EqClass);
}