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llvm-project/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp

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//===-- LiveIntervalAnalysis.cpp - Live Interval Analysis -----------------===//
//
// 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 LiveInterval analysis pass which is used
// by the Linear Scan Register allocator. This pass linearizes the
// basic blocks of the function in DFS order and uses the
// LiveVariables pass to conservatively compute live intervals for
// each virtual and physical register.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "LiveRangeCalc.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/VirtRegMap.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/BlockFrequency.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include <algorithm>
#include <cmath>
#include <limits>
using namespace llvm;
#define DEBUG_TYPE "regalloc"
char LiveIntervals::ID = 0;
char &llvm::LiveIntervalsID = LiveIntervals::ID;
INITIALIZE_PASS_BEGIN(LiveIntervals, "liveintervals",
"Live Interval Analysis", false, false)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_DEPENDENCY(LiveVariables)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
INITIALIZE_PASS_END(LiveIntervals, "liveintervals",
"Live Interval Analysis", false, false)
#ifndef NDEBUG
static cl::opt<bool> EnablePrecomputePhysRegs(
"precompute-phys-liveness", cl::Hidden,
cl::desc("Eagerly compute live intervals for all physreg units."));
#else
static bool EnablePrecomputePhysRegs = false;
#endif // NDEBUG
void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addRequired<AliasAnalysis>();
AU.addPreserved<AliasAnalysis>();
// LiveVariables isn't really required by this analysis, it is only required
// here to make sure it is live during TwoAddressInstructionPass and
// PHIElimination. This is temporary.
AU.addRequired<LiveVariables>();
AU.addPreserved<LiveVariables>();
AU.addPreservedID(MachineLoopInfoID);
AU.addRequiredTransitiveID(MachineDominatorsID);
AU.addPreservedID(MachineDominatorsID);
AU.addPreserved<SlotIndexes>();
AU.addRequiredTransitive<SlotIndexes>();
MachineFunctionPass::getAnalysisUsage(AU);
}
LiveIntervals::LiveIntervals() : MachineFunctionPass(ID),
DomTree(nullptr), LRCalc(nullptr) {
initializeLiveIntervalsPass(*PassRegistry::getPassRegistry());
}
LiveIntervals::~LiveIntervals() {
delete LRCalc;
}
void LiveIntervals::releaseMemory() {
// Free the live intervals themselves.
for (unsigned i = 0, e = VirtRegIntervals.size(); i != e; ++i)
delete VirtRegIntervals[TargetRegisterInfo::index2VirtReg(i)];
VirtRegIntervals.clear();
RegMaskSlots.clear();
RegMaskBits.clear();
RegMaskBlocks.clear();
for (unsigned i = 0, e = RegUnitRanges.size(); i != e; ++i)
delete RegUnitRanges[i];
RegUnitRanges.clear();
// Release VNInfo memory regions, VNInfo objects don't need to be dtor'd.
VNInfoAllocator.Reset();
}
/// runOnMachineFunction - calculates LiveIntervals
///
bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
MF = &fn;
MRI = &MF->getRegInfo();
TRI = MF->getSubtarget().getRegisterInfo();
TII = MF->getSubtarget().getInstrInfo();
AA = &getAnalysis<AliasAnalysis>();
Indexes = &getAnalysis<SlotIndexes>();
DomTree = &getAnalysis<MachineDominatorTree>();
if (!LRCalc)
LRCalc = new LiveRangeCalc();
// Allocate space for all virtual registers.
VirtRegIntervals.resize(MRI->getNumVirtRegs());
computeVirtRegs();
computeRegMasks();
computeLiveInRegUnits();
if (EnablePrecomputePhysRegs) {
// For stress testing, precompute live ranges of all physical register
// units, including reserved registers.
for (unsigned i = 0, e = TRI->getNumRegUnits(); i != e; ++i)
getRegUnit(i);
}
DEBUG(dump());
return true;
}
/// print - Implement the dump method.
void LiveIntervals::print(raw_ostream &OS, const Module* ) const {
OS << "********** INTERVALS **********\n";
// Dump the regunits.
for (unsigned i = 0, e = RegUnitRanges.size(); i != e; ++i)
if (LiveRange *LR = RegUnitRanges[i])
OS << PrintRegUnit(i, TRI) << ' ' << *LR << '\n';
// Dump the virtregs.
for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
if (hasInterval(Reg))
OS << getInterval(Reg) << '\n';
}
OS << "RegMasks:";
for (unsigned i = 0, e = RegMaskSlots.size(); i != e; ++i)
OS << ' ' << RegMaskSlots[i];
OS << '\n';
printInstrs(OS);
}
void LiveIntervals::printInstrs(raw_ostream &OS) const {
OS << "********** MACHINEINSTRS **********\n";
MF->print(OS, Indexes);
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void LiveIntervals::dumpInstrs() const {
printInstrs(dbgs());
}
#endif
LiveInterval* LiveIntervals::createInterval(unsigned reg) {
float Weight = TargetRegisterInfo::isPhysicalRegister(reg) ?
llvm::huge_valf : 0.0F;
return new LiveInterval(reg, Weight);
}
/// computeVirtRegInterval - Compute the live interval of a virtual register,
/// based on defs and uses.
void LiveIntervals::computeVirtRegInterval(LiveInterval &LI) {
assert(LRCalc && "LRCalc not initialized.");
assert(LI.empty() && "Should only compute empty intervals.");
LRCalc->reset(MF, getSlotIndexes(), DomTree, &getVNInfoAllocator());
LRCalc->createDeadDefs(LI);
LRCalc->extendToUses(LI);
computeDeadValues(&LI, LI, nullptr, nullptr);
}
void LiveIntervals::computeVirtRegs() {
for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
if (MRI->reg_nodbg_empty(Reg))
continue;
createAndComputeVirtRegInterval(Reg);
}
}
void LiveIntervals::computeRegMasks() {
RegMaskBlocks.resize(MF->getNumBlockIDs());
// Find all instructions with regmask operands.
for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
MBBI != E; ++MBBI) {
MachineBasicBlock *MBB = MBBI;
std::pair<unsigned, unsigned> &RMB = RegMaskBlocks[MBB->getNumber()];
RMB.first = RegMaskSlots.size();
for (MachineBasicBlock::iterator MI = MBB->begin(), ME = MBB->end();
MI != ME; ++MI)
for (MIOperands MO(MI); MO.isValid(); ++MO) {
if (!MO->isRegMask())
continue;
RegMaskSlots.push_back(Indexes->getInstructionIndex(MI).getRegSlot());
RegMaskBits.push_back(MO->getRegMask());
}
// Compute the number of register mask instructions in this block.
RMB.second = RegMaskSlots.size() - RMB.first;
}
}
//===----------------------------------------------------------------------===//
// Register Unit Liveness
//===----------------------------------------------------------------------===//
//
// Fixed interference typically comes from ABI boundaries: Function arguments
// and return values are passed in fixed registers, and so are exception
// pointers entering landing pads. Certain instructions require values to be
// present in specific registers. That is also represented through fixed
// interference.
//
/// computeRegUnitInterval - Compute the live range of a register unit, based
/// on the uses and defs of aliasing registers. The range should be empty,
/// or contain only dead phi-defs from ABI blocks.
void LiveIntervals::computeRegUnitRange(LiveRange &LR, unsigned Unit) {
assert(LRCalc && "LRCalc not initialized.");
LRCalc->reset(MF, getSlotIndexes(), DomTree, &getVNInfoAllocator());
// The physregs aliasing Unit are the roots and their super-registers.
// Create all values as dead defs before extending to uses. Note that roots
// may share super-registers. That's OK because createDeadDefs() is
// idempotent. It is very rare for a register unit to have multiple roots, so
// uniquing super-registers is probably not worthwhile.
for (MCRegUnitRootIterator Roots(Unit, TRI); Roots.isValid(); ++Roots) {
for (MCSuperRegIterator Supers(*Roots, TRI, /*IncludeSelf=*/true);
Supers.isValid(); ++Supers) {
if (!MRI->reg_empty(*Supers))
LRCalc->createDeadDefs(LR, *Supers);
}
}
// Now extend LR to reach all uses.
// Ignore uses of reserved registers. We only track defs of those.
for (MCRegUnitRootIterator Roots(Unit, TRI); Roots.isValid(); ++Roots) {
for (MCSuperRegIterator Supers(*Roots, TRI, /*IncludeSelf=*/true);
Supers.isValid(); ++Supers) {
unsigned Reg = *Supers;
if (!MRI->isReserved(Reg) && !MRI->reg_empty(Reg))
LRCalc->extendToUses(LR, Reg);
}
}
}
/// computeLiveInRegUnits - Precompute the live ranges of any register units
/// that are live-in to an ABI block somewhere. Register values can appear
/// without a corresponding def when entering the entry block or a landing pad.
///
void LiveIntervals::computeLiveInRegUnits() {
RegUnitRanges.resize(TRI->getNumRegUnits());
DEBUG(dbgs() << "Computing live-in reg-units in ABI blocks.\n");
// Keep track of the live range sets allocated.
SmallVector<unsigned, 8> NewRanges;
// Check all basic blocks for live-ins.
for (MachineFunction::const_iterator MFI = MF->begin(), MFE = MF->end();
MFI != MFE; ++MFI) {
const MachineBasicBlock *MBB = MFI;
// We only care about ABI blocks: Entry + landing pads.
if ((MFI != MF->begin() && !MBB->isLandingPad()) || MBB->livein_empty())
continue;
// Create phi-defs at Begin for all live-in registers.
SlotIndex Begin = Indexes->getMBBStartIdx(MBB);
DEBUG(dbgs() << Begin << "\tBB#" << MBB->getNumber());
for (MachineBasicBlock::livein_iterator LII = MBB->livein_begin(),
LIE = MBB->livein_end(); LII != LIE; ++LII) {
for (MCRegUnitIterator Units(*LII, TRI); Units.isValid(); ++Units) {
unsigned Unit = *Units;
LiveRange *LR = RegUnitRanges[Unit];
if (!LR) {
LR = RegUnitRanges[Unit] = new LiveRange();
NewRanges.push_back(Unit);
}
VNInfo *VNI = LR->createDeadDef(Begin, getVNInfoAllocator());
(void)VNI;
DEBUG(dbgs() << ' ' << PrintRegUnit(Unit, TRI) << '#' << VNI->id);
}
}
DEBUG(dbgs() << '\n');
}
DEBUG(dbgs() << "Created " << NewRanges.size() << " new intervals.\n");
// Compute the 'normal' part of the ranges.
for (unsigned i = 0, e = NewRanges.size(); i != e; ++i) {
unsigned Unit = NewRanges[i];
computeRegUnitRange(*RegUnitRanges[Unit], Unit);
}
}
/// shrinkToUses - After removing some uses of a register, shrink its live
/// range to just the remaining uses. This method does not compute reaching
/// defs for new uses, and it doesn't remove dead defs.
bool LiveIntervals::shrinkToUses(LiveInterval *li,
SmallVectorImpl<MachineInstr*> *dead) {
DEBUG(dbgs() << "Shrink: " << *li << '\n');
assert(TargetRegisterInfo::isVirtualRegister(li->reg)
&& "Can only shrink virtual registers");
// Find all the values used, including PHI kills.
SmallVector<std::pair<SlotIndex, VNInfo*>, 16> WorkList;
// Blocks that have already been added to WorkList as live-out.
SmallPtrSet<MachineBasicBlock*, 16> LiveOut;
// Visit all instructions reading li->reg.
for (MachineRegisterInfo::reg_instr_iterator
I = MRI->reg_instr_begin(li->reg), E = MRI->reg_instr_end();
I != E; ) {
MachineInstr *UseMI = &*(I++);
if (UseMI->isDebugValue() || !UseMI->readsVirtualRegister(li->reg))
continue;
SlotIndex Idx = getInstructionIndex(UseMI).getRegSlot();
LiveQueryResult LRQ = li->Query(Idx);
VNInfo *VNI = LRQ.valueIn();
if (!VNI) {
// This shouldn't happen: readsVirtualRegister returns true, but there is
// no live value. It is likely caused by a target getting <undef> flags
// wrong.
DEBUG(dbgs() << Idx << '\t' << *UseMI
<< "Warning: Instr claims to read non-existent value in "
<< *li << '\n');
continue;
}
// Special case: An early-clobber tied operand reads and writes the
// register one slot early.
if (VNInfo *DefVNI = LRQ.valueDefined())
Idx = DefVNI->def;
WorkList.push_back(std::make_pair(Idx, VNI));
}
// Create new live ranges with only minimal live segments per def.
LiveRange NewLR;
for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused())
continue;
NewLR.addSegment(LiveRange::Segment(VNI->def, VNI->def.getDeadSlot(), VNI));
}
// Keep track of the PHIs that are in use.
SmallPtrSet<VNInfo*, 8> UsedPHIs;
// Extend intervals to reach all uses in WorkList.
while (!WorkList.empty()) {
SlotIndex Idx = WorkList.back().first;
VNInfo *VNI = WorkList.back().second;
WorkList.pop_back();
const MachineBasicBlock *MBB = getMBBFromIndex(Idx.getPrevSlot());
SlotIndex BlockStart = getMBBStartIdx(MBB);
// Extend the live range for VNI to be live at Idx.
if (VNInfo *ExtVNI = NewLR.extendInBlock(BlockStart, Idx)) {
(void)ExtVNI;
assert(ExtVNI == VNI && "Unexpected existing value number");
// Is this a PHIDef we haven't seen before?
if (!VNI->isPHIDef() || VNI->def != BlockStart ||
!UsedPHIs.insert(VNI).second)
continue;
// The PHI is live, make sure the predecessors are live-out.
for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
if (!LiveOut.insert(*PI).second)
continue;
SlotIndex Stop = getMBBEndIdx(*PI);
// A predecessor is not required to have a live-out value for a PHI.
if (VNInfo *PVNI = li->getVNInfoBefore(Stop))
WorkList.push_back(std::make_pair(Stop, PVNI));
}
continue;
}
// VNI is live-in to MBB.
DEBUG(dbgs() << " live-in at " << BlockStart << '\n');
NewLR.addSegment(LiveRange::Segment(BlockStart, Idx, VNI));
// Make sure VNI is live-out from the predecessors.
for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
if (!LiveOut.insert(*PI).second)
continue;
SlotIndex Stop = getMBBEndIdx(*PI);
assert(li->getVNInfoBefore(Stop) == VNI &&
"Wrong value out of predecessor");
WorkList.push_back(std::make_pair(Stop, VNI));
}
}
// Handle dead values.
bool CanSeparate = false;
computeDeadValues(li, NewLR, &CanSeparate, dead);
// Move the trimmed segments back.
li->segments.swap(NewLR.segments);
DEBUG(dbgs() << "Shrunk: " << *li << '\n');
return CanSeparate;
}
void LiveIntervals::computeDeadValues(LiveInterval *li,
LiveRange &LR,
bool *CanSeparate,
SmallVectorImpl<MachineInstr*> *dead) {
for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused())
continue;
LiveRange::iterator LRI = LR.FindSegmentContaining(VNI->def);
assert(LRI != LR.end() && "Missing segment for PHI");
if (LRI->end != VNI->def.getDeadSlot())
continue;
if (VNI->isPHIDef()) {
// This is a dead PHI. Remove it.
VNI->markUnused();
LR.removeSegment(LRI->start, LRI->end);
DEBUG(dbgs() << "Dead PHI at " << VNI->def << " may separate interval\n");
if (CanSeparate)
*CanSeparate = true;
} else {
// This is a dead def. Make sure the instruction knows.
MachineInstr *MI = getInstructionFromIndex(VNI->def);
assert(MI && "No instruction defining live value");
MI->addRegisterDead(li->reg, TRI);
if (dead && MI->allDefsAreDead()) {
DEBUG(dbgs() << "All defs dead: " << VNI->def << '\t' << *MI);
dead->push_back(MI);
}
}
}
}
void LiveIntervals::extendToIndices(LiveRange &LR,
ArrayRef<SlotIndex> Indices) {
assert(LRCalc && "LRCalc not initialized.");
LRCalc->reset(MF, getSlotIndexes(), DomTree, &getVNInfoAllocator());
for (unsigned i = 0, e = Indices.size(); i != e; ++i)
LRCalc->extend(LR, Indices[i]);
}
void LiveIntervals::pruneValue(LiveInterval *LI, SlotIndex Kill,
SmallVectorImpl<SlotIndex> *EndPoints) {
LiveQueryResult LRQ = LI->Query(Kill);
VNInfo *VNI = LRQ.valueOut();
if (!VNI)
return;
MachineBasicBlock *KillMBB = Indexes->getMBBFromIndex(Kill);
SlotIndex MBBStart, MBBEnd;
std::tie(MBBStart, MBBEnd) = Indexes->getMBBRange(KillMBB);
// If VNI isn't live out from KillMBB, the value is trivially pruned.
if (LRQ.endPoint() < MBBEnd) {
LI->removeSegment(Kill, LRQ.endPoint());
if (EndPoints) EndPoints->push_back(LRQ.endPoint());
return;
}
// VNI is live out of KillMBB.
LI->removeSegment(Kill, MBBEnd);
if (EndPoints) EndPoints->push_back(MBBEnd);
// Find all blocks that are reachable from KillMBB without leaving VNI's live
// range. It is possible that KillMBB itself is reachable, so start a DFS
// from each successor.
typedef SmallPtrSet<MachineBasicBlock*, 9> VisitedTy;
VisitedTy Visited;
for (MachineBasicBlock::succ_iterator
SuccI = KillMBB->succ_begin(), SuccE = KillMBB->succ_end();
SuccI != SuccE; ++SuccI) {
for (df_ext_iterator<MachineBasicBlock*, VisitedTy>
I = df_ext_begin(*SuccI, Visited), E = df_ext_end(*SuccI, Visited);
I != E;) {
MachineBasicBlock *MBB = *I;
// Check if VNI is live in to MBB.
std::tie(MBBStart, MBBEnd) = Indexes->getMBBRange(MBB);
LiveQueryResult LRQ = LI->Query(MBBStart);
if (LRQ.valueIn() != VNI) {
// This block isn't part of the VNI segment. Prune the search.
I.skipChildren();
continue;
}
// Prune the search if VNI is killed in MBB.
if (LRQ.endPoint() < MBBEnd) {
LI->removeSegment(MBBStart, LRQ.endPoint());
if (EndPoints) EndPoints->push_back(LRQ.endPoint());
I.skipChildren();
continue;
}
// VNI is live through MBB.
LI->removeSegment(MBBStart, MBBEnd);
if (EndPoints) EndPoints->push_back(MBBEnd);
++I;
}
}
}
//===----------------------------------------------------------------------===//
// Register allocator hooks.
//
void LiveIntervals::addKillFlags(const VirtRegMap *VRM) {
// Keep track of regunit ranges.
SmallVector<std::pair<LiveRange*, LiveRange::iterator>, 8> RU;
for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
if (MRI->reg_nodbg_empty(Reg))
continue;
LiveInterval *LI = &getInterval(Reg);
if (LI->empty())
continue;
// Find the regunit intervals for the assigned register. They may overlap
// the virtual register live range, cancelling any kills.
RU.clear();
for (MCRegUnitIterator Units(VRM->getPhys(Reg), TRI); Units.isValid();
++Units) {
LiveRange &RURanges = getRegUnit(*Units);
if (RURanges.empty())
continue;
RU.push_back(std::make_pair(&RURanges, RURanges.find(LI->begin()->end)));
}
// Every instruction that kills Reg corresponds to a segment range end
// point.
for (LiveInterval::iterator RI = LI->begin(), RE = LI->end(); RI != RE;
++RI) {
// A block index indicates an MBB edge.
if (RI->end.isBlock())
continue;
MachineInstr *MI = getInstructionFromIndex(RI->end);
if (!MI)
continue;
// Check if any of the regunits are live beyond the end of RI. That could
// happen when a physreg is defined as a copy of a virtreg:
//
// %EAX = COPY %vreg5
// FOO %vreg5 <--- MI, cancel kill because %EAX is live.
// BAR %EAX<kill>
//
// There should be no kill flag on FOO when %vreg5 is rewritten as %EAX.
bool CancelKill = false;
for (unsigned u = 0, e = RU.size(); u != e; ++u) {
LiveRange &RRanges = *RU[u].first;
LiveRange::iterator &I = RU[u].second;
if (I == RRanges.end())
continue;
I = RRanges.advanceTo(I, RI->end);
if (I == RRanges.end() || I->start >= RI->end)
continue;
// I is overlapping RI.
CancelKill = true;
break;
}
if (CancelKill)
MI->clearRegisterKills(Reg, nullptr);
else
MI->addRegisterKilled(Reg, nullptr);
}
}
}
MachineBasicBlock*
LiveIntervals::intervalIsInOneMBB(const LiveInterval &LI) const {
// A local live range must be fully contained inside the block, meaning it is
// defined and killed at instructions, not at block boundaries. It is not
// live in or or out of any block.
//
// It is technically possible to have a PHI-defined live range identical to a
// single block, but we are going to return false in that case.
SlotIndex Start = LI.beginIndex();
if (Start.isBlock())
return nullptr;
SlotIndex Stop = LI.endIndex();
if (Stop.isBlock())
return nullptr;
// getMBBFromIndex doesn't need to search the MBB table when both indexes
// belong to proper instructions.
MachineBasicBlock *MBB1 = Indexes->getMBBFromIndex(Start);
MachineBasicBlock *MBB2 = Indexes->getMBBFromIndex(Stop);
return MBB1 == MBB2 ? MBB1 : nullptr;
}
bool
LiveIntervals::hasPHIKill(const LiveInterval &LI, const VNInfo *VNI) const {
for (LiveInterval::const_vni_iterator I = LI.vni_begin(), E = LI.vni_end();
I != E; ++I) {
const VNInfo *PHI = *I;
if (PHI->isUnused() || !PHI->isPHIDef())
continue;
const MachineBasicBlock *PHIMBB = getMBBFromIndex(PHI->def);
// Conservatively return true instead of scanning huge predecessor lists.
if (PHIMBB->pred_size() > 100)
return true;
for (MachineBasicBlock::const_pred_iterator
PI = PHIMBB->pred_begin(), PE = PHIMBB->pred_end(); PI != PE; ++PI)
if (VNI == LI.getVNInfoBefore(Indexes->getMBBEndIdx(*PI)))
return true;
}
return false;
}
float
LiveIntervals::getSpillWeight(bool isDef, bool isUse,
const MachineBlockFrequencyInfo *MBFI,
const MachineInstr *MI) {
BlockFrequency Freq = MBFI->getBlockFreq(MI->getParent());
const float Scale = 1.0f / MBFI->getEntryFreq();
return (isDef + isUse) * (Freq.getFrequency() * Scale);
}
LiveRange::Segment
LiveIntervals::addSegmentToEndOfBlock(unsigned reg, MachineInstr* startInst) {
LiveInterval& Interval = createEmptyInterval(reg);
VNInfo* VN = Interval.getNextValue(
SlotIndex(getInstructionIndex(startInst).getRegSlot()),
getVNInfoAllocator());
LiveRange::Segment S(
SlotIndex(getInstructionIndex(startInst).getRegSlot()),
getMBBEndIdx(startInst->getParent()), VN);
Interval.addSegment(S);
return S;
}
//===----------------------------------------------------------------------===//
// Register mask functions
//===----------------------------------------------------------------------===//
bool LiveIntervals::checkRegMaskInterference(LiveInterval &LI,
BitVector &UsableRegs) {
if (LI.empty())
return false;
LiveInterval::iterator LiveI = LI.begin(), LiveE = LI.end();
// Use a smaller arrays for local live ranges.
ArrayRef<SlotIndex> Slots;
ArrayRef<const uint32_t*> Bits;
if (MachineBasicBlock *MBB = intervalIsInOneMBB(LI)) {
Slots = getRegMaskSlotsInBlock(MBB->getNumber());
Bits = getRegMaskBitsInBlock(MBB->getNumber());
} else {
Slots = getRegMaskSlots();
Bits = getRegMaskBits();
}
// We are going to enumerate all the register mask slots contained in LI.
// Start with a binary search of RegMaskSlots to find a starting point.
ArrayRef<SlotIndex>::iterator SlotI =
std::lower_bound(Slots.begin(), Slots.end(), LiveI->start);
ArrayRef<SlotIndex>::iterator SlotE = Slots.end();
// No slots in range, LI begins after the last call.
if (SlotI == SlotE)
return false;
bool Found = false;
for (;;) {
assert(*SlotI >= LiveI->start);
// Loop over all slots overlapping this segment.
while (*SlotI < LiveI->end) {
// *SlotI overlaps LI. Collect mask bits.
if (!Found) {
// This is the first overlap. Initialize UsableRegs to all ones.
UsableRegs.clear();
UsableRegs.resize(TRI->getNumRegs(), true);
Found = true;
}
// Remove usable registers clobbered by this mask.
UsableRegs.clearBitsNotInMask(Bits[SlotI-Slots.begin()]);
if (++SlotI == SlotE)
return Found;
}
// *SlotI is beyond the current LI segment.
LiveI = LI.advanceTo(LiveI, *SlotI);
if (LiveI == LiveE)
return Found;
// Advance SlotI until it overlaps.
while (*SlotI < LiveI->start)
if (++SlotI == SlotE)
return Found;
}
}
//===----------------------------------------------------------------------===//
// IntervalUpdate class.
//===----------------------------------------------------------------------===//
// HMEditor is a toolkit used by handleMove to trim or extend live intervals.
class LiveIntervals::HMEditor {
private:
LiveIntervals& LIS;
const MachineRegisterInfo& MRI;
const TargetRegisterInfo& TRI;
SlotIndex OldIdx;
SlotIndex NewIdx;
SmallPtrSet<LiveRange*, 8> Updated;
bool UpdateFlags;
public:
HMEditor(LiveIntervals& LIS, const MachineRegisterInfo& MRI,
const TargetRegisterInfo& TRI,
SlotIndex OldIdx, SlotIndex NewIdx, bool UpdateFlags)
: LIS(LIS), MRI(MRI), TRI(TRI), OldIdx(OldIdx), NewIdx(NewIdx),
UpdateFlags(UpdateFlags) {}
// FIXME: UpdateFlags is a workaround that creates live intervals for all
// physregs, even those that aren't needed for regalloc, in order to update
// kill flags. This is wasteful. Eventually, LiveVariables will strip all kill
// flags, and postRA passes will use a live register utility instead.
LiveRange *getRegUnitLI(unsigned Unit) {
if (UpdateFlags)
return &LIS.getRegUnit(Unit);
return LIS.getCachedRegUnit(Unit);
}
/// Update all live ranges touched by MI, assuming a move from OldIdx to
/// NewIdx.
void updateAllRanges(MachineInstr *MI) {
DEBUG(dbgs() << "handleMove " << OldIdx << " -> " << NewIdx << ": " << *MI);
bool hasRegMask = false;
for (MIOperands MO(MI); MO.isValid(); ++MO) {
if (MO->isRegMask())
hasRegMask = true;
if (!MO->isReg())
continue;
// Aggressively clear all kill flags.
// They are reinserted by VirtRegRewriter.
if (MO->isUse())
MO->setIsKill(false);
unsigned Reg = MO->getReg();
if (!Reg)
continue;
if (TargetRegisterInfo::isVirtualRegister(Reg)) {
LiveInterval &LI = LIS.getInterval(Reg);
updateRange(LI, Reg);
continue;
}
// For physregs, only update the regunits that actually have a
// precomputed live range.
for (MCRegUnitIterator Units(Reg, &TRI); Units.isValid(); ++Units)
if (LiveRange *LR = getRegUnitLI(*Units))
updateRange(*LR, *Units);
}
if (hasRegMask)
updateRegMaskSlots();
}
private:
/// Update a single live range, assuming an instruction has been moved from
/// OldIdx to NewIdx.
void updateRange(LiveRange &LR, unsigned Reg) {
if (!Updated.insert(&LR).second)
return;
DEBUG({
dbgs() << " ";
if (TargetRegisterInfo::isVirtualRegister(Reg))
dbgs() << PrintReg(Reg);
else
dbgs() << PrintRegUnit(Reg, &TRI);
dbgs() << ":\t" << LR << '\n';
});
if (SlotIndex::isEarlierInstr(OldIdx, NewIdx))
handleMoveDown(LR);
else
handleMoveUp(LR, Reg);
DEBUG(dbgs() << " -->\t" << LR << '\n');
LR.verify();
}
/// Update LR to reflect an instruction has been moved downwards from OldIdx
/// to NewIdx.
///
/// 1. Live def at OldIdx:
/// Move def to NewIdx, assert endpoint after NewIdx.
///
/// 2. Live def at OldIdx, killed at NewIdx:
/// Change to dead def at NewIdx.
/// (Happens when bundling def+kill together).
///
/// 3. Dead def at OldIdx:
/// Move def to NewIdx, possibly across another live value.
///
/// 4. Def at OldIdx AND at NewIdx:
/// Remove segment [OldIdx;NewIdx) and value defined at OldIdx.
/// (Happens when bundling multiple defs together).
///
/// 5. Value read at OldIdx, killed before NewIdx:
/// Extend kill to NewIdx.
///
void handleMoveDown(LiveRange &LR) {
// First look for a kill at OldIdx.
LiveRange::iterator I = LR.find(OldIdx.getBaseIndex());
LiveRange::iterator E = LR.end();
// Is LR even live at OldIdx?
if (I == E || SlotIndex::isEarlierInstr(OldIdx, I->start))
return;
// Handle a live-in value.
if (!SlotIndex::isSameInstr(I->start, OldIdx)) {
bool isKill = SlotIndex::isSameInstr(OldIdx, I->end);
// If the live-in value already extends to NewIdx, there is nothing to do.
if (!SlotIndex::isEarlierInstr(I->end, NewIdx))
return;
// Aggressively remove all kill flags from the old kill point.
// Kill flags shouldn't be used while live intervals exist, they will be
// reinserted by VirtRegRewriter.
if (MachineInstr *KillMI = LIS.getInstructionFromIndex(I->end))
for (MIBundleOperands MO(KillMI); MO.isValid(); ++MO)
if (MO->isReg() && MO->isUse())
MO->setIsKill(false);
// Adjust I->end to reach NewIdx. This may temporarily make LR invalid by
// overlapping ranges. Case 5 above.
I->end = NewIdx.getRegSlot(I->end.isEarlyClobber());
// If this was a kill, there may also be a def. Otherwise we're done.
if (!isKill)
return;
++I;
}
// Check for a def at OldIdx.
if (I == E || !SlotIndex::isSameInstr(OldIdx, I->start))
return;
// We have a def at OldIdx.
VNInfo *DefVNI = I->valno;
assert(DefVNI->def == I->start && "Inconsistent def");
DefVNI->def = NewIdx.getRegSlot(I->start.isEarlyClobber());
// If the defined value extends beyond NewIdx, just move the def down.
// This is case 1 above.
if (SlotIndex::isEarlierInstr(NewIdx, I->end)) {
I->start = DefVNI->def;
return;
}
// The remaining possibilities are now:
// 2. Live def at OldIdx, killed at NewIdx: isSameInstr(I->end, NewIdx).
// 3. Dead def at OldIdx: I->end = OldIdx.getDeadSlot().
// In either case, it is possible that there is an existing def at NewIdx.
assert((I->end == OldIdx.getDeadSlot() ||
SlotIndex::isSameInstr(I->end, NewIdx)) &&
"Cannot move def below kill");
LiveRange::iterator NewI = LR.advanceTo(I, NewIdx.getRegSlot());
if (NewI != E && SlotIndex::isSameInstr(NewI->start, NewIdx)) {
// There is an existing def at NewIdx, case 4 above. The def at OldIdx is
// coalesced into that value.
assert(NewI->valno != DefVNI && "Multiple defs of value?");
LR.removeValNo(DefVNI);
return;
}
// There was no existing def at NewIdx. Turn *I into a dead def at NewIdx.
// If the def at OldIdx was dead, we allow it to be moved across other LR
// values. The new range should be placed immediately before NewI, move any
// intermediate ranges up.
assert(NewI != I && "Inconsistent iterators");
std::copy(std::next(I), NewI, I);
*std::prev(NewI)
= LiveRange::Segment(DefVNI->def, NewIdx.getDeadSlot(), DefVNI);
}
/// Update LR to reflect an instruction has been moved upwards from OldIdx
/// to NewIdx.
///
/// 1. Live def at OldIdx:
/// Hoist def to NewIdx.
///
/// 2. Dead def at OldIdx:
/// Hoist def+end to NewIdx, possibly move across other values.
///
/// 3. Dead def at OldIdx AND existing def at NewIdx:
/// Remove value defined at OldIdx, coalescing it with existing value.
///
/// 4. Live def at OldIdx AND existing def at NewIdx:
/// Remove value defined at NewIdx, hoist OldIdx def to NewIdx.
/// (Happens when bundling multiple defs together).
///
/// 5. Value killed at OldIdx:
/// Hoist kill to NewIdx, then scan for last kill between NewIdx and
/// OldIdx.
///
void handleMoveUp(LiveRange &LR, unsigned Reg) {
// First look for a kill at OldIdx.
LiveRange::iterator I = LR.find(OldIdx.getBaseIndex());
LiveRange::iterator E = LR.end();
// Is LR even live at OldIdx?
if (I == E || SlotIndex::isEarlierInstr(OldIdx, I->start))
return;
// Handle a live-in value.
if (!SlotIndex::isSameInstr(I->start, OldIdx)) {
// If the live-in value isn't killed here, there is nothing to do.
if (!SlotIndex::isSameInstr(OldIdx, I->end))
return;
// Adjust I->end to end at NewIdx. If we are hoisting a kill above
// another use, we need to search for that use. Case 5 above.
I->end = NewIdx.getRegSlot(I->end.isEarlyClobber());
++I;
// If OldIdx also defines a value, there couldn't have been another use.
if (I == E || !SlotIndex::isSameInstr(I->start, OldIdx)) {
// No def, search for the new kill.
// This can never be an early clobber kill since there is no def.
std::prev(I)->end = findLastUseBefore(Reg).getRegSlot();
return;
}
}
// Now deal with the def at OldIdx.
assert(I != E && SlotIndex::isSameInstr(I->start, OldIdx) && "No def?");
VNInfo *DefVNI = I->valno;
assert(DefVNI->def == I->start && "Inconsistent def");
DefVNI->def = NewIdx.getRegSlot(I->start.isEarlyClobber());
// Check for an existing def at NewIdx.
LiveRange::iterator NewI = LR.find(NewIdx.getRegSlot());
if (SlotIndex::isSameInstr(NewI->start, NewIdx)) {
assert(NewI->valno != DefVNI && "Same value defined more than once?");
// There is an existing def at NewIdx.
if (I->end.isDead()) {
// Case 3: Remove the dead def at OldIdx.
LR.removeValNo(DefVNI);
return;
}
// Case 4: Replace def at NewIdx with live def at OldIdx.
I->start = DefVNI->def;
LR.removeValNo(NewI->valno);
return;
}
// There is no existing def at NewIdx. Hoist DefVNI.
if (!I->end.isDead()) {
// Leave the end point of a live def.
I->start = DefVNI->def;
return;
}
// DefVNI is a dead def. It may have been moved across other values in LR,
// so move I up to NewI. Slide [NewI;I) down one position.
std::copy_backward(NewI, I, std::next(I));
*NewI = LiveRange::Segment(DefVNI->def, NewIdx.getDeadSlot(), DefVNI);
}
void updateRegMaskSlots() {
SmallVectorImpl<SlotIndex>::iterator RI =
std::lower_bound(LIS.RegMaskSlots.begin(), LIS.RegMaskSlots.end(),
OldIdx);
assert(RI != LIS.RegMaskSlots.end() && *RI == OldIdx.getRegSlot() &&
"No RegMask at OldIdx.");
*RI = NewIdx.getRegSlot();
assert((RI == LIS.RegMaskSlots.begin() ||
SlotIndex::isEarlierInstr(*std::prev(RI), *RI)) &&
"Cannot move regmask instruction above another call");
assert((std::next(RI) == LIS.RegMaskSlots.end() ||
SlotIndex::isEarlierInstr(*RI, *std::next(RI))) &&
"Cannot move regmask instruction below another call");
}
// Return the last use of reg between NewIdx and OldIdx.
SlotIndex findLastUseBefore(unsigned Reg) {
if (TargetRegisterInfo::isVirtualRegister(Reg)) {
SlotIndex LastUse = NewIdx;
for (MachineRegisterInfo::use_instr_nodbg_iterator
UI = MRI.use_instr_nodbg_begin(Reg),
UE = MRI.use_instr_nodbg_end();
UI != UE; ++UI) {
const MachineInstr* MI = &*UI;
SlotIndex InstSlot = LIS.getSlotIndexes()->getInstructionIndex(MI);
if (InstSlot > LastUse && InstSlot < OldIdx)
LastUse = InstSlot;
}
return LastUse;
}
// This is a regunit interval, so scanning the use list could be very
// expensive. Scan upwards from OldIdx instead.
assert(NewIdx < OldIdx && "Expected upwards move");
SlotIndexes *Indexes = LIS.getSlotIndexes();
MachineBasicBlock *MBB = Indexes->getMBBFromIndex(NewIdx);
// OldIdx may not correspond to an instruction any longer, so set MII to
// point to the next instruction after OldIdx, or MBB->end().
MachineBasicBlock::iterator MII = MBB->end();
if (MachineInstr *MI = Indexes->getInstructionFromIndex(
Indexes->getNextNonNullIndex(OldIdx)))
if (MI->getParent() == MBB)
MII = MI;
MachineBasicBlock::iterator Begin = MBB->begin();
while (MII != Begin) {
if ((--MII)->isDebugValue())
continue;
SlotIndex Idx = Indexes->getInstructionIndex(MII);
// Stop searching when NewIdx is reached.
if (!SlotIndex::isEarlierInstr(NewIdx, Idx))
return NewIdx;
// Check if MII uses Reg.
for (MIBundleOperands MO(MII); MO.isValid(); ++MO)
if (MO->isReg() &&
TargetRegisterInfo::isPhysicalRegister(MO->getReg()) &&
TRI.hasRegUnit(MO->getReg(), Reg))
return Idx;
}
// Didn't reach NewIdx. It must be the first instruction in the block.
return NewIdx;
}
};
void LiveIntervals::handleMove(MachineInstr* MI, bool UpdateFlags) {
assert(!MI->isBundled() && "Can't handle bundled instructions yet.");
SlotIndex OldIndex = Indexes->getInstructionIndex(MI);
Indexes->removeMachineInstrFromMaps(MI);
SlotIndex NewIndex = Indexes->insertMachineInstrInMaps(MI);
assert(getMBBStartIdx(MI->getParent()) <= OldIndex &&
OldIndex < getMBBEndIdx(MI->getParent()) &&
"Cannot handle moves across basic block boundaries.");
HMEditor HME(*this, *MRI, *TRI, OldIndex, NewIndex, UpdateFlags);
HME.updateAllRanges(MI);
}
void LiveIntervals::handleMoveIntoBundle(MachineInstr* MI,
MachineInstr* BundleStart,
bool UpdateFlags) {
SlotIndex OldIndex = Indexes->getInstructionIndex(MI);
SlotIndex NewIndex = Indexes->getInstructionIndex(BundleStart);
HMEditor HME(*this, *MRI, *TRI, OldIndex, NewIndex, UpdateFlags);
HME.updateAllRanges(MI);
}
void
LiveIntervals::repairIntervalsInRange(MachineBasicBlock *MBB,
MachineBasicBlock::iterator Begin,
MachineBasicBlock::iterator End,
ArrayRef<unsigned> OrigRegs) {
// Find anchor points, which are at the beginning/end of blocks or at
// instructions that already have indexes.
while (Begin != MBB->begin() && !Indexes->hasIndex(Begin))
--Begin;
while (End != MBB->end() && !Indexes->hasIndex(End))
++End;
SlotIndex endIdx;
if (End == MBB->end())
endIdx = getMBBEndIdx(MBB).getPrevSlot();
else
endIdx = getInstructionIndex(End);
Indexes->repairIndexesInRange(MBB, Begin, End);
for (MachineBasicBlock::iterator I = End; I != Begin;) {
--I;
MachineInstr *MI = I;
if (MI->isDebugValue())
continue;
for (MachineInstr::const_mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end(); MOI != MOE; ++MOI) {
if (MOI->isReg() &&
TargetRegisterInfo::isVirtualRegister(MOI->getReg()) &&
!hasInterval(MOI->getReg())) {
createAndComputeVirtRegInterval(MOI->getReg());
}
}
}
for (unsigned i = 0, e = OrigRegs.size(); i != e; ++i) {
unsigned Reg = OrigRegs[i];
if (!TargetRegisterInfo::isVirtualRegister(Reg))
continue;
LiveInterval &LI = getInterval(Reg);
// FIXME: Should we support undefs that gain defs?
if (!LI.hasAtLeastOneValue())
continue;
LiveInterval::iterator LII = LI.find(endIdx);
SlotIndex lastUseIdx;
if (LII != LI.end() && LII->start < endIdx)
lastUseIdx = LII->end;
else
--LII;
for (MachineBasicBlock::iterator I = End; I != Begin;) {
--I;
MachineInstr *MI = I;
if (MI->isDebugValue())
continue;
SlotIndex instrIdx = getInstructionIndex(MI);
bool isStartValid = getInstructionFromIndex(LII->start);
bool isEndValid = getInstructionFromIndex(LII->end);
// FIXME: This doesn't currently handle early-clobber or multiple removed
// defs inside of the region to repair.
for (MachineInstr::mop_iterator OI = MI->operands_begin(),
OE = MI->operands_end(); OI != OE; ++OI) {
const MachineOperand &MO = *OI;
if (!MO.isReg() || MO.getReg() != Reg)
continue;
if (MO.isDef()) {
if (!isStartValid) {
if (LII->end.isDead()) {
SlotIndex prevStart;
if (LII != LI.begin())
prevStart = std::prev(LII)->start;
// FIXME: This could be more efficient if there was a
// removeSegment method that returned an iterator.
LI.removeSegment(*LII, true);
if (prevStart.isValid())
LII = LI.find(prevStart);
else
LII = LI.begin();
} else {
LII->start = instrIdx.getRegSlot();
LII->valno->def = instrIdx.getRegSlot();
if (MO.getSubReg() && !MO.isUndef())
lastUseIdx = instrIdx.getRegSlot();
else
lastUseIdx = SlotIndex();
continue;
}
}
if (!lastUseIdx.isValid()) {
VNInfo *VNI = LI.getNextValue(instrIdx.getRegSlot(),
VNInfoAllocator);
LiveRange::Segment S(instrIdx.getRegSlot(),
instrIdx.getDeadSlot(), VNI);
LII = LI.addSegment(S);
} else if (LII->start != instrIdx.getRegSlot()) {
VNInfo *VNI = LI.getNextValue(instrIdx.getRegSlot(),
VNInfoAllocator);
LiveRange::Segment S(instrIdx.getRegSlot(), lastUseIdx, VNI);
LII = LI.addSegment(S);
}
if (MO.getSubReg() && !MO.isUndef())
lastUseIdx = instrIdx.getRegSlot();
else
lastUseIdx = SlotIndex();
} else if (MO.isUse()) {
// FIXME: This should probably be handled outside of this branch,
// either as part of the def case (for defs inside of the region) or
// after the loop over the region.
if (!isEndValid && !LII->end.isBlock())
LII->end = instrIdx.getRegSlot();
if (!lastUseIdx.isValid())
lastUseIdx = instrIdx.getRegSlot();
}
}
}
}
}
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