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llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
Lang Hames cd339b71ff Use convenience function for consistency. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150457 91177308-0d34-0410-b5e6-96231b3b80d8
2012-02-14 03:04:29 +00:00

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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.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regalloc"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/Value.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include <algorithm>
#include <limits>
#include <cmath>
using namespace llvm;
// Hidden options for help debugging.
static cl::opt<bool> DisableReMat("disable-rematerialization",
cl::init(false), cl::Hidden);
STATISTIC(numIntervals , "Number of original intervals");
char LiveIntervals::ID = 0;
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)
void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addRequired<AliasAnalysis>();
AU.addPreserved<AliasAnalysis>();
AU.addRequired<LiveVariables>();
AU.addPreserved<LiveVariables>();
AU.addPreservedID(MachineLoopInfoID);
AU.addPreservedID(MachineDominatorsID);
AU.addPreserved<SlotIndexes>();
AU.addRequiredTransitive<SlotIndexes>();
MachineFunctionPass::getAnalysisUsage(AU);
}
void LiveIntervals::releaseMemory() {
// Free the live intervals themselves.
for (DenseMap<unsigned, LiveInterval*>::iterator I = r2iMap_.begin(),
E = r2iMap_.end(); I != E; ++I)
delete I->second;
r2iMap_.clear();
RegMaskSlots.clear();
RegMaskBits.clear();
RegMaskBlocks.clear();
// Release VNInfo memory regions, VNInfo objects don't need to be dtor'd.
VNInfoAllocator.Reset();
}
/// runOnMachineFunction - Register allocate the whole function
///
bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
mf_ = &fn;
mri_ = &mf_->getRegInfo();
tm_ = &fn.getTarget();
tri_ = tm_->getRegisterInfo();
tii_ = tm_->getInstrInfo();
aa_ = &getAnalysis<AliasAnalysis>();
lv_ = &getAnalysis<LiveVariables>();
indexes_ = &getAnalysis<SlotIndexes>();
allocatableRegs_ = tri_->getAllocatableSet(fn);
computeIntervals();
numIntervals += getNumIntervals();
DEBUG(dump());
return true;
}
/// print - Implement the dump method.
void LiveIntervals::print(raw_ostream &OS, const Module* ) const {
OS << "********** INTERVALS **********\n";
for (const_iterator I = begin(), E = end(); I != E; ++I) {
I->second->print(OS, tri_);
OS << "\n";
}
printInstrs(OS);
}
void LiveIntervals::printInstrs(raw_ostream &OS) const {
OS << "********** MACHINEINSTRS **********\n";
mf_->print(OS, indexes_);
}
void LiveIntervals::dumpInstrs() const {
printInstrs(dbgs());
}
static
bool MultipleDefsBySameMI(const MachineInstr &MI, unsigned MOIdx) {
unsigned Reg = MI.getOperand(MOIdx).getReg();
for (unsigned i = MOIdx+1, e = MI.getNumOperands(); i < e; ++i) {
const MachineOperand &MO = MI.getOperand(i);
if (!MO.isReg())
continue;
if (MO.getReg() == Reg && MO.isDef()) {
assert(MI.getOperand(MOIdx).getSubReg() != MO.getSubReg() &&
MI.getOperand(MOIdx).getSubReg() &&
(MO.getSubReg() || MO.isImplicit()));
return true;
}
}
return false;
}
/// isPartialRedef - Return true if the specified def at the specific index is
/// partially re-defining the specified live interval. A common case of this is
/// a definition of the sub-register.
bool LiveIntervals::isPartialRedef(SlotIndex MIIdx, MachineOperand &MO,
LiveInterval &interval) {
if (!MO.getSubReg() || MO.isEarlyClobber())
return false;
SlotIndex RedefIndex = MIIdx.getRegSlot();
const LiveRange *OldLR =
interval.getLiveRangeContaining(RedefIndex.getRegSlot(true));
MachineInstr *DefMI = getInstructionFromIndex(OldLR->valno->def);
if (DefMI != 0) {
return DefMI->findRegisterDefOperandIdx(interval.reg) != -1;
}
return false;
}
void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
MachineBasicBlock::iterator mi,
SlotIndex MIIdx,
MachineOperand& MO,
unsigned MOIdx,
LiveInterval &interval) {
DEBUG(dbgs() << "\t\tregister: " << PrintReg(interval.reg, tri_));
// Virtual registers may be defined multiple times (due to phi
// elimination and 2-addr elimination). Much of what we do only has to be
// done once for the vreg. We use an empty interval to detect the first
// time we see a vreg.
LiveVariables::VarInfo& vi = lv_->getVarInfo(interval.reg);
if (interval.empty()) {
// Get the Idx of the defining instructions.
SlotIndex defIndex = MIIdx.getRegSlot(MO.isEarlyClobber());
// Make sure the first definition is not a partial redefinition. Add an
// <imp-def> of the full register.
// FIXME: LiveIntervals shouldn't modify the code like this. Whoever
// created the machine instruction should annotate it with <undef> flags
// as needed. Then we can simply assert here. The REG_SEQUENCE lowering
// is the main suspect.
if (MO.getSubReg()) {
mi->addRegisterDefined(interval.reg);
// Mark all defs of interval.reg on this instruction as reading <undef>.
for (unsigned i = MOIdx, e = mi->getNumOperands(); i != e; ++i) {
MachineOperand &MO2 = mi->getOperand(i);
if (MO2.isReg() && MO2.getReg() == interval.reg && MO2.getSubReg())
MO2.setIsUndef();
}
}
VNInfo *ValNo = interval.getNextValue(defIndex, VNInfoAllocator);
assert(ValNo->id == 0 && "First value in interval is not 0?");
// Loop over all of the blocks that the vreg is defined in. There are
// two cases we have to handle here. The most common case is a vreg
// whose lifetime is contained within a basic block. In this case there
// will be a single kill, in MBB, which comes after the definition.
if (vi.Kills.size() == 1 && vi.Kills[0]->getParent() == mbb) {
// FIXME: what about dead vars?
SlotIndex killIdx;
if (vi.Kills[0] != mi)
killIdx = getInstructionIndex(vi.Kills[0]).getRegSlot();
else
killIdx = defIndex.getDeadSlot();
// If the kill happens after the definition, we have an intra-block
// live range.
if (killIdx > defIndex) {
assert(vi.AliveBlocks.empty() &&
"Shouldn't be alive across any blocks!");
LiveRange LR(defIndex, killIdx, ValNo);
interval.addRange(LR);
DEBUG(dbgs() << " +" << LR << "\n");
return;
}
}
// The other case we handle is when a virtual register lives to the end
// of the defining block, potentially live across some blocks, then is
// live into some number of blocks, but gets killed. Start by adding a
// range that goes from this definition to the end of the defining block.
LiveRange NewLR(defIndex, getMBBEndIdx(mbb), ValNo);
DEBUG(dbgs() << " +" << NewLR);
interval.addRange(NewLR);
bool PHIJoin = lv_->isPHIJoin(interval.reg);
if (PHIJoin) {
// A phi join register is killed at the end of the MBB and revived as a new
// valno in the killing blocks.
assert(vi.AliveBlocks.empty() && "Phi join can't pass through blocks");
DEBUG(dbgs() << " phi-join");
ValNo->setHasPHIKill(true);
} else {
// Iterate over all of the blocks that the variable is completely
// live in, adding [insrtIndex(begin), instrIndex(end)+4) to the
// live interval.
for (SparseBitVector<>::iterator I = vi.AliveBlocks.begin(),
E = vi.AliveBlocks.end(); I != E; ++I) {
MachineBasicBlock *aliveBlock = mf_->getBlockNumbered(*I);
LiveRange LR(getMBBStartIdx(aliveBlock), getMBBEndIdx(aliveBlock), ValNo);
interval.addRange(LR);
DEBUG(dbgs() << " +" << LR);
}
}
// Finally, this virtual register is live from the start of any killing
// block to the 'use' slot of the killing instruction.
for (unsigned i = 0, e = vi.Kills.size(); i != e; ++i) {
MachineInstr *Kill = vi.Kills[i];
SlotIndex Start = getMBBStartIdx(Kill->getParent());
SlotIndex killIdx = getInstructionIndex(Kill).getRegSlot();
// Create interval with one of a NEW value number. Note that this value
// number isn't actually defined by an instruction, weird huh? :)
if (PHIJoin) {
assert(getInstructionFromIndex(Start) == 0 &&
"PHI def index points at actual instruction.");
ValNo = interval.getNextValue(Start, VNInfoAllocator);
ValNo->setIsPHIDef(true);
}
LiveRange LR(Start, killIdx, ValNo);
interval.addRange(LR);
DEBUG(dbgs() << " +" << LR);
}
} else {
if (MultipleDefsBySameMI(*mi, MOIdx))
// Multiple defs of the same virtual register by the same instruction.
// e.g. %reg1031:5<def>, %reg1031:6<def> = VLD1q16 %reg1024<kill>, ...
// This is likely due to elimination of REG_SEQUENCE instructions. Return
// here since there is nothing to do.
return;
// If this is the second time we see a virtual register definition, it
// must be due to phi elimination or two addr elimination. If this is
// the result of two address elimination, then the vreg is one of the
// def-and-use register operand.
// It may also be partial redef like this:
// 80 %reg1041:6<def> = VSHRNv4i16 %reg1034<kill>, 12, pred:14, pred:%reg0
// 120 %reg1041:5<def> = VSHRNv4i16 %reg1039<kill>, 12, pred:14, pred:%reg0
bool PartReDef = isPartialRedef(MIIdx, MO, interval);
if (PartReDef || mi->isRegTiedToUseOperand(MOIdx)) {
// If this is a two-address definition, then we have already processed
// the live range. The only problem is that we didn't realize there
// are actually two values in the live interval. Because of this we
// need to take the LiveRegion that defines this register and split it
// into two values.
SlotIndex RedefIndex = MIIdx.getRegSlot(MO.isEarlyClobber());
const LiveRange *OldLR =
interval.getLiveRangeContaining(RedefIndex.getRegSlot(true));
VNInfo *OldValNo = OldLR->valno;
SlotIndex DefIndex = OldValNo->def.getRegSlot();
// Delete the previous value, which should be short and continuous,
// because the 2-addr copy must be in the same MBB as the redef.
interval.removeRange(DefIndex, RedefIndex);
// The new value number (#1) is defined by the instruction we claimed
// defined value #0.
VNInfo *ValNo = interval.createValueCopy(OldValNo, VNInfoAllocator);
// Value#0 is now defined by the 2-addr instruction.
OldValNo->def = RedefIndex;
// Add the new live interval which replaces the range for the input copy.
LiveRange LR(DefIndex, RedefIndex, ValNo);
DEBUG(dbgs() << " replace range with " << LR);
interval.addRange(LR);
// If this redefinition is dead, we need to add a dummy unit live
// range covering the def slot.
if (MO.isDead())
interval.addRange(LiveRange(RedefIndex, RedefIndex.getDeadSlot(),
OldValNo));
DEBUG({
dbgs() << " RESULT: ";
interval.print(dbgs(), tri_);
});
} else if (lv_->isPHIJoin(interval.reg)) {
// In the case of PHI elimination, each variable definition is only
// live until the end of the block. We've already taken care of the
// rest of the live range.
SlotIndex defIndex = MIIdx.getRegSlot();
if (MO.isEarlyClobber())
defIndex = MIIdx.getRegSlot(true);
VNInfo *ValNo = interval.getNextValue(defIndex, VNInfoAllocator);
SlotIndex killIndex = getMBBEndIdx(mbb);
LiveRange LR(defIndex, killIndex, ValNo);
interval.addRange(LR);
ValNo->setHasPHIKill(true);
DEBUG(dbgs() << " phi-join +" << LR);
} else {
llvm_unreachable("Multiply defined register");
}
}
DEBUG(dbgs() << '\n');
}
void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB,
MachineBasicBlock::iterator mi,
SlotIndex MIIdx,
MachineOperand& MO,
LiveInterval &interval) {
// A physical register cannot be live across basic block, so its
// lifetime must end somewhere in its defining basic block.
DEBUG(dbgs() << "\t\tregister: " << PrintReg(interval.reg, tri_));
SlotIndex baseIndex = MIIdx;
SlotIndex start = baseIndex.getRegSlot(MO.isEarlyClobber());
SlotIndex end = start;
// If it is not used after definition, it is considered dead at
// the instruction defining it. Hence its interval is:
// [defSlot(def), defSlot(def)+1)
// For earlyclobbers, the defSlot was pushed back one; the extra
// advance below compensates.
if (MO.isDead()) {
DEBUG(dbgs() << " dead");
end = start.getDeadSlot();
goto exit;
}
// If it is not dead on definition, it must be killed by a
// subsequent instruction. Hence its interval is:
// [defSlot(def), useSlot(kill)+1)
baseIndex = baseIndex.getNextIndex();
while (++mi != MBB->end()) {
if (mi->isDebugValue())
continue;
if (getInstructionFromIndex(baseIndex) == 0)
baseIndex = indexes_->getNextNonNullIndex(baseIndex);
if (mi->killsRegister(interval.reg, tri_)) {
DEBUG(dbgs() << " killed");
end = baseIndex.getRegSlot();
goto exit;
} else {
int DefIdx = mi->findRegisterDefOperandIdx(interval.reg,false,false,tri_);
if (DefIdx != -1) {
if (mi->isRegTiedToUseOperand(DefIdx)) {
// Two-address instruction.
end = baseIndex.getRegSlot(mi->getOperand(DefIdx).isEarlyClobber());
} else {
// Another instruction redefines the register before it is ever read.
// Then the register is essentially dead at the instruction that
// defines it. Hence its interval is:
// [defSlot(def), defSlot(def)+1)
DEBUG(dbgs() << " dead");
end = start.getDeadSlot();
}
goto exit;
}
}
baseIndex = baseIndex.getNextIndex();
}
// The only case we should have a dead physreg here without a killing or
// instruction where we know it's dead is if it is live-in to the function
// and never used. Another possible case is the implicit use of the
// physical register has been deleted by two-address pass.
end = start.getDeadSlot();
exit:
assert(start < end && "did not find end of interval?");
// Already exists? Extend old live interval.
VNInfo *ValNo = interval.getVNInfoAt(start);
bool Extend = ValNo != 0;
if (!Extend)
ValNo = interval.getNextValue(start, VNInfoAllocator);
LiveRange LR(start, end, ValNo);
interval.addRange(LR);
DEBUG(dbgs() << " +" << LR << '\n');
}
void LiveIntervals::handleRegisterDef(MachineBasicBlock *MBB,
MachineBasicBlock::iterator MI,
SlotIndex MIIdx,
MachineOperand& MO,
unsigned MOIdx) {
if (TargetRegisterInfo::isVirtualRegister(MO.getReg()))
handleVirtualRegisterDef(MBB, MI, MIIdx, MO, MOIdx,
getOrCreateInterval(MO.getReg()));
else
handlePhysicalRegisterDef(MBB, MI, MIIdx, MO,
getOrCreateInterval(MO.getReg()));
}
void LiveIntervals::handleLiveInRegister(MachineBasicBlock *MBB,
SlotIndex MIIdx,
LiveInterval &interval) {
DEBUG(dbgs() << "\t\tlivein register: " << PrintReg(interval.reg, tri_));
// Look for kills, if it reaches a def before it's killed, then it shouldn't
// be considered a livein.
MachineBasicBlock::iterator mi = MBB->begin();
MachineBasicBlock::iterator E = MBB->end();
// Skip over DBG_VALUE at the start of the MBB.
if (mi != E && mi->isDebugValue()) {
while (++mi != E && mi->isDebugValue())
;
if (mi == E)
// MBB is empty except for DBG_VALUE's.
return;
}
SlotIndex baseIndex = MIIdx;
SlotIndex start = baseIndex;
if (getInstructionFromIndex(baseIndex) == 0)
baseIndex = indexes_->getNextNonNullIndex(baseIndex);
SlotIndex end = baseIndex;
bool SeenDefUse = false;
while (mi != E) {
if (mi->killsRegister(interval.reg, tri_)) {
DEBUG(dbgs() << " killed");
end = baseIndex.getRegSlot();
SeenDefUse = true;
break;
} else if (mi->definesRegister(interval.reg, tri_)) {
// Another instruction redefines the register before it is ever read.
// Then the register is essentially dead at the instruction that defines
// it. Hence its interval is:
// [defSlot(def), defSlot(def)+1)
DEBUG(dbgs() << " dead");
end = start.getDeadSlot();
SeenDefUse = true;
break;
}
while (++mi != E && mi->isDebugValue())
// Skip over DBG_VALUE.
;
if (mi != E)
baseIndex = indexes_->getNextNonNullIndex(baseIndex);
}
// Live-in register might not be used at all.
if (!SeenDefUse) {
DEBUG(dbgs() << " live through");
end = getMBBEndIdx(MBB);
}
SlotIndex defIdx = getMBBStartIdx(MBB);
assert(getInstructionFromIndex(defIdx) == 0 &&
"PHI def index points at actual instruction.");
VNInfo *vni = interval.getNextValue(defIdx, VNInfoAllocator);
vni->setIsPHIDef(true);
LiveRange LR(start, end, vni);
interval.addRange(LR);
DEBUG(dbgs() << " +" << LR << '\n');
}
/// computeIntervals - computes the live intervals for virtual
/// registers. for some ordering of the machine instructions [1,N] a
/// live interval is an interval [i, j) where 1 <= i <= j < N for
/// which a variable is live
void LiveIntervals::computeIntervals() {
DEBUG(dbgs() << "********** COMPUTING LIVE INTERVALS **********\n"
<< "********** Function: "
<< ((Value*)mf_->getFunction())->getName() << '\n');
RegMaskBlocks.resize(mf_->getNumBlockIDs());
SmallVector<unsigned, 8> UndefUses;
for (MachineFunction::iterator MBBI = mf_->begin(), E = mf_->end();
MBBI != E; ++MBBI) {
MachineBasicBlock *MBB = MBBI;
RegMaskBlocks[MBB->getNumber()].first = RegMaskSlots.size();
if (MBB->empty())
continue;
// Track the index of the current machine instr.
SlotIndex MIIndex = getMBBStartIdx(MBB);
DEBUG(dbgs() << "BB#" << MBB->getNumber()
<< ":\t\t# derived from " << MBB->getName() << "\n");
// Create intervals for live-ins to this BB first.
for (MachineBasicBlock::livein_iterator LI = MBB->livein_begin(),
LE = MBB->livein_end(); LI != LE; ++LI) {
handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*LI));
}
// Skip over empty initial indices.
if (getInstructionFromIndex(MIIndex) == 0)
MIIndex = indexes_->getNextNonNullIndex(MIIndex);
for (MachineBasicBlock::iterator MI = MBB->begin(), miEnd = MBB->end();
MI != miEnd; ++MI) {
DEBUG(dbgs() << MIIndex << "\t" << *MI);
if (MI->isDebugValue())
continue;
assert(indexes_->getInstructionFromIndex(MIIndex) == MI &&
"Lost SlotIndex synchronization");
// Handle defs.
for (int i = MI->getNumOperands() - 1; i >= 0; --i) {
MachineOperand &MO = MI->getOperand(i);
// Collect register masks.
if (MO.isRegMask()) {
RegMaskSlots.push_back(MIIndex.getRegSlot());
RegMaskBits.push_back(MO.getRegMask());
continue;
}
if (!MO.isReg() || !MO.getReg())
continue;
// handle register defs - build intervals
if (MO.isDef())
handleRegisterDef(MBB, MI, MIIndex, MO, i);
else if (MO.isUndef())
UndefUses.push_back(MO.getReg());
}
// Move to the next instr slot.
MIIndex = indexes_->getNextNonNullIndex(MIIndex);
}
// Compute the number of register mask instructions in this block.
std::pair<unsigned, unsigned> &RMB = RegMaskBlocks[MBB->getNumber()];
RMB.second = RegMaskSlots.size() - RMB.first;;
}
// Create empty intervals for registers defined by implicit_def's (except
// for those implicit_def that define values which are liveout of their
// blocks.
for (unsigned i = 0, e = UndefUses.size(); i != e; ++i) {
unsigned UndefReg = UndefUses[i];
(void)getOrCreateInterval(UndefReg);
}
}
LiveInterval* LiveIntervals::createInterval(unsigned reg) {
float Weight = TargetRegisterInfo::isPhysicalRegister(reg) ? HUGE_VALF : 0.0F;
return new LiveInterval(reg, Weight);
}
/// dupInterval - Duplicate a live interval. The caller is responsible for
/// managing the allocated memory.
LiveInterval* LiveIntervals::dupInterval(LiveInterval *li) {
LiveInterval *NewLI = createInterval(li->reg);
NewLI->Copy(*li, mri_, getVNInfoAllocator());
return NewLI;
}
/// 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_iterator I = mri_->reg_begin(li->reg);
MachineInstr *UseMI = I.skipInstruction();) {
if (UseMI->isDebugValue() || !UseMI->readsVirtualRegister(li->reg))
continue;
SlotIndex Idx = getInstructionIndex(UseMI).getRegSlot();
// Note: This intentionally picks up the wrong VNI in case of an EC redef.
// See below.
VNInfo *VNI = li->getVNInfoBefore(Idx);
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. The getVNInfoBefore call above would have
// picked up the value defined by UseMI. Adjust the kill slot and value.
if (SlotIndex::isSameInstr(VNI->def, Idx)) {
Idx = VNI->def;
VNI = li->getVNInfoBefore(Idx);
assert(VNI && "Early-clobber tied value not available");
}
WorkList.push_back(std::make_pair(Idx, VNI));
}
// Create a new live interval with only minimal live segments per def.
LiveInterval NewLI(li->reg, 0);
for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused())
continue;
NewLI.addRange(LiveRange(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 = NewLI.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))
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))
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');
NewLI.addRange(LiveRange(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))
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;
for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused())
continue;
LiveInterval::iterator LII = NewLI.FindLiveRangeContaining(VNI->def);
assert(LII != NewLI.end() && "Missing live range for PHI");
if (LII->end != VNI->def.getDeadSlot())
continue;
if (VNI->isPHIDef()) {
// This is a dead PHI. Remove it.
VNI->setIsUnused(true);
NewLI.removeRange(*LII);
DEBUG(dbgs() << "Dead PHI at " << VNI->def << " may separate interval\n");
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);
}
}
}
// Move the trimmed ranges back.
li->ranges.swap(NewLI.ranges);
DEBUG(dbgs() << "Shrunk: " << *li << '\n');
return CanSeparate;
}
//===----------------------------------------------------------------------===//
// Register allocator hooks.
//
void LiveIntervals::addKillFlags() {
for (iterator I = begin(), E = end(); I != E; ++I) {
unsigned Reg = I->first;
if (TargetRegisterInfo::isPhysicalRegister(Reg))
continue;
if (mri_->reg_nodbg_empty(Reg))
continue;
LiveInterval *LI = I->second;
// Every instruction that kills Reg corresponds to a live 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;
MI->addRegisterKilled(Reg, NULL);
}
}
}
#ifndef NDEBUG
static bool intervalRangesSane(const LiveInterval& li) {
if (li.empty()) {
return true;
}
SlotIndex lastEnd = li.begin()->start;
for (LiveInterval::const_iterator lrItr = li.begin(), lrEnd = li.end();
lrItr != lrEnd; ++lrItr) {
const LiveRange& lr = *lrItr;
if (lastEnd > lr.start || lr.start >= lr.end)
return false;
lastEnd = lr.end;
}
return true;
}
#endif
template <typename DefSetT>
static void handleMoveDefs(LiveIntervals& lis, SlotIndex origIdx,
SlotIndex miIdx, const DefSetT& defs) {
for (typename DefSetT::const_iterator defItr = defs.begin(),
defEnd = defs.end();
defItr != defEnd; ++defItr) {
unsigned def = *defItr;
LiveInterval& li = lis.getInterval(def);
LiveRange* lr = li.getLiveRangeContaining(origIdx.getRegSlot());
assert(lr != 0 && "No range for def?");
lr->start = miIdx.getRegSlot();
lr->valno->def = miIdx.getRegSlot();
assert(intervalRangesSane(li) && "Broke live interval moving def.");
}
}
template <typename DeadDefSetT>
static void handleMoveDeadDefs(LiveIntervals& lis, SlotIndex origIdx,
SlotIndex miIdx, const DeadDefSetT& deadDefs) {
for (typename DeadDefSetT::const_iterator deadDefItr = deadDefs.begin(),
deadDefEnd = deadDefs.end();
deadDefItr != deadDefEnd; ++deadDefItr) {
unsigned deadDef = *deadDefItr;
LiveInterval& li = lis.getInterval(deadDef);
LiveRange* lr = li.getLiveRangeContaining(origIdx.getRegSlot());
assert(lr != 0 && "No range for dead def?");
assert(lr->start == origIdx.getRegSlot() && "Bad dead range start?");
assert(lr->end == origIdx.getDeadSlot() && "Bad dead range end?");
assert(lr->valno->def == origIdx.getRegSlot() && "Bad dead valno def.");
LiveRange t(*lr);
t.start = miIdx.getRegSlot();
t.valno->def = miIdx.getRegSlot();
t.end = miIdx.getDeadSlot();
li.removeRange(*lr);
li.addRange(t);
assert(intervalRangesSane(li) && "Broke live interval moving dead def.");
}
}
template <typename ECSetT>
static void handleMoveECs(LiveIntervals& lis, SlotIndex origIdx,
SlotIndex miIdx, const ECSetT& ecs) {
for (typename ECSetT::const_iterator ecItr = ecs.begin(), ecEnd = ecs.end();
ecItr != ecEnd; ++ecItr) {
unsigned ec = *ecItr;
LiveInterval& li = lis.getInterval(ec);
LiveRange* lr = li.getLiveRangeContaining(origIdx.getRegSlot(true));
assert(lr != 0 && "No range for early clobber?");
assert(lr->start == origIdx.getRegSlot(true) && "Bad EC range start?");
assert(lr->end == origIdx.getRegSlot() && "Bad EC range end.");
assert(lr->valno->def == origIdx.getRegSlot(true) && "Bad EC valno def.");
LiveRange t(*lr);
t.start = miIdx.getRegSlot(true);
t.valno->def = miIdx.getRegSlot(true);
t.end = miIdx.getRegSlot();
li.removeRange(*lr);
li.addRange(t);
assert(intervalRangesSane(li) && "Broke live interval moving EC.");
}
}
static void moveKillFlags(unsigned reg, SlotIndex oldIdx, SlotIndex newIdx,
LiveIntervals& lis,
const TargetRegisterInfo& tri) {
MachineInstr* oldKillMI = lis.getInstructionFromIndex(oldIdx);
MachineInstr* newKillMI = lis.getInstructionFromIndex(newIdx);
assert(oldKillMI->killsRegister(reg) && "Old 'kill' instr isn't a kill.");
assert(!newKillMI->killsRegister(reg) && "New kill instr is already a kill.");
oldKillMI->clearRegisterKills(reg, &tri);
newKillMI->addRegisterKilled(reg, &tri);
}
template <typename UseSetT>
static void handleMoveUses(const MachineBasicBlock *mbb,
const MachineRegisterInfo& mri,
const TargetRegisterInfo& tri,
const BitVector& reservedRegs, LiveIntervals &lis,
SlotIndex origIdx, SlotIndex miIdx,
const UseSetT &uses) {
bool movingUp = miIdx < origIdx;
for (typename UseSetT::const_iterator usesItr = uses.begin(),
usesEnd = uses.end();
usesItr != usesEnd; ++usesItr) {
unsigned use = *usesItr;
if (!lis.hasInterval(use))
continue;
if (TargetRegisterInfo::isPhysicalRegister(use) && reservedRegs.test(use))
continue;
LiveInterval& li = lis.getInterval(use);
LiveRange* lr = li.getLiveRangeBefore(origIdx.getRegSlot());
assert(lr != 0 && "No range for use?");
bool liveThrough = lr->end > origIdx.getRegSlot();
if (movingUp) {
// If moving up and liveThrough - nothing to do.
// If not live through we need to extend the range to the last use
// between the old location and the new one.
if (!liveThrough) {
SlotIndex lastUseInRange = miIdx.getRegSlot();
for (MachineRegisterInfo::use_iterator useI = mri.use_begin(use),
useE = mri.use_end();
useI != useE; ++useI) {
const MachineInstr* mopI = &*useI;
const MachineOperand& mop = useI.getOperand();
SlotIndex instSlot = lis.getSlotIndexes()->getInstructionIndex(mopI);
SlotIndex opSlot = instSlot.getRegSlot(mop.isEarlyClobber());
if (opSlot > lastUseInRange && opSlot < origIdx)
lastUseInRange = opSlot;
}
// If we found a new instr endpoint update the kill flags.
if (lastUseInRange != miIdx.getRegSlot())
moveKillFlags(use, miIdx, lastUseInRange, lis, tri);
// Fix up the range end.
lr->end = lastUseInRange;
}
} else {
// Moving down is easy - the existing live range end tells us where
// the last kill is.
if (!liveThrough) {
// Easy fix - just update the range endpoint.
lr->end = miIdx.getRegSlot();
} else {
bool liveOut = lr->end >= lis.getSlotIndexes()->getMBBEndIdx(mbb);
if (!liveOut && miIdx.getRegSlot() > lr->end) {
moveKillFlags(use, lr->end, miIdx, lis, tri);
lr->end = miIdx.getRegSlot();
}
}
}
assert(intervalRangesSane(li) && "Broke live interval moving use.");
}
}
void LiveIntervals::moveInstr(MachineBasicBlock::iterator insertPt,
MachineInstr *mi) {
MachineBasicBlock* mbb = mi->getParent();
assert((insertPt == mbb->end() || insertPt->getParent() == mbb) &&
"Cannot handle moves across basic block boundaries.");
assert(&*insertPt != mi && "No-op move requested?");
assert(!mi->isBundled() && "Can't handle bundled instructions yet.");
// Grab the original instruction index.
SlotIndex origIdx = indexes_->getInstructionIndex(mi);
// Move the machine instr and obtain its new index.
indexes_->removeMachineInstrFromMaps(mi);
mbb->splice(insertPt, mbb, mi);
SlotIndex miIdx = indexes_->insertMachineInstrInMaps(mi);
// Pick the direction.
bool movingUp = miIdx < origIdx;
// Collect the operands.
DenseSet<unsigned> uses, defs, deadDefs, ecs;
for (MachineInstr::mop_iterator mopItr = mi->operands_begin(),
mopEnd = mi->operands_end();
mopItr != mopEnd; ++mopItr) {
const MachineOperand& mop = *mopItr;
if (!mop.isReg() || mop.getReg() == 0)
continue;
unsigned reg = mop.getReg();
if (mop.readsReg() && !ecs.count(reg)) {
uses.insert(reg);
}
if (mop.isDef()) {
if (mop.isDead()) {
assert(!defs.count(reg) && "Can't mix defs with dead-defs.");
deadDefs.insert(reg);
} else if (mop.isEarlyClobber()) {
uses.erase(reg);
ecs.insert(reg);
} else {
assert(!deadDefs.count(reg) && "Can't mix defs with dead-defs.");
defs.insert(reg);
}
}
}
BitVector reservedRegs(tri_->getReservedRegs(*mbb->getParent()));
if (movingUp) {
handleMoveUses(mbb, *mri_, *tri_, reservedRegs, *this, origIdx, miIdx, uses);
handleMoveECs(*this, origIdx, miIdx, ecs);
handleMoveDeadDefs(*this, origIdx, miIdx, deadDefs);
handleMoveDefs(*this, origIdx, miIdx, defs);
} else {
handleMoveDefs(*this, origIdx, miIdx, defs);
handleMoveDeadDefs(*this, origIdx, miIdx, deadDefs);
handleMoveECs(*this, origIdx, miIdx, ecs);
handleMoveUses(mbb, *mri_, *tri_, reservedRegs, *this, origIdx, miIdx, uses);
}
}
/// getReMatImplicitUse - If the remat definition MI has one (for now, we only
/// allow one) virtual register operand, then its uses are implicitly using
/// the register. Returns the virtual register.
unsigned LiveIntervals::getReMatImplicitUse(const LiveInterval &li,
MachineInstr *MI) const {
unsigned RegOp = 0;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isUse())
continue;
unsigned Reg = MO.getReg();
if (Reg == 0 || Reg == li.reg)
continue;
if (TargetRegisterInfo::isPhysicalRegister(Reg) && !isAllocatable(Reg))
continue;
RegOp = MO.getReg();
break; // Found vreg operand - leave the loop.
}
return RegOp;
}
/// isValNoAvailableAt - Return true if the val# of the specified interval
/// which reaches the given instruction also reaches the specified use index.
bool LiveIntervals::isValNoAvailableAt(const LiveInterval &li, MachineInstr *MI,
SlotIndex UseIdx) const {
VNInfo *UValNo = li.getVNInfoAt(UseIdx);
return UValNo && UValNo == li.getVNInfoAt(getInstructionIndex(MI));
}
/// isReMaterializable - Returns true if the definition MI of the specified
/// val# of the specified interval is re-materializable.
bool
LiveIntervals::isReMaterializable(const LiveInterval &li,
const VNInfo *ValNo, MachineInstr *MI,
const SmallVectorImpl<LiveInterval*> *SpillIs,
bool &isLoad) {
if (DisableReMat)
return false;
if (!tii_->isTriviallyReMaterializable(MI, aa_))
return false;
// Target-specific code can mark an instruction as being rematerializable
// if it has one virtual reg use, though it had better be something like
// a PIC base register which is likely to be live everywhere.
unsigned ImpUse = getReMatImplicitUse(li, MI);
if (ImpUse) {
const LiveInterval &ImpLi = getInterval(ImpUse);
for (MachineRegisterInfo::use_nodbg_iterator
ri = mri_->use_nodbg_begin(li.reg), re = mri_->use_nodbg_end();
ri != re; ++ri) {
MachineInstr *UseMI = &*ri;
SlotIndex UseIdx = getInstructionIndex(UseMI);
if (li.getVNInfoAt(UseIdx) != ValNo)
continue;
if (!isValNoAvailableAt(ImpLi, MI, UseIdx))
return false;
}
// If a register operand of the re-materialized instruction is going to
// be spilled next, then it's not legal to re-materialize this instruction.
if (SpillIs)
for (unsigned i = 0, e = SpillIs->size(); i != e; ++i)
if (ImpUse == (*SpillIs)[i]->reg)
return false;
}
return true;
}
/// isReMaterializable - Returns true if every definition of MI of every
/// val# of the specified interval is re-materializable.
bool
LiveIntervals::isReMaterializable(const LiveInterval &li,
const SmallVectorImpl<LiveInterval*> *SpillIs,
bool &isLoad) {
isLoad = false;
for (LiveInterval::const_vni_iterator i = li.vni_begin(), e = li.vni_end();
i != e; ++i) {
const VNInfo *VNI = *i;
if (VNI->isUnused())
continue; // Dead val#.
// Is the def for the val# rematerializable?
MachineInstr *ReMatDefMI = getInstructionFromIndex(VNI->def);
if (!ReMatDefMI)
return false;
bool DefIsLoad = false;
if (!ReMatDefMI ||
!isReMaterializable(li, VNI, ReMatDefMI, SpillIs, DefIsLoad))
return false;
isLoad |= DefIsLoad;
}
return true;
}
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 NULL;
SlotIndex Stop = LI.endIndex();
if (Stop.isBlock())
return NULL;
// 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 : NULL;
}
float
LiveIntervals::getSpillWeight(bool isDef, bool isUse, unsigned loopDepth) {
// Limit the loop depth ridiculousness.
if (loopDepth > 200)
loopDepth = 200;
// The loop depth is used to roughly estimate the number of times the
// instruction is executed. Something like 10^d is simple, but will quickly
// overflow a float. This expression behaves like 10^d for small d, but is
// more tempered for large d. At d=200 we get 6.7e33 which leaves a bit of
// headroom before overflow.
// By the way, powf() might be unavailable here. For consistency,
// We may take pow(double,double).
float lc = std::pow(1 + (100.0 / (loopDepth + 10)), (double)loopDepth);
return (isDef + isUse) * lc;
}
LiveRange LiveIntervals::addLiveRangeToEndOfBlock(unsigned reg,
MachineInstr* startInst) {
LiveInterval& Interval = getOrCreateInterval(reg);
VNInfo* VN = Interval.getNextValue(
SlotIndex(getInstructionIndex(startInst).getRegSlot()),
getVNInfoAllocator());
VN->setHasPHIKill(true);
LiveRange LR(
SlotIndex(getInstructionIndex(startInst).getRegSlot()),
getMBBEndIdx(startInst->getParent()), VN);
Interval.addRange(LR);
return LR;
}
//===----------------------------------------------------------------------===//
// 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;
}
}
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