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llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
Evan Cheng c781a243a3 In some rare cases, the register allocator can spill registers but end up not utilizing registers at all. The fundamental problem is linearscan's backtracking can end up freeing more than one allocated registers. However, reloads and restores might be folded into uses / defs and freed registers might not be used at all. 
VirtRegMap keeps track of allocations so it knows what's not used. As a horrible hack, the stack coloring can color spill slots with *free* registers. That is, it replace reload and spills with copies from and to the free register. It unfold instructions that load and store the spill slot and replace them with register using variants.

Not yet enabled. This is part 1. More coming.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70787 91177308-0d34-0410-b5e6-96231b3b80d8
2009-05-03 18:32:42 +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 "liveintervals"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "VirtRegMap.h"
#include "llvm/Value.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/PseudoSourceValue.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include <algorithm>
#include <cmath>
using namespace llvm;
// Hidden options for help debugging.
static cl::opt<bool> DisableReMat("disable-rematerialization",
cl::init(false), cl::Hidden);
static cl::opt<bool> SplitAtBB("split-intervals-at-bb",
cl::init(true), cl::Hidden);
static cl::opt<int> SplitLimit("split-limit",
cl::init(-1), cl::Hidden);
static cl::opt<bool> EnableAggressiveRemat("aggressive-remat", cl::Hidden);
static cl::opt<bool> EnableFastSpilling("fast-spill",
cl::init(false), cl::Hidden);
STATISTIC(numIntervals, "Number of original intervals");
STATISTIC(numFolds , "Number of loads/stores folded into instructions");
STATISTIC(numSplits , "Number of intervals split");
char LiveIntervals::ID = 0;
static RegisterPass<LiveIntervals> X("liveintervals", "Live Interval Analysis");
void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<AliasAnalysis>();
AU.addPreserved<AliasAnalysis>();
AU.addPreserved<LiveVariables>();
AU.addRequired<LiveVariables>();
AU.addPreservedID(MachineLoopInfoID);
AU.addPreservedID(MachineDominatorsID);
if (!StrongPHIElim) {
AU.addPreservedID(PHIEliminationID);
AU.addRequiredID(PHIEliminationID);
}
AU.addRequiredID(TwoAddressInstructionPassID);
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;
MBB2IdxMap.clear();
Idx2MBBMap.clear();
mi2iMap_.clear();
i2miMap_.clear();
r2iMap_.clear();
// Release VNInfo memroy regions after all VNInfo objects are dtor'd.
VNInfoAllocator.Reset();
while (!ClonedMIs.empty()) {
MachineInstr *MI = ClonedMIs.back();
ClonedMIs.pop_back();
mf_->DeleteMachineInstr(MI);
}
}
void LiveIntervals::computeNumbering() {
Index2MiMap OldI2MI = i2miMap_;
std::vector<IdxMBBPair> OldI2MBB = Idx2MBBMap;
Idx2MBBMap.clear();
MBB2IdxMap.clear();
mi2iMap_.clear();
i2miMap_.clear();
FunctionSize = 0;
// Number MachineInstrs and MachineBasicBlocks.
// Initialize MBB indexes to a sentinal.
MBB2IdxMap.resize(mf_->getNumBlockIDs(), std::make_pair(~0U,~0U));
unsigned MIIndex = 0;
for (MachineFunction::iterator MBB = mf_->begin(), E = mf_->end();
MBB != E; ++MBB) {
unsigned StartIdx = MIIndex;
// Insert an empty slot at the beginning of each block.
MIIndex += InstrSlots::NUM;
i2miMap_.push_back(0);
for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
I != E; ++I) {
bool inserted = mi2iMap_.insert(std::make_pair(I, MIIndex)).second;
assert(inserted && "multiple MachineInstr -> index mappings");
inserted = true;
i2miMap_.push_back(I);
MIIndex += InstrSlots::NUM;
FunctionSize++;
// Insert max(1, numdefs) empty slots after every instruction.
unsigned Slots = I->getDesc().getNumDefs();
if (Slots == 0)
Slots = 1;
MIIndex += InstrSlots::NUM * Slots;
while (Slots--)
i2miMap_.push_back(0);
}
// Set the MBB2IdxMap entry for this MBB.
MBB2IdxMap[MBB->getNumber()] = std::make_pair(StartIdx, MIIndex - 1);
Idx2MBBMap.push_back(std::make_pair(StartIdx, MBB));
}
std::sort(Idx2MBBMap.begin(), Idx2MBBMap.end(), Idx2MBBCompare());
if (!OldI2MI.empty())
for (iterator OI = begin(), OE = end(); OI != OE; ++OI) {
for (LiveInterval::iterator LI = OI->second->begin(),
LE = OI->second->end(); LI != LE; ++LI) {
// Remap the start index of the live range to the corresponding new
// number, or our best guess at what it _should_ correspond to if the
// original instruction has been erased. This is either the following
// instruction or its predecessor.
unsigned index = LI->start / InstrSlots::NUM;
unsigned offset = LI->start % InstrSlots::NUM;
if (offset == InstrSlots::LOAD) {
std::vector<IdxMBBPair>::const_iterator I =
std::lower_bound(OldI2MBB.begin(), OldI2MBB.end(), LI->start);
// Take the pair containing the index
std::vector<IdxMBBPair>::const_iterator J =
(I == OldI2MBB.end() && OldI2MBB.size()>0) ? (I-1): I;
LI->start = getMBBStartIdx(J->second);
} else {
LI->start = mi2iMap_[OldI2MI[index]] + offset;
}
// Remap the ending index in the same way that we remapped the start,
// except for the final step where we always map to the immediately
// following instruction.
index = (LI->end - 1) / InstrSlots::NUM;
offset = LI->end % InstrSlots::NUM;
if (offset == InstrSlots::LOAD) {
// VReg dies at end of block.
std::vector<IdxMBBPair>::const_iterator I =
std::lower_bound(OldI2MBB.begin(), OldI2MBB.end(), LI->end);
--I;
LI->end = getMBBEndIdx(I->second) + 1;
} else {
unsigned idx = index;
while (index < OldI2MI.size() && !OldI2MI[index]) ++index;
if (index != OldI2MI.size())
LI->end = mi2iMap_[OldI2MI[index]] + (idx == index ? offset : 0);
else
LI->end = InstrSlots::NUM * i2miMap_.size();
}
}
for (LiveInterval::vni_iterator VNI = OI->second->vni_begin(),
VNE = OI->second->vni_end(); VNI != VNE; ++VNI) {
VNInfo* vni = *VNI;
// Remap the VNInfo def index, which works the same as the
// start indices above. VN's with special sentinel defs
// don't need to be remapped.
if (vni->def != ~0U && vni->def != ~1U) {
unsigned index = vni->def / InstrSlots::NUM;
unsigned offset = vni->def % InstrSlots::NUM;
if (offset == InstrSlots::LOAD) {
std::vector<IdxMBBPair>::const_iterator I =
std::lower_bound(OldI2MBB.begin(), OldI2MBB.end(), vni->def);
// Take the pair containing the index
std::vector<IdxMBBPair>::const_iterator J =
(I == OldI2MBB.end() && OldI2MBB.size()>0) ? (I-1): I;
vni->def = getMBBStartIdx(J->second);
} else {
vni->def = mi2iMap_[OldI2MI[index]] + offset;
}
}
// Remap the VNInfo kill indices, which works the same as
// the end indices above.
for (size_t i = 0; i < vni->kills.size(); ++i) {
// PHI kills don't need to be remapped.
if (!vni->kills[i]) continue;
unsigned index = (vni->kills[i]-1) / InstrSlots::NUM;
unsigned offset = vni->kills[i] % InstrSlots::NUM;
if (offset == InstrSlots::LOAD) {
std::vector<IdxMBBPair>::const_iterator I =
std::lower_bound(OldI2MBB.begin(), OldI2MBB.end(), vni->kills[i]);
--I;
vni->kills[i] = getMBBEndIdx(I->second);
} else {
unsigned idx = index;
while (index < OldI2MI.size() && !OldI2MI[index]) ++index;
if (index != OldI2MI.size())
vni->kills[i] = mi2iMap_[OldI2MI[index]] +
(idx == index ? offset : 0);
else
vni->kills[i] = InstrSlots::NUM * i2miMap_.size();
}
}
}
}
}
/// 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>();
allocatableRegs_ = tri_->getAllocatableSet(fn);
computeNumbering();
computeIntervals();
numIntervals += getNumIntervals();
DEBUG(dump());
return true;
}
/// print - Implement the dump method.
void LiveIntervals::print(std::ostream &O, const Module* ) const {
O << "********** INTERVALS **********\n";
for (const_iterator I = begin(), E = end(); I != E; ++I) {
I->second->print(O, tri_);
O << "\n";
}
O << "********** MACHINEINSTRS **********\n";
for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
mbbi != mbbe; ++mbbi) {
O << ((Value*)mbbi->getBasicBlock())->getName() << ":\n";
for (MachineBasicBlock::iterator mii = mbbi->begin(),
mie = mbbi->end(); mii != mie; ++mii) {
O << getInstructionIndex(mii) << '\t' << *mii;
}
}
}
/// conflictsWithPhysRegDef - Returns true if the specified register
/// is defined during the duration of the specified interval.
bool LiveIntervals::conflictsWithPhysRegDef(const LiveInterval &li,
VirtRegMap &vrm, unsigned reg) {
for (LiveInterval::Ranges::const_iterator
I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) {
for (unsigned index = getBaseIndex(I->start),
end = getBaseIndex(I->end-1) + InstrSlots::NUM; index != end;
index += InstrSlots::NUM) {
// skip deleted instructions
while (index != end && !getInstructionFromIndex(index))
index += InstrSlots::NUM;
if (index == end) break;
MachineInstr *MI = getInstructionFromIndex(index);
unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
if (tii_->isMoveInstr(*MI, SrcReg, DstReg, SrcSubReg, DstSubReg))
if (SrcReg == li.reg || DstReg == li.reg)
continue;
for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
MachineOperand& mop = MI->getOperand(i);
if (!mop.isReg())
continue;
unsigned PhysReg = mop.getReg();
if (PhysReg == 0 || PhysReg == li.reg)
continue;
if (TargetRegisterInfo::isVirtualRegister(PhysReg)) {
if (!vrm.hasPhys(PhysReg))
continue;
PhysReg = vrm.getPhys(PhysReg);
}
if (PhysReg && tri_->regsOverlap(PhysReg, reg))
return true;
}
}
}
return false;
}
/// conflictsWithPhysRegRef - Similar to conflictsWithPhysRegRef except
/// it can check use as well.
bool LiveIntervals::conflictsWithPhysRegRef(LiveInterval &li,
unsigned Reg, bool CheckUse,
SmallPtrSet<MachineInstr*,32> &JoinedCopies) {
for (LiveInterval::Ranges::const_iterator
I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) {
for (unsigned index = getBaseIndex(I->start),
end = getBaseIndex(I->end-1) + InstrSlots::NUM; index != end;
index += InstrSlots::NUM) {
// Skip deleted instructions.
MachineInstr *MI = 0;
while (index != end) {
MI = getInstructionFromIndex(index);
if (MI)
break;
index += InstrSlots::NUM;
}
if (index == end) break;
if (JoinedCopies.count(MI))
continue;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand& MO = MI->getOperand(i);
if (!MO.isReg())
continue;
if (MO.isUse() && !CheckUse)
continue;
unsigned PhysReg = MO.getReg();
if (PhysReg == 0 || TargetRegisterInfo::isVirtualRegister(PhysReg))
continue;
if (tri_->isSubRegister(Reg, PhysReg))
return true;
}
}
}
return false;
}
void LiveIntervals::printRegName(unsigned reg) const {
if (TargetRegisterInfo::isPhysicalRegister(reg))
cerr << tri_->getName(reg);
else
cerr << "%reg" << reg;
}
void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
MachineBasicBlock::iterator mi,
unsigned MIIdx, MachineOperand& MO,
unsigned MOIdx,
LiveInterval &interval) {
DOUT << "\t\tregister: "; DEBUG(printRegName(interval.reg));
LiveVariables::VarInfo& vi = lv_->getVarInfo(interval.reg);
if (mi->getOpcode() == TargetInstrInfo::IMPLICIT_DEF) {
DOUT << "is a implicit_def\n";
return;
}
// 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.
if (interval.empty()) {
// Get the Idx of the defining instructions.
unsigned defIndex = getDefIndex(MIIdx);
// Earlyclobbers move back one.
if (MO.isEarlyClobber())
defIndex = getUseIndex(MIIdx);
VNInfo *ValNo;
MachineInstr *CopyMI = NULL;
unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
if (mi->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG ||
mi->getOpcode() == TargetInstrInfo::INSERT_SUBREG ||
mi->getOpcode() == TargetInstrInfo::SUBREG_TO_REG ||
tii_->isMoveInstr(*mi, SrcReg, DstReg, SrcSubReg, DstSubReg))
CopyMI = mi;
// Earlyclobbers move back one.
ValNo = interval.getNextValue(defIndex, CopyMI, 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?
unsigned killIdx;
if (vi.Kills[0] != mi)
killIdx = getUseIndex(getInstructionIndex(vi.Kills[0]))+1;
else
killIdx = defIndex+1;
// If the kill happens after the definition, we have an intra-block
// live range.
if (killIdx > defIndex) {
assert(vi.AliveBlocks.none() &&
"Shouldn't be alive across any blocks!");
LiveRange LR(defIndex, killIdx, ValNo);
interval.addRange(LR);
DOUT << " +" << LR << "\n";
interval.addKill(ValNo, killIdx);
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)+1, ValNo);
DOUT << " +" << NewLR;
interval.addRange(NewLR);
// Iterate over all of the blocks that the variable is completely
// live in, adding [insrtIndex(begin), instrIndex(end)+4) to the
// live interval.
for (int i = vi.AliveBlocks.find_first(); i != -1;
i = vi.AliveBlocks.find_next(i)) {
LiveRange LR(getMBBStartIdx(i),
getMBBEndIdx(i)+1, // MBB ends at -1.
ValNo);
interval.addRange(LR);
DOUT << " +" << 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];
unsigned killIdx = getUseIndex(getInstructionIndex(Kill))+1;
LiveRange LR(getMBBStartIdx(Kill->getParent()),
killIdx, ValNo);
interval.addRange(LR);
interval.addKill(ValNo, killIdx);
DOUT << " +" << LR;
}
} else {
// 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.
if (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.
assert(interval.containsOneValue());
unsigned DefIndex = getDefIndex(interval.getValNumInfo(0)->def);
unsigned RedefIndex = getDefIndex(MIIdx);
if (MO.isEarlyClobber())
RedefIndex = getUseIndex(MIIdx);
const LiveRange *OldLR = interval.getLiveRangeContaining(RedefIndex-1);
VNInfo *OldValNo = OldLR->valno;
// Delete the initial 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);
// Two-address vregs should always only be redefined once. This means
// that at this point, there should be exactly one value number in it.
assert(interval.containsOneValue() && "Unexpected 2-addr liveint!");
// The new value number (#1) is defined by the instruction we claimed
// defined value #0.
VNInfo *ValNo = interval.getNextValue(OldValNo->def, OldValNo->copy,
VNInfoAllocator);
// Value#0 is now defined by the 2-addr instruction.
OldValNo->def = RedefIndex;
OldValNo->copy = 0;
if (MO.isEarlyClobber())
OldValNo->redefByEC = true;
// Add the new live interval which replaces the range for the input copy.
LiveRange LR(DefIndex, RedefIndex, ValNo);
DOUT << " replace range with " << LR;
interval.addRange(LR);
interval.addKill(ValNo, RedefIndex);
// 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+1, OldValNo));
DOUT << " RESULT: ";
interval.print(DOUT, tri_);
} else {
// Otherwise, this must be because of phi elimination. If this is the
// first redefinition of the vreg that we have seen, go back and change
// the live range in the PHI block to be a different value number.
if (interval.containsOneValue()) {
assert(vi.Kills.size() == 1 &&
"PHI elimination vreg should have one kill, the PHI itself!");
// Remove the old range that we now know has an incorrect number.
VNInfo *VNI = interval.getValNumInfo(0);
MachineInstr *Killer = vi.Kills[0];
unsigned Start = getMBBStartIdx(Killer->getParent());
unsigned End = getUseIndex(getInstructionIndex(Killer))+1;
DOUT << " Removing [" << Start << "," << End << "] from: ";
interval.print(DOUT, tri_); DOUT << "\n";
interval.removeRange(Start, End);
VNI->hasPHIKill = true;
DOUT << " RESULT: "; interval.print(DOUT, tri_);
// Replace the interval with one of a NEW value number. Note that this
// value number isn't actually defined by an instruction, weird huh? :)
LiveRange LR(Start, End, interval.getNextValue(~0, 0, VNInfoAllocator));
DOUT << " replace range with " << LR;
interval.addRange(LR);
interval.addKill(LR.valno, End);
DOUT << " RESULT: "; interval.print(DOUT, tri_);
}
// 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.
unsigned defIndex = getDefIndex(MIIdx);
if (MO.isEarlyClobber())
defIndex = getUseIndex(MIIdx);
VNInfo *ValNo;
MachineInstr *CopyMI = NULL;
unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
if (mi->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG ||
mi->getOpcode() == TargetInstrInfo::INSERT_SUBREG ||
mi->getOpcode() == TargetInstrInfo::SUBREG_TO_REG ||
tii_->isMoveInstr(*mi, SrcReg, DstReg, SrcSubReg, DstSubReg))
CopyMI = mi;
ValNo = interval.getNextValue(defIndex, CopyMI, VNInfoAllocator);
unsigned killIndex = getMBBEndIdx(mbb) + 1;
LiveRange LR(defIndex, killIndex, ValNo);
interval.addRange(LR);
interval.addKill(ValNo, killIndex);
ValNo->hasPHIKill = true;
DOUT << " +" << LR;
}
}
DOUT << '\n';
}
void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB,
MachineBasicBlock::iterator mi,
unsigned MIIdx,
MachineOperand& MO,
LiveInterval &interval,
MachineInstr *CopyMI) {
// A physical register cannot be live across basic block, so its
// lifetime must end somewhere in its defining basic block.
DOUT << "\t\tregister: "; DEBUG(printRegName(interval.reg));
unsigned baseIndex = MIIdx;
unsigned start = getDefIndex(baseIndex);
// Earlyclobbers move back one.
if (MO.isEarlyClobber())
start = getUseIndex(MIIdx);
unsigned 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)
if (MO.isDead()) {
DOUT << " dead";
end = start + 1;
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 += InstrSlots::NUM;
while (++mi != MBB->end()) {
while (baseIndex / InstrSlots::NUM < i2miMap_.size() &&
getInstructionFromIndex(baseIndex) == 0)
baseIndex += InstrSlots::NUM;
if (mi->killsRegister(interval.reg, tri_)) {
DOUT << " killed";
end = getUseIndex(baseIndex) + 1;
goto exit;
} else {
int DefIdx = mi->findRegisterDefOperandIdx(interval.reg, false, tri_);
if (DefIdx != -1) {
if (mi->isRegTiedToUseOperand(DefIdx)) {
// Two-address instruction.
end = getDefIndex(baseIndex);
if (mi->getOperand(DefIdx).isEarlyClobber())
end = getUseIndex(baseIndex);
} 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)
DOUT << " dead";
end = start + 1;
}
goto exit;
}
}
baseIndex += InstrSlots::NUM;
}
// 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 + 1;
exit:
assert(start < end && "did not find end of interval?");
// Already exists? Extend old live interval.
LiveInterval::iterator OldLR = interval.FindLiveRangeContaining(start);
bool Extend = OldLR != interval.end();
VNInfo *ValNo = Extend
? OldLR->valno : interval.getNextValue(start, CopyMI, VNInfoAllocator);
if (MO.isEarlyClobber() && Extend)
ValNo->redefByEC = true;
LiveRange LR(start, end, ValNo);
interval.addRange(LR);
interval.addKill(LR.valno, end);
DOUT << " +" << LR << '\n';
}
void LiveIntervals::handleRegisterDef(MachineBasicBlock *MBB,
MachineBasicBlock::iterator MI,
unsigned MIIdx,
MachineOperand& MO,
unsigned MOIdx) {
if (TargetRegisterInfo::isVirtualRegister(MO.getReg()))
handleVirtualRegisterDef(MBB, MI, MIIdx, MO, MOIdx,
getOrCreateInterval(MO.getReg()));
else if (allocatableRegs_[MO.getReg()]) {
MachineInstr *CopyMI = NULL;
unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
if (MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG ||
MI->getOpcode() == TargetInstrInfo::INSERT_SUBREG ||
MI->getOpcode() == TargetInstrInfo::SUBREG_TO_REG ||
tii_->isMoveInstr(*MI, SrcReg, DstReg, SrcSubReg, DstSubReg))
CopyMI = MI;
handlePhysicalRegisterDef(MBB, MI, MIIdx, MO,
getOrCreateInterval(MO.getReg()), CopyMI);
// Def of a register also defines its sub-registers.
for (const unsigned* AS = tri_->getSubRegisters(MO.getReg()); *AS; ++AS)
// If MI also modifies the sub-register explicitly, avoid processing it
// more than once. Do not pass in TRI here so it checks for exact match.
if (!MI->modifiesRegister(*AS))
handlePhysicalRegisterDef(MBB, MI, MIIdx, MO,
getOrCreateInterval(*AS), 0);
}
}
void LiveIntervals::handleLiveInRegister(MachineBasicBlock *MBB,
unsigned MIIdx,
LiveInterval &interval, bool isAlias) {
DOUT << "\t\tlivein register: "; DEBUG(printRegName(interval.reg));
// 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();
unsigned baseIndex = MIIdx;
unsigned start = baseIndex;
while (baseIndex / InstrSlots::NUM < i2miMap_.size() &&
getInstructionFromIndex(baseIndex) == 0)
baseIndex += InstrSlots::NUM;
unsigned end = baseIndex;
bool SeenDefUse = false;
while (mi != MBB->end()) {
if (mi->killsRegister(interval.reg, tri_)) {
DOUT << " killed";
end = getUseIndex(baseIndex) + 1;
SeenDefUse = true;
goto exit;
} else if (mi->modifiesRegister(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)
DOUT << " dead";
end = getDefIndex(start) + 1;
SeenDefUse = true;
goto exit;
}
baseIndex += InstrSlots::NUM;
++mi;
if (mi != MBB->end()) {
while (baseIndex / InstrSlots::NUM < i2miMap_.size() &&
getInstructionFromIndex(baseIndex) == 0)
baseIndex += InstrSlots::NUM;
}
}
exit:
// Live-in register might not be used at all.
if (!SeenDefUse) {
if (isAlias) {
DOUT << " dead";
end = getDefIndex(MIIdx) + 1;
} else {
DOUT << " live through";
end = baseIndex;
}
}
LiveRange LR(start, end, interval.getNextValue(~0U, 0, VNInfoAllocator));
interval.addRange(LR);
interval.addKill(LR.valno, end);
DOUT << " +" << 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() {
DOUT << "********** COMPUTING LIVE INTERVALS **********\n"
<< "********** Function: "
<< ((Value*)mf_->getFunction())->getName() << '\n';
for (MachineFunction::iterator MBBI = mf_->begin(), E = mf_->end();
MBBI != E; ++MBBI) {
MachineBasicBlock *MBB = MBBI;
// Track the index of the current machine instr.
unsigned MIIndex = getMBBStartIdx(MBB);
DOUT << ((Value*)MBB->getBasicBlock())->getName() << ":\n";
MachineBasicBlock::iterator MI = MBB->begin(), miEnd = MBB->end();
// Create intervals for live-ins to this BB first.
for (MachineBasicBlock::const_livein_iterator LI = MBB->livein_begin(),
LE = MBB->livein_end(); LI != LE; ++LI) {
handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*LI));
// Multiple live-ins can alias the same register.
for (const unsigned* AS = tri_->getSubRegisters(*LI); *AS; ++AS)
if (!hasInterval(*AS))
handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*AS),
true);
}
// Skip over empty initial indices.
while (MIIndex / InstrSlots::NUM < i2miMap_.size() &&
getInstructionFromIndex(MIIndex) == 0)
MIIndex += InstrSlots::NUM;
for (; MI != miEnd; ++MI) {
DOUT << MIIndex << "\t" << *MI;
// Handle defs.
for (int i = MI->getNumOperands() - 1; i >= 0; --i) {
MachineOperand &MO = MI->getOperand(i);
// handle register defs - build intervals
if (MO.isReg() && MO.getReg() && MO.isDef()) {
handleRegisterDef(MBB, MI, MIIndex, MO, i);
}
}
// Skip over the empty slots after each instruction.
unsigned Slots = MI->getDesc().getNumDefs();
if (Slots == 0)
Slots = 1;
MIIndex += InstrSlots::NUM * Slots;
// Skip over empty indices.
while (MIIndex / InstrSlots::NUM < i2miMap_.size() &&
getInstructionFromIndex(MIIndex) == 0)
MIIndex += InstrSlots::NUM;
}
}
}
bool LiveIntervals::findLiveInMBBs(unsigned Start, unsigned End,
SmallVectorImpl<MachineBasicBlock*> &MBBs) const {
std::vector<IdxMBBPair>::const_iterator I =
std::lower_bound(Idx2MBBMap.begin(), Idx2MBBMap.end(), Start);
bool ResVal = false;
while (I != Idx2MBBMap.end()) {
if (I->first >= End)
break;
MBBs.push_back(I->second);
ResVal = true;
++I;
}
return ResVal;
}
bool LiveIntervals::findReachableMBBs(unsigned Start, unsigned End,
SmallVectorImpl<MachineBasicBlock*> &MBBs) const {
std::vector<IdxMBBPair>::const_iterator I =
std::lower_bound(Idx2MBBMap.begin(), Idx2MBBMap.end(), Start);
bool ResVal = false;
while (I != Idx2MBBMap.end()) {
if (I->first > End)
break;
MachineBasicBlock *MBB = I->second;
if (getMBBEndIdx(MBB) > End)
break;
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end(); SI != SE; ++SI)
MBBs.push_back(*SI);
ResVal = true;
++I;
}
return ResVal;
}
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, getVNInfoAllocator());
return NewLI;
}
/// getVNInfoSourceReg - Helper function that parses the specified VNInfo
/// copy field and returns the source register that defines it.
unsigned LiveIntervals::getVNInfoSourceReg(const VNInfo *VNI) const {
if (!VNI->copy)
return 0;
if (VNI->copy->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) {
// If it's extracting out of a physical register, return the sub-register.
unsigned Reg = VNI->copy->getOperand(1).getReg();
if (TargetRegisterInfo::isPhysicalRegister(Reg))
Reg = tri_->getSubReg(Reg, VNI->copy->getOperand(2).getImm());
return Reg;
} else if (VNI->copy->getOpcode() == TargetInstrInfo::INSERT_SUBREG ||
VNI->copy->getOpcode() == TargetInstrInfo::SUBREG_TO_REG)
return VNI->copy->getOperand(2).getReg();
unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
if (tii_->isMoveInstr(*VNI->copy, SrcReg, DstReg, SrcSubReg, DstSubReg))
return SrcReg;
assert(0 && "Unrecognized copy instruction!");
return 0;
}
//===----------------------------------------------------------------------===//
// Register allocator hooks.
//
/// 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;
// FIXME: For now, only remat MI with at most one register operand.
assert(!RegOp &&
"Can't rematerialize instruction with multiple register operand!");
RegOp = MO.getReg();
#ifndef NDEBUG
break;
#endif
}
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,
unsigned UseIdx) const {
unsigned Index = getInstructionIndex(MI);
VNInfo *ValNo = li.FindLiveRangeContaining(Index)->valno;
LiveInterval::const_iterator UI = li.FindLiveRangeContaining(UseIdx);
return UI != li.end() && UI->valno == ValNo;
}
/// 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,
SmallVectorImpl<LiveInterval*> &SpillIs,
bool &isLoad) {
if (DisableReMat)
return false;
if (MI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF)
return true;
int FrameIdx = 0;
if (tii_->isLoadFromStackSlot(MI, FrameIdx) &&
mf_->getFrameInfo()->isImmutableObjectIndex(FrameIdx))
// FIXME: Let target specific isReallyTriviallyReMaterializable determines
// this but remember this is not safe to fold into a two-address
// instruction.
// This is a load from fixed stack slot. It can be rematerialized.
return true;
// If the target-specific rules don't identify an instruction as
// being trivially rematerializable, use some target-independent
// rules.
if (!MI->getDesc().isRematerializable() ||
!tii_->isTriviallyReMaterializable(MI)) {
if (!EnableAggressiveRemat)
return false;
// If the instruction accesses memory but the memoperands have been lost,
// we can't analyze it.
const TargetInstrDesc &TID = MI->getDesc();
if ((TID.mayLoad() || TID.mayStore()) && MI->memoperands_empty())
return false;
// Avoid instructions obviously unsafe for remat.
if (TID.hasUnmodeledSideEffects() || TID.isNotDuplicable())
return false;
// If the instruction accesses memory and the memory could be non-constant,
// assume the instruction is not rematerializable.
for (std::list<MachineMemOperand>::const_iterator
I = MI->memoperands_begin(), E = MI->memoperands_end(); I != E; ++I){
const MachineMemOperand &MMO = *I;
if (MMO.isVolatile() || MMO.isStore())
return false;
const Value *V = MMO.getValue();
if (!V)
return false;
if (const PseudoSourceValue *PSV = dyn_cast<PseudoSourceValue>(V)) {
if (!PSV->isConstant(mf_->getFrameInfo()))
return false;
} else if (!aa_->pointsToConstantMemory(V))
return false;
}
// If any of the registers accessed are non-constant, conservatively assume
// the instruction is not rematerializable.
unsigned ImpUse = 0;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (MO.isReg()) {
unsigned Reg = MO.getReg();
if (Reg == 0)
continue;
if (TargetRegisterInfo::isPhysicalRegister(Reg))
return false;
// Only allow one def, and that in the first operand.
if (MO.isDef() != (i == 0))
return false;
// Only allow constant-valued registers.
bool IsLiveIn = mri_->isLiveIn(Reg);
MachineRegisterInfo::def_iterator I = mri_->def_begin(Reg),
E = mri_->def_end();
// For the def, it should be the only def of that register.
if (MO.isDef() && (next(I) != E || IsLiveIn))
return false;
if (MO.isUse()) {
// Only allow one use other register use, as that's all the
// remat mechanisms support currently.
if (Reg != li.reg) {
if (ImpUse == 0)
ImpUse = Reg;
else if (Reg != ImpUse)
return false;
}
// For the use, there should be only one associated def.
if (I != E && (next(I) != E || IsLiveIn))
return false;
}
}
}
}
unsigned ImpUse = getReMatImplicitUse(li, MI);
if (ImpUse) {
const LiveInterval &ImpLi = getInterval(ImpUse);
for (MachineRegisterInfo::use_iterator ri = mri_->use_begin(li.reg),
re = mri_->use_end(); ri != re; ++ri) {
MachineInstr *UseMI = &*ri;
unsigned UseIdx = getInstructionIndex(UseMI);
if (li.FindLiveRangeContaining(UseIdx)->valno != 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.
for (unsigned i = 0, e = SpillIs.size(); i != e; ++i)
if (ImpUse == SpillIs[i]->reg)
return false;
}
return true;
}
/// 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) {
SmallVector<LiveInterval*, 4> Dummy1;
bool Dummy2;
return isReMaterializable(li, ValNo, MI, Dummy1, Dummy2);
}
/// isReMaterializable - Returns true if every definition of MI of every
/// val# of the specified interval is re-materializable.
bool LiveIntervals::isReMaterializable(const LiveInterval &li,
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;
unsigned DefIdx = VNI->def;
if (DefIdx == ~1U)
continue; // Dead val#.
// Is the def for the val# rematerializable?
if (DefIdx == ~0u)
return false;
MachineInstr *ReMatDefMI = getInstructionFromIndex(DefIdx);
bool DefIsLoad = false;
if (!ReMatDefMI ||
!isReMaterializable(li, VNI, ReMatDefMI, SpillIs, DefIsLoad))
return false;
isLoad |= DefIsLoad;
}
return true;
}
/// FilterFoldedOps - Filter out two-address use operands. Return
/// true if it finds any issue with the operands that ought to prevent
/// folding.
static bool FilterFoldedOps(MachineInstr *MI,
SmallVector<unsigned, 2> &Ops,
unsigned &MRInfo,
SmallVector<unsigned, 2> &FoldOps) {
MRInfo = 0;
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
unsigned OpIdx = Ops[i];
MachineOperand &MO = MI->getOperand(OpIdx);
// FIXME: fold subreg use.
if (MO.getSubReg())
return true;
if (MO.isDef())
MRInfo |= (unsigned)VirtRegMap::isMod;
else {
// Filter out two-address use operand(s).
if (MI->isRegTiedToDefOperand(OpIdx)) {
MRInfo = VirtRegMap::isModRef;
continue;
}
MRInfo |= (unsigned)VirtRegMap::isRef;
}
FoldOps.push_back(OpIdx);
}
return false;
}
/// tryFoldMemoryOperand - Attempts to fold either a spill / restore from
/// slot / to reg or any rematerialized load into ith operand of specified
/// MI. If it is successul, MI is updated with the newly created MI and
/// returns true.
bool LiveIntervals::tryFoldMemoryOperand(MachineInstr* &MI,
VirtRegMap &vrm, MachineInstr *DefMI,
unsigned InstrIdx,
SmallVector<unsigned, 2> &Ops,
bool isSS, int Slot, unsigned Reg) {
// If it is an implicit def instruction, just delete it.
if (MI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF) {
RemoveMachineInstrFromMaps(MI);
vrm.RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
++numFolds;
return true;
}
// Filter the list of operand indexes that are to be folded. Abort if
// any operand will prevent folding.
unsigned MRInfo = 0;
SmallVector<unsigned, 2> FoldOps;
if (FilterFoldedOps(MI, Ops, MRInfo, FoldOps))
return false;
// The only time it's safe to fold into a two address instruction is when
// it's folding reload and spill from / into a spill stack slot.
if (DefMI && (MRInfo & VirtRegMap::isMod))
return false;
MachineInstr *fmi = isSS ? tii_->foldMemoryOperand(*mf_, MI, FoldOps, Slot)
: tii_->foldMemoryOperand(*mf_, MI, FoldOps, DefMI);
if (fmi) {
// Remember this instruction uses the spill slot.
if (isSS) vrm.addSpillSlotUse(Slot, fmi);
// Attempt to fold the memory reference into the instruction. If
// we can do this, we don't need to insert spill code.
MachineBasicBlock &MBB = *MI->getParent();
if (isSS && !mf_->getFrameInfo()->isImmutableObjectIndex(Slot))
vrm.virtFolded(Reg, MI, fmi, (VirtRegMap::ModRef)MRInfo);
vrm.transferSpillPts(MI, fmi);
vrm.transferRestorePts(MI, fmi);
vrm.transferEmergencySpills(MI, fmi);
mi2iMap_.erase(MI);
i2miMap_[InstrIdx /InstrSlots::NUM] = fmi;
mi2iMap_[fmi] = InstrIdx;
MI = MBB.insert(MBB.erase(MI), fmi);
++numFolds;
return true;
}
return false;
}
/// canFoldMemoryOperand - Returns true if the specified load / store
/// folding is possible.
bool LiveIntervals::canFoldMemoryOperand(MachineInstr *MI,
SmallVector<unsigned, 2> &Ops,
bool ReMat) const {
// Filter the list of operand indexes that are to be folded. Abort if
// any operand will prevent folding.
unsigned MRInfo = 0;
SmallVector<unsigned, 2> FoldOps;
if (FilterFoldedOps(MI, Ops, MRInfo, FoldOps))
return false;
// It's only legal to remat for a use, not a def.
if (ReMat && (MRInfo & VirtRegMap::isMod))
return false;
return tii_->canFoldMemoryOperand(MI, FoldOps);
}
bool LiveIntervals::intervalIsInOneMBB(const LiveInterval &li) const {
SmallPtrSet<MachineBasicBlock*, 4> MBBs;
for (LiveInterval::Ranges::const_iterator
I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) {
std::vector<IdxMBBPair>::const_iterator II =
std::lower_bound(Idx2MBBMap.begin(), Idx2MBBMap.end(), I->start);
if (II == Idx2MBBMap.end())
continue;
if (I->end > II->first) // crossing a MBB.
return false;
MBBs.insert(II->second);
if (MBBs.size() > 1)
return false;
}
return true;
}
/// rewriteImplicitOps - Rewrite implicit use operands of MI (i.e. uses of
/// interval on to-be re-materialized operands of MI) with new register.
void LiveIntervals::rewriteImplicitOps(const LiveInterval &li,
MachineInstr *MI, unsigned NewVReg,
VirtRegMap &vrm) {
// There is an implicit use. That means one of the other operand is
// being remat'ed and the remat'ed instruction has li.reg as an
// use operand. Make sure we rewrite that as well.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg())
continue;
unsigned Reg = MO.getReg();
if (Reg == 0 || TargetRegisterInfo::isPhysicalRegister(Reg))
continue;
if (!vrm.isReMaterialized(Reg))
continue;
MachineInstr *ReMatMI = vrm.getReMaterializedMI(Reg);
MachineOperand *UseMO = ReMatMI->findRegisterUseOperand(li.reg);
if (UseMO)
UseMO->setReg(NewVReg);
}
}
/// rewriteInstructionForSpills, rewriteInstructionsForSpills - Helper functions
/// for addIntervalsForSpills to rewrite uses / defs for the given live range.
bool LiveIntervals::
rewriteInstructionForSpills(const LiveInterval &li, const VNInfo *VNI,
bool TrySplit, unsigned index, unsigned end, MachineInstr *MI,
MachineInstr *ReMatOrigDefMI, MachineInstr *ReMatDefMI,
unsigned Slot, int LdSlot,
bool isLoad, bool isLoadSS, bool DefIsReMat, bool CanDelete,
VirtRegMap &vrm,
const TargetRegisterClass* rc,
SmallVector<int, 4> &ReMatIds,
const MachineLoopInfo *loopInfo,
unsigned &NewVReg, unsigned ImpUse, bool &HasDef, bool &HasUse,
DenseMap<unsigned,unsigned> &MBBVRegsMap,
std::vector<LiveInterval*> &NewLIs) {
bool CanFold = false;
RestartInstruction:
for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
MachineOperand& mop = MI->getOperand(i);
if (!mop.isReg())
continue;
unsigned Reg = mop.getReg();
unsigned RegI = Reg;
if (Reg == 0 || TargetRegisterInfo::isPhysicalRegister(Reg))
continue;
if (Reg != li.reg)
continue;
bool TryFold = !DefIsReMat;
bool FoldSS = true; // Default behavior unless it's a remat.
int FoldSlot = Slot;
if (DefIsReMat) {
// If this is the rematerializable definition MI itself and
// all of its uses are rematerialized, simply delete it.
if (MI == ReMatOrigDefMI && CanDelete) {
DOUT << "\t\t\t\tErasing re-materlizable def: ";
DOUT << MI << '\n';
RemoveMachineInstrFromMaps(MI);
vrm.RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
break;
}
// If def for this use can't be rematerialized, then try folding.
// If def is rematerializable and it's a load, also try folding.
TryFold = !ReMatDefMI || (ReMatDefMI && (MI == ReMatOrigDefMI || isLoad));
if (isLoad) {
// Try fold loads (from stack slot, constant pool, etc.) into uses.
FoldSS = isLoadSS;
FoldSlot = LdSlot;
}
}
// Scan all of the operands of this instruction rewriting operands
// to use NewVReg instead of li.reg as appropriate. We do this for
// two reasons:
//
// 1. If the instr reads the same spilled vreg multiple times, we
// want to reuse the NewVReg.
// 2. If the instr is a two-addr instruction, we are required to
// keep the src/dst regs pinned.
//
// Keep track of whether we replace a use and/or def so that we can
// create the spill interval with the appropriate range.
HasUse = mop.isUse();
HasDef = mop.isDef();
SmallVector<unsigned, 2> Ops;
Ops.push_back(i);
for (unsigned j = i+1, e = MI->getNumOperands(); j != e; ++j) {
const MachineOperand &MOj = MI->getOperand(j);
if (!MOj.isReg())
continue;
unsigned RegJ = MOj.getReg();
if (RegJ == 0 || TargetRegisterInfo::isPhysicalRegister(RegJ))
continue;
if (RegJ == RegI) {
Ops.push_back(j);
HasUse |= MOj.isUse();
HasDef |= MOj.isDef();
}
}
if (HasUse && !li.liveAt(getUseIndex(index)))
// Must be defined by an implicit def. It should not be spilled. Note,
// this is for correctness reason. e.g.
// 8 %reg1024<def> = IMPLICIT_DEF
// 12 %reg1024<def> = INSERT_SUBREG %reg1024<kill>, %reg1025, 2
// The live range [12, 14) are not part of the r1024 live interval since
// it's defined by an implicit def. It will not conflicts with live
// interval of r1025. Now suppose both registers are spilled, you can
// easily see a situation where both registers are reloaded before
// the INSERT_SUBREG and both target registers that would overlap.
HasUse = false;
// Create a new virtual register for the spill interval.
// Create the new register now so we can map the fold instruction
// to the new register so when it is unfolded we get the correct
// answer.
bool CreatedNewVReg = false;
if (NewVReg == 0) {
NewVReg = mri_->createVirtualRegister(rc);
vrm.grow();
CreatedNewVReg = true;
}
if (!TryFold)
CanFold = false;
else {
// Do not fold load / store here if we are splitting. We'll find an
// optimal point to insert a load / store later.
if (!TrySplit) {
if (tryFoldMemoryOperand(MI, vrm, ReMatDefMI, index,
Ops, FoldSS, FoldSlot, NewVReg)) {
// Folding the load/store can completely change the instruction in
// unpredictable ways, rescan it from the beginning.
if (FoldSS) {
// We need to give the new vreg the same stack slot as the
// spilled interval.
vrm.assignVirt2StackSlot(NewVReg, FoldSlot);
}
HasUse = false;
HasDef = false;
CanFold = false;
if (isNotInMIMap(MI))
break;
goto RestartInstruction;
}
} else {
// We'll try to fold it later if it's profitable.
CanFold = canFoldMemoryOperand(MI, Ops, DefIsReMat);
}
}
mop.setReg(NewVReg);
if (mop.isImplicit())
rewriteImplicitOps(li, MI, NewVReg, vrm);
// Reuse NewVReg for other reads.
for (unsigned j = 0, e = Ops.size(); j != e; ++j) {
MachineOperand &mopj = MI->getOperand(Ops[j]);
mopj.setReg(NewVReg);
if (mopj.isImplicit())
rewriteImplicitOps(li, MI, NewVReg, vrm);
}
if (CreatedNewVReg) {
if (DefIsReMat) {
vrm.setVirtIsReMaterialized(NewVReg, ReMatDefMI/*, CanDelete*/);
if (ReMatIds[VNI->id] == VirtRegMap::MAX_STACK_SLOT) {
// Each valnum may have its own remat id.
ReMatIds[VNI->id] = vrm.assignVirtReMatId(NewVReg);
} else {
vrm.assignVirtReMatId(NewVReg, ReMatIds[VNI->id]);
}
if (!CanDelete || (HasUse && HasDef)) {
// If this is a two-addr instruction then its use operands are
// rematerializable but its def is not. It should be assigned a
// stack slot.
vrm.assignVirt2StackSlot(NewVReg, Slot);
}
} else {
vrm.assignVirt2StackSlot(NewVReg, Slot);
}
} else if (HasUse && HasDef &&
vrm.getStackSlot(NewVReg) == VirtRegMap::NO_STACK_SLOT) {
// If this interval hasn't been assigned a stack slot (because earlier
// def is a deleted remat def), do it now.
assert(Slot != VirtRegMap::NO_STACK_SLOT);
vrm.assignVirt2StackSlot(NewVReg, Slot);
}
// Re-matting an instruction with virtual register use. Add the
// register as an implicit use on the use MI.
if (DefIsReMat && ImpUse)
MI->addOperand(MachineOperand::CreateReg(ImpUse, false, true));
// Create a new register interval for this spill / remat.
LiveInterval &nI = getOrCreateInterval(NewVReg);
if (CreatedNewVReg) {
NewLIs.push_back(&nI);
MBBVRegsMap.insert(std::make_pair(MI->getParent()->getNumber(), NewVReg));
if (TrySplit)
vrm.setIsSplitFromReg(NewVReg, li.reg);
}
if (HasUse) {
if (CreatedNewVReg) {
LiveRange LR(getLoadIndex(index), getUseIndex(index)+1,
nI.getNextValue(~0U, 0, VNInfoAllocator));
DOUT << " +" << LR;
nI.addRange(LR);
} else {
// Extend the split live interval to this def / use.
unsigned End = getUseIndex(index)+1;
LiveRange LR(nI.ranges[nI.ranges.size()-1].end, End,
nI.getValNumInfo(nI.getNumValNums()-1));
DOUT << " +" << LR;
nI.addRange(LR);
}
}
if (HasDef) {
LiveRange LR(getDefIndex(index), getStoreIndex(index),
nI.getNextValue(~0U, 0, VNInfoAllocator));
DOUT << " +" << LR;
nI.addRange(LR);
}
DOUT << "\t\t\t\tAdded new interval: ";
nI.print(DOUT, tri_);
DOUT << '\n';
}
return CanFold;
}
bool LiveIntervals::anyKillInMBBAfterIdx(const LiveInterval &li,
const VNInfo *VNI,
MachineBasicBlock *MBB, unsigned Idx) const {
unsigned End = getMBBEndIdx(MBB);
for (unsigned j = 0, ee = VNI->kills.size(); j != ee; ++j) {
unsigned KillIdx = VNI->kills[j];
if (KillIdx > Idx && KillIdx < End)
return true;
}
return false;
}
/// RewriteInfo - Keep track of machine instrs that will be rewritten
/// during spilling.
namespace {
struct RewriteInfo {
unsigned Index;
MachineInstr *MI;
bool HasUse;
bool HasDef;
RewriteInfo(unsigned i, MachineInstr *mi, bool u, bool d)
: Index(i), MI(mi), HasUse(u), HasDef(d) {}
};
struct RewriteInfoCompare {
bool operator()(const RewriteInfo &LHS, const RewriteInfo &RHS) const {
return LHS.Index < RHS.Index;
}
};
}
void LiveIntervals::
rewriteInstructionsForSpills(const LiveInterval &li, bool TrySplit,
LiveInterval::Ranges::const_iterator &I,
MachineInstr *ReMatOrigDefMI, MachineInstr *ReMatDefMI,
unsigned Slot, int LdSlot,
bool isLoad, bool isLoadSS, bool DefIsReMat, bool CanDelete,
VirtRegMap &vrm,
const TargetRegisterClass* rc,
SmallVector<int, 4> &ReMatIds,
const MachineLoopInfo *loopInfo,
BitVector &SpillMBBs,
DenseMap<unsigned, std::vector<SRInfo> > &SpillIdxes,
BitVector &RestoreMBBs,
DenseMap<unsigned, std::vector<SRInfo> > &RestoreIdxes,
DenseMap<unsigned,unsigned> &MBBVRegsMap,
std::vector<LiveInterval*> &NewLIs) {
bool AllCanFold = true;
unsigned NewVReg = 0;
unsigned start = getBaseIndex(I->start);
unsigned end = getBaseIndex(I->end-1) + InstrSlots::NUM;
// First collect all the def / use in this live range that will be rewritten.
// Make sure they are sorted according to instruction index.
std::vector<RewriteInfo> RewriteMIs;
for (MachineRegisterInfo::reg_iterator ri = mri_->reg_begin(li.reg),
re = mri_->reg_end(); ri != re; ) {
MachineInstr *MI = &*ri;
MachineOperand &O = ri.getOperand();
++ri;
assert(!O.isImplicit() && "Spilling register that's used as implicit use?");
unsigned index = getInstructionIndex(MI);
if (index < start || index >= end)
continue;
if (O.isUse() && !li.liveAt(getUseIndex(index)))
// Must be defined by an implicit def. It should not be spilled. Note,
// this is for correctness reason. e.g.
// 8 %reg1024<def> = IMPLICIT_DEF
// 12 %reg1024<def> = INSERT_SUBREG %reg1024<kill>, %reg1025, 2
// The live range [12, 14) are not part of the r1024 live interval since
// it's defined by an implicit def. It will not conflicts with live
// interval of r1025. Now suppose both registers are spilled, you can
// easily see a situation where both registers are reloaded before
// the INSERT_SUBREG and both target registers that would overlap.
continue;
RewriteMIs.push_back(RewriteInfo(index, MI, O.isUse(), O.isDef()));
}
std::sort(RewriteMIs.begin(), RewriteMIs.end(), RewriteInfoCompare());
unsigned ImpUse = DefIsReMat ? getReMatImplicitUse(li, ReMatDefMI) : 0;
// Now rewrite the defs and uses.
for (unsigned i = 0, e = RewriteMIs.size(); i != e; ) {
RewriteInfo &rwi = RewriteMIs[i];
++i;
unsigned index = rwi.Index;
bool MIHasUse = rwi.HasUse;
bool MIHasDef = rwi.HasDef;
MachineInstr *MI = rwi.MI;
// If MI def and/or use the same register multiple times, then there
// are multiple entries.
unsigned NumUses = MIHasUse;
while (i != e && RewriteMIs[i].MI == MI) {
assert(RewriteMIs[i].Index == index);
bool isUse = RewriteMIs[i].HasUse;
if (isUse) ++NumUses;
MIHasUse |= isUse;
MIHasDef |= RewriteMIs[i].HasDef;
++i;
}
MachineBasicBlock *MBB = MI->getParent();
if (ImpUse && MI != ReMatDefMI) {
// Re-matting an instruction with virtual register use. Update the
// register interval's spill weight to HUGE_VALF to prevent it from
// being spilled.
LiveInterval &ImpLi = getInterval(ImpUse);
ImpLi.weight = HUGE_VALF;
}
unsigned MBBId = MBB->getNumber();
unsigned ThisVReg = 0;
if (TrySplit) {
DenseMap<unsigned,unsigned>::iterator NVI = MBBVRegsMap.find(MBBId);
if (NVI != MBBVRegsMap.end()) {
ThisVReg = NVI->second;
// One common case:
// x = use
// ...
// ...
// def = ...
// = use
// It's better to start a new interval to avoid artifically
// extend the new interval.
if (MIHasDef && !MIHasUse) {
MBBVRegsMap.erase(MBB->getNumber());
ThisVReg = 0;
}
}
}
bool IsNew = ThisVReg == 0;
if (IsNew) {
// This ends the previous live interval. If all of its def / use
// can be folded, give it a low spill weight.
if (NewVReg && TrySplit && AllCanFold) {
LiveInterval &nI = getOrCreateInterval(NewVReg);
nI.weight /= 10.0F;
}
AllCanFold = true;
}
NewVReg = ThisVReg;
bool HasDef = false;
bool HasUse = false;
bool CanFold = rewriteInstructionForSpills(li, I->valno, TrySplit,
index, end, MI, ReMatOrigDefMI, ReMatDefMI,
Slot, LdSlot, isLoad, isLoadSS, DefIsReMat,
CanDelete, vrm, rc, ReMatIds, loopInfo, NewVReg,
ImpUse, HasDef, HasUse, MBBVRegsMap, NewLIs);
if (!HasDef && !HasUse)
continue;
AllCanFold &= CanFold;
// Update weight of spill interval.
LiveInterval &nI = getOrCreateInterval(NewVReg);
if (!TrySplit) {
// The spill weight is now infinity as it cannot be spilled again.
nI.weight = HUGE_VALF;
continue;
}
// Keep track of the last def and first use in each MBB.
if (HasDef) {
if (MI != ReMatOrigDefMI || !CanDelete) {
bool HasKill = false;
if (!HasUse)
HasKill = anyKillInMBBAfterIdx(li, I->valno, MBB, getDefIndex(index));
else {
// If this is a two-address code, then this index starts a new VNInfo.
const VNInfo *VNI = li.findDefinedVNInfo(getDefIndex(index));
if (VNI)
HasKill = anyKillInMBBAfterIdx(li, VNI, MBB, getDefIndex(index));
}
DenseMap<unsigned, std::vector<SRInfo> >::iterator SII =
SpillIdxes.find(MBBId);
if (!HasKill) {
if (SII == SpillIdxes.end()) {
std::vector<SRInfo> S;
S.push_back(SRInfo(index, NewVReg, true));
SpillIdxes.insert(std::make_pair(MBBId, S));
} else if (SII->second.back().vreg != NewVReg) {
SII->second.push_back(SRInfo(index, NewVReg, true));
} else if ((int)index > SII->second.back().index) {
// If there is an earlier def and this is a two-address
// instruction, then it's not possible to fold the store (which
// would also fold the load).
SRInfo &Info = SII->second.back();
Info.index = index;
Info.canFold = !HasUse;
}
SpillMBBs.set(MBBId);
} else if (SII != SpillIdxes.end() &&
SII->second.back().vreg == NewVReg &&
(int)index > SII->second.back().index) {
// There is an earlier def that's not killed (must be two-address).
// The spill is no longer needed.
SII->second.pop_back();
if (SII->second.empty()) {
SpillIdxes.erase(MBBId);
SpillMBBs.reset(MBBId);
}
}
}
}
if (HasUse) {
DenseMap<unsigned, std::vector<SRInfo> >::iterator SII =
SpillIdxes.find(MBBId);
if (SII != SpillIdxes.end() &&
SII->second.back().vreg == NewVReg &&
(int)index > SII->second.back().index)
// Use(s) following the last def, it's not safe to fold the spill.
SII->second.back().canFold = false;
DenseMap<unsigned, std::vector<SRInfo> >::iterator RII =
RestoreIdxes.find(MBBId);
if (RII != RestoreIdxes.end() && RII->second.back().vreg == NewVReg)
// If we are splitting live intervals, only fold if it's the first
// use and there isn't another use later in the MBB.
RII->second.back().canFold = false;
else if (IsNew) {
// Only need a reload if there isn't an earlier def / use.
if (RII == RestoreIdxes.end()) {
std::vector<SRInfo> Infos;
Infos.push_back(SRInfo(index, NewVReg, true));
RestoreIdxes.insert(std::make_pair(MBBId, Infos));
} else {
RII->second.push_back(SRInfo(index, NewVReg, true));
}
RestoreMBBs.set(MBBId);
}
}
// Update spill weight.
unsigned loopDepth = loopInfo->getLoopDepth(MBB);
nI.weight += getSpillWeight(HasDef, HasUse, loopDepth);
}
if (NewVReg && TrySplit && AllCanFold) {
// If all of its def / use can be folded, give it a low spill weight.
LiveInterval &nI = getOrCreateInterval(NewVReg);
nI.weight /= 10.0F;
}
}
bool LiveIntervals::alsoFoldARestore(int Id, int index, unsigned vr,
BitVector &RestoreMBBs,
DenseMap<unsigned,std::vector<SRInfo> > &RestoreIdxes) {
if (!RestoreMBBs[Id])
return false;
std::vector<SRInfo> &Restores = RestoreIdxes[Id];
for (unsigned i = 0, e = Restores.size(); i != e; ++i)
if (Restores[i].index == index &&
Restores[i].vreg == vr &&
Restores[i].canFold)
return true;
return false;
}
void LiveIntervals::eraseRestoreInfo(int Id, int index, unsigned vr,
BitVector &RestoreMBBs,
DenseMap<unsigned,std::vector<SRInfo> > &RestoreIdxes) {
if (!RestoreMBBs[Id])
return;
std::vector<SRInfo> &Restores = RestoreIdxes[Id];
for (unsigned i = 0, e = Restores.size(); i != e; ++i)
if (Restores[i].index == index && Restores[i].vreg)
Restores[i].index = -1;
}
/// handleSpilledImpDefs - Remove IMPLICIT_DEF instructions which are being
/// spilled and create empty intervals for their uses.
void
LiveIntervals::handleSpilledImpDefs(const LiveInterval &li, VirtRegMap &vrm,
const TargetRegisterClass* rc,
std::vector<LiveInterval*> &NewLIs) {
for (MachineRegisterInfo::reg_iterator ri = mri_->reg_begin(li.reg),
re = mri_->reg_end(); ri != re; ) {
MachineOperand &O = ri.getOperand();
MachineInstr *MI = &*ri;
++ri;
if (O.isDef()) {
assert(MI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF &&
"Register def was not rewritten?");
RemoveMachineInstrFromMaps(MI);
vrm.RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
} else {
// This must be an use of an implicit_def so it's not part of the live
// interval. Create a new empty live interval for it.
// FIXME: Can we simply erase some of the instructions? e.g. Stores?
unsigned NewVReg = mri_->createVirtualRegister(rc);
vrm.grow();
vrm.setIsImplicitlyDefined(NewVReg);
NewLIs.push_back(&getOrCreateInterval(NewVReg));
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (MO.isReg() && MO.getReg() == li.reg)
MO.setReg(NewVReg);
}
}
}
}
std::vector<LiveInterval*> LiveIntervals::
addIntervalsForSpillsFast(const LiveInterval &li,
const MachineLoopInfo *loopInfo,
VirtRegMap &vrm) {
unsigned slot = vrm.assignVirt2StackSlot(li.reg);
std::vector<LiveInterval*> added;
assert(li.weight != HUGE_VALF &&
"attempt to spill already spilled interval!");
DOUT << "\t\t\t\tadding intervals for spills for interval: ";
DEBUG(li.dump());
DOUT << '\n';
const TargetRegisterClass* rc = mri_->getRegClass(li.reg);
MachineRegisterInfo::reg_iterator RI = mri_->reg_begin(li.reg);
while (RI != mri_->reg_end()) {
MachineInstr* MI = &*RI;
SmallVector<unsigned, 2> Indices;
bool HasUse = false;
bool HasDef = false;
for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
MachineOperand& mop = MI->getOperand(i);
if (!mop.isReg() || mop.getReg() != li.reg) continue;
HasUse |= MI->getOperand(i).isUse();
HasDef |= MI->getOperand(i).isDef();
Indices.push_back(i);
}
if (!tryFoldMemoryOperand(MI, vrm, NULL, getInstructionIndex(MI),
Indices, true, slot, li.reg)) {
unsigned NewVReg = mri_->createVirtualRegister(rc);
vrm.grow();
vrm.assignVirt2StackSlot(NewVReg, slot);
// create a new register for this spill
LiveInterval &nI = getOrCreateInterval(NewVReg);
// the spill weight is now infinity as it
// cannot be spilled again
nI.weight = HUGE_VALF;
// Rewrite register operands to use the new vreg.
for (SmallVectorImpl<unsigned>::iterator I = Indices.begin(),
E = Indices.end(); I != E; ++I) {
MI->getOperand(*I).setReg(NewVReg);
if (MI->getOperand(*I).isUse())
MI->getOperand(*I).setIsKill(true);
}
// Fill in the new live interval.
unsigned index = getInstructionIndex(MI);
if (HasUse) {
LiveRange LR(getLoadIndex(index), getUseIndex(index),
nI.getNextValue(~0U, 0, getVNInfoAllocator()));
DOUT << " +" << LR;
nI.addRange(LR);
vrm.addRestorePoint(NewVReg, MI);
}
if (HasDef) {
LiveRange LR(getDefIndex(index), getStoreIndex(index),
nI.getNextValue(~0U, 0, getVNInfoAllocator()));
DOUT << " +" << LR;
nI.addRange(LR);
vrm.addSpillPoint(NewVReg, true, MI);
}
added.push_back(&nI);
DOUT << "\t\t\t\tadded new interval: ";
DEBUG(nI.dump());
DOUT << '\n';
}
RI = mri_->reg_begin(li.reg);
}
return added;
}
std::vector<LiveInterval*> LiveIntervals::
addIntervalsForSpills(const LiveInterval &li,
SmallVectorImpl<LiveInterval*> &SpillIs,
const MachineLoopInfo *loopInfo, VirtRegMap &vrm) {
if (EnableFastSpilling)
return addIntervalsForSpillsFast(li, loopInfo, vrm);
assert(li.weight != HUGE_VALF &&
"attempt to spill already spilled interval!");
DOUT << "\t\t\t\tadding intervals for spills for interval: ";
li.print(DOUT, tri_);
DOUT << '\n';
// Each bit specify whether a spill is required in the MBB.
BitVector SpillMBBs(mf_->getNumBlockIDs());
DenseMap<unsigned, std::vector<SRInfo> > SpillIdxes;
BitVector RestoreMBBs(mf_->getNumBlockIDs());
DenseMap<unsigned, std::vector<SRInfo> > RestoreIdxes;
DenseMap<unsigned,unsigned> MBBVRegsMap;
std::vector<LiveInterval*> NewLIs;
const TargetRegisterClass* rc = mri_->getRegClass(li.reg);
unsigned NumValNums = li.getNumValNums();
SmallVector<MachineInstr*, 4> ReMatDefs;
ReMatDefs.resize(NumValNums, NULL);
SmallVector<MachineInstr*, 4> ReMatOrigDefs;
ReMatOrigDefs.resize(NumValNums, NULL);
SmallVector<int, 4> ReMatIds;
ReMatIds.resize(NumValNums, VirtRegMap::MAX_STACK_SLOT);
BitVector ReMatDelete(NumValNums);
unsigned Slot = VirtRegMap::MAX_STACK_SLOT;
// Spilling a split live interval. It cannot be split any further. Also,
// it's also guaranteed to be a single val# / range interval.
if (vrm.getPreSplitReg(li.reg)) {
vrm.setIsSplitFromReg(li.reg, 0);
// Unset the split kill marker on the last use.
unsigned KillIdx = vrm.getKillPoint(li.reg);
if (KillIdx) {
MachineInstr *KillMI = getInstructionFromIndex(KillIdx);
assert(KillMI && "Last use disappeared?");
int KillOp = KillMI->findRegisterUseOperandIdx(li.reg, true);
assert(KillOp != -1 && "Last use disappeared?");
KillMI->getOperand(KillOp).setIsKill(false);
}
vrm.removeKillPoint(li.reg);
bool DefIsReMat = vrm.isReMaterialized(li.reg);
Slot = vrm.getStackSlot(li.reg);
assert(Slot != VirtRegMap::MAX_STACK_SLOT);
MachineInstr *ReMatDefMI = DefIsReMat ?
vrm.getReMaterializedMI(li.reg) : NULL;
int LdSlot = 0;
bool isLoadSS = DefIsReMat && tii_->isLoadFromStackSlot(ReMatDefMI, LdSlot);
bool isLoad = isLoadSS ||
(DefIsReMat && (ReMatDefMI->getDesc().canFoldAsLoad()));
bool IsFirstRange = true;
for (LiveInterval::Ranges::const_iterator
I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) {
// If this is a split live interval with multiple ranges, it means there
// are two-address instructions that re-defined the value. Only the
// first def can be rematerialized!
if (IsFirstRange) {
// Note ReMatOrigDefMI has already been deleted.
rewriteInstructionsForSpills(li, false, I, NULL, ReMatDefMI,
Slot, LdSlot, isLoad, isLoadSS, DefIsReMat,
false, vrm, rc, ReMatIds, loopInfo,
SpillMBBs, SpillIdxes, RestoreMBBs, RestoreIdxes,
MBBVRegsMap, NewLIs);
} else {
rewriteInstructionsForSpills(li, false, I, NULL, 0,
Slot, 0, false, false, false,
false, vrm, rc, ReMatIds, loopInfo,
SpillMBBs, SpillIdxes, RestoreMBBs, RestoreIdxes,
MBBVRegsMap, NewLIs);
}
IsFirstRange = false;
}
handleSpilledImpDefs(li, vrm, rc, NewLIs);
return NewLIs;
}
bool TrySplit = SplitAtBB && !intervalIsInOneMBB(li);
if (SplitLimit != -1 && (int)numSplits >= SplitLimit)
TrySplit = false;
if (TrySplit)
++numSplits;
bool NeedStackSlot = false;
for (LiveInterval::const_vni_iterator i = li.vni_begin(), e = li.vni_end();
i != e; ++i) {
const VNInfo *VNI = *i;
unsigned VN = VNI->id;
unsigned DefIdx = VNI->def;
if (DefIdx == ~1U)
continue; // Dead val#.
// Is the def for the val# rematerializable?
MachineInstr *ReMatDefMI = (DefIdx == ~0u)
? 0 : getInstructionFromIndex(DefIdx);
bool dummy;
if (ReMatDefMI && isReMaterializable(li, VNI, ReMatDefMI, SpillIs, dummy)) {
// Remember how to remat the def of this val#.
ReMatOrigDefs[VN] = ReMatDefMI;
// Original def may be modified so we have to make a copy here.
MachineInstr *Clone = mf_->CloneMachineInstr(ReMatDefMI);
ClonedMIs.push_back(Clone);
ReMatDefs[VN] = Clone;
bool CanDelete = true;
if (VNI->hasPHIKill) {
// A kill is a phi node, not all of its uses can be rematerialized.
// It must not be deleted.
CanDelete = false;
// Need a stack slot if there is any live range where uses cannot be
// rematerialized.
NeedStackSlot = true;
}
if (CanDelete)
ReMatDelete.set(VN);
} else {
// Need a stack slot if there is any live range where uses cannot be
// rematerialized.
NeedStackSlot = true;
}
}
// One stack slot per live interval.
if (NeedStackSlot && vrm.getPreSplitReg(li.reg) == 0) {
if (vrm.getStackSlot(li.reg) == VirtRegMap::NO_STACK_SLOT)
Slot = vrm.assignVirt2StackSlot(li.reg);
// This case only occurs when the prealloc splitter has already assigned
// a stack slot to this vreg.
else
Slot = vrm.getStackSlot(li.reg);
}
// Create new intervals and rewrite defs and uses.
for (LiveInterval::Ranges::const_iterator
I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) {
MachineInstr *ReMatDefMI = ReMatDefs[I->valno->id];
MachineInstr *ReMatOrigDefMI = ReMatOrigDefs[I->valno->id];
bool DefIsReMat = ReMatDefMI != NULL;
bool CanDelete = ReMatDelete[I->valno->id];
int LdSlot = 0;
bool isLoadSS = DefIsReMat && tii_->isLoadFromStackSlot(ReMatDefMI, LdSlot);
bool isLoad = isLoadSS ||
(DefIsReMat && ReMatDefMI->getDesc().canFoldAsLoad());
rewriteInstructionsForSpills(li, TrySplit, I, ReMatOrigDefMI, ReMatDefMI,
Slot, LdSlot, isLoad, isLoadSS, DefIsReMat,
CanDelete, vrm, rc, ReMatIds, loopInfo,
SpillMBBs, SpillIdxes, RestoreMBBs, RestoreIdxes,
MBBVRegsMap, NewLIs);
}
// Insert spills / restores if we are splitting.
if (!TrySplit) {
handleSpilledImpDefs(li, vrm, rc, NewLIs);
return NewLIs;
}
SmallPtrSet<LiveInterval*, 4> AddedKill;
SmallVector<unsigned, 2> Ops;
if (NeedStackSlot) {
int Id = SpillMBBs.find_first();
while (Id != -1) {
std::vector<SRInfo> &spills = SpillIdxes[Id];
for (unsigned i = 0, e = spills.size(); i != e; ++i) {
int index = spills[i].index;
unsigned VReg = spills[i].vreg;
LiveInterval &nI = getOrCreateInterval(VReg);
bool isReMat = vrm.isReMaterialized(VReg);
MachineInstr *MI = getInstructionFromIndex(index);
bool CanFold = false;
bool FoundUse = false;
Ops.clear();
if (spills[i].canFold) {
CanFold = true;
for (unsigned j = 0, ee = MI->getNumOperands(); j != ee; ++j) {
MachineOperand &MO = MI->getOperand(j);
if (!MO.isReg() || MO.getReg() != VReg)
continue;
Ops.push_back(j);
if (MO.isDef())
continue;
if (isReMat ||
(!FoundUse && !alsoFoldARestore(Id, index, VReg,
RestoreMBBs, RestoreIdxes))) {
// MI has two-address uses of the same register. If the use
// isn't the first and only use in the BB, then we can't fold
// it. FIXME: Move this to rewriteInstructionsForSpills.
CanFold = false;
break;
}
FoundUse = true;
}
}
// Fold the store into the def if possible.
bool Folded = false;
if (CanFold && !Ops.empty()) {
if (tryFoldMemoryOperand(MI, vrm, NULL, index, Ops, true, Slot,VReg)){
Folded = true;
if (FoundUse) {
// Also folded uses, do not issue a load.
eraseRestoreInfo(Id, index, VReg, RestoreMBBs, RestoreIdxes);
nI.removeRange(getLoadIndex(index), getUseIndex(index)+1);
}
nI.removeRange(getDefIndex(index), getStoreIndex(index));
}
}
// Otherwise tell the spiller to issue a spill.
if (!Folded) {
LiveRange *LR = &nI.ranges[nI.ranges.size()-1];
bool isKill = LR->end == getStoreIndex(index);
if (!MI->registerDefIsDead(nI.reg))
// No need to spill a dead def.
vrm.addSpillPoint(VReg, isKill, MI);
if (isKill)
AddedKill.insert(&nI);
}
}
Id = SpillMBBs.find_next(Id);
}
}
int Id = RestoreMBBs.find_first();
while (Id != -1) {
std::vector<SRInfo> &restores = RestoreIdxes[Id];
for (unsigned i = 0, e = restores.size(); i != e; ++i) {
int index = restores[i].index;
if (index == -1)
continue;
unsigned VReg = restores[i].vreg;
LiveInterval &nI = getOrCreateInterval(VReg);
bool isReMat = vrm.isReMaterialized(VReg);
MachineInstr *MI = getInstructionFromIndex(index);
bool CanFold = false;
Ops.clear();
if (restores[i].canFold) {
CanFold = true;
for (unsigned j = 0, ee = MI->getNumOperands(); j != ee; ++j) {
MachineOperand &MO = MI->getOperand(j);
if (!MO.isReg() || MO.getReg() != VReg)
continue;
if (MO.isDef()) {
// If this restore were to be folded, it would have been folded
// already.
CanFold = false;
break;
}
Ops.push_back(j);
}
}
// Fold the load into the use if possible.
bool Folded = false;
if (CanFold && !Ops.empty()) {
if (!isReMat)
Folded = tryFoldMemoryOperand(MI, vrm, NULL,index,Ops,true,Slot,VReg);
else {
MachineInstr *ReMatDefMI = vrm.getReMaterializedMI(VReg);
int LdSlot = 0;
bool isLoadSS = tii_->isLoadFromStackSlot(ReMatDefMI, LdSlot);
// If the rematerializable def is a load, also try to fold it.
if (isLoadSS || ReMatDefMI->getDesc().canFoldAsLoad())
Folded = tryFoldMemoryOperand(MI, vrm, ReMatDefMI, index,
Ops, isLoadSS, LdSlot, VReg);
if (!Folded) {
unsigned ImpUse = getReMatImplicitUse(li, ReMatDefMI);
if (ImpUse) {
// Re-matting an instruction with virtual register use. Add the
// register as an implicit use on the use MI and update the register
// interval's spill weight to HUGE_VALF to prevent it from being
// spilled.
LiveInterval &ImpLi = getInterval(ImpUse);
ImpLi.weight = HUGE_VALF;
MI->addOperand(MachineOperand::CreateReg(ImpUse, false, true));
}
}
}
}
// If folding is not possible / failed, then tell the spiller to issue a
// load / rematerialization for us.
if (Folded)
nI.removeRange(getLoadIndex(index), getUseIndex(index)+1);
else
vrm.addRestorePoint(VReg, MI);
}
Id = RestoreMBBs.find_next(Id);
}
// Finalize intervals: add kills, finalize spill weights, and filter out
// dead intervals.
std::vector<LiveInterval*> RetNewLIs;
for (unsigned i = 0, e = NewLIs.size(); i != e; ++i) {
LiveInterval *LI = NewLIs[i];
if (!LI->empty()) {
LI->weight /= InstrSlots::NUM * getApproximateInstructionCount(*LI);
if (!AddedKill.count(LI)) {
LiveRange *LR = &LI->ranges[LI->ranges.size()-1];
unsigned LastUseIdx = getBaseIndex(LR->end);
MachineInstr *LastUse = getInstructionFromIndex(LastUseIdx);
int UseIdx = LastUse->findRegisterUseOperandIdx(LI->reg, false);
assert(UseIdx != -1);
if (!LastUse->isRegTiedToDefOperand(UseIdx)) {
LastUse->getOperand(UseIdx).setIsKill();
vrm.addKillPoint(LI->reg, LastUseIdx);
}
}
RetNewLIs.push_back(LI);
}
}
handleSpilledImpDefs(li, vrm, rc, RetNewLIs);
return RetNewLIs;
}
/// hasAllocatableSuperReg - Return true if the specified physical register has
/// any super register that's allocatable.
bool LiveIntervals::hasAllocatableSuperReg(unsigned Reg) const {
for (const unsigned* AS = tri_->getSuperRegisters(Reg); *AS; ++AS)
if (allocatableRegs_[*AS] && hasInterval(*AS))
return true;
return false;
}
/// getRepresentativeReg - Find the largest super register of the specified
/// physical register.
unsigned LiveIntervals::getRepresentativeReg(unsigned Reg) const {
// Find the largest super-register that is allocatable.
unsigned BestReg = Reg;
for (const unsigned* AS = tri_->getSuperRegisters(Reg); *AS; ++AS) {
unsigned SuperReg = *AS;
if (!hasAllocatableSuperReg(SuperReg) && hasInterval(SuperReg)) {
BestReg = SuperReg;
break;
}
}
return BestReg;
}
/// getNumConflictsWithPhysReg - Return the number of uses and defs of the
/// specified interval that conflicts with the specified physical register.
unsigned LiveIntervals::getNumConflictsWithPhysReg(const LiveInterval &li,
unsigned PhysReg) const {
unsigned NumConflicts = 0;
const LiveInterval &pli = getInterval(getRepresentativeReg(PhysReg));
for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(li.reg),
E = mri_->reg_end(); I != E; ++I) {
MachineOperand &O = I.getOperand();
MachineInstr *MI = O.getParent();
unsigned Index = getInstructionIndex(MI);
if (pli.liveAt(Index))
++NumConflicts;
}
return NumConflicts;
}
/// spillPhysRegAroundRegDefsUses - Spill the specified physical register
/// around all defs and uses of the specified interval. Return true if it
/// was able to cut its interval.
bool LiveIntervals::spillPhysRegAroundRegDefsUses(const LiveInterval &li,
unsigned PhysReg, VirtRegMap &vrm) {
unsigned SpillReg = getRepresentativeReg(PhysReg);
for (const unsigned *AS = tri_->getAliasSet(PhysReg); *AS; ++AS)
// If there are registers which alias PhysReg, but which are not a
// sub-register of the chosen representative super register. Assert
// since we can't handle it yet.
assert(*AS == SpillReg || !allocatableRegs_[*AS] || !hasInterval(*AS) ||
tri_->isSuperRegister(*AS, SpillReg));
bool Cut = false;
LiveInterval &pli = getInterval(SpillReg);
SmallPtrSet<MachineInstr*, 8> SeenMIs;
for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(li.reg),
E = mri_->reg_end(); I != E; ++I) {
MachineOperand &O = I.getOperand();
MachineInstr *MI = O.getParent();
if (SeenMIs.count(MI))
continue;
SeenMIs.insert(MI);
unsigned Index = getInstructionIndex(MI);
if (pli.liveAt(Index)) {
vrm.addEmergencySpill(SpillReg, MI);
unsigned StartIdx = getLoadIndex(Index);
unsigned EndIdx = getStoreIndex(Index)+1;
if (pli.isInOneLiveRange(StartIdx, EndIdx)) {
pli.removeRange(StartIdx, EndIdx);
Cut = true;
} else {
cerr << "Ran out of registers during register allocation!\n";
if (MI->getOpcode() == TargetInstrInfo::INLINEASM) {
cerr << "Please check your inline asm statement for invalid "
<< "constraints:\n";
MI->print(cerr.stream(), tm_);
}
exit(1);
}
for (const unsigned* AS = tri_->getSubRegisters(SpillReg); *AS; ++AS) {
if (!hasInterval(*AS))
continue;
LiveInterval &spli = getInterval(*AS);
if (spli.liveAt(Index))
spli.removeRange(getLoadIndex(Index), getStoreIndex(Index)+1);
}
}
}
return Cut;
}
LiveRange LiveIntervals::addLiveRangeToEndOfBlock(unsigned reg,
MachineInstr* startInst) {
LiveInterval& Interval = getOrCreateInterval(reg);
VNInfo* VN = Interval.getNextValue(
getInstructionIndex(startInst) + InstrSlots::DEF,
startInst, getVNInfoAllocator());
VN->hasPHIKill = true;
VN->kills.push_back(getMBBEndIdx(startInst->getParent()));
LiveRange LR(getInstructionIndex(startInst) + InstrSlots::DEF,
getMBBEndIdx(startInst->getParent()) + 1, VN);
Interval.addRange(LR);
return LR;
}
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