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llvm-6502/lib/CodeGen/LiveIntervalAnalysis.cpp
Evan Cheng 8480293f41 Only remat loads from immutable stack slots. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45831 91177308-0d34-0410-b5e6-96231b3b80d8
2008-01-10 08:24:38 +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/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/Target/MRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.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;
namespace {
// Hidden options for help debugging.
cl::opt<bool> DisableReMat("disable-rematerialization",
cl::init(false), cl::Hidden);
cl::opt<bool> SplitAtBB("split-intervals-at-bb",
cl::init(true), cl::Hidden);
cl::opt<int> SplitLimit("split-limit",
cl::init(-1), cl::Hidden);
}
STATISTIC(numIntervals, "Number of original intervals");
STATISTIC(numIntervalsAfter, "Number of intervals after coalescing");
STATISTIC(numFolds , "Number of loads/stores folded into instructions");
STATISTIC(numSplits , "Number of intervals split");
char LiveIntervals::ID = 0;
namespace {
RegisterPass<LiveIntervals> X("liveintervals", "Live Interval Analysis");
}
void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addPreserved<LiveVariables>();
AU.addRequired<LiveVariables>();
AU.addPreservedID(MachineLoopInfoID);
AU.addPreservedID(MachineDominatorsID);
AU.addPreservedID(PHIEliminationID);
AU.addRequiredID(PHIEliminationID);
AU.addRequiredID(TwoAddressInstructionPassID);
MachineFunctionPass::getAnalysisUsage(AU);
}
void LiveIntervals::releaseMemory() {
Idx2MBBMap.clear();
mi2iMap_.clear();
i2miMap_.clear();
r2iMap_.clear();
// Release VNInfo memroy regions after all VNInfo objects are dtor'd.
VNInfoAllocator.Reset();
for (unsigned i = 0, e = ClonedMIs.size(); i != e; ++i)
delete ClonedMIs[i];
}
namespace llvm {
inline bool operator<(unsigned V, const IdxMBBPair &IM) {
return V < IM.first;
}
inline bool operator<(const IdxMBBPair &IM, unsigned V) {
return IM.first < V;
}
struct Idx2MBBCompare {
bool operator()(const IdxMBBPair &LHS, const IdxMBBPair &RHS) const {
return LHS.first < RHS.first;
}
};
}
/// runOnMachineFunction - Register allocate the whole function
///
bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
mf_ = &fn;
tm_ = &fn.getTarget();
mri_ = tm_->getRegisterInfo();
tii_ = tm_->getInstrInfo();
lv_ = &getAnalysis<LiveVariables>();
allocatableRegs_ = mri_->getAllocatableSet(fn);
// 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;
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");
i2miMap_.push_back(I);
MIIndex += InstrSlots::NUM;
}
// 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());
computeIntervals();
numIntervals += getNumIntervals();
DOUT << "********** INTERVALS **********\n";
for (iterator I = begin(), E = end(); I != E; ++I) {
I->second.print(DOUT, mri_);
DOUT << "\n";
}
numIntervalsAfter += 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(DOUT, mri_);
DOUT << "\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;
if (tii_->isMoveInstr(*MI, SrcReg, DstReg))
if (SrcReg == li.reg || DstReg == li.reg)
continue;
for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
MachineOperand& mop = MI->getOperand(i);
if (!mop.isRegister())
continue;
unsigned PhysReg = mop.getReg();
if (PhysReg == 0 || PhysReg == li.reg)
continue;
if (MRegisterInfo::isVirtualRegister(PhysReg)) {
if (!vrm.hasPhys(PhysReg))
continue;
PhysReg = vrm.getPhys(PhysReg);
}
if (PhysReg && mri_->regsOverlap(PhysReg, reg))
return true;
}
}
}
return false;
}
void LiveIntervals::printRegName(unsigned reg) const {
if (MRegisterInfo::isPhysicalRegister(reg))
cerr << mri_->getName(reg);
else
cerr << "%reg" << reg;
}
void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
MachineBasicBlock::iterator mi,
unsigned MIIdx,
LiveInterval &interval) {
DOUT << "\t\tregister: "; DEBUG(printRegName(interval.reg));
LiveVariables::VarInfo& vi = lv_->getVarInfo(interval.reg);
// 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);
VNInfo *ValNo;
unsigned SrcReg, DstReg;
if (tii_->isMoveInstr(*mi, SrcReg, DstReg))
ValNo = interval.getNextValue(defIndex, SrcReg, VNInfoAllocator);
else if (mi->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG)
ValNo = interval.getNextValue(defIndex, mi->getOperand(1).getReg(),
VNInfoAllocator);
else
ValNo = interval.getNextValue(defIndex, 0, 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,
getInstructionIndex(&mbb->back()) + InstrSlots::NUM,
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 (unsigned i = 0, e = vi.AliveBlocks.size(); i != e; ++i) {
if (vi.AliveBlocks[i]) {
MachineBasicBlock *MBB = mf_->getBlockNumbered(i);
if (!MBB->empty()) {
LiveRange LR(getMBBStartIdx(i),
getInstructionIndex(&MBB->back()) + InstrSlots::NUM,
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->isRegReDefinedByTwoAddr(interval.reg)) {
// 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);
const LiveRange *OldLR = interval.getLiveRangeContaining(RedefIndex-1);
VNInfo *OldValNo = OldLR->valno;
unsigned OldEnd = OldLR->end;
// 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(0, 0, VNInfoAllocator);
interval.copyValNumInfo(ValNo, OldValNo);
// Value#0 is now defined by the 2-addr instruction.
OldValNo->def = RedefIndex;
OldValNo->reg = 0;
// 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);
interval.removeKills(ValNo, RedefIndex, OldEnd);
// If this redefinition is dead, we need to add a dummy unit live
// range covering the def slot.
if (lv_->RegisterDefIsDead(mi, interval.reg))
interval.addRange(LiveRange(RedefIndex, RedefIndex+1, OldValNo));
DOUT << " RESULT: ";
interval.print(DOUT, mri_);
} 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, mri_); DOUT << "\n";
interval.removeRange(Start, End);
interval.addKill(VNI, Start);
VNI->hasPHIKill = true;
DOUT << " RESULT: "; interval.print(DOUT, mri_);
// 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, mri_);
}
// 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);
VNInfo *ValNo;
unsigned SrcReg, DstReg;
if (tii_->isMoveInstr(*mi, SrcReg, DstReg))
ValNo = interval.getNextValue(defIndex, SrcReg, VNInfoAllocator);
else if (mi->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG)
ValNo = interval.getNextValue(defIndex, mi->getOperand(1).getReg(),
VNInfoAllocator);
else
ValNo = interval.getNextValue(defIndex, 0, VNInfoAllocator);
unsigned killIndex = getInstructionIndex(&mbb->back()) + InstrSlots::NUM;
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,
LiveInterval &interval,
unsigned SrcReg) {
// 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);
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 (lv_->RegisterDefIsDead(mi, interval.reg)) {
DOUT << " dead";
end = getDefIndex(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)
while (++mi != MBB->end()) {
baseIndex += InstrSlots::NUM;
if (lv_->KillsRegister(mi, interval.reg)) {
DOUT << " killed";
end = getUseIndex(baseIndex) + 1;
goto exit;
} else if (lv_->ModifiesRegister(mi, interval.reg)) {
// 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;
goto exit;
}
}
// 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.
assert(!SrcReg && "physreg was not killed in defining block!");
end = getDefIndex(start) + 1; // It's dead.
exit:
assert(start < end && "did not find end of interval?");
// Already exists? Extend old live interval.
LiveInterval::iterator OldLR = interval.FindLiveRangeContaining(start);
VNInfo *ValNo = (OldLR != interval.end())
? OldLR->valno : interval.getNextValue(start, SrcReg, VNInfoAllocator);
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,
unsigned reg) {
if (MRegisterInfo::isVirtualRegister(reg))
handleVirtualRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(reg));
else if (allocatableRegs_[reg]) {
unsigned SrcReg, DstReg;
if (MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG)
SrcReg = MI->getOperand(1).getReg();
else if (!tii_->isMoveInstr(*MI, SrcReg, DstReg))
SrcReg = 0;
handlePhysicalRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(reg), SrcReg);
// Def of a register also defines its sub-registers.
for (const unsigned* AS = mri_->getSubRegisters(reg); *AS; ++AS)
// Avoid processing some defs more than once.
if (!MI->findRegisterDefOperand(*AS))
handlePhysicalRegisterDef(MBB, MI, MIIdx, 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;
unsigned end = start;
while (mi != MBB->end()) {
if (lv_->KillsRegister(mi, interval.reg)) {
DOUT << " killed";
end = getUseIndex(baseIndex) + 1;
goto exit;
} else if (lv_->ModifiesRegister(mi, interval.reg)) {
// 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;
goto exit;
}
baseIndex += InstrSlots::NUM;
++mi;
}
exit:
// Live-in register might not be used at all.
if (end == MIIdx) {
if (isAlias) {
DOUT << " dead";
end = getDefIndex(MIIdx) + 1;
} else {
DOUT << " live through";
end = baseIndex;
}
}
LiveRange LR(start, end, interval.getNextValue(start, 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';
// Track the index of the current machine instr.
unsigned MIIndex = 0;
for (MachineFunction::iterator MBBI = mf_->begin(), E = mf_->end();
MBBI != E; ++MBBI) {
MachineBasicBlock *MBB = MBBI;
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 = mri_->getSubRegisters(*LI); *AS; ++AS)
if (!hasInterval(*AS))
handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*AS),
true);
}
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.isRegister() && MO.getReg() && MO.isDef())
handleRegisterDef(MBB, MI, MIIndex, MO.getReg());
}
MIIndex += InstrSlots::NUM;
}
}
}
bool LiveIntervals::findLiveInMBBs(const LiveRange &LR,
SmallVectorImpl<MachineBasicBlock*> &MBBs) const {
std::vector<IdxMBBPair>::const_iterator I =
std::lower_bound(Idx2MBBMap.begin(), Idx2MBBMap.end(), LR.start);
bool ResVal = false;
while (I != Idx2MBBMap.end()) {
if (LR.end <= I->first)
break;
MBBs.push_back(I->second);
ResVal = true;
++I;
}
return ResVal;
}
LiveInterval LiveIntervals::createInterval(unsigned reg) {
float Weight = MRegisterInfo::isPhysicalRegister(reg) ?
HUGE_VALF : 0.0F;
return LiveInterval(reg, Weight);
}
//===----------------------------------------------------------------------===//
// Register allocator hooks.
//
/// 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,
bool &isLoad) {
if (DisableReMat)
return false;
isLoad = false;
const TargetInstrDesc &TID = MI->getDesc();
if (TID.isImplicitDef() || tii_->isTriviallyReMaterializable(MI)) {
isLoad = TID.isSimpleLoad();
return true;
}
int FrameIdx = 0;
if (!tii_->isLoadFromStackSlot(MI, FrameIdx) ||
!mf_->getFrameInfo()->isImmutableObjectIndex(FrameIdx))
return false;
// This is a load from fixed stack slot. It can be rematerialized unless it's
// re-defined by a two-address instruction.
isLoad = true;
for (LiveInterval::const_vni_iterator i = li.vni_begin(), e = li.vni_end();
i != e; ++i) {
const VNInfo *VNI = *i;
if (VNI == ValNo)
continue;
unsigned DefIdx = VNI->def;
if (DefIdx == ~1U)
continue; // Dead val#.
MachineInstr *DefMI = (DefIdx == ~0u)
? NULL : getInstructionFromIndex(DefIdx);
if (DefMI && DefMI->isRegReDefinedByTwoAddr(li.reg)) {
isLoad = false;
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, 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, DefIsLoad))
return false;
isLoad |= DefIsLoad;
}
return true;
}
/// 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) {
unsigned MRInfo = 0;
const TargetInstrDesc &TID = MI->getDesc();
// If it is an implicit def instruction, just delete it.
if (TID.isImplicitDef()) {
RemoveMachineInstrFromMaps(MI);
vrm.RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
++numFolds;
return true;
}
SmallVector<unsigned, 2> FoldOps;
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
unsigned OpIdx = Ops[i];
// FIXME: fold subreg use.
if (MI->getOperand(OpIdx).getSubReg())
return false;
if (MI->getOperand(OpIdx).isDef())
MRInfo |= (unsigned)VirtRegMap::isMod;
else {
// Filter out two-address use operand(s).
if (TID.getOperandConstraint(OpIdx, TOI::TIED_TO) != -1) {
MRInfo = VirtRegMap::isModRef;
continue;
}
MRInfo |= (unsigned)VirtRegMap::isRef;
}
FoldOps.push_back(OpIdx);
}
MachineInstr *fmi = isSS ? tii_->foldMemoryOperand(MI, FoldOps, Slot)
: tii_->foldMemoryOperand(MI, FoldOps, DefMI);
if (fmi) {
// Attempt to fold the memory reference into the instruction. If
// we can do this, we don't need to insert spill code.
if (lv_)
lv_->instructionChanged(MI, fmi);
else
LiveVariables::transferKillDeadInfo(MI, fmi, mri_);
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);
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) const {
SmallVector<unsigned, 2> FoldOps;
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
unsigned OpIdx = Ops[i];
// FIXME: fold subreg use.
if (MI->getOperand(OpIdx).getSubReg())
return false;
FoldOps.push_back(OpIdx);
}
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;
}
/// rewriteInstructionForSpills, rewriteInstructionsForSpills - Helper functions
/// for addIntervalsForSpills to rewrite uses / defs for the given live range.
bool LiveIntervals::
rewriteInstructionForSpills(const LiveInterval &li, bool TrySplit,
unsigned id, unsigned index, unsigned end, MachineInstr *MI,
MachineInstr *ReMatOrigDefMI, MachineInstr *ReMatDefMI,
unsigned Slot, int LdSlot,
bool isLoad, bool isLoadSS, bool DefIsReMat, bool CanDelete,
VirtRegMap &vrm, MachineRegisterInfo &RegInfo,
const TargetRegisterClass* rc,
SmallVector<int, 4> &ReMatIds,
unsigned &NewVReg, bool &HasDef, bool &HasUse,
const MachineLoopInfo *loopInfo,
std::map<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.isRegister())
continue;
unsigned Reg = mop.getReg();
unsigned RegI = Reg;
if (Reg == 0 || MRegisterInfo::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.isRegister())
continue;
unsigned RegJ = MOj.getReg();
if (RegJ == 0 || MRegisterInfo::isPhysicalRegister(RegJ))
continue;
if (RegJ == RegI) {
Ops.push_back(j);
HasUse |= MOj.isUse();
HasDef |= MOj.isDef();
}
}
if (TryFold) {
// 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, Reg)) {
// Folding the load/store can completely change the instruction in
// unpredictable ways, rescan it from the beginning.
HasUse = false;
HasDef = false;
CanFold = false;
goto RestartInstruction;
}
} else {
CanFold = canFoldMemoryOperand(MI, Ops);
}
} else
CanFold = false;
// Create a new virtual register for the spill interval.
bool CreatedNewVReg = false;
if (NewVReg == 0) {
NewVReg = RegInfo.createVirtualRegister(rc);
vrm.grow();
CreatedNewVReg = true;
}
mop.setReg(NewVReg);
// Reuse NewVReg for other reads.
for (unsigned j = 0, e = Ops.size(); j != e; ++j)
MI->getOperand(Ops[j]).setReg(NewVReg);
if (CreatedNewVReg) {
if (DefIsReMat) {
vrm.setVirtIsReMaterialized(NewVReg, ReMatDefMI/*, CanDelete*/);
if (ReMatIds[id] == VirtRegMap::MAX_STACK_SLOT) {
// Each valnum may have its own remat id.
ReMatIds[id] = vrm.assignVirtReMatId(NewVReg);
} else {
vrm.assignVirtReMatId(NewVReg, ReMatIds[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);
}
// 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, mri_);
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;
}
static const VNInfo *findDefinedVNInfo(const LiveInterval &li, unsigned DefIdx) {
const VNInfo *VNI = NULL;
for (LiveInterval::const_vni_iterator i = li.vni_begin(),
e = li.vni_end(); i != e; ++i)
if ((*i)->def == DefIdx) {
VNI = *i;
break;
}
return VNI;
}
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, MachineRegisterInfo &RegInfo,
const TargetRegisterClass* rc,
SmallVector<int, 4> &ReMatIds,
const MachineLoopInfo *loopInfo,
BitVector &SpillMBBs,
std::map<unsigned, std::vector<SRInfo> > &SpillIdxes,
BitVector &RestoreMBBs,
std::map<unsigned, std::vector<SRInfo> > &RestoreIdxes,
std::map<unsigned,unsigned> &MBBVRegsMap,
std::vector<LiveInterval*> &NewLIs) {
bool AllCanFold = true;
unsigned NewVReg = 0;
unsigned index = getBaseIndex(I->start);
unsigned end = getBaseIndex(I->end-1) + InstrSlots::NUM;
for (; index != end; index += InstrSlots::NUM) {
// skip deleted instructions
while (index != end && !getInstructionFromIndex(index))
index += InstrSlots::NUM;
if (index == end) break;
MachineInstr *MI = getInstructionFromIndex(index);
MachineBasicBlock *MBB = MI->getParent();
unsigned ThisVReg = 0;
if (TrySplit) {
std::map<unsigned,unsigned>::const_iterator NVI =
MBBVRegsMap.find(MBB->getNumber());
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.
// FIXME: Too slow? Can we fix it after rewriteInstructionsForSpills?
bool MIHasUse = false;
bool MIHasDef = false;
for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
MachineOperand& mop = MI->getOperand(i);
if (!mop.isRegister() || mop.getReg() != li.reg)
continue;
if (mop.isUse())
MIHasUse = true;
else
MIHasDef = true;
}
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, TrySplit, I->valno->id,
index, end, MI, ReMatOrigDefMI, ReMatDefMI,
Slot, LdSlot, isLoad, isLoadSS, DefIsReMat,
CanDelete, vrm, RegInfo, rc, ReMatIds, NewVReg,
HasDef, HasUse, loopInfo, 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.
unsigned MBBId = MBB->getNumber();
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 = findDefinedVNInfo(li, getDefIndex(index));
if (VNI)
HasKill = anyKillInMBBAfterIdx(li, VNI, MBB, getDefIndex(index));
}
std::map<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) {
std::map<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;
std::map<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,
std::map<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,
std::map<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;
}
std::vector<LiveInterval*> LiveIntervals::
addIntervalsForSpills(const LiveInterval &li,
const MachineLoopInfo *loopInfo, VirtRegMap &vrm) {
// Since this is called after the analysis is done we don't know if
// LiveVariables is available
lv_ = getAnalysisToUpdate<LiveVariables>();
assert(li.weight != HUGE_VALF &&
"attempt to spill already spilled interval!");
DOUT << "\t\t\t\tadding intervals for spills for interval: ";
li.print(DOUT, mri_);
DOUT << '\n';
// Each bit specify whether it a spill is required in the MBB.
BitVector SpillMBBs(mf_->getNumBlockIDs());
std::map<unsigned, std::vector<SRInfo> > SpillIdxes;
BitVector RestoreMBBs(mf_->getNumBlockIDs());
std::map<unsigned, std::vector<SRInfo> > RestoreIdxes;
std::map<unsigned,unsigned> MBBVRegsMap;
std::vector<LiveInterval*> NewLIs;
MachineRegisterInfo &RegInfo = mf_->getRegInfo();
const TargetRegisterClass* rc = RegInfo.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().isSimpleLoad()));
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, RegInfo, rc, ReMatIds, loopInfo,
SpillMBBs, SpillIdxes, RestoreMBBs, RestoreIdxes,
MBBVRegsMap, NewLIs);
} else {
rewriteInstructionsForSpills(li, false, I, NULL, 0,
Slot, 0, false, false, false,
false, vrm, RegInfo, rc, ReMatIds, loopInfo,
SpillMBBs, SpillIdxes, RestoreMBBs, RestoreIdxes,
MBBVRegsMap, NewLIs);
}
IsFirstRange = false;
}
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, 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. vrm must
// delete these!
ReMatDefs[VN] = ReMatDefMI = ReMatDefMI->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)
Slot = vrm.assignVirt2StackSlot(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().isSimpleLoad());
rewriteInstructionsForSpills(li, TrySplit, I, ReMatOrigDefMI, ReMatDefMI,
Slot, LdSlot, isLoad, isLoadSS, DefIsReMat,
CanDelete, vrm, RegInfo, rc, ReMatIds, loopInfo,
SpillMBBs, SpillIdxes, RestoreMBBs, RestoreIdxes,
MBBVRegsMap, NewLIs);
}
// Insert spills / restores if we are splitting.
if (!TrySplit)
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.isRegister() || 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 > 0) {
// 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));
}
}
// Else tell the spiller to issue a spill.
if (!Folded) {
LiveRange *LR = &nI.ranges[nI.ranges.size()-1];
bool isKill = LR->end == getStoreIndex(index);
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);
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.isRegister() || 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 (!vrm.isReMaterialized(VReg))
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().isSimpleLoad())
Folded = tryFoldMemoryOperand(MI, vrm, ReMatDefMI, index,
Ops, isLoadSS, LdSlot, VReg);
}
}
// 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 /= LI->getSize();
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);
assert(UseIdx != -1);
if (LastUse->getDesc().getOperandConstraint(UseIdx, TOI::TIED_TO) ==
-1) {
LastUse->getOperand(UseIdx).setIsKill();
vrm.addKillPoint(LI->reg, LastUseIdx);
}
}
RetNewLIs.push_back(LI);
}
}
return RetNewLIs;
}
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