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llvm-mirror/lib/CodeGen/LiveIntervalAnalysis.cpp
Jakob Stoklund Olesen ffe1dbc840 When a physreg is live-in and live through a basic block, make sure its live 
range covers the entire block.

The live range can't be terminated at a random instruction.

llvm-svn: 130619
2011-04-30 19:12:33 +00:00

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79 KiB
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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/CalcSpillWeights.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/ProcessImplicitDefs.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/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include <algorithm>
#include <limits>
#include <cmath>
using namespace llvm;
// Hidden options for help debugging.
static cl::opt<bool> DisableReMat("disable-rematerialization",
cl::init(false), cl::Hidden);
STATISTIC(numIntervals , "Number of original intervals");
STATISTIC(numFolds , "Number of loads/stores folded into instructions");
STATISTIC(numSplits , "Number of intervals split");
char LiveIntervals::ID = 0;
INITIALIZE_PASS_BEGIN(LiveIntervals, "liveintervals",
"Live Interval Analysis", false, false)
INITIALIZE_PASS_DEPENDENCY(LiveVariables)
INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
INITIALIZE_PASS_DEPENDENCY(PHIElimination)
INITIALIZE_PASS_DEPENDENCY(TwoAddressInstructionPass)
INITIALIZE_PASS_DEPENDENCY(ProcessImplicitDefs)
INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_END(LiveIntervals, "liveintervals",
"Live Interval Analysis", false, false)
void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addRequired<AliasAnalysis>();
AU.addPreserved<AliasAnalysis>();
AU.addRequired<LiveVariables>();
AU.addPreserved<LiveVariables>();
AU.addRequired<MachineLoopInfo>();
AU.addPreserved<MachineLoopInfo>();
AU.addPreservedID(MachineDominatorsID);
if (!StrongPHIElim) {
AU.addPreservedID(PHIEliminationID);
AU.addRequiredID(PHIEliminationID);
}
AU.addRequiredID(TwoAddressInstructionPassID);
AU.addPreserved<ProcessImplicitDefs>();
AU.addRequired<ProcessImplicitDefs>();
AU.addPreserved<SlotIndexes>();
AU.addRequiredTransitive<SlotIndexes>();
MachineFunctionPass::getAnalysisUsage(AU);
}
void LiveIntervals::releaseMemory() {
// Free the live intervals themselves.
for (DenseMap<unsigned, LiveInterval*>::iterator I = r2iMap_.begin(),
E = r2iMap_.end(); I != E; ++I)
delete I->second;
r2iMap_.clear();
// Release VNInfo memory regions, VNInfo objects don't need to be dtor'd.
VNInfoAllocator.Reset();
while (!CloneMIs.empty()) {
MachineInstr *MI = CloneMIs.back();
CloneMIs.pop_back();
mf_->DeleteMachineInstr(MI);
}
}
/// runOnMachineFunction - Register allocate the whole function
///
bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
mf_ = &fn;
mri_ = &mf_->getRegInfo();
tm_ = &fn.getTarget();
tri_ = tm_->getRegisterInfo();
tii_ = tm_->getInstrInfo();
aa_ = &getAnalysis<AliasAnalysis>();
lv_ = &getAnalysis<LiveVariables>();
indexes_ = &getAnalysis<SlotIndexes>();
allocatableRegs_ = tri_->getAllocatableSet(fn);
computeIntervals();
numIntervals += getNumIntervals();
DEBUG(dump());
return true;
}
/// print - Implement the dump method.
void LiveIntervals::print(raw_ostream &OS, const Module* ) const {
OS << "********** INTERVALS **********\n";
for (const_iterator I = begin(), E = end(); I != E; ++I) {
I->second->print(OS, tri_);
OS << "\n";
}
printInstrs(OS);
}
void LiveIntervals::printInstrs(raw_ostream &OS) const {
OS << "********** MACHINEINSTRS **********\n";
mf_->print(OS, indexes_);
}
void LiveIntervals::dumpInstrs() const {
printInstrs(dbgs());
}
bool LiveIntervals::conflictsWithPhysReg(const LiveInterval &li,
VirtRegMap &vrm, unsigned reg) {
// We don't handle fancy stuff crossing basic block boundaries
if (li.ranges.size() != 1)
return true;
const LiveRange &range = li.ranges.front();
SlotIndex idx = range.start.getBaseIndex();
SlotIndex end = range.end.getPrevSlot().getBaseIndex().getNextIndex();
// Skip deleted instructions
MachineInstr *firstMI = getInstructionFromIndex(idx);
while (!firstMI && idx != end) {
idx = idx.getNextIndex();
firstMI = getInstructionFromIndex(idx);
}
if (!firstMI)
return false;
// Find last instruction in range
SlotIndex lastIdx = end.getPrevIndex();
MachineInstr *lastMI = getInstructionFromIndex(lastIdx);
while (!lastMI && lastIdx != idx) {
lastIdx = lastIdx.getPrevIndex();
lastMI = getInstructionFromIndex(lastIdx);
}
if (!lastMI)
return false;
// Range cannot cross basic block boundaries or terminators
MachineBasicBlock *MBB = firstMI->getParent();
if (MBB != lastMI->getParent() || lastMI->getDesc().isTerminator())
return true;
MachineBasicBlock::const_iterator E = lastMI;
++E;
for (MachineBasicBlock::const_iterator I = firstMI; I != E; ++I) {
const MachineInstr &MI = *I;
// Allow copies to and from li.reg
if (MI.isCopy())
if (MI.getOperand(0).getReg() == li.reg ||
MI.getOperand(1).getReg() == li.reg)
continue;
// Check for operands using reg
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
const 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;
}
}
// No conflicts found.
return false;
}
bool LiveIntervals::conflictsWithAliasRef(LiveInterval &li, unsigned Reg,
SmallPtrSet<MachineInstr*,32> &JoinedCopies) {
for (LiveInterval::Ranges::const_iterator
I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) {
for (SlotIndex index = I->start.getBaseIndex(),
end = I->end.getPrevSlot().getBaseIndex().getNextIndex();
index != end;
index = index.getNextIndex()) {
MachineInstr *MI = getInstructionFromIndex(index);
if (!MI)
continue; // skip deleted instructions
if (JoinedCopies.count(MI))
continue;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand& MO = MI->getOperand(i);
if (!MO.isReg())
continue;
unsigned PhysReg = MO.getReg();
if (PhysReg == 0 || PhysReg == Reg ||
TargetRegisterInfo::isVirtualRegister(PhysReg))
continue;
if (tri_->regsOverlap(Reg, PhysReg))
return true;
}
}
}
return false;
}
static
bool MultipleDefsBySameMI(const MachineInstr &MI, unsigned MOIdx) {
unsigned Reg = MI.getOperand(MOIdx).getReg();
for (unsigned i = MOIdx+1, e = MI.getNumOperands(); i < e; ++i) {
const MachineOperand &MO = MI.getOperand(i);
if (!MO.isReg())
continue;
if (MO.getReg() == Reg && MO.isDef()) {
assert(MI.getOperand(MOIdx).getSubReg() != MO.getSubReg() &&
MI.getOperand(MOIdx).getSubReg() &&
(MO.getSubReg() || MO.isImplicit()));
return true;
}
}
return false;
}
/// isPartialRedef - Return true if the specified def at the specific index is
/// partially re-defining the specified live interval. A common case of this is
/// a definition of the sub-register.
bool LiveIntervals::isPartialRedef(SlotIndex MIIdx, MachineOperand &MO,
LiveInterval &interval) {
if (!MO.getSubReg() || MO.isEarlyClobber())
return false;
SlotIndex RedefIndex = MIIdx.getDefIndex();
const LiveRange *OldLR =
interval.getLiveRangeContaining(RedefIndex.getUseIndex());
MachineInstr *DefMI = getInstructionFromIndex(OldLR->valno->def);
if (DefMI != 0) {
return DefMI->findRegisterDefOperandIdx(interval.reg) != -1;
}
return false;
}
void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
MachineBasicBlock::iterator mi,
SlotIndex MIIdx,
MachineOperand& MO,
unsigned MOIdx,
LiveInterval &interval) {
DEBUG(dbgs() << "\t\tregister: " << PrintReg(interval.reg, tri_));
// Virtual registers may be defined multiple times (due to phi
// elimination and 2-addr elimination). Much of what we do only has to be
// done once for the vreg. We use an empty interval to detect the first
// time we see a vreg.
LiveVariables::VarInfo& vi = lv_->getVarInfo(interval.reg);
if (interval.empty()) {
// Get the Idx of the defining instructions.
SlotIndex defIndex = MIIdx.getDefIndex();
// Earlyclobbers move back one, so that they overlap the live range
// of inputs.
if (MO.isEarlyClobber())
defIndex = MIIdx.getUseIndex();
// Make sure the first definition is not a partial redefinition. Add an
// <imp-def> of the full register.
if (MO.getSubReg())
mi->addRegisterDefined(interval.reg);
MachineInstr *CopyMI = NULL;
if (mi->isCopyLike()) {
CopyMI = mi;
}
VNInfo *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?
SlotIndex killIdx;
if (vi.Kills[0] != mi)
killIdx = getInstructionIndex(vi.Kills[0]).getDefIndex();
else
killIdx = defIndex.getStoreIndex();
// If the kill happens after the definition, we have an intra-block
// live range.
if (killIdx > defIndex) {
assert(vi.AliveBlocks.empty() &&
"Shouldn't be alive across any blocks!");
LiveRange LR(defIndex, killIdx, ValNo);
interval.addRange(LR);
DEBUG(dbgs() << " +" << LR << "\n");
return;
}
}
// The other case we handle is when a virtual register lives to the end
// of the defining block, potentially live across some blocks, then is
// live into some number of blocks, but gets killed. Start by adding a
// range that goes from this definition to the end of the defining block.
LiveRange NewLR(defIndex, getMBBEndIdx(mbb), ValNo);
DEBUG(dbgs() << " +" << NewLR);
interval.addRange(NewLR);
bool PHIJoin = lv_->isPHIJoin(interval.reg);
if (PHIJoin) {
// A phi join register is killed at the end of the MBB and revived as a new
// valno in the killing blocks.
assert(vi.AliveBlocks.empty() && "Phi join can't pass through blocks");
DEBUG(dbgs() << " phi-join");
ValNo->setHasPHIKill(true);
} else {
// Iterate over all of the blocks that the variable is completely
// live in, adding [insrtIndex(begin), instrIndex(end)+4) to the
// live interval.
for (SparseBitVector<>::iterator I = vi.AliveBlocks.begin(),
E = vi.AliveBlocks.end(); I != E; ++I) {
MachineBasicBlock *aliveBlock = mf_->getBlockNumbered(*I);
LiveRange LR(getMBBStartIdx(aliveBlock), getMBBEndIdx(aliveBlock), ValNo);
interval.addRange(LR);
DEBUG(dbgs() << " +" << LR);
}
}
// Finally, this virtual register is live from the start of any killing
// block to the 'use' slot of the killing instruction.
for (unsigned i = 0, e = vi.Kills.size(); i != e; ++i) {
MachineInstr *Kill = vi.Kills[i];
SlotIndex Start = getMBBStartIdx(Kill->getParent());
SlotIndex killIdx = getInstructionIndex(Kill).getDefIndex();
// Create interval with one of a NEW value number. Note that this value
// number isn't actually defined by an instruction, weird huh? :)
if (PHIJoin) {
assert(getInstructionFromIndex(Start) == 0 &&
"PHI def index points at actual instruction.");
ValNo = interval.getNextValue(Start, 0, VNInfoAllocator);
ValNo->setIsPHIDef(true);
}
LiveRange LR(Start, killIdx, ValNo);
interval.addRange(LR);
DEBUG(dbgs() << " +" << LR);
}
} else {
if (MultipleDefsBySameMI(*mi, MOIdx))
// Multiple defs of the same virtual register by the same instruction.
// e.g. %reg1031:5<def>, %reg1031:6<def> = VLD1q16 %reg1024<kill>, ...
// This is likely due to elimination of REG_SEQUENCE instructions. Return
// here since there is nothing to do.
return;
// If this is the second time we see a virtual register definition, it
// must be due to phi elimination or two addr elimination. If this is
// the result of two address elimination, then the vreg is one of the
// def-and-use register operand.
// It may also be partial redef like this:
// 80 %reg1041:6<def> = VSHRNv4i16 %reg1034<kill>, 12, pred:14, pred:%reg0
// 120 %reg1041:5<def> = VSHRNv4i16 %reg1039<kill>, 12, pred:14, pred:%reg0
bool PartReDef = isPartialRedef(MIIdx, MO, interval);
if (PartReDef || mi->isRegTiedToUseOperand(MOIdx)) {
// If this is a two-address definition, then we have already processed
// the live range. The only problem is that we didn't realize there
// are actually two values in the live interval. Because of this we
// need to take the LiveRegion that defines this register and split it
// into two values.
SlotIndex RedefIndex = MIIdx.getDefIndex();
if (MO.isEarlyClobber())
RedefIndex = MIIdx.getUseIndex();
const LiveRange *OldLR =
interval.getLiveRangeContaining(RedefIndex.getUseIndex());
VNInfo *OldValNo = OldLR->valno;
SlotIndex DefIndex = OldValNo->def.getDefIndex();
// Delete the previous value, which should be short and continuous,
// because the 2-addr copy must be in the same MBB as the redef.
interval.removeRange(DefIndex, RedefIndex);
// The new value number (#1) is defined by the instruction we claimed
// defined value #0.
VNInfo *ValNo = interval.createValueCopy(OldValNo, VNInfoAllocator);
// Value#0 is now defined by the 2-addr instruction.
OldValNo->def = RedefIndex;
OldValNo->setCopy(0);
// A re-def may be a copy. e.g. %reg1030:6<def> = VMOVD %reg1026, ...
if (PartReDef && mi->isCopyLike())
OldValNo->setCopy(&*mi);
// Add the new live interval which replaces the range for the input copy.
LiveRange LR(DefIndex, RedefIndex, ValNo);
DEBUG(dbgs() << " replace range with " << LR);
interval.addRange(LR);
// If this redefinition is dead, we need to add a dummy unit live
// range covering the def slot.
if (MO.isDead())
interval.addRange(LiveRange(RedefIndex, RedefIndex.getStoreIndex(),
OldValNo));
DEBUG({
dbgs() << " RESULT: ";
interval.print(dbgs(), tri_);
});
} else if (lv_->isPHIJoin(interval.reg)) {
// In the case of PHI elimination, each variable definition is only
// live until the end of the block. We've already taken care of the
// rest of the live range.
SlotIndex defIndex = MIIdx.getDefIndex();
if (MO.isEarlyClobber())
defIndex = MIIdx.getUseIndex();
VNInfo *ValNo;
MachineInstr *CopyMI = NULL;
if (mi->isCopyLike())
CopyMI = mi;
ValNo = interval.getNextValue(defIndex, CopyMI, VNInfoAllocator);
SlotIndex killIndex = getMBBEndIdx(mbb);
LiveRange LR(defIndex, killIndex, ValNo);
interval.addRange(LR);
ValNo->setHasPHIKill(true);
DEBUG(dbgs() << " phi-join +" << LR);
} else {
llvm_unreachable("Multiply defined register");
}
}
DEBUG(dbgs() << '\n');
}
void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB,
MachineBasicBlock::iterator mi,
SlotIndex MIIdx,
MachineOperand& MO,
LiveInterval &interval,
MachineInstr *CopyMI) {
// A physical register cannot be live across basic block, so its
// lifetime must end somewhere in its defining basic block.
DEBUG(dbgs() << "\t\tregister: " << PrintReg(interval.reg, tri_));
SlotIndex baseIndex = MIIdx;
SlotIndex start = baseIndex.getDefIndex();
// Earlyclobbers move back one.
if (MO.isEarlyClobber())
start = MIIdx.getUseIndex();
SlotIndex end = start;
// If it is not used after definition, it is considered dead at
// the instruction defining it. Hence its interval is:
// [defSlot(def), defSlot(def)+1)
// For earlyclobbers, the defSlot was pushed back one; the extra
// advance below compensates.
if (MO.isDead()) {
DEBUG(dbgs() << " dead");
end = start.getStoreIndex();
goto exit;
}
// If it is not dead on definition, it must be killed by a
// subsequent instruction. Hence its interval is:
// [defSlot(def), useSlot(kill)+1)
baseIndex = baseIndex.getNextIndex();
while (++mi != MBB->end()) {
if (mi->isDebugValue())
continue;
if (getInstructionFromIndex(baseIndex) == 0)
baseIndex = indexes_->getNextNonNullIndex(baseIndex);
if (mi->killsRegister(interval.reg, tri_)) {
DEBUG(dbgs() << " killed");
end = baseIndex.getDefIndex();
goto exit;
} else {
int DefIdx = mi->findRegisterDefOperandIdx(interval.reg,false,false,tri_);
if (DefIdx != -1) {
if (mi->isRegTiedToUseOperand(DefIdx)) {
// Two-address instruction.
end = baseIndex.getDefIndex();
} else {
// Another instruction redefines the register before it is ever read.
// Then the register is essentially dead at the instruction that
// defines it. Hence its interval is:
// [defSlot(def), defSlot(def)+1)
DEBUG(dbgs() << " dead");
end = start.getStoreIndex();
}
goto exit;
}
}
baseIndex = baseIndex.getNextIndex();
}
// The only case we should have a dead physreg here without a killing or
// instruction where we know it's dead is if it is live-in to the function
// and never used. Another possible case is the implicit use of the
// physical register has been deleted by two-address pass.
end = start.getStoreIndex();
exit:
assert(start < end && "did not find end of interval?");
// Already exists? Extend old live interval.
VNInfo *ValNo = interval.getVNInfoAt(start);
bool Extend = ValNo != 0;
if (!Extend)
ValNo = interval.getNextValue(start, CopyMI, VNInfoAllocator);
if (Extend && MO.isEarlyClobber())
ValNo->setHasRedefByEC(true);
LiveRange LR(start, end, ValNo);
interval.addRange(LR);
DEBUG(dbgs() << " +" << LR << '\n');
}
void LiveIntervals::handleRegisterDef(MachineBasicBlock *MBB,
MachineBasicBlock::iterator MI,
SlotIndex MIIdx,
MachineOperand& MO,
unsigned MOIdx) {
if (TargetRegisterInfo::isVirtualRegister(MO.getReg()))
handleVirtualRegisterDef(MBB, MI, MIIdx, MO, MOIdx,
getOrCreateInterval(MO.getReg()));
else {
MachineInstr *CopyMI = NULL;
if (MI->isCopyLike())
CopyMI = MI;
handlePhysicalRegisterDef(MBB, MI, MIIdx, MO,
getOrCreateInterval(MO.getReg()), CopyMI);
}
}
void LiveIntervals::handleLiveInRegister(MachineBasicBlock *MBB,
SlotIndex MIIdx,
LiveInterval &interval, bool isAlias) {
DEBUG(dbgs() << "\t\tlivein register: " << PrintReg(interval.reg, tri_));
// Look for kills, if it reaches a def before it's killed, then it shouldn't
// be considered a livein.
MachineBasicBlock::iterator mi = MBB->begin();
MachineBasicBlock::iterator E = MBB->end();
// Skip over DBG_VALUE at the start of the MBB.
if (mi != E && mi->isDebugValue()) {
while (++mi != E && mi->isDebugValue())
;
if (mi == E)
// MBB is empty except for DBG_VALUE's.
return;
}
SlotIndex baseIndex = MIIdx;
SlotIndex start = baseIndex;
if (getInstructionFromIndex(baseIndex) == 0)
baseIndex = indexes_->getNextNonNullIndex(baseIndex);
SlotIndex end = baseIndex;
bool SeenDefUse = false;
while (mi != E) {
if (mi->killsRegister(interval.reg, tri_)) {
DEBUG(dbgs() << " killed");
end = baseIndex.getDefIndex();
SeenDefUse = true;
break;
} else if (mi->definesRegister(interval.reg, tri_)) {
// Another instruction redefines the register before it is ever read.
// Then the register is essentially dead at the instruction that defines
// it. Hence its interval is:
// [defSlot(def), defSlot(def)+1)
DEBUG(dbgs() << " dead");
end = start.getStoreIndex();
SeenDefUse = true;
break;
}
while (++mi != E && mi->isDebugValue())
// Skip over DBG_VALUE.
;
if (mi != E)
baseIndex = indexes_->getNextNonNullIndex(baseIndex);
}
// Live-in register might not be used at all.
if (!SeenDefUse) {
if (isAlias) {
DEBUG(dbgs() << " dead");
end = MIIdx.getStoreIndex();
} else {
DEBUG(dbgs() << " live through");
end = getMBBEndIdx(MBB);
}
}
SlotIndex defIdx = getMBBStartIdx(MBB);
assert(getInstructionFromIndex(defIdx) == 0 &&
"PHI def index points at actual instruction.");
VNInfo *vni =
interval.getNextValue(defIdx, 0, VNInfoAllocator);
vni->setIsPHIDef(true);
LiveRange LR(start, end, vni);
interval.addRange(LR);
DEBUG(dbgs() << " +" << LR << '\n');
}
/// computeIntervals - computes the live intervals for virtual
/// registers. for some ordering of the machine instructions [1,N] a
/// live interval is an interval [i, j) where 1 <= i <= j < N for
/// which a variable is live
void LiveIntervals::computeIntervals() {
DEBUG(dbgs() << "********** COMPUTING LIVE INTERVALS **********\n"
<< "********** Function: "
<< ((Value*)mf_->getFunction())->getName() << '\n');
SmallVector<unsigned, 8> UndefUses;
for (MachineFunction::iterator MBBI = mf_->begin(), E = mf_->end();
MBBI != E; ++MBBI) {
MachineBasicBlock *MBB = MBBI;
if (MBB->empty())
continue;
// Track the index of the current machine instr.
SlotIndex MIIndex = getMBBStartIdx(MBB);
DEBUG(dbgs() << "BB#" << MBB->getNumber()
<< ":\t\t# derived from " << MBB->getName() << "\n");
// Create intervals for live-ins to this BB first.
for (MachineBasicBlock::livein_iterator LI = MBB->livein_begin(),
LE = MBB->livein_end(); LI != LE; ++LI) {
handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*LI));
// 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.
if (getInstructionFromIndex(MIIndex) == 0)
MIIndex = indexes_->getNextNonNullIndex(MIIndex);
for (MachineBasicBlock::iterator MI = MBB->begin(), miEnd = MBB->end();
MI != miEnd; ++MI) {
DEBUG(dbgs() << MIIndex << "\t" << *MI);
if (MI->isDebugValue())
continue;
// Handle defs.
for (int i = MI->getNumOperands() - 1; i >= 0; --i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.getReg())
continue;
// handle register defs - build intervals
if (MO.isDef())
handleRegisterDef(MBB, MI, MIIndex, MO, i);
else if (MO.isUndef())
UndefUses.push_back(MO.getReg());
}
// Move to the next instr slot.
MIIndex = indexes_->getNextNonNullIndex(MIIndex);
}
}
// Create empty intervals for registers defined by implicit_def's (except
// for those implicit_def that define values which are liveout of their
// blocks.
for (unsigned i = 0, e = UndefUses.size(); i != e; ++i) {
unsigned UndefReg = UndefUses[i];
(void)getOrCreateInterval(UndefReg);
}
}
LiveInterval* LiveIntervals::createInterval(unsigned reg) {
float Weight = TargetRegisterInfo::isPhysicalRegister(reg) ? HUGE_VALF : 0.0F;
return new LiveInterval(reg, Weight);
}
/// dupInterval - Duplicate a live interval. The caller is responsible for
/// managing the allocated memory.
LiveInterval* LiveIntervals::dupInterval(LiveInterval *li) {
LiveInterval *NewLI = createInterval(li->reg);
NewLI->Copy(*li, mri_, getVNInfoAllocator());
return NewLI;
}
/// shrinkToUses - After removing some uses of a register, shrink its live
/// range to just the remaining uses. This method does not compute reaching
/// defs for new uses, and it doesn't remove dead defs.
bool LiveIntervals::shrinkToUses(LiveInterval *li,
SmallVectorImpl<MachineInstr*> *dead) {
DEBUG(dbgs() << "Shrink: " << *li << '\n');
assert(TargetRegisterInfo::isVirtualRegister(li->reg)
&& "Can't only shrink physical registers");
// Find all the values used, including PHI kills.
SmallVector<std::pair<SlotIndex, VNInfo*>, 16> WorkList;
// Visit all instructions reading li->reg.
for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(li->reg);
MachineInstr *UseMI = I.skipInstruction();) {
if (UseMI->isDebugValue() || !UseMI->readsVirtualRegister(li->reg))
continue;
SlotIndex Idx = getInstructionIndex(UseMI).getUseIndex();
VNInfo *VNI = li->getVNInfoAt(Idx);
if (!VNI) {
// This shouldn't happen: readsVirtualRegister returns true, but there is
// no live value. It is likely caused by a target getting <undef> flags
// wrong.
DEBUG(dbgs() << Idx << '\t' << *UseMI
<< "Warning: Instr claims to read non-existent value in "
<< *li << '\n');
continue;
}
if (VNI->def == Idx) {
// Special case: An early-clobber tied operand reads and writes the
// register one slot early.
Idx = Idx.getPrevSlot();
VNI = li->getVNInfoAt(Idx);
assert(VNI && "Early-clobber tied value not available");
}
WorkList.push_back(std::make_pair(Idx, VNI));
}
// Create a new live interval with only minimal live segments per def.
LiveInterval NewLI(li->reg, 0);
for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused())
continue;
// We may eliminate PHI values, so recompute PHIKill flags.
VNI->setHasPHIKill(false);
NewLI.addRange(LiveRange(VNI->def, VNI->def.getNextSlot(), VNI));
// A use tied to an early-clobber def ends at the load slot and isn't caught
// above. Catch it here instead. This probably only ever happens for inline
// assembly.
if (VNI->def.isUse())
if (VNInfo *UVNI = li->getVNInfoAt(VNI->def.getLoadIndex()))
WorkList.push_back(std::make_pair(VNI->def.getLoadIndex(), UVNI));
}
// Keep track of the PHIs that are in use.
SmallPtrSet<VNInfo*, 8> UsedPHIs;
// Extend intervals to reach all uses in WorkList.
while (!WorkList.empty()) {
SlotIndex Idx = WorkList.back().first;
VNInfo *VNI = WorkList.back().second;
WorkList.pop_back();
const MachineBasicBlock *MBB = getMBBFromIndex(Idx);
SlotIndex BlockStart = getMBBStartIdx(MBB);
// Extend the live range for VNI to be live at Idx.
if (VNInfo *ExtVNI = NewLI.extendInBlock(BlockStart, Idx)) {
(void)ExtVNI;
assert(ExtVNI == VNI && "Unexpected existing value number");
// Is this a PHIDef we haven't seen before?
if (!VNI->isPHIDef() || VNI->def != BlockStart || !UsedPHIs.insert(VNI))
continue;
// The PHI is live, make sure the predecessors are live-out.
for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
SlotIndex Stop = getMBBEndIdx(*PI).getPrevSlot();
VNInfo *PVNI = li->getVNInfoAt(Stop);
// A predecessor is not required to have a live-out value for a PHI.
if (PVNI) {
PVNI->setHasPHIKill(true);
WorkList.push_back(std::make_pair(Stop, PVNI));
}
}
continue;
}
// VNI is live-in to MBB.
DEBUG(dbgs() << " live-in at " << BlockStart << '\n');
NewLI.addRange(LiveRange(BlockStart, Idx.getNextSlot(), VNI));
// Make sure VNI is live-out from the predecessors.
for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
SlotIndex Stop = getMBBEndIdx(*PI).getPrevSlot();
assert(li->getVNInfoAt(Stop) == VNI && "Wrong value out of predecessor");
WorkList.push_back(std::make_pair(Stop, VNI));
}
}
// Handle dead values.
bool CanSeparate = false;
for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused())
continue;
LiveInterval::iterator LII = NewLI.FindLiveRangeContaining(VNI->def);
assert(LII != NewLI.end() && "Missing live range for PHI");
if (LII->end != VNI->def.getNextSlot())
continue;
if (VNI->isPHIDef()) {
// This is a dead PHI. Remove it.
VNI->setIsUnused(true);
NewLI.removeRange(*LII);
DEBUG(dbgs() << "Dead PHI at " << VNI->def << " may separate interval\n");
CanSeparate = true;
} else {
// This is a dead def. Make sure the instruction knows.
MachineInstr *MI = getInstructionFromIndex(VNI->def);
assert(MI && "No instruction defining live value");
MI->addRegisterDead(li->reg, tri_);
if (dead && MI->allDefsAreDead()) {
DEBUG(dbgs() << "All defs dead: " << VNI->def << '\t' << *MI);
dead->push_back(MI);
}
}
}
// Move the trimmed ranges back.
li->ranges.swap(NewLI.ranges);
DEBUG(dbgs() << "Shrunk: " << *li << '\n');
return CanSeparate;
}
//===----------------------------------------------------------------------===//
// Register allocator hooks.
//
MachineBasicBlock::iterator
LiveIntervals::getLastSplitPoint(const LiveInterval &li,
MachineBasicBlock *mbb) const {
const MachineBasicBlock *lpad = mbb->getLandingPadSuccessor();
// If li is not live into a landing pad, we can insert spill code before the
// first terminator.
if (!lpad || !isLiveInToMBB(li, lpad))
return mbb->getFirstTerminator();
// When there is a landing pad, spill code must go before the call instruction
// that can throw.
MachineBasicBlock::iterator I = mbb->end(), B = mbb->begin();
while (I != B) {
--I;
if (I->getDesc().isCall())
return I;
}
// The block contains no calls that can throw, so use the first terminator.
return mbb->getFirstTerminator();
}
void LiveIntervals::addKillFlags() {
for (iterator I = begin(), E = end(); I != E; ++I) {
unsigned Reg = I->first;
if (TargetRegisterInfo::isPhysicalRegister(Reg))
continue;
if (mri_->reg_nodbg_empty(Reg))
continue;
LiveInterval *LI = I->second;
// Every instruction that kills Reg corresponds to a live range end point.
for (LiveInterval::iterator RI = LI->begin(), RE = LI->end(); RI != RE;
++RI) {
// A LOAD index indicates an MBB edge.
if (RI->end.isLoad())
continue;
MachineInstr *MI = getInstructionFromIndex(RI->end);
if (!MI)
continue;
MI->addRegisterKilled(Reg, NULL);
}
}
}
/// getReMatImplicitUse - If the remat definition MI has one (for now, we only
/// allow one) virtual register operand, then its uses are implicitly using
/// the register. Returns the virtual register.
unsigned LiveIntervals::getReMatImplicitUse(const LiveInterval &li,
MachineInstr *MI) const {
unsigned RegOp = 0;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isUse())
continue;
unsigned Reg = MO.getReg();
if (Reg == 0 || Reg == li.reg)
continue;
if (TargetRegisterInfo::isPhysicalRegister(Reg) &&
!allocatableRegs_[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,
SlotIndex UseIdx) const {
VNInfo *UValNo = li.getVNInfoAt(UseIdx);
return UValNo && UValNo == li.getVNInfoAt(getInstructionIndex(MI));
}
/// isReMaterializable - Returns true if the definition MI of the specified
/// val# of the specified interval is re-materializable.
bool
LiveIntervals::isReMaterializable(const LiveInterval &li,
const VNInfo *ValNo, MachineInstr *MI,
const SmallVectorImpl<LiveInterval*> *SpillIs,
bool &isLoad) {
if (DisableReMat)
return false;
if (!tii_->isTriviallyReMaterializable(MI, aa_))
return false;
// Target-specific code can mark an instruction as being rematerializable
// if it has one virtual reg use, though it had better be something like
// a PIC base register which is likely to be live everywhere.
unsigned ImpUse = getReMatImplicitUse(li, MI);
if (ImpUse) {
const LiveInterval &ImpLi = getInterval(ImpUse);
for (MachineRegisterInfo::use_nodbg_iterator
ri = mri_->use_nodbg_begin(li.reg), re = mri_->use_nodbg_end();
ri != re; ++ri) {
MachineInstr *UseMI = &*ri;
SlotIndex UseIdx = getInstructionIndex(UseMI);
if (li.getVNInfoAt(UseIdx) != ValNo)
continue;
if (!isValNoAvailableAt(ImpLi, MI, UseIdx))
return false;
}
// If a register operand of the re-materialized instruction is going to
// be spilled next, then it's not legal to re-materialize this instruction.
if (SpillIs)
for (unsigned i = 0, e = SpillIs->size(); i != e; ++i)
if (ImpUse == (*SpillIs)[i]->reg)
return false;
}
return true;
}
/// isReMaterializable - Returns true if 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 Dummy2;
return isReMaterializable(li, ValNo, MI, 0, 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,
const SmallVectorImpl<LiveInterval*> *SpillIs,
bool &isLoad) {
isLoad = false;
for (LiveInterval::const_vni_iterator i = li.vni_begin(), e = li.vni_end();
i != e; ++i) {
const VNInfo *VNI = *i;
if (VNI->isUnused())
continue; // Dead val#.
// Is the def for the val# rematerializable?
MachineInstr *ReMatDefMI = getInstructionFromIndex(VNI->def);
if (!ReMatDefMI)
return false;
bool DefIsLoad = false;
if (!ReMatDefMI ||
!isReMaterializable(li, VNI, ReMatDefMI, SpillIs, DefIsLoad))
return false;
isLoad |= DefIsLoad;
}
return true;
}
/// 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,
SlotIndex InstrIdx,
SmallVector<unsigned, 2> &Ops,
bool isSS, int Slot, unsigned Reg) {
// If it is an implicit def instruction, just delete it.
if (MI->isImplicitDef()) {
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(MI, FoldOps, Slot)
: tii_->foldMemoryOperand(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.
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);
ReplaceMachineInstrInMaps(MI, fmi);
MI->eraseFromParent();
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 {
LiveInterval::Ranges::const_iterator itr = li.ranges.begin();
MachineBasicBlock *mbb = indexes_->getMBBCoveringRange(itr->start, itr->end);
if (mbb == 0)
return false;
for (++itr; itr != li.ranges.end(); ++itr) {
MachineBasicBlock *mbb2 =
indexes_->getMBBCoveringRange(itr->start, itr->end);
if (mbb2 != mbb)
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 (!TargetRegisterInfo::isVirtualRegister(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, SlotIndex index, SlotIndex 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();
if (!TargetRegisterInfo::isVirtualRegister(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) {
DEBUG(dbgs() << "\t\t\t\tErasing re-materializable def: "
<< *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.
SmallVector<unsigned, 2> Ops;
tie(HasUse, HasDef) = MI->readsWritesVirtualRegister(Reg, &Ops);
// 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;
// The new virtual register should get the same allocation hints as the
// old one.
std::pair<unsigned, unsigned> Hint = mri_->getRegAllocationHint(Reg);
if (Hint.first || Hint.second)
mri_->setRegAllocationHint(NewVReg, Hint.first, Hint.second);
}
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.
bool HasEarlyClobber = false;
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 (mopj.isEarlyClobber())
HasEarlyClobber = true;
}
if (CreatedNewVReg) {
if (DefIsReMat) {
vrm.setVirtIsReMaterialized(NewVReg, ReMatDefMI);
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(index.getLoadIndex(), index.getDefIndex(),
nI.getNextValue(SlotIndex(), 0, VNInfoAllocator));
DEBUG(dbgs() << " +" << LR);
nI.addRange(LR);
} else {
// Extend the split live interval to this def / use.
SlotIndex End = index.getDefIndex();
LiveRange LR(nI.ranges[nI.ranges.size()-1].end, End,
nI.getValNumInfo(nI.getNumValNums()-1));
DEBUG(dbgs() << " +" << LR);
nI.addRange(LR);
}
}
if (HasDef) {
// An early clobber starts at the use slot, except for an early clobber
// tied to a use operand (yes, that is a thing).
LiveRange LR(HasEarlyClobber && !HasUse ?
index.getUseIndex() : index.getDefIndex(),
index.getStoreIndex(),
nI.getNextValue(SlotIndex(), 0, VNInfoAllocator));
DEBUG(dbgs() << " +" << LR);
nI.addRange(LR);
}
DEBUG({
dbgs() << "\t\t\t\tAdded new interval: ";
nI.print(dbgs(), tri_);
dbgs() << '\n';
});
}
return CanFold;
}
bool LiveIntervals::anyKillInMBBAfterIdx(const LiveInterval &li,
const VNInfo *VNI,
MachineBasicBlock *MBB,
SlotIndex Idx) const {
return li.killedInRange(Idx.getNextSlot(), getMBBEndIdx(MBB));
}
/// RewriteInfo - Keep track of machine instrs that will be rewritten
/// during spilling.
namespace {
struct RewriteInfo {
SlotIndex Index;
MachineInstr *MI;
RewriteInfo(SlotIndex i, MachineInstr *mi) : Index(i), MI(mi) {}
};
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;
SlotIndex start = I->start.getBaseIndex();
SlotIndex end = I->end.getPrevSlot().getBaseIndex().getNextIndex();
// 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;
if (MI->isDebugValue()) {
// Modify DBG_VALUE now that the value is in a spill slot.
if (Slot != VirtRegMap::MAX_STACK_SLOT || isLoadSS) {
uint64_t Offset = MI->getOperand(1).getImm();
const MDNode *MDPtr = MI->getOperand(2).getMetadata();
DebugLoc DL = MI->getDebugLoc();
int FI = isLoadSS ? LdSlot : (int)Slot;
if (MachineInstr *NewDV = tii_->emitFrameIndexDebugValue(*mf_, FI,
Offset, MDPtr, DL)) {
DEBUG(dbgs() << "Modifying debug info due to spill:" << "\t" << *MI);
ReplaceMachineInstrInMaps(MI, NewDV);
MachineBasicBlock *MBB = MI->getParent();
MBB->insert(MBB->erase(MI), NewDV);
continue;
}
}
DEBUG(dbgs() << "Removing debug info due to spill:" << "\t" << *MI);
RemoveMachineInstrFromMaps(MI);
vrm.RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
continue;
}
assert(!(O.isImplicit() && O.isUse()) &&
"Spilling register that's used as implicit use?");
SlotIndex index = getInstructionIndex(MI);
if (index < start || index >= end)
continue;
if (O.isUndef())
// 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));
}
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;
SlotIndex index = rwi.Index;
MachineInstr *MI = rwi.MI;
// If MI def and/or use the same register multiple times, then there
// are multiple entries.
while (i != e && RewriteMIs[i].MI == MI) {
assert(RewriteMIs[i].Index == index);
++i;
}
MachineBasicBlock *MBB = MI->getParent();
if (ImpUse && MI != ReMatDefMI) {
// Re-matting an instruction with virtual register use. Prevent interval
// from being spilled.
getInterval(ImpUse).markNotSpillable();
}
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 artificially
// extend the new interval.
if (MI->readsWritesVirtualRegister(li.reg) ==
std::make_pair(false,true)) {
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.markNotSpillable();
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, index.getDefIndex());
else {
// If this is a two-address code, then this index starts a new VNInfo.
const VNInfo *VNI = li.findDefinedVNInfoForRegInt(index.getDefIndex());
if (VNI)
HasKill = anyKillInMBBAfterIdx(li, VNI, MBB, index.getDefIndex());
}
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 (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 &&
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 &&
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, SlotIndex 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, SlotIndex 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 = SlotIndex();
}
/// 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 (MI->isDebugValue()) {
// Remove debug info for now.
O.setReg(0U);
DEBUG(dbgs() << "Removing debug info due to spill:" << "\t" << *MI);
continue;
}
if (O.isDef()) {
assert(MI->isImplicitDef() &&
"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);
MO.setIsUndef();
}
}
}
}
}
float
LiveIntervals::getSpillWeight(bool isDef, bool isUse, unsigned loopDepth) {
// Limit the loop depth ridiculousness.
if (loopDepth > 200)
loopDepth = 200;
// The loop depth is used to roughly estimate the number of times the
// instruction is executed. Something like 10^d is simple, but will quickly
// overflow a float. This expression behaves like 10^d for small d, but is
// more tempered for large d. At d=200 we get 6.7e33 which leaves a bit of
// headroom before overflow.
// By the way, powf() might be unavailable here. For consistency,
// We may take pow(double,double).
float lc = std::pow(1 + (100.0 / (loopDepth + 10)), (double)loopDepth);
return (isDef + isUse) * lc;
}
static void normalizeSpillWeights(std::vector<LiveInterval*> &NewLIs) {
for (unsigned i = 0, e = NewLIs.size(); i != e; ++i)
NewLIs[i]->weight =
normalizeSpillWeight(NewLIs[i]->weight, NewLIs[i]->getSize());
}
std::vector<LiveInterval*> LiveIntervals::
addIntervalsForSpills(const LiveInterval &li,
const SmallVectorImpl<LiveInterval*> *SpillIs,
const MachineLoopInfo *loopInfo, VirtRegMap &vrm) {
assert(li.isSpillable() && "attempt to spill already spilled interval!");
DEBUG({
dbgs() << "\t\t\t\tadding intervals for spills for interval: ";
li.print(dbgs(), tri_);
dbgs() << '\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.
SlotIndex KillIdx = vrm.getKillPoint(li.reg);
if (KillIdx != SlotIndex()) {
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);
normalizeSpillWeights(NewLIs);
return NewLIs;
}
bool TrySplit = !intervalIsInOneMBB(li);
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;
if (VNI->isUnused())
continue; // Dead val#.
// Is the def for the val# rematerializable?
MachineInstr *ReMatDefMI = getInstructionFromIndex(VNI->def);
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);
CloneMIs.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);
normalizeSpillWeights(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) {
SlotIndex 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(index.getLoadIndex(), index.getDefIndex());
}
nI.removeRange(index.getDefIndex(), index.getStoreIndex());
}
}
// Otherwise tell the spiller to issue a spill.
if (!Folded) {
LiveRange *LR = &nI.ranges[nI.ranges.size()-1];
bool isKill = LR->end == index.getStoreIndex();
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) {
SlotIndex index = restores[i].index;
if (index == SlotIndex())
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 mark the register
// interval as unspillable.
LiveInterval &ImpLi = getInterval(ImpUse);
ImpLi.markNotSpillable();
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(index.getLoadIndex(), index.getDefIndex());
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()) {
if (!AddedKill.count(LI)) {
LiveRange *LR = &LI->ranges[LI->ranges.size()-1];
SlotIndex LastUseIdx = LR->end.getBaseIndex();
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);
normalizeSpillWeights(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();
if (MI->isDebugValue())
continue;
SlotIndex 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);
DEBUG(dbgs() << "spillPhysRegAroundRegDefsUses " << tri_->getName(PhysReg)
<< " represented by " << tri_->getName(SpillReg) << '\n');
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;
SmallVector<unsigned, 4> PRegs;
if (hasInterval(SpillReg))
PRegs.push_back(SpillReg);
for (const unsigned *SR = tri_->getSubRegisters(SpillReg); *SR; ++SR)
if (hasInterval(*SR))
PRegs.push_back(*SR);
DEBUG({
dbgs() << "Trying to spill:";
for (unsigned i = 0, e = PRegs.size(); i != e; ++i)
dbgs() << ' ' << tri_->getName(PRegs[i]);
dbgs() << '\n';
});
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 (MI->isDebugValue() || SeenMIs.count(MI))
continue;
SeenMIs.insert(MI);
SlotIndex Index = getInstructionIndex(MI);
bool LiveReg = false;
for (unsigned i = 0, e = PRegs.size(); i != e; ++i) {
unsigned PReg = PRegs[i];
LiveInterval &pli = getInterval(PReg);
if (!pli.liveAt(Index))
continue;
LiveReg = true;
SlotIndex StartIdx = Index.getLoadIndex();
SlotIndex EndIdx = Index.getNextIndex().getBaseIndex();
if (!pli.isInOneLiveRange(StartIdx, EndIdx)) {
std::string msg;
raw_string_ostream Msg(msg);
Msg << "Ran out of registers during register allocation!";
if (MI->isInlineAsm()) {
Msg << "\nPlease check your inline asm statement for invalid "
<< "constraints:\n";
MI->print(Msg, tm_);
}
report_fatal_error(Msg.str());
}
pli.removeRange(StartIdx, EndIdx);
LiveReg = true;
}
if (!LiveReg)
continue;
DEBUG(dbgs() << "Emergency spill around " << Index << '\t' << *MI);
vrm.addEmergencySpill(SpillReg, MI);
Cut = true;
}
return Cut;
}
LiveRange LiveIntervals::addLiveRangeToEndOfBlock(unsigned reg,
MachineInstr* startInst) {
LiveInterval& Interval = getOrCreateInterval(reg);
VNInfo* VN = Interval.getNextValue(
SlotIndex(getInstructionIndex(startInst).getDefIndex()),
startInst, getVNInfoAllocator());
VN->setHasPHIKill(true);
LiveRange LR(
SlotIndex(getInstructionIndex(startInst).getDefIndex()),
getMBBEndIdx(startInst->getParent()), VN);
Interval.addRange(LR);
return LR;
}
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