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llvm-6502/lib/CodeGen/SplitKit.cpp
Jakob Stoklund Olesen 5881799d0c Delete dead code after rematerializing. 
LiveRangeEdit::eliminateDeadDefs() will eventually be used by coalescing,
splitting, and spilling for dead code elimination. It can delete chains of dead
instructions as long as there are no dependency loops.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127287 91177308-0d34-0410-b5e6-96231b3b80d8
2011-03-08 22:46:11 +00:00

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//===---------- SplitKit.cpp - Toolkit for splitting live ranges ----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the SplitAnalysis class as well as mutator functions for
// live range splitting.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regalloc"
#include "SplitKit.h"
#include "LiveRangeEdit.h"
#include "VirtRegMap.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/CalcSpillWeights.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
static cl::opt<bool>
AllowSplit("spiller-splits-edges",
cl::desc("Allow critical edge splitting during spilling"));
STATISTIC(NumFinished, "Number of splits finished");
STATISTIC(NumSimple, "Number of splits that were simple");
//===----------------------------------------------------------------------===//
// Split Analysis
//===----------------------------------------------------------------------===//
SplitAnalysis::SplitAnalysis(const VirtRegMap &vrm,
const LiveIntervals &lis,
const MachineLoopInfo &mli)
: MF(vrm.getMachineFunction()),
VRM(vrm),
LIS(lis),
Loops(mli),
TII(*MF.getTarget().getInstrInfo()),
CurLI(0) {}
void SplitAnalysis::clear() {
UseSlots.clear();
UsingInstrs.clear();
UsingBlocks.clear();
LiveBlocks.clear();
CurLI = 0;
}
bool SplitAnalysis::canAnalyzeBranch(const MachineBasicBlock *MBB) {
MachineBasicBlock *T, *F;
SmallVector<MachineOperand, 4> Cond;
return !TII.AnalyzeBranch(const_cast<MachineBasicBlock&>(*MBB), T, F, Cond);
}
/// analyzeUses - Count instructions, basic blocks, and loops using CurLI.
void SplitAnalysis::analyzeUses() {
const MachineRegisterInfo &MRI = MF.getRegInfo();
for (MachineRegisterInfo::reg_iterator I = MRI.reg_begin(CurLI->reg),
E = MRI.reg_end(); I != E; ++I) {
MachineOperand &MO = I.getOperand();
if (MO.isUse() && MO.isUndef())
continue;
MachineInstr *MI = MO.getParent();
if (MI->isDebugValue() || !UsingInstrs.insert(MI))
continue;
UseSlots.push_back(LIS.getInstructionIndex(MI).getDefIndex());
MachineBasicBlock *MBB = MI->getParent();
UsingBlocks[MBB]++;
}
array_pod_sort(UseSlots.begin(), UseSlots.end());
// Compute per-live block info.
if (!calcLiveBlockInfo()) {
// FIXME: calcLiveBlockInfo found inconsistencies in the live range.
// I am looking at you, SimpleRegisterCoalescing!
DEBUG(dbgs() << "*** Fixing inconsistent live interval! ***\n");
const_cast<LiveIntervals&>(LIS)
.shrinkToUses(const_cast<LiveInterval*>(CurLI));
LiveBlocks.clear();
bool fixed = calcLiveBlockInfo();
(void)fixed;
assert(fixed && "Couldn't fix broken live interval");
}
DEBUG(dbgs() << " counted "
<< UsingInstrs.size() << " instrs, "
<< UsingBlocks.size() << " blocks.\n");
}
/// calcLiveBlockInfo - Fill the LiveBlocks array with information about blocks
/// where CurLI is live.
bool SplitAnalysis::calcLiveBlockInfo() {
if (CurLI->empty())
return true;
LiveInterval::const_iterator LVI = CurLI->begin();
LiveInterval::const_iterator LVE = CurLI->end();
SmallVectorImpl<SlotIndex>::const_iterator UseI, UseE;
UseI = UseSlots.begin();
UseE = UseSlots.end();
// Loop over basic blocks where CurLI is live.
MachineFunction::iterator MFI = LIS.getMBBFromIndex(LVI->start);
for (;;) {
BlockInfo BI;
BI.MBB = MFI;
tie(BI.Start, BI.Stop) = LIS.getSlotIndexes()->getMBBRange(BI.MBB);
// The last split point is the latest possible insertion point that dominates
// all successor blocks. If interference reaches LastSplitPoint, it is not
// possible to insert a split or reload that makes CurLI live in the
// outgoing bundle.
MachineBasicBlock::iterator LSP = LIS.getLastSplitPoint(*CurLI, BI.MBB);
if (LSP == BI.MBB->end())
BI.LastSplitPoint = BI.Stop;
else
BI.LastSplitPoint = LIS.getInstructionIndex(LSP);
// LVI is the first live segment overlapping MBB.
BI.LiveIn = LVI->start <= BI.Start;
if (!BI.LiveIn)
BI.Def = LVI->start;
// Find the first and last uses in the block.
BI.Uses = hasUses(MFI);
if (BI.Uses && UseI != UseE) {
BI.FirstUse = *UseI;
assert(BI.FirstUse >= BI.Start);
do ++UseI;
while (UseI != UseE && *UseI < BI.Stop);
BI.LastUse = UseI[-1];
assert(BI.LastUse < BI.Stop);
}
// Look for gaps in the live range.
bool hasGap = false;
BI.LiveOut = true;
while (LVI->end < BI.Stop) {
SlotIndex LastStop = LVI->end;
if (++LVI == LVE || LVI->start >= BI.Stop) {
BI.Kill = LastStop;
BI.LiveOut = false;
break;
}
if (LastStop < LVI->start) {
hasGap = true;
BI.Kill = LastStop;
BI.Def = LVI->start;
}
}
// Don't set LiveThrough when the block has a gap.
BI.LiveThrough = !hasGap && BI.LiveIn && BI.LiveOut;
LiveBlocks.push_back(BI);
// FIXME: This should never happen. The live range stops or starts without a
// corresponding use. An earlier pass did something wrong.
if (!BI.LiveThrough && !BI.Uses)
return false;
// LVI is now at LVE or LVI->end >= Stop.
if (LVI == LVE)
break;
// Live segment ends exactly at Stop. Move to the next segment.
if (LVI->end == BI.Stop && ++LVI == LVE)
break;
// Pick the next basic block.
if (LVI->start < BI.Stop)
++MFI;
else
MFI = LIS.getMBBFromIndex(LVI->start);
}
return true;
}
bool SplitAnalysis::isOriginalEndpoint(SlotIndex Idx) const {
unsigned OrigReg = VRM.getOriginal(CurLI->reg);
const LiveInterval &Orig = LIS.getInterval(OrigReg);
assert(!Orig.empty() && "Splitting empty interval?");
LiveInterval::const_iterator I = Orig.find(Idx);
// Range containing Idx should begin at Idx.
if (I != Orig.end() && I->start <= Idx)
return I->start == Idx;
// Range does not contain Idx, previous must end at Idx.
return I != Orig.begin() && (--I)->end == Idx;
}
void SplitAnalysis::print(const BlockPtrSet &B, raw_ostream &OS) const {
for (BlockPtrSet::const_iterator I = B.begin(), E = B.end(); I != E; ++I) {
unsigned count = UsingBlocks.lookup(*I);
OS << " BB#" << (*I)->getNumber();
if (count)
OS << '(' << count << ')';
}
}
void SplitAnalysis::analyze(const LiveInterval *li) {
clear();
CurLI = li;
analyzeUses();
}
//===----------------------------------------------------------------------===//
// Split Editor
//===----------------------------------------------------------------------===//
/// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
SplitEditor::SplitEditor(SplitAnalysis &sa,
LiveIntervals &lis,
VirtRegMap &vrm,
MachineDominatorTree &mdt)
: SA(sa), LIS(lis), VRM(vrm),
MRI(vrm.getMachineFunction().getRegInfo()),
MDT(mdt),
TII(*vrm.getMachineFunction().getTarget().getInstrInfo()),
TRI(*vrm.getMachineFunction().getTarget().getRegisterInfo()),
Edit(0),
OpenIdx(0),
RegAssign(Allocator)
{}
void SplitEditor::reset(LiveRangeEdit &lre) {
Edit = &lre;
OpenIdx = 0;
RegAssign.clear();
Values.clear();
// We don't need to clear LiveOutCache, only LiveOutSeen entries are read.
LiveOutSeen.clear();
// We don't need an AliasAnalysis since we will only be performing
// cheap-as-a-copy remats anyway.
Edit->anyRematerializable(LIS, TII, 0);
}
void SplitEditor::dump() const {
if (RegAssign.empty()) {
dbgs() << " empty\n";
return;
}
for (RegAssignMap::const_iterator I = RegAssign.begin(); I.valid(); ++I)
dbgs() << " [" << I.start() << ';' << I.stop() << "):" << I.value();
dbgs() << '\n';
}
VNInfo *SplitEditor::defValue(unsigned RegIdx,
const VNInfo *ParentVNI,
SlotIndex Idx) {
assert(ParentVNI && "Mapping NULL value");
assert(Idx.isValid() && "Invalid SlotIndex");
assert(Edit->getParent().getVNInfoAt(Idx) == ParentVNI && "Bad Parent VNI");
LiveInterval *LI = Edit->get(RegIdx);
// Create a new value.
VNInfo *VNI = LI->getNextValue(Idx, 0, LIS.getVNInfoAllocator());
// Preserve the PHIDef bit.
if (ParentVNI->isPHIDef() && Idx == ParentVNI->def)
VNI->setIsPHIDef(true);
// Use insert for lookup, so we can add missing values with a second lookup.
std::pair<ValueMap::iterator, bool> InsP =
Values.insert(std::make_pair(std::make_pair(RegIdx, ParentVNI->id), VNI));
// This was the first time (RegIdx, ParentVNI) was mapped.
// Keep it as a simple def without any liveness.
if (InsP.second)
return VNI;
// If the previous value was a simple mapping, add liveness for it now.
if (VNInfo *OldVNI = InsP.first->second) {
SlotIndex Def = OldVNI->def;
LI->addRange(LiveRange(Def, Def.getNextSlot(), OldVNI));
// No longer a simple mapping.
InsP.first->second = 0;
}
// This is a complex mapping, add liveness for VNI
SlotIndex Def = VNI->def;
LI->addRange(LiveRange(Def, Def.getNextSlot(), VNI));
return VNI;
}
void SplitEditor::markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI) {
assert(ParentVNI && "Mapping NULL value");
VNInfo *&VNI = Values[std::make_pair(RegIdx, ParentVNI->id)];
// ParentVNI was either unmapped or already complex mapped. Either way.
if (!VNI)
return;
// This was previously a single mapping. Make sure the old def is represented
// by a trivial live range.
SlotIndex Def = VNI->def;
Edit->get(RegIdx)->addRange(LiveRange(Def, Def.getNextSlot(), VNI));
VNI = 0;
}
// extendRange - Extend the live range to reach Idx.
// Potentially create phi-def values.
void SplitEditor::extendRange(unsigned RegIdx, SlotIndex Idx) {
assert(Idx.isValid() && "Invalid SlotIndex");
MachineBasicBlock *IdxMBB = LIS.getMBBFromIndex(Idx);
assert(IdxMBB && "No MBB at Idx");
LiveInterval *LI = Edit->get(RegIdx);
// Is there a def in the same MBB we can extend?
if (LI->extendInBlock(LIS.getMBBStartIdx(IdxMBB), Idx))
return;
// Now for the fun part. We know that ParentVNI potentially has multiple defs,
// and we may need to create even more phi-defs to preserve VNInfo SSA form.
// Perform a search for all predecessor blocks where we know the dominating
// VNInfo. Insert phi-def VNInfos along the path back to IdxMBB.
// Initialize the live-out cache the first time it is needed.
if (LiveOutSeen.empty()) {
unsigned N = VRM.getMachineFunction().getNumBlockIDs();
LiveOutSeen.resize(N);
LiveOutCache.resize(N);
}
// Blocks where LI should be live-in.
SmallVector<MachineDomTreeNode*, 16> LiveIn;
LiveIn.push_back(MDT[IdxMBB]);
// Remember if we have seen more than one value.
bool UniqueVNI = true;
VNInfo *IdxVNI = 0;
// Using LiveOutCache as a visited set, perform a BFS for all reaching defs.
for (unsigned i = 0; i != LiveIn.size(); ++i) {
MachineBasicBlock *MBB = LiveIn[i]->getBlock();
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
MachineBasicBlock *Pred = *PI;
LiveOutPair &LOP = LiveOutCache[Pred];
// Is this a known live-out block?
if (LiveOutSeen.test(Pred->getNumber())) {
if (VNInfo *VNI = LOP.first) {
if (IdxVNI && IdxVNI != VNI)
UniqueVNI = false;
IdxVNI = VNI;
}
continue;
}
// First time. LOP is garbage and must be cleared below.
LiveOutSeen.set(Pred->getNumber());
// Does Pred provide a live-out value?
SlotIndex Start, Last;
tie(Start, Last) = LIS.getSlotIndexes()->getMBBRange(Pred);
Last = Last.getPrevSlot();
VNInfo *VNI = LI->extendInBlock(Start, Last);
LOP.first = VNI;
if (VNI) {
LOP.second = MDT[LIS.getMBBFromIndex(VNI->def)];
if (IdxVNI && IdxVNI != VNI)
UniqueVNI = false;
IdxVNI = VNI;
continue;
}
LOP.second = 0;
// No, we need a live-in value for Pred as well
if (Pred != IdxMBB)
LiveIn.push_back(MDT[Pred]);
else
UniqueVNI = false; // Loopback to IdxMBB, ask updateSSA() for help.
}
}
// We may need to add phi-def values to preserve the SSA form.
if (UniqueVNI) {
LiveOutPair LOP(IdxVNI, MDT[LIS.getMBBFromIndex(IdxVNI->def)]);
// Update LiveOutCache, but skip IdxMBB at LiveIn[0].
for (unsigned i = 1, e = LiveIn.size(); i != e; ++i)
LiveOutCache[LiveIn[i]->getBlock()] = LOP;
} else
IdxVNI = updateSSA(RegIdx, LiveIn, Idx, IdxMBB);
// Since we went through the trouble of a full BFS visiting all reaching defs,
// the values in LiveIn are now accurate. No more phi-defs are needed
// for these blocks, so we can color the live ranges.
for (unsigned i = 0, e = LiveIn.size(); i != e; ++i) {
MachineBasicBlock *MBB = LiveIn[i]->getBlock();
SlotIndex Start = LIS.getMBBStartIdx(MBB);
VNInfo *VNI = LiveOutCache[MBB].first;
// Anything in LiveIn other than IdxMBB is live-through.
// In IdxMBB, we should stop at Idx unless the same value is live-out.
if (MBB == IdxMBB && IdxVNI != VNI)
LI->addRange(LiveRange(Start, Idx.getNextSlot(), IdxVNI));
else
LI->addRange(LiveRange(Start, LIS.getMBBEndIdx(MBB), VNI));
}
}
VNInfo *SplitEditor::updateSSA(unsigned RegIdx,
SmallVectorImpl<MachineDomTreeNode*> &LiveIn,
SlotIndex Idx,
const MachineBasicBlock *IdxMBB) {
// This is essentially the same iterative algorithm that SSAUpdater uses,
// except we already have a dominator tree, so we don't have to recompute it.
LiveInterval *LI = Edit->get(RegIdx);
VNInfo *IdxVNI = 0;
unsigned Changes;
do {
Changes = 0;
// Propagate live-out values down the dominator tree, inserting phi-defs
// when necessary. Since LiveIn was created by a BFS, going backwards makes
// it more likely for us to visit immediate dominators before their
// children.
for (unsigned i = LiveIn.size(); i; --i) {
MachineDomTreeNode *Node = LiveIn[i-1];
MachineBasicBlock *MBB = Node->getBlock();
MachineDomTreeNode *IDom = Node->getIDom();
LiveOutPair IDomValue;
// We need a live-in value to a block with no immediate dominator?
// This is probably an unreachable block that has survived somehow.
bool needPHI = !IDom || !LiveOutSeen.test(IDom->getBlock()->getNumber());
// IDom dominates all of our predecessors, but it may not be the immediate
// dominator. Check if any of them have live-out values that are properly
// dominated by IDom. If so, we need a phi-def here.
if (!needPHI) {
IDomValue = LiveOutCache[IDom->getBlock()];
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
LiveOutPair Value = LiveOutCache[*PI];
if (!Value.first || Value.first == IDomValue.first)
continue;
// This predecessor is carrying something other than IDomValue.
// It could be because IDomValue hasn't propagated yet, or it could be
// because MBB is in the dominance frontier of that value.
if (MDT.dominates(IDom, Value.second)) {
needPHI = true;
break;
}
}
}
// Create a phi-def if required.
if (needPHI) {
++Changes;
SlotIndex Start = LIS.getMBBStartIdx(MBB);
VNInfo *VNI = LI->getNextValue(Start, 0, LIS.getVNInfoAllocator());
VNI->setIsPHIDef(true);
// We no longer need LI to be live-in.
LiveIn.erase(LiveIn.begin()+(i-1));
// Blocks in LiveIn are either IdxMBB, or have a value live-through.
if (MBB == IdxMBB)
IdxVNI = VNI;
// Check if we need to update live-out info.
LiveOutPair &LOP = LiveOutCache[MBB];
if (LOP.second == Node || !LiveOutSeen.test(MBB->getNumber())) {
// We already have a live-out defined in MBB, so this must be IdxMBB.
assert(MBB == IdxMBB && "Adding phi-def to known live-out");
LI->addRange(LiveRange(Start, Idx.getNextSlot(), VNI));
} else {
// This phi-def is also live-out, so color the whole block.
LI->addRange(LiveRange(Start, LIS.getMBBEndIdx(MBB), VNI));
LOP = LiveOutPair(VNI, Node);
}
} else if (IDomValue.first) {
// No phi-def here. Remember incoming value for IdxMBB.
if (MBB == IdxMBB) {
IdxVNI = IDomValue.first;
// IdxMBB need not be live-out.
if (!LiveOutSeen.test(MBB->getNumber()))
continue;
}
assert(LiveOutSeen.test(MBB->getNumber()) && "Expected live-out block");
// Propagate IDomValue if needed:
// MBB is live-out and doesn't define its own value.
LiveOutPair &LOP = LiveOutCache[MBB];
if (LOP.second != Node && LOP.first != IDomValue.first) {
++Changes;
LOP = IDomValue;
}
}
}
} while (Changes);
assert(IdxVNI && "Didn't find value for Idx");
return IdxVNI;
}
VNInfo *SplitEditor::defFromParent(unsigned RegIdx,
VNInfo *ParentVNI,
SlotIndex UseIdx,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) {
MachineInstr *CopyMI = 0;
SlotIndex Def;
LiveInterval *LI = Edit->get(RegIdx);
// Attempt cheap-as-a-copy rematerialization.
LiveRangeEdit::Remat RM(ParentVNI);
if (Edit->canRematerializeAt(RM, UseIdx, true, LIS)) {
Def = Edit->rematerializeAt(MBB, I, LI->reg, RM, LIS, TII, TRI);
} else {
// Can't remat, just insert a copy from parent.
CopyMI = BuildMI(MBB, I, DebugLoc(), TII.get(TargetOpcode::COPY), LI->reg)
.addReg(Edit->getReg());
Def = LIS.InsertMachineInstrInMaps(CopyMI).getDefIndex();
}
// Define the value in Reg.
VNInfo *VNI = defValue(RegIdx, ParentVNI, Def);
VNI->setCopy(CopyMI);
return VNI;
}
/// Create a new virtual register and live interval.
void SplitEditor::openIntv() {
assert(!OpenIdx && "Previous LI not closed before openIntv");
// Create the complement as index 0.
if (Edit->empty())
Edit->create(MRI, LIS, VRM);
// Create the open interval.
OpenIdx = Edit->size();
Edit->create(MRI, LIS, VRM);
}
SlotIndex SplitEditor::enterIntvBefore(SlotIndex Idx) {
assert(OpenIdx && "openIntv not called before enterIntvBefore");
DEBUG(dbgs() << " enterIntvBefore " << Idx);
Idx = Idx.getBaseIndex();
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Idx);
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return Idx;
}
DEBUG(dbgs() << ": valno " << ParentVNI->id << '\n');
MachineInstr *MI = LIS.getInstructionFromIndex(Idx);
assert(MI && "enterIntvBefore called with invalid index");
VNInfo *VNI = defFromParent(OpenIdx, ParentVNI, Idx, *MI->getParent(), MI);
return VNI->def;
}
SlotIndex SplitEditor::enterIntvAtEnd(MachineBasicBlock &MBB) {
assert(OpenIdx && "openIntv not called before enterIntvAtEnd");
SlotIndex End = LIS.getMBBEndIdx(&MBB);
SlotIndex Last = End.getPrevSlot();
DEBUG(dbgs() << " enterIntvAtEnd BB#" << MBB.getNumber() << ", " << Last);
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Last);
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return End;
}
DEBUG(dbgs() << ": valno " << ParentVNI->id);
VNInfo *VNI = defFromParent(OpenIdx, ParentVNI, Last, MBB,
LIS.getLastSplitPoint(Edit->getParent(), &MBB));
RegAssign.insert(VNI->def, End, OpenIdx);
DEBUG(dump());
return VNI->def;
}
/// useIntv - indicate that all instructions in MBB should use OpenLI.
void SplitEditor::useIntv(const MachineBasicBlock &MBB) {
useIntv(LIS.getMBBStartIdx(&MBB), LIS.getMBBEndIdx(&MBB));
}
void SplitEditor::useIntv(SlotIndex Start, SlotIndex End) {
assert(OpenIdx && "openIntv not called before useIntv");
DEBUG(dbgs() << " useIntv [" << Start << ';' << End << "):");
RegAssign.insert(Start, End, OpenIdx);
DEBUG(dump());
}
SlotIndex SplitEditor::leaveIntvAfter(SlotIndex Idx) {
assert(OpenIdx && "openIntv not called before leaveIntvAfter");
DEBUG(dbgs() << " leaveIntvAfter " << Idx);
// The interval must be live beyond the instruction at Idx.
Idx = Idx.getBoundaryIndex();
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Idx);
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return Idx.getNextSlot();
}
DEBUG(dbgs() << ": valno " << ParentVNI->id << '\n');
MachineInstr *MI = LIS.getInstructionFromIndex(Idx);
assert(MI && "No instruction at index");
VNInfo *VNI = defFromParent(0, ParentVNI, Idx, *MI->getParent(),
llvm::next(MachineBasicBlock::iterator(MI)));
return VNI->def;
}
SlotIndex SplitEditor::leaveIntvBefore(SlotIndex Idx) {
assert(OpenIdx && "openIntv not called before leaveIntvBefore");
DEBUG(dbgs() << " leaveIntvBefore " << Idx);
// The interval must be live into the instruction at Idx.
Idx = Idx.getBoundaryIndex();
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Idx);
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return Idx.getNextSlot();
}
DEBUG(dbgs() << ": valno " << ParentVNI->id << '\n');
MachineInstr *MI = LIS.getInstructionFromIndex(Idx);
assert(MI && "No instruction at index");
VNInfo *VNI = defFromParent(0, ParentVNI, Idx, *MI->getParent(), MI);
return VNI->def;
}
SlotIndex SplitEditor::leaveIntvAtTop(MachineBasicBlock &MBB) {
assert(OpenIdx && "openIntv not called before leaveIntvAtTop");
SlotIndex Start = LIS.getMBBStartIdx(&MBB);
DEBUG(dbgs() << " leaveIntvAtTop BB#" << MBB.getNumber() << ", " << Start);
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Start);
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return Start;
}
VNInfo *VNI = defFromParent(0, ParentVNI, Start, MBB,
MBB.SkipPHIsAndLabels(MBB.begin()));
RegAssign.insert(Start, VNI->def, OpenIdx);
DEBUG(dump());
return VNI->def;
}
void SplitEditor::overlapIntv(SlotIndex Start, SlotIndex End) {
assert(OpenIdx && "openIntv not called before overlapIntv");
const VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Start);
assert(ParentVNI == Edit->getParent().getVNInfoAt(End.getPrevSlot()) &&
"Parent changes value in extended range");
assert(LIS.getMBBFromIndex(Start) == LIS.getMBBFromIndex(End) &&
"Range cannot span basic blocks");
// The complement interval will be extended as needed by extendRange().
markComplexMapped(0, ParentVNI);
DEBUG(dbgs() << " overlapIntv [" << Start << ';' << End << "):");
RegAssign.insert(Start, End, OpenIdx);
DEBUG(dump());
}
/// closeIntv - Indicate that we are done editing the currently open
/// LiveInterval, and ranges can be trimmed.
void SplitEditor::closeIntv() {
assert(OpenIdx && "openIntv not called before closeIntv");
OpenIdx = 0;
}
/// transferSimpleValues - Transfer all simply defined values to the new live
/// ranges.
/// Values that were rematerialized or that have multiple defs are left alone.
bool SplitEditor::transferSimpleValues() {
bool Skipped = false;
RegAssignMap::const_iterator AssignI = RegAssign.begin();
for (LiveInterval::const_iterator ParentI = Edit->getParent().begin(),
ParentE = Edit->getParent().end(); ParentI != ParentE; ++ParentI) {
DEBUG(dbgs() << " blit " << *ParentI << ':');
VNInfo *ParentVNI = ParentI->valno;
// RegAssign has holes where RegIdx 0 should be used.
SlotIndex Start = ParentI->start;
AssignI.advanceTo(Start);
do {
unsigned RegIdx;
SlotIndex End = ParentI->end;
if (!AssignI.valid()) {
RegIdx = 0;
} else if (AssignI.start() <= Start) {
RegIdx = AssignI.value();
if (AssignI.stop() < End) {
End = AssignI.stop();
++AssignI;
}
} else {
RegIdx = 0;
End = std::min(End, AssignI.start());
}
DEBUG(dbgs() << " [" << Start << ';' << End << ")=" << RegIdx);
if (VNInfo *VNI = Values.lookup(std::make_pair(RegIdx, ParentVNI->id))) {
DEBUG(dbgs() << ':' << VNI->id);
Edit->get(RegIdx)->addRange(LiveRange(Start, End, VNI));
} else
Skipped = true;
Start = End;
} while (Start != ParentI->end);
DEBUG(dbgs() << '\n');
}
return Skipped;
}
void SplitEditor::extendPHIKillRanges() {
// Extend live ranges to be live-out for successor PHI values.
for (LiveInterval::const_vni_iterator I = Edit->getParent().vni_begin(),
E = Edit->getParent().vni_end(); I != E; ++I) {
const VNInfo *PHIVNI = *I;
if (PHIVNI->isUnused() || !PHIVNI->isPHIDef())
continue;
unsigned RegIdx = RegAssign.lookup(PHIVNI->def);
MachineBasicBlock *MBB = LIS.getMBBFromIndex(PHIVNI->def);
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
SlotIndex End = LIS.getMBBEndIdx(*PI).getPrevSlot();
// The predecessor may not have a live-out value. That is OK, like an
// undef PHI operand.
if (Edit->getParent().liveAt(End)) {
assert(RegAssign.lookup(End) == RegIdx &&
"Different register assignment in phi predecessor");
extendRange(RegIdx, End);
}
}
}
}
/// rewriteAssigned - Rewrite all uses of Edit->getReg().
void SplitEditor::rewriteAssigned(bool ExtendRanges) {
for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(Edit->getReg()),
RE = MRI.reg_end(); RI != RE;) {
MachineOperand &MO = RI.getOperand();
MachineInstr *MI = MO.getParent();
++RI;
// LiveDebugVariables should have handled all DBG_VALUE instructions.
if (MI->isDebugValue()) {
DEBUG(dbgs() << "Zapping " << *MI);
MO.setReg(0);
continue;
}
// <undef> operands don't really read the register, so just assign them to
// the complement.
if (MO.isUse() && MO.isUndef()) {
MO.setReg(Edit->get(0)->reg);
continue;
}
SlotIndex Idx = LIS.getInstructionIndex(MI);
Idx = MO.isUse() ? Idx.getUseIndex() : Idx.getDefIndex();
// Rewrite to the mapped register at Idx.
unsigned RegIdx = RegAssign.lookup(Idx);
MO.setReg(Edit->get(RegIdx)->reg);
DEBUG(dbgs() << " rewr BB#" << MI->getParent()->getNumber() << '\t'
<< Idx << ':' << RegIdx << '\t' << *MI);
// Extend liveness to Idx.
if (ExtendRanges)
extendRange(RegIdx, Idx);
}
}
/// rewriteSplit - Rewrite uses of Intvs[0] according to the ConEQ mapping.
void SplitEditor::rewriteComponents(const SmallVectorImpl<LiveInterval*> &Intvs,
const ConnectedVNInfoEqClasses &ConEq) {
for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(Intvs[0]->reg),
RE = MRI.reg_end(); RI != RE;) {
MachineOperand &MO = RI.getOperand();
MachineInstr *MI = MO.getParent();
++RI;
if (MO.isUse() && MO.isUndef())
continue;
// DBG_VALUE instructions should have been eliminated earlier.
SlotIndex Idx = LIS.getInstructionIndex(MI);
Idx = MO.isUse() ? Idx.getUseIndex() : Idx.getDefIndex();
DEBUG(dbgs() << " rewr BB#" << MI->getParent()->getNumber() << '\t'
<< Idx << ':');
const VNInfo *VNI = Intvs[0]->getVNInfoAt(Idx);
assert(VNI && "Interval not live at use.");
MO.setReg(Intvs[ConEq.getEqClass(VNI)]->reg);
DEBUG(dbgs() << VNI->id << '\t' << *MI);
}
}
void SplitEditor::deleteRematVictims() {
SmallVector<MachineInstr*, 8> Dead;
for (LiveInterval::const_vni_iterator I = Edit->getParent().vni_begin(),
E = Edit->getParent().vni_end(); I != E; ++I) {
const VNInfo *VNI = *I;
// Was VNI rematted anywhere?
if (VNI->isUnused() || VNI->isPHIDef() || !Edit->didRematerialize(VNI))
continue;
unsigned RegIdx = RegAssign.lookup(VNI->def);
LiveInterval *LI = Edit->get(RegIdx);
LiveInterval::const_iterator LII = LI->FindLiveRangeContaining(VNI->def);
assert(LII != LI->end() && "Missing live range for rematted def");
// Is this a dead def?
if (LII->end != VNI->def.getNextSlot())
continue;
MachineInstr *MI = LIS.getInstructionFromIndex(VNI->def);
assert(MI && "Missing instruction for dead def");
MI->addRegisterDead(LI->reg, &TRI);
if (!MI->allDefsAreDead())
continue;
DEBUG(dbgs() << "All defs dead: " << *MI);
Dead.push_back(MI);
}
if (Dead.empty())
return;
Edit->eliminateDeadDefs(Dead, LIS, TII);
}
void SplitEditor::finish() {
assert(OpenIdx == 0 && "Previous LI not closed before rewrite");
++NumFinished;
// At this point, the live intervals in Edit contain VNInfos corresponding to
// the inserted copies.
// Add the original defs from the parent interval.
for (LiveInterval::const_vni_iterator I = Edit->getParent().vni_begin(),
E = Edit->getParent().vni_end(); I != E; ++I) {
const VNInfo *ParentVNI = *I;
if (ParentVNI->isUnused())
continue;
unsigned RegIdx = RegAssign.lookup(ParentVNI->def);
defValue(RegIdx, ParentVNI, ParentVNI->def);
// Mark rematted values as complex everywhere to force liveness computation.
// The new live ranges may be truncated.
if (Edit->didRematerialize(ParentVNI))
for (unsigned i = 0, e = Edit->size(); i != e; ++i)
markComplexMapped(i, ParentVNI);
}
#ifndef NDEBUG
// Every new interval must have a def by now, otherwise the split is bogus.
for (LiveRangeEdit::iterator I = Edit->begin(), E = Edit->end(); I != E; ++I)
assert((*I)->hasAtLeastOneValue() && "Split interval has no value");
#endif
// Transfer the simply mapped values, check if any are complex.
bool Complex = transferSimpleValues();
if (Complex)
extendPHIKillRanges();
else
++NumSimple;
// Rewrite virtual registers, possibly extending ranges.
rewriteAssigned(Complex);
// Delete defs that were rematted everywhere.
if (Complex)
deleteRematVictims();
// Get rid of unused values and set phi-kill flags.
for (LiveRangeEdit::iterator I = Edit->begin(), E = Edit->end(); I != E; ++I)
(*I)->RenumberValues(LIS);
// Now check if any registers were separated into multiple components.
ConnectedVNInfoEqClasses ConEQ(LIS);
for (unsigned i = 0, e = Edit->size(); i != e; ++i) {
// Don't use iterators, they are invalidated by create() below.
LiveInterval *li = Edit->get(i);
unsigned NumComp = ConEQ.Classify(li);
if (NumComp <= 1)
continue;
DEBUG(dbgs() << " " << NumComp << " components: " << *li << '\n');
SmallVector<LiveInterval*, 8> dups;
dups.push_back(li);
for (unsigned i = 1; i != NumComp; ++i)
dups.push_back(&Edit->create(MRI, LIS, VRM));
rewriteComponents(dups, ConEQ);
ConEQ.Distribute(&dups[0]);
}
// Calculate spill weight and allocation hints for new intervals.
VirtRegAuxInfo vrai(VRM.getMachineFunction(), LIS, SA.Loops);
for (LiveRangeEdit::iterator I = Edit->begin(), E = Edit->end(); I != E; ++I){
LiveInterval &li = **I;
vrai.CalculateRegClass(li.reg);
vrai.CalculateWeightAndHint(li);
DEBUG(dbgs() << " new interval " << MRI.getRegClass(li.reg)->getName()
<< ":" << li << '\n');
}
}
//===----------------------------------------------------------------------===//
// Single Block Splitting
//===----------------------------------------------------------------------===//
/// getMultiUseBlocks - if CurLI has more than one use in a basic block, it
/// may be an advantage to split CurLI for the duration of the block.
bool SplitAnalysis::getMultiUseBlocks(BlockPtrSet &Blocks) {
// If CurLI is local to one block, there is no point to splitting it.
if (LiveBlocks.size() <= 1)
return false;
// Add blocks with multiple uses.
for (unsigned i = 0, e = LiveBlocks.size(); i != e; ++i) {
const BlockInfo &BI = LiveBlocks[i];
if (!BI.Uses)
continue;
unsigned Instrs = UsingBlocks.lookup(BI.MBB);
if (Instrs <= 1)
continue;
if (Instrs == 2 && BI.LiveIn && BI.LiveOut && !BI.LiveThrough)
continue;
Blocks.insert(BI.MBB);
}
return !Blocks.empty();
}
/// splitSingleBlocks - Split CurLI into a separate live interval inside each
/// basic block in Blocks.
void SplitEditor::splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks) {
DEBUG(dbgs() << " splitSingleBlocks for " << Blocks.size() << " blocks.\n");
for (unsigned i = 0, e = SA.LiveBlocks.size(); i != e; ++i) {
const SplitAnalysis::BlockInfo &BI = SA.LiveBlocks[i];
if (!BI.Uses || !Blocks.count(BI.MBB))
continue;
openIntv();
SlotIndex SegStart = enterIntvBefore(BI.FirstUse);
if (!BI.LiveOut || BI.LastUse < BI.LastSplitPoint) {
useIntv(SegStart, leaveIntvAfter(BI.LastUse));
} else {
// The last use is after the last valid split point.
SlotIndex SegStop = leaveIntvBefore(BI.LastSplitPoint);
useIntv(SegStart, SegStop);
overlapIntv(SegStop, BI.LastUse);
}
closeIntv();
}
finish();
}
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