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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 "splitter"
#include "SplitKit.h"
#include "VirtRegMap.h"
#include "llvm/CodeGen/CalcSpillWeights.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.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"));
//===----------------------------------------------------------------------===//
// Split Analysis
//===----------------------------------------------------------------------===//
SplitAnalysis::SplitAnalysis(const MachineFunction &mf,
const LiveIntervals &lis,
const MachineLoopInfo &mli)
: mf_(mf),
lis_(lis),
loops_(mli),
tii_(*mf.getTarget().getInstrInfo()),
curli_(0) {}
void SplitAnalysis::clear() {
usingInstrs_.clear();
usingBlocks_.clear();
usingLoops_.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);
MachineInstr *MI = I.skipInstruction();) {
if (MI->isDebugValue() || !usingInstrs_.insert(MI))
continue;
MachineBasicBlock *MBB = MI->getParent();
if (usingBlocks_[MBB]++)
continue;
for (MachineLoop *Loop = loops_.getLoopFor(MBB); Loop;
Loop = Loop->getParentLoop())
usingLoops_[Loop]++;
}
DEBUG(dbgs() << " counted "
<< usingInstrs_.size() << " instrs, "
<< usingBlocks_.size() << " blocks, "
<< usingLoops_.size() << " loops.\n");
}
// Get three sets of basic blocks surrounding a loop: Blocks inside the loop,
// predecessor blocks, and exit blocks.
void SplitAnalysis::getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks) {
Blocks.clear();
// Blocks in the loop.
Blocks.Loop.insert(Loop->block_begin(), Loop->block_end());
// Predecessor blocks.
const MachineBasicBlock *Header = Loop->getHeader();
for (MachineBasicBlock::const_pred_iterator I = Header->pred_begin(),
E = Header->pred_end(); I != E; ++I)
if (!Blocks.Loop.count(*I))
Blocks.Preds.insert(*I);
// Exit blocks.
for (MachineLoop::block_iterator I = Loop->block_begin(),
E = Loop->block_end(); I != E; ++I) {
const MachineBasicBlock *MBB = *I;
for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end(); SI != SE; ++SI)
if (!Blocks.Loop.count(*SI))
Blocks.Exits.insert(*SI);
}
}
/// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in
/// and around the Loop.
SplitAnalysis::LoopPeripheralUse SplitAnalysis::
analyzeLoopPeripheralUse(const SplitAnalysis::LoopBlocks &Blocks) {
LoopPeripheralUse use = ContainedInLoop;
for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end();
I != E; ++I) {
const MachineBasicBlock *MBB = I->first;
// Is this a peripheral block?
if (use < MultiPeripheral &&
(Blocks.Preds.count(MBB) || Blocks.Exits.count(MBB))) {
if (I->second > 1) use = MultiPeripheral;
else use = SinglePeripheral;
continue;
}
// Is it a loop block?
if (Blocks.Loop.count(MBB))
continue;
// It must be an unrelated block.
return OutsideLoop;
}
return use;
}
/// getCriticalExits - It may be necessary to partially break critical edges
/// leaving the loop if an exit block has phi uses of curli. Collect the exit
/// blocks that need special treatment into CriticalExits.
void SplitAnalysis::getCriticalExits(const SplitAnalysis::LoopBlocks &Blocks,
BlockPtrSet &CriticalExits) {
CriticalExits.clear();
// A critical exit block contains a phi def of curli, and has a predecessor
// that is not in the loop nor a loop predecessor.
// For such an exit block, the edges carrying the new variable must be moved
// to a new pre-exit block.
for (BlockPtrSet::iterator I = Blocks.Exits.begin(), E = Blocks.Exits.end();
I != E; ++I) {
const MachineBasicBlock *Succ = *I;
SlotIndex SuccIdx = lis_.getMBBStartIdx(Succ);
VNInfo *SuccVNI = curli_->getVNInfoAt(SuccIdx);
// This exit may not have curli live in at all. No need to split.
if (!SuccVNI)
continue;
// If this is not a PHI def, it is either using a value from before the
// loop, or a value defined inside the loop. Both are safe.
if (!SuccVNI->isPHIDef() || SuccVNI->def.getBaseIndex() != SuccIdx)
continue;
// This exit block does have a PHI. Does it also have a predecessor that is
// not a loop block or loop predecessor?
for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(),
PE = Succ->pred_end(); PI != PE; ++PI) {
const MachineBasicBlock *Pred = *PI;
if (Blocks.Loop.count(Pred) || Blocks.Preds.count(Pred))
continue;
// This is a critical exit block, and we need to split the exit edge.
CriticalExits.insert(Succ);
break;
}
}
}
/// canSplitCriticalExits - Return true if it is possible to insert new exit
/// blocks before the blocks in CriticalExits.
bool
SplitAnalysis::canSplitCriticalExits(const SplitAnalysis::LoopBlocks &Blocks,
BlockPtrSet &CriticalExits) {
// If we don't allow critical edge splitting, require no critical exits.
if (!AllowSplit)
return CriticalExits.empty();
for (BlockPtrSet::iterator I = CriticalExits.begin(), E = CriticalExits.end();
I != E; ++I) {
const MachineBasicBlock *Succ = *I;
// We want to insert a new pre-exit MBB before Succ, and change all the
// in-loop blocks to branch to the pre-exit instead of Succ.
// Check that all the in-loop predecessors can be changed.
for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(),
PE = Succ->pred_end(); PI != PE; ++PI) {
const MachineBasicBlock *Pred = *PI;
// The external predecessors won't be altered.
if (!Blocks.Loop.count(Pred) && !Blocks.Preds.count(Pred))
continue;
if (!canAnalyzeBranch(Pred))
return false;
}
// If Succ's layout predecessor falls through, that too must be analyzable.
// We need to insert the pre-exit block in the gap.
MachineFunction::const_iterator MFI = Succ;
if (MFI == mf_.begin())
continue;
if (!canAnalyzeBranch(--MFI))
return false;
}
// No problems found.
return true;
}
void SplitAnalysis::analyze(const LiveInterval *li) {
clear();
curli_ = li;
analyzeUses();
}
const MachineLoop *SplitAnalysis::getBestSplitLoop() {
assert(curli_ && "Call analyze() before getBestSplitLoop");
if (usingLoops_.empty())
return 0;
LoopPtrSet Loops, SecondLoops;
LoopBlocks Blocks;
BlockPtrSet CriticalExits;
// Find first-class and second class candidate loops.
// We prefer to split around loops where curli is used outside the periphery.
for (LoopCountMap::const_iterator I = usingLoops_.begin(),
E = usingLoops_.end(); I != E; ++I) {
const MachineLoop *Loop = I->first;
getLoopBlocks(Loop, Blocks);
LoopPtrSet *LPS = 0;
switch(analyzeLoopPeripheralUse(Blocks)) {
case OutsideLoop:
LPS = &Loops;
break;
case MultiPeripheral:
LPS = &SecondLoops;
break;
case ContainedInLoop:
DEBUG(dbgs() << " contained in " << *Loop);
continue;
case SinglePeripheral:
DEBUG(dbgs() << " single peripheral use in " << *Loop);
continue;
}
// Will it be possible to split around this loop?
getCriticalExits(Blocks, CriticalExits);
DEBUG(dbgs() << " " << CriticalExits.size() << " critical exits from "
<< *Loop);
if (!canSplitCriticalExits(Blocks, CriticalExits))
continue;
// This is a possible split.
assert(LPS);
LPS->insert(Loop);
}
DEBUG(dbgs() << " getBestSplitLoop found " << Loops.size() << " + "
<< SecondLoops.size() << " candidate loops.\n");
// If there are no first class loops available, look at second class loops.
if (Loops.empty())
Loops = SecondLoops;
if (Loops.empty())
return 0;
// Pick the earliest loop.
// FIXME: Are there other heuristics to consider?
const MachineLoop *Best = 0;
SlotIndex BestIdx;
for (LoopPtrSet::const_iterator I = Loops.begin(), E = Loops.end(); I != E;
++I) {
SlotIndex Idx = lis_.getMBBStartIdx((*I)->getHeader());
if (!Best || Idx < BestIdx)
Best = *I, BestIdx = Idx;
}
DEBUG(dbgs() << " getBestSplitLoop found " << *Best);
return Best;
}
/// 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 (usingBlocks_.size() <= 1)
return false;
// Add blocks with multiple uses.
for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end();
I != E; ++I)
switch (I->second) {
case 0:
case 1:
continue;
case 2: {
// It doesn't pay to split a 2-instr block if it redefines curli.
VNInfo *VN1 = curli_->getVNInfoAt(lis_.getMBBStartIdx(I->first));
VNInfo *VN2 =
curli_->getVNInfoAt(lis_.getMBBEndIdx(I->first).getPrevIndex());
// live-in and live-out with a different value.
if (VN1 && VN2 && VN1 != VN2)
continue;
} // Fall through.
default:
Blocks.insert(I->first);
}
return !Blocks.empty();
}
//===----------------------------------------------------------------------===//
// LiveIntervalMap
//===----------------------------------------------------------------------===//
// Work around the fact that the std::pair constructors are broken for pointer
// pairs in some implementations. makeVV(x, 0) works.
static inline std::pair<const VNInfo*, VNInfo*>
makeVV(const VNInfo *a, VNInfo *b) {
return std::make_pair(a, b);
}
void LiveIntervalMap::reset(LiveInterval *li) {
li_ = li;
valueMap_.clear();
}
bool LiveIntervalMap::isComplexMapped(const VNInfo *ParentVNI) const {
ValueMap::const_iterator i = valueMap_.find(ParentVNI);
return i != valueMap_.end() && i->second == 0;
}
// defValue - Introduce a li_ def for ParentVNI that could be later than
// ParentVNI->def.
VNInfo *LiveIntervalMap::defValue(const VNInfo *ParentVNI, SlotIndex Idx) {
assert(li_ && "call reset first");
assert(ParentVNI && "Mapping NULL value");
assert(Idx.isValid() && "Invalid SlotIndex");
assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI");
// Create a new value.
VNInfo *VNI = li_->getNextValue(Idx, 0, lis_.getVNInfoAllocator());
// Use insert for lookup, so we can add missing values with a second lookup.
std::pair<ValueMap::iterator,bool> InsP =
valueMap_.insert(makeVV(ParentVNI, Idx == ParentVNI->def ? VNI : 0));
// This is now a complex def. Mark with a NULL in valueMap.
if (!InsP.second)
InsP.first->second = 0;
return VNI;
}
// mapValue - Find the mapped value for ParentVNI at Idx.
// Potentially create phi-def values.
VNInfo *LiveIntervalMap::mapValue(const VNInfo *ParentVNI, SlotIndex Idx,
bool *simple) {
assert(li_ && "call reset first");
assert(ParentVNI && "Mapping NULL value");
assert(Idx.isValid() && "Invalid SlotIndex");
assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI");
// Use insert for lookup, so we can add missing values with a second lookup.
std::pair<ValueMap::iterator,bool> InsP =
valueMap_.insert(makeVV(ParentVNI, 0));
// This was an unknown value. Create a simple mapping.
if (InsP.second) {
if (simple) *simple = true;
return InsP.first->second = li_->createValueCopy(ParentVNI,
lis_.getVNInfoAllocator());
}
// This was a simple mapped value.
if (InsP.first->second) {
if (simple) *simple = true;
return InsP.first->second;
}
// This is a complex mapped value. There may be multiple defs, and we may need
// to create phi-defs.
if (simple) *simple = false;
MachineBasicBlock *IdxMBB = lis_.getMBBFromIndex(Idx);
assert(IdxMBB && "No MBB at Idx");
// Is there a def in the same MBB we can extend?
if (VNInfo *VNI = extendTo(IdxMBB, Idx))
return VNI;
// 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 depth-first search for predecessor blocks where we know the
// dominating VNInfo. Insert phi-def VNInfos along the path back to IdxMBB.
// Track MBBs where we have created or learned the dominating value.
// This may change during the DFS as we create new phi-defs.
typedef DenseMap<MachineBasicBlock*, VNInfo*> MBBValueMap;
MBBValueMap DomValue;
typedef SplitAnalysis::BlockPtrSet BlockPtrSet;
BlockPtrSet Visited;
// Iterate over IdxMBB predecessors in a depth-first order.
// Skip begin() since that is always IdxMBB.
for (idf_ext_iterator<MachineBasicBlock*, BlockPtrSet>
IDFI = llvm::next(idf_ext_begin(IdxMBB, Visited)),
IDFE = idf_ext_end(IdxMBB, Visited); IDFI != IDFE;) {
MachineBasicBlock *MBB = *IDFI;
SlotIndex End = lis_.getMBBEndIdx(MBB).getPrevSlot();
// We are operating on the restricted CFG where ParentVNI is live.
if (parentli_.getVNInfoAt(End) != ParentVNI) {
IDFI.skipChildren();
continue;
}
// Do we have a dominating value in this block?
VNInfo *VNI = extendTo(MBB, End);
if (!VNI) {
++IDFI;
continue;
}
// Yes, VNI dominates MBB. Make sure we visit MBB again from other paths.
Visited.erase(MBB);
// Track the path back to IdxMBB, creating phi-defs
// as needed along the way.
for (unsigned PI = IDFI.getPathLength()-1; PI != 0; --PI) {
// Start from MBB's immediate successor. End at IdxMBB.
MachineBasicBlock *Succ = IDFI.getPath(PI-1);
std::pair<MBBValueMap::iterator, bool> InsP =
DomValue.insert(MBBValueMap::value_type(Succ, VNI));
// This is the first time we backtrack to Succ.
if (InsP.second)
continue;
// We reached Succ again with the same VNI. Nothing is going to change.
VNInfo *OVNI = InsP.first->second;
if (OVNI == VNI)
break;
// Succ already has a phi-def. No need to continue.
SlotIndex Start = lis_.getMBBStartIdx(Succ);
if (OVNI->def == Start)
break;
// We have a collision between the old and new VNI at Succ. That means
// neither dominates and we need a new phi-def.
VNI = li_->getNextValue(Start, 0, lis_.getVNInfoAllocator());
VNI->setIsPHIDef(true);
InsP.first->second = VNI;
// Replace OVNI with VNI in the remaining path.
for (; PI > 1 ; --PI) {
MBBValueMap::iterator I = DomValue.find(IDFI.getPath(PI-2));
if (I == DomValue.end() || I->second != OVNI)
break;
I->second = VNI;
}
}
// No need to search the children, we found a dominating value.
IDFI.skipChildren();
}
// The search should at least find a dominating value for IdxMBB.
assert(!DomValue.empty() && "Couldn't find a reaching definition");
// Since we went through the trouble of a full DFS visiting all reaching defs,
// the values in DomValue are now accurate. No more phi-defs are needed for
// these blocks, so we can color the live ranges.
// This makes the next mapValue call much faster.
VNInfo *IdxVNI = 0;
for (MBBValueMap::iterator I = DomValue.begin(), E = DomValue.end(); I != E;
++I) {
MachineBasicBlock *MBB = I->first;
VNInfo *VNI = I->second;
SlotIndex Start = lis_.getMBBStartIdx(MBB);
if (MBB == IdxMBB) {
// Don't add full liveness to IdxMBB, stop at Idx.
if (Start != Idx)
li_->addRange(LiveRange(Start, Idx.getNextSlot(), VNI));
// The caller had better add some liveness to IdxVNI, or it leaks.
IdxVNI = VNI;
} else
li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI));
}
assert(IdxVNI && "Didn't find value for Idx");
return IdxVNI;
}
// extendTo - Find the last li_ value defined in MBB at or before Idx. The
// parentli_ is assumed to be live at Idx. Extend the live range to Idx.
// Return the found VNInfo, or NULL.
VNInfo *LiveIntervalMap::extendTo(MachineBasicBlock *MBB, SlotIndex Idx) {
assert(li_ && "call reset first");
LiveInterval::iterator I = std::upper_bound(li_->begin(), li_->end(), Idx);
if (I == li_->begin())
return 0;
--I;
if (I->end <= lis_.getMBBStartIdx(MBB))
return 0;
if (I->end <= Idx)
I->end = Idx.getNextSlot();
return I->valno;
}
// addSimpleRange - Add a simple range from parentli_ to li_.
// ParentVNI must be live in the [Start;End) interval.
void LiveIntervalMap::addSimpleRange(SlotIndex Start, SlotIndex End,
const VNInfo *ParentVNI) {
assert(li_ && "call reset first");
bool simple;
VNInfo *VNI = mapValue(ParentVNI, Start, &simple);
// A simple mapping is easy.
if (simple) {
li_->addRange(LiveRange(Start, End, VNI));
return;
}
// ParentVNI is a complex value. We must map per MBB.
MachineFunction::iterator MBB = lis_.getMBBFromIndex(Start);
MachineFunction::iterator MBBE = lis_.getMBBFromIndex(End.getPrevSlot());
if (MBB == MBBE) {
li_->addRange(LiveRange(Start, End, VNI));
return;
}
// First block.
li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI));
// Run sequence of full blocks.
for (++MBB; MBB != MBBE; ++MBB) {
Start = lis_.getMBBStartIdx(MBB);
li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB),
mapValue(ParentVNI, Start)));
}
// Final block.
Start = lis_.getMBBStartIdx(MBB);
if (Start != End)
li_->addRange(LiveRange(Start, End, mapValue(ParentVNI, Start)));
}
/// addRange - Add live ranges to li_ where [Start;End) intersects parentli_.
/// All needed values whose def is not inside [Start;End) must be defined
/// beforehand so mapValue will work.
void LiveIntervalMap::addRange(SlotIndex Start, SlotIndex End) {
assert(li_ && "call reset first");
LiveInterval::const_iterator B = parentli_.begin(), E = parentli_.end();
LiveInterval::const_iterator I = std::lower_bound(B, E, Start);
// Check if --I begins before Start and overlaps.
if (I != B) {
--I;
if (I->end > Start)
addSimpleRange(Start, std::min(End, I->end), I->valno);
++I;
}
// The remaining ranges begin after Start.
for (;I != E && I->start < End; ++I)
addSimpleRange(I->start, std::min(End, I->end), I->valno);
}
VNInfo *LiveIntervalMap::defByCopyFrom(unsigned Reg,
const VNInfo *ParentVNI,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) {
const TargetInstrDesc &TID = MBB.getParent()->getTarget().getInstrInfo()->
get(TargetOpcode::COPY);
MachineInstr *MI = BuildMI(MBB, I, DebugLoc(), TID, li_->reg).addReg(Reg);
SlotIndex DefIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
VNInfo *VNI = defValue(ParentVNI, DefIdx);
VNI->setCopy(MI);
li_->addRange(LiveRange(DefIdx, DefIdx.getNextSlot(), VNI));
return VNI;
}
//===----------------------------------------------------------------------===//
// Split Editor
//===----------------------------------------------------------------------===//
/// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
SplitEditor::SplitEditor(SplitAnalysis &sa, LiveIntervals &lis, VirtRegMap &vrm,
SmallVectorImpl<LiveInterval*> &intervals)
: sa_(sa), lis_(lis), vrm_(vrm),
mri_(vrm.getMachineFunction().getRegInfo()),
tii_(*vrm.getMachineFunction().getTarget().getInstrInfo()),
curli_(sa_.getCurLI()),
dupli_(lis_, *curli_),
openli_(lis_, *curli_),
intervals_(intervals),
firstInterval(intervals_.size())
{
assert(curli_ && "SplitEditor created from empty SplitAnalysis");
// Make sure curli_ is assigned a stack slot, so all our intervals get the
// same slot as curli_.
if (vrm_.getStackSlot(curli_->reg) == VirtRegMap::NO_STACK_SLOT)
vrm_.assignVirt2StackSlot(curli_->reg);
}
LiveInterval *SplitEditor::createInterval() {
unsigned Reg = mri_.createVirtualRegister(mri_.getRegClass(curli_->reg));
LiveInterval &Intv = lis_.getOrCreateInterval(Reg);
vrm_.grow();
vrm_.assignVirt2StackSlot(Reg, vrm_.getStackSlot(curli_->reg));
return &Intv;
}
bool SplitEditor::intervalsLiveAt(SlotIndex Idx) const {
for (int i = firstInterval, e = intervals_.size(); i != e; ++i)
if (intervals_[i]->liveAt(Idx))
return true;
return false;
}
/// Create a new virtual register and live interval.
void SplitEditor::openIntv() {
assert(!openli_.getLI() && "Previous LI not closed before openIntv");
if (!dupli_.getLI())
dupli_.reset(createInterval());
openli_.reset(createInterval());
intervals_.push_back(openli_.getLI());
}
/// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
/// not live before Idx, a COPY is not inserted.
void SplitEditor::enterIntvBefore(SlotIndex Idx) {
assert(openli_.getLI() && "openIntv not called before enterIntvBefore");
DEBUG(dbgs() << " enterIntvBefore " << Idx);
VNInfo *ParentVNI = curli_->getVNInfoAt(Idx.getUseIndex());
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return;
}
DEBUG(dbgs() << ": valno " << ParentVNI->id);
truncatedValues.insert(ParentVNI);
MachineInstr *MI = lis_.getInstructionFromIndex(Idx);
assert(MI && "enterIntvBefore called with invalid index");
VNInfo *VNI = openli_.defByCopyFrom(curli_->reg, ParentVNI,
*MI->getParent(), MI);
openli_.getLI()->addRange(LiveRange(VNI->def, Idx.getDefIndex(), VNI));
DEBUG(dbgs() << ": " << *openli_.getLI() << '\n');
}
/// enterIntvAtEnd - Enter openli at the end of MBB.
void SplitEditor::enterIntvAtEnd(MachineBasicBlock &MBB) {
assert(openli_.getLI() && "openIntv not called before enterIntvAtEnd");
SlotIndex End = lis_.getMBBEndIdx(&MBB);
DEBUG(dbgs() << " enterIntvAtEnd BB#" << MBB.getNumber() << ", " << End);
VNInfo *ParentVNI = curli_->getVNInfoAt(End.getPrevSlot());
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return;
}
DEBUG(dbgs() << ": valno " << ParentVNI->id);
truncatedValues.insert(ParentVNI);
VNInfo *VNI = openli_.defByCopyFrom(curli_->reg, ParentVNI,
MBB, MBB.getFirstTerminator());
// Make sure openli is live out of MBB.
openli_.getLI()->addRange(LiveRange(VNI->def, End, VNI));
DEBUG(dbgs() << ": " << *openli_.getLI() << '\n');
}
/// 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(openli_.getLI() && "openIntv not called before useIntv");
openli_.addRange(Start, End);
DEBUG(dbgs() << " use [" << Start << ';' << End << "): "
<< *openli_.getLI() << '\n');
}
/// leaveIntvAfter - Leave openli after the instruction at Idx.
void SplitEditor::leaveIntvAfter(SlotIndex Idx) {
assert(openli_.getLI() && "openIntv not called before leaveIntvAfter");
DEBUG(dbgs() << " leaveIntvAfter " << Idx);
// The interval must be live beyond the instruction at Idx.
VNInfo *ParentVNI = curli_->getVNInfoAt(Idx.getBoundaryIndex());
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return;
}
DEBUG(dbgs() << ": valno " << ParentVNI->id);
MachineBasicBlock::iterator MII = lis_.getInstructionFromIndex(Idx);
MachineBasicBlock *MBB = MII->getParent();
VNInfo *VNI = dupli_.defByCopyFrom(openli_.getLI()->reg, ParentVNI, *MBB,
llvm::next(MII));
// Finally we must make sure that openli is properly extended from Idx to the
// new copy.
openli_.addSimpleRange(Idx.getBoundaryIndex(), VNI->def, ParentVNI);
DEBUG(dbgs() << ": " << *openli_.getLI() << '\n');
}
/// leaveIntvAtTop - Leave the interval at the top of MBB.
/// Currently, only one value can leave the interval.
void SplitEditor::leaveIntvAtTop(MachineBasicBlock &MBB) {
assert(openli_.getLI() && "openIntv not called before leaveIntvAtTop");
SlotIndex Start = lis_.getMBBStartIdx(&MBB);
DEBUG(dbgs() << " leaveIntvAtTop BB#" << MBB.getNumber() << ", " << Start);
VNInfo *ParentVNI = curli_->getVNInfoAt(Start);
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return;
}
// We are going to insert a back copy, so we must have a dupli_.
VNInfo *VNI = dupli_.defByCopyFrom(openli_.getLI()->reg, ParentVNI,
MBB, MBB.begin());
// Finally we must make sure that openli is properly extended from Start to
// the new copy.
openli_.addSimpleRange(Start, VNI->def, ParentVNI);
DEBUG(dbgs() << ": " << *openli_.getLI() << '\n');
}
/// closeIntv - Indicate that we are done editing the currently open
/// LiveInterval, and ranges can be trimmed.
void SplitEditor::closeIntv() {
assert(openli_.getLI() && "openIntv not called before closeIntv");
DEBUG(dbgs() << " closeIntv cleaning up\n");
DEBUG(dbgs() << " open " << *openli_.getLI() << '\n');
openli_.reset(0);
}
void
SplitEditor::addTruncSimpleRange(SlotIndex Start, SlotIndex End, VNInfo *VNI) {
// Build vector of iterator pairs from the intervals.
typedef std::pair<LiveInterval::const_iterator,
LiveInterval::const_iterator> IIPair;
SmallVector<IIPair, 8> Iters;
for (int i = firstInterval, e = intervals_.size(); i != e; ++i) {
LiveInterval::const_iterator I = intervals_[i]->find(Start);
LiveInterval::const_iterator E = intervals_[i]->end();
if (I != E)
Iters.push_back(std::make_pair(I, E));
}
SlotIndex sidx = Start;
// Break [Start;End) into segments that don't overlap any intervals.
for (;;) {
SlotIndex next = sidx, eidx = End;
// Find overlapping intervals.
for (unsigned i = 0; i != Iters.size() && sidx < eidx; ++i) {
LiveInterval::const_iterator I = Iters[i].first;
// Interval I is overlapping [sidx;eidx). Trim sidx.
if (I->start <= sidx) {
sidx = I->end;
// Move to the next run, remove iters when all are consumed.
I = ++Iters[i].first;
if (I == Iters[i].second) {
Iters.erase(Iters.begin() + i);
--i;
continue;
}
}
// Trim eidx too if needed.
if (I->start >= eidx)
continue;
eidx = I->start;
next = I->end;
}
// Now, [sidx;eidx) doesn't overlap anything in intervals_.
if (sidx < eidx)
dupli_.addSimpleRange(sidx, eidx, VNI);
// If the interval end was truncated, we can try again from next.
if (next <= sidx)
break;
sidx = next;
}
}
/// rewrite - after all the new live ranges have been created, rewrite
/// instructions using curli to use the new intervals.
void SplitEditor::rewrite() {
assert(!openli_.getLI() && "Previous LI not closed before rewrite");
assert(dupli_.getLI() && "No dupli for rewrite. Noop spilt?");
// First we need to fill in the live ranges in dupli.
// If values were redefined, we need a full recoloring with SSA update.
// If values were truncated, we only need to truncate the ranges.
// If values were partially rematted, we should shrink to uses.
// If values were fully rematted, they should be omitted.
// FIXME: If a single value is redefined, just move the def and truncate.
// Values that are fully contained in the split intervals.
SmallPtrSet<const VNInfo*, 8> deadValues;
// Map all curli values that should have live defs in dupli.
for (LiveInterval::const_vni_iterator I = curli_->vni_begin(),
E = curli_->vni_end(); I != E; ++I) {
const VNInfo *VNI = *I;
// Original def is contained in the split intervals.
if (intervalsLiveAt(VNI->def)) {
// Did this value escape?
if (dupli_.isMapped(VNI))
truncatedValues.insert(VNI);
else
deadValues.insert(VNI);
continue;
}
// Add minimal live range at the definition.
VNInfo *DVNI = dupli_.defValue(VNI, VNI->def);
dupli_.getLI()->addRange(LiveRange(VNI->def, VNI->def.getNextSlot(), DVNI));
}
// Add all ranges to dupli.
for (LiveInterval::const_iterator I = curli_->begin(), E = curli_->end();
I != E; ++I) {
const LiveRange &LR = *I;
if (truncatedValues.count(LR.valno)) {
// recolor after removing intervals_.
addTruncSimpleRange(LR.start, LR.end, LR.valno);
} else if (!deadValues.count(LR.valno)) {
// recolor without truncation.
dupli_.addSimpleRange(LR.start, LR.end, LR.valno);
}
}
// Get rid of unused values and set phi-kill flags.
dupli_.getLI()->RenumberValues(lis_);
// Now check if dupli was separated into multiple connected components.
ConnectedVNInfoEqClasses ConEQ(lis_);
if (unsigned NumComp = ConEQ.Classify(dupli_.getLI())) {
DEBUG(dbgs() << " Remainder has " << NumComp << " connected components: "
<< *dupli_.getLI() << '\n');
unsigned firstComp = intervals_.size();
intervals_.push_back(dupli_.getLI());
// Did the remainder break up? Create intervals for all the components.
if (NumComp > 1) {
for (unsigned i = 1; i != NumComp; ++i)
intervals_.push_back(createInterval());
ConEQ.Distribute(&intervals_[firstComp]);
}
} else {
DEBUG(dbgs() << " dupli became empty?\n");
lis_.removeInterval(dupli_.getLI()->reg);
dupli_.reset(0);
}
// Rewrite instructions.
const LiveInterval *curli = sa_.getCurLI();
for (MachineRegisterInfo::reg_iterator RI = mri_.reg_begin(curli->reg),
RE = mri_.reg_end(); RI != RE;) {
MachineOperand &MO = RI.getOperand();
MachineInstr *MI = MO.getParent();
++RI;
if (MI->isDebugValue()) {
DEBUG(dbgs() << "Zapping " << *MI);
// FIXME: We can do much better with debug values.
MO.setReg(0);
continue;
}
SlotIndex Idx = lis_.getInstructionIndex(MI);
Idx = MO.isUse() ? Idx.getUseIndex() : Idx.getDefIndex();
LiveInterval *LI = 0;
for (unsigned i = firstInterval, e = intervals_.size(); i != e; ++i) {
LiveInterval *testli = intervals_[i];
if (testli->liveAt(Idx)) {
LI = testli;
break;
}
}
assert(LI && "No register was live at use");
MO.setReg(LI->reg);
DEBUG(dbgs() << " rewrite BB#" << MI->getParent()->getNumber() << '\t'
<< Idx << '\t' << *MI);
}
// Calculate spill weight and allocation hints for new intervals.
VirtRegAuxInfo vrai(vrm_.getMachineFunction(), lis_, sa_.loops_);
for (unsigned i = firstInterval, e = intervals_.size(); i != e; ++i) {
LiveInterval &li = *intervals_[i];
vrai.CalculateRegClass(li.reg);
vrai.CalculateWeightAndHint(li);
DEBUG(dbgs() << " new interval " << mri_.getRegClass(li.reg)->getName()
<< ":" << li << '\n');
}
}
//===----------------------------------------------------------------------===//
// Loop Splitting
//===----------------------------------------------------------------------===//
void SplitEditor::splitAroundLoop(const MachineLoop *Loop) {
SplitAnalysis::LoopBlocks Blocks;
sa_.getLoopBlocks(Loop, Blocks);
DEBUG({
dbgs() << " splitAroundLoop";
for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Loop.begin(),
E = Blocks.Loop.end(); I != E; ++I)
dbgs() << " BB#" << (*I)->getNumber();
dbgs() << ", preds:";
for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Preds.begin(),
E = Blocks.Preds.end(); I != E; ++I)
dbgs() << " BB#" << (*I)->getNumber();
dbgs() << ", exits:";
for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Exits.begin(),
E = Blocks.Exits.end(); I != E; ++I)
dbgs() << " BB#" << (*I)->getNumber();
dbgs() << '\n';
});
// Break critical edges as needed.
SplitAnalysis::BlockPtrSet CriticalExits;
sa_.getCriticalExits(Blocks, CriticalExits);
assert(CriticalExits.empty() && "Cannot break critical exits yet");
// Create new live interval for the loop.
openIntv();
// Insert copies in the predecessors.
for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Preds.begin(),
E = Blocks.Preds.end(); I != E; ++I) {
MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I);
enterIntvAtEnd(MBB);
}
// Switch all loop blocks.
for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Loop.begin(),
E = Blocks.Loop.end(); I != E; ++I)
useIntv(**I);
// Insert back copies in the exit blocks.
for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Exits.begin(),
E = Blocks.Exits.end(); I != E; ++I) {
MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I);
leaveIntvAtTop(MBB);
}
// Done.
closeIntv();
rewrite();
}
//===----------------------------------------------------------------------===//
// Single Block Splitting
//===----------------------------------------------------------------------===//
/// 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");
// Determine the first and last instruction using curli in each block.
typedef std::pair<SlotIndex,SlotIndex> IndexPair;
typedef DenseMap<const MachineBasicBlock*,IndexPair> IndexPairMap;
IndexPairMap MBBRange;
for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(),
E = sa_.usingInstrs_.end(); I != E; ++I) {
const MachineBasicBlock *MBB = (*I)->getParent();
if (!Blocks.count(MBB))
continue;
SlotIndex Idx = lis_.getInstructionIndex(*I);
DEBUG(dbgs() << " BB#" << MBB->getNumber() << '\t' << Idx << '\t' << **I);
IndexPair &IP = MBBRange[MBB];
if (!IP.first.isValid() || Idx < IP.first)
IP.first = Idx;
if (!IP.second.isValid() || Idx > IP.second)
IP.second = Idx;
}
// Create a new interval for each block.
for (SplitAnalysis::BlockPtrSet::const_iterator I = Blocks.begin(),
E = Blocks.end(); I != E; ++I) {
IndexPair &IP = MBBRange[*I];
DEBUG(dbgs() << " splitting for BB#" << (*I)->getNumber() << ": ["
<< IP.first << ';' << IP.second << ")\n");
assert(IP.first.isValid() && IP.second.isValid());
openIntv();
enterIntvBefore(IP.first);
useIntv(IP.first.getBaseIndex(), IP.second.getBoundaryIndex());
leaveIntvAfter(IP.second);
closeIntv();
}
rewrite();
}
//===----------------------------------------------------------------------===//
// Sub Block Splitting
//===----------------------------------------------------------------------===//
/// getBlockForInsideSplit - If curli is contained inside a single basic block,
/// and it wou pay to subdivide the interval inside that block, return it.
/// Otherwise return NULL. The returned block can be passed to
/// SplitEditor::splitInsideBlock.
const MachineBasicBlock *SplitAnalysis::getBlockForInsideSplit() {
// The interval must be exclusive to one block.
if (usingBlocks_.size() != 1)
return 0;
// Don't to this for less than 4 instructions. We want to be sure that
// splitting actually reduces the instruction count per interval.
if (usingInstrs_.size() < 4)
return 0;
return usingBlocks_.begin()->first;
}
/// splitInsideBlock - Split curli into multiple intervals inside MBB.
void SplitEditor::splitInsideBlock(const MachineBasicBlock *MBB) {
SmallVector<SlotIndex, 32> Uses;
Uses.reserve(sa_.usingInstrs_.size());
for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(),
E = sa_.usingInstrs_.end(); I != E; ++I)
if ((*I)->getParent() == MBB)
Uses.push_back(lis_.getInstructionIndex(*I));
DEBUG(dbgs() << " splitInsideBlock BB#" << MBB->getNumber() << " for "
<< Uses.size() << " instructions.\n");
assert(Uses.size() >= 3 && "Need at least 3 instructions");
array_pod_sort(Uses.begin(), Uses.end());
// Simple algorithm: Find the largest gap between uses as determined by slot
// indices. Create new intervals for instructions before the gap and after the
// gap.
unsigned bestPos = 0;
int bestGap = 0;
DEBUG(dbgs() << " dist (" << Uses[0]);
for (unsigned i = 1, e = Uses.size(); i != e; ++i) {
int g = Uses[i-1].distance(Uses[i]);
DEBUG(dbgs() << ") -" << g << "- (" << Uses[i]);
if (g > bestGap)
bestPos = i, bestGap = g;
}
DEBUG(dbgs() << "), best: -" << bestGap << "-\n");
// bestPos points to the first use after the best gap.
assert(bestPos > 0 && "Invalid gap");
// FIXME: Don't create intervals for low densities.
// First interval before the gap. Don't create single-instr intervals.
if (bestPos > 1) {
openIntv();
enterIntvBefore(Uses.front());
useIntv(Uses.front().getBaseIndex(), Uses[bestPos-1].getBoundaryIndex());
leaveIntvAfter(Uses[bestPos-1]);
closeIntv();
}
// Second interval after the gap.
if (bestPos < Uses.size()-1) {
openIntv();
enterIntvBefore(Uses[bestPos]);
useIntv(Uses[bestPos].getBaseIndex(), Uses.back().getBoundaryIndex());
leaveIntvAfter(Uses.back());
closeIntv();
}
rewrite();
}
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