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llvm-project/llvm/lib/CodeGen/SplitKit.cpp

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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 "LiveRangeEdit.h"
#include "VirtRegMap.h"
#include "llvm/CodeGen/CalcSpillWeights.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineDominators.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");
}
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 << ')';
}
}
// 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);
}
}
void SplitAnalysis::print(const LoopBlocks &B, raw_ostream &OS) const {
OS << "Loop:";
print(B.Loop, OS);
OS << ", preds:";
print(B.Preds, OS);
OS << ", exits:";
print(B.Exits, OS);
}
/// 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.
DEBUG(dbgs() << ", outside: BB#" << MBB->getNumber());
return OutsideLoop;
}
return use;
}
/// getCriticalExits - It may be necessary to partially break critical edges
/// leaving the loop if an exit block has predecessors from outside the loop
/// periphery.
void SplitAnalysis::getCriticalExits(const SplitAnalysis::LoopBlocks &Blocks,
BlockPtrSet &CriticalExits) {
CriticalExits.clear();
// A critical exit block has curli live-in, 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 *Exit = *I;
// A single-predecessor exit block is definitely not a critical edge.
if (Exit->pred_size() == 1)
continue;
// This exit may not have curli live in at all. No need to split.
if (!lis_.isLiveInToMBB(*curli_, Exit))
continue;
// Does this exit block have a predecessor that is not a loop block or loop
// predecessor?
for (MachineBasicBlock::const_pred_iterator PI = Exit->pred_begin(),
PE = Exit->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(Exit);
break;
}
}
}
void SplitAnalysis::getCriticalPreds(const SplitAnalysis::LoopBlocks &Blocks,
BlockPtrSet &CriticalPreds) {
CriticalPreds.clear();
// A critical predecessor block has curli live-out, and has a successor that
// has curli live-in and is not in the loop nor a loop exit block. For such a
// predecessor block, we must carry the value in both the 'inside' and
// 'outside' registers.
for (BlockPtrSet::iterator I = Blocks.Preds.begin(), E = Blocks.Preds.end();
I != E; ++I) {
const MachineBasicBlock *Pred = *I;
// Definitely not a critical edge.
if (Pred->succ_size() == 1)
continue;
// This block may not have curli live out at all if there is a PHI.
if (!lis_.isLiveOutOfMBB(*curli_, Pred))
continue;
// Does this block have a successor outside the loop?
for (MachineBasicBlock::const_pred_iterator SI = Pred->succ_begin(),
SE = Pred->succ_end(); SI != SE; ++SI) {
const MachineBasicBlock *Succ = *SI;
if (Blocks.Loop.count(Succ) || Blocks.Exits.count(Succ))
continue;
if (!lis_.isLiveInToMBB(*curli_, Succ))
continue;
// This is a critical predecessor block.
CriticalPreds.insert(Pred);
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;
LoopBlocks Blocks;
BlockPtrSet CriticalExits;
// We 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);
DEBUG({ dbgs() << " "; print(Blocks, dbgs()); });
switch(analyzeLoopPeripheralUse(Blocks)) {
case OutsideLoop:
break;
case MultiPeripheral:
// FIXME: We could split a live range with multiple uses in a peripheral
// block and still make progress. However, it is possible that splitting
// another live range will insert copies into a peripheral block, and
// there is a small chance we can enter an infinity loop, inserting copies
// forever.
// For safety, stick to splitting live ranges with uses outside the
// periphery.
DEBUG(dbgs() << ": multiple peripheral uses\n");
break;
case ContainedInLoop:
DEBUG(dbgs() << ": fully contained\n");
continue;
case SinglePeripheral:
DEBUG(dbgs() << ": single peripheral use\n");
continue;
}
// Will it be possible to split around this loop?
getCriticalExits(Blocks, CriticalExits);
DEBUG(dbgs() << ": " << CriticalExits.size() << " critical exits\n");
if (!canSplitCriticalExits(Blocks, CriticalExits))
continue;
// This is a possible split.
Loops.insert(Loop);
}
DEBUG(dbgs() << " getBestSplitLoop found " << Loops.size()
<< " candidate loops.\n");
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;
}
//===----------------------------------------------------------------------===//
// 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();
liveOutCache_.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());
// 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 =
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 search for all predecessor blocks where we know the dominating
// VNInfo. Insert phi-def VNInfos along the path back to IdxMBB.
DEBUG(dbgs() << "\n Reaching defs for BB#" << IdxMBB->getNumber()
<< " at " << Idx << " in " << *li_ << '\n');
// Blocks where li_ should be live-in.
SmallVector<MachineDomTreeNode*, 16> LiveIn;
LiveIn.push_back(mdt_[IdxMBB]);
// 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;
// Is this a known live-out block?
std::pair<LiveOutMap::iterator,bool> LOIP =
liveOutCache_.insert(std::make_pair(Pred, LiveOutPair()));
// Yes, we have been here before.
if (!LOIP.second) {
if (VNInfo *VNI = LOIP.first->second.first) {
DEBUG(dbgs() << " known valno #" << VNI->id
<< " at BB#" << Pred->getNumber() << '\n');
}
continue;
}
// Does Pred provide a live-out value?
SlotIndex Last = lis_.getMBBEndIdx(Pred).getPrevSlot();
if (VNInfo *VNI = extendTo(Pred, Last)) {
MachineBasicBlock *DefMBB = lis_.getMBBFromIndex(VNI->def);
DEBUG(dbgs() << " found valno #" << VNI->id
<< " from BB#" << DefMBB->getNumber()
<< " at BB#" << Pred->getNumber() << '\n');
LiveOutPair &LOP = LOIP.first->second;
LOP.first = VNI;
LOP.second = mdt_[lis_.getMBBFromIndex(VNI->def)];
continue;
}
// No, we need a live-in value for Pred as well
if (Pred != IdxMBB)
LiveIn.push_back(mdt_[Pred]);
}
}
// We may need to add phi-def values to preserve the SSA form.
// 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.
VNInfo *IdxVNI = 0;
unsigned Changes;
do {
Changes = 0;
DEBUG(dbgs() << " Iterating over " << LiveIn.size() << " blocks.\n");
// 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;
// Get the IDom live-out value.
if (!needPHI) {
LiveOutMap::iterator I = liveOutCache_.find(IDom->getBlock());
if (I != liveOutCache_.end())
IDomValue = I->second;
else
// If IDom is outside our set of live-out blocks, there must be new
// defs, and we need a phi-def here.
needPHI = true;
}
// 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) {
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);
DEBUG(dbgs() << " - BB#" << MBB->getNumber()
<< " phi-def #" << VNI->id << " at " << Start << '\n');
// 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.
LiveOutMap::iterator I = liveOutCache_.find(MBB);
if (I == liveOutCache_.end() || I->second.second == Node) {
// 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));
I->second = LiveOutPair(VNI, Node);
}
} else if (IDomValue.first) {
// No phi-def here. Remember incoming value for IdxMBB.
if (MBB == IdxMBB)
IdxVNI = IDomValue.first;
// Propagate IDomValue if needed:
// MBB is live-out and doesn't define its own value.
LiveOutMap::iterator I = liveOutCache_.find(MBB);
if (I != liveOutCache_.end() && I->second.second != Node &&
I->second.first != IDomValue.first) {
++Changes;
I->second = IDomValue;
DEBUG(dbgs() << " - BB#" << MBB->getNumber()
<< " idom valno #" << IDomValue.first->id
<< " from BB#" << IDom->getBlock()->getNumber() << '\n');
}
}
}
DEBUG(dbgs() << " - made " << Changes << " changes.\n");
} while (Changes);
assert(IdxVNI && "Didn't find value for Idx");
#ifndef NDEBUG
// Check the liveOutCache_ invariants.
for (LiveOutMap::iterator I = liveOutCache_.begin(), E = liveOutCache_.end();
I != E; ++I) {
assert(I->first && "Null MBB entry in cache");
assert(I->second.first && "Null VNInfo in cache");
assert(I->second.second && "Null DomTreeNode in cache");
if (I->second.second->getBlock() == I->first)
continue;
for (MachineBasicBlock::pred_iterator PI = I->first->pred_begin(),
PE = I->first->pred_end(); PI != PE; ++PI)
assert(liveOutCache_.lookup(*PI) == I->second && "Bad invariant");
}
#endif
// 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.
// This makes the next mapValue call much faster.
for (unsigned i = 0, e = LiveIn.size(); i != e; ++i) {
MachineBasicBlock *MBB = LiveIn[i]->getBlock();
SlotIndex Start = lis_.getMBBStartIdx(MBB);
if (MBB == IdxMBB) {
li_->addRange(LiveRange(Start, Idx.getNextSlot(), IdxVNI));
continue;
}
// Anything in LiveIn other than IdxMBB is live-through.
VNInfo *VNI = liveOutCache_.lookup(MBB).first;
assert(VNI && "Missing block value");
li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI));
}
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(const 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,
MachineDominatorTree &mdt,
LiveRangeEdit &edit)
: sa_(sa), lis_(lis), vrm_(vrm),
mri_(vrm.getMachineFunction().getRegInfo()),
tii_(*vrm.getMachineFunction().getTarget().getInstrInfo()),
edit_(edit),
dupli_(lis_, mdt, edit.getParent()),
openli_(lis_, mdt, edit.getParent())
{
}
bool SplitEditor::intervalsLiveAt(SlotIndex Idx) const {
for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E; ++I)
if (*I != dupli_.getLI() && (*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(&edit_.create(mri_, lis_, vrm_));
openli_.reset(&edit_.create(mri_, lis_, vrm_));
}
/// 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 = edit_.getParent().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(edit_.getReg(), 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 = edit_.getParent().getVNInfoAt(End.getPrevSlot());
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return;
}
DEBUG(dbgs() << ": valno " << ParentVNI->id);
truncatedValues.insert(ParentVNI);
VNInfo *VNI = openli_.defByCopyFrom(edit_.getReg(), 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 = edit_.getParent().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 = edit_.getParent().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);
}
/// rewrite - Rewrite all uses of reg to use the new registers.
void SplitEditor::rewrite(unsigned reg) {
for (MachineRegisterInfo::reg_iterator RI = mri_.reg_begin(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 (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E;
++I) {
LiveInterval *testli = *I;
if (testli->liveAt(Idx)) {
LI = testli;
break;
}
}
DEBUG(dbgs() << " rewr BB#" << MI->getParent()->getNumber() << '\t'<< Idx);
assert(LI && "No register was live at use");
MO.setReg(LI->reg);
DEBUG(dbgs() << '\t' << *MI);
}
}
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 (LiveRangeEdit::iterator LI = edit_.begin(), LE = edit_.end(); LI != LE;
++LI) {
if (*LI == dupli_.getLI())
continue;
LiveInterval::const_iterator I = (*LI)->find(Start);
LiveInterval::const_iterator E = (*LI)->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;
}
}
void SplitEditor::computeRemainder() {
// 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.
LiveInterval &parent = edit_.getParent();
// 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 = parent.vni_begin(),
E = parent.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 = parent.begin(), E = parent.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);
}
}
// Extend dupli_ to be live out of any critical loop predecessors.
// This means we have multiple registers live out of those blocks.
// The alternative would be to split the critical edges.
if (criticalPreds_.empty())
return;
for (SplitAnalysis::BlockPtrSet::iterator I = criticalPreds_.begin(),
E = criticalPreds_.end(); I != E; ++I)
dupli_.extendTo(*I, lis_.getMBBEndIdx(*I).getPrevSlot());
criticalPreds_.clear();
}
void SplitEditor::finish() {
assert(!openli_.getLI() && "Previous LI not closed before rewrite");
assert(dupli_.getLI() && "No dupli for rewrite. Noop spilt?");
// Complete dupli liveness.
computeRemainder();
// 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_);
// Rewrite instructions.
rewrite(edit_.getReg());
// 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_));
ConEQ.Distribute(&dups[0]);
// Rewrite uses to the new regs.
rewrite(li->reg);
}
// 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');
}
}
//===----------------------------------------------------------------------===//
// Loop Splitting
//===----------------------------------------------------------------------===//
void SplitEditor::splitAroundLoop(const MachineLoop *Loop) {
SplitAnalysis::LoopBlocks Blocks;
sa_.getLoopBlocks(Loop, Blocks);
DEBUG({
dbgs() << " splitAround"; sa_.print(Blocks, dbgs()); dbgs() << '\n';
});
// Break critical edges as needed.
SplitAnalysis::BlockPtrSet CriticalExits;
sa_.getCriticalExits(Blocks, CriticalExits);
assert(CriticalExits.empty() && "Cannot break critical exits yet");
// Get critical predecessors so computeRemainder can deal with them.
sa_.getCriticalPreds(Blocks, criticalPreds_);
// 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();
finish();
}
//===----------------------------------------------------------------------===//
// 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 (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: {
// When there are only two uses and curli is both live in and live out,
// we don't really win anything by isolating the block since we would be
// inserting two copies.
// The remaing register would still have two uses in the block. (Unless it
// separates into disconnected components).
if (lis_.isLiveInToMBB(*curli_, I->first) &&
lis_.isLiveOutOfMBB(*curli_, I->first))
continue;
} // Fall through.
default:
Blocks.insert(I->first);
}
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");
// 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();
}
finish();
}
//===----------------------------------------------------------------------===//
// 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();
}
finish();
}
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