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1407c84242
llvm/lib/CodeGen/SplitKit.cpp
Jakob Stoklund Olesen 1407c84242 Add the LiveIntervalMap class. Don't hook it up yet. 
LiveIntervalMap maps values from a parent LiveInterval to a child interval that
is a strict subset. It will create phi-def values as needed to preserve the
VNInfo SSA form in the child interval.

This leads to an algorithm very similar to the one in SSAUpdaterImpl.h, but with
enough differences that the code can't be reused:

- We don't need to manipulate PHI instructions.
- LiveIntervals have kills.
- We have MachineDominatorTree.
- We can use df_iterator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111393 91177308-0d34-0410-b5e6-96231b3b80d8
2010-08-18 19:00:08 +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 "splitter"
#include "SplitKit.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;
if (MachineLoop *Loop = loops_.getLoopFor(MBB))
usingLoops_[Loop]++;
}
DEBUG(dbgs() << " counted "
<< usingInstrs_.size() << " instrs, "
<< usingBlocks_.size() << " blocks, "
<< usingLoops_.size() << " loops.\n");
}
/// removeUse - Update statistics by noting that MI no longer uses curli.
void SplitAnalysis::removeUse(const MachineInstr *MI) {
if (!usingInstrs_.erase(MI))
return;
// Decrement MBB count.
const MachineBasicBlock *MBB = MI->getParent();
BlockCountMap::iterator bi = usingBlocks_.find(MBB);
assert(bi != usingBlocks_.end() && "MBB missing");
assert(bi->second && "0 count in map");
if (--bi->second)
return;
// No more uses in MBB.
usingBlocks_.erase(bi);
// Decrement loop count.
MachineLoop *Loop = loops_.getLoopFor(MBB);
if (!Loop)
return;
LoopCountMap::iterator li = usingLoops_.find(Loop);
assert(li != usingLoops_.end() && "Loop missing");
assert(li->second && "0 count in map");
if (--li->second)
return;
// No more blocks in Loop.
usingLoops_.erase(li);
}
// 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);
// FIXME: We need an SSA updater to properly handle multiple exit blocks.
if (Blocks.Exits.size() > 1) {
DEBUG(dbgs() << " multiple exits from " << *Loop);
continue;
}
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
//===----------------------------------------------------------------------===//
// defValue - Introduce a li_ def for ParentVNI that could be later than
// ParentVNI->def.
VNInfo *LiveIntervalMap::defValue(const VNInfo *ParentVNI, SlotIndex Idx) {
assert(ParentVNI && "Mapping NULL value");
assert(Idx.isValid() && "Invalid SlotIndex");
assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI");
// Is this a simple 1-1 mapping? Not likely.
if (Idx == ParentVNI->def)
return mapValue(ParentVNI, Idx);
// This is a complex def. Mark with a NULL in valueMap.
VNInfo *OldVNI =
valueMap_.insert(ValueMap::value_type(ParentVNI, 0)).first->second;
(void)OldVNI;
assert(OldVNI == 0 && "Simple/Complex values mixed");
// Should we insert a minimal snippet of VNI LiveRange, or can we count on
// callers to do that? We need it for lookups of complex values.
VNInfo *VNI = li_.getNextValue(Idx, 0, true, lis_.getVNInfoAllocator());
return VNI;
}
// mapValue - Find the mapped value for ParentVNI at Idx.
// Potentially create phi-def values.
VNInfo *LiveIntervalMap::mapValue(const VNInfo *ParentVNI, SlotIndex Idx) {
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(ValueMap::value_type(ParentVNI, 0));
// This was an unknown value. Create a simple mapping.
if (InsP.second)
return InsP.first->second = li_.createValueCopy(ParentVNI,
lis_.getVNInfoAllocator());
// This was a simple mapped value.
if (InsP.first->second)
return InsP.first->second;
// This is a complex mapped value. There may be multiple defs, and we may need
// to create phi-defs.
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;
for (idf_iterator<MachineBasicBlock*>
IDFI = idf_begin(IdxMBB),
IDFE = idf_end(IdxMBB); IDFI != IDFE;) {
MachineBasicBlock *MBB = *IDFI;
SlotIndex End = lis_.getMBBEndIdx(MBB);
// We are operating on the restricted CFG where ParentVNI is live.
if (parentli_.getVNInfoAt(End.getPrevSlot()) != 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. 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.
MachineBasicBlock *Succ = IDFI.getPath(PI-1);
std::pair<MBBValueMap::iterator, bool> InsP =
DomValue.insert(MBBValueMap::value_type(Succ, VNI));
SlotIndex Start = lis_.getMBBStartIdx(Succ);
if (InsP.second) {
// This is the first time we backtrack to Succ. Verify dominance.
if (Succ->pred_size() == 1 || dt_.dominates(MBB, Succ))
continue;
} else if (InsP.first->second == VNI ||
InsP.first->second->def == Start) {
// We have previously backtracked VNI to Succ, or Succ already has a
// phi-def. No need to backtrack further.
break;
}
// VNI does not dominate Succ, we need a new phi-def.
VNI = li_.getNextValue(Start, 0, true, lis_.getVNInfoAllocator());
VNI->setIsPHIDef(true);
InsP.first->second = VNI;
MBB = Succ;
}
// No need to search the children, we found a dominating value.
// FIXME: We could prune up to the last phi-def we inserted, need df_iterator
// for that.
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, VNI));
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) {
LiveInterval::iterator I = std::upper_bound(li_.begin(), li_.end(), Idx);
if (I == li_.begin())
return 0;
--I;
if (I->start < lis_.getMBBStartIdx(MBB))
return 0;
if (I->end < Idx)
I->end = Idx;
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) {
VNInfo *VNI = mapValue(ParentVNI, Start);
// A simple mappoing is easy.
if (VNI->def == ParentVNI->def) {
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);
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) {
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);
}
//===----------------------------------------------------------------------===//
// 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_(0), openli_(0),
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 curli = sa_.getCurLI()->reg;
unsigned Reg = mri_.createVirtualRegister(mri_.getRegClass(curli));
LiveInterval &Intv = lis_.getOrCreateInterval(Reg);
vrm_.grow();
vrm_.assignVirt2StackSlot(Reg, vrm_.getStackSlot(curli));
return &Intv;
}
LiveInterval *SplitEditor::getDupLI() {
if (!dupli_) {
// Create an interval for dupli that is a copy of curli.
dupli_ = createInterval();
dupli_->Copy(*curli_, &mri_, lis_.getVNInfoAllocator());
}
return dupli_;
}
VNInfo *SplitEditor::mapValue(const VNInfo *curliVNI) {
VNInfo *&VNI = valueMap_[curliVNI];
if (!VNI)
VNI = openli_->createValueCopy(curliVNI, lis_.getVNInfoAllocator());
return VNI;
}
/// Insert a COPY instruction curli -> li. Allocate a new value from li
/// defined by the COPY. Note that rewrite() will deal with the curli
/// register, so this function can be used to copy from any interval - openli,
/// curli, or dupli.
VNInfo *SplitEditor::insertCopy(LiveInterval &LI,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) {
MachineInstr *MI = BuildMI(MBB, I, DebugLoc(), tii_.get(TargetOpcode::COPY),
LI.reg).addReg(curli_->reg);
SlotIndex DefIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
return LI.getNextValue(DefIdx, MI, true, lis_.getVNInfoAllocator());
}
/// Create a new virtual register and live interval.
void SplitEditor::openIntv() {
assert(!openli_ && "Previous LI not closed before openIntv");
openli_ = createInterval();
intervals_.push_back(openli_);
liveThrough_ = false;
}
/// 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_ && "openIntv not called before enterIntvBefore");
// Copy from curli_ if it is live.
if (VNInfo *CurVNI = curli_->getVNInfoAt(Idx.getUseIndex())) {
MachineInstr *MI = lis_.getInstructionFromIndex(Idx);
assert(MI && "enterIntvBefore called with invalid index");
VNInfo *VNI = insertCopy(*openli_, *MI->getParent(), MI);
openli_->addRange(LiveRange(VNI->def, Idx.getDefIndex(), VNI));
// Make sure CurVNI is properly mapped.
VNInfo *&mapVNI = valueMap_[CurVNI];
// We dont have SSA update yet, so only one entry per value is allowed.
assert(!mapVNI && "enterIntvBefore called more than once for the same value");
mapVNI = VNI;
}
DEBUG(dbgs() << " enterIntvBefore " << Idx << ": " << *openli_ << '\n');
}
/// enterIntvAtEnd - Enter openli at the end of MBB.
/// PhiMBB is a successor inside openli where a PHI value is created.
/// Currently, all entries must share the same PhiMBB.
void SplitEditor::enterIntvAtEnd(MachineBasicBlock &A, MachineBasicBlock &B) {
assert(openli_ && "openIntv not called before enterIntvAtEnd");
SlotIndex EndA = lis_.getMBBEndIdx(&A);
VNInfo *CurVNIA = curli_->getVNInfoAt(EndA.getPrevIndex());
if (!CurVNIA) {
DEBUG(dbgs() << " enterIntvAtEnd, curli not live out of BB#"
<< A.getNumber() << ".\n");
return;
}
// Add a phi kill value and live range out of A.
VNInfo *VNIA = insertCopy(*openli_, A, A.getFirstTerminator());
openli_->addRange(LiveRange(VNIA->def, EndA, VNIA));
// FIXME: If this is the only entry edge, we don't need the extra PHI value.
// FIXME: If there are multiple entry blocks (so not a loop), we need proper
// SSA update.
// Now look at the start of B.
SlotIndex StartB = lis_.getMBBStartIdx(&B);
SlotIndex EndB = lis_.getMBBEndIdx(&B);
const LiveRange *CurB = curli_->getLiveRangeContaining(StartB);
if (!CurB) {
DEBUG(dbgs() << " enterIntvAtEnd: curli not live in to BB#"
<< B.getNumber() << ".\n");
return;
}
VNInfo *VNIB = openli_->getVNInfoAt(StartB);
if (!VNIB) {
// Create a phi value.
VNIB = openli_->getNextValue(SlotIndex(StartB, true), 0, false,
lis_.getVNInfoAllocator());
VNIB->setIsPHIDef(true);
VNInfo *&mapVNI = valueMap_[CurB->valno];
if (mapVNI) {
// Multiple copies - must create PHI value.
abort();
} else {
// This is the first copy of dupLR. Mark the mapping.
mapVNI = VNIB;
}
}
DEBUG(dbgs() << " enterIntvAtEnd: " << *openli_ << '\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_ && "openIntv not called before useIntv");
// Map the curli values from the interval into openli_
LiveInterval::const_iterator B = curli_->begin(), E = curli_->end();
LiveInterval::const_iterator I = std::lower_bound(B, E, Start);
if (I != B) {
--I;
// I begins before Start, but overlaps.
if (I->end > Start)
openli_->addRange(LiveRange(Start, std::min(End, I->end),
mapValue(I->valno)));
++I;
}
// The remaining ranges begin after Start.
for (;I != E && I->start < End; ++I)
openli_->addRange(LiveRange(I->start, std::min(End, I->end),
mapValue(I->valno)));
DEBUG(dbgs() << " use [" << Start << ';' << End << "): " << *openli_
<< '\n');
}
/// leaveIntvAfter - Leave openli after the instruction at Idx.
void SplitEditor::leaveIntvAfter(SlotIndex Idx) {
assert(openli_ && "openIntv not called before leaveIntvAfter");
const LiveRange *CurLR = curli_->getLiveRangeContaining(Idx.getDefIndex());
if (!CurLR || CurLR->end <= Idx.getBoundaryIndex()) {
DEBUG(dbgs() << " leaveIntvAfter " << Idx << ": not live\n");
return;
}
// Was this value of curli live through openli?
if (!openli_->liveAt(CurLR->valno->def)) {
DEBUG(dbgs() << " leaveIntvAfter " << Idx << ": using external value\n");
liveThrough_ = true;
return;
}
// We are going to insert a back copy, so we must have a dupli_.
LiveRange *DupLR = getDupLI()->getLiveRangeContaining(Idx.getDefIndex());
assert(DupLR && "dupli not live into black, but curli is?");
// Insert the COPY instruction.
MachineBasicBlock::iterator I = lis_.getInstructionFromIndex(Idx);
MachineInstr *MI = BuildMI(*I->getParent(), llvm::next(I), I->getDebugLoc(),
tii_.get(TargetOpcode::COPY), dupli_->reg)
.addReg(openli_->reg);
SlotIndex CopyIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
openli_->addRange(LiveRange(Idx.getDefIndex(), CopyIdx,
mapValue(CurLR->valno)));
DupLR->valno->def = CopyIdx;
DEBUG(dbgs() << " leaveIntvAfter " << Idx << ": " << *openli_ << '\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_ && "openIntv not called before leaveIntvAtTop");
SlotIndex Start = lis_.getMBBStartIdx(&MBB);
const LiveRange *CurLR = curli_->getLiveRangeContaining(Start);
// Is curli even live-in to MBB?
if (!CurLR) {
DEBUG(dbgs() << " leaveIntvAtTop at " << Start << ": not live\n");
return;
}
// Is curli defined by PHI at the beginning of MBB?
bool isPHIDef = CurLR->valno->isPHIDef() &&
CurLR->valno->def.getBaseIndex() == Start;
// If MBB is using a value of curli that was defined outside the openli range,
// we don't want to copy it back here.
if (!isPHIDef && !openli_->liveAt(CurLR->valno->def)) {
DEBUG(dbgs() << " leaveIntvAtTop at " << Start
<< ": using external value\n");
liveThrough_ = true;
return;
}
// We are going to insert a back copy, so we must have a dupli_.
LiveRange *DupLR = getDupLI()->getLiveRangeContaining(Start);
assert(DupLR && "dupli not live into black, but curli is?");
// Insert the COPY instruction.
MachineInstr *MI = BuildMI(MBB, MBB.begin(), DebugLoc(),
tii_.get(TargetOpcode::COPY), dupli_->reg)
.addReg(openli_->reg);
SlotIndex Idx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
// Adjust dupli and openli values.
if (isPHIDef) {
// dupli was already a PHI on entry to MBB. Simply insert an openli PHI,
// and shift the dupli def down to the COPY.
VNInfo *VNI = openli_->getNextValue(SlotIndex(Start, true), 0, false,
lis_.getVNInfoAllocator());
VNI->setIsPHIDef(true);
openli_->addRange(LiveRange(VNI->def, Idx, VNI));
dupli_->removeRange(Start, Idx);
DupLR->valno->def = Idx;
DupLR->valno->setIsPHIDef(false);
} else {
// The dupli value was defined somewhere inside the openli range.
DEBUG(dbgs() << " leaveIntvAtTop source value defined at "
<< DupLR->valno->def << "\n");
// FIXME: We may not need a PHI here if all predecessors have the same
// value.
VNInfo *VNI = openli_->getNextValue(SlotIndex(Start, true), 0, false,
lis_.getVNInfoAllocator());
VNI->setIsPHIDef(true);
openli_->addRange(LiveRange(VNI->def, Idx, VNI));
// FIXME: What if DupLR->valno is used by multiple exits? SSA Update.
// closeIntv is going to remove the superfluous live ranges.
DupLR->valno->def = Idx;
DupLR->valno->setIsPHIDef(false);
}
DEBUG(dbgs() << " leaveIntvAtTop at " << Idx << ": " << *openli_ << '\n');
}
/// closeIntv - Indicate that we are done editing the currently open
/// LiveInterval, and ranges can be trimmed.
void SplitEditor::closeIntv() {
assert(openli_ && "openIntv not called before closeIntv");
DEBUG(dbgs() << " closeIntv cleaning up\n");
DEBUG(dbgs() << " open " << *openli_ << '\n');
if (liveThrough_) {
DEBUG(dbgs() << " value live through region, leaving dupli as is.\n");
} else {
// live out with copies inserted, or killed by region. Either way we need to
// remove the overlapping region from dupli.
getDupLI();
for (LiveInterval::iterator I = openli_->begin(), E = openli_->end();
I != E; ++I) {
dupli_->removeRange(I->start, I->end);
}
// FIXME: A block branching to the entry block may also branch elsewhere
// curli is live. We need both openli and curli to be live in that case.
DEBUG(dbgs() << " dup2 " << *dupli_ << '\n');
}
openli_ = 0;
valueMap_.clear();
}
/// rewrite - after all the new live ranges have been created, rewrite
/// instructions using curli to use the new intervals.
void SplitEditor::rewrite() {
assert(!openli_ && "Previous LI not closed before rewrite");
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 = dupli_;
for (unsigned i = firstInterval, e = intervals_.size(); i != e; ++i) {
LiveInterval *testli = intervals_[i];
if (testli->liveAt(Idx)) {
LI = testli;
break;
}
}
if (LI) {
MO.setReg(LI->reg);
sa_.removeUse(MI);
DEBUG(dbgs() << " rewrite " << Idx << '\t' << *MI);
}
}
// dupli_ goes in last, after rewriting.
if (dupli_) {
if (dupli_->empty()) {
DEBUG(dbgs() << " dupli became empty?\n");
lis_.removeInterval(dupli_->reg);
dupli_ = 0;
} else {
dupli_->RenumberValues(lis_);
intervals_.push_back(dupli_);
}
}
// 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
//===----------------------------------------------------------------------===//
bool SplitEditor::splitAroundLoop(const MachineLoop *Loop) {
SplitAnalysis::LoopBlocks Blocks;
sa_.getLoopBlocks(Loop, Blocks);
// 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, *Loop->getHeader());
}
// 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();
return dupli_;
}
//===----------------------------------------------------------------------===//
// Single Block Splitting
//===----------------------------------------------------------------------===//
/// splitSingleBlocks - Split curli into a separate live interval inside each
/// basic block in Blocks. Return true if curli has been completely replaced,
/// false if curli is still intact, and needs to be spilled or split further.
bool 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();
return dupli_;
}
//===----------------------------------------------------------------------===//
// 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. Return
/// true if curli has been completely replaced, false if curli is still
/// intact, and needs to be spilled or split further.
bool 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();
return dupli_;
}
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