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llvm-6502/lib/CodeGen/SplitKit.cpp
Michael J. Spencer 6715be20e2 Fix the msvc 2010 build. 
The Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 16.00.30319.01
implements parts of C++0x based on the draft standard. An old version of
the draft had a bug that makes std::pair<T1*, T2*>(something, 0) fail to
compile. This is because the template<class U, class V> pair(U&& x, V&& y)
constructor is selected, even though it later fails to implicitly convert
U and V to frist_type and second_type.

This has been fixed in n3090, but it seems that Microsoft is not going to
update msvc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111535 91177308-0d34-0410-b5e6-96231b3b80d8
2010-08-19 18:16:39 +00:00

1098 lines
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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;
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, static_cast<VNInfo *>(0))).first->second;
// The static_cast<VNInfo *> is only needed to work around a bug in an
// old version of the C++0x standard which the following compilers
// implemented and have yet to fix:
//
// Microsoft Visual Studio 2010 Version 10.0.30319.1 RTMRel
// Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 16.00.30319.01
//
// If/When we move to C++0x, this can be replaced by nullptr.
(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, static_cast<VNInfo *>(0)));
// The static_cast<VNInfo *> is only needed to work around a bug in an
// old version of the C++0x standard which the following compilers
// implemented and have yet to fix:
//
// Microsoft Visual Studio 2010 Version 10.0.30319.1 RTMRel
// Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 16.00.30319.01
//
// If/When we move to C++0x, this can be replaced by nullptr.
// 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. 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, true, 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, 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) {
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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