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Implement single block splitting. 

Before spilling a live range, we split it into a separate range for each basic
block where it is used. That way we only get one reload per basic block if the
new smaller ranges can allocate to a register.

This type of splitting is already present in the standard spiller.

llvm-svn: 110934
This commit is contained in:
Jakob Stoklund Olesen 2010-08-12 17:07:14 +00:00
parent 02690ba643
commit 622848b262
3 changed files with 158 additions and 5 deletions
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9
llvm/lib/CodeGen/InlineSpiller.cpp
View File

@ -118,6 +118,15 @@ bool InlineSpiller::split() {
.splitAroundLoop(loop))
return true;
}
// Try splitting into single block intervals.
SplitAnalysis::BlockPtrSet blocks;
if (splitAnalysis_.getMultiUseBlocks(blocks)) {
if (SplitEditor(splitAnalysis_, lis_, vrm_, *newIntervals_)
.splitSingleBlocks(blocks))
return true;
}
return false;
}

128
llvm/lib/CodeGen/SplitKit.cpp
View File

@ -279,6 +279,33 @@ const MachineLoop *SplitAnalysis::getBestSplitLoop() {
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();
}
//===----------------------------------------------------------------------===//
// Split Editor
@ -351,6 +378,27 @@ void SplitEditor::openIntv() {
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.
@ -435,6 +483,39 @@ void SplitEditor::useIntv(SlotIndex Start, SlotIndex End) {
<< '\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 at " << 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) {
@ -528,6 +609,7 @@ void SplitEditor::closeIntv() {
DEBUG(dbgs() << " dup2 " << *dupli_ << '\n');
}
openli_ = 0;
valueMap_.clear();
}
/// rewrite - after all the new live ranges have been created, rewrite
@ -620,3 +702,49 @@ bool SplitEditor::splitAroundLoop(const MachineLoop *Loop) {
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_;
}

26
llvm/lib/CodeGen/SplitKit.h
View File

@ -37,10 +37,6 @@ public:
const MachineLoopInfo &loops_;
const TargetInstrInfo &tii_;
private:
// Current live interval.
const LiveInterval *curli_;
// Instructions using the the current register.
typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet;
InstrPtrSet usingInstrs_;
@ -53,6 +49,10 @@ private:
typedef SmallPtrSet<const MachineLoop*, 16> LoopPtrSet;
LoopPtrSet usingLoops_;
private:
// Current live interval.
const LiveInterval *curli_;
// Sumarize statistics by counting instructions using curli_.
void analyzeUses();
@ -118,6 +118,11 @@ public:
/// getBestSplitLoop - Return the loop where curli may best be split to a
/// separate register, or NULL.
const MachineLoop *getBestSplitLoop();
/// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
/// having curli split to a new live interval. Return true if Blocks can be
/// passed to SplitEditor::splitSingleBlocks.
bool getMultiUseBlocks(BlockPtrSet &Blocks);
};
/// SplitEditor - Edit machine code and LiveIntervals for live range
@ -156,7 +161,7 @@ class SplitEditor {
/// getDupLI - Ensure dupli is created and return it.
LiveInterval *getDupLI();
/// valueMap_ - Map values in dupli to values in openIntv. These are direct 1-1
/// valueMap_ - Map values in cupli to values in openli. These are direct 1-1
/// mappings, and do not include values created by inserted copies.
DenseMap<const VNInfo*, VNInfo*> valueMap_;
@ -192,6 +197,10 @@ public:
/// Create a new virtual register and live interval.
void openIntv();
/// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
/// not live before Idx, a COPY is not inserted.
void enterIntvBefore(SlotIndex Idx);
/// 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.
@ -203,6 +212,9 @@ public:
/// useIntv - indicate that all instructions in range should use openli.
void useIntv(SlotIndex Start, SlotIndex End);
/// leaveIntvAfter - Leave openli after the instruction at Idx.
void leaveIntvAfter(SlotIndex Idx);
/// leaveIntvAtTop - Leave the interval at the top of MBB.
/// Currently, only one value can leave the interval.
void leaveIntvAtTop(MachineBasicBlock &MBB);
@ -222,6 +234,10 @@ public:
/// curli is still intact, and needs to be spilled or split further.
bool splitAroundLoop(const MachineLoop*);
/// 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 splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
};