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Promote MergePotentialsElt and SameTailElt to be regular classes

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instead of typedefs for std::pair. This simplifies the type of
SameTails, which previously was std::vector<std::pair<std::vector<std::pair<unsigned, MachineBasicBlock *> >::iterator, MachineBasicBlock::iterator>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86885 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-11-11 21:57:02 +00:00
parent c158dde219
commit ffe644ebf4
2 changed files with 107 additions and 58 deletions
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114
lib/CodeGen/BranchFolding.cpp
View File

@ -429,24 +429,24 @@ static void FixTail(MachineBasicBlock* CurMBB, MachineBasicBlock *SuccBB,
TII->InsertBranch(*CurMBB, SuccBB, NULL, SmallVector<MachineOperand, 0>());
}
static bool MergeCompare(const std::pair<unsigned,MachineBasicBlock*> &p,
const std::pair<unsigned,MachineBasicBlock*> &q) {
if (p.first < q.first)
return true;
else if (p.first > q.first)
return false;
else if (p.second->getNumber() < q.second->getNumber())
return true;
else if (p.second->getNumber() > q.second->getNumber())
return false;
else {
// _GLIBCXX_DEBUG checks strict weak ordering, which involves comparing
// an object with itself.
bool
BranchFolder::MergePotentialsElt::operator<(const MergePotentialsElt &o) const {
if (getHash() < o.getHash())
return true;
else if (getHash() > o.getHash())
return false;
else if (getBlock()->getNumber() < o.getBlock()->getNumber())
return true;
else if (getBlock()->getNumber() > o.getBlock()->getNumber())
return false;
else {
// _GLIBCXX_DEBUG checks strict weak ordering, which involves comparing
// an object with itself.
#ifndef _GLIBCXX_DEBUG
llvm_unreachable("Predecessor appears twice");
llvm_unreachable("Predecessor appears twice");
#endif
return false;
}
return false;
}
}
/// CountTerminators - Count the number of terminators in the given
@ -537,22 +537,23 @@ unsigned BranchFolder::ComputeSameTails(unsigned CurHash,
MPIterator HighestMPIter = prior(MergePotentials.end());
for (MPIterator CurMPIter = prior(MergePotentials.end()),
B = MergePotentials.begin();
CurMPIter!=B && CurMPIter->first == CurHash;
CurMPIter!=B && CurMPIter->getHash() == CurHash;
--CurMPIter) {
for (MPIterator I = prior(CurMPIter); I->first == CurHash ; --I) {
for (MPIterator I = prior(CurMPIter); I->getHash() == CurHash ; --I) {
unsigned CommonTailLen;
if (ProfitableToMerge(CurMPIter->second, I->second, minCommonTailLength,
if (ProfitableToMerge(CurMPIter->getBlock(), I->getBlock(),
minCommonTailLength,
CommonTailLen, TrialBBI1, TrialBBI2,
SuccBB, PredBB)) {
if (CommonTailLen > maxCommonTailLength) {
SameTails.clear();
maxCommonTailLength = CommonTailLen;
HighestMPIter = CurMPIter;
SameTails.push_back(std::make_pair(CurMPIter, TrialBBI1));
SameTails.push_back(SameTailElt(CurMPIter, TrialBBI1));
}
if (HighestMPIter == CurMPIter &&
CommonTailLen == maxCommonTailLength)
SameTails.push_back(std::make_pair(I, TrialBBI2));
SameTails.push_back(SameTailElt(I, TrialBBI2));
}
if (I == B)
break;
@ -568,16 +569,16 @@ void BranchFolder::RemoveBlocksWithHash(unsigned CurHash,
MachineBasicBlock* PredBB) {
MPIterator CurMPIter, B;
for (CurMPIter = prior(MergePotentials.end()), B = MergePotentials.begin();
CurMPIter->first == CurHash;
CurMPIter->getHash() == CurHash;
--CurMPIter) {
// Put the unconditional branch back, if we need one.
MachineBasicBlock *CurMBB = CurMPIter->second;
MachineBasicBlock *CurMBB = CurMPIter->getBlock();
if (SuccBB && CurMBB != PredBB)
FixTail(CurMBB, SuccBB, TII);
if (CurMPIter == B)
break;
}
if (CurMPIter->first!=CurHash)
if (CurMPIter->getHash() != CurHash)
CurMPIter++;
MergePotentials.erase(CurMPIter, MergePotentials.end());
}
@ -590,29 +591,30 @@ unsigned BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
unsigned TimeEstimate = ~0U;
for (i=0, commonTailIndex=0; i<SameTails.size(); i++) {
// Use PredBB if possible; that doesn't require a new branch.
if (SameTails[i].first->second == PredBB) {
if (SameTails[i].getBlock() == PredBB) {
commonTailIndex = i;
break;
}
// Otherwise, make a (fairly bogus) choice based on estimate of
// how long it will take the various blocks to execute.
unsigned t = EstimateRuntime(SameTails[i].first->second->begin(),
SameTails[i].second);
unsigned t = EstimateRuntime(SameTails[i].getBlock()->begin(),
SameTails[i].getTailStartPos());
if (t <= TimeEstimate) {
TimeEstimate = t;
commonTailIndex = i;
}
}
MachineBasicBlock::iterator BBI = SameTails[commonTailIndex].second;
MachineBasicBlock *MBB = SameTails[commonTailIndex].first->second;
MachineBasicBlock::iterator BBI =
SameTails[commonTailIndex].getTailStartPos();
MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock();
DEBUG(errs() << "\nSplitting BB#" << MBB->getNumber() << ", size "
<< maxCommonTailLength);
MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI);
SameTails[commonTailIndex].first->second = newMBB;
SameTails[commonTailIndex].second = newMBB->begin();
SameTails[commonTailIndex].setBlock(newMBB);
SameTails[commonTailIndex].setTailStartPos(newMBB->begin());
// If we split PredBB, newMBB is the new predecessor.
if (PredBB == MBB)
@ -641,22 +643,22 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB,
// new branching and as such are very likely to be profitable.
if (SuccBB) {
if (SuccBB->pred_size() == MergePotentials.size() &&
!MergePotentials[0].second->empty()) {
!MergePotentials[0].getBlock()->empty()) {
// If all the predecessors have at least one tail instruction in common,
// merging is very likely to be a win since it won't require an increase
// in static branches, and it will decrease the static instruction count.
bool AllPredsMatch = true;
MachineBasicBlock::iterator FirstNonTerm;
unsigned MinNumTerms = CountTerminators(MergePotentials[0].second,
unsigned MinNumTerms = CountTerminators(MergePotentials[0].getBlock(),
FirstNonTerm);
if (FirstNonTerm != MergePotentials[0].second->end()) {
if (FirstNonTerm != MergePotentials[0].getBlock()->end()) {
for (unsigned i = 1, e = MergePotentials.size(); i != e; ++i) {
MachineBasicBlock::iterator OtherFirstNonTerm;
unsigned NumTerms = CountTerminators(MergePotentials[0].second,
unsigned NumTerms = CountTerminators(MergePotentials[0].getBlock(),
OtherFirstNonTerm);
if (NumTerms < MinNumTerms)
MinNumTerms = NumTerms;
if (OtherFirstNonTerm == MergePotentials[i].second->end() ||
if (OtherFirstNonTerm == MergePotentials[i].getBlock()->end() ||
OtherFirstNonTerm->isIdenticalTo(FirstNonTerm)) {
AllPredsMatch = false;
break;
@ -672,7 +674,7 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB,
DEBUG(errs() << "\nTryTailMergeBlocks: ";
for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
errs() << "BB#" << MergePotentials[i].second->getNumber()
errs() << "BB#" << MergePotentials[i].getBlock()->getNumber()
<< (i == e-1 ? "" : ", ");
errs() << "\n";
if (SuccBB) {
@ -688,11 +690,11 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB,
// Sort by hash value so that blocks with identical end sequences sort
// together.
std::stable_sort(MergePotentials.begin(), MergePotentials.end(),MergeCompare);
std::stable_sort(MergePotentials.begin(), MergePotentials.end());
// Walk through equivalence sets looking for actual exact matches.
while (MergePotentials.size() > 1) {
unsigned CurHash = MergePotentials.back().first;
unsigned CurHash = MergePotentials.back().getHash();
// Build SameTails, identifying the set of blocks with this hash code
// and with the maximum number of instructions in common.
@ -711,31 +713,30 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB,
// block, which we can't jump to), we can treat all blocks with this same
// tail at once. Use PredBB if that is one of the possibilities, as that
// will not introduce any extra branches.
MachineBasicBlock *EntryBB = MergePotentials.begin()->second->
getParent()->begin();
unsigned int commonTailIndex, i;
for (commonTailIndex=SameTails.size(), i=0; i<SameTails.size(); i++) {
MachineBasicBlock *MBB = SameTails[i].first->second;
MachineBasicBlock *EntryBB = MergePotentials.begin()->getBlock()->
getParent()->begin();
unsigned commonTailIndex = SameTails.size();
for (unsigned i=0; i<SameTails.size(); i++) {
MachineBasicBlock *MBB = SameTails[i].getBlock();
if (MBB == EntryBB)
continue;
if (MBB == PredBB) {
commonTailIndex = i;
break;
}
if (MBB->begin() == SameTails[i].second)
if (MBB->begin() == SameTails[i].getTailStartPos())
commonTailIndex = i;
}
if (commonTailIndex == SameTails.size() ||
(SameTails[commonTailIndex].first->second == PredBB &&
SameTails[commonTailIndex].first->second->begin() !=
SameTails[i].second)) {
(SameTails[commonTailIndex].getBlock() == PredBB &&
!SameTails[commonTailIndex].tailIsWholeBlock())) {
// None of the blocks consist entirely of the common tail.
// Split a block so that one does.
commonTailIndex = CreateCommonTailOnlyBlock(PredBB, maxCommonTailLength);
}
MachineBasicBlock *MBB = SameTails[commonTailIndex].first->second;
MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock();
// MBB is common tail. Adjust all other BB's to jump to this one.
// Traversal must be forwards so erases work.
DEBUG(errs() << "\nUsing common tail in BB#" << MBB->getNumber()
@ -743,12 +744,12 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB,
for (unsigned int i=0, e = SameTails.size(); i != e; ++i) {
if (commonTailIndex == i)
continue;
DEBUG(errs() << "BB#" << SameTails[i].first->second->getNumber()
DEBUG(errs() << "BB#" << SameTails[i].getBlock()->getNumber()
<< (i == e-1 ? "" : ", "));
// Hack the end off BB i, making it jump to BB commonTailIndex instead.
ReplaceTailWithBranchTo(SameTails[i].second, MBB);
ReplaceTailWithBranchTo(SameTails[i].getTailStartPos(), MBB);
// BB i is no longer a predecessor of SuccBB; remove it from the worklist.
MergePotentials.erase(SameTails[i].first);
MergePotentials.erase(SameTails[i].getMPIter());
}
DEBUG(errs() << "\n");
// We leave commonTailIndex in the worklist in case there are other blocks
@ -768,7 +769,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
MergePotentials.clear();
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
if (I->succ_empty())
MergePotentials.push_back(std::make_pair(HashEndOfMBB(I, 2U), I));
MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(I, 2U), I));
}
// See if we can do any tail merging on those.
@ -854,7 +855,8 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
// reinsert conditional branch only, for now
TII->InsertBranch(*PBB, (TBB == IBB) ? FBB : TBB, 0, NewCond);
}
MergePotentials.push_back(std::make_pair(HashEndOfMBB(PBB, 1U), *P));
MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(PBB, 1U),
*P));
}
}
if (MergePotentials.size() >= 2)
@ -863,8 +865,8 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
// The 1 below can occur as a result of removing blocks in TryTailMergeBlocks.
PredBB = prior(I); // this may have been changed in TryTailMergeBlocks
if (MergePotentials.size() == 1 &&
MergePotentials.begin()->second != PredBB)
FixTail(MergePotentials.begin()->second, IBB, TII);
MergePotentials.begin()->getBlock() != PredBB)
FixTail(MergePotentials.begin()->getBlock(), IBB, TII);
}
}
return MadeChange;

51
lib/CodeGen/BranchFolding.h
View File

@ -30,11 +30,58 @@ namespace llvm {
const TargetRegisterInfo *tri,
MachineModuleInfo *mmi);
private:
typedef std::pair<unsigned,MachineBasicBlock*> MergePotentialsElt;
class MergePotentialsElt {
unsigned Hash;
MachineBasicBlock *Block;
public:
MergePotentialsElt(unsigned h, MachineBasicBlock *b)
: Hash(h), Block(b) {}
unsigned getHash() const { return Hash; }
MachineBasicBlock *getBlock() const { return Block; }
void setBlock(MachineBasicBlock *MBB) {
Block = MBB;
}
bool operator<(const MergePotentialsElt &) const;
};
typedef std::vector<MergePotentialsElt>::iterator MPIterator;
std::vector<MergePotentialsElt> MergePotentials;
typedef std::pair<MPIterator, MachineBasicBlock::iterator> SameTailElt;
class SameTailElt {
MPIterator MPIter;
MachineBasicBlock::iterator TailStartPos;
public:
SameTailElt(MPIterator mp, MachineBasicBlock::iterator tsp)
: MPIter(mp), TailStartPos(tsp) {}
MPIterator getMPIter() const {
return MPIter;
}
MergePotentialsElt &getMergePotentialsElt() const {
return *getMPIter();
}
MachineBasicBlock::iterator getTailStartPos() const {
return TailStartPos;
}
unsigned getHash() const {
return getMergePotentialsElt().getHash();
}
MachineBasicBlock *getBlock() const {
return getMergePotentialsElt().getBlock();
}
bool tailIsWholeBlock() const {
return TailStartPos == getBlock()->begin();
}
void setBlock(MachineBasicBlock *MBB) {
getMergePotentialsElt().setBlock(MBB);
}
void setTailStartPos(MachineBasicBlock::iterator Pos) {
TailStartPos = Pos;
}
};
std::vector<SameTailElt> SameTails;
bool EnableTailMerge;