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Remove an evil vector bool. Cosmetic refactoring,
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no functional change.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50921 91177308-0d34-0410-b5e6-96231b3b80d8
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Dale Johannesen committed May 9, 2008
1 parent 120de8a commit 27a8534
Showing 1 changed file with 85 additions and 62 deletions.
147 changes: 85 additions & 62 deletions lib/CodeGen/BranchFolding.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -71,10 +71,15 @@ namespace {
MachineBasicBlock *NewDest);
MachineBasicBlock *SplitMBBAt(MachineBasicBlock &CurMBB,
MachineBasicBlock::iterator BBI1);
unsigned ComputeSameTails(unsigned CurHash, unsigned minCommonTailLength);
void RemoveBlocksWithHash(unsigned CurHash, MachineBasicBlock* SuccBB,
MachineBasicBlock* PredBB);

typedef std::pair<unsigned,MachineBasicBlock*> MergePotentialsElt;
std::vector<MergePotentialsElt> MergePotentials;
typedef std::vector<MergePotentialsElt>::iterator MPIterator;
std::vector<MergePotentialsElt> MergePotentials;
typedef std::pair<MPIterator, MachineBasicBlock::iterator> SameTailElt;
std::vector<SameTailElt> SameTails;

const TargetRegisterInfo *RegInfo;
RegScavenger *RS;
Expand Down Expand Up @@ -221,8 +226,7 @@ bool BranchFolder::runOnMachineFunction(MachineFunction &MF) {
// If a jump table was merge with another one, walk the function rewriting
// references to jump tables to reference the new JT ID's. Keep track of
// whether we see a jump table idx, if not, we can delete the JT.
std::vector<bool> JTIsLive;
JTIsLive.resize(JTs.size());
BitVector JTIsLive(JTs.size());
for (MachineFunction::iterator BB = MF.begin(), E = MF.end();
BB != E; ++BB) {
for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
Expand All @@ -234,15 +238,15 @@ bool BranchFolder::runOnMachineFunction(MachineFunction &MF) {
Op.setIndex(NewIdx);

// Remember that this JT is live.
JTIsLive[NewIdx] = true;
JTIsLive.set(NewIdx);
}
}

// Finally, remove dead jump tables. This happens either because the
// indirect jump was unreachable (and thus deleted) or because the jump
// table was merged with some other one.
for (unsigned i = 0, e = JTIsLive.size(); i != e; ++i)
if (!JTIsLive[i]) {
if (!JTIsLive.test(i)) {
JTI->RemoveJumpTable(i);
EverMadeChange = true;
}
Expand Down Expand Up @@ -468,7 +472,7 @@ static void FixTail(MachineBasicBlock* CurMBB, MachineBasicBlock *SuccBB,
if (I != MF->end() &&
!TII->AnalyzeBranch(*CurMBB, TBB, FBB, Cond)) {
MachineBasicBlock *NextBB = I;
if (TBB == NextBB && Cond.size() && !FBB) {
if (TBB == NextBB && !Cond.empty() && !FBB) {
if (!TII->ReverseBranchCondition(Cond)) {
TII->RemoveBranch(*CurMBB);
TII->InsertBranch(*CurMBB, SuccBB, NULL, Cond);
Expand Down Expand Up @@ -499,6 +503,68 @@ static bool MergeCompare(const std::pair<unsigned,MachineBasicBlock*> &p,
}
}

/// ComputeSameTails - Look through all the blocks in MergePotentials that have
/// hash CurHash (guaranteed to match the last element). Build the vector
/// SameTails of all those that have the (same) largest number of instructions
/// in common of any pair of these blocks. SameTails entries contain an
/// iterator into MergePotentials (from which the MachineBasicBlock can be
/// found) and a MachineBasicBlock::iterator into that MBB indicating the
/// instruction where the matching code sequence begins.
/// Order of elements in SameTails is the reverse of the order in which
/// those blocks appear in MergePotentials (where they are not necessarily
/// consecutive).
unsigned BranchFolder::ComputeSameTails(unsigned CurHash,
unsigned minCommonTailLength) {
unsigned maxCommonTailLength = 0U;
SameTails.clear();
MachineBasicBlock::iterator TrialBBI1, TrialBBI2;
MPIterator HighestMPIter = prior(MergePotentials.end());
for (MPIterator CurMPIter = prior(MergePotentials.end()),
B = MergePotentials.begin();
CurMPIter!=B && CurMPIter->first==CurHash;
--CurMPIter) {
for (MPIterator I = prior(CurMPIter); I->first==CurHash ; --I) {
unsigned CommonTailLen = ComputeCommonTailLength(
CurMPIter->second,
I->second,
TrialBBI1, TrialBBI2);
if (CommonTailLen >= minCommonTailLength) {
if (CommonTailLen > maxCommonTailLength) {
SameTails.clear();
maxCommonTailLength = CommonTailLen;
HighestMPIter = CurMPIter;
SameTails.push_back(std::make_pair(CurMPIter, TrialBBI1));
}
if (HighestMPIter == CurMPIter &&
CommonTailLen == maxCommonTailLength)
SameTails.push_back(std::make_pair(I, TrialBBI2));
}
if (I==B)
break;
}
}
return maxCommonTailLength;
}

/// RemoveBlocksWithHash - Remove all blocks with hash CurHash from
/// MergePotentials, restoring branches at ends of blocks as appropriate.
void BranchFolder::RemoveBlocksWithHash(unsigned CurHash,
MachineBasicBlock* SuccBB,
MachineBasicBlock* PredBB) {
for (MPIterator CurMPIter = prior(MergePotentials.end()),
B = MergePotentials.begin();
CurMPIter->first==CurHash;
--CurMPIter) {
// Put the unconditional branch back, if we need one.
MachineBasicBlock *CurMBB = CurMPIter->second;
if (SuccBB && CurMBB != PredBB)
FixTail(CurMBB, SuccBB, TII);
MergePotentials.erase(CurMPIter);
if (CurMPIter==B)
break;
}
}

// See if any of the blocks in MergePotentials (which all have a common single
// successor, or all have no successor) can be tail-merged. If there is a
// successor, any blocks in MergePotentials that are not tail-merged and
Expand All @@ -520,67 +586,24 @@ bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
MadeChange = false;

DOUT << "\nTryMergeBlocks " << MergePotentials.size();

// 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(),MergeCompare);

// Walk through equivalence sets looking for actual exact matches.
while (MergePotentials.size() > 1) {
unsigned CurHash = prior(MergePotentials.end())->first;

// Look through all the other blocks that have the same hash as this
// one, and build a vector of all those that have the (same) largest number
// of instructions in common.
// Order of elements in SameTails is the reverse of the order in which
// those blocks appear in MergePotentials (where they are not necessarily
// consecutive).
typedef std::pair<MPIterator, MachineBasicBlock::iterator> SameTailElt;
std::vector<SameTailElt> SameTails;

unsigned maxCommonTailLength = 0U;
SameTails.clear();
MachineBasicBlock::iterator TrialBBI1, TrialBBI2;
MPIterator HighestMPIter = prior(MergePotentials.end());
for (MPIterator CurMPIter = prior(MergePotentials.end()),
B = MergePotentials.begin();
CurMPIter!=B && CurMPIter->first==CurHash;
--CurMPIter) {
for (MPIterator I = prior(CurMPIter); I->first==CurHash ; --I) {
unsigned CommonTailLen = ComputeCommonTailLength(
CurMPIter->second,
I->second,
TrialBBI1, TrialBBI2);
if (CommonTailLen >= minCommonTailLength) {
if (CommonTailLen > maxCommonTailLength) {
SameTails.clear();
maxCommonTailLength = CommonTailLen;
HighestMPIter = CurMPIter;
SameTails.push_back(std::make_pair(CurMPIter, TrialBBI1));
}
if (HighestMPIter == CurMPIter &&
CommonTailLen == maxCommonTailLength)
SameTails.push_back(std::make_pair(I, TrialBBI2));
}
if (I==B)
break;
}
}
// Build SameTails, identifying the set of blocks with this hash code
// and with the maximum number of instructions in common.
unsigned maxCommonTailLength = ComputeSameTails(CurHash,
minCommonTailLength);

// If we didn't find any pair that has at least minCommonTailLength
// instructions in common, remove all blocks with this hash code and retry.
if (SameTails.empty()) {
for (MPIterator CurMPIter = prior(MergePotentials.end()),
B = MergePotentials.begin();
CurMPIter->first==CurHash;
--CurMPIter) {
// Put the unconditional branch back, if we need one.
MachineBasicBlock *CurMBB = CurMPIter->second;
if (SuccBB && CurMBB != PredBB)
FixTail(CurMBB, SuccBB, TII);
MergePotentials.erase(CurMPIter);
if (CurMPIter==B)
break;
}
RemoveBlocksWithHash(CurHash, SuccBB, PredBB);
continue;
}

Expand Down Expand Up @@ -629,9 +652,9 @@ bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
// entry block, so if one block is the entry block, split the other one.

// The second half of the split block will remain in SameTails, and will
// consist entirely of common code. Thus in the case where there are multiple
// blocks that would all need to be split, the next iteration of the
// outer loop will handle all the rest of them.
// consist entirely of common code. Thus in the case where there are
// multiple blocks that would all need to be split, the next iteration of
// the outer loop will handle all the rest of them.

// Decide whether we want to split MBB1 or MBB2.
if (ShouldSplitFirstBlock(MBB1, BBI1, MBB2, BBI2, PredBB)) {
Expand Down Expand Up @@ -717,7 +740,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
// Failing case: IBB is the target of a cbr, and
// we cannot reverse the branch.
std::vector<MachineOperand> NewCond(Cond);
if (Cond.size() && TBB==IBB) {
if (!Cond.empty() && TBB==IBB) {
if (TII->ReverseBranchCondition(NewCond))
continue;
// This is the QBB case described above
Expand Down Expand Up @@ -747,9 +770,9 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
}
}
// Remove the unconditional branch at the end, if any.
if (TBB && (Cond.size()==0 || FBB)) {
if (TBB && (Cond.empty() || FBB)) {
TII->RemoveBranch(*PBB);
if (Cond.size())
if (!Cond.empty())
// reinsert conditional branch only, for now
TII->InsertBranch(*PBB, (TBB==IBB) ? FBB : TBB, 0, NewCond);
}
Expand Down

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