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Allow small blocks to be duplicated to enable if-conversion.

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llvm-svn: 37590
This commit is contained in:
Evan Cheng 2007-06-15 07:36:12 +00:00
parent 3a979f2fa5
commit f4d3d695b2
1 changed files with 100 additions and 26 deletions
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126
lib/CodeGen/IfConversion.cpp
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@ -54,6 +54,7 @@ STATISTIC(NumTriangleFalse,"Number of triangle (F) if-conversions performed");
STATISTIC(NumTriangleFRev, "Number of triangle (F/R) if-conversions performed");
STATISTIC(NumDiamonds, "Number of diamond if-conversions performed");
STATISTIC(NumIfConvBBs, "Number of if-converted blocks");
STATISTIC(NumDupBBs, "Number of duplicated blocks");
namespace {
class IfConverter : public MachineFunctionPass {
@ -153,7 +154,10 @@ namespace {
void PredicateBlock(BBInfo &BBI,
std::vector<MachineOperand> &Cond,
bool IgnoreTerm = false);
void MergeBlocks(BBInfo &TrueBBI, BBInfo &FalseBBI);
void CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
std::vector<MachineOperand> &Cond,
bool IgnoreBr = false);
void MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI);
// blockAlwaysFallThrough - Block ends without a terminator.
bool blockAlwaysFallThrough(BBInfo &BBI) const {
@ -196,7 +200,9 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
std::vector<BBInfo*> Candidates;
MadeChange = false;
while (IfCvtLimit == -1 || (int)NumIfConvBBs < IfCvtLimit) {
unsigned NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle +
NumTriangleRev + NumTriangleFalse + NumTriangleFRev + NumDiamonds;
while (IfCvtLimit == -1 || (int)NumIfCvts < IfCvtLimit) {
// Do an intial analysis for each basic block and finding all the potential
// candidates to perform if-convesion.
bool Change = AnalyzeBlocks(MF, Candidates);
@ -274,7 +280,9 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
}
Change |= RetVal;
if (IfCvtLimit != -1 && (int)NumIfConvBBs >= IfCvtLimit)
NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle + NumTriangleRev +
NumTriangleFalse + NumTriangleFRev + NumDiamonds;
if (IfCvtLimit != -1 && (int)NumIfCvts >= IfCvtLimit)
break;
}
@ -326,8 +334,12 @@ bool IfConverter::ValidSimple(BBInfo &TrueBBI) const {
if (TrueBBI.IsBeingAnalyzed)
return false;
return !blockAlwaysFallThrough(TrueBBI) &&
TrueBBI.BrCond.size() == 0 && TrueBBI.BB->pred_size() == 1;
if (TrueBBI.BB->pred_size() != 1) {
if (TrueBBI.NonPredSize > TLI->getIfCvtDupBlockSizeLimit())
return false;
}
return !blockAlwaysFallThrough(TrueBBI) && TrueBBI.BrCond.size() == 0;
}
/// ValidTriangle - Returns true if the 'true' and 'false' blocks (along
@ -337,8 +349,13 @@ bool IfConverter::ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
if (TrueBBI.IsBeingAnalyzed)
return false;
if (TrueBBI.BB->pred_size() != 1)
return false;
if (TrueBBI.BB->pred_size() != 1) {
unsigned Size = TrueBBI.NonPredSize;
if (TrueBBI.FalseBB)
++Size;
if (Size > TLI->getIfCvtDupBlockSizeLimit())
return false;
}
MachineBasicBlock *TExit = FalseBranch ? TrueBBI.FalseBB : TrueBBI.TrueBB;
if (!TExit && blockAlwaysFallThrough(TrueBBI)) {
@ -709,11 +726,18 @@ bool IfConverter::IfConvertSimple(BBInfo &BBI) {
TII->ReverseBranchCondition(Cond);
}
PredicateBlock(*CvtBBI, Cond);
if (CvtBBI->BB->pred_size() > 1) {
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
// Copy instructions in the true block, predicate them add them to
// the entry block.
CopyAndPredicateBlock(BBI, *CvtBBI, Cond);
} else {
PredicateBlock(*CvtBBI, Cond);
// Merge converted block into entry block.
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
MergeBlocks(BBI, *CvtBBI);
// Merge converted block into entry block.
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
MergeBlocks(BBI, *CvtBBI);
}
bool IterIfcvt = true;
if (!canFallThroughTo(BBI.BB, NextBBI->BB)) {
@ -775,22 +799,38 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
}
}
// Predicate the 'true' block after removing its branch.
CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB);
PredicateBlock(*CvtBBI, Cond);
bool HasEarlyExit = CvtBBI->FalseBB != NULL;
bool DupBB = CvtBBI->BB->pred_size() > 1;
if (DupBB) {
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
// Copy instructions in the true block, predicate them add them to
// the entry block.
CopyAndPredicateBlock(BBI, *CvtBBI, Cond, true);
BBI.BB->removeSuccessor(CvtBBI->BB);
} else {
// Predicate the 'true' block after removing its branch.
CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB);
PredicateBlock(*CvtBBI, Cond);
}
// If 'true' block has a 'false' successor, add an exit branch to it.
bool HasEarlyExit = CvtBBI->FalseBB != NULL;
if (HasEarlyExit) {
std::vector<MachineOperand> RevCond(CvtBBI->BrCond);
if (TII->ReverseBranchCondition(RevCond))
assert(false && "Unable to reverse branch condition!");
TII->InsertBranch(*CvtBBI->BB, CvtBBI->FalseBB, NULL, RevCond);
if (DupBB) {
TII->InsertBranch(*BBI.BB, CvtBBI->FalseBB, NULL, RevCond);
BBI.BB->addSuccessor(CvtBBI->FalseBB);
} else {
TII->InsertBranch(*CvtBBI->BB, CvtBBI->FalseBB, NULL, RevCond);
}
}
// Now merge the entry of the triangle with the true block.
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
MergeBlocks(BBI, *CvtBBI);
if (!DupBB) {
// Now merge the entry of the triangle with the true block.
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
MergeBlocks(BBI, *CvtBBI);
}
// Merge in the 'false' block if the 'false' block has no other
// predecessors. Otherwise, add a unconditional branch from to 'false'.
@ -970,13 +1010,48 @@ void IfConverter::PredicateBlock(BBInfo &BBI,
}
}
BBI.IsAnalyzed = false;
BBI.NonPredSize = 0;
std::copy(Cond.begin(), Cond.end(), std::back_inserter(BBI.Predicate));
BBI.IsAnalyzed = false;
BBI.NonPredSize = 0;
NumIfConvBBs++;
}
/// CopyAndPredicateBlock - Copy and predicate instructions from source BB to
/// the destination block. Skip end of block branches if IgnoreBr is true.
void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
std::vector<MachineOperand> &Cond,
bool IgnoreBr) {
for (MachineBasicBlock::iterator I = FromBBI.BB->begin(),
E = FromBBI.BB->end(); I != E; ++I) {
const TargetInstrDescriptor *TID = I->getInstrDescriptor();
bool isPredicated = TII->isPredicated(I);
// Do not copy the end of the block branches.
if (IgnoreBr && !isPredicated && (TID->Flags & M_BRANCH_FLAG) != 0)
break;
MachineInstr *MI = I->clone();
ToBBI.BB->insert(ToBBI.BB->end(), MI);
ToBBI.NonPredSize++;
if (!isPredicated)
if (!TII->PredicateInstruction(MI, Cond)) {
cerr << "Unable to predicate " << *MI << "!\n";
abort();
}
}
std::copy(FromBBI.Predicate.begin(), FromBBI.Predicate.end(),
std::back_inserter(ToBBI.Predicate));
std::copy(Cond.begin(), Cond.end(), std::back_inserter(ToBBI.Predicate));
ToBBI.ClobbersPred |= FromBBI.ClobbersPred;
ToBBI.IsAnalyzed = false;
NumDupBBs++;
}
/// MergeBlocks - Move all instructions from FromBB to the end of ToBB.
///
void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI) {
@ -1012,16 +1087,15 @@ void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI) {
if (NBB)
FromBBI.BB->addSuccessor(NBB);
std::copy(FromBBI.Predicate.begin(), FromBBI.Predicate.end(),
std::back_inserter(ToBBI.Predicate));
FromBBI.Predicate.clear();
ToBBI.NonPredSize += FromBBI.NonPredSize;
FromBBI.NonPredSize = 0;
ToBBI.ClobbersPred |= FromBBI.ClobbersPred;
ToBBI.HasFallThrough = FromBBI.HasFallThrough;
std::copy(FromBBI.Predicate.begin(), FromBBI.Predicate.end(),
std::back_inserter(ToBBI.Predicate));
FromBBI.Predicate.clear();
ToBBI.IsAnalyzed = false;
FromBBI.IsAnalyzed = false;
}