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Teach early dup how to duplicate basic blocks with one successor and only phi instructions

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into more complex blocks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133415 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2011-06-20 04:16:35 +00:00
parent b065b06c12
commit 275c1f9f93
1 changed files with 142 additions and 2 deletions
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144
lib/CodeGen/TailDuplication.cpp
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@ -96,6 +96,12 @@ namespace {
bool TailDuplicateBlocks(MachineFunction &MF);
bool shouldTailDuplicate(const MachineFunction &MF,
MachineBasicBlock &TailBB);
bool isSimpleBB(MachineBasicBlock *TailBB);
bool canCompletelyDuplicateSimpleBB(MachineBasicBlock &BB);
bool duplicateSimpleBB(MachineBasicBlock *TailBB,
SmallVector<MachineBasicBlock*, 8> &TDBBs,
const DenseSet<unsigned> &RegsUsedByPhi,
SmallVector<MachineInstr*, 16> &Copies);
bool TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF,
SmallVector<MachineBasicBlock*, 8> &TDBBs,
SmallVector<MachineInstr*, 16> &Copies);
@ -557,6 +563,136 @@ TailDuplicatePass::shouldTailDuplicate(const MachineFunction &MF,
return true;
}
/// isSimpleBB - True if this BB has only one unconditional jump.
bool
TailDuplicatePass::isSimpleBB(MachineBasicBlock *TailBB) {
if (TailBB->succ_size() != 1)
return false;
MachineBasicBlock::iterator I = TailBB->getFirstNonPHI();
MachineBasicBlock::iterator E = TailBB->end();
while (I->isDebugValue() && I != E)
++I;
if (I == E)
return true;
return I->getDesc().isUnconditionalBranch();
}
static bool
bothUsedInPHI(const MachineBasicBlock &A,
SmallPtrSet<MachineBasicBlock*, 8> SuccsB) {
for (MachineBasicBlock::const_succ_iterator SI = A.succ_begin(),
SE = A.succ_end(); SI != SE; ++SI) {
MachineBasicBlock *BB = *SI;
if (SuccsB.count(BB) && !BB->empty() && BB->begin()->isPHI())
return true;
}
return false;
}
bool
TailDuplicatePass::canCompletelyDuplicateSimpleBB(MachineBasicBlock &BB) {
SmallPtrSet<MachineBasicBlock*, 8> Succs(BB.succ_begin(), BB.succ_end());
for (MachineBasicBlock::pred_iterator PI = BB.pred_begin(),
PE = BB.pred_end(); PI != PE; ++PI) {
MachineBasicBlock *PredBB = *PI;
if (PredBB->getLandingPadSuccessor())
return false;
if (bothUsedInPHI(*PredBB, Succs))
return false;
MachineBasicBlock *PredTBB = NULL, *PredFBB = NULL;
SmallVector<MachineOperand, 4> PredCond;
if (TII->AnalyzeBranch(*PredBB, PredTBB, PredFBB, PredCond, true))
return false;
}
return true;
}
bool
TailDuplicatePass::duplicateSimpleBB(MachineBasicBlock *TailBB,
SmallVector<MachineBasicBlock*, 8> &TDBBs,
const DenseSet<unsigned> &UsedByPhi,
SmallVector<MachineInstr*, 16> &Copies) {
if (!canCompletelyDuplicateSimpleBB(*TailBB))
return false;
bool Changed = false;
SmallVector<MachineBasicBlock*, 8> Preds(TailBB->pred_begin(),
TailBB->pred_end());
for (SmallSetVector<MachineBasicBlock *, 8>::iterator PI = Preds.begin(),
PE = Preds.end(); PI != PE; ++PI) {
MachineBasicBlock *PredBB = *PI;
MachineBasicBlock *PredTBB = NULL, *PredFBB = NULL;
SmallVector<MachineOperand, 4> PredCond;
bool NotAnalyzable =
TII->AnalyzeBranch(*PredBB, PredTBB, PredFBB, PredCond, true);
(void)NotAnalyzable;
assert(!NotAnalyzable && "Cannot duplicate this!");
DEBUG(dbgs() << "\nTail-duplicating into PredBB: " << *PredBB
<< "From simple Succ: " << *TailBB);
MachineBasicBlock *NewTarget = *TailBB->succ_begin();
MachineBasicBlock *NextBB = next(MachineFunction::iterator(PredBB));
DenseMap<unsigned, unsigned> LocalVRMap;
SmallVector<std::pair<unsigned,unsigned>, 4> CopyInfos;
for (MachineBasicBlock::iterator I = TailBB->begin();
I != TailBB->end() && I->isPHI();) {
MachineInstr *MI = &*I;
++I;
ProcessPHI(MI, TailBB, PredBB, LocalVRMap, CopyInfos, UsedByPhi, true);
}
MachineBasicBlock::iterator Loc = PredBB->getFirstTerminator();
for (unsigned i = 0, e = CopyInfos.size(); i != e; ++i) {
Copies.push_back(BuildMI(*PredBB, Loc, DebugLoc(),
TII->get(TargetOpcode::COPY),
CopyInfos[i].first).addReg(CopyInfos[i].second));
}
// Make PredFBB explicit.
if (PredCond.empty())
PredFBB = PredTBB;
// Make fall through explicit.
if (!PredTBB)
PredTBB = NextBB;
if (!PredFBB)
PredFBB = NextBB;
// Redirect
if (PredFBB == TailBB)
PredFBB = NewTarget;
if (PredTBB == TailBB)
PredTBB = NewTarget;
// Make the branch unconditional if possible
if (PredTBB == PredFBB)
PredFBB = NULL;
// Avoid adding fall through branches.
if (PredFBB == NextBB)
PredFBB = NULL;
if (PredTBB == NextBB && PredFBB == NULL)
PredTBB = NULL;
TII->RemoveBranch(*PredBB);
if (PredTBB)
TII->InsertBranch(*PredBB, PredTBB, PredFBB, PredCond, DebugLoc());
PredBB->removeSuccessor(TailBB);
PredBB->addSuccessor(NewTarget);
TDBBs.push_back(PredBB);
Changed = true;
}
return Changed;
}
/// TailDuplicate - If it is profitable, duplicate TailBB's contents in each
/// of its predecessors.
bool
@ -568,14 +704,18 @@ TailDuplicatePass::TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF,
DEBUG(dbgs() << "\n*** Tail-duplicating BB#" << TailBB->getNumber() << '\n');
DenseSet<unsigned> UsedByPhi;
getRegsUsedByPHIs(*TailBB, &UsedByPhi);
if (isSimpleBB(TailBB))
return duplicateSimpleBB(TailBB, TDBBs, UsedByPhi, Copies);
// Iterate through all the unique predecessors and tail-duplicate this
// block into them, if possible. Copying the list ahead of time also
// avoids trouble with the predecessor list reallocating.
bool Changed = false;
SmallSetVector<MachineBasicBlock*, 8> Preds(TailBB->pred_begin(),
TailBB->pred_end());
DenseSet<unsigned> UsedByPhi;
getRegsUsedByPHIs(*TailBB, &UsedByPhi);
for (SmallSetVector<MachineBasicBlock *, 8>::iterator PI = Preds.begin(),
PE = Preds.end(); PI != PE; ++PI) {
MachineBasicBlock *PredBB = *PI;