}
}
+/// FoldBlockIntoPredecessor - Folds a basic block into its predecessor if it
+/// only has one predecessor, and that predecessor only has one successor.
+/// The LoopInfo Analysis that is passed will be kept consistent.
+/// Returns the new combined block.
+static BasicBlock *FoldBlockIntoPredecessor(BasicBlock *BB, LoopInfo* LI) {
+ // Merge basic blocks into their predecessor if there is only one distinct
+ // pred, and if there is only one distinct successor of the predecessor, and
+ // if there are no PHI nodes.
+ BasicBlock *OnlyPred = BB->getSinglePredecessor();
+ if (!OnlyPred) return 0;
+
+ if (OnlyPred->getTerminator()->getNumSuccessors() != 1)
+ return 0;
+
+ DEBUG(dbgs() << "Merging: " << *BB << "into: " << *OnlyPred);
+
+ // Resolve any PHI nodes at the start of the block. They are all
+ // guaranteed to have exactly one entry if they exist, unless there are
+ // multiple duplicate (but guaranteed to be equal) entries for the
+ // incoming edges. This occurs when there are multiple edges from
+ // OnlyPred to OnlySucc.
+ FoldSingleEntryPHINodes(BB);
+
+ // Delete the unconditional branch from the predecessor...
+ OnlyPred->getInstList().pop_back();
+
+ // Move all definitions in the successor to the predecessor...
+ OnlyPred->getInstList().splice(OnlyPred->end(), BB->getInstList());
+
+ // Make all PHI nodes that referred to BB now refer to Pred as their
+ // source...
+ BB->replaceAllUsesWith(OnlyPred);
+
+ std::string OldName = BB->getName();
+
+ // Erase basic block from the function...
+ LI->removeBlock(BB);
+ BB->eraseFromParent();
+
+ // Inherit predecessor's name if it exists...
+ if (!OldName.empty() && !OnlyPred->hasName())
+ OnlyPred->setName(OldName);
+
+ return OnlyPred;
+}
+
/// Unroll the given loop by Count. The loop must be in LCSSA form. Returns true
/// if unrolling was succesful, or false if the loop was unmodified. Unrolling
/// can only fail when the loop's latch block is not terminated by a conditional
bool llvm::UnrollLoop(Loop *L, unsigned Count, LoopInfo* LI, LPPassManager* LPM) {
assert(L->isLCSSAForm());
- BasicBlock *Header = L->getHeader();
+ BasicBlock *Preheader = L->getLoopPreheader();
+ if (!Preheader) {
+ DEBUG(dbgs() << " Can't unroll; loop preheader-insertion failed.\n");
+ return false;
+ }
+
BasicBlock *LatchBlock = L->getLoopLatch();
+ if (!LatchBlock) {
+ DEBUG(dbgs() << " Can't unroll; loop exit-block-insertion failed.\n");
+ return false;
+ }
+
+ BasicBlock *Header = L->getHeader();
BranchInst *BI = dyn_cast<BranchInst>(LatchBlock->getTerminator());
if (!BI || BI->isUnconditional()) {
// The loop-rotate pass can be helpful to avoid this in many cases.
- DEBUG(errs() <<
+ DEBUG(dbgs() <<
" Can't unroll; loop not terminated by a conditional branch.\n");
return false;
}
TripMultiple = L->getSmallConstantTripMultiple();
if (TripCount != 0)
- DEBUG(errs() << " Trip Count = " << TripCount << "\n");
+ DEBUG(dbgs() << " Trip Count = " << TripCount << "\n");
if (TripMultiple != 1)
- DEBUG(errs() << " Trip Multiple = " << TripMultiple << "\n");
+ DEBUG(dbgs() << " Trip Multiple = " << TripMultiple << "\n");
// Effectively "DCE" unrolled iterations that are beyond the tripcount
// and will never be executed.
}
if (CompletelyUnroll) {
- DEBUG(errs() << "COMPLETELY UNROLLING loop %" << Header->getName()
+ DEBUG(dbgs() << "COMPLETELY UNROLLING loop %" << Header->getName()
<< " with trip count " << TripCount << "!\n");
} else {
- DEBUG(errs() << "UNROLLING loop %" << Header->getName()
+ DEBUG(dbgs() << "UNROLLING loop %" << Header->getName()
<< " by " << Count);
if (TripMultiple == 0 || BreakoutTrip != TripMultiple) {
- DEBUG(errs() << " with a breakout at trip " << BreakoutTrip);
+ DEBUG(dbgs() << " with a breakout at trip " << BreakoutTrip);
} else if (TripMultiple != 1) {
- DEBUG(errs() << " with " << TripMultiple << " trips per branch");
+ DEBUG(dbgs() << " with " << TripMultiple << " trips per branch");
}
- DEBUG(errs() << "!\n");
+ DEBUG(dbgs() << "!\n");
}
std::vector<BasicBlock*> LoopBlocks = L->getBlocks();
OrigPHINode.push_back(PN);
if (Instruction *I =
dyn_cast<Instruction>(PN->getIncomingValueForBlock(LatchBlock)))
- if (L->contains(I->getParent()))
+ if (L->contains(I))
LastValueMap[I] = I;
}
PHINode *NewPHI = cast<PHINode>(ValueMap[OrigPHINode[i]]);
Value *InVal = NewPHI->getIncomingValueForBlock(LatchBlock);
if (Instruction *InValI = dyn_cast<Instruction>(InVal))
- if (It > 1 && L->contains(InValI->getParent()))
+ if (It > 1 && L->contains(InValI))
InVal = LastValueMap[InValI];
ValueMap[OrigPHINode[i]] = InVal;
New->getInstList().erase(NewPHI);
UI != UE;) {
Instruction *UseInst = cast<Instruction>(*UI);
++UI;
- if (isa<PHINode>(UseInst) && !L->contains(UseInst->getParent())) {
+ if (isa<PHINode>(UseInst) && !L->contains(UseInst)) {
PHINode *phi = cast<PHINode>(UseInst);
Value *Incoming = phi->getIncomingValueForBlock(*BB);
phi->addIncoming(Incoming, New);
// If this value was defined in the loop, take the value defined by the
// last iteration of the loop.
if (Instruction *InValI = dyn_cast<Instruction>(InVal)) {
- if (L->contains(InValI->getParent()))
+ if (L->contains(InValI))
InVal = LastValueMap[InVal];
}
PN->addIncoming(InVal, LastIterationBB);
} else {
Term->setUnconditionalDest(Dest);
// Merge adjacent basic blocks, if possible.
- if (BasicBlock *Fold = MergeBlockIntoPredecessor(Dest, LI)) {
+ if (BasicBlock *Fold = FoldBlockIntoPredecessor(Dest, LI)) {
std::replace(Latches.begin(), Latches.end(), Dest, Fold);
std::replace(Headers.begin(), Headers.end(), Dest, Fold);
}
if (isInstructionTriviallyDead(Inst))
(*BB)->getInstList().erase(Inst);
- else if (Constant *C = ConstantFoldInstruction(Inst,
- Header->getContext())) {
+ else if (Constant *C = ConstantFoldInstruction(Inst)) {
Inst->replaceAllUsesWith(C);
(*BB)->getInstList().erase(Inst);
}
projects / oota-llvm.git / blobdiff