diff options
Diffstat (limited to 'contrib/llvm/lib/CodeGen/MachineBlockPlacement.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/MachineBlockPlacement.cpp | 360 |
1 files changed, 307 insertions, 53 deletions
diff --git a/contrib/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/contrib/llvm/lib/CodeGen/MachineBlockPlacement.cpp index 2969bad4ff98..f5e305645011 100644 --- a/contrib/llvm/lib/CodeGen/MachineBlockPlacement.cpp +++ b/contrib/llvm/lib/CodeGen/MachineBlockPlacement.cpp @@ -51,7 +51,7 @@ using namespace llvm; #define DEBUG_TYPE "block-placement" STATISTIC(NumCondBranches, "Number of conditional branches"); -STATISTIC(NumUncondBranches, "Number of uncondittional branches"); +STATISTIC(NumUncondBranches, "Number of unconditional branches"); STATISTIC(CondBranchTakenFreq, "Potential frequency of taking conditional branches"); STATISTIC(UncondBranchTakenFreq, @@ -62,6 +62,11 @@ static cl::opt<unsigned> AlignAllBlock("align-all-blocks", "blocks in the function."), cl::init(0), cl::Hidden); +static cl::opt<unsigned> + AlignAllLoops("align-all-loops", + cl::desc("Force the alignment of all loops in the function."), + cl::init(0), cl::Hidden); + // FIXME: Find a good default for this flag and remove the flag. static cl::opt<unsigned> ExitBlockBias( "block-placement-exit-block-bias", @@ -81,6 +86,29 @@ static cl::opt<unsigned> OutlineOptionalThreshold( "instruction count below this threshold"), cl::init(4), cl::Hidden); +static cl::opt<unsigned> LoopToColdBlockRatio( + "loop-to-cold-block-ratio", + cl::desc("Outline loop blocks from loop chain if (frequency of loop) / " + "(frequency of block) is greater than this ratio"), + cl::init(5), cl::Hidden); + +static cl::opt<bool> + PreciseRotationCost("precise-rotation-cost", + cl::desc("Model the cost of loop rotation more " + "precisely by using profile data."), + cl::init(false), cl::Hidden); + +static cl::opt<unsigned> MisfetchCost( + "misfetch-cost", + cl::desc("Cost that models the probablistic risk of an instruction " + "misfetch due to a jump comparing to falling through, whose cost " + "is zero."), + cl::init(1), cl::Hidden); + +static cl::opt<unsigned> JumpInstCost("jump-inst-cost", + cl::desc("Cost of jump instructions."), + cl::init(1), cl::Hidden); + namespace { class BlockChain; /// \brief Type for our function-wide basic block -> block chain mapping. @@ -246,9 +274,12 @@ class MachineBlockPlacement : public MachineFunctionPass { const BlockFilterSet &LoopBlockSet); MachineBasicBlock *findBestLoopExit(MachineFunction &F, MachineLoop &L, const BlockFilterSet &LoopBlockSet); + BlockFilterSet collectLoopBlockSet(MachineFunction &F, MachineLoop &L); void buildLoopChains(MachineFunction &F, MachineLoop &L); void rotateLoop(BlockChain &LoopChain, MachineBasicBlock *ExitingBB, const BlockFilterSet &LoopBlockSet); + void rotateLoopWithProfile(BlockChain &LoopChain, MachineLoop &L, + const BlockFilterSet &LoopBlockSet); void buildCFGChains(MachineFunction &F); public: @@ -354,31 +385,56 @@ MachineBlockPlacement::selectBestSuccessor(MachineBasicBlock *BB, const BranchProbability HotProb(4, 5); // 80% MachineBasicBlock *BestSucc = nullptr; - // FIXME: Due to the performance of the probability and weight routines in - // the MBPI analysis, we manually compute probabilities using the edge - // weights. This is suboptimal as it means that the somewhat subtle - // definition of edge weight semantics is encoded here as well. We should - // improve the MBPI interface to efficiently support query patterns such as - // this. - uint32_t BestWeight = 0; - uint32_t WeightScale = 0; - uint32_t SumWeight = MBPI->getSumForBlock(BB, WeightScale); - DEBUG(dbgs() << "Attempting merge from: " << getBlockName(BB) << "\n"); + auto BestProb = BranchProbability::getZero(); + + // Adjust edge probabilities by excluding edges pointing to blocks that is + // either not in BlockFilter or is already in the current chain. Consider the + // following CFG: + // + // --->A + // | / \ + // | B C + // | \ / \ + // ----D E + // + // Assume A->C is very hot (>90%), and C->D has a 50% probability, then after + // A->C is chosen as a fall-through, D won't be selected as a successor of C + // due to CFG constraint (the probability of C->D is not greater than + // HotProb). If we exclude E that is not in BlockFilter when calculating the + // probability of C->D, D will be selected and we will get A C D B as the + // layout of this loop. + auto AdjustedSumProb = BranchProbability::getOne(); + SmallVector<MachineBasicBlock *, 4> Successors; for (MachineBasicBlock *Succ : BB->successors()) { - if (BlockFilter && !BlockFilter->count(Succ)) - continue; - BlockChain &SuccChain = *BlockToChain[Succ]; - if (&SuccChain == &Chain) { - DEBUG(dbgs() << " " << getBlockName(Succ) << " -> Already merged!\n"); - continue; - } - if (Succ != *SuccChain.begin()) { - DEBUG(dbgs() << " " << getBlockName(Succ) << " -> Mid chain!\n"); - continue; + bool SkipSucc = false; + if (BlockFilter && !BlockFilter->count(Succ)) { + SkipSucc = true; + } else { + BlockChain *SuccChain = BlockToChain[Succ]; + if (SuccChain == &Chain) { + DEBUG(dbgs() << " " << getBlockName(Succ) + << " -> Already merged!\n"); + SkipSucc = true; + } else if (Succ != *SuccChain->begin()) { + DEBUG(dbgs() << " " << getBlockName(Succ) << " -> Mid chain!\n"); + continue; + } } + if (SkipSucc) + AdjustedSumProb -= MBPI->getEdgeProbability(BB, Succ); + else + Successors.push_back(Succ); + } - uint32_t SuccWeight = MBPI->getEdgeWeight(BB, Succ); - BranchProbability SuccProb(SuccWeight / WeightScale, SumWeight); + DEBUG(dbgs() << "Attempting merge from: " << getBlockName(BB) << "\n"); + for (MachineBasicBlock *Succ : Successors) { + BranchProbability SuccProb; + uint32_t SuccProbN = MBPI->getEdgeProbability(BB, Succ).getNumerator(); + uint32_t SuccProbD = AdjustedSumProb.getNumerator(); + if (SuccProbN >= SuccProbD) + SuccProb = BranchProbability::getOne(); + else + SuccProb = BranchProbability(SuccProbN, SuccProbD); // If we outline optional branches, look whether Succ is unavoidable, i.e. // dominates all terminators of the MachineFunction. If it does, other @@ -406,6 +462,7 @@ MachineBlockPlacement::selectBestSuccessor(MachineBasicBlock *BB, // Only consider successors which are either "hot", or wouldn't violate // any CFG constraints. + BlockChain &SuccChain = *BlockToChain[Succ]; if (SuccChain.LoopPredecessors != 0) { if (SuccProb < HotProb) { DEBUG(dbgs() << " " << getBlockName(Succ) << " -> " << SuccProb @@ -415,8 +472,9 @@ MachineBlockPlacement::selectBestSuccessor(MachineBasicBlock *BB, // Make sure that a hot successor doesn't have a globally more // important predecessor. + auto RealSuccProb = MBPI->getEdgeProbability(BB, Succ); BlockFrequency CandidateEdgeFreq = - MBFI->getBlockFreq(BB) * SuccProb * HotProb.getCompl(); + MBFI->getBlockFreq(BB) * RealSuccProb * HotProb.getCompl(); bool BadCFGConflict = false; for (MachineBasicBlock *Pred : Succ->predecessors()) { if (Pred == Succ || (BlockFilter && !BlockFilter->count(Pred)) || @@ -440,10 +498,10 @@ MachineBlockPlacement::selectBestSuccessor(MachineBasicBlock *BB, << " (prob)" << (SuccChain.LoopPredecessors != 0 ? " (CFG break)" : "") << "\n"); - if (BestSucc && BestWeight >= SuccWeight) + if (BestSucc && BestProb >= SuccProb) continue; BestSucc = Succ; - BestWeight = SuccWeight; + BestProb = SuccProb; } return BestSucc; } @@ -505,14 +563,14 @@ MachineBasicBlock *MachineBlockPlacement::getFirstUnplacedBlock( const BlockFilterSet *BlockFilter) { for (MachineFunction::iterator I = PrevUnplacedBlockIt, E = F.end(); I != E; ++I) { - if (BlockFilter && !BlockFilter->count(I)) + if (BlockFilter && !BlockFilter->count(&*I)) continue; - if (BlockToChain[I] != &PlacedChain) { + if (BlockToChain[&*I] != &PlacedChain) { PrevUnplacedBlockIt = I; // Now select the head of the chain to which the unplaced block belongs // as the block to place. This will force the entire chain to be placed, // and satisfies the requirements of merging chains. - return *BlockToChain[I]->begin(); + return *BlockToChain[&*I]->begin(); } } return nullptr; @@ -672,13 +730,8 @@ MachineBlockPlacement::findBestLoopExit(MachineFunction &F, MachineLoop &L, MachineBasicBlock *OldExitingBB = ExitingBB; BlockFrequency OldBestExitEdgeFreq = BestExitEdgeFreq; bool HasLoopingSucc = false; - // FIXME: Due to the performance of the probability and weight routines in - // the MBPI analysis, we use the internal weights and manually compute the - // probabilities to avoid quadratic behavior. - uint32_t WeightScale = 0; - uint32_t SumWeight = MBPI->getSumForBlock(MBB, WeightScale); for (MachineBasicBlock *Succ : MBB->successors()) { - if (Succ->isLandingPad()) + if (Succ->isEHPad()) continue; if (Succ == MBB) continue; @@ -690,10 +743,10 @@ MachineBlockPlacement::findBestLoopExit(MachineFunction &F, MachineLoop &L, continue; } - uint32_t SuccWeight = MBPI->getEdgeWeight(MBB, Succ); + auto SuccProb = MBPI->getEdgeProbability(MBB, Succ); if (LoopBlockSet.count(Succ)) { DEBUG(dbgs() << " looping: " << getBlockName(MBB) << " -> " - << getBlockName(Succ) << " (" << SuccWeight << ")\n"); + << getBlockName(Succ) << " (" << SuccProb << ")\n"); HasLoopingSucc = true; continue; } @@ -705,7 +758,6 @@ MachineBlockPlacement::findBestLoopExit(MachineFunction &F, MachineLoop &L, BlocksExitingToOuterLoop.insert(MBB); } - BranchProbability SuccProb(SuccWeight / WeightScale, SumWeight); BlockFrequency ExitEdgeFreq = MBFI->getBlockFreq(MBB) * SuccProb; DEBUG(dbgs() << " exiting: " << getBlockName(MBB) << " -> " << getBlockName(Succ) << " [L:" << SuccLoopDepth << "] ("; @@ -791,6 +843,188 @@ void MachineBlockPlacement::rotateLoop(BlockChain &LoopChain, std::rotate(LoopChain.begin(), std::next(ExitIt), LoopChain.end()); } +/// \brief Attempt to rotate a loop based on profile data to reduce branch cost. +/// +/// With profile data, we can determine the cost in terms of missed fall through +/// opportunities when rotating a loop chain and select the best rotation. +/// Basically, there are three kinds of cost to consider for each rotation: +/// 1. The possibly missed fall through edge (if it exists) from BB out of +/// the loop to the loop header. +/// 2. The possibly missed fall through edges (if they exist) from the loop +/// exits to BB out of the loop. +/// 3. The missed fall through edge (if it exists) from the last BB to the +/// first BB in the loop chain. +/// Therefore, the cost for a given rotation is the sum of costs listed above. +/// We select the best rotation with the smallest cost. +void MachineBlockPlacement::rotateLoopWithProfile( + BlockChain &LoopChain, MachineLoop &L, const BlockFilterSet &LoopBlockSet) { + auto HeaderBB = L.getHeader(); + auto HeaderIter = std::find(LoopChain.begin(), LoopChain.end(), HeaderBB); + auto RotationPos = LoopChain.end(); + + BlockFrequency SmallestRotationCost = BlockFrequency::getMaxFrequency(); + + // A utility lambda that scales up a block frequency by dividing it by a + // branch probability which is the reciprocal of the scale. + auto ScaleBlockFrequency = [](BlockFrequency Freq, + unsigned Scale) -> BlockFrequency { + if (Scale == 0) + return 0; + // Use operator / between BlockFrequency and BranchProbability to implement + // saturating multiplication. + return Freq / BranchProbability(1, Scale); + }; + + // Compute the cost of the missed fall-through edge to the loop header if the + // chain head is not the loop header. As we only consider natural loops with + // single header, this computation can be done only once. + BlockFrequency HeaderFallThroughCost(0); + for (auto *Pred : HeaderBB->predecessors()) { + BlockChain *PredChain = BlockToChain[Pred]; + if (!LoopBlockSet.count(Pred) && + (!PredChain || Pred == *std::prev(PredChain->end()))) { + auto EdgeFreq = + MBFI->getBlockFreq(Pred) * MBPI->getEdgeProbability(Pred, HeaderBB); + auto FallThruCost = ScaleBlockFrequency(EdgeFreq, MisfetchCost); + // If the predecessor has only an unconditional jump to the header, we + // need to consider the cost of this jump. + if (Pred->succ_size() == 1) + FallThruCost += ScaleBlockFrequency(EdgeFreq, JumpInstCost); + HeaderFallThroughCost = std::max(HeaderFallThroughCost, FallThruCost); + } + } + + // Here we collect all exit blocks in the loop, and for each exit we find out + // its hottest exit edge. For each loop rotation, we define the loop exit cost + // as the sum of frequencies of exit edges we collect here, excluding the exit + // edge from the tail of the loop chain. + SmallVector<std::pair<MachineBasicBlock *, BlockFrequency>, 4> ExitsWithFreq; + for (auto BB : LoopChain) { + auto LargestExitEdgeProb = BranchProbability::getZero(); + for (auto *Succ : BB->successors()) { + BlockChain *SuccChain = BlockToChain[Succ]; + if (!LoopBlockSet.count(Succ) && + (!SuccChain || Succ == *SuccChain->begin())) { + auto SuccProb = MBPI->getEdgeProbability(BB, Succ); + LargestExitEdgeProb = std::max(LargestExitEdgeProb, SuccProb); + } + } + if (LargestExitEdgeProb > BranchProbability::getZero()) { + auto ExitFreq = MBFI->getBlockFreq(BB) * LargestExitEdgeProb; + ExitsWithFreq.emplace_back(BB, ExitFreq); + } + } + + // In this loop we iterate every block in the loop chain and calculate the + // cost assuming the block is the head of the loop chain. When the loop ends, + // we should have found the best candidate as the loop chain's head. + for (auto Iter = LoopChain.begin(), TailIter = std::prev(LoopChain.end()), + EndIter = LoopChain.end(); + Iter != EndIter; Iter++, TailIter++) { + // TailIter is used to track the tail of the loop chain if the block we are + // checking (pointed by Iter) is the head of the chain. + if (TailIter == LoopChain.end()) + TailIter = LoopChain.begin(); + + auto TailBB = *TailIter; + + // Calculate the cost by putting this BB to the top. + BlockFrequency Cost = 0; + + // If the current BB is the loop header, we need to take into account the + // cost of the missed fall through edge from outside of the loop to the + // header. + if (Iter != HeaderIter) + Cost += HeaderFallThroughCost; + + // Collect the loop exit cost by summing up frequencies of all exit edges + // except the one from the chain tail. + for (auto &ExitWithFreq : ExitsWithFreq) + if (TailBB != ExitWithFreq.first) + Cost += ExitWithFreq.second; + + // The cost of breaking the once fall-through edge from the tail to the top + // of the loop chain. Here we need to consider three cases: + // 1. If the tail node has only one successor, then we will get an + // additional jmp instruction. So the cost here is (MisfetchCost + + // JumpInstCost) * tail node frequency. + // 2. If the tail node has two successors, then we may still get an + // additional jmp instruction if the layout successor after the loop + // chain is not its CFG successor. Note that the more frequently executed + // jmp instruction will be put ahead of the other one. Assume the + // frequency of those two branches are x and y, where x is the frequency + // of the edge to the chain head, then the cost will be + // (x * MisfetechCost + min(x, y) * JumpInstCost) * tail node frequency. + // 3. If the tail node has more than two successors (this rarely happens), + // we won't consider any additional cost. + if (TailBB->isSuccessor(*Iter)) { + auto TailBBFreq = MBFI->getBlockFreq(TailBB); + if (TailBB->succ_size() == 1) + Cost += ScaleBlockFrequency(TailBBFreq.getFrequency(), + MisfetchCost + JumpInstCost); + else if (TailBB->succ_size() == 2) { + auto TailToHeadProb = MBPI->getEdgeProbability(TailBB, *Iter); + auto TailToHeadFreq = TailBBFreq * TailToHeadProb; + auto ColderEdgeFreq = TailToHeadProb > BranchProbability(1, 2) + ? TailBBFreq * TailToHeadProb.getCompl() + : TailToHeadFreq; + Cost += ScaleBlockFrequency(TailToHeadFreq, MisfetchCost) + + ScaleBlockFrequency(ColderEdgeFreq, JumpInstCost); + } + } + + DEBUG(dbgs() << "The cost of loop rotation by making " << getBlockNum(*Iter) + << " to the top: " << Cost.getFrequency() << "\n"); + + if (Cost < SmallestRotationCost) { + SmallestRotationCost = Cost; + RotationPos = Iter; + } + } + + if (RotationPos != LoopChain.end()) { + DEBUG(dbgs() << "Rotate loop by making " << getBlockNum(*RotationPos) + << " to the top\n"); + std::rotate(LoopChain.begin(), RotationPos, LoopChain.end()); + } +} + +/// \brief Collect blocks in the given loop that are to be placed. +/// +/// When profile data is available, exclude cold blocks from the returned set; +/// otherwise, collect all blocks in the loop. +MachineBlockPlacement::BlockFilterSet +MachineBlockPlacement::collectLoopBlockSet(MachineFunction &F, MachineLoop &L) { + BlockFilterSet LoopBlockSet; + + // Filter cold blocks off from LoopBlockSet when profile data is available. + // Collect the sum of frequencies of incoming edges to the loop header from + // outside. If we treat the loop as a super block, this is the frequency of + // the loop. Then for each block in the loop, we calculate the ratio between + // its frequency and the frequency of the loop block. When it is too small, + // don't add it to the loop chain. If there are outer loops, then this block + // will be merged into the first outer loop chain for which this block is not + // cold anymore. This needs precise profile data and we only do this when + // profile data is available. + if (F.getFunction()->getEntryCount()) { + BlockFrequency LoopFreq(0); + for (auto LoopPred : L.getHeader()->predecessors()) + if (!L.contains(LoopPred)) + LoopFreq += MBFI->getBlockFreq(LoopPred) * + MBPI->getEdgeProbability(LoopPred, L.getHeader()); + + for (MachineBasicBlock *LoopBB : L.getBlocks()) { + auto Freq = MBFI->getBlockFreq(LoopBB).getFrequency(); + if (Freq == 0 || LoopFreq.getFrequency() / Freq > LoopToColdBlockRatio) + continue; + LoopBlockSet.insert(LoopBB); + } + } else + LoopBlockSet.insert(L.block_begin(), L.block_end()); + + return LoopBlockSet; +} + /// \brief Forms basic block chains from the natural loop structures. /// /// These chains are designed to preserve the existing *structure* of the code @@ -805,19 +1039,27 @@ void MachineBlockPlacement::buildLoopChains(MachineFunction &F, buildLoopChains(F, *InnerLoop); SmallVector<MachineBasicBlock *, 16> BlockWorkList; - BlockFilterSet LoopBlockSet(L.block_begin(), L.block_end()); + BlockFilterSet LoopBlockSet = collectLoopBlockSet(F, L); + + // Check if we have profile data for this function. If yes, we will rotate + // this loop by modeling costs more precisely which requires the profile data + // for better layout. + bool RotateLoopWithProfile = + PreciseRotationCost && F.getFunction()->getEntryCount(); // First check to see if there is an obviously preferable top block for the // loop. This will default to the header, but may end up as one of the // predecessors to the header if there is one which will result in strictly // fewer branches in the loop body. - MachineBasicBlock *LoopTop = findBestLoopTop(L, LoopBlockSet); + // When we use profile data to rotate the loop, this is unnecessary. + MachineBasicBlock *LoopTop = + RotateLoopWithProfile ? L.getHeader() : findBestLoopTop(L, LoopBlockSet); // If we selected just the header for the loop top, look for a potentially // profitable exit block in the event that rotating the loop can eliminate // branches by placing an exit edge at the bottom. MachineBasicBlock *ExitingBB = nullptr; - if (LoopTop == L.getHeader()) + if (!RotateLoopWithProfile && LoopTop == L.getHeader()) ExitingBB = findBestLoopExit(F, L, LoopBlockSet); BlockChain &LoopChain = *BlockToChain[LoopTop]; @@ -828,7 +1070,8 @@ void MachineBlockPlacement::buildLoopChains(MachineFunction &F, SmallPtrSet<BlockChain *, 4> UpdatedPreds; assert(LoopChain.LoopPredecessors == 0); UpdatedPreds.insert(&LoopChain); - for (MachineBasicBlock *LoopBB : L.getBlocks()) { + + for (MachineBasicBlock *LoopBB : LoopBlockSet) { BlockChain &Chain = *BlockToChain[LoopBB]; if (!UpdatedPreds.insert(&Chain).second) continue; @@ -848,7 +1091,11 @@ void MachineBlockPlacement::buildLoopChains(MachineFunction &F, } buildChain(LoopTop, LoopChain, BlockWorkList, &LoopBlockSet); - rotateLoop(LoopChain, ExitingBB, LoopBlockSet); + + if (RotateLoopWithProfile) + rotateLoopWithProfile(LoopChain, L, LoopBlockSet); + else + rotateLoop(LoopChain, ExitingBB, LoopBlockSet); DEBUG({ // Crash at the end so we get all of the debugging output first. @@ -889,7 +1136,7 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { // the assumptions of the remaining algorithm. SmallVector<MachineOperand, 4> Cond; // For AnalyzeBranch. for (MachineFunction::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) { - MachineBasicBlock *BB = FI; + MachineBasicBlock *BB = &*FI; BlockChain *Chain = new (ChainAllocator.Allocate()) BlockChain(BlockToChain, BB); // Also, merge any blocks which we cannot reason about and must preserve @@ -900,8 +1147,8 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { if (!TII->AnalyzeBranch(*BB, TBB, FBB, Cond) || !FI->canFallThrough()) break; - MachineFunction::iterator NextFI(std::next(FI)); - MachineBasicBlock *NextBB = NextFI; + MachineFunction::iterator NextFI = std::next(FI); + MachineBasicBlock *NextBB = &*NextFI; // Ensure that the layout successor is a viable block, as we know that // fallthrough is a possibility. assert(NextFI != FE && "Can't fallthrough past the last block."); @@ -1004,7 +1251,7 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { // Update the terminator of the previous block. if (ChainBB == *FunctionChain.begin()) continue; - MachineBasicBlock *PrevBB = std::prev(MachineFunction::iterator(ChainBB)); + MachineBasicBlock *PrevBB = &*std::prev(MachineFunction::iterator(ChainBB)); // FIXME: It would be awesome of updateTerminator would just return rather // than assert when the branch cannot be analyzed in order to remove this @@ -1035,14 +1282,16 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { } // If PrevBB has a two-way branch, try to re-order the branches - // such that we branch to the successor with higher weight first. + // such that we branch to the successor with higher probability first. if (TBB && !Cond.empty() && FBB && - MBPI->getEdgeWeight(PrevBB, FBB) > MBPI->getEdgeWeight(PrevBB, TBB) && + MBPI->getEdgeProbability(PrevBB, FBB) > + MBPI->getEdgeProbability(PrevBB, TBB) && !TII->ReverseBranchCondition(Cond)) { DEBUG(dbgs() << "Reverse order of the two branches: " << getBlockName(PrevBB) << "\n"); - DEBUG(dbgs() << " Edge weight: " << MBPI->getEdgeWeight(PrevBB, FBB) - << " vs " << MBPI->getEdgeWeight(PrevBB, TBB) << "\n"); + DEBUG(dbgs() << " Edge probability: " + << MBPI->getEdgeProbability(PrevBB, FBB) << " vs " + << MBPI->getEdgeProbability(PrevBB, TBB) << "\n"); DebugLoc dl; // FIXME: this is nowhere TII->RemoveBranch(*PrevBB); TII->InsertBranch(*PrevBB, FBB, TBB, Cond, dl); @@ -1064,13 +1313,14 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { // exclusively on the loop info here so that we can align backedges in // unnatural CFGs and backedges that were introduced purely because of the // loop rotations done during this layout pass. + // FIXME: Use Function::optForSize(). if (F.getFunction()->hasFnAttribute(Attribute::OptimizeForSize)) return; if (FunctionChain.begin() == FunctionChain.end()) return; // Empty chain. const BranchProbability ColdProb(1, 5); // 20% - BlockFrequency EntryFreq = MBFI->getBlockFreq(F.begin()); + BlockFrequency EntryFreq = MBFI->getBlockFreq(&F.front()); BlockFrequency WeightedEntryFreq = EntryFreq * ColdProb; for (MachineBasicBlock *ChainBB : FunctionChain) { if (ChainBB == *FunctionChain.begin()) @@ -1084,6 +1334,11 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { if (!L) continue; + if (AlignAllLoops) { + ChainBB->setAlignment(AlignAllLoops); + continue; + } + unsigned Align = TLI->getPrefLoopAlignment(L); if (!Align) continue; // Don't care about loop alignment. @@ -1224,4 +1479,3 @@ bool MachineBlockPlacementStats::runOnMachineFunction(MachineFunction &F) { return false; } - |