X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FMachineBlockPlacement.cpp;h=84cc9bcdb60db08d95aefeec12a993589b45d61d;hb=424a6917aa3f44c05c886bba41b9b58023bf666d;hp=04bf2a5b3e3e3e91a984c9b0b4e32a6125b599dd;hpb=35742dd20c98497d9e575a87dd69691cbcd4406b;p=oota-llvm.git diff --git a/lib/CodeGen/MachineBlockPlacement.cpp b/lib/CodeGen/MachineBlockPlacement.cpp index 04bf2a5b3e3..84cc9bcdb60 100644 --- a/lib/CodeGen/MachineBlockPlacement.cpp +++ b/lib/CodeGen/MachineBlockPlacement.cpp @@ -41,6 +41,7 @@ #include "llvm/Support/Allocator.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" +#include "llvm/Support/raw_ostream.h" #include "llvm/Target/TargetInstrInfo.h" #include "llvm/Target/TargetLowering.h" #include "llvm/Target/TargetSubtargetInfo.h" @@ -50,7 +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, @@ -74,6 +75,12 @@ static cl::opt OutlineOptionalBranches( "post dominator, out of line."), cl::init(false), cl::Hidden); +static cl::opt OutlineOptionalThreshold( + "outline-optional-threshold", + cl::desc("Don't outline optional branches that are a single block with an " + "instruction count below this threshold"), + cl::init(4), cl::Hidden); + namespace { class BlockChain; /// \brief Type for our function-wide basic block -> block chain mapping. @@ -151,19 +158,18 @@ public: // Update the incoming blocks to point to this chain, and add them to the // chain structure. - for (BlockChain::iterator BI = Chain->begin(), BE = Chain->end(); BI != BE; - ++BI) { - Blocks.push_back(*BI); - assert(BlockToChain[*BI] == Chain && "Incoming blocks not in chain"); - BlockToChain[*BI] = this; + for (MachineBasicBlock *ChainBB : *Chain) { + Blocks.push_back(ChainBB); + assert(BlockToChain[ChainBB] == Chain && "Incoming blocks not in chain"); + BlockToChain[ChainBB] = this; } } #ifndef NDEBUG /// \brief Dump the blocks in this chain. LLVM_DUMP_METHOD void dump() { - for (iterator I = begin(), E = end(); I != E; ++I) - (*I)->dump(); + for (MachineBasicBlock *MBB : *this) + MBB->dump(); } #endif // NDEBUG @@ -311,20 +317,17 @@ void MachineBlockPlacement::markChainSuccessors( const BlockFilterSet *BlockFilter) { // Walk all the blocks in this chain, marking their successors as having // a predecessor placed. - for (BlockChain::iterator CBI = Chain.begin(), CBE = Chain.end(); CBI != CBE; - ++CBI) { + for (MachineBasicBlock *MBB : Chain) { // Add any successors for which this is the only un-placed in-loop // predecessor to the worklist as a viable candidate for CFG-neutral // placement. No subsequent placement of this block will violate the CFG // shape, so we get to use heuristics to choose a favorable placement. - for (MachineBasicBlock::succ_iterator SI = (*CBI)->succ_begin(), - SE = (*CBI)->succ_end(); - SI != SE; ++SI) { - if (BlockFilter && !BlockFilter->count(*SI)) + for (MachineBasicBlock *Succ : MBB->successors()) { + if (BlockFilter && !BlockFilter->count(Succ)) continue; - BlockChain &SuccChain = *BlockToChain[*SI]; + BlockChain &SuccChain = *BlockToChain[Succ]; // Disregard edges within a fixed chain, or edges to the loop header. - if (&Chain == &SuccChain || *SI == LoopHeaderBB) + if (&Chain == &SuccChain || Succ == LoopHeaderBB) continue; // This is a cross-chain edge that is within the loop, so decrement the @@ -381,8 +384,25 @@ MachineBlockPlacement::selectBestSuccessor(MachineBasicBlock *BB, // dominates all terminators of the MachineFunction. If it does, other // successors must be optional. Don't do this for cold branches. if (OutlineOptionalBranches && SuccProb > HotProb.getCompl() && - UnavoidableBlocks.count(Succ) > 0) - return Succ; + UnavoidableBlocks.count(Succ) > 0) { + auto HasShortOptionalBranch = [&]() { + for (MachineBasicBlock *Pred : Succ->predecessors()) { + // Check whether there is an unplaced optional branch. + if (Pred == Succ || (BlockFilter && !BlockFilter->count(Pred)) || + BlockToChain[Pred] == &Chain) + continue; + // Check whether the optional branch has exactly one BB. + if (Pred->pred_size() > 1 || *Pred->pred_begin() != BB) + continue; + // Check whether the optional branch is small. + if (Pred->size() < OutlineOptionalThreshold) + return true; + } + return false; + }; + if (!HasShortOptionalBranch()) + return Succ; + } // Only consider successors which are either "hot", or wouldn't violate // any CFG constraints. @@ -453,22 +473,20 @@ MachineBasicBlock *MachineBlockPlacement::selectBestCandidateBlock( MachineBasicBlock *BestBlock = nullptr; BlockFrequency BestFreq; - for (SmallVectorImpl::iterator WBI = WorkList.begin(), - WBE = WorkList.end(); - WBI != WBE; ++WBI) { - BlockChain &SuccChain = *BlockToChain[*WBI]; + for (MachineBasicBlock *MBB : WorkList) { + BlockChain &SuccChain = *BlockToChain[MBB]; if (&SuccChain == &Chain) { - DEBUG(dbgs() << " " << getBlockName(*WBI) << " -> Already merged!\n"); + DEBUG(dbgs() << " " << getBlockName(MBB) << " -> Already merged!\n"); continue; } assert(SuccChain.LoopPredecessors == 0 && "Found CFG-violating block"); - BlockFrequency CandidateFreq = MBFI->getBlockFreq(*WBI); - DEBUG(dbgs() << " " << getBlockName(*WBI) << " -> "; + BlockFrequency CandidateFreq = MBFI->getBlockFreq(MBB); + DEBUG(dbgs() << " " << getBlockName(MBB) << " -> "; MBFI->printBlockFreq(dbgs(), CandidateFreq) << " (freq)\n"); if (BestBlock && BestFreq >= CandidateFreq) continue; - BestBlock = *WBI; + BestBlock = MBB; BestFreq = CandidateFreq; } return BestBlock; @@ -487,14 +505,14 @@ 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; @@ -578,10 +596,7 @@ MachineBlockPlacement::findBestLoopTop(MachineLoop &L, BlockFrequency BestPredFreq; MachineBasicBlock *BestPred = nullptr; - for (MachineBasicBlock::pred_iterator PI = L.getHeader()->pred_begin(), - PE = L.getHeader()->pred_end(); - PI != PE; ++PI) { - MachineBasicBlock *Pred = *PI; + for (MachineBasicBlock *Pred : L.getHeader()->predecessors()) { if (!LoopBlockSet.count(Pred)) continue; DEBUG(dbgs() << " header pred: " << getBlockName(Pred) << ", " @@ -643,12 +658,11 @@ MachineBlockPlacement::findBestLoopExit(MachineFunction &F, MachineLoop &L, DEBUG(dbgs() << "Finding best loop exit for: " << getBlockName(L.getHeader()) << "\n"); - for (MachineLoop::block_iterator I = L.block_begin(), E = L.block_end(); - I != E; ++I) { - BlockChain &Chain = *BlockToChain[*I]; + for (MachineBasicBlock *MBB : L.getBlocks()) { + BlockChain &Chain = *BlockToChain[MBB]; // Ensure that this block is at the end of a chain; otherwise it could be - // mid-way through an inner loop or a successor of an analyzable branch. - if (*I != *std::prev(Chain.end())) + // mid-way through an inner loop or a successor of an unanalyzable branch. + if (MBB != *std::prev(Chain.end())) continue; // Now walk the successors. We need to establish whether this has a viable @@ -662,58 +676,56 @@ MachineBlockPlacement::findBestLoopExit(MachineFunction &F, MachineLoop &L, // 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(*I, WeightScale); - for (MachineBasicBlock::succ_iterator SI = (*I)->succ_begin(), - SE = (*I)->succ_end(); - SI != SE; ++SI) { - if ((*SI)->isLandingPad()) + uint32_t SumWeight = MBPI->getSumForBlock(MBB, WeightScale); + for (MachineBasicBlock *Succ : MBB->successors()) { + if (Succ->isEHPad()) continue; - if (*SI == *I) + if (Succ == MBB) continue; - BlockChain &SuccChain = *BlockToChain[*SI]; + BlockChain &SuccChain = *BlockToChain[Succ]; // Don't split chains, either this chain or the successor's chain. if (&Chain == &SuccChain) { - DEBUG(dbgs() << " exiting: " << getBlockName(*I) << " -> " - << getBlockName(*SI) << " (chain conflict)\n"); + DEBUG(dbgs() << " exiting: " << getBlockName(MBB) << " -> " + << getBlockName(Succ) << " (chain conflict)\n"); continue; } - uint32_t SuccWeight = MBPI->getEdgeWeight(*I, *SI); - if (LoopBlockSet.count(*SI)) { - DEBUG(dbgs() << " looping: " << getBlockName(*I) << " -> " - << getBlockName(*SI) << " (" << SuccWeight << ")\n"); + uint32_t SuccWeight = MBPI->getEdgeWeight(MBB, Succ); + if (LoopBlockSet.count(Succ)) { + DEBUG(dbgs() << " looping: " << getBlockName(MBB) << " -> " + << getBlockName(Succ) << " (" << SuccWeight << ")\n"); HasLoopingSucc = true; continue; } unsigned SuccLoopDepth = 0; - if (MachineLoop *ExitLoop = MLI->getLoopFor(*SI)) { + if (MachineLoop *ExitLoop = MLI->getLoopFor(Succ)) { SuccLoopDepth = ExitLoop->getLoopDepth(); if (ExitLoop->contains(&L)) - BlocksExitingToOuterLoop.insert(*I); + BlocksExitingToOuterLoop.insert(MBB); } BranchProbability SuccProb(SuccWeight / WeightScale, SumWeight); - BlockFrequency ExitEdgeFreq = MBFI->getBlockFreq(*I) * SuccProb; - DEBUG(dbgs() << " exiting: " << getBlockName(*I) << " -> " - << getBlockName(*SI) << " [L:" << SuccLoopDepth << "] ("; + BlockFrequency ExitEdgeFreq = MBFI->getBlockFreq(MBB) * SuccProb; + DEBUG(dbgs() << " exiting: " << getBlockName(MBB) << " -> " + << getBlockName(Succ) << " [L:" << SuccLoopDepth << "] ("; MBFI->printBlockFreq(dbgs(), ExitEdgeFreq) << ")\n"); // Note that we bias this toward an existing layout successor to retain // incoming order in the absence of better information. The exit must have // a frequency higher than the current exit before we consider breaking // the layout. BranchProbability Bias(100 - ExitBlockBias, 100); - if (!ExitingBB || BestExitLoopDepth < SuccLoopDepth || + if (!ExitingBB || SuccLoopDepth > BestExitLoopDepth || ExitEdgeFreq > BestExitEdgeFreq || - ((*I)->isLayoutSuccessor(*SI) && + (MBB->isLayoutSuccessor(Succ) && !(ExitEdgeFreq < BestExitEdgeFreq * Bias))) { BestExitEdgeFreq = ExitEdgeFreq; - ExitingBB = *I; + ExitingBB = MBB; } } - // Restore the old exiting state, no viable looping successor was found. if (!HasLoopingSucc) { + // Restore the old exiting state, no viable looping successor was found. ExitingBB = OldExitingBB; BestExitEdgeFreq = OldBestExitEdgeFreq; continue; @@ -749,12 +761,10 @@ void MachineBlockPlacement::rotateLoop(BlockChain &LoopChain, MachineBasicBlock *Top = *LoopChain.begin(); bool ViableTopFallthrough = false; - for (MachineBasicBlock::pred_iterator PI = Top->pred_begin(), - PE = Top->pred_end(); - PI != PE; ++PI) { - BlockChain *PredChain = BlockToChain[*PI]; - if (!LoopBlockSet.count(*PI) && - (!PredChain || *PI == *std::prev(PredChain->end()))) { + for (MachineBasicBlock *Pred : Top->predecessors()) { + BlockChain *PredChain = BlockToChain[Pred]; + if (!LoopBlockSet.count(Pred) && + (!PredChain || Pred == *std::prev(PredChain->end()))) { ViableTopFallthrough = true; break; } @@ -765,12 +775,10 @@ void MachineBlockPlacement::rotateLoop(BlockChain &LoopChain, // introduce an unnecessary branch. if (ViableTopFallthrough) { MachineBasicBlock *Bottom = *std::prev(LoopChain.end()); - for (MachineBasicBlock::succ_iterator SI = Bottom->succ_begin(), - SE = Bottom->succ_end(); - SI != SE; ++SI) { - BlockChain *SuccChain = BlockToChain[*SI]; - if (!LoopBlockSet.count(*SI) && - (!SuccChain || *SI == *SuccChain->begin())) + for (MachineBasicBlock *Succ : Bottom->successors()) { + BlockChain *SuccChain = BlockToChain[Succ]; + if (!LoopBlockSet.count(Succ) && + (!SuccChain || Succ == *SuccChain->begin())) return; } } @@ -793,8 +801,8 @@ void MachineBlockPlacement::buildLoopChains(MachineFunction &F, MachineLoop &L) { // First recurse through any nested loops, building chains for those inner // loops. - for (MachineLoop::iterator LI = L.begin(), LE = L.end(); LI != LE; ++LI) - buildLoopChains(F, **LI); + for (MachineLoop *InnerLoop : L) + buildLoopChains(F, *InnerLoop); SmallVector BlockWorkList; BlockFilterSet LoopBlockSet(L.block_begin(), L.block_end()); @@ -820,20 +828,16 @@ void MachineBlockPlacement::buildLoopChains(MachineFunction &F, SmallPtrSet UpdatedPreds; assert(LoopChain.LoopPredecessors == 0); UpdatedPreds.insert(&LoopChain); - for (MachineLoop::block_iterator BI = L.block_begin(), BE = L.block_end(); - BI != BE; ++BI) { - BlockChain &Chain = *BlockToChain[*BI]; + for (MachineBasicBlock *LoopBB : L.getBlocks()) { + BlockChain &Chain = *BlockToChain[LoopBB]; if (!UpdatedPreds.insert(&Chain).second) continue; assert(Chain.LoopPredecessors == 0); - for (BlockChain::iterator BCI = Chain.begin(), BCE = Chain.end(); - BCI != BCE; ++BCI) { - assert(BlockToChain[*BCI] == &Chain); - for (MachineBasicBlock::pred_iterator PI = (*BCI)->pred_begin(), - PE = (*BCI)->pred_end(); - PI != PE; ++PI) { - if (BlockToChain[*PI] == &Chain || !LoopBlockSet.count(*PI)) + for (MachineBasicBlock *ChainBB : Chain) { + assert(BlockToChain[ChainBB] == &Chain); + for (MachineBasicBlock *Pred : ChainBB->predecessors()) { + if (BlockToChain[Pred] == &Chain || !LoopBlockSet.count(Pred)) continue; ++Chain.LoopPredecessors; } @@ -855,29 +859,26 @@ void MachineBlockPlacement::buildLoopChains(MachineFunction &F, << " Loop header: " << getBlockName(*L.block_begin()) << "\n" << " Chain header: " << getBlockName(*LoopChain.begin()) << "\n"; } - for (BlockChain::iterator BCI = LoopChain.begin(), BCE = LoopChain.end(); - BCI != BCE; ++BCI) { - dbgs() << " ... " << getBlockName(*BCI) << "\n"; - if (!LoopBlockSet.erase(*BCI)) { + for (MachineBasicBlock *ChainBB : LoopChain) { + dbgs() << " ... " << getBlockName(ChainBB) << "\n"; + if (!LoopBlockSet.erase(ChainBB)) { // We don't mark the loop as bad here because there are real situations // where this can occur. For example, with an unanalyzable fallthrough // from a loop block to a non-loop block or vice versa. dbgs() << "Loop chain contains a block not contained by the loop!\n" << " Loop header: " << getBlockName(*L.block_begin()) << "\n" << " Chain header: " << getBlockName(*LoopChain.begin()) << "\n" - << " Bad block: " << getBlockName(*BCI) << "\n"; + << " Bad block: " << getBlockName(ChainBB) << "\n"; } } if (!LoopBlockSet.empty()) { BadLoop = true; - for (BlockFilterSet::iterator LBI = LoopBlockSet.begin(), - LBE = LoopBlockSet.end(); - LBI != LBE; ++LBI) + for (MachineBasicBlock *LoopBB : LoopBlockSet) dbgs() << "Loop contains blocks never placed into a chain!\n" << " Loop header: " << getBlockName(*L.block_begin()) << "\n" << " Chain header: " << getBlockName(*LoopChain.begin()) << "\n" - << " Bad block: " << getBlockName(*LBI) << "\n"; + << " Bad block: " << getBlockName(LoopBB) << "\n"; } assert(!BadLoop && "Detected problems with the placement of this loop."); }); @@ -888,7 +889,7 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { // the assumptions of the remaining algorithm. SmallVector 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 @@ -899,8 +900,8 @@ 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."); @@ -935,27 +936,22 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { } // Build any loop-based chains. - for (MachineLoopInfo::iterator LI = MLI->begin(), LE = MLI->end(); LI != LE; - ++LI) - buildLoopChains(F, **LI); + for (MachineLoop *L : *MLI) + buildLoopChains(F, *L); SmallVector BlockWorkList; SmallPtrSet UpdatedPreds; - for (MachineFunction::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) { - MachineBasicBlock *BB = &*FI; - BlockChain &Chain = *BlockToChain[BB]; + for (MachineBasicBlock &MBB : F) { + BlockChain &Chain = *BlockToChain[&MBB]; if (!UpdatedPreds.insert(&Chain).second) continue; assert(Chain.LoopPredecessors == 0); - for (BlockChain::iterator BCI = Chain.begin(), BCE = Chain.end(); - BCI != BCE; ++BCI) { - assert(BlockToChain[*BCI] == &Chain); - for (MachineBasicBlock::pred_iterator PI = (*BCI)->pred_begin(), - PE = (*BCI)->pred_end(); - PI != PE; ++PI) { - if (BlockToChain[*PI] == &Chain) + for (MachineBasicBlock *ChainBB : Chain) { + assert(BlockToChain[ChainBB] == &Chain); + for (MachineBasicBlock *Pred : ChainBB->predecessors()) { + if (BlockToChain[Pred] == &Chain) continue; ++Chain.LoopPredecessors; } @@ -975,46 +971,40 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { // Crash at the end so we get all of the debugging output first. bool BadFunc = false; FunctionBlockSetType FunctionBlockSet; - for (MachineFunction::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) - FunctionBlockSet.insert(FI); + for (MachineBasicBlock &MBB : F) + FunctionBlockSet.insert(&MBB); - for (BlockChain::iterator BCI = FunctionChain.begin(), - BCE = FunctionChain.end(); - BCI != BCE; ++BCI) - if (!FunctionBlockSet.erase(*BCI)) { + for (MachineBasicBlock *ChainBB : FunctionChain) + if (!FunctionBlockSet.erase(ChainBB)) { BadFunc = true; dbgs() << "Function chain contains a block not in the function!\n" - << " Bad block: " << getBlockName(*BCI) << "\n"; + << " Bad block: " << getBlockName(ChainBB) << "\n"; } if (!FunctionBlockSet.empty()) { BadFunc = true; - for (FunctionBlockSetType::iterator FBI = FunctionBlockSet.begin(), - FBE = FunctionBlockSet.end(); - FBI != FBE; ++FBI) + for (MachineBasicBlock *RemainingBB : FunctionBlockSet) dbgs() << "Function contains blocks never placed into a chain!\n" - << " Bad block: " << getBlockName(*FBI) << "\n"; + << " Bad block: " << getBlockName(RemainingBB) << "\n"; } assert(!BadFunc && "Detected problems with the block placement."); }); // Splice the blocks into place. MachineFunction::iterator InsertPos = F.begin(); - for (BlockChain::iterator BI = FunctionChain.begin(), - BE = FunctionChain.end(); - BI != BE; ++BI) { - DEBUG(dbgs() << (BI == FunctionChain.begin() ? "Placing chain " - : " ... ") - << getBlockName(*BI) << "\n"); - if (InsertPos != MachineFunction::iterator(*BI)) - F.splice(InsertPos, *BI); + for (MachineBasicBlock *ChainBB : FunctionChain) { + DEBUG(dbgs() << (ChainBB == *FunctionChain.begin() ? "Placing chain " + : " ... ") + << getBlockName(ChainBB) << "\n"); + if (InsertPos != MachineFunction::iterator(ChainBB)) + F.splice(InsertPos, ChainBB); else ++InsertPos; // Update the terminator of the previous block. - if (BI == FunctionChain.begin()) + if (ChainBB == *FunctionChain.begin()) continue; - MachineBasicBlock *PrevBB = std::prev(MachineFunction::iterator(*BI)); + 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 @@ -1033,7 +1023,7 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { // is mistakenly pointing to "*BI". // bool needUpdateBr = true; - if (!Cond.empty() && (!FBB || FBB == *BI)) { + if (!Cond.empty() && (!FBB || FBB == ChainBB)) { PrevBB->updateTerminator(); needUpdateBr = false; Cond.clear(); @@ -1074,22 +1064,24 @@ 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 (BlockChain::iterator BI = std::next(FunctionChain.begin()), - BE = FunctionChain.end(); - BI != BE; ++BI) { + for (MachineBasicBlock *ChainBB : FunctionChain) { + if (ChainBB == *FunctionChain.begin()) + continue; + // Don't align non-looping basic blocks. These are unlikely to execute // enough times to matter in practice. Note that we'll still handle // unnatural CFGs inside of a natural outer loop (the common case) and // rotated loops. - MachineLoop *L = MLI->getLoopFor(*BI); + MachineLoop *L = MLI->getLoopFor(ChainBB); if (!L) continue; @@ -1099,7 +1091,7 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { // If the block is cold relative to the function entry don't waste space // aligning it. - BlockFrequency Freq = MBFI->getBlockFreq(*BI); + BlockFrequency Freq = MBFI->getBlockFreq(ChainBB); if (Freq < WeightedEntryFreq) continue; @@ -1112,12 +1104,13 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { // Check for the existence of a non-layout predecessor which would benefit // from aligning this block. - MachineBasicBlock *LayoutPred = *std::prev(BI); + MachineBasicBlock *LayoutPred = + &*std::prev(MachineFunction::iterator(ChainBB)); // Force alignment if all the predecessors are jumps. We already checked // that the block isn't cold above. - if (!LayoutPred->isSuccessor(*BI)) { - (*BI)->setAlignment(Align); + if (!LayoutPred->isSuccessor(ChainBB)) { + ChainBB->setAlignment(Align); continue; } @@ -1125,10 +1118,11 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { // cold relative to the block. When this is true, other predecessors make up // all of the hot entries into the block and thus alignment is likely to be // important. - BranchProbability LayoutProb = MBPI->getEdgeProbability(LayoutPred, *BI); + BranchProbability LayoutProb = + MBPI->getEdgeProbability(LayoutPred, ChainBB); BlockFrequency LayoutEdgeFreq = MBFI->getBlockFreq(LayoutPred) * LayoutProb; if (LayoutEdgeFreq <= (Freq * ColdProb)) - (*BI)->setAlignment(Align); + ChainBB->setAlignment(Align); } } @@ -1155,8 +1149,8 @@ bool MachineBlockPlacement::runOnMachineFunction(MachineFunction &F) { if (AlignAllBlock) // Align all of the blocks in the function to a specific alignment. - for (MachineFunction::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) - FI->setAlignment(AlignAllBlock); + for (MachineBasicBlock &MBB : F) + MBB.setAlignment(AlignAllBlock); // We always return true as we have no way to track whether the final order // differs from the original order. @@ -1211,20 +1205,19 @@ bool MachineBlockPlacementStats::runOnMachineFunction(MachineFunction &F) { MBPI = &getAnalysis(); MBFI = &getAnalysis(); - for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I) { - BlockFrequency BlockFreq = MBFI->getBlockFreq(I); + for (MachineBasicBlock &MBB : F) { + BlockFrequency BlockFreq = MBFI->getBlockFreq(&MBB); Statistic &NumBranches = - (I->succ_size() > 1) ? NumCondBranches : NumUncondBranches; + (MBB.succ_size() > 1) ? NumCondBranches : NumUncondBranches; Statistic &BranchTakenFreq = - (I->succ_size() > 1) ? CondBranchTakenFreq : UncondBranchTakenFreq; - for (MachineBasicBlock::succ_iterator SI = I->succ_begin(), - SE = I->succ_end(); - SI != SE; ++SI) { + (MBB.succ_size() > 1) ? CondBranchTakenFreq : UncondBranchTakenFreq; + for (MachineBasicBlock *Succ : MBB.successors()) { // Skip if this successor is a fallthrough. - if (I->isLayoutSuccessor(*SI)) + if (MBB.isLayoutSuccessor(Succ)) continue; - BlockFrequency EdgeFreq = BlockFreq * MBPI->getEdgeProbability(I, *SI); + BlockFrequency EdgeFreq = + BlockFreq * MBPI->getEdgeProbability(&MBB, Succ); ++NumBranches; BranchTakenFreq += EdgeFreq.getFrequency(); } @@ -1232,4 +1225,3 @@ bool MachineBlockPlacementStats::runOnMachineFunction(MachineFunction &F) { return false; } -