//===-- LoopUnswitch.cpp - Hoist loop-invariant conditionals in loop ------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This pass transforms loops that contain branches on loop-invariant conditions // to have multiple loops. For example, it turns the left into the right code: // // for (...) if (lic) // A for (...) // if (lic) A; B; C // B else // C for (...) // A; C // // This can increase the size of the code exponentially (doubling it every time // a loop is unswitched) so we only unswitch if the resultant code will be // smaller than a threshold. // // This pass expects LICM to be run before it to hoist invariant conditions out // of the loop, to make the unswitching opportunity obvious. // //===----------------------------------------------------------------------===// #include "llvm/Transforms/Scalar.h" #include "llvm/ADT/STLExtras.h" #include "llvm/ADT/SmallPtrSet.h" #include "llvm/ADT/Statistic.h" #include "llvm/Analysis/GlobalsModRef.h" #include "llvm/Analysis/AssumptionCache.h" #include "llvm/Analysis/CodeMetrics.h" #include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Analysis/LoopInfo.h" #include "llvm/Analysis/LoopPass.h" #include "llvm/Analysis/ScalarEvolution.h" #include "llvm/Analysis/TargetTransformInfo.h" #include "llvm/Analysis/BlockFrequencyInfoImpl.h" #include "llvm/Analysis/BlockFrequencyInfo.h" #include "llvm/Analysis/BranchProbabilityInfo.h" #include "llvm/Support/BranchProbability.h" #include "llvm/IR/Constants.h" #include "llvm/IR/DerivedTypes.h" #include "llvm/IR/Dominators.h" #include "llvm/IR/Function.h" #include "llvm/IR/Instructions.h" #include "llvm/IR/Module.h" #include "llvm/IR/MDBuilder.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/Support/raw_ostream.h" #include "llvm/Transforms/Utils/BasicBlockUtils.h" #include "llvm/Transforms/Utils/Cloning.h" #include "llvm/Transforms/Utils/Local.h" #include <algorithm> #include <map> #include <set> using namespace llvm; #define DEBUG_TYPE "loop-unswitch" STATISTIC(NumBranches, "Number of branches unswitched"); STATISTIC(NumSwitches, "Number of switches unswitched"); STATISTIC(NumSelects , "Number of selects unswitched"); STATISTIC(NumTrivial , "Number of unswitches that are trivial"); STATISTIC(NumSimplify, "Number of simplifications of unswitched code"); STATISTIC(TotalInsts, "Total number of instructions analyzed"); // The specific value of 100 here was chosen based only on intuition and a // few specific examples. static cl::opt<unsigned> Threshold("loop-unswitch-threshold", cl::desc("Max loop size to unswitch"), cl::init(100), cl::Hidden); static cl::opt<bool> LoopUnswitchWithBlockFrequency("loop-unswitch-with-block-frequency", cl::init(false), cl::Hidden, cl::desc("Enable the use of the block frequency analysis to access PGO " "heuristics to minimize code growth in cold regions.")); static cl::opt<unsigned> ColdnessThreshold("loop-unswitch-coldness-threshold", cl::init(1), cl::Hidden, cl::desc("Coldness threshold in percentage. The loop header frequency " "(relative to the entry frequency) is compared with this " "threshold to determine if non-trivial unswitching should be " "enabled.")); namespace { class LUAnalysisCache { typedef DenseMap<const SwitchInst*, SmallPtrSet<const Value *, 8> > UnswitchedValsMap; typedef UnswitchedValsMap::iterator UnswitchedValsIt; struct LoopProperties { unsigned CanBeUnswitchedCount; unsigned WasUnswitchedCount; unsigned SizeEstimation; UnswitchedValsMap UnswitchedVals; }; // Here we use std::map instead of DenseMap, since we need to keep valid // LoopProperties pointer for current loop for better performance. typedef std::map<const Loop*, LoopProperties> LoopPropsMap; typedef LoopPropsMap::iterator LoopPropsMapIt; LoopPropsMap LoopsProperties; UnswitchedValsMap *CurLoopInstructions; LoopProperties *CurrentLoopProperties; // A loop unswitching with an estimated cost above this threshold // is not performed. MaxSize is turned into unswitching quota for // the current loop, and reduced correspondingly, though note that // the quota is returned by releaseMemory() when the loop has been // processed, so that MaxSize will return to its previous // value. So in most cases MaxSize will equal the Threshold flag // when a new loop is processed. An exception to that is that // MaxSize will have a smaller value while processing nested loops // that were introduced due to loop unswitching of an outer loop. // // FIXME: The way that MaxSize works is subtle and depends on the // pass manager processing loops and calling releaseMemory() in a // specific order. It would be good to find a more straightforward // way of doing what MaxSize does. unsigned MaxSize; public: LUAnalysisCache() : CurLoopInstructions(nullptr), CurrentLoopProperties(nullptr), MaxSize(Threshold) {} // Analyze loop. Check its size, calculate is it possible to unswitch // it. Returns true if we can unswitch this loop. bool countLoop(const Loop *L, const TargetTransformInfo &TTI, AssumptionCache *AC); // Clean all data related to given loop. void forgetLoop(const Loop *L); // Mark case value as unswitched. // Since SI instruction can be partly unswitched, in order to avoid // extra unswitching in cloned loops keep track all unswitched values. void setUnswitched(const SwitchInst *SI, const Value *V); // Check was this case value unswitched before or not. bool isUnswitched(const SwitchInst *SI, const Value *V); // Returns true if another unswitching could be done within the cost // threshold. bool CostAllowsUnswitching(); // Clone all loop-unswitch related loop properties. // Redistribute unswitching quotas. // Note, that new loop data is stored inside the VMap. void cloneData(const Loop *NewLoop, const Loop *OldLoop, const ValueToValueMapTy &VMap); }; class LoopUnswitch : public LoopPass { LoopInfo *LI; // Loop information LPPassManager *LPM; AssumptionCache *AC; // Used to check if second loop needs processing after // RewriteLoopBodyWithConditionConstant rewrites first loop. std::vector<Loop*> LoopProcessWorklist; LUAnalysisCache BranchesInfo; bool EnabledPGO; // BFI and ColdEntryFreq are only used when PGO and // LoopUnswitchWithBlockFrequency are enabled. BlockFrequencyInfo BFI; BlockFrequency ColdEntryFreq; bool OptimizeForSize; bool redoLoop; Loop *currentLoop; DominatorTree *DT; BasicBlock *loopHeader; BasicBlock *loopPreheader; // LoopBlocks contains all of the basic blocks of the loop, including the // preheader of the loop, the body of the loop, and the exit blocks of the // loop, in that order. std::vector<BasicBlock*> LoopBlocks; // NewBlocks contained cloned copy of basic blocks from LoopBlocks. std::vector<BasicBlock*> NewBlocks; public: static char ID; // Pass ID, replacement for typeid explicit LoopUnswitch(bool Os = false) : LoopPass(ID), OptimizeForSize(Os), redoLoop(false), currentLoop(nullptr), DT(nullptr), loopHeader(nullptr), loopPreheader(nullptr) { initializeLoopUnswitchPass(*PassRegistry::getPassRegistry()); } bool runOnLoop(Loop *L, LPPassManager &LPM) override; bool processCurrentLoop(); /// This transformation requires natural loop information & requires that /// loop preheaders be inserted into the CFG. /// void getAnalysisUsage(AnalysisUsage &AU) const override { AU.addRequired<AssumptionCacheTracker>(); AU.addRequiredID(LoopSimplifyID); AU.addPreservedID(LoopSimplifyID); AU.addRequired<LoopInfoWrapperPass>(); AU.addPreserved<LoopInfoWrapperPass>(); AU.addRequiredID(LCSSAID); AU.addPreservedID(LCSSAID); AU.addRequired<DominatorTreeWrapperPass>(); AU.addPreserved<DominatorTreeWrapperPass>(); AU.addPreserved<ScalarEvolutionWrapperPass>(); AU.addRequired<TargetTransformInfoWrapperPass>(); AU.addPreserved<GlobalsAAWrapperPass>(); } private: void releaseMemory() override { BranchesInfo.forgetLoop(currentLoop); } void initLoopData() { loopHeader = currentLoop->getHeader(); loopPreheader = currentLoop->getLoopPreheader(); } /// Split all of the edges from inside the loop to their exit blocks. /// Update the appropriate Phi nodes as we do so. void SplitExitEdges(Loop *L, const SmallVectorImpl<BasicBlock *> &ExitBlocks); bool TryTrivialLoopUnswitch(bool &Changed); bool UnswitchIfProfitable(Value *LoopCond, Constant *Val, TerminatorInst *TI = nullptr); void UnswitchTrivialCondition(Loop *L, Value *Cond, Constant *Val, BasicBlock *ExitBlock, TerminatorInst *TI); void UnswitchNontrivialCondition(Value *LIC, Constant *OnVal, Loop *L, TerminatorInst *TI); void RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC, Constant *Val, bool isEqual); void EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val, BasicBlock *TrueDest, BasicBlock *FalseDest, Instruction *InsertPt, TerminatorInst *TI); void SimplifyCode(std::vector<Instruction*> &Worklist, Loop *L); }; } // Analyze loop. Check its size, calculate is it possible to unswitch // it. Returns true if we can unswitch this loop. bool LUAnalysisCache::countLoop(const Loop *L, const TargetTransformInfo &TTI, AssumptionCache *AC) { LoopPropsMapIt PropsIt; bool Inserted; std::tie(PropsIt, Inserted) = LoopsProperties.insert(std::make_pair(L, LoopProperties())); LoopProperties &Props = PropsIt->second; if (Inserted) { // New loop. // Limit the number of instructions to avoid causing significant code // expansion, and the number of basic blocks, to avoid loops with // large numbers of branches which cause loop unswitching to go crazy. // This is a very ad-hoc heuristic. SmallPtrSet<const Value *, 32> EphValues; CodeMetrics::collectEphemeralValues(L, AC, EphValues); // FIXME: This is overly conservative because it does not take into // consideration code simplification opportunities and code that can // be shared by the resultant unswitched loops. CodeMetrics Metrics; for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); I != E; ++I) Metrics.analyzeBasicBlock(*I, TTI, EphValues); Props.SizeEstimation = Metrics.NumInsts; Props.CanBeUnswitchedCount = MaxSize / (Props.SizeEstimation); Props.WasUnswitchedCount = 0; MaxSize -= Props.SizeEstimation * Props.CanBeUnswitchedCount; if (Metrics.notDuplicatable) { DEBUG(dbgs() << "NOT unswitching loop %" << L->getHeader()->getName() << ", contents cannot be " << "duplicated!\n"); return false; } } // Be careful. This links are good only before new loop addition. CurrentLoopProperties = &Props; CurLoopInstructions = &Props.UnswitchedVals; return true; } // Clean all data related to given loop. void LUAnalysisCache::forgetLoop(const Loop *L) { LoopPropsMapIt LIt = LoopsProperties.find(L); if (LIt != LoopsProperties.end()) { LoopProperties &Props = LIt->second; MaxSize += (Props.CanBeUnswitchedCount + Props.WasUnswitchedCount) * Props.SizeEstimation; LoopsProperties.erase(LIt); } CurrentLoopProperties = nullptr; CurLoopInstructions = nullptr; } // Mark case value as unswitched. // Since SI instruction can be partly unswitched, in order to avoid // extra unswitching in cloned loops keep track all unswitched values. void LUAnalysisCache::setUnswitched(const SwitchInst *SI, const Value *V) { (*CurLoopInstructions)[SI].insert(V); } // Check was this case value unswitched before or not. bool LUAnalysisCache::isUnswitched(const SwitchInst *SI, const Value *V) { return (*CurLoopInstructions)[SI].count(V); } bool LUAnalysisCache::CostAllowsUnswitching() { return CurrentLoopProperties->CanBeUnswitchedCount > 0; } // Clone all loop-unswitch related loop properties. // Redistribute unswitching quotas. // Note, that new loop data is stored inside the VMap. void LUAnalysisCache::cloneData(const Loop *NewLoop, const Loop *OldLoop, const ValueToValueMapTy &VMap) { LoopProperties &NewLoopProps = LoopsProperties[NewLoop]; LoopProperties &OldLoopProps = *CurrentLoopProperties; UnswitchedValsMap &Insts = OldLoopProps.UnswitchedVals; // Reallocate "can-be-unswitched quota" --OldLoopProps.CanBeUnswitchedCount; ++OldLoopProps.WasUnswitchedCount; NewLoopProps.WasUnswitchedCount = 0; unsigned Quota = OldLoopProps.CanBeUnswitchedCount; NewLoopProps.CanBeUnswitchedCount = Quota / 2; OldLoopProps.CanBeUnswitchedCount = Quota - Quota / 2; NewLoopProps.SizeEstimation = OldLoopProps.SizeEstimation; // Clone unswitched values info: // for new loop switches we clone info about values that was // already unswitched and has redundant successors. for (UnswitchedValsIt I = Insts.begin(); I != Insts.end(); ++I) { const SwitchInst *OldInst = I->first; Value *NewI = VMap.lookup(OldInst); const SwitchInst *NewInst = cast_or_null<SwitchInst>(NewI); assert(NewInst && "All instructions that are in SrcBB must be in VMap."); NewLoopProps.UnswitchedVals[NewInst] = OldLoopProps.UnswitchedVals[OldInst]; } } char LoopUnswitch::ID = 0; INITIALIZE_PASS_BEGIN(LoopUnswitch, "loop-unswitch", "Unswitch loops", false, false) INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) INITIALIZE_PASS_DEPENDENCY(LoopSimplify) INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) INITIALIZE_PASS_DEPENDENCY(LCSSA) INITIALIZE_PASS_END(LoopUnswitch, "loop-unswitch", "Unswitch loops", false, false) Pass *llvm::createLoopUnswitchPass(bool Os) { return new LoopUnswitch(Os); } /// Cond is a condition that occurs in L. If it is invariant in the loop, or has /// an invariant piece, return the invariant. Otherwise, return null. static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed) { // We started analyze new instruction, increment scanned instructions counter. ++TotalInsts; // We can never unswitch on vector conditions. if (Cond->getType()->isVectorTy()) return nullptr; // Constants should be folded, not unswitched on! if (isa<Constant>(Cond)) return nullptr; // TODO: Handle: br (VARIANT|INVARIANT). // Hoist simple values out. if (L->makeLoopInvariant(Cond, Changed)) return Cond; if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Cond)) if (BO->getOpcode() == Instruction::And || BO->getOpcode() == Instruction::Or) { // If either the left or right side is invariant, we can unswitch on this, // which will cause the branch to go away in one loop and the condition to // simplify in the other one. if (Value *LHS = FindLIVLoopCondition(BO->getOperand(0), L, Changed)) return LHS; if (Value *RHS = FindLIVLoopCondition(BO->getOperand(1), L, Changed)) return RHS; } return nullptr; } bool LoopUnswitch::runOnLoop(Loop *L, LPPassManager &LPM_Ref) { if (skipOptnoneFunction(L)) return false; AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache( *L->getHeader()->getParent()); LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); LPM = &LPM_Ref; DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree(); currentLoop = L; Function *F = currentLoop->getHeader()->getParent(); EnabledPGO = F->getEntryCount().hasValue(); if (LoopUnswitchWithBlockFrequency && EnabledPGO) { BranchProbabilityInfo BPI(*F, *LI); BFI.calculate(*L->getHeader()->getParent(), BPI, *LI); // Use BranchProbability to compute a minimum frequency based on // function entry baseline frequency. Loops with headers below this // frequency are considered as cold. const BranchProbability ColdProb(ColdnessThreshold, 100); ColdEntryFreq = BlockFrequency(BFI.getEntryFreq()) * ColdProb; } bool Changed = false; do { assert(currentLoop->isLCSSAForm(*DT)); redoLoop = false; Changed |= processCurrentLoop(); } while(redoLoop); // FIXME: Reconstruct dom info, because it is not preserved properly. if (Changed) DT->recalculate(*F); return Changed; } /// Do actual work and unswitch loop if possible and profitable. bool LoopUnswitch::processCurrentLoop() { bool Changed = false; initLoopData(); // If LoopSimplify was unable to form a preheader, don't do any unswitching. if (!loopPreheader) return false; // Loops with indirectbr cannot be cloned. if (!currentLoop->isSafeToClone()) return false; // Without dedicated exits, splitting the exit edge may fail. if (!currentLoop->hasDedicatedExits()) return false; LLVMContext &Context = loopHeader->getContext(); // Analyze loop cost, and stop unswitching if loop content can not be duplicated. if (!BranchesInfo.countLoop( currentLoop, getAnalysis<TargetTransformInfoWrapperPass>().getTTI( *currentLoop->getHeader()->getParent()), AC)) return false; // Try trivial unswitch first before loop over other basic blocks in the loop. if (TryTrivialLoopUnswitch(Changed)) { return true; } // Do not unswitch loops containing convergent operations, as we might be // making them control dependent on the unswitch value when they were not // before. // FIXME: This could be refined to only bail if the convergent operation is // not already control-dependent on the unswitch value. for (const auto BB : currentLoop->blocks()) { for (auto &I : *BB) { auto CS = CallSite(&I); if (!CS) continue; if (CS.hasFnAttr(Attribute::Convergent)) return false; } } // Do not do non-trivial unswitch while optimizing for size. // FIXME: Use Function::optForSize(). if (OptimizeForSize || loopHeader->getParent()->hasFnAttribute(Attribute::OptimizeForSize)) return false; if (LoopUnswitchWithBlockFrequency && EnabledPGO) { // Compute the weighted frequency of the hottest block in the // loop (loopHeader in this case since inner loops should be // processed before outer loop). If it is less than ColdFrequency, // we should not unswitch. BlockFrequency LoopEntryFreq = BFI.getBlockFreq(loopHeader); if (LoopEntryFreq < ColdEntryFreq) return false; } // Loop over all of the basic blocks in the loop. If we find an interior // block that is branching on a loop-invariant condition, we can unswitch this // loop. for (Loop::block_iterator I = currentLoop->block_begin(), E = currentLoop->block_end(); I != E; ++I) { TerminatorInst *TI = (*I)->getTerminator(); if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { // If this isn't branching on an invariant condition, we can't unswitch // it. if (BI->isConditional()) { // See if this, or some part of it, is loop invariant. If so, we can // unswitch on it if we desire. Value *LoopCond = FindLIVLoopCondition(BI->getCondition(), currentLoop, Changed); if (LoopCond && UnswitchIfProfitable(LoopCond, ConstantInt::getTrue(Context), TI)) { ++NumBranches; return true; } } } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { Value *LoopCond = FindLIVLoopCondition(SI->getCondition(), currentLoop, Changed); unsigned NumCases = SI->getNumCases(); if (LoopCond && NumCases) { // Find a value to unswitch on: // FIXME: this should chose the most expensive case! // FIXME: scan for a case with a non-critical edge? Constant *UnswitchVal = nullptr; // Do not process same value again and again. // At this point we have some cases already unswitched and // some not yet unswitched. Let's find the first not yet unswitched one. for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); i != e; ++i) { Constant *UnswitchValCandidate = i.getCaseValue(); if (!BranchesInfo.isUnswitched(SI, UnswitchValCandidate)) { UnswitchVal = UnswitchValCandidate; break; } } if (!UnswitchVal) continue; if (UnswitchIfProfitable(LoopCond, UnswitchVal)) { ++NumSwitches; return true; } } } // Scan the instructions to check for unswitchable values. for (BasicBlock::iterator BBI = (*I)->begin(), E = (*I)->end(); BBI != E; ++BBI) if (SelectInst *SI = dyn_cast<SelectInst>(BBI)) { Value *LoopCond = FindLIVLoopCondition(SI->getCondition(), currentLoop, Changed); if (LoopCond && UnswitchIfProfitable(LoopCond, ConstantInt::getTrue(Context))) { ++NumSelects; return true; } } } return Changed; } /// Check to see if all paths from BB exit the loop with no side effects /// (including infinite loops). /// /// If true, we return true and set ExitBB to the block we /// exit through. /// static bool isTrivialLoopExitBlockHelper(Loop *L, BasicBlock *BB, BasicBlock *&ExitBB, std::set<BasicBlock*> &Visited) { if (!Visited.insert(BB).second) { // Already visited. Without more analysis, this could indicate an infinite // loop. return false; } if (!L->contains(BB)) { // Otherwise, this is a loop exit, this is fine so long as this is the // first exit. if (ExitBB) return false; ExitBB = BB; return true; } // Otherwise, this is an unvisited intra-loop node. Check all successors. for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) { // Check to see if the successor is a trivial loop exit. if (!isTrivialLoopExitBlockHelper(L, *SI, ExitBB, Visited)) return false; } // Okay, everything after this looks good, check to make sure that this block // doesn't include any side effects. for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) if (I->mayHaveSideEffects()) return false; return true; } /// Return true if the specified block unconditionally leads to an exit from /// the specified loop, and has no side-effects in the process. If so, return /// the block that is exited to, otherwise return null. static BasicBlock *isTrivialLoopExitBlock(Loop *L, BasicBlock *BB) { std::set<BasicBlock*> Visited; Visited.insert(L->getHeader()); // Branches to header make infinite loops. BasicBlock *ExitBB = nullptr; if (isTrivialLoopExitBlockHelper(L, BB, ExitBB, Visited)) return ExitBB; return nullptr; } /// We have found that we can unswitch currentLoop when LoopCond == Val to /// simplify the loop. If we decide that this is profitable, /// unswitch the loop, reprocess the pieces, then return true. bool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val, TerminatorInst *TI) { // Check to see if it would be profitable to unswitch current loop. if (!BranchesInfo.CostAllowsUnswitching()) { DEBUG(dbgs() << "NOT unswitching loop %" << currentLoop->getHeader()->getName() << " at non-trivial condition '" << *Val << "' == " << *LoopCond << "\n" << ". Cost too high.\n"); return false; } UnswitchNontrivialCondition(LoopCond, Val, currentLoop, TI); return true; } /// Recursively clone the specified loop and all of its children, /// mapping the blocks with the specified map. static Loop *CloneLoop(Loop *L, Loop *PL, ValueToValueMapTy &VM, LoopInfo *LI, LPPassManager *LPM) { Loop &New = LPM->addLoop(PL); // Add all of the blocks in L to the new loop. for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); I != E; ++I) if (LI->getLoopFor(*I) == L) New.addBasicBlockToLoop(cast<BasicBlock>(VM[*I]), *LI); // Add all of the subloops to the new loop. for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I) CloneLoop(*I, &New, VM, LI, LPM); return &New; } static void copyMetadata(Instruction *DstInst, const Instruction *SrcInst, bool Swapped) { if (!SrcInst || !SrcInst->hasMetadata()) return; SmallVector<std::pair<unsigned, MDNode *>, 4> MDs; SrcInst->getAllMetadata(MDs); for (auto &MD : MDs) { switch (MD.first) { default: break; case LLVMContext::MD_prof: if (Swapped && MD.second->getNumOperands() == 3 && isa<MDString>(MD.second->getOperand(0))) { MDString *MDName = cast<MDString>(MD.second->getOperand(0)); if (MDName->getString() == "branch_weights") { auto *ValT = cast_or_null<ConstantAsMetadata>( MD.second->getOperand(1))->getValue(); auto *ValF = cast_or_null<ConstantAsMetadata>( MD.second->getOperand(2))->getValue(); assert(ValT && ValF && "Invalid Operands of branch_weights"); auto NewMD = MDBuilder(DstInst->getParent()->getContext()) .createBranchWeights(cast<ConstantInt>(ValF)->getZExtValue(), cast<ConstantInt>(ValT)->getZExtValue()); MD.second = NewMD; } } // fallthrough. case LLVMContext::MD_make_implicit: case LLVMContext::MD_dbg: DstInst->setMetadata(MD.first, MD.second); } } } /// Emit a conditional branch on two values if LIC == Val, branch to TrueDst, /// otherwise branch to FalseDest. Insert the code immediately before InsertPt. void LoopUnswitch::EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val, BasicBlock *TrueDest, BasicBlock *FalseDest, Instruction *InsertPt, TerminatorInst *TI) { // Insert a conditional branch on LIC to the two preheaders. The original // code is the true version and the new code is the false version. Value *BranchVal = LIC; bool Swapped = false; if (!isa<ConstantInt>(Val) || Val->getType() != Type::getInt1Ty(LIC->getContext())) BranchVal = new ICmpInst(InsertPt, ICmpInst::ICMP_EQ, LIC, Val); else if (Val != ConstantInt::getTrue(Val->getContext())) { // We want to enter the new loop when the condition is true. std::swap(TrueDest, FalseDest); Swapped = true; } // Insert the new branch. BranchInst *BI = BranchInst::Create(TrueDest, FalseDest, BranchVal, InsertPt); copyMetadata(BI, TI, Swapped); // If either edge is critical, split it. This helps preserve LoopSimplify // form for enclosing loops. auto Options = CriticalEdgeSplittingOptions(DT, LI).setPreserveLCSSA(); SplitCriticalEdge(BI, 0, Options); SplitCriticalEdge(BI, 1, Options); } /// Given a loop that has a trivial unswitchable condition in it (a cond branch /// from its header block to its latch block, where the path through the loop /// that doesn't execute its body has no side-effects), unswitch it. This /// doesn't involve any code duplication, just moving the conditional branch /// outside of the loop and updating loop info. void LoopUnswitch::UnswitchTrivialCondition(Loop *L, Value *Cond, Constant *Val, BasicBlock *ExitBlock, TerminatorInst *TI) { DEBUG(dbgs() << "loop-unswitch: Trivial-Unswitch loop %" << loopHeader->getName() << " [" << L->getBlocks().size() << " blocks] in Function " << L->getHeader()->getParent()->getName() << " on cond: " << *Val << " == " << *Cond << "\n"); // First step, split the preheader, so that we know that there is a safe place // to insert the conditional branch. We will change loopPreheader to have a // conditional branch on Cond. BasicBlock *NewPH = SplitEdge(loopPreheader, loopHeader, DT, LI); // Now that we have a place to insert the conditional branch, create a place // to branch to: this is the exit block out of the loop that we should // short-circuit to. // Split this block now, so that the loop maintains its exit block, and so // that the jump from the preheader can execute the contents of the exit block // without actually branching to it (the exit block should be dominated by the // loop header, not the preheader). assert(!L->contains(ExitBlock) && "Exit block is in the loop?"); BasicBlock *NewExit = SplitBlock(ExitBlock, &ExitBlock->front(), DT, LI); // Okay, now we have a position to branch from and a position to branch to, // insert the new conditional branch. EmitPreheaderBranchOnCondition(Cond, Val, NewExit, NewPH, loopPreheader->getTerminator(), TI); LPM->deleteSimpleAnalysisValue(loopPreheader->getTerminator(), L); loopPreheader->getTerminator()->eraseFromParent(); // We need to reprocess this loop, it could be unswitched again. redoLoop = true; // Now that we know that the loop is never entered when this condition is a // particular value, rewrite the loop with this info. We know that this will // at least eliminate the old branch. RewriteLoopBodyWithConditionConstant(L, Cond, Val, false); ++NumTrivial; } /// Check if the first non-constant condition starting from the loop header is /// a trivial unswitch condition: that is, a condition controls whether or not /// the loop does anything at all. If it is a trivial condition, unswitching /// produces no code duplications (equivalently, it produces a simpler loop and /// a new empty loop, which gets deleted). Therefore always unswitch trivial /// condition. bool LoopUnswitch::TryTrivialLoopUnswitch(bool &Changed) { BasicBlock *CurrentBB = currentLoop->getHeader(); TerminatorInst *CurrentTerm = CurrentBB->getTerminator(); LLVMContext &Context = CurrentBB->getContext(); // If loop header has only one reachable successor (currently via an // unconditional branch or constant foldable conditional branch, but // should also consider adding constant foldable switch instruction in // future), we should keep looking for trivial condition candidates in // the successor as well. An alternative is to constant fold conditions // and merge successors into loop header (then we only need to check header's // terminator). The reason for not doing this in LoopUnswitch pass is that // it could potentially break LoopPassManager's invariants. Folding dead // branches could either eliminate the current loop or make other loops // unreachable. LCSSA form might also not be preserved after deleting // branches. The following code keeps traversing loop header's successors // until it finds the trivial condition candidate (condition that is not a // constant). Since unswitching generates branches with constant conditions, // this scenario could be very common in practice. SmallSet<BasicBlock*, 8> Visited; while (true) { // If we exit loop or reach a previous visited block, then // we can not reach any trivial condition candidates (unfoldable // branch instructions or switch instructions) and no unswitch // can happen. Exit and return false. if (!currentLoop->contains(CurrentBB) || !Visited.insert(CurrentBB).second) return false; // Check if this loop will execute any side-effecting instructions (e.g. // stores, calls, volatile loads) in the part of the loop that the code // *would* execute. Check the header first. for (Instruction &I : *CurrentBB) if (I.mayHaveSideEffects()) return false; // FIXME: add check for constant foldable switch instructions. if (BranchInst *BI = dyn_cast<BranchInst>(CurrentTerm)) { if (BI->isUnconditional()) { CurrentBB = BI->getSuccessor(0); } else if (BI->getCondition() == ConstantInt::getTrue(Context)) { CurrentBB = BI->getSuccessor(0); } else if (BI->getCondition() == ConstantInt::getFalse(Context)) { CurrentBB = BI->getSuccessor(1); } else { // Found a trivial condition candidate: non-foldable conditional branch. break; } } else { break; } CurrentTerm = CurrentBB->getTerminator(); } // CondVal is the condition that controls the trivial condition. // LoopExitBB is the BasicBlock that loop exits when meets trivial condition. Constant *CondVal = nullptr; BasicBlock *LoopExitBB = nullptr; if (BranchInst *BI = dyn_cast<BranchInst>(CurrentTerm)) { // If this isn't branching on an invariant condition, we can't unswitch it. if (!BI->isConditional()) return false; Value *LoopCond = FindLIVLoopCondition(BI->getCondition(), currentLoop, Changed); // Unswitch only if the trivial condition itself is an LIV (not // partial LIV which could occur in and/or) if (!LoopCond || LoopCond != BI->getCondition()) return false; // Check to see if a successor of the branch is guaranteed to // exit through a unique exit block without having any // side-effects. If so, determine the value of Cond that causes // it to do this. if ((LoopExitBB = isTrivialLoopExitBlock(currentLoop, BI->getSuccessor(0)))) { CondVal = ConstantInt::getTrue(Context); } else if ((LoopExitBB = isTrivialLoopExitBlock(currentLoop, BI->getSuccessor(1)))) { CondVal = ConstantInt::getFalse(Context); } // If we didn't find a single unique LoopExit block, or if the loop exit // block contains phi nodes, this isn't trivial. if (!LoopExitBB || isa<PHINode>(LoopExitBB->begin())) return false; // Can't handle this. UnswitchTrivialCondition(currentLoop, LoopCond, CondVal, LoopExitBB, CurrentTerm); ++NumBranches; return true; } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurrentTerm)) { // If this isn't switching on an invariant condition, we can't unswitch it. Value *LoopCond = FindLIVLoopCondition(SI->getCondition(), currentLoop, Changed); // Unswitch only if the trivial condition itself is an LIV (not // partial LIV which could occur in and/or) if (!LoopCond || LoopCond != SI->getCondition()) return false; // Check to see if a successor of the switch is guaranteed to go to the // latch block or exit through a one exit block without having any // side-effects. If so, determine the value of Cond that causes it to do // this. // Note that we can't trivially unswitch on the default case or // on already unswitched cases. for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); i != e; ++i) { BasicBlock *LoopExitCandidate; if ((LoopExitCandidate = isTrivialLoopExitBlock(currentLoop, i.getCaseSuccessor()))) { // Okay, we found a trivial case, remember the value that is trivial. ConstantInt *CaseVal = i.getCaseValue(); // Check that it was not unswitched before, since already unswitched // trivial vals are looks trivial too. if (BranchesInfo.isUnswitched(SI, CaseVal)) continue; LoopExitBB = LoopExitCandidate; CondVal = CaseVal; break; } } // If we didn't find a single unique LoopExit block, or if the loop exit // block contains phi nodes, this isn't trivial. if (!LoopExitBB || isa<PHINode>(LoopExitBB->begin())) return false; // Can't handle this. UnswitchTrivialCondition(currentLoop, LoopCond, CondVal, LoopExitBB, nullptr); ++NumSwitches; return true; } return false; } /// Split all of the edges from inside the loop to their exit blocks. /// Update the appropriate Phi nodes as we do so. void LoopUnswitch::SplitExitEdges(Loop *L, const SmallVectorImpl<BasicBlock *> &ExitBlocks){ for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { BasicBlock *ExitBlock = ExitBlocks[i]; SmallVector<BasicBlock *, 4> Preds(pred_begin(ExitBlock), pred_end(ExitBlock)); // Although SplitBlockPredecessors doesn't preserve loop-simplify in // general, if we call it on all predecessors of all exits then it does. SplitBlockPredecessors(ExitBlock, Preds, ".us-lcssa", DT, LI, /*PreserveLCSSA*/ true); } } /// We determined that the loop is profitable to unswitch when LIC equal Val. /// Split it into loop versions and test the condition outside of either loop. /// Return the loops created as Out1/Out2. void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val, Loop *L, TerminatorInst *TI) { Function *F = loopHeader->getParent(); DEBUG(dbgs() << "loop-unswitch: Unswitching loop %" << loopHeader->getName() << " [" << L->getBlocks().size() << " blocks] in Function " << F->getName() << " when '" << *Val << "' == " << *LIC << "\n"); if (auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>()) SEWP->getSE().forgetLoop(L); LoopBlocks.clear(); NewBlocks.clear(); // First step, split the preheader and exit blocks, and add these blocks to // the LoopBlocks list. BasicBlock *NewPreheader = SplitEdge(loopPreheader, loopHeader, DT, LI); LoopBlocks.push_back(NewPreheader); // We want the loop to come after the preheader, but before the exit blocks. LoopBlocks.insert(LoopBlocks.end(), L->block_begin(), L->block_end()); SmallVector<BasicBlock*, 8> ExitBlocks; L->getUniqueExitBlocks(ExitBlocks); // Split all of the edges from inside the loop to their exit blocks. Update // the appropriate Phi nodes as we do so. SplitExitEdges(L, ExitBlocks); // The exit blocks may have been changed due to edge splitting, recompute. ExitBlocks.clear(); L->getUniqueExitBlocks(ExitBlocks); // Add exit blocks to the loop blocks. LoopBlocks.insert(LoopBlocks.end(), ExitBlocks.begin(), ExitBlocks.end()); // Next step, clone all of the basic blocks that make up the loop (including // the loop preheader and exit blocks), keeping track of the mapping between // the instructions and blocks. NewBlocks.reserve(LoopBlocks.size()); ValueToValueMapTy VMap; for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) { BasicBlock *NewBB = CloneBasicBlock(LoopBlocks[i], VMap, ".us", F); NewBlocks.push_back(NewBB); VMap[LoopBlocks[i]] = NewBB; // Keep the BB mapping. LPM->cloneBasicBlockSimpleAnalysis(LoopBlocks[i], NewBB, L); } // Splice the newly inserted blocks into the function right before the // original preheader. F->getBasicBlockList().splice(NewPreheader->getIterator(), F->getBasicBlockList(), NewBlocks[0]->getIterator(), F->end()); // FIXME: We could register any cloned assumptions instead of clearing the // whole function's cache. AC->clear(); // Now we create the new Loop object for the versioned loop. Loop *NewLoop = CloneLoop(L, L->getParentLoop(), VMap, LI, LPM); // Recalculate unswitching quota, inherit simplified switches info for NewBB, // Probably clone more loop-unswitch related loop properties. BranchesInfo.cloneData(NewLoop, L, VMap); Loop *ParentLoop = L->getParentLoop(); if (ParentLoop) { // Make sure to add the cloned preheader and exit blocks to the parent loop // as well. ParentLoop->addBasicBlockToLoop(NewBlocks[0], *LI); } for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { BasicBlock *NewExit = cast<BasicBlock>(VMap[ExitBlocks[i]]); // The new exit block should be in the same loop as the old one. if (Loop *ExitBBLoop = LI->getLoopFor(ExitBlocks[i])) ExitBBLoop->addBasicBlockToLoop(NewExit, *LI); assert(NewExit->getTerminator()->getNumSuccessors() == 1 && "Exit block should have been split to have one successor!"); BasicBlock *ExitSucc = NewExit->getTerminator()->getSuccessor(0); // If the successor of the exit block had PHI nodes, add an entry for // NewExit. for (BasicBlock::iterator I = ExitSucc->begin(); PHINode *PN = dyn_cast<PHINode>(I); ++I) { Value *V = PN->getIncomingValueForBlock(ExitBlocks[i]); ValueToValueMapTy::iterator It = VMap.find(V); if (It != VMap.end()) V = It->second; PN->addIncoming(V, NewExit); } if (LandingPadInst *LPad = NewExit->getLandingPadInst()) { PHINode *PN = PHINode::Create(LPad->getType(), 0, "", &*ExitSucc->getFirstInsertionPt()); for (pred_iterator I = pred_begin(ExitSucc), E = pred_end(ExitSucc); I != E; ++I) { BasicBlock *BB = *I; LandingPadInst *LPI = BB->getLandingPadInst(); LPI->replaceAllUsesWith(PN); PN->addIncoming(LPI, BB); } } } // Rewrite the code to refer to itself. for (unsigned i = 0, e = NewBlocks.size(); i != e; ++i) for (BasicBlock::iterator I = NewBlocks[i]->begin(), E = NewBlocks[i]->end(); I != E; ++I) RemapInstruction(&*I, VMap, RF_NoModuleLevelChanges | RF_IgnoreMissingEntries); // Rewrite the original preheader to select between versions of the loop. BranchInst *OldBR = cast<BranchInst>(loopPreheader->getTerminator()); assert(OldBR->isUnconditional() && OldBR->getSuccessor(0) == LoopBlocks[0] && "Preheader splitting did not work correctly!"); // Emit the new branch that selects between the two versions of this loop. EmitPreheaderBranchOnCondition(LIC, Val, NewBlocks[0], LoopBlocks[0], OldBR, TI); LPM->deleteSimpleAnalysisValue(OldBR, L); OldBR->eraseFromParent(); LoopProcessWorklist.push_back(NewLoop); redoLoop = true; // Keep a WeakVH holding onto LIC. If the first call to RewriteLoopBody // deletes the instruction (for example by simplifying a PHI that feeds into // the condition that we're unswitching on), we don't rewrite the second // iteration. WeakVH LICHandle(LIC); // Now we rewrite the original code to know that the condition is true and the // new code to know that the condition is false. RewriteLoopBodyWithConditionConstant(L, LIC, Val, false); // It's possible that simplifying one loop could cause the other to be // changed to another value or a constant. If its a constant, don't simplify // it. if (!LoopProcessWorklist.empty() && LoopProcessWorklist.back() == NewLoop && LICHandle && !isa<Constant>(LICHandle)) RewriteLoopBodyWithConditionConstant(NewLoop, LICHandle, Val, true); } /// Remove all instances of I from the worklist vector specified. static void RemoveFromWorklist(Instruction *I, std::vector<Instruction*> &Worklist) { Worklist.erase(std::remove(Worklist.begin(), Worklist.end(), I), Worklist.end()); } /// When we find that I really equals V, remove I from the /// program, replacing all uses with V and update the worklist. static void ReplaceUsesOfWith(Instruction *I, Value *V, std::vector<Instruction*> &Worklist, Loop *L, LPPassManager *LPM) { DEBUG(dbgs() << "Replace with '" << *V << "': " << *I); // Add uses to the worklist, which may be dead now. for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) if (Instruction *Use = dyn_cast<Instruction>(I->getOperand(i))) Worklist.push_back(Use); // Add users to the worklist which may be simplified now. for (User *U : I->users()) Worklist.push_back(cast<Instruction>(U)); LPM->deleteSimpleAnalysisValue(I, L); RemoveFromWorklist(I, Worklist); I->replaceAllUsesWith(V); I->eraseFromParent(); ++NumSimplify; } /// We know either that the value LIC has the value specified by Val in the /// specified loop, or we know it does NOT have that value. /// Rewrite any uses of LIC or of properties correlated to it. void LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC, Constant *Val, bool IsEqual) { assert(!isa<Constant>(LIC) && "Why are we unswitching on a constant?"); // FIXME: Support correlated properties, like: // for (...) // if (li1 < li2) // ... // if (li1 > li2) // ... // FOLD boolean conditions (X|LIC), (X&LIC). Fold conditional branches, // selects, switches. std::vector<Instruction*> Worklist; LLVMContext &Context = Val->getContext(); // If we know that LIC == Val, or that LIC == NotVal, just replace uses of LIC // in the loop with the appropriate one directly. if (IsEqual || (isa<ConstantInt>(Val) && Val->getType()->isIntegerTy(1))) { Value *Replacement; if (IsEqual) Replacement = Val; else Replacement = ConstantInt::get(Type::getInt1Ty(Val->getContext()), !cast<ConstantInt>(Val)->getZExtValue()); for (User *U : LIC->users()) { Instruction *UI = dyn_cast<Instruction>(U); if (!UI || !L->contains(UI)) continue; Worklist.push_back(UI); } for (std::vector<Instruction*>::iterator UI = Worklist.begin(), UE = Worklist.end(); UI != UE; ++UI) (*UI)->replaceUsesOfWith(LIC, Replacement); SimplifyCode(Worklist, L); return; } // Otherwise, we don't know the precise value of LIC, but we do know that it // is certainly NOT "Val". As such, simplify any uses in the loop that we // can. This case occurs when we unswitch switch statements. for (User *U : LIC->users()) { Instruction *UI = dyn_cast<Instruction>(U); if (!UI || !L->contains(UI)) continue; Worklist.push_back(UI); // TODO: We could do other simplifications, for example, turning // 'icmp eq LIC, Val' -> false. // If we know that LIC is not Val, use this info to simplify code. SwitchInst *SI = dyn_cast<SwitchInst>(UI); if (!SI || !isa<ConstantInt>(Val)) continue; SwitchInst::CaseIt DeadCase = SI->findCaseValue(cast<ConstantInt>(Val)); // Default case is live for multiple values. if (DeadCase == SI->case_default()) continue; // Found a dead case value. Don't remove PHI nodes in the // successor if they become single-entry, those PHI nodes may // be in the Users list. BasicBlock *Switch = SI->getParent(); BasicBlock *SISucc = DeadCase.getCaseSuccessor(); BasicBlock *Latch = L->getLoopLatch(); BranchesInfo.setUnswitched(SI, Val); if (!SI->findCaseDest(SISucc)) continue; // Edge is critical. // If the DeadCase successor dominates the loop latch, then the // transformation isn't safe since it will delete the sole predecessor edge // to the latch. if (Latch && DT->dominates(SISucc, Latch)) continue; // FIXME: This is a hack. We need to keep the successor around // and hooked up so as to preserve the loop structure, because // trying to update it is complicated. So instead we preserve the // loop structure and put the block on a dead code path. SplitEdge(Switch, SISucc, DT, LI); // Compute the successors instead of relying on the return value // of SplitEdge, since it may have split the switch successor // after PHI nodes. BasicBlock *NewSISucc = DeadCase.getCaseSuccessor(); BasicBlock *OldSISucc = *succ_begin(NewSISucc); // Create an "unreachable" destination. BasicBlock *Abort = BasicBlock::Create(Context, "us-unreachable", Switch->getParent(), OldSISucc); new UnreachableInst(Context, Abort); // Force the new case destination to branch to the "unreachable" // block while maintaining a (dead) CFG edge to the old block. NewSISucc->getTerminator()->eraseFromParent(); BranchInst::Create(Abort, OldSISucc, ConstantInt::getTrue(Context), NewSISucc); // Release the PHI operands for this edge. for (BasicBlock::iterator II = NewSISucc->begin(); PHINode *PN = dyn_cast<PHINode>(II); ++II) PN->setIncomingValue(PN->getBasicBlockIndex(Switch), UndefValue::get(PN->getType())); // Tell the domtree about the new block. We don't fully update the // domtree here -- instead we force it to do a full recomputation // after the pass is complete -- but we do need to inform it of // new blocks. DT->addNewBlock(Abort, NewSISucc); } SimplifyCode(Worklist, L); } /// Now that we have simplified some instructions in the loop, walk over it and /// constant prop, dce, and fold control flow where possible. Note that this is /// effectively a very simple loop-structure-aware optimizer. During processing /// of this loop, L could very well be deleted, so it must not be used. /// /// FIXME: When the loop optimizer is more mature, separate this out to a new /// pass. /// void LoopUnswitch::SimplifyCode(std::vector<Instruction*> &Worklist, Loop *L) { const DataLayout &DL = L->getHeader()->getModule()->getDataLayout(); while (!Worklist.empty()) { Instruction *I = Worklist.back(); Worklist.pop_back(); // Simple DCE. if (isInstructionTriviallyDead(I)) { DEBUG(dbgs() << "Remove dead instruction '" << *I); // Add uses to the worklist, which may be dead now. for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) if (Instruction *Use = dyn_cast<Instruction>(I->getOperand(i))) Worklist.push_back(Use); LPM->deleteSimpleAnalysisValue(I, L); RemoveFromWorklist(I, Worklist); I->eraseFromParent(); ++NumSimplify; continue; } // See if instruction simplification can hack this up. This is common for // things like "select false, X, Y" after unswitching made the condition be // 'false'. TODO: update the domtree properly so we can pass it here. if (Value *V = SimplifyInstruction(I, DL)) if (LI->replacementPreservesLCSSAForm(I, V)) { ReplaceUsesOfWith(I, V, Worklist, L, LPM); continue; } // Special case hacks that appear commonly in unswitched code. if (BranchInst *BI = dyn_cast<BranchInst>(I)) { if (BI->isUnconditional()) { // If BI's parent is the only pred of the successor, fold the two blocks // together. BasicBlock *Pred = BI->getParent(); BasicBlock *Succ = BI->getSuccessor(0); BasicBlock *SinglePred = Succ->getSinglePredecessor(); if (!SinglePred) continue; // Nothing to do. assert(SinglePred == Pred && "CFG broken"); DEBUG(dbgs() << "Merging blocks: " << Pred->getName() << " <- " << Succ->getName() << "\n"); // Resolve any single entry PHI nodes in Succ. while (PHINode *PN = dyn_cast<PHINode>(Succ->begin())) ReplaceUsesOfWith(PN, PN->getIncomingValue(0), Worklist, L, LPM); // If Succ has any successors with PHI nodes, update them to have // entries coming from Pred instead of Succ. Succ->replaceAllUsesWith(Pred); // Move all of the successor contents from Succ to Pred. Pred->getInstList().splice(BI->getIterator(), Succ->getInstList(), Succ->begin(), Succ->end()); LPM->deleteSimpleAnalysisValue(BI, L); BI->eraseFromParent(); RemoveFromWorklist(BI, Worklist); // Remove Succ from the loop tree. LI->removeBlock(Succ); LPM->deleteSimpleAnalysisValue(Succ, L); Succ->eraseFromParent(); ++NumSimplify; continue; } continue; } } }