| //===- IndVarSimplify.cpp - Induction Variable Elimination ----------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // Guarantees that all loops with identifiable, linear, induction variables will |
| // be transformed to have a single, canonical, induction variable. After this |
| // pass runs, it guarantees the the first PHI node of the header block in the |
| // loop is the canonical induction variable if there is one. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/Analysis/InductionVariable.h" |
| #include "llvm/Analysis/LoopInfo.h" |
| #include "llvm/iPHINode.h" |
| #include "llvm/iOther.h" |
| #include "llvm/Type.h" |
| #include "llvm/Constants.h" |
| #include "llvm/Support/CFG.h" |
| #include "Support/Debug.h" |
| #include "Support/Statistic.h" |
| #include "Support/STLExtras.h" |
| |
| namespace llvm { |
| |
| namespace { |
| Statistic<> NumRemoved ("indvars", "Number of aux indvars removed"); |
| Statistic<> NumInserted("indvars", "Number of canonical indvars added"); |
| } |
| |
| // InsertCast - Cast Val to Ty, setting a useful name on the cast if Val has a |
| // name... |
| // |
| static Instruction *InsertCast(Value *Val, const Type *Ty, |
| Instruction *InsertBefore) { |
| return new CastInst(Val, Ty, Val->getName()+"-casted", InsertBefore); |
| } |
| |
| static bool TransformLoop(LoopInfo *Loops, Loop *Loop) { |
| // Transform all subloops before this loop... |
| bool Changed = reduce_apply_bool(Loop->getSubLoops().begin(), |
| Loop->getSubLoops().end(), |
| std::bind1st(std::ptr_fun(TransformLoop), Loops)); |
| // Get the header node for this loop. All of the phi nodes that could be |
| // induction variables must live in this basic block. |
| // |
| BasicBlock *Header = Loop->getHeader(); |
| |
| // Loop over all of the PHI nodes in the basic block, calculating the |
| // induction variables that they represent... stuffing the induction variable |
| // info into a vector... |
| // |
| std::vector<InductionVariable> IndVars; // Induction variables for block |
| BasicBlock::iterator AfterPHIIt = Header->begin(); |
| for (; PHINode *PN = dyn_cast<PHINode>(AfterPHIIt); ++AfterPHIIt) |
| IndVars.push_back(InductionVariable(PN, Loops)); |
| // AfterPHIIt now points to first non-phi instruction... |
| |
| // If there are no phi nodes in this basic block, there can't be indvars... |
| if (IndVars.empty()) return Changed; |
| |
| // Loop over the induction variables, looking for a canonical induction |
| // variable, and checking to make sure they are not all unknown induction |
| // variables. |
| // |
| bool FoundIndVars = false; |
| InductionVariable *Canonical = 0; |
| for (unsigned i = 0; i < IndVars.size(); ++i) { |
| if (IndVars[i].InductionType == InductionVariable::Canonical && |
| !isa<PointerType>(IndVars[i].Phi->getType())) |
| Canonical = &IndVars[i]; |
| if (IndVars[i].InductionType != InductionVariable::Unknown) |
| FoundIndVars = true; |
| } |
| |
| // No induction variables, bail early... don't add a canonical indvar |
| if (!FoundIndVars) return Changed; |
| |
| // Okay, we want to convert other induction variables to use a canonical |
| // indvar. If we don't have one, add one now... |
| if (!Canonical) { |
| // Create the PHI node for the new induction variable, and insert the phi |
| // node at the start of the PHI nodes... |
| PHINode *PN = new PHINode(Type::UIntTy, "cann-indvar", Header->begin()); |
| |
| // Create the increment instruction to add one to the counter... |
| Instruction *Add = BinaryOperator::create(Instruction::Add, PN, |
| ConstantUInt::get(Type::UIntTy,1), |
| "add1-indvar", AfterPHIIt); |
| |
| // Figure out which block is incoming and which is the backedge for the loop |
| BasicBlock *Incoming, *BackEdgeBlock; |
| pred_iterator PI = pred_begin(Header); |
| assert(PI != pred_end(Header) && "Loop headers should have 2 preds!"); |
| if (Loop->contains(*PI)) { // First pred is back edge... |
| BackEdgeBlock = *PI++; |
| Incoming = *PI++; |
| } else { |
| Incoming = *PI++; |
| BackEdgeBlock = *PI++; |
| } |
| assert(PI == pred_end(Header) && "Loop headers should have 2 preds!"); |
| |
| // Add incoming values for the PHI node... |
| PN->addIncoming(Constant::getNullValue(Type::UIntTy), Incoming); |
| PN->addIncoming(Add, BackEdgeBlock); |
| |
| // Analyze the new induction variable... |
| IndVars.push_back(InductionVariable(PN, Loops)); |
| assert(IndVars.back().InductionType == InductionVariable::Canonical && |
| "Just inserted canonical indvar that is not canonical!"); |
| Canonical = &IndVars.back(); |
| ++NumInserted; |
| Changed = true; |
| } else { |
| // If we have a canonical induction variable, make sure that it is the first |
| // one in the basic block. |
| if (&Header->front() != Canonical->Phi) |
| Header->getInstList().splice(Header->begin(), Header->getInstList(), |
| Canonical->Phi); |
| } |
| |
| DEBUG(std::cerr << "Induction variables:\n"); |
| |
| // Get the current loop iteration count, which is always the value of the |
| // canonical phi node... |
| // |
| PHINode *IterCount = Canonical->Phi; |
| |
| // Loop through and replace all of the auxiliary induction variables with |
| // references to the canonical induction variable... |
| // |
| for (unsigned i = 0; i < IndVars.size(); ++i) { |
| InductionVariable *IV = &IndVars[i]; |
| |
| DEBUG(IV->print(std::cerr)); |
| |
| // Don't do math with pointers... |
| const Type *IVTy = IV->Phi->getType(); |
| if (isa<PointerType>(IVTy)) IVTy = Type::ULongTy; |
| |
| // Don't modify the canonical indvar or unrecognized indvars... |
| if (IV != Canonical && IV->InductionType != InductionVariable::Unknown) { |
| Instruction *Val = IterCount; |
| if (!isa<ConstantInt>(IV->Step) || // If the step != 1 |
| !cast<ConstantInt>(IV->Step)->equalsInt(1)) { |
| |
| // If the types are not compatible, insert a cast now... |
| if (Val->getType() != IVTy) |
| Val = InsertCast(Val, IVTy, AfterPHIIt); |
| if (IV->Step->getType() != IVTy) |
| IV->Step = InsertCast(IV->Step, IVTy, AfterPHIIt); |
| |
| Val = BinaryOperator::create(Instruction::Mul, Val, IV->Step, |
| IV->Phi->getName()+"-scale", AfterPHIIt); |
| } |
| |
| // If the start != 0 |
| if (IV->Start != Constant::getNullValue(IV->Start->getType())) { |
| // If the types are not compatible, insert a cast now... |
| if (Val->getType() != IVTy) |
| Val = InsertCast(Val, IVTy, AfterPHIIt); |
| if (IV->Start->getType() != IVTy) |
| IV->Start = InsertCast(IV->Start, IVTy, AfterPHIIt); |
| |
| // Insert the instruction after the phi nodes... |
| Val = BinaryOperator::create(Instruction::Add, Val, IV->Start, |
| IV->Phi->getName()+"-offset", AfterPHIIt); |
| } |
| |
| // If the PHI node has a different type than val is, insert a cast now... |
| if (Val->getType() != IV->Phi->getType()) |
| Val = InsertCast(Val, IV->Phi->getType(), AfterPHIIt); |
| |
| // Replace all uses of the old PHI node with the new computed value... |
| IV->Phi->replaceAllUsesWith(Val); |
| |
| // Move the PHI name to it's new equivalent value... |
| std::string OldName = IV->Phi->getName(); |
| IV->Phi->setName(""); |
| Val->setName(OldName); |
| |
| // Delete the old, now unused, phi node... |
| Header->getInstList().erase(IV->Phi); |
| Changed = true; |
| ++NumRemoved; |
| } |
| } |
| |
| return Changed; |
| } |
| |
| namespace { |
| struct InductionVariableSimplify : public FunctionPass { |
| virtual bool runOnFunction(Function &) { |
| LoopInfo &LI = getAnalysis<LoopInfo>(); |
| |
| // Induction Variables live in the header nodes of loops |
| return reduce_apply_bool(LI.getTopLevelLoops().begin(), |
| LI.getTopLevelLoops().end(), |
| std::bind1st(std::ptr_fun(TransformLoop), &LI)); |
| } |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<LoopInfo>(); |
| AU.addRequiredID(LoopSimplifyID); |
| AU.setPreservesCFG(); |
| } |
| }; |
| RegisterOpt<InductionVariableSimplify> X("indvars", |
| "Canonicalize Induction Variables"); |
| } |
| |
| Pass *createIndVarSimplifyPass() { |
| return new InductionVariableSimplify(); |
| } |
| |
| } // End llvm namespace |