| //===- IndVarSimplify.cpp - Induction Variable Elimination ----------------===// |
| // |
| // InductionVariableSimplify - Transform induction variables in a program |
| // to all use a single cannonical induction variable per loop. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Transforms/Scalar/IndVarSimplify.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/BasicBlock.h" |
| #include "llvm/Constants.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/CFG.h" |
| #include "Support/STLExtras.h" |
| |
| #if 0 |
| #define DEBUG |
| #include "llvm/Analysis/Writer.h" |
| #endif |
| |
| // InsertCast - Cast Val to Ty, setting a useful name on the cast if Val has a |
| // name... |
| // |
| static Instruction *InsertCast(Instruction *Val, const Type *Ty, |
| BasicBlock::iterator It) { |
| Instruction *Cast = new CastInst(Val, Ty); |
| if (Val->hasName()) Cast->setName(Val->getName()+"-casted"); |
| Val->getParent()->getInstList().insert(It, Cast); |
| return Cast; |
| } |
| |
| 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 = (BasicBlock*)Loop->getBlocks().front(); |
| |
| // 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 |
| for (BasicBlock::iterator I = Header->begin(); |
| PHINode *PN = dyn_cast<PHINode>(*I); ++I) |
| IndVars.push_back(InductionVariable(PN, Loops)); |
| |
| // 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 cannonical induction |
| // variable, and checking to make sure they are not all unknown induction |
| // variables. |
| // |
| bool FoundIndVars = false; |
| InductionVariable *Cannonical = 0; |
| for (unsigned i = 0; i < IndVars.size(); ++i) { |
| if (IndVars[i].InductionType == InductionVariable::Cannonical) |
| Cannonical = &IndVars[i]; |
| if (IndVars[i].InductionType != InductionVariable::Unknown) |
| FoundIndVars = true; |
| } |
| |
| // No induction variables, bail early... don't add a cannonnical indvar |
| if (!FoundIndVars) return Changed; |
| |
| // Okay, we want to convert other induction variables to use a cannonical |
| // indvar. If we don't have one, add one now... |
| if (!Cannonical) { |
| // Create the PHI node for the new induction variable |
| PHINode *PN = new PHINode(Type::UIntTy, "cann-indvar"); |
| |
| // Insert the phi node at the end of the other phi nodes... |
| Header->getInstList().insert(Header->begin()+IndVars.size(), PN); |
| |
| // Create the increment instruction to add one to the counter... |
| Instruction *Add = BinaryOperator::create(Instruction::Add, PN, |
| ConstantUInt::get(Type::UIntTy,1), |
| "add1-indvar"); |
| |
| // Insert the add instruction after all of the PHI nodes... |
| Header->getInstList().insert(Header->begin()+(IndVars.size()+1), Add); |
| |
| // 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::Cannonical && |
| "Just inserted cannonical indvar that is not cannonical!"); |
| Cannonical = &IndVars.back(); |
| Changed = true; |
| } |
| |
| #ifdef DEBUG |
| cerr << "Induction variables:\n"; |
| #endif |
| |
| // Get the current loop iteration count, which is always the value of the |
| // cannonical phi node... |
| // |
| PHINode *IterCount = Cannonical->Phi; |
| |
| // Loop through and replace all of the auxillary induction variables with |
| // references to the primary induction variable... |
| // |
| unsigned InsertPos = IndVars.size(); |
| for (unsigned i = 0; i < IndVars.size(); ++i) { |
| InductionVariable *IV = &IndVars[i]; |
| #ifdef DEBUG |
| cerr << IndVars[i]; |
| #endif |
| // Don't modify the cannonical indvar or unrecognized indvars... |
| if (IV != Cannonical && IV->InductionType != InductionVariable::Unknown) { |
| Instruction *Val = IterCount; |
| if (!isa<ConstantInt>(IV->Step) || // If the step != 1 |
| !cast<ConstantInt>(IV->Step)->equalsInt(1)) { |
| std::string Name; // Create a scale by the step value... |
| if (IV->Phi->hasName()) Name = IV->Phi->getName()+"-scale"; |
| |
| // If the types are not compatible, insert a cast now... |
| if (Val->getType() != IV->Step->getType()) |
| Val = InsertCast(Val, IV->Step->getType(), |
| Header->begin()+InsertPos++); |
| |
| Val = BinaryOperator::create(Instruction::Mul, Val, IV->Step, Name); |
| // Insert the phi node at the end of the other phi nodes... |
| Header->getInstList().insert(Header->begin()+InsertPos++, Val); |
| } |
| |
| if (!isa<Constant>(IV->Start) || // If the start != 0 |
| !cast<Constant>(IV->Start)->isNullValue()) { |
| std::string Name; // Create a offset by the start value... |
| if (IV->Phi->hasName()) Name = IV->Phi->getName()+"-offset"; |
| |
| // If the types are not compatible, insert a cast now... |
| if (Val->getType() != IV->Start->getType()) |
| Val = InsertCast(Val, IV->Start->getType(), |
| Header->begin()+InsertPos++); |
| |
| Val = BinaryOperator::create(Instruction::Add, Val, IV->Start, Name); |
| // Insert the phi node at the end of the other phi nodes... |
| Header->getInstList().insert(Header->begin()+InsertPos++, Val); |
| } |
| |
| // 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(), |
| Header->begin()+InsertPos++); |
| |
| // 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().remove(IV->Phi); |
| delete IV->Phi; |
| InsertPos--; // Deleted an instr, decrement insert position |
| Changed = true; |
| } |
| } |
| |
| return Changed; |
| } |
| |
| static bool doit(Function *M, LoopInfo &Loops) { |
| // Induction Variables live in the header nodes of the loops of the function |
| return reduce_apply_bool(Loops.getTopLevelLoops().begin(), |
| Loops.getTopLevelLoops().end(), |
| std::bind1st(std::ptr_fun(TransformLoop), &Loops)); |
| } |
| |
| |
| namespace { |
| struct InductionVariableSimplify : public FunctionPass { |
| virtual bool runOnFunction(Function *F) { |
| return doit(F, getAnalysis<LoopInfo>()); |
| } |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired(LoopInfo::ID); |
| } |
| }; |
| } |
| |
| Pass *createIndVarSimplifyPass() { |
| return new InductionVariableSimplify(); |
| } |
| |