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creation functions in their public header file, unless they can help it. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1816 91177308-0d34-0410-b5e6-96231b3b80d8
216 lines
8.1 KiB
C++
216 lines
8.1 KiB
C++
//===- IndVarSimplify.cpp - Induction Variable Elimination ----------------===//
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//
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// InductionVariableSimplify - Transform induction variables in a program
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// to all use a single cannonical induction variable per loop.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar/IndVarSimplify.h"
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#include "llvm/Analysis/InductionVariable.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/iPHINode.h"
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#include "llvm/iOther.h"
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#include "llvm/Type.h"
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#include "llvm/BasicBlock.h"
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#include "llvm/ConstantVals.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/CFG.h"
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#include "Support/STLExtras.h"
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#if 0
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#define DEBUG
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#include "llvm/Analysis/Writer.h"
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#endif
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// InsertCast - Cast Val to Ty, setting a useful name on the cast if Val has a
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// name...
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//
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static Instruction *InsertCast(Instruction *Val, const Type *Ty,
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BasicBlock::iterator It) {
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Instruction *Cast = new CastInst(Val, Ty);
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if (Val->hasName()) Cast->setName(Val->getName()+"-casted");
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Val->getParent()->getInstList().insert(It, Cast);
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return Cast;
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}
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static bool TransformLoop(cfg::LoopInfo *Loops, cfg::Loop *Loop) {
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// Transform all subloops before this loop...
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bool Changed = reduce_apply_bool(Loop->getSubLoops().begin(),
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Loop->getSubLoops().end(),
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std::bind1st(std::ptr_fun(TransformLoop), Loops));
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// Get the header node for this loop. All of the phi nodes that could be
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// induction variables must live in this basic block.
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BasicBlock *Header = (BasicBlock*)Loop->getBlocks().front();
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// Loop over all of the PHI nodes in the basic block, calculating the
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// induction variables that they represent... stuffing the induction variable
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// info into a vector...
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//
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std::vector<InductionVariable> IndVars; // Induction variables for block
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for (BasicBlock::iterator I = Header->begin();
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PHINode *PN = dyn_cast<PHINode>(*I); ++I)
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IndVars.push_back(InductionVariable(PN, Loops));
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// If there are no phi nodes in this basic block, there can't be indvars...
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if (IndVars.empty()) return Changed;
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// Loop over the induction variables, looking for a cannonical induction
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// variable, and checking to make sure they are not all unknown induction
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// variables.
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//
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bool FoundIndVars = false;
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InductionVariable *Cannonical = 0;
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for (unsigned i = 0; i < IndVars.size(); ++i) {
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if (IndVars[i].InductionType == InductionVariable::Cannonical)
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Cannonical = &IndVars[i];
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if (IndVars[i].InductionType != InductionVariable::Unknown)
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FoundIndVars = true;
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}
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// No induction variables, bail early... don't add a cannonnical indvar
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if (!FoundIndVars) return Changed;
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// Okay, we want to convert other induction variables to use a cannonical
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// indvar. If we don't have one, add one now...
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if (!Cannonical) {
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// Create the PHI node for the new induction variable
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PHINode *PN = new PHINode(Type::UIntTy, "cann-indvar");
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// Insert the phi node at the end of the other phi nodes...
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Header->getInstList().insert(Header->begin()+IndVars.size(), PN);
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// Create the increment instruction to add one to the counter...
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Instruction *Add = BinaryOperator::create(Instruction::Add, PN,
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ConstantUInt::get(Type::UIntTy,1),
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"add1-indvar");
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// Insert the add instruction after all of the PHI nodes...
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Header->getInstList().insert(Header->begin()+(IndVars.size()+1), Add);
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// Figure out which block is incoming and which is the backedge for the loop
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BasicBlock *Incoming, *BackEdgeBlock;
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pred_iterator PI = pred_begin(Header);
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assert(PI != pred_end(Header) && "Loop headers should have 2 preds!");
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if (Loop->contains(*PI)) { // First pred is back edge...
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BackEdgeBlock = *PI++;
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Incoming = *PI++;
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} else {
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Incoming = *PI++;
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BackEdgeBlock = *PI++;
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}
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assert(PI == pred_end(Header) && "Loop headers should have 2 preds!");
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// Add incoming values for the PHI node...
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PN->addIncoming(Constant::getNullConstant(Type::UIntTy), Incoming);
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PN->addIncoming(Add, BackEdgeBlock);
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// Analyze the new induction variable...
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IndVars.push_back(InductionVariable(PN, Loops));
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assert(IndVars.back().InductionType == InductionVariable::Cannonical &&
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"Just inserted cannonical indvar that is not cannonical!");
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Cannonical = &IndVars.back();
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Changed = true;
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}
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#ifdef DEBUG
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cerr << "Induction variables:\n";
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#endif
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// Get the current loop iteration count, which is always the value of the
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// cannonical phi node...
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//
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PHINode *IterCount = Cannonical->Phi;
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// Loop through and replace all of the auxillary induction variables with
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// references to the primary induction variable...
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//
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unsigned InsertPos = IndVars.size();
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for (unsigned i = 0; i < IndVars.size(); ++i) {
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InductionVariable *IV = &IndVars[i];
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#ifdef DEBUG
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cerr << IndVars[i];
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#endif
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// Don't modify the cannonical indvar or unrecognized indvars...
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if (IV != Cannonical && IV->InductionType != InductionVariable::Unknown) {
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Instruction *Val = IterCount;
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if (!isa<ConstantInt>(IV->Step) || // If the step != 1
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!cast<ConstantInt>(IV->Step)->equalsInt(1)) {
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std::string Name; // Create a scale by the step value...
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if (IV->Phi->hasName()) Name = IV->Phi->getName()+"-scale";
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// If the types are not compatible, insert a cast now...
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if (Val->getType() != IV->Step->getType())
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Val = InsertCast(Val, IV->Step->getType(),
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Header->begin()+InsertPos++);
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Val = BinaryOperator::create(Instruction::Mul, Val, IV->Step, Name);
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// Insert the phi node at the end of the other phi nodes...
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Header->getInstList().insert(Header->begin()+InsertPos++, Val);
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}
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if (!isa<Constant>(IV->Start) || // If the start != 0
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!cast<Constant>(IV->Start)->isNullValue()) {
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std::string Name; // Create a offset by the start value...
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if (IV->Phi->hasName()) Name = IV->Phi->getName()+"-offset";
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// If the types are not compatible, insert a cast now...
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if (Val->getType() != IV->Start->getType())
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Val = InsertCast(Val, IV->Start->getType(),
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Header->begin()+InsertPos++);
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Val = BinaryOperator::create(Instruction::Add, Val, IV->Start, Name);
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// Insert the phi node at the end of the other phi nodes...
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Header->getInstList().insert(Header->begin()+InsertPos++, Val);
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}
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// If the PHI node has a different type than val is, insert a cast now...
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if (Val->getType() != IV->Phi->getType())
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Val = InsertCast(Val, IV->Phi->getType(),
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Header->begin()+InsertPos++);
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// Replace all uses of the old PHI node with the new computed value...
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IV->Phi->replaceAllUsesWith(Val);
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// Move the PHI name to it's new equivalent value...
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std::string OldName = IV->Phi->getName();
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IV->Phi->setName("");
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Val->setName(OldName);
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// Delete the old, now unused, phi node...
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Header->getInstList().remove(IV->Phi);
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delete IV->Phi;
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InsertPos--; // Deleted an instr, decrement insert position
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Changed = true;
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}
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}
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return Changed;
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}
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static bool doit(Method *M, cfg::LoopInfo &Loops) {
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// Induction Variables live in the header nodes of the loops of the method...
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return reduce_apply_bool(Loops.getTopLevelLoops().begin(),
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Loops.getTopLevelLoops().end(),
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std::bind1st(std::ptr_fun(TransformLoop), &Loops));
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}
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namespace {
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struct InductionVariableSimplify : public MethodPass {
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virtual bool runOnMethod(Method *M) {
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return doit(M, getAnalysis<cfg::LoopInfo>());
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}
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virtual void getAnalysisUsageInfo(Pass::AnalysisSet &Required,
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Pass::AnalysisSet &Destroyed,
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Pass::AnalysisSet &Provided) {
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Required.push_back(cfg::LoopInfo::ID);
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}
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};
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}
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Pass *createIndVarSimplifyPass() {
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return new InductionVariableSimplify();
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}
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