diff options
| -rw-r--r-- | lib/Transforms/Scalar/IndVarSimplify.cpp | 644 |
1 files changed, 346 insertions, 298 deletions
diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp index f631b69f0a..0622b170c8 100644 --- a/lib/Transforms/Scalar/IndVarSimplify.cpp +++ b/lib/Transforms/Scalar/IndVarSimplify.cpp @@ -7,65 +7,88 @@ // //===----------------------------------------------------------------------===// // -// 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. +// This transformation analyzes and transforms the induction variables (and +// computations derived from them) into simpler forms suitable for subsequent +// analysis and transformation. +// +// This transformation make the following changes to each loop with an +// identifiable induction variable: +// 1. All loops are transformed to have a SINGLE canonical induction variable +// which starts at zero and steps by one. +// 2. The canonical induction variable is guaranteed to be the first PHI node +// in the loop header block. +// 3. Any pointer arithmetic recurrences are raised to use array subscripts. +// +// If the trip count of a loop is computable, this pass also makes the following +// changes: +// 1. The exit condition for the loop is canonicalized to compare the +// induction value against the exit value. This turns loops like: +// 'for (i = 7; i*i < 1000; ++i)' into 'for (i = 0; i != 25; ++i)' +// 2. Any use outside of the loop of an expression derived from the indvar +// is changed to compute the derived value outside of the loop, eliminating +// the dependence on the exit value of the induction variable. If the only +// purpose of the loop is to compute the exit value of some derived +// expression, this transformation will make the loop dead. +// +// This transformation should be followed by strength reduction after all of the +// desired loop transformations have been performed. Additionally, on targets +// where it is profitable, the loop could be transformed to count down to zero +// (the "do loop" optimization). // //===----------------------------------------------------------------------===// -#define DEBUG_TYPE "indvar" #include "llvm/Transforms/Scalar.h" -#include "llvm/Constants.h" -#include "llvm/Type.h" +#include "llvm/BasicBlock.h" +#include "llvm/Constant.h" #include "llvm/Instructions.h" -#include "llvm/Analysis/InductionVariable.h" +#include "llvm/Type.h" +#include "llvm/Analysis/ScalarEvolution.h" #include "llvm/Analysis/LoopInfo.h" #include "llvm/Support/CFG.h" -#include "llvm/Target/TargetData.h" #include "llvm/Transforms/Utils/Local.h" -#include "Support/Debug.h" +#include "Support/CommandLine.h" #include "Support/Statistic.h" using namespace llvm; namespace { Statistic<> NumRemoved ("indvars", "Number of aux indvars removed"); + Statistic<> NumPointer ("indvars", "Number of pointer indvars promoted"); Statistic<> NumInserted("indvars", "Number of canonical indvars added"); + Statistic<> NumReplaced("indvars", "Number of exit values replaced"); + Statistic<> NumLFTR ("indvars", "Number of loop exit tests replaced"); class IndVarSimplify : public FunctionPass { - LoopInfo *Loops; - TargetData *TD; + LoopInfo *LI; + ScalarEvolution *SE; bool Changed; public: virtual bool runOnFunction(Function &) { - Loops = &getAnalysis<LoopInfo>(); - TD = &getAnalysis<TargetData>(); + LI = &getAnalysis<LoopInfo>(); + SE = &getAnalysis<ScalarEvolution>(); Changed = false; // Induction Variables live in the header nodes of loops - for (LoopInfo::iterator I = Loops->begin(), E = Loops->end(); I != E; ++I) + for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I) runOnLoop(*I); return Changed; } - unsigned getTypeSize(const Type *Ty) { - if (unsigned Size = Ty->getPrimitiveSize()) - return Size; - return TD->getTypeSize(Ty); // Must be a pointer - } - - Value *ComputeAuxIndVarValue(InductionVariable &IV, Value *CIV); - void ReplaceIndVar(InductionVariable &IV, Value *Counter); - - void runOnLoop(Loop *L); - virtual void getAnalysisUsage(AnalysisUsage &AU) const { - AU.addRequired<TargetData>(); // Need pointer size - AU.addRequired<LoopInfo>(); AU.addRequiredID(LoopSimplifyID); + AU.addRequired<ScalarEvolution>(); + AU.addRequired<LoopInfo>(); AU.addPreservedID(LoopSimplifyID); AU.setPreservesCFG(); } + private: + void runOnLoop(Loop *L); + void EliminatePointerRecurrence(PHINode *PN, BasicBlock *Preheader, + std::set<Instruction*> &DeadInsts); + void LinearFunctionTestReplace(Loop *L, SCEV *IterationCount, + Value *IndVar, ScalarEvolutionRewriter &RW); + void RewriteLoopExitValues(Loop *L); + + void DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts); }; RegisterOpt<IndVarSimplify> X("indvars", "Canonicalize Induction Variables"); } @@ -75,298 +98,323 @@ Pass *llvm::createIndVarSimplifyPass() { } -void IndVarSimplify::runOnLoop(Loop *Loop) { - // Transform all subloops before this loop... - for (LoopInfo::iterator I = Loop->begin(), E = Loop->end(); I != E; ++I) - runOnLoop(*I); +/// DeleteTriviallyDeadInstructions - If any of the instructions is the +/// specified set are trivially dead, delete them and see if this makes any of +/// their operands subsequently dead. +void IndVarSimplify:: +DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts) { + while (!Insts.empty()) { + Instruction *I = *Insts.begin(); + Insts.erase(Insts.begin()); + if (isInstructionTriviallyDead(I)) { + for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) + if (Instruction *U = dyn_cast<Instruction>(I->getOperand(i))) + Insts.insert(U); + SE->deleteInstructionFromRecords(I); + I->getParent()->getInstList().erase(I); + Changed = true; + } + } +} - // 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; - - // Loop over the induction variables, looking for a canonical induction - // variable, and checking to make sure they are not all unknown induction - // variables. Keep track of the largest integer size of the induction - // variable. - // - InductionVariable *Canonical = 0; - unsigned MaxSize = 0; +/// EliminatePointerRecurrence - Check to see if this is a trivial GEP pointer +/// recurrence. If so, change it into an integer recurrence, permitting +/// analysis by the SCEV routines. +void IndVarSimplify::EliminatePointerRecurrence(PHINode *PN, + BasicBlock *Preheader, + std::set<Instruction*> &DeadInsts) { + assert(PN->getNumIncomingValues() == 2 && "Noncanonicalized loop!"); + unsigned PreheaderIdx = PN->getBasicBlockIndex(Preheader); + unsigned BackedgeIdx = PreheaderIdx^1; + if (GetElementPtrInst *GEPI = + dyn_cast<GetElementPtrInst>(PN->getIncomingValue(BackedgeIdx))) + if (GEPI->getOperand(0) == PN) { + assert(GEPI->getNumOperands() == 2 && "GEP types must mismatch!"); + + // Okay, we found a pointer recurrence. Transform this pointer + // recurrence into an integer recurrence. Compute the value that gets + // added to the pointer at every iteration. + Value *AddedVal = GEPI->getOperand(1); + + // Insert a new integer PHI node into the top of the block. + PHINode *NewPhi = new PHINode(AddedVal->getType(), + PN->getName()+".rec", PN); + NewPhi->addIncoming(Constant::getNullValue(NewPhi->getType()), + Preheader); + // Create the new add instruction. + Value *NewAdd = BinaryOperator::create(Instruction::Add, NewPhi, + AddedVal, + GEPI->getName()+".rec", GEPI); + NewPhi->addIncoming(NewAdd, PN->getIncomingBlock(BackedgeIdx)); + + // Update the existing GEP to use the recurrence. + GEPI->setOperand(0, PN->getIncomingValue(PreheaderIdx)); + + // Update the GEP to use the new recurrence we just inserted. + GEPI->setOperand(1, NewAdd); + + // Finally, if there are any other users of the PHI node, we must + // insert a new GEP instruction that uses the pre-incremented version + // of the induction amount. + if (!PN->use_empty()) { + BasicBlock::iterator InsertPos = PN; ++InsertPos; + while (isa<PHINode>(InsertPos)) ++InsertPos; + std::string Name = PN->getName(); PN->setName(""); + Value *PreInc = + new GetElementPtrInst(PN->getIncomingValue(PreheaderIdx), + std::vector<Value*>(1, NewPhi), Name, + InsertPos); + PN->replaceAllUsesWith(PreInc); + } + + // Delete the old PHI for sure, and the GEP if its otherwise unused. + DeadInsts.insert(PN); - for (unsigned i = 0; i != IndVars.size(); ++i) { - InductionVariable &IV = IndVars[i]; + ++NumPointer; + Changed = true; + } +} - if (IV.InductionType != InductionVariable::Unknown) { - unsigned IVSize = getTypeSize(IV.Phi->getType()); +/// LinearFunctionTestReplace - This method rewrites the exit condition of the +/// loop to be a canonical != comparison against the loop induction variable. +/// This pass is able to rewrite the exit tests of any loop where the SCEV +/// analysis can determine the trip count of the loop, which is actually a much +/// broader range than just linear tests. +void IndVarSimplify::LinearFunctionTestReplace(Loop *L, SCEV *IterationCount, + Value *IndVar, + ScalarEvolutionRewriter &RW) { + // Find the exit block for the loop. We can currently only handle loops with + // a single exit. + if (L->getExitBlocks().size() != 1) return; + BasicBlock *ExitBlock = L->getExitBlocks()[0]; + + // Make sure there is only one predecessor block in the loop. + BasicBlock *ExitingBlock = 0; + for (pred_iterator PI = pred_begin(ExitBlock), PE = pred_end(ExitBlock); + PI != PE; ++PI) + if (L->contains(*PI)) { + if (ExitingBlock == 0) + ExitingBlock = *PI; + else + return; // Multiple exits from loop to this block. + } + assert(ExitingBlock && "Loop info is broken"); + + if (!isa<BranchInst>(ExitingBlock->getTerminator())) + return; // Can't rewrite non-branch yet + BranchInst *BI = cast<BranchInst>(ExitingBlock->getTerminator()); + assert(BI->isConditional() && "Must be conditional to be part of loop!"); + + std::set<Instruction*> InstructionsToDelete; + if (Instruction *Cond = dyn_cast<Instruction>(BI->getCondition())) + InstructionsToDelete.insert(Cond); + + // Expand the code for the iteration count into the preheader of the loop. + BasicBlock *Preheader = L->getLoopPreheader(); + Value *ExitCnt = RW.ExpandCodeFor(IterationCount, Preheader->getTerminator(), + IndVar->getType()); + + // Insert a new setne or seteq instruction before the branch. + Instruction::BinaryOps Opcode; + if (L->contains(BI->getSuccessor(0))) + Opcode = Instruction::SetNE; + else + Opcode = Instruction::SetEQ; + + Value *Cond = new SetCondInst(Opcode, IndVar, ExitCnt, "exitcond", BI); + BI->setCondition(Cond); + ++NumLFTR; + Changed = true; + + DeleteTriviallyDeadInstructions(InstructionsToDelete); +} - if (IV.InductionType == InductionVariable::Canonical && - !isa<PointerType>(IV.Phi->getType()) && IVSize >= MaxSize) - Canonical = &IV; - - if (IVSize > MaxSize) MaxSize = IVSize; - // If this variable is larger than the currently identified canonical - // indvar, the canonical indvar is not usable. - if (Canonical && IVSize > getTypeSize(Canonical->Phi->getType())) - Canonical = 0; +/// RewriteLoopExitValues - Check to see if this loop has a computable +/// loop-invariant execution count. If so, this means that we can compute the +/// final value of any expressions that are recurrent in the loop, and +/// substitute the exit values from the loop into any instructions outside of +/// the loop that use the final values of the current expressions. +void IndVarSimplify::RewriteLoopExitValues(Loop *L) { + BasicBlock *Preheader = L->getLoopPreheader(); + + // Scan all of the instructions in the loop, looking at those that have + // extra-loop users and which are recurrences. + ScalarEvolutionRewriter Rewriter(*SE, *LI); + + // We insert the code into the preheader of the loop if the loop contains + // multiple exit blocks, or in the exit block if there is exactly one. + BasicBlock *BlockToInsertInto; + if (L->getExitBlocks().size() == 1) + BlockToInsertInto = L->getExitBlocks()[0]; + else + BlockToInsertInto = Preheader; + BasicBlock::iterator InsertPt = BlockToInsertInto->begin(); + while (isa<PHINode>(InsertPt)) ++InsertPt; + + std::set<Instruction*> InstructionsToDelete; + + for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i) + if (LI->getLoopFor(L->getBlocks()[i]) == L) { // Not in a subloop... + BasicBlock *BB = L->getBlocks()[i]; + for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) + if (I->getType()->isInteger()) { // Is an integer instruction + SCEVHandle SH = SE->getSCEV(I); + if (SH->hasComputableLoopEvolution(L)) { // Varies predictably + // Find out if this predictably varying value is actually used + // outside of the loop. "extra" as opposed to "intra". + std::vector<User*> ExtraLoopUsers; + for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); + UI != E; ++UI) + if (!L->contains(cast<Instruction>(*UI)->getParent())) + ExtraLoopUsers.push_back(*UI); + if (!ExtraLoopUsers.empty()) { + // Okay, this instruction has a user outside of the current loop + // and varies predictably in this loop. Evaluate the value it + // contains when the loop exits, and insert code for it. + SCEVHandle ExitValue = SE->getSCEVAtScope(I,L->getParentLoop()); + if (!isa<SCEVCouldNotCompute>(ExitValue)) { + Changed = true; + ++NumReplaced; + Value *NewVal = Rewriter.ExpandCodeFor(ExitValue, InsertPt, + I->getType()); + + // Rewrite any users of the computed value outside of the loop + // with the newly computed value. + for (unsigned i = 0, e = ExtraLoopUsers.size(); i != e; ++i) + ExtraLoopUsers[i]->replaceUsesOfWith(I, NewVal); + + // If this instruction is dead now, schedule it to be removed. + if (I->use_empty()) + InstructionsToDelete.insert(I); + } + } + } + } } - } - // No induction variables, bail early... don't add a canonical indvar - if (MaxSize == 0) return; + DeleteTriviallyDeadInstructions(InstructionsToDelete); +} - // Figure out what the exit condition of the loop is. We can currently only - // handle loops with a single exit. If we cannot figure out what the - // termination condition is, we leave this variable set to null. +void IndVarSimplify::runOnLoop(Loop *L) { + // First step. Check to see if there are any trivial GEP pointer recurrences. + // If there are, change them into integer recurrences, permitting analysis by + // the SCEV routines. // - SetCondInst *TermCond = 0; - if (Loop->getExitBlocks().size() == 1) { - // Get ExitingBlock - the basic block in the loop which contains the branch - // out of the loop. - BasicBlock *Exit = Loop->getExitBlocks()[0]; - pred_iterator PI = pred_begin(Exit); - assert(PI != pred_end(Exit) && "Should have one predecessor in loop!"); - BasicBlock *ExitingBlock = *PI; - assert(++PI == pred_end(Exit) && "Exit block should have one pred!"); - assert(Loop->isLoopExit(ExitingBlock) && "Exiting block is not loop exit!"); - - // Since the block is in the loop, yet branches out of it, we know that the - // block must end with multiple destination terminator. Which means it is - // either a conditional branch, a switch instruction, or an invoke. - if (BranchInst *BI = dyn_cast<BranchInst>(ExitingBlock->getTerminator())) { - assert(BI->isConditional() && "Unconditional branch has multiple succs?"); - TermCond = dyn_cast<SetCondInst>(BI->getCondition()); - } else { - // NOTE: if people actually exit loops with switch instructions, we could - // handle them, but I don't think this is important enough to spend time - // thinking about. - assert(isa<SwitchInst>(ExitingBlock->getTerminator()) || - isa<InvokeInst>(ExitingBlock->getTerminator()) && - "Unknown multi-successor terminator!"); - } - } + BasicBlock *Header = L->getHeader(); + BasicBlock *Preheader = L->getLoopPreheader(); + + std::set<Instruction*> DeadInsts; + for (BasicBlock::iterator I = Header->begin(); + PHINode *PN = dyn_cast<PHINode>(I); ++I) + if (isa<PointerType>(PN->getType())) + EliminatePointerRecurrence(PN, Preheader, DeadInsts); - if (TermCond) - DEBUG(std::cerr << "INDVAR: Found termination condition: " << *TermCond); - - // 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... - const Type *IVType; - switch (MaxSize) { - default: assert(0 && "Unknown integer type size!"); - case 1: IVType = Type::UByteTy; break; - case 2: IVType = Type::UShortTy; break; - case 4: IVType = Type::UIntTy; break; - case 8: IVType = Type::ULongTy; break; - } - - PHINode *PN = new PHINode(IVType, "cann-indvar", Header->begin()); - - // Create the increment instruction to add one to the counter... - Instruction *Add = BinaryOperator::create(Instruction::Add, PN, - ConstantUInt::get(IVType, 1), - "next-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(IVType), 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; - DEBUG(std::cerr << "INDVAR: Inserted canonical iv: " << *PN); - } 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 << "IndVar: Existing canonical iv used: " - << *Canonical->Phi); - } + if (!DeadInsts.empty()) + DeleteTriviallyDeadInstructions(DeadInsts); - DEBUG(std::cerr << "INDVAR: Replacing Induction variables:\n"); - // Get the current loop iteration count, which is always the value of the - // canonical phi node... - // - PHINode *IterCount = Canonical->Phi; + // Next, transform all loops nesting inside of this loop. + for (LoopInfo::iterator I = L->begin(), E = L->end(); I != E; ++I) + runOnLoop(*I); - // Loop through and replace all of the auxiliary induction variables with - // references to the canonical induction variable... + // Check to see if this loop has a computable loop-invariant execution count. + // If so, this means that we can compute the final value of any expressions + // that are recurrent in the loop, and substitute the exit values from the + // loop into any instructions outside of the loop that use the final values of + // the current expressions. // - for (unsigned i = 0; i != IndVars.size(); ++i) { - InductionVariable *IV = &IndVars[i]; + SCEVHandle IterationCount = SE->getIterationCount(L); + if (!isa<SCEVCouldNotCompute>(IterationCount)) + RewriteLoopExitValues(L); + + // Next, analyze all of the induction variables in the loop, canonicalizing + // auxillary induction variables. + std::vector<std::pair<PHINode*, SCEVHandle> > IndVars; + + for (BasicBlock::iterator I = Header->begin(); + PHINode *PN = dyn_cast<PHINode>(I); ++I) + if (PN->getType()->isInteger()) { // FIXME: when we have fast-math, enable! + SCEVHandle SCEV = SE->getSCEV(PN); + if (SCEV->hasComputableLoopEvolution(L)) + if (SE->shouldSubstituteIndVar(SCEV)) // HACK! + IndVars.push_back(std::make_pair(PN, SCEV)); + } - DEBUG(IV->print(std::cerr)); + // If there are no induction variables in the loop, there is nothing more to + // do. + if (IndVars.empty()) return; - // Don't modify the canonical indvar or unrecognized indvars... - if (IV != Canonical && IV->InductionType != InductionVariable::Unknown) { - ReplaceIndVar(*IV, IterCount); - Changed = true; - ++NumRemoved; - } + // Compute the type of the largest recurrence expression. + // + const Type *LargestType = IndVars[0].first->getType(); + bool DifferingSizes = false; + for (unsigned i = 1, e = IndVars.size(); i != e; ++i) { + const Type *Ty = IndVars[i].first->getType(); + DifferingSizes |= Ty->getPrimitiveSize() != LargestType->getPrimitiveSize(); + if (Ty->getPrimitiveSize() > LargestType->getPrimitiveSize()) + LargestType = Ty; } -} -/// ComputeAuxIndVarValue - Given an auxillary induction variable, compute and -/// return a value which will always be equal to the induction variable PHI, but -/// is based off of the canonical induction variable CIV. -/// -Value *IndVarSimplify::ComputeAuxIndVarValue(InductionVariable &IV, Value *CIV){ - Instruction *Phi = IV.Phi; - const Type *IVTy = Phi->getType(); - if (isa<PointerType>(IVTy)) // If indexing into a pointer, make the - IVTy = TD->getIntPtrType(); // index the appropriate type. - - BasicBlock::iterator AfterPHIIt = Phi; - while (isa<PHINode>(AfterPHIIt)) ++AfterPHIIt; - - Value *Val = CIV; - if (Val->getType() != IVTy) - Val = new CastInst(Val, IVTy, Val->getName(), AfterPHIIt); - - 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 (IV.Step->getType() != IVTy) - IV.Step = new CastInst(IV.Step, IVTy, IV.Step->getName(), AfterPHIIt); - - Val = BinaryOperator::create(Instruction::Mul, Val, IV.Step, - Phi->getName()+"-scale", AfterPHIIt); - } - - // If this is a pointer indvar... - if (isa<PointerType>(Phi->getType())) { - std::vector<Value*> Idx; - // FIXME: this should not be needed when we fix PR82! - if (Val->getType() != Type::LongTy) - Val = new CastInst(Val, Type::LongTy, Val->getName(), AfterPHIIt); - Idx.push_back(Val); - Val = new GetElementPtrInst(IV.Start, Idx, - Phi->getName()+"-offset", - AfterPHIIt); - - } else if (!isa<Constant>(IV.Start) || // If Start != 0... - !cast<Constant>(IV.Start)->isNullValue()) { - // If the types are not compatible, insert a cast now... - if (IV.Start->getType() != IVTy) - IV.Start = new CastInst(IV.Start, IVTy, IV.Start->getName(), - AfterPHIIt); - - // Insert the instruction after the phi nodes... - Val = BinaryOperator::create(Instruction::Add, Val, IV.Start, - Phi->getName()+"-offset", AfterPHIIt); + // Create a rewriter object which we'll use to transform the code with. + ScalarEvolutionRewriter Rewriter(*SE, *LI); + + // Now that we know the largest of of the induction variables in this loop, + // insert a canonical induction variable of the largest size. + Value *IndVar = Rewriter.GetOrInsertCanonicalInductionVariable(L,LargestType); + ++NumInserted; + Changed = true; + + if (!isa<SCEVCouldNotCompute>(IterationCount)) + LinearFunctionTestReplace(L, IterationCount, IndVar, Rewriter); + +#if 0 + // If there were induction variables of other sizes, cast the primary + // induction variable to the right size for them, avoiding the need for the + // code evaluation methods to insert induction variables of different sizes. + // FIXME! + if (DifferingSizes) { + std::map<unsigned, Value*> InsertedSizes; + for (unsigned i = 0, e = IndVars.size(); i != e; ++i) { + } } - - // If the PHI node has a different type than val is, insert a cast now... - if (Val->getType() != Phi->getType()) - Val = new CastInst(Val, Phi->getType(), Val->getName(), AfterPHIIt); - - // Move the PHI name to it's new equivalent value... - std::string OldName = Phi->getName(); - Phi->setName(""); - Val->setName(OldName); - - return Val; -} - -// ReplaceIndVar - Replace all uses of the specified induction variable with -// expressions computed from the specified loop iteration counter variable. -// Return true if instructions were deleted. -void IndVarSimplify::ReplaceIndVar(InductionVariable &IV, Value *CIV) { - Value *IndVarVal = 0; - PHINode *Phi = IV.Phi; - - assert(Phi->getNumOperands() == 4 && - "Only expect induction variables in canonical loops!"); - - // Remember the incoming values used by the PHI node - std::vector<Value*> PHIOps; - PHIOps.reserve(2); - PHIOps.push_back(Phi->getIncomingValue(0)); - PHIOps.push_back(Phi->getIncomingValue(1)); - - // Delete all of the operands of the PHI node... so that the to-be-deleted PHI - // node does not cause any expressions to be computed that would not otherwise - // be. - Phi->dropAllReferences(); - - // Now that we are rid of unneeded uses of the PHI node, replace any remaining - // ones with the appropriate code using the canonical induction variable. - while (!Phi->use_empty()) { - Instruction *U = cast<Instruction>(Phi->use_back()); - - // TODO: Perform LFTR here if possible - if (0) { - - } else { - // Replace all uses of the old PHI node with the new computed value... - if (IndVarVal == 0) - IndVarVal = ComputeAuxIndVarValue(IV, CIV); - U->replaceUsesOfWith(Phi, IndVarVal); - } +#endif + + // Now that we have a canonical induction variable, we can rewrite any + // recurrences in terms of the induction variable. Start with the auxillary + // induction variables, and recursively rewrite any of their uses. + BasicBlock::iterator InsertPt = Header->begin(); + while (isa<PHINode>(InsertPt)) ++InsertPt; + + while (!IndVars.empty()) { + PHINode *PN = IndVars.back().first; + Value *NewVal = Rewriter.ExpandCodeFor(IndVars.back().second, InsertPt, + PN->getType()); + // Replace the old PHI Node with the inserted computation. + PN->replaceAllUsesWith(NewVal); + DeadInsts.insert(PN); + IndVars.pop_back(); + ++NumRemoved; + Changed = true; } - // If the PHI is the last user of any instructions for computing PHI nodes - // that are irrelevant now, delete those instructions. - while (!PHIOps.empty()) { - Instruction *MaybeDead = dyn_cast<Instruction>(PHIOps.back()); - PHIOps.pop_back(); - - if (MaybeDead && isInstructionTriviallyDead(MaybeDead) && - (!isa<PHINode>(MaybeDead) || - MaybeDead->getParent() != Phi->getParent())) { - PHIOps.insert(PHIOps.end(), MaybeDead->op_begin(), - MaybeDead->op_end()); - MaybeDead->getParent()->getInstList().erase(MaybeDead); - - // Erase any duplicates entries in the PHIOps list. - std::vector<Value*>::iterator It = - std::find(PHIOps.begin(), PHIOps.end(), MaybeDead); - while (It != PHIOps.end()) { - PHIOps.erase(It); - It = std::find(PHIOps.begin(), PHIOps.end(), MaybeDead); - } + DeleteTriviallyDeadInstructions(DeadInsts); + + // TODO: In the future we could replace all instructions in the loop body with + // simpler expressions. It's not clear how useful this would be though or if + // the code expansion cost would be worth it! We probably shouldn't do this + // until we have a way to reuse expressions already in the code. +#if 0 + for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i) + if (LI->getLoopFor(L->getBlocks()[i]) == L) { // Not in a subloop... + BasicBlock *BB = L->getBlocks()[i]; + for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) + if (I->getType()->isInteger() && // Is an integer instruction + !Rewriter.isInsertedInstruction(I)) { + SCEVHandle SH = SE->getSCEV(I); + } } - } - - // Delete the old, now unused, phi node... - Phi->getParent()->getInstList().erase(Phi); +#endif } - |