1 //===- IndVarSimplify.cpp - Induction Variable Elimination ----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This transformation analyzes and transforms the induction variables (and
11 // computations derived from them) into simpler forms suitable for subsequent
12 // analysis and transformation.
14 // This transformation make the following changes to each loop with an
15 // identifiable induction variable:
16 // 1. All loops are transformed to have a SINGLE canonical induction variable
17 // which starts at zero and steps by one.
18 // 2. The canonical induction variable is guaranteed to be the first PHI node
19 // in the loop header block.
20 // 3. Any pointer arithmetic recurrences are raised to use array subscripts.
22 // If the trip count of a loop is computable, this pass also makes the following
24 // 1. The exit condition for the loop is canonicalized to compare the
25 // induction value against the exit value. This turns loops like:
26 // 'for (i = 7; i*i < 1000; ++i)' into 'for (i = 0; i != 25; ++i)'
27 // 2. Any use outside of the loop of an expression derived from the indvar
28 // is changed to compute the derived value outside of the loop, eliminating
29 // the dependence on the exit value of the induction variable. If the only
30 // purpose of the loop is to compute the exit value of some derived
31 // expression, this transformation will make the loop dead.
33 // This transformation should be followed by strength reduction after all of the
34 // desired loop transformations have been performed. Additionally, on targets
35 // where it is profitable, the loop could be transformed to count down to zero
36 // (the "do loop" optimization).
38 //===----------------------------------------------------------------------===//
40 #include "llvm/Transforms/Scalar.h"
41 #include "llvm/BasicBlock.h"
42 #include "llvm/Constants.h"
43 #include "llvm/Instructions.h"
44 #include "llvm/Type.h"
45 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
46 #include "llvm/Analysis/LoopInfo.h"
47 #include "llvm/Support/CFG.h"
48 #include "llvm/Transforms/Utils/Local.h"
49 #include "Support/CommandLine.h"
50 #include "Support/Statistic.h"
54 /// SCEVExpander - This class uses information about analyze scalars to
55 /// rewrite expressions in canonical form.
57 /// Clients should create an instance of this class when rewriting is needed,
58 /// and destroying it when finished to allow the release of the associated
60 struct SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
63 std::map<SCEVHandle, Value*> InsertedExpressions;
64 std::set<Instruction*> InsertedInstructions;
66 Instruction *InsertPt;
68 friend class SCEVVisitor<SCEVExpander, Value*>;
70 SCEVExpander(ScalarEvolution &se, LoopInfo &li) : SE(se), LI(li) {}
72 /// isInsertedInstruction - Return true if the specified instruction was
73 /// inserted by the code rewriter. If so, the client should not modify the
75 bool isInsertedInstruction(Instruction *I) const {
76 return InsertedInstructions.count(I);
79 /// getOrInsertCanonicalInductionVariable - This method returns the
80 /// canonical induction variable of the specified type for the specified
81 /// loop (inserting one if there is none). A canonical induction variable
82 /// starts at zero and steps by one on each iteration.
83 Value *getOrInsertCanonicalInductionVariable(const Loop *L, const Type *Ty){
84 assert((Ty->isInteger() || Ty->isFloatingPoint()) &&
85 "Can only insert integer or floating point induction variables!");
86 SCEVHandle H = SCEVAddRecExpr::get(SCEVUnknown::getIntegerSCEV(0, Ty),
87 SCEVUnknown::getIntegerSCEV(1, Ty), L);
91 /// addInsertedValue - Remember the specified instruction as being the
92 /// canonical form for the specified SCEV.
93 void addInsertedValue(Instruction *I, SCEV *S) {
94 InsertedExpressions[S] = (Value*)I;
95 InsertedInstructions.insert(I);
98 /// expandCodeFor - Insert code to directly compute the specified SCEV
99 /// expression into the program. The inserted code is inserted into the
102 /// If a particular value sign is required, a type may be specified for the
104 Value *expandCodeFor(SCEVHandle SH, Instruction *IP, const Type *Ty = 0) {
105 // Expand the code for this SCEV.
107 return expandInTy(SH, Ty);
111 Value *expand(SCEV *S) {
112 // Check to see if we already expanded this.
113 std::map<SCEVHandle, Value*>::iterator I = InsertedExpressions.find(S);
114 if (I != InsertedExpressions.end())
118 InsertedExpressions[S] = V;
122 Value *expandInTy(SCEV *S, const Type *Ty) {
123 Value *V = expand(S);
124 if (Ty && V->getType() != Ty) {
125 // FIXME: keep track of the cast instruction.
126 if (Constant *C = dyn_cast<Constant>(V))
127 return ConstantExpr::getCast(C, Ty);
128 else if (Instruction *I = dyn_cast<Instruction>(V)) {
129 // Check to see if there is already a cast. If there is, use it.
130 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
132 if ((*UI)->getType() == Ty)
133 if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI))) {
134 BasicBlock::iterator It = I; ++It;
135 while (isa<PHINode>(It)) ++It;
136 if (It != BasicBlock::iterator(CI)) {
137 // Splice the cast immediately after the operand in question.
138 I->getParent()->getInstList().splice(It,
139 CI->getParent()->getInstList(),
145 BasicBlock::iterator IP = I; ++IP;
146 if (InvokeInst *II = dyn_cast<InvokeInst>(I))
147 IP = II->getNormalDest()->begin();
148 while (isa<PHINode>(IP)) ++IP;
149 return new CastInst(V, Ty, V->getName(), IP);
151 // FIXME: check to see if there is already a cast!
152 return new CastInst(V, Ty, V->getName(), InsertPt);
158 Value *visitConstant(SCEVConstant *S) {
159 return S->getValue();
162 Value *visitTruncateExpr(SCEVTruncateExpr *S) {
163 Value *V = expand(S->getOperand());
164 return new CastInst(V, S->getType(), "tmp.", InsertPt);
167 Value *visitZeroExtendExpr(SCEVZeroExtendExpr *S) {
168 Value *V = expandInTy(S->getOperand(),V->getType()->getUnsignedVersion());
169 return new CastInst(V, S->getType(), "tmp.", InsertPt);
172 Value *visitAddExpr(SCEVAddExpr *S) {
173 const Type *Ty = S->getType();
174 Value *V = expandInTy(S->getOperand(S->getNumOperands()-1), Ty);
176 // Emit a bunch of add instructions
177 for (int i = S->getNumOperands()-2; i >= 0; --i)
178 V = BinaryOperator::create(Instruction::Add, V,
179 expandInTy(S->getOperand(i), Ty),
184 Value *visitMulExpr(SCEVMulExpr *S);
186 Value *visitUDivExpr(SCEVUDivExpr *S) {
187 const Type *Ty = S->getType();
188 Value *LHS = expandInTy(S->getLHS(), Ty);
189 Value *RHS = expandInTy(S->getRHS(), Ty);
190 return BinaryOperator::create(Instruction::Div, LHS, RHS, "tmp.",
194 Value *visitAddRecExpr(SCEVAddRecExpr *S);
196 Value *visitUnknown(SCEVUnknown *S) {
197 return S->getValue();
202 Value *SCEVExpander::visitMulExpr(SCEVMulExpr *S) {
203 const Type *Ty = S->getType();
204 int FirstOp = 0; // Set if we should emit a subtract.
205 if (SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(0)))
206 if (SC->getValue()->isAllOnesValue())
209 int i = S->getNumOperands()-2;
210 Value *V = expandInTy(S->getOperand(i+1), Ty);
212 // Emit a bunch of multiply instructions
213 for (; i >= FirstOp; --i)
214 V = BinaryOperator::create(Instruction::Mul, V,
215 expandInTy(S->getOperand(i), Ty),
217 // -1 * ... ---> 0 - ...
219 V = BinaryOperator::create(Instruction::Sub, Constant::getNullValue(Ty),
220 V, "tmp.", InsertPt);
224 Value *SCEVExpander::visitAddRecExpr(SCEVAddRecExpr *S) {
225 const Type *Ty = S->getType();
226 const Loop *L = S->getLoop();
227 // We cannot yet do fp recurrences, e.g. the xform of {X,+,F} --> X+{0,+,F}
228 assert(Ty->isIntegral() && "Cannot expand fp recurrences yet!");
230 // {X,+,F} --> X + {0,+,F}
231 if (!isa<SCEVConstant>(S->getStart()) ||
232 !cast<SCEVConstant>(S->getStart())->getValue()->isNullValue()) {
233 Value *Start = expandInTy(S->getStart(), Ty);
234 std::vector<SCEVHandle> NewOps(S->op_begin(), S->op_end());
235 NewOps[0] = SCEVUnknown::getIntegerSCEV(0, Ty);
236 Value *Rest = expandInTy(SCEVAddRecExpr::get(NewOps, L), Ty);
238 // FIXME: look for an existing add to use.
239 return BinaryOperator::create(Instruction::Add, Rest, Start, "tmp.",
243 // {0,+,1} --> Insert a canonical induction variable into the loop!
244 if (S->getNumOperands() == 2 &&
245 S->getOperand(1) == SCEVUnknown::getIntegerSCEV(1, Ty)) {
246 // Create and insert the PHI node for the induction variable in the
248 BasicBlock *Header = L->getHeader();
249 PHINode *PN = new PHINode(Ty, "indvar", Header->begin());
250 PN->addIncoming(Constant::getNullValue(Ty), L->getLoopPreheader());
252 pred_iterator HPI = pred_begin(Header);
253 assert(HPI != pred_end(Header) && "Loop with zero preds???");
254 if (!L->contains(*HPI)) ++HPI;
255 assert(HPI != pred_end(Header) && L->contains(*HPI) &&
256 "No backedge in loop?");
258 // Insert a unit add instruction right before the terminator corresponding
260 Constant *One = Ty->isFloatingPoint() ? (Constant*)ConstantFP::get(Ty, 1.0)
261 : ConstantInt::get(Ty, 1);
262 Instruction *Add = BinaryOperator::create(Instruction::Add, PN, One,
264 (*HPI)->getTerminator());
266 pred_iterator PI = pred_begin(Header);
267 if (*PI == L->getLoopPreheader())
269 PN->addIncoming(Add, *PI);
273 // Get the canonical induction variable I for this loop.
274 Value *I = getOrInsertCanonicalInductionVariable(L, Ty);
276 if (S->getNumOperands() == 2) { // {0,+,F} --> i*F
277 Value *F = expandInTy(S->getOperand(1), Ty);
278 return BinaryOperator::create(Instruction::Mul, I, F, "tmp.", InsertPt);
281 // If this is a chain of recurrences, turn it into a closed form, using the
282 // folders, then expandCodeFor the closed form. This allows the folders to
283 // simplify the expression without having to build a bunch of special code
285 SCEVHandle IH = SCEVUnknown::get(I); // Get I as a "symbolic" SCEV.
287 SCEVHandle V = S->evaluateAtIteration(IH);
288 //std::cerr << "Evaluated: " << *this << "\n to: " << *V << "\n";
290 return expandInTy(V, Ty);
295 Statistic<> NumRemoved ("indvars", "Number of aux indvars removed");
296 Statistic<> NumPointer ("indvars", "Number of pointer indvars promoted");
297 Statistic<> NumInserted("indvars", "Number of canonical indvars added");
298 Statistic<> NumReplaced("indvars", "Number of exit values replaced");
299 Statistic<> NumLFTR ("indvars", "Number of loop exit tests replaced");
301 class IndVarSimplify : public FunctionPass {
306 virtual bool runOnFunction(Function &) {
307 LI = &getAnalysis<LoopInfo>();
308 SE = &getAnalysis<ScalarEvolution>();
311 // Induction Variables live in the header nodes of loops
312 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
317 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
318 AU.addRequiredID(LoopSimplifyID);
319 AU.addRequired<ScalarEvolution>();
320 AU.addRequired<LoopInfo>();
321 AU.addPreservedID(LoopSimplifyID);
322 AU.setPreservesCFG();
325 void runOnLoop(Loop *L);
326 void EliminatePointerRecurrence(PHINode *PN, BasicBlock *Preheader,
327 std::set<Instruction*> &DeadInsts);
328 void LinearFunctionTestReplace(Loop *L, SCEV *IterationCount,
330 void RewriteLoopExitValues(Loop *L);
332 void DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts);
334 RegisterOpt<IndVarSimplify> X("indvars", "Canonicalize Induction Variables");
337 Pass *llvm::createIndVarSimplifyPass() {
338 return new IndVarSimplify();
341 /// DeleteTriviallyDeadInstructions - If any of the instructions is the
342 /// specified set are trivially dead, delete them and see if this makes any of
343 /// their operands subsequently dead.
344 void IndVarSimplify::
345 DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts) {
346 while (!Insts.empty()) {
347 Instruction *I = *Insts.begin();
348 Insts.erase(Insts.begin());
349 if (isInstructionTriviallyDead(I)) {
350 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
351 if (Instruction *U = dyn_cast<Instruction>(I->getOperand(i)))
353 SE->deleteInstructionFromRecords(I);
354 I->getParent()->getInstList().erase(I);
361 /// EliminatePointerRecurrence - Check to see if this is a trivial GEP pointer
362 /// recurrence. If so, change it into an integer recurrence, permitting
363 /// analysis by the SCEV routines.
364 void IndVarSimplify::EliminatePointerRecurrence(PHINode *PN,
365 BasicBlock *Preheader,
366 std::set<Instruction*> &DeadInsts) {
367 assert(PN->getNumIncomingValues() == 2 && "Noncanonicalized loop!");
368 unsigned PreheaderIdx = PN->getBasicBlockIndex(Preheader);
369 unsigned BackedgeIdx = PreheaderIdx^1;
370 if (GetElementPtrInst *GEPI =
371 dyn_cast<GetElementPtrInst>(PN->getIncomingValue(BackedgeIdx)))
372 if (GEPI->getOperand(0) == PN) {
373 assert(GEPI->getNumOperands() == 2 && "GEP types must mismatch!");
375 // Okay, we found a pointer recurrence. Transform this pointer
376 // recurrence into an integer recurrence. Compute the value that gets
377 // added to the pointer at every iteration.
378 Value *AddedVal = GEPI->getOperand(1);
380 // Insert a new integer PHI node into the top of the block.
381 PHINode *NewPhi = new PHINode(AddedVal->getType(),
382 PN->getName()+".rec", PN);
383 NewPhi->addIncoming(Constant::getNullValue(NewPhi->getType()),
385 // Create the new add instruction.
386 Value *NewAdd = BinaryOperator::create(Instruction::Add, NewPhi,
388 GEPI->getName()+".rec", GEPI);
389 NewPhi->addIncoming(NewAdd, PN->getIncomingBlock(BackedgeIdx));
391 // Update the existing GEP to use the recurrence.
392 GEPI->setOperand(0, PN->getIncomingValue(PreheaderIdx));
394 // Update the GEP to use the new recurrence we just inserted.
395 GEPI->setOperand(1, NewAdd);
397 // Finally, if there are any other users of the PHI node, we must
398 // insert a new GEP instruction that uses the pre-incremented version
399 // of the induction amount.
400 if (!PN->use_empty()) {
401 BasicBlock::iterator InsertPos = PN; ++InsertPos;
402 while (isa<PHINode>(InsertPos)) ++InsertPos;
403 std::string Name = PN->getName(); PN->setName("");
405 new GetElementPtrInst(PN->getIncomingValue(PreheaderIdx),
406 std::vector<Value*>(1, NewPhi), Name,
408 PN->replaceAllUsesWith(PreInc);
411 // Delete the old PHI for sure, and the GEP if its otherwise unused.
412 DeadInsts.insert(PN);
419 /// LinearFunctionTestReplace - This method rewrites the exit condition of the
420 /// loop to be a canonical != comparison against the incremented loop induction
421 /// variable. This pass is able to rewrite the exit tests of any loop where the
422 /// SCEV analysis can determine a loop-invariant trip count of the loop, which
423 /// is actually a much broader range than just linear tests.
424 void IndVarSimplify::LinearFunctionTestReplace(Loop *L, SCEV *IterationCount,
426 // Find the exit block for the loop. We can currently only handle loops with
428 std::vector<BasicBlock*> ExitBlocks;
429 L->getExitBlocks(ExitBlocks);
430 if (ExitBlocks.size() != 1) return;
431 BasicBlock *ExitBlock = ExitBlocks[0];
433 // Make sure there is only one predecessor block in the loop.
434 BasicBlock *ExitingBlock = 0;
435 for (pred_iterator PI = pred_begin(ExitBlock), PE = pred_end(ExitBlock);
437 if (L->contains(*PI)) {
438 if (ExitingBlock == 0)
441 return; // Multiple exits from loop to this block.
443 assert(ExitingBlock && "Loop info is broken");
445 if (!isa<BranchInst>(ExitingBlock->getTerminator()))
446 return; // Can't rewrite non-branch yet
447 BranchInst *BI = cast<BranchInst>(ExitingBlock->getTerminator());
448 assert(BI->isConditional() && "Must be conditional to be part of loop!");
450 std::set<Instruction*> InstructionsToDelete;
451 if (Instruction *Cond = dyn_cast<Instruction>(BI->getCondition()))
452 InstructionsToDelete.insert(Cond);
454 // If the exiting block is not the same as the backedge block, we must compare
455 // against the preincremented value, otherwise we prefer to compare against
456 // the post-incremented value.
457 BasicBlock *Header = L->getHeader();
458 pred_iterator HPI = pred_begin(Header);
459 assert(HPI != pred_end(Header) && "Loop with zero preds???");
460 if (!L->contains(*HPI)) ++HPI;
461 assert(HPI != pred_end(Header) && L->contains(*HPI) &&
462 "No backedge in loop?");
464 SCEVHandle TripCount = IterationCount;
466 if (*HPI == ExitingBlock) {
467 // The IterationCount expression contains the number of times that the
468 // backedge actually branches to the loop header. This is one less than the
469 // number of times the loop executes, so add one to it.
470 Constant *OneC = ConstantInt::get(IterationCount->getType(), 1);
471 TripCount = SCEVAddExpr::get(IterationCount, SCEVUnknown::get(OneC));
472 IndVar = L->getCanonicalInductionVariableIncrement();
474 // We have to use the preincremented value...
475 IndVar = L->getCanonicalInductionVariable();
478 // Expand the code for the iteration count into the preheader of the loop.
479 BasicBlock *Preheader = L->getLoopPreheader();
480 Value *ExitCnt = RW.expandCodeFor(TripCount, Preheader->getTerminator(),
483 // Insert a new setne or seteq instruction before the branch.
484 Instruction::BinaryOps Opcode;
485 if (L->contains(BI->getSuccessor(0)))
486 Opcode = Instruction::SetNE;
488 Opcode = Instruction::SetEQ;
490 Value *Cond = new SetCondInst(Opcode, IndVar, ExitCnt, "exitcond", BI);
491 BI->setCondition(Cond);
495 DeleteTriviallyDeadInstructions(InstructionsToDelete);
499 /// RewriteLoopExitValues - Check to see if this loop has a computable
500 /// loop-invariant execution count. If so, this means that we can compute the
501 /// final value of any expressions that are recurrent in the loop, and
502 /// substitute the exit values from the loop into any instructions outside of
503 /// the loop that use the final values of the current expressions.
504 void IndVarSimplify::RewriteLoopExitValues(Loop *L) {
505 BasicBlock *Preheader = L->getLoopPreheader();
507 // Scan all of the instructions in the loop, looking at those that have
508 // extra-loop users and which are recurrences.
509 SCEVExpander Rewriter(*SE, *LI);
511 // We insert the code into the preheader of the loop if the loop contains
512 // multiple exit blocks, or in the exit block if there is exactly one.
513 BasicBlock *BlockToInsertInto;
514 std::vector<BasicBlock*> ExitBlocks;
515 L->getExitBlocks(ExitBlocks);
516 if (ExitBlocks.size() == 1)
517 BlockToInsertInto = ExitBlocks[0];
519 BlockToInsertInto = Preheader;
520 BasicBlock::iterator InsertPt = BlockToInsertInto->begin();
521 while (isa<PHINode>(InsertPt)) ++InsertPt;
523 bool HasConstantItCount = isa<SCEVConstant>(SE->getIterationCount(L));
525 std::set<Instruction*> InstructionsToDelete;
527 for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i)
528 if (LI->getLoopFor(L->getBlocks()[i]) == L) { // Not in a subloop...
529 BasicBlock *BB = L->getBlocks()[i];
530 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
531 if (I->getType()->isInteger()) { // Is an integer instruction
532 SCEVHandle SH = SE->getSCEV(I);
533 if (SH->hasComputableLoopEvolution(L) || // Varies predictably
534 HasConstantItCount) {
535 // Find out if this predictably varying value is actually used
536 // outside of the loop. "extra" as opposed to "intra".
537 std::vector<User*> ExtraLoopUsers;
538 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
540 if (!L->contains(cast<Instruction>(*UI)->getParent()))
541 ExtraLoopUsers.push_back(*UI);
542 if (!ExtraLoopUsers.empty()) {
543 // Okay, this instruction has a user outside of the current loop
544 // and varies predictably in this loop. Evaluate the value it
545 // contains when the loop exits, and insert code for it.
546 SCEVHandle ExitValue = SE->getSCEVAtScope(I, L->getParentLoop());
547 if (!isa<SCEVCouldNotCompute>(ExitValue)) {
550 Value *NewVal = Rewriter.expandCodeFor(ExitValue, InsertPt,
553 // Rewrite any users of the computed value outside of the loop
554 // with the newly computed value.
555 for (unsigned i = 0, e = ExtraLoopUsers.size(); i != e; ++i)
556 ExtraLoopUsers[i]->replaceUsesOfWith(I, NewVal);
558 // If this instruction is dead now, schedule it to be removed.
560 InstructionsToDelete.insert(I);
567 DeleteTriviallyDeadInstructions(InstructionsToDelete);
571 void IndVarSimplify::runOnLoop(Loop *L) {
572 // First step. Check to see if there are any trivial GEP pointer recurrences.
573 // If there are, change them into integer recurrences, permitting analysis by
574 // the SCEV routines.
576 BasicBlock *Header = L->getHeader();
577 BasicBlock *Preheader = L->getLoopPreheader();
579 std::set<Instruction*> DeadInsts;
580 for (BasicBlock::iterator I = Header->begin();
581 PHINode *PN = dyn_cast<PHINode>(I); ++I)
582 if (isa<PointerType>(PN->getType()))
583 EliminatePointerRecurrence(PN, Preheader, DeadInsts);
585 if (!DeadInsts.empty())
586 DeleteTriviallyDeadInstructions(DeadInsts);
589 // Next, transform all loops nesting inside of this loop.
590 for (LoopInfo::iterator I = L->begin(), E = L->end(); I != E; ++I)
593 // Check to see if this loop has a computable loop-invariant execution count.
594 // If so, this means that we can compute the final value of any expressions
595 // that are recurrent in the loop, and substitute the exit values from the
596 // loop into any instructions outside of the loop that use the final values of
597 // the current expressions.
599 SCEVHandle IterationCount = SE->getIterationCount(L);
600 if (!isa<SCEVCouldNotCompute>(IterationCount))
601 RewriteLoopExitValues(L);
603 // Next, analyze all of the induction variables in the loop, canonicalizing
604 // auxillary induction variables.
605 std::vector<std::pair<PHINode*, SCEVHandle> > IndVars;
607 for (BasicBlock::iterator I = Header->begin();
608 PHINode *PN = dyn_cast<PHINode>(I); ++I)
609 if (PN->getType()->isInteger()) { // FIXME: when we have fast-math, enable!
610 SCEVHandle SCEV = SE->getSCEV(PN);
611 if (SCEV->hasComputableLoopEvolution(L))
612 if (SE->shouldSubstituteIndVar(SCEV)) // HACK!
613 IndVars.push_back(std::make_pair(PN, SCEV));
616 // If there are no induction variables in the loop, there is nothing more to
618 if (IndVars.empty()) {
619 // Actually, if we know how many times the loop iterates, lets insert a
620 // canonical induction variable to help subsequent passes.
621 if (!isa<SCEVCouldNotCompute>(IterationCount)) {
622 SCEVExpander Rewriter(*SE, *LI);
623 Rewriter.getOrInsertCanonicalInductionVariable(L,
624 IterationCount->getType());
625 LinearFunctionTestReplace(L, IterationCount, Rewriter);
630 // Compute the type of the largest recurrence expression.
632 const Type *LargestType = IndVars[0].first->getType();
633 bool DifferingSizes = false;
634 for (unsigned i = 1, e = IndVars.size(); i != e; ++i) {
635 const Type *Ty = IndVars[i].first->getType();
636 DifferingSizes |= Ty->getPrimitiveSize() != LargestType->getPrimitiveSize();
637 if (Ty->getPrimitiveSize() > LargestType->getPrimitiveSize())
641 // Create a rewriter object which we'll use to transform the code with.
642 SCEVExpander Rewriter(*SE, *LI);
644 // Now that we know the largest of of the induction variables in this loop,
645 // insert a canonical induction variable of the largest size.
646 LargestType = LargestType->getUnsignedVersion();
647 Value *IndVar = Rewriter.getOrInsertCanonicalInductionVariable(L,LargestType);
651 if (!isa<SCEVCouldNotCompute>(IterationCount))
652 LinearFunctionTestReplace(L, IterationCount, Rewriter);
654 // Now that we have a canonical induction variable, we can rewrite any
655 // recurrences in terms of the induction variable. Start with the auxillary
656 // induction variables, and recursively rewrite any of their uses.
657 BasicBlock::iterator InsertPt = Header->begin();
658 while (isa<PHINode>(InsertPt)) ++InsertPt;
660 // If there were induction variables of other sizes, cast the primary
661 // induction variable to the right size for them, avoiding the need for the
662 // code evaluation methods to insert induction variables of different sizes.
663 if (DifferingSizes) {
664 bool InsertedSizes[17] = { false };
665 InsertedSizes[LargestType->getPrimitiveSize()] = true;
666 for (unsigned i = 0, e = IndVars.size(); i != e; ++i)
667 if (!InsertedSizes[IndVars[i].first->getType()->getPrimitiveSize()]) {
668 PHINode *PN = IndVars[i].first;
669 InsertedSizes[PN->getType()->getPrimitiveSize()] = true;
670 Instruction *New = new CastInst(IndVar,
671 PN->getType()->getUnsignedVersion(),
673 Rewriter.addInsertedValue(New, SE->getSCEV(New));
677 // If there were induction variables of other sizes, cast the primary
678 // induction variable to the right size for them, avoiding the need for the
679 // code evaluation methods to insert induction variables of different sizes.
680 std::map<unsigned, Value*> InsertedSizes;
681 while (!IndVars.empty()) {
682 PHINode *PN = IndVars.back().first;
683 Value *NewVal = Rewriter.expandCodeFor(IndVars.back().second, InsertPt,
685 std::string Name = PN->getName();
687 NewVal->setName(Name);
689 // Replace the old PHI Node with the inserted computation.
690 PN->replaceAllUsesWith(NewVal);
691 DeadInsts.insert(PN);
698 // Now replace all derived expressions in the loop body with simpler
700 for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i)
701 if (LI->getLoopFor(L->getBlocks()[i]) == L) { // Not in a subloop...
702 BasicBlock *BB = L->getBlocks()[i];
703 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
704 if (I->getType()->isInteger() && // Is an integer instruction
706 !Rewriter.isInsertedInstruction(I)) {
707 SCEVHandle SH = SE->getSCEV(I);
708 Value *V = Rewriter.expandCodeFor(SH, I, I->getType());
710 if (isa<Instruction>(V)) {
711 std::string Name = I->getName();
715 I->replaceAllUsesWith(V);
724 DeleteTriviallyDeadInstructions(DeadInsts);