ScalarEvolutionExpander.cpp revision b679de2a21f5ecbae81b444290d72af93aa5b0b3 
1//===- ScalarEvolutionExpander.cpp - Scalar Evolution Analysis --*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file contains the implementation of the scalar evolution expander,
11// which is used to generate the code corresponding to a given scalar evolution
12// expression.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/Analysis/ScalarEvolutionExpander.h"
17#include "llvm/Analysis/LoopInfo.h"
18#include "llvm/Target/TargetData.h"
19using namespace llvm;
20
21/// InsertCastOfTo - Insert a cast of V to the specified type, doing what
22/// we can to share the casts.
23Value *SCEVExpander::InsertCastOfTo(Instruction::CastOps opcode, Value *V,
24                                    const Type *Ty) {
25  // Short-circuit unnecessary bitcasts.
26  if (opcode == Instruction::BitCast && V->getType() == Ty)
27    return V;
28
29  // Short-circuit unnecessary inttoptr<->ptrtoint casts.
30  if ((opcode == Instruction::PtrToInt || opcode == Instruction::IntToPtr) &&
31      SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(V->getType())) {
32    if (CastInst *CI = dyn_cast<CastInst>(V))
33      if ((CI->getOpcode() == Instruction::PtrToInt ||
34           CI->getOpcode() == Instruction::IntToPtr) &&
35          SE.getTypeSizeInBits(CI->getType()) ==
36          SE.getTypeSizeInBits(CI->getOperand(0)->getType()))
37        return CI->getOperand(0);
38    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
39      if ((CE->getOpcode() == Instruction::PtrToInt ||
40           CE->getOpcode() == Instruction::IntToPtr) &&
41          SE.getTypeSizeInBits(CE->getType()) ==
42          SE.getTypeSizeInBits(CE->getOperand(0)->getType()))
43        return CE->getOperand(0);
44  }
45
46  // FIXME: keep track of the cast instruction.
47  if (Constant *C = dyn_cast<Constant>(V))
48    return ConstantExpr::getCast(opcode, C, Ty);
49
50  if (Argument *A = dyn_cast<Argument>(V)) {
51    // Check to see if there is already a cast!
52    for (Value::use_iterator UI = A->use_begin(), E = A->use_end();
53         UI != E; ++UI) {
54      if ((*UI)->getType() == Ty)
55        if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI)))
56          if (CI->getOpcode() == opcode) {
57            // If the cast isn't the first instruction of the function, move it.
58            if (BasicBlock::iterator(CI) !=
59                A->getParent()->getEntryBlock().begin()) {
60              // If the CastInst is the insert point, change the insert point.
61              if (CI == InsertPt) ++InsertPt;
62              // Splice the cast at the beginning of the entry block.
63              CI->moveBefore(A->getParent()->getEntryBlock().begin());
64            }
65            return CI;
66          }
67    }
68    Instruction *I = CastInst::Create(opcode, V, Ty, V->getName(),
69                                      A->getParent()->getEntryBlock().begin());
70    InsertedValues.insert(I);
71    return I;
72  }
73
74  Instruction *I = cast<Instruction>(V);
75
76  // Check to see if there is already a cast.  If there is, use it.
77  for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
78       UI != E; ++UI) {
79    if ((*UI)->getType() == Ty)
80      if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI)))
81        if (CI->getOpcode() == opcode) {
82          BasicBlock::iterator It = I; ++It;
83          if (isa<InvokeInst>(I))
84            It = cast<InvokeInst>(I)->getNormalDest()->begin();
85          while (isa<PHINode>(It)) ++It;
86          if (It != BasicBlock::iterator(CI)) {
87            // If the CastInst is the insert point, change the insert point.
88            if (CI == InsertPt) ++InsertPt;
89            // Splice the cast immediately after the operand in question.
90            CI->moveBefore(It);
91          }
92          return CI;
93        }
94  }
95  BasicBlock::iterator IP = I; ++IP;
96  if (InvokeInst *II = dyn_cast<InvokeInst>(I))
97    IP = II->getNormalDest()->begin();
98  while (isa<PHINode>(IP)) ++IP;
99  Instruction *CI = CastInst::Create(opcode, V, Ty, V->getName(), IP);
100  InsertedValues.insert(CI);
101  return CI;
102}
103
104/// InsertNoopCastOfTo - Insert a cast of V to the specified type,
105/// which must be possible with a noop cast.
106Value *SCEVExpander::InsertNoopCastOfTo(Value *V, const Type *Ty) {
107  Instruction::CastOps Op = CastInst::getCastOpcode(V, false, Ty, false);
108  assert((Op == Instruction::BitCast ||
109          Op == Instruction::PtrToInt ||
110          Op == Instruction::IntToPtr) &&
111         "InsertNoopCastOfTo cannot perform non-noop casts!");
112  assert(SE.getTypeSizeInBits(V->getType()) == SE.getTypeSizeInBits(Ty) &&
113         "InsertNoopCastOfTo cannot change sizes!");
114  return InsertCastOfTo(Op, V, Ty);
115}
116
117/// InsertBinop - Insert the specified binary operator, doing a small amount
118/// of work to avoid inserting an obviously redundant operation.
119Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode, Value *LHS,
120                                 Value *RHS, BasicBlock::iterator InsertPt) {
121  // Fold a binop with constant operands.
122  if (Constant *CLHS = dyn_cast<Constant>(LHS))
123    if (Constant *CRHS = dyn_cast<Constant>(RHS))
124      return ConstantExpr::get(Opcode, CLHS, CRHS);
125
126  // Do a quick scan to see if we have this binop nearby.  If so, reuse it.
127  unsigned ScanLimit = 6;
128  BasicBlock::iterator BlockBegin = InsertPt->getParent()->begin();
129  if (InsertPt != BlockBegin) {
130    // Scanning starts from the last instruction before InsertPt.
131    BasicBlock::iterator IP = InsertPt;
132    --IP;
133    for (; ScanLimit; --IP, --ScanLimit) {
134      if (IP->getOpcode() == (unsigned)Opcode && IP->getOperand(0) == LHS &&
135          IP->getOperand(1) == RHS)
136        return IP;
137      if (IP == BlockBegin) break;
138    }
139  }
140
141  // If we haven't found this binop, insert it.
142  Instruction *BO = BinaryOperator::Create(Opcode, LHS, RHS, "tmp", InsertPt);
143  InsertedValues.insert(BO);
144  return BO;
145}
146
147/// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
148/// instead of using ptrtoint+arithmetic+inttoptr.
149Value *SCEVExpander::expandAddToGEP(const SCEVAddExpr *S,
150                                    const PointerType *PTy,
151                                    const Type *Ty,
152                                    Value *V) {
153  const Type *ElTy = PTy->getElementType();
154  SmallVector<Value *, 4> GepIndices;
155  std::vector<SCEVHandle> Ops = S->getOperands();
156  bool AnyNonZeroIndices = false;
157  Ops.pop_back();
158
159  // Decend down the pointer's type and attempt to convert the other
160  // operands into GEP indices, at each level. The first index in a GEP
161  // indexes into the array implied by the pointer operand; the rest of
162  // the indices index into the element or field type selected by the
163  // preceding index.
164  for (;;) {
165    APInt ElSize = APInt(SE.getTypeSizeInBits(Ty),
166                         ElTy->isSized() ?  SE.TD->getTypeAllocSize(ElTy) : 0);
167    std::vector<SCEVHandle> NewOps;
168    std::vector<SCEVHandle> ScaledOps;
169    for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
170      if (ElSize != 0) {
171        // For a Constant, check for a multiple of the pointer type's
172        // scale size.
173        if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i]))
174          if (!C->getValue()->getValue().srem(ElSize)) {
175            ConstantInt *CI =
176              ConstantInt::get(C->getValue()->getValue().sdiv(ElSize));
177            SCEVHandle Div = SE.getConstant(CI);
178            ScaledOps.push_back(Div);
179            continue;
180          }
181        // In a Mul, check if there is a constant operand which is a multiple
182        // of the pointer type's scale size.
183        if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i]))
184          if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0)))
185            if (!C->getValue()->getValue().srem(ElSize)) {
186              std::vector<SCEVHandle> NewMulOps(M->getOperands());
187              NewMulOps[0] =
188                SE.getConstant(C->getValue()->getValue().sdiv(ElSize));
189              ScaledOps.push_back(SE.getMulExpr(NewMulOps));
190              continue;
191            }
192        // In an Unknown, check if the underlying value is a Mul by a constant
193        // which is equal to the pointer type's scale size.
194        if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Ops[i]))
195          if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U->getValue()))
196            if (BO->getOpcode() == Instruction::Mul)
197              if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1)))
198                if (CI->getValue() == ElSize) {
199                  ScaledOps.push_back(SE.getUnknown(BO->getOperand(0)));
200                  continue;
201                }
202        // If the pointer type's scale size is 1, no scaling is necessary
203        // and any value can be used.
204        if (ElSize == 1) {
205          ScaledOps.push_back(Ops[i]);
206          continue;
207        }
208      }
209      NewOps.push_back(Ops[i]);
210    }
211    Ops = NewOps;
212    AnyNonZeroIndices |= !ScaledOps.empty();
213    Value *Scaled = ScaledOps.empty() ?
214                    Constant::getNullValue(Ty) :
215                    expandCodeFor(SE.getAddExpr(ScaledOps), Ty);
216    GepIndices.push_back(Scaled);
217
218    // Collect struct field index operands.
219    if (!Ops.empty())
220      while (const StructType *STy = dyn_cast<StructType>(ElTy)) {
221        if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[0]))
222          if (SE.getTypeSizeInBits(C->getType()) <= 64) {
223            const StructLayout &SL = *SE.TD->getStructLayout(STy);
224            uint64_t FullOffset = C->getValue()->getZExtValue();
225            if (FullOffset < SL.getSizeInBytes()) {
226              unsigned ElIdx = SL.getElementContainingOffset(FullOffset);
227              GepIndices.push_back(ConstantInt::get(Type::Int32Ty, ElIdx));
228              ElTy = STy->getTypeAtIndex(ElIdx);
229              Ops[0] =
230                SE.getConstant(ConstantInt::get(Ty,
231                                                FullOffset -
232                                                  SL.getElementOffset(ElIdx)));
233              AnyNonZeroIndices = true;
234              continue;
235            }
236          }
237        break;
238      }
239
240    if (const ArrayType *ATy = dyn_cast<ArrayType>(ElTy)) {
241      ElTy = ATy->getElementType();
242      continue;
243    }
244    break;
245  }
246
247  // If none of the operands were convertable to proper GEP indices, cast
248  // the base to i8* and do an ugly getelementptr with that. It's still
249  // better than ptrtoint+arithmetic+inttoptr at least.
250  if (!AnyNonZeroIndices) {
251    V = InsertNoopCastOfTo(V,
252                           Type::Int8Ty->getPointerTo(PTy->getAddressSpace()));
253    Value *Idx = expand(SE.getAddExpr(Ops));
254    Idx = InsertNoopCastOfTo(Idx, Ty);
255
256    // Fold a GEP with constant operands.
257    if (Constant *CLHS = dyn_cast<Constant>(V))
258      if (Constant *CRHS = dyn_cast<Constant>(Idx))
259        return ConstantExpr::getGetElementPtr(CLHS, &CRHS, 1);
260
261    // Do a quick scan to see if we have this GEP nearby.  If so, reuse it.
262    unsigned ScanLimit = 6;
263    BasicBlock::iterator BlockBegin = InsertPt->getParent()->begin();
264    if (InsertPt != BlockBegin) {
265      // Scanning starts from the last instruction before InsertPt.
266      BasicBlock::iterator IP = InsertPt;
267      --IP;
268      for (; ScanLimit; --IP, --ScanLimit) {
269        if (IP->getOpcode() == Instruction::GetElementPtr &&
270            IP->getOperand(0) == V && IP->getOperand(1) == Idx)
271          return IP;
272        if (IP == BlockBegin) break;
273      }
274    }
275
276    Value *GEP = GetElementPtrInst::Create(V, Idx, "scevgep", InsertPt);
277    InsertedValues.insert(GEP);
278    return GEP;
279  }
280
281  // Insert a pretty getelementptr.
282  Value *GEP = GetElementPtrInst::Create(V,
283                                         GepIndices.begin(),
284                                         GepIndices.end(),
285                                         "scevgep", InsertPt);
286  Ops.push_back(SE.getUnknown(GEP));
287  InsertedValues.insert(GEP);
288  return expand(SE.getAddExpr(Ops));
289}
290
291Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) {
292  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
293  Value *V = expand(S->getOperand(S->getNumOperands()-1));
294
295  // Turn things like ptrtoint+arithmetic+inttoptr into GEP. This helps
296  // BasicAliasAnalysis analyze the result. However, it suffers from the
297  // underlying bug described in PR2831. Addition in LLVM currently always
298  // has two's complement wrapping guaranteed. However, the semantics for
299  // getelementptr overflow are ambiguous. In the common case though, this
300  // expansion gets used when a GEP in the original code has been converted
301  // into integer arithmetic, in which case the resulting code will be no
302  // more undefined than it was originally.
303  if (SE.TD)
304    if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
305      return expandAddToGEP(S, PTy, Ty, V);
306
307  V = InsertNoopCastOfTo(V, Ty);
308
309  // Emit a bunch of add instructions
310  for (int i = S->getNumOperands()-2; i >= 0; --i) {
311    Value *W = expand(S->getOperand(i));
312    W = InsertNoopCastOfTo(W, Ty);
313    V = InsertBinop(Instruction::Add, V, W, InsertPt);
314  }
315  return V;
316}
317
318Value *SCEVExpander::visitMulExpr(const SCEVMulExpr *S) {
319  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
320  int FirstOp = 0;  // Set if we should emit a subtract.
321  if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(0)))
322    if (SC->getValue()->isAllOnesValue())
323      FirstOp = 1;
324
325  int i = S->getNumOperands()-2;
326  Value *V = expand(S->getOperand(i+1));
327  V = InsertNoopCastOfTo(V, Ty);
328
329  // Emit a bunch of multiply instructions
330  for (; i >= FirstOp; --i) {
331    Value *W = expand(S->getOperand(i));
332    W = InsertNoopCastOfTo(W, Ty);
333    V = InsertBinop(Instruction::Mul, V, W, InsertPt);
334  }
335
336  // -1 * ...  --->  0 - ...
337  if (FirstOp == 1)
338    V = InsertBinop(Instruction::Sub, Constant::getNullValue(Ty), V, InsertPt);
339  return V;
340}
341
342Value *SCEVExpander::visitUDivExpr(const SCEVUDivExpr *S) {
343  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
344
345  Value *LHS = expand(S->getLHS());
346  LHS = InsertNoopCastOfTo(LHS, Ty);
347  if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getRHS())) {
348    const APInt &RHS = SC->getValue()->getValue();
349    if (RHS.isPowerOf2())
350      return InsertBinop(Instruction::LShr, LHS,
351                         ConstantInt::get(Ty, RHS.logBase2()),
352                         InsertPt);
353  }
354
355  Value *RHS = expand(S->getRHS());
356  RHS = InsertNoopCastOfTo(RHS, Ty);
357  return InsertBinop(Instruction::UDiv, LHS, RHS, InsertPt);
358}
359
360Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) {
361  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
362  const Loop *L = S->getLoop();
363
364  // {X,+,F} --> X + {0,+,F}
365  if (!S->getStart()->isZero()) {
366    std::vector<SCEVHandle> NewOps(S->getOperands());
367    NewOps[0] = SE.getIntegerSCEV(0, Ty);
368    Value *Rest = expand(SE.getAddRecExpr(NewOps, L));
369    return expand(SE.getAddExpr(S->getStart(), SE.getUnknown(Rest)));
370  }
371
372  // {0,+,1} --> Insert a canonical induction variable into the loop!
373  if (S->isAffine() &&
374      S->getOperand(1) == SE.getIntegerSCEV(1, Ty)) {
375    // Create and insert the PHI node for the induction variable in the
376    // specified loop.
377    BasicBlock *Header = L->getHeader();
378    PHINode *PN = PHINode::Create(Ty, "indvar", Header->begin());
379    InsertedValues.insert(PN);
380    PN->addIncoming(Constant::getNullValue(Ty), L->getLoopPreheader());
381
382    pred_iterator HPI = pred_begin(Header);
383    assert(HPI != pred_end(Header) && "Loop with zero preds???");
384    if (!L->contains(*HPI)) ++HPI;
385    assert(HPI != pred_end(Header) && L->contains(*HPI) &&
386           "No backedge in loop?");
387
388    // Insert a unit add instruction right before the terminator corresponding
389    // to the back-edge.
390    Constant *One = ConstantInt::get(Ty, 1);
391    Instruction *Add = BinaryOperator::CreateAdd(PN, One, "indvar.next",
392                                                 (*HPI)->getTerminator());
393    InsertedValues.insert(Add);
394
395    pred_iterator PI = pred_begin(Header);
396    if (*PI == L->getLoopPreheader())
397      ++PI;
398    PN->addIncoming(Add, *PI);
399    return PN;
400  }
401
402  // Get the canonical induction variable I for this loop.
403  Value *I = getOrInsertCanonicalInductionVariable(L, Ty);
404
405  // If this is a simple linear addrec, emit it now as a special case.
406  if (S->isAffine()) {   // {0,+,F} --> i*F
407    Value *F = expand(S->getOperand(1));
408    F = InsertNoopCastOfTo(F, Ty);
409
410    // IF the step is by one, just return the inserted IV.
411    if (ConstantInt *CI = dyn_cast<ConstantInt>(F))
412      if (CI->getValue() == 1)
413        return I;
414
415    // If the insert point is directly inside of the loop, emit the multiply at
416    // the insert point.  Otherwise, L is a loop that is a parent of the insert
417    // point loop.  If we can, move the multiply to the outer most loop that it
418    // is safe to be in.
419    BasicBlock::iterator MulInsertPt = getInsertionPoint();
420    Loop *InsertPtLoop = SE.LI->getLoopFor(MulInsertPt->getParent());
421    if (InsertPtLoop != L && InsertPtLoop &&
422        L->contains(InsertPtLoop->getHeader())) {
423      do {
424        // If we cannot hoist the multiply out of this loop, don't.
425        if (!InsertPtLoop->isLoopInvariant(F)) break;
426
427        BasicBlock *InsertPtLoopPH = InsertPtLoop->getLoopPreheader();
428
429        // If this loop hasn't got a preheader, we aren't able to hoist the
430        // multiply.
431        if (!InsertPtLoopPH)
432          break;
433
434        // Otherwise, move the insert point to the preheader.
435        MulInsertPt = InsertPtLoopPH->getTerminator();
436        InsertPtLoop = InsertPtLoop->getParentLoop();
437      } while (InsertPtLoop != L);
438    }
439
440    return InsertBinop(Instruction::Mul, I, F, MulInsertPt);
441  }
442
443  // If this is a chain of recurrences, turn it into a closed form, using the
444  // folders, then expandCodeFor the closed form.  This allows the folders to
445  // simplify the expression without having to build a bunch of special code
446  // into this folder.
447  SCEVHandle IH = SE.getUnknown(I);   // Get I as a "symbolic" SCEV.
448
449  SCEVHandle V = S->evaluateAtIteration(IH, SE);
450  //cerr << "Evaluated: " << *this << "\n     to: " << *V << "\n";
451
452  return expand(V);
453}
454
455Value *SCEVExpander::visitTruncateExpr(const SCEVTruncateExpr *S) {
456  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
457  Value *V = expand(S->getOperand());
458  V = InsertNoopCastOfTo(V, SE.getEffectiveSCEVType(V->getType()));
459  Instruction *I = new TruncInst(V, Ty, "tmp.", InsertPt);
460  InsertedValues.insert(I);
461  return I;
462}
463
464Value *SCEVExpander::visitZeroExtendExpr(const SCEVZeroExtendExpr *S) {
465  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
466  Value *V = expand(S->getOperand());
467  V = InsertNoopCastOfTo(V, SE.getEffectiveSCEVType(V->getType()));
468  Instruction *I = new ZExtInst(V, Ty, "tmp.", InsertPt);
469  InsertedValues.insert(I);
470  return I;
471}
472
473Value *SCEVExpander::visitSignExtendExpr(const SCEVSignExtendExpr *S) {
474  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
475  Value *V = expand(S->getOperand());
476  V = InsertNoopCastOfTo(V, SE.getEffectiveSCEVType(V->getType()));
477  Instruction *I = new SExtInst(V, Ty, "tmp.", InsertPt);
478  InsertedValues.insert(I);
479  return I;
480}
481
482Value *SCEVExpander::visitSMaxExpr(const SCEVSMaxExpr *S) {
483  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
484  Value *LHS = expand(S->getOperand(0));
485  LHS = InsertNoopCastOfTo(LHS, Ty);
486  for (unsigned i = 1; i < S->getNumOperands(); ++i) {
487    Value *RHS = expand(S->getOperand(i));
488    RHS = InsertNoopCastOfTo(RHS, Ty);
489    Instruction *ICmp =
490      new ICmpInst(ICmpInst::ICMP_SGT, LHS, RHS, "tmp", InsertPt);
491    InsertedValues.insert(ICmp);
492    Instruction *Sel = SelectInst::Create(ICmp, LHS, RHS, "smax", InsertPt);
493    InsertedValues.insert(Sel);
494    LHS = Sel;
495  }
496  return LHS;
497}
498
499Value *SCEVExpander::visitUMaxExpr(const SCEVUMaxExpr *S) {
500  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
501  Value *LHS = expand(S->getOperand(0));
502  LHS = InsertNoopCastOfTo(LHS, Ty);
503  for (unsigned i = 1; i < S->getNumOperands(); ++i) {
504    Value *RHS = expand(S->getOperand(i));
505    RHS = InsertNoopCastOfTo(RHS, Ty);
506    Instruction *ICmp =
507      new ICmpInst(ICmpInst::ICMP_UGT, LHS, RHS, "tmp", InsertPt);
508    InsertedValues.insert(ICmp);
509    Instruction *Sel = SelectInst::Create(ICmp, LHS, RHS, "umax", InsertPt);
510    InsertedValues.insert(Sel);
511    LHS = Sel;
512  }
513  return LHS;
514}
515
516Value *SCEVExpander::expandCodeFor(SCEVHandle SH, const Type *Ty) {
517  // Expand the code for this SCEV.
518  Value *V = expand(SH);
519  if (Ty) {
520    assert(SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(SH->getType()) &&
521           "non-trivial casts should be done with the SCEVs directly!");
522    V = InsertNoopCastOfTo(V, Ty);
523  }
524  return V;
525}
526
527Value *SCEVExpander::expand(const SCEV *S) {
528  // Check to see if we already expanded this.
529  std::map<SCEVHandle, AssertingVH<Value> >::iterator I = InsertedExpressions.find(S);
530  if (I != InsertedExpressions.end())
531    return I->second;
532
533  Value *V = visit(S);
534  InsertedExpressions[S] = V;
535  return V;
536}
537