Import LLVM, at r72732.

1 files changed, 646 insertions, 0 deletions

diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp
new file mode 100644
index 0000000..7ba8268
--- /dev/null
+++ b/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -0,0 +1,646 @@
+//===- ScalarEvolutionExpander.cpp - Scalar Evolution Analysis --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the implementation of the scalar evolution expander,
+// which is used to generate the code corresponding to a given scalar evolution
+// expression.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/ScalarEvolutionExpander.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Target/TargetData.h"
+using namespace llvm;
+
+/// InsertCastOfTo - Insert a cast of V to the specified type, doing what
+/// we can to share the casts.
+Value *SCEVExpander::InsertCastOfTo(Instruction::CastOps opcode, Value *V, 
+                                    const Type *Ty) {
+  // Short-circuit unnecessary bitcasts.
+  if (opcode == Instruction::BitCast && V->getType() == Ty)
+    return V;
+
+  // Short-circuit unnecessary inttoptr<->ptrtoint casts.
+  if ((opcode == Instruction::PtrToInt || opcode == Instruction::IntToPtr) &&
+      SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(V->getType())) {
+    if (CastInst *CI = dyn_cast<CastInst>(V))
+      if ((CI->getOpcode() == Instruction::PtrToInt ||
+           CI->getOpcode() == Instruction::IntToPtr) &&
+          SE.getTypeSizeInBits(CI->getType()) ==
+          SE.getTypeSizeInBits(CI->getOperand(0)->getType()))
+        return CI->getOperand(0);
+    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
+      if ((CE->getOpcode() == Instruction::PtrToInt ||
+           CE->getOpcode() == Instruction::IntToPtr) &&
+          SE.getTypeSizeInBits(CE->getType()) ==
+          SE.getTypeSizeInBits(CE->getOperand(0)->getType()))
+        return CE->getOperand(0);
+  }
+
+  // FIXME: keep track of the cast instruction.
+  if (Constant *C = dyn_cast<Constant>(V))
+    return ConstantExpr::getCast(opcode, C, Ty);
+  
+  if (Argument *A = dyn_cast<Argument>(V)) {
+    // Check to see if there is already a cast!
+    for (Value::use_iterator UI = A->use_begin(), E = A->use_end();
+         UI != E; ++UI) {
+      if ((*UI)->getType() == Ty)
+        if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI)))
+          if (CI->getOpcode() == opcode) {
+            // If the cast isn't the first instruction of the function, move it.
+            if (BasicBlock::iterator(CI) != 
+                A->getParent()->getEntryBlock().begin()) {
+              // If the CastInst is the insert point, change the insert point.
+              if (CI == InsertPt) ++InsertPt;
+              // Splice the cast at the beginning of the entry block.
+              CI->moveBefore(A->getParent()->getEntryBlock().begin());
+            }
+            return CI;
+          }
+    }
+    Instruction *I = CastInst::Create(opcode, V, Ty, V->getName(),
+                                      A->getParent()->getEntryBlock().begin());
+    InsertedValues.insert(I);
+    return I;
+  }
+
+  Instruction *I = cast<Instruction>(V);
+
+  // Check to see if there is already a cast.  If there is, use it.
+  for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
+       UI != E; ++UI) {
+    if ((*UI)->getType() == Ty)
+      if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI)))
+        if (CI->getOpcode() == opcode) {
+          BasicBlock::iterator It = I; ++It;
+          if (isa<InvokeInst>(I))
+            It = cast<InvokeInst>(I)->getNormalDest()->begin();
+          while (isa<PHINode>(It)) ++It;
+          if (It != BasicBlock::iterator(CI)) {
+            // If the CastInst is the insert point, change the insert point.
+            if (CI == InsertPt) ++InsertPt;
+            // Splice the cast immediately after the operand in question.
+            CI->moveBefore(It);
+          }
+          return CI;
+        }
+  }
+  BasicBlock::iterator IP = I; ++IP;
+  if (InvokeInst *II = dyn_cast<InvokeInst>(I))
+    IP = II->getNormalDest()->begin();
+  while (isa<PHINode>(IP)) ++IP;
+  Instruction *CI = CastInst::Create(opcode, V, Ty, V->getName(), IP);
+  InsertedValues.insert(CI);
+  return CI;
+}
+
+/// InsertNoopCastOfTo - Insert a cast of V to the specified type,
+/// which must be possible with a noop cast.
+Value *SCEVExpander::InsertNoopCastOfTo(Value *V, const Type *Ty) {
+  Instruction::CastOps Op = CastInst::getCastOpcode(V, false, Ty, false);
+  assert((Op == Instruction::BitCast ||
+          Op == Instruction::PtrToInt ||
+          Op == Instruction::IntToPtr) &&
+         "InsertNoopCastOfTo cannot perform non-noop casts!");
+  assert(SE.getTypeSizeInBits(V->getType()) == SE.getTypeSizeInBits(Ty) &&
+         "InsertNoopCastOfTo cannot change sizes!");
+  return InsertCastOfTo(Op, V, Ty);
+}
+
+/// InsertBinop - Insert the specified binary operator, doing a small amount
+/// of work to avoid inserting an obviously redundant operation.
+Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode, Value *LHS,
+                                 Value *RHS, BasicBlock::iterator InsertPt) {
+  // Fold a binop with constant operands.
+  if (Constant *CLHS = dyn_cast<Constant>(LHS))
+    if (Constant *CRHS = dyn_cast<Constant>(RHS))
+      return ConstantExpr::get(Opcode, CLHS, CRHS);
+
+  // Do a quick scan to see if we have this binop nearby.  If so, reuse it.
+  unsigned ScanLimit = 6;
+  BasicBlock::iterator BlockBegin = InsertPt->getParent()->begin();
+  if (InsertPt != BlockBegin) {
+    // Scanning starts from the last instruction before InsertPt.
+    BasicBlock::iterator IP = InsertPt;
+    --IP;
+    for (; ScanLimit; --IP, --ScanLimit) {
+      if (IP->getOpcode() == (unsigned)Opcode && IP->getOperand(0) == LHS &&
+          IP->getOperand(1) == RHS)
+        return IP;
+      if (IP == BlockBegin) break;
+    }
+  }
+  
+  // If we haven't found this binop, insert it.
+  Instruction *BO = BinaryOperator::Create(Opcode, LHS, RHS, "tmp", InsertPt);
+  InsertedValues.insert(BO);
+  return BO;
+}
+
+/// FactorOutConstant - Test if S is divisible by Factor, using signed
+/// division. If so, update S with Factor divided out and return true.
+/// S need not be evenly divisble if a reasonable remainder can be
+/// computed.
+/// TODO: When ScalarEvolution gets a SCEVSDivExpr, this can be made
+/// unnecessary; in its place, just signed-divide Ops[i] by the scale and
+/// check to see if the divide was folded.
+static bool FactorOutConstant(SCEVHandle &S,
+                              SCEVHandle &Remainder,
+                              const APInt &Factor,
+                              ScalarEvolution &SE) {
+  // Everything is divisible by one.
+  if (Factor == 1)
+    return true;
+
+  // For a Constant, check for a multiple of the given factor.
+  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
+    ConstantInt *CI =
+      ConstantInt::get(C->getValue()->getValue().sdiv(Factor));
+    // If the quotient is zero and the remainder is non-zero, reject
+    // the value at this scale. It will be considered for subsequent
+    // smaller scales.
+    if (C->isZero() || !CI->isZero()) {
+      SCEVHandle Div = SE.getConstant(CI);
+      S = Div;
+      Remainder =
+        SE.getAddExpr(Remainder,
+                      SE.getConstant(C->getValue()->getValue().srem(Factor)));
+      return true;
+    }
+  }
+
+  // In a Mul, check if there is a constant operand which is a multiple
+  // of the given factor.
+  if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S))
+    if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0)))
+      if (!C->getValue()->getValue().srem(Factor)) {
+        std::vector<SCEVHandle> NewMulOps(M->getOperands());
+        NewMulOps[0] =
+          SE.getConstant(C->getValue()->getValue().sdiv(Factor));
+        S = SE.getMulExpr(NewMulOps);
+        return true;
+      }
+
+  // In an AddRec, check if both start and step are divisible.
+  if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
+    SCEVHandle Step = A->getStepRecurrence(SE);
+    SCEVHandle StepRem = SE.getIntegerSCEV(0, Step->getType());
+    if (!FactorOutConstant(Step, StepRem, Factor, SE))
+      return false;
+    if (!StepRem->isZero())
+      return false;
+    SCEVHandle Start = A->getStart();
+    if (!FactorOutConstant(Start, Remainder, Factor, SE))
+      return false;
+    S = SE.getAddRecExpr(Start, Step, A->getLoop());
+    return true;
+  }
+
+  return false;
+}
+
+/// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
+/// instead of using ptrtoint+arithmetic+inttoptr. This helps
+/// BasicAliasAnalysis analyze the result. However, it suffers from the
+/// underlying bug described in PR2831. Addition in LLVM currently always
+/// has two's complement wrapping guaranteed. However, the semantics for
+/// getelementptr overflow are ambiguous. In the common case though, this
+/// expansion gets used when a GEP in the original code has been converted
+/// into integer arithmetic, in which case the resulting code will be no
+/// more undefined than it was originally.
+///
+/// Design note: It might seem desirable for this function to be more
+/// loop-aware. If some of the indices are loop-invariant while others
+/// aren't, it might seem desirable to emit multiple GEPs, keeping the
+/// loop-invariant portions of the overall computation outside the loop.
+/// However, there are a few reasons this is not done here. Hoisting simple
+/// arithmetic is a low-level optimization that often isn't very
+/// important until late in the optimization process. In fact, passes
+/// like InstructionCombining will combine GEPs, even if it means
+/// pushing loop-invariant computation down into loops, so even if the
+/// GEPs were split here, the work would quickly be undone. The
+/// LoopStrengthReduction pass, which is usually run quite late (and
+/// after the last InstructionCombining pass), takes care of hoisting
+/// loop-invariant portions of expressions, after considering what
+/// can be folded using target addressing modes.
+///
+Value *SCEVExpander::expandAddToGEP(const SCEVHandle *op_begin,
+                                    const SCEVHandle *op_end,
+                                    const PointerType *PTy,
+                                    const Type *Ty,
+                                    Value *V) {
+  const Type *ElTy = PTy->getElementType();
+  SmallVector<Value *, 4> GepIndices;
+  std::vector<SCEVHandle> Ops(op_begin, op_end);
+  bool AnyNonZeroIndices = false;
+
+  // Decend down the pointer's type and attempt to convert the other
+  // operands into GEP indices, at each level. The first index in a GEP
+  // indexes into the array implied by the pointer operand; the rest of
+  // the indices index into the element or field type selected by the
+  // preceding index.
+  for (;;) {
+    APInt ElSize = APInt(SE.getTypeSizeInBits(Ty),
+                         ElTy->isSized() ?  SE.TD->getTypeAllocSize(ElTy) : 0);
+    std::vector<SCEVHandle> NewOps;
+    std::vector<SCEVHandle> ScaledOps;
+    for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
+      // Split AddRecs up into parts as either of the parts may be usable
+      // without the other.
+      if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Ops[i]))
+        if (!A->getStart()->isZero()) {
+          SCEVHandle Start = A->getStart();
+          Ops.push_back(SE.getAddRecExpr(SE.getIntegerSCEV(0, A->getType()),
+                                         A->getStepRecurrence(SE),
+                                         A->getLoop()));
+          Ops[i] = Start;
+          ++e;
+        }
+      // If the scale size is not 0, attempt to factor out a scale.
+      if (ElSize != 0) {
+        SCEVHandle Op = Ops[i];
+        SCEVHandle Remainder = SE.getIntegerSCEV(0, Op->getType());
+        if (FactorOutConstant(Op, Remainder, ElSize, SE)) {
+          ScaledOps.push_back(Op); // Op now has ElSize factored out.
+          NewOps.push_back(Remainder);
+          continue;
+        }
+      }
+      // If the operand was not divisible, add it to the list of operands
+      // we'll scan next iteration.
+      NewOps.push_back(Ops[i]);
+    }
+    Ops = NewOps;
+    AnyNonZeroIndices |= !ScaledOps.empty();
+    Value *Scaled = ScaledOps.empty() ?
+                    Constant::getNullValue(Ty) :
+                    expandCodeFor(SE.getAddExpr(ScaledOps), Ty);
+    GepIndices.push_back(Scaled);
+
+    // Collect struct field index operands.
+    if (!Ops.empty())
+      while (const StructType *STy = dyn_cast<StructType>(ElTy)) {
+        if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[0]))
+          if (SE.getTypeSizeInBits(C->getType()) <= 64) {
+            const StructLayout &SL = *SE.TD->getStructLayout(STy);
+            uint64_t FullOffset = C->getValue()->getZExtValue();
+            if (FullOffset < SL.getSizeInBytes()) {
+              unsigned ElIdx = SL.getElementContainingOffset(FullOffset);
+              GepIndices.push_back(ConstantInt::get(Type::Int32Ty, ElIdx));
+              ElTy = STy->getTypeAtIndex(ElIdx);
+              Ops[0] =
+                SE.getConstant(ConstantInt::get(Ty,
+                                                FullOffset -
+                                                  SL.getElementOffset(ElIdx)));
+              AnyNonZeroIndices = true;
+              continue;
+            }
+          }
+        break;
+      }
+
+    if (const ArrayType *ATy = dyn_cast<ArrayType>(ElTy)) {
+      ElTy = ATy->getElementType();
+      continue;
+    }
+    break;
+  }
+
+  // If none of the operands were convertable to proper GEP indices, cast
+  // the base to i8* and do an ugly getelementptr with that. It's still
+  // better than ptrtoint+arithmetic+inttoptr at least.
+  if (!AnyNonZeroIndices) {
+    V = InsertNoopCastOfTo(V,
+                           Type::Int8Ty->getPointerTo(PTy->getAddressSpace()));
+    Value *Idx = expand(SE.getAddExpr(Ops));
+    Idx = InsertNoopCastOfTo(Idx, Ty);
+
+    // Fold a GEP with constant operands.
+    if (Constant *CLHS = dyn_cast<Constant>(V))
+      if (Constant *CRHS = dyn_cast<Constant>(Idx))
+        return ConstantExpr::getGetElementPtr(CLHS, &CRHS, 1);
+
+    // Do a quick scan to see if we have this GEP nearby.  If so, reuse it.
+    unsigned ScanLimit = 6;
+    BasicBlock::iterator BlockBegin = InsertPt->getParent()->begin();
+    if (InsertPt != BlockBegin) {
+      // Scanning starts from the last instruction before InsertPt.
+      BasicBlock::iterator IP = InsertPt;
+      --IP;
+      for (; ScanLimit; --IP, --ScanLimit) {
+        if (IP->getOpcode() == Instruction::GetElementPtr &&
+            IP->getOperand(0) == V && IP->getOperand(1) == Idx)
+          return IP;
+        if (IP == BlockBegin) break;
+      }
+    }
+
+    Value *GEP = GetElementPtrInst::Create(V, Idx, "scevgep", InsertPt);
+    InsertedValues.insert(GEP);
+    return GEP;
+  }
+
+  // Insert a pretty getelementptr.
+  Value *GEP = GetElementPtrInst::Create(V,
+                                         GepIndices.begin(),
+                                         GepIndices.end(),
+                                         "scevgep", InsertPt);
+  Ops.push_back(SE.getUnknown(GEP));
+  InsertedValues.insert(GEP);
+  return expand(SE.getAddExpr(Ops));
+}
+
+Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) {
+  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
+  Value *V = expand(S->getOperand(S->getNumOperands()-1));
+
+  // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
+  // comments on expandAddToGEP for details.
+  if (SE.TD)
+    if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) {
+      const std::vector<SCEVHandle> &Ops = S->getOperands();
+      return expandAddToGEP(&Ops[0], &Ops[Ops.size() - 1],
+                            PTy, Ty, V);
+    }
+
+  V = InsertNoopCastOfTo(V, Ty);
+
+  // Emit a bunch of add instructions
+  for (int i = S->getNumOperands()-2; i >= 0; --i) {
+    Value *W = expand(S->getOperand(i));
+    W = InsertNoopCastOfTo(W, Ty);
+    V = InsertBinop(Instruction::Add, V, W, InsertPt);
+  }
+  return V;
+}
+
+Value *SCEVExpander::visitMulExpr(const SCEVMulExpr *S) {
+  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
+  int FirstOp = 0;  // Set if we should emit a subtract.
+  if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(0)))
+    if (SC->getValue()->isAllOnesValue())
+      FirstOp = 1;
+
+  int i = S->getNumOperands()-2;
+  Value *V = expand(S->getOperand(i+1));
+  V = InsertNoopCastOfTo(V, Ty);
+
+  // Emit a bunch of multiply instructions
+  for (; i >= FirstOp; --i) {
+    Value *W = expand(S->getOperand(i));
+    W = InsertNoopCastOfTo(W, Ty);
+    V = InsertBinop(Instruction::Mul, V, W, InsertPt);
+  }
+
+  // -1 * ...  --->  0 - ...
+  if (FirstOp == 1)
+    V = InsertBinop(Instruction::Sub, Constant::getNullValue(Ty), V, InsertPt);
+  return V;
+}
+
+Value *SCEVExpander::visitUDivExpr(const SCEVUDivExpr *S) {
+  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
+
+  Value *LHS = expand(S->getLHS());
+  LHS = InsertNoopCastOfTo(LHS, Ty);
+  if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getRHS())) {
+    const APInt &RHS = SC->getValue()->getValue();
+    if (RHS.isPowerOf2())
+      return InsertBinop(Instruction::LShr, LHS,
+                         ConstantInt::get(Ty, RHS.logBase2()),
+                         InsertPt);
+  }
+
+  Value *RHS = expand(S->getRHS());
+  RHS = InsertNoopCastOfTo(RHS, Ty);
+  return InsertBinop(Instruction::UDiv, LHS, RHS, InsertPt);
+}
+
+/// Move parts of Base into Rest to leave Base with the minimal
+/// expression that provides a pointer operand suitable for a
+/// GEP expansion.
+static void ExposePointerBase(SCEVHandle &Base, SCEVHandle &Rest,
+                              ScalarEvolution &SE) {
+  while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Base)) {
+    Base = A->getStart();
+    Rest = SE.getAddExpr(Rest,
+                         SE.getAddRecExpr(SE.getIntegerSCEV(0, A->getType()),
+                                          A->getStepRecurrence(SE),
+                                          A->getLoop()));
+  }
+  if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(Base)) {
+    Base = A->getOperand(A->getNumOperands()-1);
+    std::vector<SCEVHandle> NewAddOps(A->op_begin(), A->op_end());
+    NewAddOps.back() = Rest;
+    Rest = SE.getAddExpr(NewAddOps);
+    ExposePointerBase(Base, Rest, SE);
+  }
+}
+
+Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) {
+  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
+  const Loop *L = S->getLoop();
+
+  // {X,+,F} --> X + {0,+,F}
+  if (!S->getStart()->isZero()) {
+    std::vector<SCEVHandle> NewOps(S->getOperands());
+    NewOps[0] = SE.getIntegerSCEV(0, Ty);
+    SCEVHandle Rest = SE.getAddRecExpr(NewOps, L);
+
+    // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
+    // comments on expandAddToGEP for details.
+    if (SE.TD) {
+      SCEVHandle Base = S->getStart();
+      SCEVHandle RestArray[1] = { Rest };
+      // Dig into the expression to find the pointer base for a GEP.
+      ExposePointerBase(Base, RestArray[0], SE);
+      // If we found a pointer, expand the AddRec with a GEP.
+      if (const PointerType *PTy = dyn_cast<PointerType>(Base->getType())) {
+        // Make sure the Base isn't something exotic, such as a multiplied
+        // or divided pointer value. In those cases, the result type isn't
+        // actually a pointer type.
+        if (!isa<SCEVMulExpr>(Base) && !isa<SCEVUDivExpr>(Base)) {
+          Value *StartV = expand(Base);
+          assert(StartV->getType() == PTy && "Pointer type mismatch for GEP!");
+          return expandAddToGEP(RestArray, RestArray+1, PTy, Ty, StartV);
+        }
+      }
+    }
+
+    Value *RestV = expand(Rest);
+    return expand(SE.getAddExpr(S->getStart(), SE.getUnknown(RestV)));
+  }
+
+  // {0,+,1} --> Insert a canonical induction variable into the loop!
+  if (S->isAffine() &&
+      S->getOperand(1) == SE.getIntegerSCEV(1, Ty)) {
+    // Create and insert the PHI node for the induction variable in the
+    // specified loop.
+    BasicBlock *Header = L->getHeader();
+    PHINode *PN = PHINode::Create(Ty, "indvar", Header->begin());
+    InsertedValues.insert(PN);
+    PN->addIncoming(Constant::getNullValue(Ty), L->getLoopPreheader());
+
+    pred_iterator HPI = pred_begin(Header);
+    assert(HPI != pred_end(Header) && "Loop with zero preds???");
+    if (!L->contains(*HPI)) ++HPI;
+    assert(HPI != pred_end(Header) && L->contains(*HPI) &&
+           "No backedge in loop?");
+
+    // Insert a unit add instruction right before the terminator corresponding
+    // to the back-edge.
+    Constant *One = ConstantInt::get(Ty, 1);
+    Instruction *Add = BinaryOperator::CreateAdd(PN, One, "indvar.next",
+                                                 (*HPI)->getTerminator());
+    InsertedValues.insert(Add);
+
+    pred_iterator PI = pred_begin(Header);
+    if (*PI == L->getLoopPreheader())
+      ++PI;
+    PN->addIncoming(Add, *PI);
+    return PN;
+  }
+
+  // Get the canonical induction variable I for this loop.
+  Value *I = getOrInsertCanonicalInductionVariable(L, Ty);
+
+  // If this is a simple linear addrec, emit it now as a special case.
+  if (S->isAffine()) {   // {0,+,F} --> i*F
+    Value *F = expand(S->getOperand(1));
+    F = InsertNoopCastOfTo(F, Ty);
+    
+    // IF the step is by one, just return the inserted IV.
+    if (ConstantInt *CI = dyn_cast<ConstantInt>(F))
+      if (CI->getValue() == 1)
+        return I;
+    
+    // If the insert point is directly inside of the loop, emit the multiply at
+    // the insert point.  Otherwise, L is a loop that is a parent of the insert
+    // point loop.  If we can, move the multiply to the outer most loop that it
+    // is safe to be in.
+    BasicBlock::iterator MulInsertPt = getInsertionPoint();
+    Loop *InsertPtLoop = SE.LI->getLoopFor(MulInsertPt->getParent());
+    if (InsertPtLoop != L && InsertPtLoop &&
+        L->contains(InsertPtLoop->getHeader())) {
+      do {
+        // If we cannot hoist the multiply out of this loop, don't.
+        if (!InsertPtLoop->isLoopInvariant(F)) break;
+
+        BasicBlock *InsertPtLoopPH = InsertPtLoop->getLoopPreheader();
+
+        // If this loop hasn't got a preheader, we aren't able to hoist the
+        // multiply.
+        if (!InsertPtLoopPH)
+          break;
+
+        // Otherwise, move the insert point to the preheader.
+        MulInsertPt = InsertPtLoopPH->getTerminator();
+        InsertPtLoop = InsertPtLoop->getParentLoop();
+      } while (InsertPtLoop != L);
+    }
+    
+    return InsertBinop(Instruction::Mul, I, F, MulInsertPt);
+  }
+
+  // If this is a chain of recurrences, turn it into a closed form, using the
+  // folders, then expandCodeFor the closed form.  This allows the folders to
+  // simplify the expression without having to build a bunch of special code
+  // into this folder.
+  SCEVHandle IH = SE.getUnknown(I);   // Get I as a "symbolic" SCEV.
+
+  SCEVHandle V = S->evaluateAtIteration(IH, SE);
+  //cerr << "Evaluated: " << *this << "\n     to: " << *V << "\n";
+
+  return expand(V);
+}
+
+Value *SCEVExpander::visitTruncateExpr(const SCEVTruncateExpr *S) {
+  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
+  Value *V = expand(S->getOperand());
+  V = InsertNoopCastOfTo(V, SE.getEffectiveSCEVType(V->getType()));
+  Instruction *I = new TruncInst(V, Ty, "tmp.", InsertPt);
+  InsertedValues.insert(I);
+  return I;
+}
+
+Value *SCEVExpander::visitZeroExtendExpr(const SCEVZeroExtendExpr *S) {
+  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
+  Value *V = expand(S->getOperand());
+  V = InsertNoopCastOfTo(V, SE.getEffectiveSCEVType(V->getType()));
+  Instruction *I = new ZExtInst(V, Ty, "tmp.", InsertPt);
+  InsertedValues.insert(I);
+  return I;
+}
+
+Value *SCEVExpander::visitSignExtendExpr(const SCEVSignExtendExpr *S) {
+  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
+  Value *V = expand(S->getOperand());
+  V = InsertNoopCastOfTo(V, SE.getEffectiveSCEVType(V->getType()));
+  Instruction *I = new SExtInst(V, Ty, "tmp.", InsertPt);
+  InsertedValues.insert(I);
+  return I;
+}
+
+Value *SCEVExpander::visitSMaxExpr(const SCEVSMaxExpr *S) {
+  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
+  Value *LHS = expand(S->getOperand(0));
+  LHS = InsertNoopCastOfTo(LHS, Ty);
+  for (unsigned i = 1; i < S->getNumOperands(); ++i) {
+    Value *RHS = expand(S->getOperand(i));
+    RHS = InsertNoopCastOfTo(RHS, Ty);
+    Instruction *ICmp =
+      new ICmpInst(ICmpInst::ICMP_SGT, LHS, RHS, "tmp", InsertPt);
+    InsertedValues.insert(ICmp);
+    Instruction *Sel = SelectInst::Create(ICmp, LHS, RHS, "smax", InsertPt);
+    InsertedValues.insert(Sel);
+    LHS = Sel;
+  }
+  return LHS;
+}
+
+Value *SCEVExpander::visitUMaxExpr(const SCEVUMaxExpr *S) {
+  const Type *Ty = SE.getEffectiveSCEVType(S->getType());
+  Value *LHS = expand(S->getOperand(0));
+  LHS = InsertNoopCastOfTo(LHS, Ty);
+  for (unsigned i = 1; i < S->getNumOperands(); ++i) {
+    Value *RHS = expand(S->getOperand(i));
+    RHS = InsertNoopCastOfTo(RHS, Ty);
+    Instruction *ICmp =
+      new ICmpInst(ICmpInst::ICMP_UGT, LHS, RHS, "tmp", InsertPt);
+    InsertedValues.insert(ICmp);
+    Instruction *Sel = SelectInst::Create(ICmp, LHS, RHS, "umax", InsertPt);
+    InsertedValues.insert(Sel);
+    LHS = Sel;
+  }
+  return LHS;
+}
+
+Value *SCEVExpander::expandCodeFor(SCEVHandle SH, const Type *Ty) {
+  // Expand the code for this SCEV.
+  Value *V = expand(SH);
+  if (Ty) {
+    assert(SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(SH->getType()) &&
+           "non-trivial casts should be done with the SCEVs directly!");
+    V = InsertNoopCastOfTo(V, Ty);
+  }
+  return V;
+}
+
+Value *SCEVExpander::expand(const SCEV *S) {
+  // Check to see if we already expanded this.
+  std::map<SCEVHandle, AssertingVH<Value> >::iterator I =
+    InsertedExpressions.find(S);
+  if (I != InsertedExpressions.end())
+    return I->second;
+  
+  Value *V = visit(S);
+  InsertedExpressions[S] = V;
+  return V;
+}