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diff --git a/contrib/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp b/contrib/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
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+//===- TailRecursionElimination.cpp - Eliminate Tail Calls ----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file transforms calls of the current function (self recursion) followed
+// by a return instruction with a branch to the entry of the function, creating
+// a loop.  This pass also implements the following extensions to the basic
+// algorithm:
+//
+//  1. Trivial instructions between the call and return do not prevent the
+//     transformation from taking place, though currently the analysis cannot
+//     support moving any really useful instructions (only dead ones).
+//  2. This pass transforms functions that are prevented from being tail
+//     recursive by an associative expression to use an accumulator variable,
+//     thus compiling the typical naive factorial or 'fib' implementation into
+//     efficient code.
+//  3. TRE is performed if the function returns void, if the return
+//     returns the result returned by the call, or if the function returns a
+//     run-time constant on all exits from the function.  It is possible, though
+//     unlikely, that the return returns something else (like constant 0), and
+//     can still be TRE'd.  It can be TRE'd if ALL OTHER return instructions in
+//     the function return the exact same value.
+//  4. If it can prove that callees do not access their caller stack frame,
+//     they are marked as eligible for tail call elimination (by the code
+//     generator).
+//
+// There are several improvements that could be made:
+//
+//  1. If the function has any alloca instructions, these instructions will be
+//     moved out of the entry block of the function, causing them to be
+//     evaluated each time through the tail recursion.  Safely keeping allocas
+//     in the entry block requires analysis to proves that the tail-called
+//     function does not read or write the stack object.
+//  2. Tail recursion is only performed if the call immediately preceeds the
+//     return instruction.  It's possible that there could be a jump between
+//     the call and the return.
+//  3. There can be intervening operations between the call and the return that
+//     prevent the TRE from occurring.  For example, there could be GEP's and
+//     stores to memory that will not be read or written by the call.  This
+//     requires some substantial analysis (such as with DSA) to prove safe to
+//     move ahead of the call, but doing so could allow many more TREs to be
+//     performed, for example in TreeAdd/TreeAlloc from the treeadd benchmark.
+//  4. The algorithm we use to detect if callees access their caller stack
+//     frames is very primitive.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "tailcallelim"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Function.h"
+#include "llvm/Instructions.h"
+#include "llvm/Pass.h"
+#include "llvm/Analysis/CaptureTracking.h"
+#include "llvm/Analysis/InlineCost.h"
+#include "llvm/Support/CallSite.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/ADT/Statistic.h"
+using namespace llvm;
+
+STATISTIC(NumEliminated, "Number of tail calls removed");
+STATISTIC(NumAccumAdded, "Number of accumulators introduced");
+
+namespace {
+  struct TailCallElim : public FunctionPass {
+    static char ID; // Pass identification, replacement for typeid
+    TailCallElim() : FunctionPass(&ID) {}
+
+    virtual bool runOnFunction(Function &F);
+
+  private:
+    bool ProcessReturningBlock(ReturnInst *RI, BasicBlock *&OldEntry,
+                               bool &TailCallsAreMarkedTail,
+                               SmallVector<PHINode*, 8> &ArgumentPHIs,
+                               bool CannotTailCallElimCallsMarkedTail);
+    bool CanMoveAboveCall(Instruction *I, CallInst *CI);
+    Value *CanTransformAccumulatorRecursion(Instruction *I, CallInst *CI);
+  };
+}
+
+char TailCallElim::ID = 0;
+static RegisterPass<TailCallElim> X("tailcallelim", "Tail Call Elimination");
+
+// Public interface to the TailCallElimination pass
+FunctionPass *llvm::createTailCallEliminationPass() {
+  return new TailCallElim();
+}
+
+/// AllocaMightEscapeToCalls - Return true if this alloca may be accessed by
+/// callees of this function.  We only do very simple analysis right now, this
+/// could be expanded in the future to use mod/ref information for particular
+/// call sites if desired.
+static bool AllocaMightEscapeToCalls(AllocaInst *AI) {
+  // FIXME: do simple 'address taken' analysis.
+  return true;
+}
+
+/// CheckForEscapingAllocas - Scan the specified basic block for alloca
+/// instructions.  If it contains any that might be accessed by calls, return
+/// true.
+static bool CheckForEscapingAllocas(BasicBlock *BB,
+                                    bool &CannotTCETailMarkedCall) {
+  bool RetVal = false;
+  for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
+    if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
+      RetVal |= AllocaMightEscapeToCalls(AI);
+
+      // If this alloca is in the body of the function, or if it is a variable
+      // sized allocation, we cannot tail call eliminate calls marked 'tail'
+      // with this mechanism.
+      if (BB != &BB->getParent()->getEntryBlock() ||
+          !isa<ConstantInt>(AI->getArraySize()))
+        CannotTCETailMarkedCall = true;
+    }
+  return RetVal;
+}
+
+bool TailCallElim::runOnFunction(Function &F) {
+  // If this function is a varargs function, we won't be able to PHI the args
+  // right, so don't even try to convert it...
+  if (F.getFunctionType()->isVarArg()) return false;
+
+  BasicBlock *OldEntry = 0;
+  bool TailCallsAreMarkedTail = false;
+  SmallVector<PHINode*, 8> ArgumentPHIs;
+  bool MadeChange = false;
+
+  bool FunctionContainsEscapingAllocas = false;
+
+  // CannotTCETailMarkedCall - If true, we cannot perform TCE on tail calls
+  // marked with the 'tail' attribute, because doing so would cause the stack
+  // size to increase (real TCE would deallocate variable sized allocas, TCE
+  // doesn't).
+  bool CannotTCETailMarkedCall = false;
+
+  // Loop over the function, looking for any returning blocks, and keeping track
+  // of whether this function has any non-trivially used allocas.
+  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
+    if (FunctionContainsEscapingAllocas && CannotTCETailMarkedCall)
+      break;
+
+    FunctionContainsEscapingAllocas |=
+      CheckForEscapingAllocas(BB, CannotTCETailMarkedCall);
+  }
+  
+  /// FIXME: The code generator produces really bad code when an 'escaping
+  /// alloca' is changed from being a static alloca to being a dynamic alloca.
+  /// Until this is resolved, disable this transformation if that would ever
+  /// happen.  This bug is PR962.
+  if (FunctionContainsEscapingAllocas)
+    return false;
+
+  // Second pass, change any tail calls to loops.
+  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+    if (ReturnInst *Ret = dyn_cast<ReturnInst>(BB->getTerminator()))
+      MadeChange |= ProcessReturningBlock(Ret, OldEntry, TailCallsAreMarkedTail,
+                                          ArgumentPHIs,CannotTCETailMarkedCall);
+
+  // If we eliminated any tail recursions, it's possible that we inserted some
+  // silly PHI nodes which just merge an initial value (the incoming operand)
+  // with themselves.  Check to see if we did and clean up our mess if so.  This
+  // occurs when a function passes an argument straight through to its tail
+  // call.
+  if (!ArgumentPHIs.empty()) {
+    for (unsigned i = 0, e = ArgumentPHIs.size(); i != e; ++i) {
+      PHINode *PN = ArgumentPHIs[i];
+
+      // If the PHI Node is a dynamic constant, replace it with the value it is.
+      if (Value *PNV = PN->hasConstantValue()) {
+        PN->replaceAllUsesWith(PNV);
+        PN->eraseFromParent();
+      }
+    }
+  }
+
+  // Finally, if this function contains no non-escaping allocas, mark all calls
+  // in the function as eligible for tail calls (there is no stack memory for
+  // them to access).
+  if (!FunctionContainsEscapingAllocas)
+    for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+      for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
+        if (CallInst *CI = dyn_cast<CallInst>(I)) {
+          CI->setTailCall();
+          MadeChange = true;
+        }
+
+  return MadeChange;
+}
+
+
+/// CanMoveAboveCall - Return true if it is safe to move the specified
+/// instruction from after the call to before the call, assuming that all
+/// instructions between the call and this instruction are movable.
+///
+bool TailCallElim::CanMoveAboveCall(Instruction *I, CallInst *CI) {
+  // FIXME: We can move load/store/call/free instructions above the call if the
+  // call does not mod/ref the memory location being processed.
+  if (I->mayHaveSideEffects())  // This also handles volatile loads.
+    return false;
+  
+  if (LoadInst *L = dyn_cast<LoadInst>(I)) {
+    // Loads may always be moved above calls without side effects.
+    if (CI->mayHaveSideEffects()) {
+      // Non-volatile loads may be moved above a call with side effects if it
+      // does not write to memory and the load provably won't trap.
+      // FIXME: Writes to memory only matter if they may alias the pointer
+      // being loaded from.
+      if (CI->mayWriteToMemory() ||
+          !isSafeToLoadUnconditionally(L->getPointerOperand(), L,
+                                       L->getAlignment()))
+        return false;
+    }
+  }
+
+  // Otherwise, if this is a side-effect free instruction, check to make sure
+  // that it does not use the return value of the call.  If it doesn't use the
+  // return value of the call, it must only use things that are defined before
+  // the call, or movable instructions between the call and the instruction
+  // itself.
+  for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
+    if (I->getOperand(i) == CI)
+      return false;
+  return true;
+}
+
+// isDynamicConstant - Return true if the specified value is the same when the
+// return would exit as it was when the initial iteration of the recursive
+// function was executed.
+//
+// We currently handle static constants and arguments that are not modified as
+// part of the recursion.
+//
+static bool isDynamicConstant(Value *V, CallInst *CI, ReturnInst *RI) {
+  if (isa<Constant>(V)) return true; // Static constants are always dyn consts
+
+  // Check to see if this is an immutable argument, if so, the value
+  // will be available to initialize the accumulator.
+  if (Argument *Arg = dyn_cast<Argument>(V)) {
+    // Figure out which argument number this is...
+    unsigned ArgNo = 0;
+    Function *F = CI->getParent()->getParent();
+    for (Function::arg_iterator AI = F->arg_begin(); &*AI != Arg; ++AI)
+      ++ArgNo;
+
+    // If we are passing this argument into call as the corresponding
+    // argument operand, then the argument is dynamically constant.
+    // Otherwise, we cannot transform this function safely.
+    if (CI->getOperand(ArgNo+1) == Arg)
+      return true;
+  }
+
+  // Switch cases are always constant integers. If the value is being switched
+  // on and the return is only reachable from one of its cases, it's
+  // effectively constant.
+  if (BasicBlock *UniquePred = RI->getParent()->getUniquePredecessor())
+    if (SwitchInst *SI = dyn_cast<SwitchInst>(UniquePred->getTerminator()))
+      if (SI->getCondition() == V)
+        return SI->getDefaultDest() != RI->getParent();
+
+  // Not a constant or immutable argument, we can't safely transform.
+  return false;
+}
+
+// getCommonReturnValue - Check to see if the function containing the specified
+// return instruction and tail call consistently returns the same
+// runtime-constant value at all exit points.  If so, return the returned value.
+//
+static Value *getCommonReturnValue(ReturnInst *TheRI, CallInst *CI) {
+  Function *F = TheRI->getParent()->getParent();
+  Value *ReturnedValue = 0;
+
+  for (Function::iterator BBI = F->begin(), E = F->end(); BBI != E; ++BBI)
+    if (ReturnInst *RI = dyn_cast<ReturnInst>(BBI->getTerminator()))
+      if (RI != TheRI) {
+        Value *RetOp = RI->getOperand(0);
+
+        // We can only perform this transformation if the value returned is
+        // evaluatable at the start of the initial invocation of the function,
+        // instead of at the end of the evaluation.
+        //
+        if (!isDynamicConstant(RetOp, CI, RI))
+          return 0;
+
+        if (ReturnedValue && RetOp != ReturnedValue)
+          return 0;     // Cannot transform if differing values are returned.
+        ReturnedValue = RetOp;
+      }
+  return ReturnedValue;
+}
+
+/// CanTransformAccumulatorRecursion - If the specified instruction can be
+/// transformed using accumulator recursion elimination, return the constant
+/// which is the start of the accumulator value.  Otherwise return null.
+///
+Value *TailCallElim::CanTransformAccumulatorRecursion(Instruction *I,
+                                                      CallInst *CI) {
+  if (!I->isAssociative()) return 0;
+  assert(I->getNumOperands() == 2 &&
+         "Associative operations should have 2 args!");
+
+  // Exactly one operand should be the result of the call instruction...
+  if ((I->getOperand(0) == CI && I->getOperand(1) == CI) ||
+      (I->getOperand(0) != CI && I->getOperand(1) != CI))
+    return 0;
+
+  // The only user of this instruction we allow is a single return instruction.
+  if (!I->hasOneUse() || !isa<ReturnInst>(I->use_back()))
+    return 0;
+
+  // Ok, now we have to check all of the other return instructions in this
+  // function.  If they return non-constants or differing values, then we cannot
+  // transform the function safely.
+  return getCommonReturnValue(cast<ReturnInst>(I->use_back()), CI);
+}
+
+bool TailCallElim::ProcessReturningBlock(ReturnInst *Ret, BasicBlock *&OldEntry,
+                                         bool &TailCallsAreMarkedTail,
+                                         SmallVector<PHINode*, 8> &ArgumentPHIs,
+                                       bool CannotTailCallElimCallsMarkedTail) {
+  BasicBlock *BB = Ret->getParent();
+  Function *F = BB->getParent();
+
+  if (&BB->front() == Ret) // Make sure there is something before the ret...
+    return false;
+  
+  // Scan backwards from the return, checking to see if there is a tail call in
+  // this block.  If so, set CI to it.
+  CallInst *CI;
+  BasicBlock::iterator BBI = Ret;
+  while (1) {
+    CI = dyn_cast<CallInst>(BBI);
+    if (CI && CI->getCalledFunction() == F)
+      break;
+
+    if (BBI == BB->begin())
+      return false;          // Didn't find a potential tail call.
+    --BBI;
+  }
+
+  // If this call is marked as a tail call, and if there are dynamic allocas in
+  // the function, we cannot perform this optimization.
+  if (CI->isTailCall() && CannotTailCallElimCallsMarkedTail)
+    return false;
+
+  // As a special case, detect code like this:
+  //   double fabs(double f) { return __builtin_fabs(f); } // a 'fabs' call
+  // and disable this xform in this case, because the code generator will
+  // lower the call to fabs into inline code.
+  if (BB == &F->getEntryBlock() && 
+      &BB->front() == CI && &*++BB->begin() == Ret &&
+      callIsSmall(F)) {
+    // A single-block function with just a call and a return. Check that
+    // the arguments match.
+    CallSite::arg_iterator I = CallSite(CI).arg_begin(),
+                           E = CallSite(CI).arg_end();
+    Function::arg_iterator FI = F->arg_begin(),
+                           FE = F->arg_end();
+    for (; I != E && FI != FE; ++I, ++FI)
+      if (*I != &*FI) break;
+    if (I == E && FI == FE)
+      return false;
+  }
+
+  // If we are introducing accumulator recursion to eliminate associative
+  // operations after the call instruction, this variable contains the initial
+  // value for the accumulator.  If this value is set, we actually perform
+  // accumulator recursion elimination instead of simple tail recursion
+  // elimination.
+  Value *AccumulatorRecursionEliminationInitVal = 0;
+  Instruction *AccumulatorRecursionInstr = 0;
+
+  // Ok, we found a potential tail call.  We can currently only transform the
+  // tail call if all of the instructions between the call and the return are
+  // movable to above the call itself, leaving the call next to the return.
+  // Check that this is the case now.
+  for (BBI = CI, ++BBI; &*BBI != Ret; ++BBI)
+    if (!CanMoveAboveCall(BBI, CI)) {
+      // If we can't move the instruction above the call, it might be because it
+      // is an associative operation that could be tranformed using accumulator
+      // recursion elimination.  Check to see if this is the case, and if so,
+      // remember the initial accumulator value for later.
+      if ((AccumulatorRecursionEliminationInitVal =
+                             CanTransformAccumulatorRecursion(BBI, CI))) {
+        // Yes, this is accumulator recursion.  Remember which instruction
+        // accumulates.
+        AccumulatorRecursionInstr = BBI;
+      } else {
+        return false;   // Otherwise, we cannot eliminate the tail recursion!
+      }
+    }
+
+  // We can only transform call/return pairs that either ignore the return value
+  // of the call and return void, ignore the value of the call and return a
+  // constant, return the value returned by the tail call, or that are being
+  // accumulator recursion variable eliminated.
+  if (Ret->getNumOperands() == 1 && Ret->getReturnValue() != CI &&
+      !isa<UndefValue>(Ret->getReturnValue()) &&
+      AccumulatorRecursionEliminationInitVal == 0 &&
+      !getCommonReturnValue(Ret, CI))
+    return false;
+
+  // OK! We can transform this tail call.  If this is the first one found,
+  // create the new entry block, allowing us to branch back to the old entry.
+  if (OldEntry == 0) {
+    OldEntry = &F->getEntryBlock();
+    BasicBlock *NewEntry = BasicBlock::Create(F->getContext(), "", F, OldEntry);
+    NewEntry->takeName(OldEntry);
+    OldEntry->setName("tailrecurse");
+    BranchInst::Create(OldEntry, NewEntry);
+
+    // If this tail call is marked 'tail' and if there are any allocas in the
+    // entry block, move them up to the new entry block.
+    TailCallsAreMarkedTail = CI->isTailCall();
+    if (TailCallsAreMarkedTail)
+      // Move all fixed sized allocas from OldEntry to NewEntry.
+      for (BasicBlock::iterator OEBI = OldEntry->begin(), E = OldEntry->end(),
+             NEBI = NewEntry->begin(); OEBI != E; )
+        if (AllocaInst *AI = dyn_cast<AllocaInst>(OEBI++))
+          if (isa<ConstantInt>(AI->getArraySize()))
+            AI->moveBefore(NEBI);
+
+    // Now that we have created a new block, which jumps to the entry
+    // block, insert a PHI node for each argument of the function.
+    // For now, we initialize each PHI to only have the real arguments
+    // which are passed in.
+    Instruction *InsertPos = OldEntry->begin();
+    for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
+         I != E; ++I) {
+      PHINode *PN = PHINode::Create(I->getType(),
+                                    I->getName() + ".tr", InsertPos);
+      I->replaceAllUsesWith(PN); // Everyone use the PHI node now!
+      PN->addIncoming(I, NewEntry);
+      ArgumentPHIs.push_back(PN);
+    }
+  }
+
+  // If this function has self recursive calls in the tail position where some
+  // are marked tail and some are not, only transform one flavor or another.  We
+  // have to choose whether we move allocas in the entry block to the new entry
+  // block or not, so we can't make a good choice for both.  NOTE: We could do
+  // slightly better here in the case that the function has no entry block
+  // allocas.
+  if (TailCallsAreMarkedTail && !CI->isTailCall())
+    return false;
+
+  // Ok, now that we know we have a pseudo-entry block WITH all of the
+  // required PHI nodes, add entries into the PHI node for the actual
+  // parameters passed into the tail-recursive call.
+  for (unsigned i = 0, e = CI->getNumOperands()-1; i != e; ++i)
+    ArgumentPHIs[i]->addIncoming(CI->getOperand(i+1), BB);
+
+  // If we are introducing an accumulator variable to eliminate the recursion,
+  // do so now.  Note that we _know_ that no subsequent tail recursion
+  // eliminations will happen on this function because of the way the
+  // accumulator recursion predicate is set up.
+  //
+  if (AccumulatorRecursionEliminationInitVal) {
+    Instruction *AccRecInstr = AccumulatorRecursionInstr;
+    // Start by inserting a new PHI node for the accumulator.
+    PHINode *AccPN = PHINode::Create(AccRecInstr->getType(), "accumulator.tr",
+                                     OldEntry->begin());
+
+    // Loop over all of the predecessors of the tail recursion block.  For the
+    // real entry into the function we seed the PHI with the initial value,
+    // computed earlier.  For any other existing branches to this block (due to
+    // other tail recursions eliminated) the accumulator is not modified.
+    // Because we haven't added the branch in the current block to OldEntry yet,
+    // it will not show up as a predecessor.
+    for (pred_iterator PI = pred_begin(OldEntry), PE = pred_end(OldEntry);
+         PI != PE; ++PI) {
+      if (*PI == &F->getEntryBlock())
+        AccPN->addIncoming(AccumulatorRecursionEliminationInitVal, *PI);
+      else
+        AccPN->addIncoming(AccPN, *PI);
+    }
+
+    // Add an incoming argument for the current block, which is computed by our
+    // associative accumulator instruction.
+    AccPN->addIncoming(AccRecInstr, BB);
+
+    // Next, rewrite the accumulator recursion instruction so that it does not
+    // use the result of the call anymore, instead, use the PHI node we just
+    // inserted.
+    AccRecInstr->setOperand(AccRecInstr->getOperand(0) != CI, AccPN);
+
+    // Finally, rewrite any return instructions in the program to return the PHI
+    // node instead of the "initval" that they do currently.  This loop will
+    // actually rewrite the return value we are destroying, but that's ok.
+    for (Function::iterator BBI = F->begin(), E = F->end(); BBI != E; ++BBI)
+      if (ReturnInst *RI = dyn_cast<ReturnInst>(BBI->getTerminator()))
+        RI->setOperand(0, AccPN);
+    ++NumAccumAdded;
+  }
+
+  // Now that all of the PHI nodes are in place, remove the call and
+  // ret instructions, replacing them with an unconditional branch.
+  BranchInst::Create(OldEntry, Ret);
+  BB->getInstList().erase(Ret);  // Remove return.
+  BB->getInstList().erase(CI);   // Remove call.
+  ++NumEliminated;
+  return true;
+}