vendor/llvm/llvm-r72732

1 files changed, 746 insertions, 0 deletions

diff --git a/lib/Transforms/Utils/CodeExtractor.cpp b/lib/Transforms/Utils/CodeExtractor.cpp
new file mode 100644
index 000000000000..6d5904e30886
--- /dev/null
+++ b/lib/Transforms/Utils/CodeExtractor.cpp
@@ -0,0 +1,746 @@
+//===- CodeExtractor.cpp - Pull code region into a new function -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the interface to tear out a code region, such as an
+// individual loop or a parallel section, into a new function, replacing it with
+// a call to the new function.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/FunctionUtils.h"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Instructions.h"
+#include "llvm/Intrinsics.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/StringExtras.h"
+#include <algorithm>
+#include <set>
+using namespace llvm;
+
+// Provide a command-line option to aggregate function arguments into a struct
+// for functions produced by the code extractor. This is useful when converting
+// extracted functions to pthread-based code, as only one argument (void*) can
+// be passed in to pthread_create().
+static cl::opt<bool>
+AggregateArgsOpt("aggregate-extracted-args", cl::Hidden,
+                 cl::desc("Aggregate arguments to code-extracted functions"));
+
+namespace {
+  class VISIBILITY_HIDDEN CodeExtractor {
+    typedef std::vector<Value*> Values;
+    std::set<BasicBlock*> BlocksToExtract;
+    DominatorTree* DT;
+    bool AggregateArgs;
+    unsigned NumExitBlocks;
+    const Type *RetTy;
+  public:
+    CodeExtractor(DominatorTree* dt = 0, bool AggArgs = false)
+      : DT(dt), AggregateArgs(AggArgs||AggregateArgsOpt), NumExitBlocks(~0U) {}
+
+    Function *ExtractCodeRegion(const std::vector<BasicBlock*> &code);
+
+    bool isEligible(const std::vector<BasicBlock*> &code);
+
+  private:
+    /// definedInRegion - Return true if the specified value is defined in the
+    /// extracted region.
+    bool definedInRegion(Value *V) const {
+      if (Instruction *I = dyn_cast<Instruction>(V))
+        if (BlocksToExtract.count(I->getParent()))
+          return true;
+      return false;
+    }
+
+    /// definedInCaller - Return true if the specified value is defined in the
+    /// function being code extracted, but not in the region being extracted.
+    /// These values must be passed in as live-ins to the function.
+    bool definedInCaller(Value *V) const {
+      if (isa<Argument>(V)) return true;
+      if (Instruction *I = dyn_cast<Instruction>(V))
+        if (!BlocksToExtract.count(I->getParent()))
+          return true;
+      return false;
+    }
+
+    void severSplitPHINodes(BasicBlock *&Header);
+    void splitReturnBlocks();
+    void findInputsOutputs(Values &inputs, Values &outputs);
+
+    Function *constructFunction(const Values &inputs,
+                                const Values &outputs,
+                                BasicBlock *header,
+                                BasicBlock *newRootNode, BasicBlock *newHeader,
+                                Function *oldFunction, Module *M);
+
+    void moveCodeToFunction(Function *newFunction);
+
+    void emitCallAndSwitchStatement(Function *newFunction,
+                                    BasicBlock *newHeader,
+                                    Values &inputs,
+                                    Values &outputs);
+
+  };
+}
+
+/// severSplitPHINodes - If a PHI node has multiple inputs from outside of the
+/// region, we need to split the entry block of the region so that the PHI node
+/// is easier to deal with.
+void CodeExtractor::severSplitPHINodes(BasicBlock *&Header) {
+  bool HasPredsFromRegion = false;
+  unsigned NumPredsOutsideRegion = 0;
+
+  if (Header != &Header->getParent()->getEntryBlock()) {
+    PHINode *PN = dyn_cast<PHINode>(Header->begin());
+    if (!PN) return;  // No PHI nodes.
+
+    // If the header node contains any PHI nodes, check to see if there is more
+    // than one entry from outside the region.  If so, we need to sever the
+    // header block into two.
+    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+      if (BlocksToExtract.count(PN->getIncomingBlock(i)))
+        HasPredsFromRegion = true;
+      else
+        ++NumPredsOutsideRegion;
+
+    // If there is one (or fewer) predecessor from outside the region, we don't
+    // need to do anything special.
+    if (NumPredsOutsideRegion <= 1) return;
+  }
+
+  // Otherwise, we need to split the header block into two pieces: one
+  // containing PHI nodes merging values from outside of the region, and a
+  // second that contains all of the code for the block and merges back any
+  // incoming values from inside of the region.
+  BasicBlock::iterator AfterPHIs = Header->getFirstNonPHI();
+  BasicBlock *NewBB = Header->splitBasicBlock(AfterPHIs,
+                                              Header->getName()+".ce");
+
+  // We only want to code extract the second block now, and it becomes the new
+  // header of the region.
+  BasicBlock *OldPred = Header;
+  BlocksToExtract.erase(OldPred);
+  BlocksToExtract.insert(NewBB);
+  Header = NewBB;
+
+  // Okay, update dominator sets. The blocks that dominate the new one are the
+  // blocks that dominate TIBB plus the new block itself.
+  if (DT)
+    DT->splitBlock(NewBB);
+
+  // Okay, now we need to adjust the PHI nodes and any branches from within the
+  // region to go to the new header block instead of the old header block.
+  if (HasPredsFromRegion) {
+    PHINode *PN = cast<PHINode>(OldPred->begin());
+    // Loop over all of the predecessors of OldPred that are in the region,
+    // changing them to branch to NewBB instead.
+    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+      if (BlocksToExtract.count(PN->getIncomingBlock(i))) {
+        TerminatorInst *TI = PN->getIncomingBlock(i)->getTerminator();
+        TI->replaceUsesOfWith(OldPred, NewBB);
+      }
+
+    // Okay, everthing within the region is now branching to the right block, we
+    // just have to update the PHI nodes now, inserting PHI nodes into NewBB.
+    for (AfterPHIs = OldPred->begin(); isa<PHINode>(AfterPHIs); ++AfterPHIs) {
+      PHINode *PN = cast<PHINode>(AfterPHIs);
+      // Create a new PHI node in the new region, which has an incoming value
+      // from OldPred of PN.
+      PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".ce",
+                                       NewBB->begin());
+      NewPN->addIncoming(PN, OldPred);
+
+      // Loop over all of the incoming value in PN, moving them to NewPN if they
+      // are from the extracted region.
+      for (unsigned i = 0; i != PN->getNumIncomingValues(); ++i) {
+        if (BlocksToExtract.count(PN->getIncomingBlock(i))) {
+          NewPN->addIncoming(PN->getIncomingValue(i), PN->getIncomingBlock(i));
+          PN->removeIncomingValue(i);
+          --i;
+        }
+      }
+    }
+  }
+}
+
+void CodeExtractor::splitReturnBlocks() {
+  for (std::set<BasicBlock*>::iterator I = BlocksToExtract.begin(),
+         E = BlocksToExtract.end(); I != E; ++I)
+    if (ReturnInst *RI = dyn_cast<ReturnInst>((*I)->getTerminator()))
+      (*I)->splitBasicBlock(RI, (*I)->getName()+".ret");
+}
+
+// findInputsOutputs - Find inputs to, outputs from the code region.
+//
+void CodeExtractor::findInputsOutputs(Values &inputs, Values &outputs) {
+  std::set<BasicBlock*> ExitBlocks;
+  for (std::set<BasicBlock*>::const_iterator ci = BlocksToExtract.begin(),
+       ce = BlocksToExtract.end(); ci != ce; ++ci) {
+    BasicBlock *BB = *ci;
+
+    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+      // If a used value is defined outside the region, it's an input.  If an
+      // instruction is used outside the region, it's an output.
+      for (User::op_iterator O = I->op_begin(), E = I->op_end(); O != E; ++O)
+        if (definedInCaller(*O))
+          inputs.push_back(*O);
+
+      // Consider uses of this instruction (outputs).
+      for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
+           UI != E; ++UI)
+        if (!definedInRegion(*UI)) {
+          outputs.push_back(I);
+          break;
+        }
+    } // for: insts
+
+    // Keep track of the exit blocks from the region.
+    TerminatorInst *TI = BB->getTerminator();
+    for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
+      if (!BlocksToExtract.count(TI->getSuccessor(i)))
+        ExitBlocks.insert(TI->getSuccessor(i));
+  } // for: basic blocks
+
+  NumExitBlocks = ExitBlocks.size();
+
+  // Eliminate duplicates.
+  std::sort(inputs.begin(), inputs.end());
+  inputs.erase(std::unique(inputs.begin(), inputs.end()), inputs.end());
+  std::sort(outputs.begin(), outputs.end());
+  outputs.erase(std::unique(outputs.begin(), outputs.end()), outputs.end());
+}
+
+/// constructFunction - make a function based on inputs and outputs, as follows:
+/// f(in0, ..., inN, out0, ..., outN)
+///
+Function *CodeExtractor::constructFunction(const Values &inputs,
+                                           const Values &outputs,
+                                           BasicBlock *header,
+                                           BasicBlock *newRootNode,
+                                           BasicBlock *newHeader,
+                                           Function *oldFunction,
+                                           Module *M) {
+  DOUT << "inputs: " << inputs.size() << "\n";
+  DOUT << "outputs: " << outputs.size() << "\n";
+
+  // This function returns unsigned, outputs will go back by reference.
+  switch (NumExitBlocks) {
+  case 0:
+  case 1: RetTy = Type::VoidTy; break;
+  case 2: RetTy = Type::Int1Ty; break;
+  default: RetTy = Type::Int16Ty; break;
+  }
+
+  std::vector<const Type*> paramTy;
+
+  // Add the types of the input values to the function's argument list
+  for (Values::const_iterator i = inputs.begin(),
+         e = inputs.end(); i != e; ++i) {
+    const Value *value = *i;
+    DOUT << "value used in func: " << *value << "\n";
+    paramTy.push_back(value->getType());
+  }
+
+  // Add the types of the output values to the function's argument list.
+  for (Values::const_iterator I = outputs.begin(), E = outputs.end();
+       I != E; ++I) {
+    DOUT << "instr used in func: " << **I << "\n";
+    if (AggregateArgs)
+      paramTy.push_back((*I)->getType());
+    else
+      paramTy.push_back(PointerType::getUnqual((*I)->getType()));
+  }
+
+  DOUT << "Function type: " << *RetTy << " f(";
+  for (std::vector<const Type*>::iterator i = paramTy.begin(),
+         e = paramTy.end(); i != e; ++i)
+    DOUT << **i << ", ";
+  DOUT << ")\n";
+
+  if (AggregateArgs && (inputs.size() + outputs.size() > 0)) {
+    PointerType *StructPtr = PointerType::getUnqual(StructType::get(paramTy));
+    paramTy.clear();
+    paramTy.push_back(StructPtr);
+  }
+  const FunctionType *funcType = FunctionType::get(RetTy, paramTy, false);
+
+  // Create the new function
+  Function *newFunction = Function::Create(funcType,
+                                           GlobalValue::InternalLinkage,
+                                           oldFunction->getName() + "_" +
+                                           header->getName(), M);
+  // If the old function is no-throw, so is the new one.
+  if (oldFunction->doesNotThrow())
+    newFunction->setDoesNotThrow(true);
+  
+  newFunction->getBasicBlockList().push_back(newRootNode);
+
+  // Create an iterator to name all of the arguments we inserted.
+  Function::arg_iterator AI = newFunction->arg_begin();
+
+  // Rewrite all users of the inputs in the extracted region to use the
+  // arguments (or appropriate addressing into struct) instead.
+  for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
+    Value *RewriteVal;
+    if (AggregateArgs) {
+      Value *Idx[2];
+      Idx[0] = Constant::getNullValue(Type::Int32Ty);
+      Idx[1] = ConstantInt::get(Type::Int32Ty, i);
+      std::string GEPname = "gep_" + inputs[i]->getName();
+      TerminatorInst *TI = newFunction->begin()->getTerminator();
+      GetElementPtrInst *GEP = GetElementPtrInst::Create(AI, Idx, Idx+2, 
+                                                         GEPname, TI);
+      RewriteVal = new LoadInst(GEP, "load" + GEPname, TI);
+    } else
+      RewriteVal = AI++;
+
+    std::vector<User*> Users(inputs[i]->use_begin(), inputs[i]->use_end());
+    for (std::vector<User*>::iterator use = Users.begin(), useE = Users.end();
+         use != useE; ++use)
+      if (Instruction* inst = dyn_cast<Instruction>(*use))
+        if (BlocksToExtract.count(inst->getParent()))
+          inst->replaceUsesOfWith(inputs[i], RewriteVal);
+  }
+
+  // Set names for input and output arguments.
+  if (!AggregateArgs) {
+    AI = newFunction->arg_begin();
+    for (unsigned i = 0, e = inputs.size(); i != e; ++i, ++AI)
+      AI->setName(inputs[i]->getName());
+    for (unsigned i = 0, e = outputs.size(); i != e; ++i, ++AI)
+      AI->setName(outputs[i]->getName()+".out");
+  }
+
+  // Rewrite branches to basic blocks outside of the loop to new dummy blocks
+  // within the new function. This must be done before we lose track of which
+  // blocks were originally in the code region.
+  std::vector<User*> Users(header->use_begin(), header->use_end());
+  for (unsigned i = 0, e = Users.size(); i != e; ++i)
+    // The BasicBlock which contains the branch is not in the region
+    // modify the branch target to a new block
+    if (TerminatorInst *TI = dyn_cast<TerminatorInst>(Users[i]))
+      if (!BlocksToExtract.count(TI->getParent()) &&
+          TI->getParent()->getParent() == oldFunction)
+        TI->replaceUsesOfWith(header, newHeader);
+
+  return newFunction;
+}
+
+/// emitCallAndSwitchStatement - This method sets up the caller side by adding
+/// the call instruction, splitting any PHI nodes in the header block as
+/// necessary.
+void CodeExtractor::
+emitCallAndSwitchStatement(Function *newFunction, BasicBlock *codeReplacer,
+                           Values &inputs, Values &outputs) {
+  // Emit a call to the new function, passing in: *pointer to struct (if
+  // aggregating parameters), or plan inputs and allocated memory for outputs
+  std::vector<Value*> params, StructValues, ReloadOutputs;
+
+  // Add inputs as params, or to be filled into the struct
+  for (Values::iterator i = inputs.begin(), e = inputs.end(); i != e; ++i)
+    if (AggregateArgs)
+      StructValues.push_back(*i);
+    else
+      params.push_back(*i);
+
+  // Create allocas for the outputs
+  for (Values::iterator i = outputs.begin(), e = outputs.end(); i != e; ++i) {
+    if (AggregateArgs) {
+      StructValues.push_back(*i);
+    } else {
+      AllocaInst *alloca =
+        new AllocaInst((*i)->getType(), 0, (*i)->getName()+".loc",
+                       codeReplacer->getParent()->begin()->begin());
+      ReloadOutputs.push_back(alloca);
+      params.push_back(alloca);
+    }
+  }
+
+  AllocaInst *Struct = 0;
+  if (AggregateArgs && (inputs.size() + outputs.size() > 0)) {
+    std::vector<const Type*> ArgTypes;
+    for (Values::iterator v = StructValues.begin(),
+           ve = StructValues.end(); v != ve; ++v)
+      ArgTypes.push_back((*v)->getType());
+
+    // Allocate a struct at the beginning of this function
+    Type *StructArgTy = StructType::get(ArgTypes);
+    Struct =
+      new AllocaInst(StructArgTy, 0, "structArg",
+                     codeReplacer->getParent()->begin()->begin());
+    params.push_back(Struct);
+
+    for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
+      Value *Idx[2];
+      Idx[0] = Constant::getNullValue(Type::Int32Ty);
+      Idx[1] = ConstantInt::get(Type::Int32Ty, i);
+      GetElementPtrInst *GEP =
+        GetElementPtrInst::Create(Struct, Idx, Idx + 2,
+                                  "gep_" + StructValues[i]->getName());
+      codeReplacer->getInstList().push_back(GEP);
+      StoreInst *SI = new StoreInst(StructValues[i], GEP);
+      codeReplacer->getInstList().push_back(SI);
+    }
+  }
+
+  // Emit the call to the function
+  CallInst *call = CallInst::Create(newFunction, params.begin(), params.end(),
+                                    NumExitBlocks > 1 ? "targetBlock" : "");
+  codeReplacer->getInstList().push_back(call);
+
+  Function::arg_iterator OutputArgBegin = newFunction->arg_begin();
+  unsigned FirstOut = inputs.size();
+  if (!AggregateArgs)
+    std::advance(OutputArgBegin, inputs.size());
+
+  // Reload the outputs passed in by reference
+  for (unsigned i = 0, e = outputs.size(); i != e; ++i) {
+    Value *Output = 0;
+    if (AggregateArgs) {
+      Value *Idx[2];
+      Idx[0] = Constant::getNullValue(Type::Int32Ty);
+      Idx[1] = ConstantInt::get(Type::Int32Ty, FirstOut + i);
+      GetElementPtrInst *GEP
+        = GetElementPtrInst::Create(Struct, Idx, Idx + 2,
+                                    "gep_reload_" + outputs[i]->getName());
+      codeReplacer->getInstList().push_back(GEP);
+      Output = GEP;
+    } else {
+      Output = ReloadOutputs[i];
+    }
+    LoadInst *load = new LoadInst(Output, outputs[i]->getName()+".reload");
+    codeReplacer->getInstList().push_back(load);
+    std::vector<User*> Users(outputs[i]->use_begin(), outputs[i]->use_end());
+    for (unsigned u = 0, e = Users.size(); u != e; ++u) {
+      Instruction *inst = cast<Instruction>(Users[u]);
+      if (!BlocksToExtract.count(inst->getParent()))
+        inst->replaceUsesOfWith(outputs[i], load);
+    }
+  }
+
+  // Now we can emit a switch statement using the call as a value.
+  SwitchInst *TheSwitch =
+      SwitchInst::Create(ConstantInt::getNullValue(Type::Int16Ty),
+                         codeReplacer, 0, codeReplacer);
+
+  // Since there may be multiple exits from the original region, make the new
+  // function return an unsigned, switch on that number.  This loop iterates
+  // over all of the blocks in the extracted region, updating any terminator
+  // instructions in the to-be-extracted region that branch to blocks that are
+  // not in the region to be extracted.
+  std::map<BasicBlock*, BasicBlock*> ExitBlockMap;
+
+  unsigned switchVal = 0;
+  for (std::set<BasicBlock*>::const_iterator i = BlocksToExtract.begin(),
+         e = BlocksToExtract.end(); i != e; ++i) {
+    TerminatorInst *TI = (*i)->getTerminator();
+    for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
+      if (!BlocksToExtract.count(TI->getSuccessor(i))) {
+        BasicBlock *OldTarget = TI->getSuccessor(i);
+        // add a new basic block which returns the appropriate value
+        BasicBlock *&NewTarget = ExitBlockMap[OldTarget];
+        if (!NewTarget) {
+          // If we don't already have an exit stub for this non-extracted
+          // destination, create one now!
+          NewTarget = BasicBlock::Create(OldTarget->getName() + ".exitStub",
+                                         newFunction);
+          unsigned SuccNum = switchVal++;
+
+          Value *brVal = 0;
+          switch (NumExitBlocks) {
+          case 0:
+          case 1: break;  // No value needed.
+          case 2:         // Conditional branch, return a bool
+            brVal = ConstantInt::get(Type::Int1Ty, !SuccNum);
+            break;
+          default:
+            brVal = ConstantInt::get(Type::Int16Ty, SuccNum);
+            break;
+          }
+
+          ReturnInst *NTRet = ReturnInst::Create(brVal, NewTarget);
+
+          // Update the switch instruction.
+          TheSwitch->addCase(ConstantInt::get(Type::Int16Ty, SuccNum),
+                             OldTarget);
+
+          // Restore values just before we exit
+          Function::arg_iterator OAI = OutputArgBegin;
+          for (unsigned out = 0, e = outputs.size(); out != e; ++out) {
+            // For an invoke, the normal destination is the only one that is
+            // dominated by the result of the invocation
+            BasicBlock *DefBlock = cast<Instruction>(outputs[out])->getParent();
+
+            bool DominatesDef = true;
+
+            if (InvokeInst *Invoke = dyn_cast<InvokeInst>(outputs[out])) {
+              DefBlock = Invoke->getNormalDest();
+
+              // Make sure we are looking at the original successor block, not
+              // at a newly inserted exit block, which won't be in the dominator
+              // info.
+              for (std::map<BasicBlock*, BasicBlock*>::iterator I =
+                     ExitBlockMap.begin(), E = ExitBlockMap.end(); I != E; ++I)
+                if (DefBlock == I->second) {
+                  DefBlock = I->first;
+                  break;
+                }
+
+              // In the extract block case, if the block we are extracting ends
+              // with an invoke instruction, make sure that we don't emit a
+              // store of the invoke value for the unwind block.
+              if (!DT && DefBlock != OldTarget)
+                DominatesDef = false;
+            }
+
+            if (DT)
+              DominatesDef = DT->dominates(DefBlock, OldTarget);
+
+            if (DominatesDef) {
+              if (AggregateArgs) {
+                Value *Idx[2];
+                Idx[0] = Constant::getNullValue(Type::Int32Ty);
+                Idx[1] = ConstantInt::get(Type::Int32Ty,FirstOut+out);
+                GetElementPtrInst *GEP =
+                  GetElementPtrInst::Create(OAI, Idx, Idx + 2,
+                                            "gep_" + outputs[out]->getName(),
+                                            NTRet);
+                new StoreInst(outputs[out], GEP, NTRet);
+              } else {
+                new StoreInst(outputs[out], OAI, NTRet);
+              }
+            }
+            // Advance output iterator even if we don't emit a store
+            if (!AggregateArgs) ++OAI;
+          }
+        }
+
+        // rewrite the original branch instruction with this new target
+        TI->setSuccessor(i, NewTarget);
+      }
+  }
+
+  // Now that we've done the deed, simplify the switch instruction.
+  const Type *OldFnRetTy = TheSwitch->getParent()->getParent()->getReturnType();
+  switch (NumExitBlocks) {
+  case 0:
+    // There are no successors (the block containing the switch itself), which
+    // means that previously this was the last part of the function, and hence
+    // this should be rewritten as a `ret'
+
+    // Check if the function should return a value
+    if (OldFnRetTy == Type::VoidTy) {
+      ReturnInst::Create(0, TheSwitch);  // Return void
+    } else if (OldFnRetTy == TheSwitch->getCondition()->getType()) {
+      // return what we have
+      ReturnInst::Create(TheSwitch->getCondition(), TheSwitch);
+    } else {
+      // Otherwise we must have code extracted an unwind or something, just
+      // return whatever we want.
+      ReturnInst::Create(Constant::getNullValue(OldFnRetTy), TheSwitch);
+    }
+
+    TheSwitch->eraseFromParent();
+    break;
+  case 1:
+    // Only a single destination, change the switch into an unconditional
+    // branch.
+    BranchInst::Create(TheSwitch->getSuccessor(1), TheSwitch);
+    TheSwitch->eraseFromParent();
+    break;
+  case 2:
+    BranchInst::Create(TheSwitch->getSuccessor(1), TheSwitch->getSuccessor(2),
+                       call, TheSwitch);
+    TheSwitch->eraseFromParent();
+    break;
+  default:
+    // Otherwise, make the default destination of the switch instruction be one
+    // of the other successors.
+    TheSwitch->setOperand(0, call);
+    TheSwitch->setSuccessor(0, TheSwitch->getSuccessor(NumExitBlocks));
+    TheSwitch->removeCase(NumExitBlocks);  // Remove redundant case
+    break;
+  }
+}
+
+void CodeExtractor::moveCodeToFunction(Function *newFunction) {
+  Function *oldFunc = (*BlocksToExtract.begin())->getParent();
+  Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList();
+  Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList();
+
+  for (std::set<BasicBlock*>::const_iterator i = BlocksToExtract.begin(),
+         e = BlocksToExtract.end(); i != e; ++i) {
+    // Delete the basic block from the old function, and the list of blocks
+    oldBlocks.remove(*i);
+
+    // Insert this basic block into the new function
+    newBlocks.push_back(*i);
+  }
+}
+
+/// ExtractRegion - Removes a loop from a function, replaces it with a call to
+/// new function. Returns pointer to the new function.
+///
+/// algorithm:
+///
+/// find inputs and outputs for the region
+///
+/// for inputs: add to function as args, map input instr* to arg#
+/// for outputs: add allocas for scalars,
+///             add to func as args, map output instr* to arg#
+///
+/// rewrite func to use argument #s instead of instr*
+///
+/// for each scalar output in the function: at every exit, store intermediate
+/// computed result back into memory.
+///
+Function *CodeExtractor::
+ExtractCodeRegion(const std::vector<BasicBlock*> &code) {
+  if (!isEligible(code))
+    return 0;
+
+  // 1) Find inputs, outputs
+  // 2) Construct new function
+  //  * Add allocas for defs, pass as args by reference
+  //  * Pass in uses as args
+  // 3) Move code region, add call instr to func
+  //
+  BlocksToExtract.insert(code.begin(), code.end());
+
+  Values inputs, outputs;
+
+  // Assumption: this is a single-entry code region, and the header is the first
+  // block in the region.
+  BasicBlock *header = code[0];
+
+  for (unsigned i = 1, e = code.size(); i != e; ++i)
+    for (pred_iterator PI = pred_begin(code[i]), E = pred_end(code[i]);
+         PI != E; ++PI)
+      assert(BlocksToExtract.count(*PI) &&
+             "No blocks in this region may have entries from outside the region"
+             " except for the first block!");
+
+  // If we have to split PHI nodes or the entry block, do so now.
+  severSplitPHINodes(header);
+
+  // If we have any return instructions in the region, split those blocks so
+  // that the return is not in the region.
+  splitReturnBlocks();
+
+  Function *oldFunction = header->getParent();
+
+  // This takes place of the original loop
+  BasicBlock *codeReplacer = BasicBlock::Create("codeRepl", oldFunction,
+                                                header);
+
+  // The new function needs a root node because other nodes can branch to the
+  // head of the region, but the entry node of a function cannot have preds.
+  BasicBlock *newFuncRoot = BasicBlock::Create("newFuncRoot");
+  newFuncRoot->getInstList().push_back(BranchInst::Create(header));
+
+  // Find inputs to, outputs from the code region.
+  findInputsOutputs(inputs, outputs);
+
+  // Construct new function based on inputs/outputs & add allocas for all defs.
+  Function *newFunction = constructFunction(inputs, outputs, header,
+                                            newFuncRoot,
+                                            codeReplacer, oldFunction,
+                                            oldFunction->getParent());
+
+  emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs);
+
+  moveCodeToFunction(newFunction);
+
+  // Loop over all of the PHI nodes in the header block, and change any
+  // references to the old incoming edge to be the new incoming edge.
+  for (BasicBlock::iterator I = header->begin(); isa<PHINode>(I); ++I) {
+    PHINode *PN = cast<PHINode>(I);
+    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+      if (!BlocksToExtract.count(PN->getIncomingBlock(i)))
+        PN->setIncomingBlock(i, newFuncRoot);
+  }
+
+  // Look at all successors of the codeReplacer block.  If any of these blocks
+  // had PHI nodes in them, we need to update the "from" block to be the code
+  // replacer, not the original block in the extracted region.
+  std::vector<BasicBlock*> Succs(succ_begin(codeReplacer),
+                                 succ_end(codeReplacer));
+  for (unsigned i = 0, e = Succs.size(); i != e; ++i)
+    for (BasicBlock::iterator I = Succs[i]->begin(); isa<PHINode>(I); ++I) {
+      PHINode *PN = cast<PHINode>(I);
+      std::set<BasicBlock*> ProcessedPreds;
+      for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+        if (BlocksToExtract.count(PN->getIncomingBlock(i))) {
+          if (ProcessedPreds.insert(PN->getIncomingBlock(i)).second)
+            PN->setIncomingBlock(i, codeReplacer);
+          else {
+            // There were multiple entries in the PHI for this block, now there
+            // is only one, so remove the duplicated entries.
+            PN->removeIncomingValue(i, false);
+            --i; --e;
+          }
+        }
+    }
+
+  //cerr << "NEW FUNCTION: " << *newFunction;
+  //  verifyFunction(*newFunction);
+
+  //  cerr << "OLD FUNCTION: " << *oldFunction;
+  //  verifyFunction(*oldFunction);
+
+  DEBUG(if (verifyFunction(*newFunction)) abort());
+  return newFunction;
+}
+
+bool CodeExtractor::isEligible(const std::vector<BasicBlock*> &code) {
+  // Deny code region if it contains allocas or vastarts.
+  for (std::vector<BasicBlock*>::const_iterator BB = code.begin(), e=code.end();
+       BB != e; ++BB)
+    for (BasicBlock::const_iterator I = (*BB)->begin(), Ie = (*BB)->end();
+         I != Ie; ++I)
+      if (isa<AllocaInst>(*I))
+        return false;
+      else if (const CallInst *CI = dyn_cast<CallInst>(I))
+        if (const Function *F = CI->getCalledFunction())
+          if (F->getIntrinsicID() == Intrinsic::vastart)
+            return false;
+  return true;
+}
+
+
+/// ExtractCodeRegion - slurp a sequence of basic blocks into a brand new
+/// function
+///
+Function* llvm::ExtractCodeRegion(DominatorTree &DT,
+                                  const std::vector<BasicBlock*> &code,
+                                  bool AggregateArgs) {
+  return CodeExtractor(&DT, AggregateArgs).ExtractCodeRegion(code);
+}
+
+/// ExtractBasicBlock - slurp a natural loop into a brand new function
+///
+Function* llvm::ExtractLoop(DominatorTree &DT, Loop *L, bool AggregateArgs) {
+  return CodeExtractor(&DT, AggregateArgs).ExtractCodeRegion(L->getBlocks());
+}
+
+/// ExtractBasicBlock - slurp a basic block into a brand new function
+///
+Function* llvm::ExtractBasicBlock(BasicBlock *BB, bool AggregateArgs) {
+  std::vector<BasicBlock*> Blocks;
+  Blocks.push_back(BB);
+  return CodeExtractor(0, AggregateArgs).ExtractCodeRegion(Blocks);
+}