llvm/lib/Transforms/Utils/CodeExtractor.cpp - toolchain/llvm-project - Gitiles

 //===- CodeExtractor.cpp - Pull code region into a new function -----------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file was developed by the LLVM research group and 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/BasicBlock.h"
 #include "llvm/Constants.h"
 #include "llvm/DerivedTypes.h"
 #include "llvm/Instructions.h"
 #include "llvm/Module.h"
 #include "llvm/Pass.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/Verifier.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/FunctionUtils.h"
 #include "Support/Debug.h"
 #include "Support/StringExtras.h"
 #include <algorithm>
 #include <set>
 using namespace llvm;

 namespace {

   /// getFunctionArg - Return a pointer to F's ARGNOth argument.
   ///
   Argument *getFunctionArg(Function *F, unsigned argno) {
     Function::aiterator I = F->abegin();
     std::advance(I, argno);
     return I;
   }

   struct CodeExtractor {
     typedef std::vector<Value*> Values;
     typedef std::vector<std::pair<unsigned, unsigned> > PhiValChangesTy;
     typedef std::map<PHINode*, PhiValChangesTy> PhiVal2ArgTy;
     PhiVal2ArgTy PhiVal2Arg;
     std::set<BasicBlock*> BlocksToExtract;
   public:
     Function *ExtractCodeRegion(const std::vector<BasicBlock*> &code);

   private:
     void findInputsOutputs(Values &inputs, Values &outputs,
                            BasicBlock *newHeader,
                            BasicBlock *newRootNode);

     void processPhiNodeInputs(PHINode *Phi,
                               Values &inputs,
                               BasicBlock *newHeader,
                               BasicBlock *newRootNode);

     void rewritePhiNodes(Function *F, BasicBlock *newFuncRoot);

     Function *constructFunction(const Values &inputs,
                                 const Values &outputs,
                                 BasicBlock *newRootNode, BasicBlock *newHeader,
                                 Function *oldFunction, Module *M);

     void moveCodeToFunction(Function *newFunction);

     void emitCallAndSwitchStatement(Function *newFunction,
                                     BasicBlock *newHeader,
                                     Values &inputs,
                                     Values &outputs);

   };
 }

 void CodeExtractor::processPhiNodeInputs(PHINode *Phi,
                                          Values &inputs,
                                          BasicBlock *codeReplacer,
                                          BasicBlock *newFuncRoot)
 {
   // Separate incoming values and BasicBlocks as internal/external. We ignore
   // the case where both the value and BasicBlock are internal, because we don't
   // need to do a thing.
   std::vector<unsigned> EValEBB;
   std::vector<unsigned> EValIBB;
   std::vector<unsigned> IValEBB;

   for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
     Value *phiVal = Phi->getIncomingValue(i);
     if (Instruction *Inst = dyn_cast<Instruction>(phiVal)) {
       if (BlocksToExtract.count(Inst->getParent())) {
         if (!BlocksToExtract.count(Phi->getIncomingBlock(i)))
           IValEBB.push_back(i);
       } else {
         if (BlocksToExtract.count(Phi->getIncomingBlock(i)))
           EValIBB.push_back(i);
         else
           EValEBB.push_back(i);
       }
     } else if (Constant *Const = dyn_cast<Constant>(phiVal)) {
       // Constants are internal, but considered `external' if they are coming
       // from an external block.
       if (!BlocksToExtract.count(Phi->getIncomingBlock(i)))
         EValEBB.push_back(i);
     } else if (Argument *Arg = dyn_cast<Argument>(phiVal)) {
       // arguments are external
       if (BlocksToExtract.count(Phi->getIncomingBlock(i)))
         EValIBB.push_back(i);
       else
         EValEBB.push_back(i);
     } else {
       phiVal->dump();
       assert(0 && "Unhandled input in a Phi node");
     }
   }

   // Both value and block are external. Need to group all of
   // these, have an external phi, pass the result as an
   // argument, and have THIS phi use that result.
   if (EValEBB.size() > 0) {
     if (EValEBB.size() == 1) {
       // Now if it's coming from the newFuncRoot, it's that funky input
       unsigned phiIdx = EValEBB[0];
       if (!dyn_cast<Constant>(Phi->getIncomingValue(phiIdx)))
       {
         PhiVal2Arg[Phi].push_back(std::make_pair(phiIdx, inputs.size()));
         // We can just pass this value in as argument
         inputs.push_back(Phi->getIncomingValue(phiIdx));
       }
       Phi->setIncomingBlock(phiIdx, newFuncRoot);
     } else {
       PHINode *externalPhi = new PHINode(Phi->getType(), "extPhi");
       codeReplacer->getInstList().insert(codeReplacer->begin(), externalPhi);
       for (std::vector<unsigned>::iterator i = EValEBB.begin(),
              e = EValEBB.end(); i != e; ++i)
       {
         externalPhi->addIncoming(Phi->getIncomingValue(*i),
                                  Phi->getIncomingBlock(*i));

         // We make these values invalid instead of deleting them because that
         // would shift the indices of other values... The fixPhiNodes should
         // clean these phi nodes up later.
         Phi->setIncomingValue(*i, 0);
         Phi->setIncomingBlock(*i, 0);
       }
       PhiVal2Arg[Phi].push_back(std::make_pair(Phi->getNumIncomingValues(),
                                                inputs.size()));
       // We can just pass this value in as argument
       inputs.push_back(externalPhi);
     }
   }

   // When the value is external, but block internal...
   // just pass it in as argument, no change to phi node
   for (std::vector<unsigned>::iterator i = EValIBB.begin(),
          e = EValIBB.end(); i != e; ++i)
   {
     // rewrite the phi input node to be an argument
     PhiVal2Arg[Phi].push_back(std::make_pair(*i, inputs.size()));
     inputs.push_back(Phi->getIncomingValue(*i));
   }

   // Value internal, block external
   // this can happen if we are extracting a part of a loop
   for (std::vector<unsigned>::iterator i = IValEBB.begin(),
          e = IValEBB.end(); i != e; ++i)
   {
     assert(0 && "Cannot (YET) handle internal values via external blocks");
   }
 }


 void CodeExtractor::findInputsOutputs(Values &inputs, Values &outputs,
                                       BasicBlock *newHeader,
                                       BasicBlock *newRootNode) {
   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.
       if (PHINode *Phi = dyn_cast<PHINode>(I)) {
         processPhiNodeInputs(Phi, inputs, newHeader, newRootNode);
       } else {
         // All other instructions go through the generic input finder
         // Loop over the operands of each instruction (inputs)
         for (User::op_iterator op = I->op_begin(), opE = I->op_end();
              op != opE; ++op)
           if (Instruction *opI = dyn_cast<Instruction>(*op)) {
             // Check if definition of this operand is within the loop
             if (!BlocksToExtract.count(opI->getParent())) {
               // add this operand to the inputs
               inputs.push_back(opI);
             }
           } else if (isa<Argument>(*op)) {
             inputs.push_back(*op);
           }
       }

       // Consider uses of this instruction (outputs)
       for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
            UI != E; ++UI)
         if (!BlocksToExtract.count(cast<Instruction>(*UI)->getParent()))
           outputs.push_back(*UI);
     } // for: insts
   } // for: basic blocks
 }

 void CodeExtractor::rewritePhiNodes(Function *F,
                                     BasicBlock *newFuncRoot) {
   // Write any changes that were saved before: use function arguments as inputs
   for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end();
        i != e; ++i)
   {
     PHINode *phi = (*i).first;
     PhiValChangesTy &values = (*i).second;
     for (unsigned cIdx = 0, ce = values.size(); cIdx != ce; ++cIdx)
     {
       unsigned phiValueIdx = values[cIdx].first, argNum = values[cIdx].second;
       if (phiValueIdx < phi->getNumIncomingValues())
         phi->setIncomingValue(phiValueIdx, getFunctionArg(F, argNum));
       else
         phi->addIncoming(getFunctionArg(F, argNum), newFuncRoot);
     }
   }

   // Delete any invalid Phi node inputs that were marked as NULL previously
   for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end();
        i != e; ++i)
   {
     PHINode *phi = (*i).first;
     for (unsigned idx = 0, end = phi->getNumIncomingValues(); idx != end; ++idx)
     {
       if (phi->getIncomingValue(idx) == 0 && phi->getIncomingBlock(idx) == 0) {
         phi->removeIncomingValue(idx);
         --idx;
         --end;
       }
     }
   }

   // We are done with the saved values
   PhiVal2Arg.clear();
 }


 /// 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 *newRootNode,
                                            BasicBlock *newHeader,
                                            Function *oldFunction, Module *M) {
   DEBUG(std::cerr << "inputs: " << inputs.size() << "\n");
   DEBUG(std::cerr << "outputs: " << outputs.size() << "\n");
   BasicBlock *header = *BlocksToExtract.begin();

   // This function returns unsigned, outputs will go back by reference.
   Type *retTy = Type::UShortTy;
   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;
     DEBUG(std::cerr << "value used in func: " << value << "\n");
     paramTy.push_back(value->getType());
   }

   // Add the types of the output values to the function's argument list, but
   // make them pointer types for scalars
   for (Values::const_iterator i = outputs.begin(),
          e = outputs.end(); i != e; ++i) {
     const Value *value = *i;
     DEBUG(std::cerr << "instr used in func: " << value << "\n");
     const Type *valueType = value->getType();
     // Convert scalar types into a pointer of that type
     if (valueType->isPrimitiveType()) {
       valueType = PointerType::get(valueType);
     }
     paramTy.push_back(valueType);
   }

   DEBUG(std::cerr << "Function type: " << retTy << " f(");
   for (std::vector<const Type*>::iterator i = paramTy.begin(),
          e = paramTy.end(); i != e; ++i)
     DEBUG(std::cerr << (*i) << ", ");
   DEBUG(std::cerr << ")\n");

   const FunctionType *funcType = FunctionType::get(retTy, paramTy, false);

   // Create the new function
   Function *newFunction = new Function(funcType,
                                        GlobalValue::InternalLinkage,
                                        oldFunction->getName() + "_code", M);
   newFunction->getBasicBlockList().push_back(newRootNode);

   for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
     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], getFunctionArg(newFunction, i));
   }

   // 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 (std::vector<User*>::iterator i = Users.begin(), e = Users.end();
        i != e; ++i) {
     if (BranchInst *inst = dyn_cast<BranchInst>(*i)) {
       BasicBlock *BB = inst->getParent();
       if (!BlocksToExtract.count(BB) && BB->getParent() == oldFunction) {
         // The BasicBlock which contains the branch is not in the region
         // modify the branch target to a new block
         inst->replaceUsesOfWith(header, newHeader);
       }
     }
   }

   return newFunction;
 }

 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);
   }
 }

 void
 CodeExtractor::emitCallAndSwitchStatement(Function *newFunction,
                                           BasicBlock *codeReplacer,
                                           Values &inputs,
                                           Values &outputs)
 {
   // Emit a call to the new function, passing allocated memory for outputs and
   // just plain inputs for non-scalars
   std::vector<Value*> params(inputs);

   for (Values::const_iterator i = outputs.begin(), e = outputs.end(); i != e;
        ++i) {
     Value *Output = *i;
     // Create allocas for scalar outputs
     if (Output->getType()->isPrimitiveType()) {
       AllocaInst *alloca =
         new AllocaInst((*i)->getType(), 0, Output->getName()+".loc",
                        codeReplacer->getParent()->begin()->begin());
       params.push_back(alloca);

       LoadInst *load = new LoadInst(alloca, Output->getName()+".reload");
       codeReplacer->getInstList().push_back(load);
       std::vector<User*> Users((*i)->use_begin(), (*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(*i, load);
         }
       }
     } else {
       params.push_back(*i);
     }
   }

   CallInst *call = new CallInst(newFunction, params, "targetBlock");
   codeReplacer->getInstList().push_front(call);

   // Now we can emit a switch statement using the call as a value.
   SwitchInst *TheSwitch = new SwitchInst(call, codeReplacer, 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 = new BasicBlock(OldTarget->getName() + ".exitStub",
                                      newFunction);

           ConstantUInt *brVal = ConstantUInt::get(Type::UShortTy, switchVal++);
           ReturnInst *NTRet = new ReturnInst(brVal, NewTarget);

           // Update the switch instruction.
           TheSwitch->addCase(brVal, OldTarget);

           // Restore values just before we exit
           // FIXME: Use a GetElementPtr to bunch the outputs in a struct
           for (unsigned out = 0, e = outputs.size(); out != e; ++out)
             new StoreInst(outputs[out], getFunctionArg(newFunction, out),NTRet);
         }

         // rewrite the original branch instruction with this new target
         TI->setSuccessor(i, NewTarget);
       }
   }

   // Now that we've done the deed, make the default destination of the switch
   // instruction be one of the exit blocks of the region.
   if (TheSwitch->getNumSuccessors() > 1) {
     // FIXME: this is broken w.r.t. PHI nodes, but the old code was more broken.
     // This edge is not traversable.
     TheSwitch->setSuccessor(0, TheSwitch->getSuccessor(1));
   }
 }


 /// 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)
 {
   // 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!");

   Function *oldFunction = header->getParent();

   // This takes place of the original loop
   BasicBlock *codeReplacer = new BasicBlock("codeRepl", oldFunction);

   // The new function needs a root node because other nodes can branch to the
   // head of the loop, and the root cannot have predecessors
   BasicBlock *newFuncRoot = new BasicBlock("newFuncRoot");
   newFuncRoot->getInstList().push_back(new BranchInst(header));

   // Find inputs to, outputs from the code region
   //
   // If one of the inputs is coming from a different basic block and it's in a
   // phi node, we need to rewrite the phi node:
   //
   // * All the inputs which involve basic blocks OUTSIDE of this region go into
   //   a NEW phi node that takes care of finding which value really came in.
   //   The result of this phi is passed to the function as an argument.
   //
   // * All the other phi values stay.
   //
   // FIXME: PHI nodes' incoming blocks aren't being rewritten to accomodate for
   // blocks moving to a new function.
   // SOLUTION: move Phi nodes out of the loop header into the codeReplacer, pass
   // the values as parameters to the function
   findInputsOutputs(inputs, outputs, codeReplacer, newFuncRoot);

   // Step 2: Construct new function based on inputs/outputs,
   // Add allocas for all defs
   Function *newFunction = constructFunction(inputs, outputs, newFuncRoot,
                                             codeReplacer, oldFunction,
                                             oldFunction->getParent());

   rewritePhiNodes(newFunction, newFuncRoot);

   emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs);

   moveCodeToFunction(newFunction);

   DEBUG(if (verifyFunction(*newFunction)) abort());
   return newFunction;
 }

 /// ExtractCodeRegion - slurp a sequence of basic blocks into a brand new
 /// function
 ///
 Function* llvm::ExtractCodeRegion(const std::vector<BasicBlock*> &code) {
   return CodeExtractor().ExtractCodeRegion(code);
 }

 /// ExtractBasicBlock - slurp a natural loop into a brand new function
 ///
 Function* llvm::ExtractLoop(Loop *L) {
   return CodeExtractor().ExtractCodeRegion(L->getBlocks());
 }

 /// ExtractBasicBlock - slurp a basic block into a brand new function
 ///
 Function* llvm::ExtractBasicBlock(BasicBlock *BB) {
   std::vector<BasicBlock*> Blocks;
   Blocks.push_back(BB);
   return CodeExtractor().ExtractCodeRegion(Blocks);
 }
	//===- CodeExtractor.cpp - Pull code region into a new function -----------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file was developed by the LLVM research group and 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/BasicBlock.h"
	#include "llvm/Constants.h"
	#include "llvm/DerivedTypes.h"
	#include "llvm/Instructions.h"
	#include "llvm/Module.h"
	#include "llvm/Pass.h"
	#include "llvm/Analysis/LoopInfo.h"
	#include "llvm/Analysis/Verifier.h"
	#include "llvm/Transforms/Utils/BasicBlockUtils.h"
	#include "llvm/Transforms/Utils/FunctionUtils.h"
	#include "Support/Debug.h"
	#include "Support/StringExtras.h"
	#include <algorithm>
	#include <set>
	using namespace llvm;

	namespace {

	/// getFunctionArg - Return a pointer to F's ARGNOth argument.
	///
	Argument getFunctionArg(Function F, unsigned argno) {
	Function::aiterator I = F->abegin();
	std::advance(I, argno);
	return I;
	}

	struct CodeExtractor {
	typedef std::vector<Value*> Values;
	typedef std::vector<std::pair<unsigned, unsigned> > PhiValChangesTy;
	typedef std::map<PHINode*, PhiValChangesTy> PhiVal2ArgTy;
	PhiVal2ArgTy PhiVal2Arg;
	std::set<BasicBlock*> BlocksToExtract;
	public:
	Function ExtractCodeRegion(const std::vector<BasicBlock> &code);

	private:
	void findInputsOutputs(Values &inputs, Values &outputs,
	BasicBlock *newHeader,
	BasicBlock *newRootNode);

	void processPhiNodeInputs(PHINode *Phi,
	Values &inputs,
	BasicBlock *newHeader,
	BasicBlock *newRootNode);

	void rewritePhiNodes(Function F, BasicBlock newFuncRoot);

	Function *constructFunction(const Values &inputs,
	const Values &outputs,
	BasicBlock newRootNode, BasicBlock newHeader,
	Function oldFunction, Module M);

	void moveCodeToFunction(Function *newFunction);

	void emitCallAndSwitchStatement(Function *newFunction,
	BasicBlock *newHeader,
	Values &inputs,
	Values &outputs);

	};
	}

	void CodeExtractor::processPhiNodeInputs(PHINode *Phi,
	Values &inputs,
	BasicBlock *codeReplacer,
	BasicBlock *newFuncRoot)
	{
	// Separate incoming values and BasicBlocks as internal/external. We ignore
	// the case where both the value and BasicBlock are internal, because we don't
	// need to do a thing.
	std::vector<unsigned> EValEBB;
	std::vector<unsigned> EValIBB;
	std::vector<unsigned> IValEBB;

	for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
	Value *phiVal = Phi->getIncomingValue(i);
	if (Instruction *Inst = dyn_cast<Instruction>(phiVal)) {
	if (BlocksToExtract.count(Inst->getParent())) {
	if (!BlocksToExtract.count(Phi->getIncomingBlock(i)))
	IValEBB.push_back(i);
	} else {
	if (BlocksToExtract.count(Phi->getIncomingBlock(i)))
	EValIBB.push_back(i);
	else
	EValEBB.push_back(i);
	}
	} else if (Constant *Const = dyn_cast<Constant>(phiVal)) {
	// Constants are internal, but considered `external' if they are coming
	// from an external block.
	if (!BlocksToExtract.count(Phi->getIncomingBlock(i)))
	EValEBB.push_back(i);
	} else if (Argument *Arg = dyn_cast<Argument>(phiVal)) {
	// arguments are external
	if (BlocksToExtract.count(Phi->getIncomingBlock(i)))
	EValIBB.push_back(i);
	else
	EValEBB.push_back(i);
	} else {
	phiVal->dump();
	assert(0 && "Unhandled input in a Phi node");
	}
	}

	// Both value and block are external. Need to group all of
	// these, have an external phi, pass the result as an
	// argument, and have THIS phi use that result.
	if (EValEBB.size() > 0) {
	if (EValEBB.size() == 1) {
	// Now if it's coming from the newFuncRoot, it's that funky input
	unsigned phiIdx = EValEBB[0];
	if (!dyn_cast<Constant>(Phi->getIncomingValue(phiIdx)))
	{
	PhiVal2Arg[Phi].push_back(std::make_pair(phiIdx, inputs.size()));
	// We can just pass this value in as argument
	inputs.push_back(Phi->getIncomingValue(phiIdx));
	}
	Phi->setIncomingBlock(phiIdx, newFuncRoot);
	} else {
	PHINode *externalPhi = new PHINode(Phi->getType(), "extPhi");
	codeReplacer->getInstList().insert(codeReplacer->begin(), externalPhi);
	for (std::vector<unsigned>::iterator i = EValEBB.begin(),
	e = EValEBB.end(); i != e; ++i)
	{
	externalPhi->addIncoming(Phi->getIncomingValue(*i),
	Phi->getIncomingBlock(*i));

	// We make these values invalid instead of deleting them because that
	// would shift the indices of other values... The fixPhiNodes should
	// clean these phi nodes up later.
	Phi->setIncomingValue(*i, 0);
	Phi->setIncomingBlock(*i, 0);
	}
	PhiVal2Arg[Phi].push_back(std::make_pair(Phi->getNumIncomingValues(),
	inputs.size()));
	// We can just pass this value in as argument
	inputs.push_back(externalPhi);
	}
	}

	// When the value is external, but block internal...
	// just pass it in as argument, no change to phi node
	for (std::vector<unsigned>::iterator i = EValIBB.begin(),
	e = EValIBB.end(); i != e; ++i)
	{
	// rewrite the phi input node to be an argument
	PhiVal2Arg[Phi].push_back(std::make_pair(*i, inputs.size()));
	inputs.push_back(Phi->getIncomingValue(*i));
	}

	// Value internal, block external
	// this can happen if we are extracting a part of a loop
	for (std::vector<unsigned>::iterator i = IValEBB.begin(),
	e = IValEBB.end(); i != e; ++i)
	{
	assert(0 && "Cannot (YET) handle internal values via external blocks");
	}
	}


	void CodeExtractor::findInputsOutputs(Values &inputs, Values &outputs,
	BasicBlock *newHeader,
	BasicBlock *newRootNode) {
	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.
	if (PHINode *Phi = dyn_cast<PHINode>(I)) {
	processPhiNodeInputs(Phi, inputs, newHeader, newRootNode);
	} else {
	// All other instructions go through the generic input finder
	// Loop over the operands of each instruction (inputs)
	for (User::op_iterator op = I->op_begin(), opE = I->op_end();
	op != opE; ++op)
	if (Instruction opI = dyn_cast<Instruction>(op)) {
	// Check if definition of this operand is within the loop
	if (!BlocksToExtract.count(opI->getParent())) {
	// add this operand to the inputs
	inputs.push_back(opI);
	}
	} else if (isa<Argument>(*op)) {
	inputs.push_back(*op);
	}
	}

	// Consider uses of this instruction (outputs)
	for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
	UI != E; ++UI)
	if (!BlocksToExtract.count(cast<Instruction>(*UI)->getParent()))
	outputs.push_back(*UI);
	} // for: insts
	} // for: basic blocks
	}

	void CodeExtractor::rewritePhiNodes(Function *F,
	BasicBlock *newFuncRoot) {
	// Write any changes that were saved before: use function arguments as inputs
	for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end();
	i != e; ++i)
	{
	PHINode phi = (i).first;
	PhiValChangesTy &values = (*i).second;
	for (unsigned cIdx = 0, ce = values.size(); cIdx != ce; ++cIdx)
	{
	unsigned phiValueIdx = values[cIdx].first, argNum = values[cIdx].second;
	if (phiValueIdx < phi->getNumIncomingValues())
	phi->setIncomingValue(phiValueIdx, getFunctionArg(F, argNum));
	else
	phi->addIncoming(getFunctionArg(F, argNum), newFuncRoot);
	}
	}

	// Delete any invalid Phi node inputs that were marked as NULL previously
	for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end();
	i != e; ++i)
	{
	PHINode phi = (i).first;
	for (unsigned idx = 0, end = phi->getNumIncomingValues(); idx != end; ++idx)
	{
	if (phi->getIncomingValue(idx) == 0 && phi->getIncomingBlock(idx) == 0) {
	phi->removeIncomingValue(idx);
	--idx;
	--end;
	}
	}
	}

	// We are done with the saved values
	PhiVal2Arg.clear();
	}


	/// 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 *newRootNode,
	BasicBlock *newHeader,
	Function oldFunction, Module M) {
	DEBUG(std::cerr << "inputs: " << inputs.size() << "\n");
	DEBUG(std::cerr << "outputs: " << outputs.size() << "\n");
	BasicBlock header = BlocksToExtract.begin();

	// This function returns unsigned, outputs will go back by reference.
	Type *retTy = Type::UShortTy;
	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;
	DEBUG(std::cerr << "value used in func: " << value << "\n");
	paramTy.push_back(value->getType());
	}

	// Add the types of the output values to the function's argument list, but
	// make them pointer types for scalars
	for (Values::const_iterator i = outputs.begin(),
	e = outputs.end(); i != e; ++i) {
	const Value value = i;
	DEBUG(std::cerr << "instr used in func: " << value << "\n");
	const Type *valueType = value->getType();
	// Convert scalar types into a pointer of that type
	if (valueType->isPrimitiveType()) {
	valueType = PointerType::get(valueType);
	}
	paramTy.push_back(valueType);
	}

	DEBUG(std::cerr << "Function type: " << retTy << " f(");
	for (std::vector<const Type*>::iterator i = paramTy.begin(),
	e = paramTy.end(); i != e; ++i)
	DEBUG(std::cerr << (*i) << ", ");
	DEBUG(std::cerr << ")\n");

	const FunctionType *funcType = FunctionType::get(retTy, paramTy, false);

	// Create the new function
	Function *newFunction = new Function(funcType,
	GlobalValue::InternalLinkage,
	oldFunction->getName() + "_code", M);
	newFunction->getBasicBlockList().push_back(newRootNode);

	for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
	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], getFunctionArg(newFunction, i));
	}

	// 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 (std::vector<User*>::iterator i = Users.begin(), e = Users.end();
	i != e; ++i) {
	if (BranchInst inst = dyn_cast<BranchInst>(i)) {
	BasicBlock *BB = inst->getParent();
	if (!BlocksToExtract.count(BB) && BB->getParent() == oldFunction) {
	// The BasicBlock which contains the branch is not in the region
	// modify the branch target to a new block
	inst->replaceUsesOfWith(header, newHeader);
	}
	}
	}

	return newFunction;
	}

	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);
	}
	}

	void
	CodeExtractor::emitCallAndSwitchStatement(Function *newFunction,
	BasicBlock *codeReplacer,
	Values &inputs,
	Values &outputs)
	{
	// Emit a call to the new function, passing allocated memory for outputs and
	// just plain inputs for non-scalars
	std::vector<Value*> params(inputs);

	for (Values::const_iterator i = outputs.begin(), e = outputs.end(); i != e;
	++i) {
	Value Output = i;
	// Create allocas for scalar outputs
	if (Output->getType()->isPrimitiveType()) {
	AllocaInst *alloca =
	new AllocaInst((*i)->getType(), 0, Output->getName()+".loc",
	codeReplacer->getParent()->begin()->begin());
	params.push_back(alloca);

	LoadInst *load = new LoadInst(alloca, Output->getName()+".reload");
	codeReplacer->getInstList().push_back(load);
	std::vector<User> Users((i)->use_begin(), (*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(*i, load);
	}
	}
	} else {
	params.push_back(*i);
	}
	}

	CallInst *call = new CallInst(newFunction, params, "targetBlock");
	codeReplacer->getInstList().push_front(call);

	// Now we can emit a switch statement using the call as a value.
	SwitchInst *TheSwitch = new SwitchInst(call, codeReplacer, 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 = new BasicBlock(OldTarget->getName() + ".exitStub",
	newFunction);

	ConstantUInt *brVal = ConstantUInt::get(Type::UShortTy, switchVal++);
	ReturnInst *NTRet = new ReturnInst(brVal, NewTarget);

	// Update the switch instruction.
	TheSwitch->addCase(brVal, OldTarget);

	// Restore values just before we exit
	// FIXME: Use a GetElementPtr to bunch the outputs in a struct
	for (unsigned out = 0, e = outputs.size(); out != e; ++out)
	new StoreInst(outputs[out], getFunctionArg(newFunction, out),NTRet);
	}

	// rewrite the original branch instruction with this new target
	TI->setSuccessor(i, NewTarget);
	}
	}

	// Now that we've done the deed, make the default destination of the switch
	// instruction be one of the exit blocks of the region.
	if (TheSwitch->getNumSuccessors() > 1) {
	// FIXME: this is broken w.r.t. PHI nodes, but the old code was more broken.
	// This edge is not traversable.
	TheSwitch->setSuccessor(0, TheSwitch->getSuccessor(1));
	}
	}


	/// 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)
	{
	// 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!");

	Function *oldFunction = header->getParent();

	// This takes place of the original loop
	BasicBlock *codeReplacer = new BasicBlock("codeRepl", oldFunction);

	// The new function needs a root node because other nodes can branch to the
	// head of the loop, and the root cannot have predecessors
	BasicBlock *newFuncRoot = new BasicBlock("newFuncRoot");
	newFuncRoot->getInstList().push_back(new BranchInst(header));

	// Find inputs to, outputs from the code region
	//
	// If one of the inputs is coming from a different basic block and it's in a
	// phi node, we need to rewrite the phi node:
	//
	// * All the inputs which involve basic blocks OUTSIDE of this region go into
	// a NEW phi node that takes care of finding which value really came in.
	// The result of this phi is passed to the function as an argument.
	//
	// * All the other phi values stay.
	//
	// FIXME: PHI nodes' incoming blocks aren't being rewritten to accomodate for
	// blocks moving to a new function.
	// SOLUTION: move Phi nodes out of the loop header into the codeReplacer, pass
	// the values as parameters to the function
	findInputsOutputs(inputs, outputs, codeReplacer, newFuncRoot);

	// Step 2: Construct new function based on inputs/outputs,
	// Add allocas for all defs
	Function *newFunction = constructFunction(inputs, outputs, newFuncRoot,
	codeReplacer, oldFunction,
	oldFunction->getParent());

	rewritePhiNodes(newFunction, newFuncRoot);

	emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs);

	moveCodeToFunction(newFunction);

	DEBUG(if (verifyFunction(*newFunction)) abort());
	return newFunction;
	}

	/// ExtractCodeRegion - slurp a sequence of basic blocks into a brand new
	/// function
	///
	Function* llvm::ExtractCodeRegion(const std::vector<BasicBlock*> &code) {
	return CodeExtractor().ExtractCodeRegion(code);
	}

	/// ExtractBasicBlock - slurp a natural loop into a brand new function
	///
	Function* llvm::ExtractLoop(Loop *L) {
	return CodeExtractor().ExtractCodeRegion(L->getBlocks());
	}

	/// ExtractBasicBlock - slurp a basic block into a brand new function
	///
	Function* llvm::ExtractBasicBlock(BasicBlock *BB) {
	std::vector<BasicBlock*> Blocks;
	Blocks.push_back(BB);
	return CodeExtractor().ExtractCodeRegion(Blocks);
	}