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/Transforms/Utils/FunctionUtils.h"
 #include "llvm/Constants.h"
 #include "llvm/DerivedTypes.h"
 #include "llvm/Instructions.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 "Support/CommandLine.h"
 #include "Support/Debug.h"
 #include "Support/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 extrator. 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 CodeExtractor {
     typedef std::vector<Value*> Values;
     std::set<BasicBlock*> BlocksToExtract;
     DominatorSet *DS;
     bool AggregateArgs;
   public:
     CodeExtractor(DominatorSet *ds = 0, bool AggArgs = false)
       : DS(ds), AggregateArgs(AggregateArgsOpt) {}

     Function *ExtractCodeRegion(const std::vector<BasicBlock*> &code);

     bool isEligible(const std::vector<BasicBlock*> &code);

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

     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);

   };
 }

 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 *PN = dyn_cast<PHINode>(I)) {
         for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
           Value *V = PN->getIncomingValue(i);
           if (!BlocksToExtract.count(PN->getIncomingBlock(i)) &&
               (isa<Instruction>(V) || isa<Argument>(V)))
             inputs.push_back(V);
           else if (Instruction *opI = dyn_cast<Instruction>(V)) {
             if (!BlocksToExtract.count(opI->getParent()))
               inputs.push_back(opI);
           } else if (isa<Argument>(V))
             inputs.push_back(V);
         }
       } 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()))
               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(I);
           break;
         }
     } // for: insts
   } // for: basic blocks
 }

 /// 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) {
   DEBUG(std::cerr << "inputs: " << inputs.size() << "\n");
   DEBUG(std::cerr << "outputs: " << outputs.size() << "\n");

   // 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.
   for (Values::const_iterator I = outputs.begin(), E = outputs.end();
        I != E; ++I) {
     DEBUG(std::cerr << "instr used in func: " << *I << "\n");
     if (AggregateArgs)
       paramTy.push_back((*I)->getType());
     else
       paramTy.push_back(PointerType::get((*I)->getType()));
   }

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

   if (AggregateArgs && (inputs.size() + outputs.size() > 0)) {
     PointerType *StructPtr = PointerType::get(StructType::get(paramTy));
     paramTy.clear();
     paramTy.push_back(StructPtr);
   }
   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);

   // Create an iterator to name all of the arguments we inserted.
   Function::aiterator AI = newFunction->abegin();

   // 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) {
       std::vector<Value*> Indices;
       Indices.push_back(Constant::getNullValue(Type::UIntTy));
       Indices.push_back(ConstantUInt::get(Type::UIntTy, i));
       std::string GEPname = "gep_" + inputs[i]->getName();
       TerminatorInst *TI = newFunction->begin()->getTerminator();
       GetElementPtrInst *GEP = new GetElementPtrInst(AI, Indices, 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->abegin();
     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;
 }

 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 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) {
       std::vector<Value*> Indices;
       Indices.push_back(Constant::getNullValue(Type::UIntTy));
       Indices.push_back(ConstantUInt::get(Type::UIntTy, i));
       GetElementPtrInst *GEP =
         new GetElementPtrInst(Struct, Indices,
                               "gep_" + StructValues[i]->getName(), 0);
       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 = new CallInst(newFunction, params, "targetBlock");
   codeReplacer->getInstList().push_back(call);

   Function::aiterator OutputArgBegin = newFunction->abegin();
   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) {
       std::vector<Value*> Indices;
       Indices.push_back(Constant::getNullValue(Type::UIntTy));
       Indices.push_back(ConstantUInt::get(Type::UIntTy, FirstOut + i));
       GetElementPtrInst *GEP
         = new GetElementPtrInst(Struct, Indices,
                                 "gep_reload_" + outputs[i]->getName(), 0);
       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 = 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
           Function::aiterator 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();
             if (InvokeInst *Invoke = dyn_cast<InvokeInst>(outputs[out]))
               DefBlock = Invoke->getNormalDest();
             if (!DS || DS->dominates(DefBlock, TI->getParent()))
               if (AggregateArgs) {
                 std::vector<Value*> Indices;
                 Indices.push_back(Constant::getNullValue(Type::UIntTy));
                 Indices.push_back(ConstantUInt::get(Type::UIntTy,FirstOut+out));
                 GetElementPtrInst *GEP =
                   new GetElementPtrInst(OAI, Indices,
                                         "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.
   unsigned NumSuccs = TheSwitch->getNumSuccessors();
   if (NumSuccs > 1) {
     if (NumSuccs-1 == 1) {
       // Only a single destination, change the switch into an unconditional
       // branch.
       new BranchInst(TheSwitch->getSuccessor(1), TheSwitch);
       TheSwitch->getParent()->getInstList().erase(TheSwitch);
     } else {
       // Otherwise, make the default destination of the switch instruction be
       // one of the other successors.
       TheSwitch->setSuccessor(0, TheSwitch->getSuccessor(NumSuccs-1));
       TheSwitch->removeCase(NumSuccs-1);  // Remove redundant case
     }
   } else {
     // There is only 1 successor (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 (TheSwitch->getParent()->getParent()->getReturnType() != Type::VoidTy &&
         TheSwitch->getParent()->getParent()->getReturnType() ==
         TheSwitch->getCondition()->getType())
       // return what we have
       new ReturnInst(TheSwitch->getCondition(), TheSwitch);
     else
       // just return
       new ReturnInst(0, TheSwitch);

     TheSwitch->getParent()->getInstList().erase(TheSwitch);
   }
 }


 /// 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!");

   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, code[0],
                                             newFuncRoot,
                                             codeReplacer, oldFunction,
                                             oldFunction->getParent());

   emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs);

   moveCodeToFunction(newFunction);

   // Loop over all of the PHI nodes in the entry block (code[0]), and change any
   // references to the old incoming edge to be the new incoming edge.
   for (BasicBlock::iterator I = code[0]->begin();
        PHINode *PN = dyn_cast<PHINode>(I); ++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();
          PHINode *PN = dyn_cast<PHINode>(I); ++I)
       for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
         if (BlocksToExtract.count(PN->getIncomingBlock(i)))
           PN->setIncomingBlock(i, codeReplacer);


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

 bool CodeExtractor::isEligible(const std::vector<BasicBlock*> &code) {
   // Deny code region if it contains allocas
   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;
   return true;
 }


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

 /// ExtractBasicBlock - slurp a natural loop into a brand new function
 ///
 Function* llvm::ExtractLoop(DominatorSet &DS, Loop *L, bool AggregateArgs) {
   return CodeExtractor(&DS, 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);
 }
	//===- 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/Transforms/Utils/FunctionUtils.h"
	#include "llvm/Constants.h"
	#include "llvm/DerivedTypes.h"
	#include "llvm/Instructions.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 "Support/CommandLine.h"
	#include "Support/Debug.h"
	#include "Support/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 extrator. 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 CodeExtractor {
	typedef std::vector<Value*> Values;
	std::set<BasicBlock*> BlocksToExtract;
	DominatorSet *DS;
	bool AggregateArgs;
	public:
	CodeExtractor(DominatorSet *ds = 0, bool AggArgs = false)
	: DS(ds), AggregateArgs(AggregateArgsOpt) {}

	Function ExtractCodeRegion(const std::vector<BasicBlock> &code);

	bool isEligible(const std::vector<BasicBlock*> &code);

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

	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);

	};
	}

	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 *PN = dyn_cast<PHINode>(I)) {
	for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
	Value *V = PN->getIncomingValue(i);
	if (!BlocksToExtract.count(PN->getIncomingBlock(i)) &&
	(isa<Instruction>(V) \|\| isa<Argument>(V)))
	inputs.push_back(V);
	else if (Instruction *opI = dyn_cast<Instruction>(V)) {
	if (!BlocksToExtract.count(opI->getParent()))
	inputs.push_back(opI);
	} else if (isa<Argument>(V))
	inputs.push_back(V);
	}
	} 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()))
	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(I);
	break;
	}
	} // for: insts
	} // for: basic blocks
	}

	/// 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) {
	DEBUG(std::cerr << "inputs: " << inputs.size() << "\n");
	DEBUG(std::cerr << "outputs: " << outputs.size() << "\n");

	// 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.
	for (Values::const_iterator I = outputs.begin(), E = outputs.end();
	I != E; ++I) {
	DEBUG(std::cerr << "instr used in func: " << *I << "\n");
	if (AggregateArgs)
	paramTy.push_back((*I)->getType());
	else
	paramTy.push_back(PointerType::get((*I)->getType()));
	}

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

	if (AggregateArgs && (inputs.size() + outputs.size() > 0)) {
	PointerType *StructPtr = PointerType::get(StructType::get(paramTy));
	paramTy.clear();
	paramTy.push_back(StructPtr);
	}
	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);

	// Create an iterator to name all of the arguments we inserted.
	Function::aiterator AI = newFunction->abegin();

	// 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) {
	std::vector<Value*> Indices;
	Indices.push_back(Constant::getNullValue(Type::UIntTy));
	Indices.push_back(ConstantUInt::get(Type::UIntTy, i));
	std::string GEPname = "gep_" + inputs[i]->getName();
	TerminatorInst *TI = newFunction->begin()->getTerminator();
	GetElementPtrInst *GEP = new GetElementPtrInst(AI, Indices, 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->abegin();
	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;
	}

	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 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) {
	std::vector<Value*> Indices;
	Indices.push_back(Constant::getNullValue(Type::UIntTy));
	Indices.push_back(ConstantUInt::get(Type::UIntTy, i));
	GetElementPtrInst *GEP =
	new GetElementPtrInst(Struct, Indices,
	"gep_" + StructValues[i]->getName(), 0);
	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 = new CallInst(newFunction, params, "targetBlock");
	codeReplacer->getInstList().push_back(call);

	Function::aiterator OutputArgBegin = newFunction->abegin();
	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) {
	std::vector<Value*> Indices;
	Indices.push_back(Constant::getNullValue(Type::UIntTy));
	Indices.push_back(ConstantUInt::get(Type::UIntTy, FirstOut + i));
	GetElementPtrInst *GEP
	= new GetElementPtrInst(Struct, Indices,
	"gep_reload_" + outputs[i]->getName(), 0);
	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 = 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
	Function::aiterator 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();
	if (InvokeInst *Invoke = dyn_cast<InvokeInst>(outputs[out]))
	DefBlock = Invoke->getNormalDest();
	if (!DS \|\| DS->dominates(DefBlock, TI->getParent()))
	if (AggregateArgs) {
	std::vector<Value*> Indices;
	Indices.push_back(Constant::getNullValue(Type::UIntTy));
	Indices.push_back(ConstantUInt::get(Type::UIntTy,FirstOut+out));
	GetElementPtrInst *GEP =
	new GetElementPtrInst(OAI, Indices,
	"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.
	unsigned NumSuccs = TheSwitch->getNumSuccessors();
	if (NumSuccs > 1) {
	if (NumSuccs-1 == 1) {
	// Only a single destination, change the switch into an unconditional
	// branch.
	new BranchInst(TheSwitch->getSuccessor(1), TheSwitch);
	TheSwitch->getParent()->getInstList().erase(TheSwitch);
	} else {
	// Otherwise, make the default destination of the switch instruction be
	// one of the other successors.
	TheSwitch->setSuccessor(0, TheSwitch->getSuccessor(NumSuccs-1));
	TheSwitch->removeCase(NumSuccs-1); // Remove redundant case
	}
	} else {
	// There is only 1 successor (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 (TheSwitch->getParent()->getParent()->getReturnType() != Type::VoidTy &&
	TheSwitch->getParent()->getParent()->getReturnType() ==
	TheSwitch->getCondition()->getType())
	// return what we have
	new ReturnInst(TheSwitch->getCondition(), TheSwitch);
	else
	// just return
	new ReturnInst(0, TheSwitch);

	TheSwitch->getParent()->getInstList().erase(TheSwitch);
	}
	}


	/// 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!");

	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, code[0],
	newFuncRoot,
	codeReplacer, oldFunction,
	oldFunction->getParent());

	emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs);

	moveCodeToFunction(newFunction);

	// Loop over all of the PHI nodes in the entry block (code[0]), and change any
	// references to the old incoming edge to be the new incoming edge.
	for (BasicBlock::iterator I = code[0]->begin();
	PHINode *PN = dyn_cast<PHINode>(I); ++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();
	PHINode *PN = dyn_cast<PHINode>(I); ++I)
	for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
	if (BlocksToExtract.count(PN->getIncomingBlock(i)))
	PN->setIncomingBlock(i, codeReplacer);


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

	bool CodeExtractor::isEligible(const std::vector<BasicBlock*> &code) {
	// Deny code region if it contains allocas
	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;
	return true;
	}


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

	/// ExtractBasicBlock - slurp a natural loop into a brand new function
	///
	Function* llvm::ExtractLoop(DominatorSet &DS, Loop *L, bool AggregateArgs) {
	return CodeExtractor(&DS, 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);
	}