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llvm-mirror/lib/Transforms/Utils/CodeExtractor.cpp
Chris Lattner 80b41881bc rename llvm::llvm_report_error -> llvm::report_fatal_error 
llvm-svn: 100709
2010-04-07 22:58:41 +00:00

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//===- 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/LLVMContext.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/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/SetVector.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 CodeExtractor {
typedef SetVector<Value*> Values;
SetVector<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.remove(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 (SetVector<BasicBlock*>::iterator I = BlocksToExtract.begin(),
E = BlocksToExtract.end(); I != E; ++I)
if (ReturnInst *RI = dyn_cast<ReturnInst>((*I)->getTerminator())) {
BasicBlock *New = (*I)->splitBasicBlock(RI, (*I)->getName()+".ret");
if (DT) {
// Old dominates New. New node domiantes all other nodes dominated
//by Old.
DomTreeNode *OldNode = DT->getNode(*I);
SmallVector<DomTreeNode*, 8> Children;
for (DomTreeNode::iterator DI = OldNode->begin(), DE = OldNode->end();
DI != DE; ++DI)
Children.push_back(*DI);
DomTreeNode *NewNode = DT->addNewBlock(New, *I);
for (SmallVector<DomTreeNode*, 8>::iterator I = Children.begin(),
E = Children.end(); I != E; ++I)
DT->changeImmediateDominator(*I, NewNode);
}
}
}
// findInputsOutputs - Find inputs to, outputs from the code region.
//
void CodeExtractor::findInputsOutputs(Values &inputs, Values &outputs) {
std::set<BasicBlock*> ExitBlocks;
for (SetVector<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.insert(*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.insert(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();
}
/// 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(dbgs() << "inputs: " << inputs.size() << "\n");
DEBUG(dbgs() << "outputs: " << outputs.size() << "\n");
// This function returns unsigned, outputs will go back by reference.
switch (NumExitBlocks) {
case 0:
case 1: RetTy = Type::getVoidTy(header->getContext()); break;
case 2: RetTy = Type::getInt1Ty(header->getContext()); break;
default: RetTy = Type::getInt16Ty(header->getContext()); 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;
DEBUG(dbgs() << "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(dbgs() << "instr used in func: " << **I << "\n");
if (AggregateArgs)
paramTy.push_back((*I)->getType());
else
paramTy.push_back(PointerType::getUnqual((*I)->getType()));
}
DEBUG(dbgs() << "Function type: " << *RetTy << " f(");
for (std::vector<const Type*>::iterator i = paramTy.begin(),
e = paramTy.end(); i != e; ++i)
DEBUG(dbgs() << **i << ", ");
DEBUG(dbgs() << ")\n");
if (AggregateArgs && (inputs.size() + outputs.size() > 0)) {
PointerType *StructPtr =
PointerType::getUnqual(StructType::get(M->getContext(), 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::getInt32Ty(header->getContext()));
Idx[1] = ConstantInt::get(Type::getInt32Ty(header->getContext()), i);
TerminatorInst *TI = newFunction->begin()->getTerminator();
GetElementPtrInst *GEP =
GetElementPtrInst::Create(AI, Idx, Idx+2,
"gep_" + inputs[i]->getName(), TI);
RewriteVal = new LoadInst(GEP, "loadgep_" + inputs[i]->getName(), 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;
}
/// FindPhiPredForUseInBlock - Given a value and a basic block, find a PHI
/// that uses the value within the basic block, and return the predecessor
/// block associated with that use, or return 0 if none is found.
static BasicBlock* FindPhiPredForUseInBlock(Value* Used, BasicBlock* BB) {
for (Value::use_iterator UI = Used->use_begin(),
UE = Used->use_end(); UI != UE; ++UI) {
PHINode *P = dyn_cast<PHINode>(*UI);
if (P && P->getParent() == BB)
return P->getIncomingBlock(UI);
}
return 0;
}
/// 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, Reloads;
LLVMContext &Context = newFunction->getContext();
// 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(newFunction->getContext(), 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::getInt32Ty(Context));
Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), 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::getInt32Ty(Context));
Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), 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");
Reloads.push_back(load);
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(Constant::getNullValue(Type::getInt16Ty(Context)),
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 (SetVector<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(Context,
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::getInt1Ty(Context), !SuccNum);
break;
default:
brVal = ConstantInt::get(Type::getInt16Ty(Context), SuccNum);
break;
}
ReturnInst *NTRet = ReturnInst::Create(Context, brVal, NewTarget);
// Update the switch instruction.
TheSwitch->addCase(ConstantInt::get(Type::getInt16Ty(Context),
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 the output value is used by a phi in the target block,
// then we need to test for dominance of the phi's predecessor
// instead. Unfortunately, this a little complicated since we
// have already rewritten uses of the value to uses of the reload.
BasicBlock* pred = FindPhiPredForUseInBlock(Reloads[out],
OldTarget);
if (pred && DT && DT->dominates(DefBlock, pred))
DominatesDef = true;
}
if (DominatesDef) {
if (AggregateArgs) {
Value *Idx[2];
Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context));
Idx[1] = ConstantInt::get(Type::getInt32Ty(Context),
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->isVoidTy()) {
ReturnInst::Create(Context, 0, TheSwitch); // Return void
} else if (OldFnRetTy == TheSwitch->getCondition()->getType()) {
// return what we have
ReturnInst::Create(Context, TheSwitch->getCondition(), TheSwitch);
} else {
// Otherwise we must have code extracted an unwind or something, just
// return whatever we want.
ReturnInst::Create(Context,
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 (SetVector<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(header->getContext(),
"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(header->getContext(),
"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))
report_fatal_error("verifyFunction failed!"));
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);
}
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