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Diffstat (limited to 'contrib/llvm/lib/Transforms/Utils/CodeExtractor.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/Utils/CodeExtractor.cpp | 875 |
1 files changed, 875 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Transforms/Utils/CodeExtractor.cpp b/contrib/llvm/lib/Transforms/Utils/CodeExtractor.cpp new file mode 100644 index 000000000000..c514c9c9cd4a --- /dev/null +++ b/contrib/llvm/lib/Transforms/Utils/CodeExtractor.cpp @@ -0,0 +1,875 @@ +//===- 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/CodeExtractor.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/SetVector.h" +#include "llvm/ADT/StringExtras.h" +#include "llvm/Analysis/BlockFrequencyInfo.h" +#include "llvm/Analysis/BlockFrequencyInfoImpl.h" +#include "llvm/Analysis/BranchProbabilityInfo.h" +#include "llvm/Analysis/LoopInfo.h" +#include "llvm/Analysis/RegionInfo.h" +#include "llvm/Analysis/RegionIterator.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/DerivedTypes.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/Intrinsics.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/MDBuilder.h" +#include "llvm/IR/Module.h" +#include "llvm/IR/Verifier.h" +#include "llvm/Pass.h" +#include "llvm/Support/BlockFrequency.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Transforms/Utils/BasicBlockUtils.h" +#include <algorithm> +#include <set> +using namespace llvm; + +#define DEBUG_TYPE "code-extractor" + +// 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")); + +/// \brief Test whether a block is valid for extraction. +bool CodeExtractor::isBlockValidForExtraction(const BasicBlock &BB) { + // Landing pads must be in the function where they were inserted for cleanup. + if (BB.isEHPad()) + return false; + + // Don't hoist code containing allocas, invokes, or vastarts. + for (BasicBlock::const_iterator I = BB.begin(), E = BB.end(); I != E; ++I) { + if (isa<AllocaInst>(I) || isa<InvokeInst>(I)) + return false; + if (const CallInst *CI = dyn_cast<CallInst>(I)) + if (const Function *F = CI->getCalledFunction()) + if (F->getIntrinsicID() == Intrinsic::vastart) + return false; + } + + return true; +} + +/// \brief Build a set of blocks to extract if the input blocks are viable. +template <typename IteratorT> +static SetVector<BasicBlock *> buildExtractionBlockSet(IteratorT BBBegin, + IteratorT BBEnd) { + SetVector<BasicBlock *> Result; + + assert(BBBegin != BBEnd); + + // Loop over the blocks, adding them to our set-vector, and aborting with an + // empty set if we encounter invalid blocks. + do { + if (!Result.insert(*BBBegin)) + llvm_unreachable("Repeated basic blocks in extraction input"); + + if (!CodeExtractor::isBlockValidForExtraction(**BBBegin)) { + Result.clear(); + return Result; + } + } while (++BBBegin != BBEnd); + +#ifndef NDEBUG + for (SetVector<BasicBlock *>::iterator I = std::next(Result.begin()), + E = Result.end(); + I != E; ++I) + for (pred_iterator PI = pred_begin(*I), PE = pred_end(*I); + PI != PE; ++PI) + assert(Result.count(*PI) && + "No blocks in this region may have entries from outside the region" + " except for the first block!"); +#endif + + return Result; +} + +/// \brief Helper to call buildExtractionBlockSet with an ArrayRef. +static SetVector<BasicBlock *> +buildExtractionBlockSet(ArrayRef<BasicBlock *> BBs) { + return buildExtractionBlockSet(BBs.begin(), BBs.end()); +} + +/// \brief Helper to call buildExtractionBlockSet with a RegionNode. +static SetVector<BasicBlock *> +buildExtractionBlockSet(const RegionNode &RN) { + if (!RN.isSubRegion()) + // Just a single BasicBlock. + return buildExtractionBlockSet(RN.getNodeAs<BasicBlock>()); + + const Region &R = *RN.getNodeAs<Region>(); + + return buildExtractionBlockSet(R.block_begin(), R.block_end()); +} + +CodeExtractor::CodeExtractor(BasicBlock *BB, bool AggregateArgs, + BlockFrequencyInfo *BFI, + BranchProbabilityInfo *BPI) + : DT(nullptr), AggregateArgs(AggregateArgs || AggregateArgsOpt), BFI(BFI), + BPI(BPI), Blocks(buildExtractionBlockSet(BB)), NumExitBlocks(~0U) {} + +CodeExtractor::CodeExtractor(ArrayRef<BasicBlock *> BBs, DominatorTree *DT, + bool AggregateArgs, BlockFrequencyInfo *BFI, + BranchProbabilityInfo *BPI) + : DT(DT), AggregateArgs(AggregateArgs || AggregateArgsOpt), BFI(BFI), + BPI(BPI), Blocks(buildExtractionBlockSet(BBs)), NumExitBlocks(~0U) {} + +CodeExtractor::CodeExtractor(DominatorTree &DT, Loop &L, bool AggregateArgs, + BlockFrequencyInfo *BFI, + BranchProbabilityInfo *BPI) + : DT(&DT), AggregateArgs(AggregateArgs || AggregateArgsOpt), BFI(BFI), + BPI(BPI), Blocks(buildExtractionBlockSet(L.getBlocks())), + NumExitBlocks(~0U) {} + +CodeExtractor::CodeExtractor(DominatorTree &DT, const RegionNode &RN, + bool AggregateArgs, BlockFrequencyInfo *BFI, + BranchProbabilityInfo *BPI) + : DT(&DT), AggregateArgs(AggregateArgs || AggregateArgsOpt), BFI(BFI), + BPI(BPI), Blocks(buildExtractionBlockSet(RN)), NumExitBlocks(~0U) {} + +/// definedInRegion - Return true if the specified value is defined in the +/// extracted region. +static bool definedInRegion(const SetVector<BasicBlock *> &Blocks, Value *V) { + if (Instruction *I = dyn_cast<Instruction>(V)) + if (Blocks.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. +static bool definedInCaller(const SetVector<BasicBlock *> &Blocks, Value *V) { + if (isa<Argument>(V)) return true; + if (Instruction *I = dyn_cast<Instruction>(V)) + if (!Blocks.count(I->getParent())) + return true; + return false; +} + +void CodeExtractor::findInputsOutputs(ValueSet &Inputs, + ValueSet &Outputs) const { + for (BasicBlock *BB : Blocks) { + // 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 (Instruction &II : *BB) { + for (User::op_iterator OI = II.op_begin(), OE = II.op_end(); OI != OE; + ++OI) + if (definedInCaller(Blocks, *OI)) + Inputs.insert(*OI); + + for (User *U : II.users()) + if (!definedInRegion(Blocks, U)) { + Outputs.insert(&II); + break; + } + } + } +} + +/// 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) { + unsigned NumPredsFromRegion = 0; + 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 (Blocks.count(PN->getIncomingBlock(i))) + ++NumPredsFromRegion; + 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()->getIterator(); + 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; + Blocks.remove(OldPred); + Blocks.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 (NumPredsFromRegion) { + 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 (Blocks.count(PN->getIncomingBlock(i))) { + TerminatorInst *TI = PN->getIncomingBlock(i)->getTerminator(); + TI->replaceUsesOfWith(OldPred, NewBB); + } + + // Okay, everything 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(), 1 + NumPredsFromRegion, + PN->getName() + ".ce", &NewBB->front()); + 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 (Blocks.count(PN->getIncomingBlock(i))) { + NewPN->addIncoming(PN->getIncomingValue(i), PN->getIncomingBlock(i)); + PN->removeIncomingValue(i); + --i; + } + } + } + } +} + +void CodeExtractor::splitReturnBlocks() { + for (BasicBlock *Block : Blocks) + if (ReturnInst *RI = dyn_cast<ReturnInst>(Block->getTerminator())) { + BasicBlock *New = + Block->splitBasicBlock(RI->getIterator(), Block->getName() + ".ret"); + if (DT) { + // Old dominates New. New node dominates all other nodes dominated + // by Old. + DomTreeNode *OldNode = DT->getNode(Block); + SmallVector<DomTreeNode *, 8> Children(OldNode->begin(), + OldNode->end()); + + DomTreeNode *NewNode = DT->addNewBlock(New, Block); + + for (DomTreeNode *I : Children) + DT->changeImmediateDominator(I, NewNode); + } + } +} + +/// constructFunction - make a function based on inputs and outputs, as follows: +/// f(in0, ..., inN, out0, ..., outN) +/// +Function *CodeExtractor::constructFunction(const ValueSet &inputs, + const ValueSet &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<Type*> paramTy; + + // Add the types of the input values to the function's argument list + for (Value *value : inputs) { + 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 (Value *output : outputs) { + DEBUG(dbgs() << "instr used in func: " << *output << "\n"); + if (AggregateArgs) + paramTy.push_back(output->getType()); + else + paramTy.push_back(PointerType::getUnqual(output->getType())); + } + + DEBUG({ + dbgs() << "Function type: " << *RetTy << " f("; + for (Type *i : paramTy) + dbgs() << *i << ", "; + dbgs() << ")\n"; + }); + + StructType *StructTy; + if (AggregateArgs && (inputs.size() + outputs.size() > 0)) { + StructTy = StructType::get(M->getContext(), paramTy); + paramTy.clear(); + paramTy.push_back(PointerType::getUnqual(StructTy)); + } + 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(); + + // Inherit the uwtable attribute if we need to. + if (oldFunction->hasUWTable()) + newFunction->setHasUWTable(); + + // Inherit all of the target dependent attributes. + // (e.g. If the extracted region contains a call to an x86.sse + // instruction we need to make sure that the extracted region has the + // "target-features" attribute allowing it to be lowered. + // FIXME: This should be changed to check to see if a specific + // attribute can not be inherited. + AttributeSet OldFnAttrs = oldFunction->getAttributes().getFnAttributes(); + AttrBuilder AB(OldFnAttrs, AttributeSet::FunctionIndex); + for (auto Attr : AB.td_attrs()) + newFunction->addFnAttr(Attr.first, Attr.second); + + 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( + StructTy, &*AI, Idx, "gep_" + inputs[i]->getName(), TI); + RewriteVal = new LoadInst(GEP, "loadgep_" + inputs[i]->getName(), TI); + } else + RewriteVal = &*AI++; + + std::vector<User*> Users(inputs[i]->user_begin(), inputs[i]->user_end()); + for (User *use : Users) + if (Instruction *inst = dyn_cast<Instruction>(use)) + if (Blocks.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->user_begin(), header->user_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 (!Blocks.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 (Use &U : Used->uses()) { + PHINode *P = dyn_cast<PHINode>(U.getUser()); + if (P && P->getParent() == BB) + return P->getIncomingBlock(U); + } + + return nullptr; +} + +/// 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, + ValueSet &inputs, ValueSet &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 (Value *input : inputs) + if (AggregateArgs) + StructValues.push_back(input); + else + params.push_back(input); + + // Create allocas for the outputs + for (Value *output : outputs) { + if (AggregateArgs) { + StructValues.push_back(output); + } else { + AllocaInst *alloca = + new AllocaInst(output->getType(), nullptr, output->getName() + ".loc", + &codeReplacer->getParent()->front().front()); + ReloadOutputs.push_back(alloca); + params.push_back(alloca); + } + } + + StructType *StructArgTy = nullptr; + AllocaInst *Struct = nullptr; + if (AggregateArgs && (inputs.size() + outputs.size() > 0)) { + std::vector<Type*> ArgTypes; + for (ValueSet::iterator v = StructValues.begin(), + ve = StructValues.end(); v != ve; ++v) + ArgTypes.push_back((*v)->getType()); + + // Allocate a struct at the beginning of this function + StructArgTy = StructType::get(newFunction->getContext(), ArgTypes); + Struct = new AllocaInst(StructArgTy, nullptr, "structArg", + &codeReplacer->getParent()->front().front()); + 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( + StructArgTy, Struct, Idx, "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, + 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 = nullptr; + 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( + StructArgTy, Struct, Idx, "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]->user_begin(), outputs[i]->user_end()); + for (unsigned u = 0, e = Users.size(); u != e; ++u) { + Instruction *inst = cast<Instruction>(Users[u]); + if (!Blocks.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 (BasicBlock *Block : Blocks) { + TerminatorInst *TI = Block->getTerminator(); + for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) + if (!Blocks.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 = nullptr; + 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; + + BasicBlock *NormalDest = nullptr; + if (auto *Invoke = dyn_cast<InvokeInst>(outputs[out])) + NormalDest = Invoke->getNormalDest(); + + if (NormalDest) { + DefBlock = NormalDest; + + // 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 (const auto &I : ExitBlockMap) + 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( + StructArgTy, &*OAI, Idx, "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. + 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, nullptr, 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->setCondition(call); + TheSwitch->setDefaultDest(TheSwitch->getSuccessor(NumExitBlocks)); + // Remove redundant case + TheSwitch->removeCase(SwitchInst::CaseIt(TheSwitch, NumExitBlocks-1)); + break; + } +} + +void CodeExtractor::moveCodeToFunction(Function *newFunction) { + Function *oldFunc = (*Blocks.begin())->getParent(); + Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList(); + Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList(); + + for (BasicBlock *Block : Blocks) { + // Delete the basic block from the old function, and the list of blocks + oldBlocks.remove(Block); + + // Insert this basic block into the new function + newBlocks.push_back(Block); + } +} + +void CodeExtractor::calculateNewCallTerminatorWeights( + BasicBlock *CodeReplacer, + DenseMap<BasicBlock *, BlockFrequency> &ExitWeights, + BranchProbabilityInfo *BPI) { + typedef BlockFrequencyInfoImplBase::Distribution Distribution; + typedef BlockFrequencyInfoImplBase::BlockNode BlockNode; + + // Update the branch weights for the exit block. + TerminatorInst *TI = CodeReplacer->getTerminator(); + SmallVector<unsigned, 8> BranchWeights(TI->getNumSuccessors(), 0); + + // Block Frequency distribution with dummy node. + Distribution BranchDist; + + // Add each of the frequencies of the successors. + for (unsigned i = 0, e = TI->getNumSuccessors(); i < e; ++i) { + BlockNode ExitNode(i); + uint64_t ExitFreq = ExitWeights[TI->getSuccessor(i)].getFrequency(); + if (ExitFreq != 0) + BranchDist.addExit(ExitNode, ExitFreq); + else + BPI->setEdgeProbability(CodeReplacer, i, BranchProbability::getZero()); + } + + // Check for no total weight. + if (BranchDist.Total == 0) + return; + + // Normalize the distribution so that they can fit in unsigned. + BranchDist.normalize(); + + // Create normalized branch weights and set the metadata. + for (unsigned I = 0, E = BranchDist.Weights.size(); I < E; ++I) { + const auto &Weight = BranchDist.Weights[I]; + + // Get the weight and update the current BFI. + BranchWeights[Weight.TargetNode.Index] = Weight.Amount; + BranchProbability BP(Weight.Amount, BranchDist.Total); + BPI->setEdgeProbability(CodeReplacer, Weight.TargetNode.Index, BP); + } + TI->setMetadata( + LLVMContext::MD_prof, + MDBuilder(TI->getContext()).createBranchWeights(BranchWeights)); +} + +Function *CodeExtractor::extractCodeRegion() { + if (!isEligible()) + return nullptr; + + ValueSet inputs, outputs; + + // Assumption: this is a single-entry code region, and the header is the first + // block in the region. + BasicBlock *header = *Blocks.begin(); + + // Calculate the entry frequency of the new function before we change the root + // block. + BlockFrequency EntryFreq; + if (BFI) { + assert(BPI && "Both BPI and BFI are required to preserve profile info"); + for (BasicBlock *Pred : predecessors(header)) { + if (Blocks.count(Pred)) + continue; + EntryFreq += + BFI->getBlockFreq(Pred) * BPI->getEdgeProbability(Pred, header); + } + } + + // 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); + + // Calculate the exit blocks for the extracted region and the total exit + // weights for each of those blocks. + DenseMap<BasicBlock *, BlockFrequency> ExitWeights; + SmallPtrSet<BasicBlock *, 1> ExitBlocks; + for (BasicBlock *Block : Blocks) { + for (succ_iterator SI = succ_begin(Block), SE = succ_end(Block); SI != SE; + ++SI) { + if (!Blocks.count(*SI)) { + // Update the branch weight for this successor. + if (BFI) { + BlockFrequency &BF = ExitWeights[*SI]; + BF += BFI->getBlockFreq(Block) * BPI->getEdgeProbability(Block, *SI); + } + ExitBlocks.insert(*SI); + } + } + } + NumExitBlocks = ExitBlocks.size(); + + // Construct new function based on inputs/outputs & add allocas for all defs. + Function *newFunction = constructFunction(inputs, outputs, header, + newFuncRoot, + codeReplacer, oldFunction, + oldFunction->getParent()); + + // Update the entry count of the function. + if (BFI) { + Optional<uint64_t> EntryCount = + BFI->getProfileCountFromFreq(EntryFreq.getFrequency()); + if (EntryCount.hasValue()) + newFunction->setEntryCount(EntryCount.getValue()); + BFI->setBlockFreq(codeReplacer, EntryFreq.getFrequency()); + } + + emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs); + + moveCodeToFunction(newFunction); + + // Update the branch weights for the exit block. + if (BFI && NumExitBlocks > 1) + calculateNewCallTerminatorWeights(codeReplacer, ExitWeights, BPI); + + // 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 (!Blocks.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 (Blocks.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; +} |