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

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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/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/IntrinsicInst.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;
// taking the address of a basic block moved to another function is illegal
if (BB.hasAddressTaken())
return false;
// don't hoist code that uses another basicblock address, as it's likely to
// lead to unexpected behavior, like cross-function jumps
SmallPtrSet<User const *, 16> Visited;
SmallVector<User const *, 16> ToVisit;
for (Instruction const &Inst : BB)
ToVisit.push_back(&Inst);
while (!ToVisit.empty()) {
User const *Curr = ToVisit.pop_back_val();
if (!Visited.insert(Curr).second)
continue;
if (isa<BlockAddress const>(Curr))
return false; // even a reference to self is likely to be not compatible
if (isa<Instruction>(Curr) && cast<Instruction>(Curr)->getParent() != &BB)
continue;
for (auto const &U : Curr->operands()) {
if (auto *UU = dyn_cast<User>(U))
ToVisit.push_back(UU);
}
}
// 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.
static SetVector<BasicBlock *>
buildExtractionBlockSet(ArrayRef<BasicBlock *> BBs, DominatorTree *DT) {
assert(!BBs.empty() && "The set of blocks to extract must be non-empty");
SetVector<BasicBlock *> Result;
// Loop over the blocks, adding them to our set-vector, and aborting with an
// empty set if we encounter invalid blocks.
for (BasicBlock *BB : BBs) {
// If this block is dead, don't process it.
if (DT && !DT->isReachableFromEntry(BB))
continue;
if (!Result.insert(BB))
llvm_unreachable("Repeated basic blocks in extraction input");
if (!CodeExtractor::isBlockValidForExtraction(*BB)) {
Result.clear();
return Result;
}
}
#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;
}
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, DT)), 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(), &DT)),
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;
}
static BasicBlock *getCommonExitBlock(const SetVector<BasicBlock *> &Blocks) {
BasicBlock *CommonExitBlock = nullptr;
auto hasNonCommonExitSucc = [&](BasicBlock *Block) {
for (auto *Succ : successors(Block)) {
// Internal edges, ok.
if (Blocks.count(Succ))
continue;
if (!CommonExitBlock) {
CommonExitBlock = Succ;
continue;
}
if (CommonExitBlock == Succ)
continue;
return true;
}
return false;
};
if (any_of(Blocks, hasNonCommonExitSucc))
return nullptr;
return CommonExitBlock;
}
bool CodeExtractor::isLegalToShrinkwrapLifetimeMarkers(
Instruction *Addr) const {
AllocaInst *AI = cast<AllocaInst>(Addr->stripInBoundsConstantOffsets());
Function *Func = (*Blocks.begin())->getParent();
for (BasicBlock &BB : *Func) {
if (Blocks.count(&BB))
continue;
for (Instruction &II : BB) {
if (isa<DbgInfoIntrinsic>(II))
continue;
unsigned Opcode = II.getOpcode();
Value *MemAddr = nullptr;
switch (Opcode) {
case Instruction::Store:
case Instruction::Load: {
if (Opcode == Instruction::Store) {
StoreInst *SI = cast<StoreInst>(&II);
MemAddr = SI->getPointerOperand();
} else {
LoadInst *LI = cast<LoadInst>(&II);
MemAddr = LI->getPointerOperand();
}
// Global variable can not be aliased with locals.
if (dyn_cast<Constant>(MemAddr))
break;
Value *Base = MemAddr->stripInBoundsConstantOffsets();
if (!dyn_cast<AllocaInst>(Base) || Base == AI)
return false;
break;
}
default: {
IntrinsicInst *IntrInst = dyn_cast<IntrinsicInst>(&II);
if (IntrInst) {
if (IntrInst->getIntrinsicID() == Intrinsic::lifetime_start ||
IntrInst->getIntrinsicID() == Intrinsic::lifetime_end)
break;
return false;
}
// Treat all the other cases conservatively if it has side effects.
if (II.mayHaveSideEffects())
return false;
}
}
}
}
return true;
}
BasicBlock *
CodeExtractor::findOrCreateBlockForHoisting(BasicBlock *CommonExitBlock) {
BasicBlock *SinglePredFromOutlineRegion = nullptr;
assert(!Blocks.count(CommonExitBlock) &&
"Expect a block outside the region!");
for (auto *Pred : predecessors(CommonExitBlock)) {
if (!Blocks.count(Pred))
continue;
if (!SinglePredFromOutlineRegion) {
SinglePredFromOutlineRegion = Pred;
} else if (SinglePredFromOutlineRegion != Pred) {
SinglePredFromOutlineRegion = nullptr;
break;
}
}
if (SinglePredFromOutlineRegion)
return SinglePredFromOutlineRegion;
#ifndef NDEBUG
auto getFirstPHI = [](BasicBlock *BB) {
BasicBlock::iterator I = BB->begin();
PHINode *FirstPhi = nullptr;
while (I != BB->end()) {
PHINode *Phi = dyn_cast<PHINode>(I);
if (!Phi)
break;
if (!FirstPhi) {
FirstPhi = Phi;
break;
}
}
return FirstPhi;
};
// If there are any phi nodes, the single pred either exists or has already
// be created before code extraction.
assert(!getFirstPHI(CommonExitBlock) && "Phi not expected");
#endif
BasicBlock *NewExitBlock = CommonExitBlock->splitBasicBlock(
CommonExitBlock->getFirstNonPHI()->getIterator());
for (auto *Pred : predecessors(CommonExitBlock)) {
if (Blocks.count(Pred))
continue;
Pred->getTerminator()->replaceUsesOfWith(CommonExitBlock, NewExitBlock);
}
// Now add the old exit block to the outline region.
Blocks.insert(CommonExitBlock);
return CommonExitBlock;
}
void CodeExtractor::findAllocas(ValueSet &SinkCands, ValueSet &HoistCands,
BasicBlock *&ExitBlock) const {
Function *Func = (*Blocks.begin())->getParent();
ExitBlock = getCommonExitBlock(Blocks);
for (BasicBlock &BB : *Func) {
if (Blocks.count(&BB))
continue;
for (Instruction &II : BB) {
auto *AI = dyn_cast<AllocaInst>(&II);
if (!AI)
continue;
// Find the pair of life time markers for address 'Addr' that are either
// defined inside the outline region or can legally be shrinkwrapped into
// the outline region. If there are not other untracked uses of the
// address, return the pair of markers if found; otherwise return a pair
// of nullptr.
auto GetLifeTimeMarkers =
[&](Instruction *Addr, bool &SinkLifeStart,
bool &HoistLifeEnd) -> std::pair<Instruction *, Instruction *> {
Instruction *LifeStart = nullptr, *LifeEnd = nullptr;
for (User *U : Addr->users()) {
IntrinsicInst *IntrInst = dyn_cast<IntrinsicInst>(U);
if (IntrInst) {
if (IntrInst->getIntrinsicID() == Intrinsic::lifetime_start) {
// Do not handle the case where AI has multiple start markers.
if (LifeStart)
return std::make_pair<Instruction *>(nullptr, nullptr);
LifeStart = IntrInst;
}
if (IntrInst->getIntrinsicID() == Intrinsic::lifetime_end) {
if (LifeEnd)
return std::make_pair<Instruction *>(nullptr, nullptr);
LifeEnd = IntrInst;
}
continue;
}
// Find untracked uses of the address, bail.
if (!definedInRegion(Blocks, U))
return std::make_pair<Instruction *>(nullptr, nullptr);
}
if (!LifeStart || !LifeEnd)
return std::make_pair<Instruction *>(nullptr, nullptr);
SinkLifeStart = !definedInRegion(Blocks, LifeStart);
HoistLifeEnd = !definedInRegion(Blocks, LifeEnd);
// Do legality Check.
if ((SinkLifeStart || HoistLifeEnd) &&
!isLegalToShrinkwrapLifetimeMarkers(Addr))
return std::make_pair<Instruction *>(nullptr, nullptr);
// Check to see if we have a place to do hoisting, if not, bail.
if (HoistLifeEnd && !ExitBlock)
return std::make_pair<Instruction *>(nullptr, nullptr);
return std::make_pair(LifeStart, LifeEnd);
};
bool SinkLifeStart = false, HoistLifeEnd = false;
auto Markers = GetLifeTimeMarkers(AI, SinkLifeStart, HoistLifeEnd);
if (Markers.first) {
if (SinkLifeStart)
SinkCands.insert(Markers.first);
SinkCands.insert(AI);
if (HoistLifeEnd)
HoistCands.insert(Markers.second);
continue;
}
// Follow the bitcast.
Instruction *MarkerAddr = nullptr;
for (User *U : AI->users()) {
if (U->stripInBoundsConstantOffsets() == AI) {
SinkLifeStart = false;
HoistLifeEnd = false;
Instruction *Bitcast = cast<Instruction>(U);
Markers = GetLifeTimeMarkers(Bitcast, SinkLifeStart, HoistLifeEnd);
if (Markers.first) {
MarkerAddr = Bitcast;
continue;
}
}
// Found unknown use of AI.
if (!definedInRegion(Blocks, U)) {
MarkerAddr = nullptr;
break;
}
}
if (MarkerAddr) {
if (SinkLifeStart)
SinkCands.insert(Markers.first);
if (!definedInRegion(Blocks, MarkerAddr))
SinkCands.insert(MarkerAddr);
SinkCands.insert(AI);
if (HoistLifeEnd)
HoistCands.insert(Markers.second);
}
}
}
}
void CodeExtractor::findInputsOutputs(ValueSet &Inputs, ValueSet &Outputs,
const ValueSet &SinkCands) 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) {
Value *V = *OI;
if (!SinkCands.count(V) && definedInCaller(Blocks, V))
Inputs.insert(V);
}
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 *NewBB = llvm::SplitBlock(Header, Header->getFirstNonPHI(), DT);
// 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, 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.
BasicBlock::iterator AfterPHIs;
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());
PN->replaceAllUsesWith(NewPN);
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.
AttrBuilder AB(oldFunction->getAttributes().getFnAttributes());
for (const 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;
Module *M = newFunction->getParent();
LLVMContext &Context = M->getContext();
const DataLayout &DL = M->getDataLayout();
// 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(), DL.getAllocaAddrSpace(),
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, DL.getAllocaAddrSpace(), 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, SinkingCands, HoistingCands;
BasicBlock *CommonExit = nullptr;
// 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));
findAllocas(SinkingCands, HoistingCands, CommonExit);
assert(HoistingCands.empty() || CommonExit);
// Find inputs to, outputs from the code region.
findInputsOutputs(inputs, outputs, SinkingCands);
// Now sink all instructions which only have non-phi uses inside the region
for (auto *II : SinkingCands)
cast<Instruction>(II)->moveBefore(*newFuncRoot,
newFuncRoot->getFirstInsertionPt());
if (!HoistingCands.empty()) {
auto *HoistToBlock = findOrCreateBlockForHoisting(CommonExit);
Instruction *TI = HoistToBlock->getTerminator();
for (auto *II : HoistingCands)
cast<Instruction>(II)->moveBefore(TI);
}
// 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;
}
}
}
DEBUG(if (verifyFunction(*newFunction))
report_fatal_error("verifyFunction failed!"));
return newFunction;
}
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