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llvm-for-llvmta/lib/Transforms/Utils/CodeExtractor.cpp

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2022-04-25 10:02:23 +02:00
//===- CodeExtractor.cpp - Pull code region into a new function -----------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// 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/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/BlockFrequencyInfoImpl.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.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/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/Verifier.h"
#include "llvm/Pass.h"
#include "llvm/Support/BlockFrequency.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/Casting.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 "llvm/Transforms/Utils/Local.h"
#include <cassert>
#include <cstdint>
#include <iterator>
#include <map>
#include <set>
#include <utility>
#include <vector>
using namespace llvm;
using namespace llvm::PatternMatch;
using ProfileCount = Function::ProfileCount;
#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"));
/// Test whether a block is valid for extraction.
static bool isBlockValidForExtraction(const BasicBlock &BB,
const SetVector<BasicBlock *> &Result,
bool AllowVarArgs, bool AllowAlloca) {
// 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);
}
}
// If explicitly requested, allow vastart and alloca. For invoke instructions
// verify that extraction is valid.
for (BasicBlock::const_iterator I = BB.begin(), E = BB.end(); I != E; ++I) {
if (isa<AllocaInst>(I)) {
if (!AllowAlloca)
return false;
continue;
}
if (const auto *II = dyn_cast<InvokeInst>(I)) {
// Unwind destination (either a landingpad, catchswitch, or cleanuppad)
// must be a part of the subgraph which is being extracted.
if (auto *UBB = II->getUnwindDest())
if (!Result.count(UBB))
return false;
continue;
}
// All catch handlers of a catchswitch instruction as well as the unwind
// destination must be in the subgraph.
if (const auto *CSI = dyn_cast<CatchSwitchInst>(I)) {
if (auto *UBB = CSI->getUnwindDest())
if (!Result.count(UBB))
return false;
for (auto *HBB : CSI->handlers())
if (!Result.count(const_cast<BasicBlock*>(HBB)))
return false;
continue;
}
// Make sure that entire catch handler is within subgraph. It is sufficient
// to check that catch return's block is in the list.
if (const auto *CPI = dyn_cast<CatchPadInst>(I)) {
for (const auto *U : CPI->users())
if (const auto *CRI = dyn_cast<CatchReturnInst>(U))
if (!Result.count(const_cast<BasicBlock*>(CRI->getParent())))
return false;
continue;
}
// And do similar checks for cleanup handler - the entire handler must be
// in subgraph which is going to be extracted. For cleanup return should
// additionally check that the unwind destination is also in the subgraph.
if (const auto *CPI = dyn_cast<CleanupPadInst>(I)) {
for (const auto *U : CPI->users())
if (const auto *CRI = dyn_cast<CleanupReturnInst>(U))
if (!Result.count(const_cast<BasicBlock*>(CRI->getParent())))
return false;
continue;
}
if (const auto *CRI = dyn_cast<CleanupReturnInst>(I)) {
if (auto *UBB = CRI->getUnwindDest())
if (!Result.count(UBB))
return false;
continue;
}
if (const CallInst *CI = dyn_cast<CallInst>(I)) {
if (const Function *F = CI->getCalledFunction()) {
auto IID = F->getIntrinsicID();
if (IID == Intrinsic::vastart) {
if (AllowVarArgs)
continue;
else
return false;
}
// Currently, we miscompile outlined copies of eh_typid_for. There are
// proposals for fixing this in llvm.org/PR39545.
if (IID == Intrinsic::eh_typeid_for)
return false;
}
}
}
return true;
}
/// Build a set of blocks to extract if the input blocks are viable.
static SetVector<BasicBlock *>
buildExtractionBlockSet(ArrayRef<BasicBlock *> BBs, DominatorTree *DT,
bool AllowVarArgs, bool AllowAlloca) {
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");
}
LLVM_DEBUG(dbgs() << "Region front block: " << Result.front()->getName()
<< '\n');
for (auto *BB : Result) {
if (!isBlockValidForExtraction(*BB, Result, AllowVarArgs, AllowAlloca))
return {};
// Make sure that the first block is not a landing pad.
if (BB == Result.front()) {
if (BB->isEHPad()) {
LLVM_DEBUG(dbgs() << "The first block cannot be an unwind block\n");
return {};
}
continue;
}
// All blocks other than the first must not have predecessors outside of
// the subgraph which is being extracted.
for (auto *PBB : predecessors(BB))
if (!Result.count(PBB)) {
LLVM_DEBUG(dbgs() << "No blocks in this region may have entries from "
"outside the region except for the first block!\n"
<< "Problematic source BB: " << BB->getName() << "\n"
<< "Problematic destination BB: " << PBB->getName()
<< "\n");
return {};
}
}
return Result;
}
CodeExtractor::CodeExtractor(ArrayRef<BasicBlock *> BBs, DominatorTree *DT,
bool AggregateArgs, BlockFrequencyInfo *BFI,
BranchProbabilityInfo *BPI, AssumptionCache *AC,
bool AllowVarArgs, bool AllowAlloca,
std::string Suffix)
: DT(DT), AggregateArgs(AggregateArgs || AggregateArgsOpt), BFI(BFI),
BPI(BPI), AC(AC), AllowVarArgs(AllowVarArgs),
Blocks(buildExtractionBlockSet(BBs, DT, AllowVarArgs, AllowAlloca)),
Suffix(Suffix) {}
CodeExtractor::CodeExtractor(DominatorTree &DT, Loop &L, bool AggregateArgs,
BlockFrequencyInfo *BFI,
BranchProbabilityInfo *BPI, AssumptionCache *AC,
std::string Suffix)
: DT(&DT), AggregateArgs(AggregateArgs || AggregateArgsOpt), BFI(BFI),
BPI(BPI), AC(AC), AllowVarArgs(false),
Blocks(buildExtractionBlockSet(L.getBlocks(), &DT,
/* AllowVarArgs */ false,
/* AllowAlloca */ false)),
Suffix(Suffix) {}
/// 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)
return true;
}
return false;
};
if (any_of(Blocks, hasNonCommonExitSucc))
return nullptr;
return CommonExitBlock;
}
CodeExtractorAnalysisCache::CodeExtractorAnalysisCache(Function &F) {
for (BasicBlock &BB : F) {
for (Instruction &II : BB.instructionsWithoutDebug())
if (auto *AI = dyn_cast<AllocaInst>(&II))
Allocas.push_back(AI);
findSideEffectInfoForBlock(BB);
}
}
void CodeExtractorAnalysisCache::findSideEffectInfoForBlock(BasicBlock &BB) {
for (Instruction &II : BB.instructionsWithoutDebug()) {
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 (!isa<AllocaInst>(Base)) {
SideEffectingBlocks.insert(&BB);
return;
}
BaseMemAddrs[&BB].insert(Base);
break;
}
default: {
IntrinsicInst *IntrInst = dyn_cast<IntrinsicInst>(&II);
if (IntrInst) {
if (IntrInst->isLifetimeStartOrEnd())
break;
SideEffectingBlocks.insert(&BB);
return;
}
// Treat all the other cases conservatively if it has side effects.
if (II.mayHaveSideEffects()) {
SideEffectingBlocks.insert(&BB);
return;
}
}
}
}
}
bool CodeExtractorAnalysisCache::doesBlockContainClobberOfAddr(
BasicBlock &BB, AllocaInst *Addr) const {
if (SideEffectingBlocks.count(&BB))
return true;
auto It = BaseMemAddrs.find(&BB);
if (It != BaseMemAddrs.end())
return It->second.count(Addr);
return false;
}
bool CodeExtractor::isLegalToShrinkwrapLifetimeMarkers(
const CodeExtractorAnalysisCache &CEAC, Instruction *Addr) const {
AllocaInst *AI = cast<AllocaInst>(Addr->stripInBoundsConstantOffsets());
Function *Func = (*Blocks.begin())->getParent();
for (BasicBlock &BB : *Func) {
if (Blocks.count(&BB))
continue;
if (CEAC.doesBlockContainClobberOfAddr(BB, AI))
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 PI = pred_begin(CommonExitBlock), PE = pred_end(CommonExitBlock);
PI != PE;) {
BasicBlock *Pred = *PI++;
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;
}
// 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.
CodeExtractor::LifetimeMarkerInfo
CodeExtractor::getLifetimeMarkers(const CodeExtractorAnalysisCache &CEAC,
Instruction *Addr,
BasicBlock *ExitBlock) const {
LifetimeMarkerInfo Info;
for (User *U : Addr->users()) {
IntrinsicInst *IntrInst = dyn_cast<IntrinsicInst>(U);
if (IntrInst) {
// We don't model addresses with multiple start/end markers, but the
// markers do not need to be in the region.
if (IntrInst->getIntrinsicID() == Intrinsic::lifetime_start) {
if (Info.LifeStart)
return {};
Info.LifeStart = IntrInst;
continue;
}
if (IntrInst->getIntrinsicID() == Intrinsic::lifetime_end) {
if (Info.LifeEnd)
return {};
Info.LifeEnd = IntrInst;
continue;
}
// At this point, permit debug uses outside of the region.
// This is fixed in a later call to fixupDebugInfoPostExtraction().
if (isa<DbgInfoIntrinsic>(IntrInst))
continue;
}
// Find untracked uses of the address, bail.
if (!definedInRegion(Blocks, U))
return {};
}
if (!Info.LifeStart || !Info.LifeEnd)
return {};
Info.SinkLifeStart = !definedInRegion(Blocks, Info.LifeStart);
Info.HoistLifeEnd = !definedInRegion(Blocks, Info.LifeEnd);
// Do legality check.
if ((Info.SinkLifeStart || Info.HoistLifeEnd) &&
!isLegalToShrinkwrapLifetimeMarkers(CEAC, Addr))
return {};
// Check to see if we have a place to do hoisting, if not, bail.
if (Info.HoistLifeEnd && !ExitBlock)
return {};
return Info;
}
void CodeExtractor::findAllocas(const CodeExtractorAnalysisCache &CEAC,
ValueSet &SinkCands, ValueSet &HoistCands,
BasicBlock *&ExitBlock) const {
Function *Func = (*Blocks.begin())->getParent();
ExitBlock = getCommonExitBlock(Blocks);
auto moveOrIgnoreLifetimeMarkers =
[&](const LifetimeMarkerInfo &LMI) -> bool {
if (!LMI.LifeStart)
return false;
if (LMI.SinkLifeStart) {
LLVM_DEBUG(dbgs() << "Sinking lifetime.start: " << *LMI.LifeStart
<< "\n");
SinkCands.insert(LMI.LifeStart);
}
if (LMI.HoistLifeEnd) {
LLVM_DEBUG(dbgs() << "Hoisting lifetime.end: " << *LMI.LifeEnd << "\n");
HoistCands.insert(LMI.LifeEnd);
}
return true;
};
// Look up allocas in the original function in CodeExtractorAnalysisCache, as
// this is much faster than walking all the instructions.
for (AllocaInst *AI : CEAC.getAllocas()) {
BasicBlock *BB = AI->getParent();
if (Blocks.count(BB))
continue;
// As a prior call to extractCodeRegion() may have shrinkwrapped the alloca,
// check whether it is actually still in the original function.
Function *AIFunc = BB->getParent();
if (AIFunc != Func)
continue;
LifetimeMarkerInfo MarkerInfo = getLifetimeMarkers(CEAC, AI, ExitBlock);
bool Moved = moveOrIgnoreLifetimeMarkers(MarkerInfo);
if (Moved) {
LLVM_DEBUG(dbgs() << "Sinking alloca: " << *AI << "\n");
SinkCands.insert(AI);
continue;
}
// Find bitcasts in the outlined region that have lifetime marker users
// outside that region. Replace the lifetime marker use with an
// outside region bitcast to avoid unnecessary alloca/reload instructions
// and extra lifetime markers.
SmallVector<Instruction *, 2> LifetimeBitcastUsers;
for (User *U : AI->users()) {
if (!definedInRegion(Blocks, U))
continue;
if (U->stripInBoundsConstantOffsets() != AI)
continue;
Instruction *Bitcast = cast<Instruction>(U);
for (User *BU : Bitcast->users()) {
IntrinsicInst *IntrInst = dyn_cast<IntrinsicInst>(BU);
if (!IntrInst)
continue;
if (!IntrInst->isLifetimeStartOrEnd())
continue;
if (definedInRegion(Blocks, IntrInst))
continue;
LLVM_DEBUG(dbgs() << "Replace use of extracted region bitcast"
<< *Bitcast << " in out-of-region lifetime marker "
<< *IntrInst << "\n");
LifetimeBitcastUsers.push_back(IntrInst);
}
}
for (Instruction *I : LifetimeBitcastUsers) {
Module *M = AIFunc->getParent();
LLVMContext &Ctx = M->getContext();
auto *Int8PtrTy = Type::getInt8PtrTy(Ctx);
CastInst *CastI =
CastInst::CreatePointerCast(AI, Int8PtrTy, "lt.cast", I);
I->replaceUsesOfWith(I->getOperand(1), CastI);
}
// Follow any bitcasts.
SmallVector<Instruction *, 2> Bitcasts;
SmallVector<LifetimeMarkerInfo, 2> BitcastLifetimeInfo;
for (User *U : AI->users()) {
if (U->stripInBoundsConstantOffsets() == AI) {
Instruction *Bitcast = cast<Instruction>(U);
LifetimeMarkerInfo LMI = getLifetimeMarkers(CEAC, Bitcast, ExitBlock);
if (LMI.LifeStart) {
Bitcasts.push_back(Bitcast);
BitcastLifetimeInfo.push_back(LMI);
continue;
}
}
// Found unknown use of AI.
if (!definedInRegion(Blocks, U)) {
Bitcasts.clear();
break;
}
}
// Either no bitcasts reference the alloca or there are unknown uses.
if (Bitcasts.empty())
continue;
LLVM_DEBUG(dbgs() << "Sinking alloca (via bitcast): " << *AI << "\n");
SinkCands.insert(AI);
for (unsigned I = 0, E = Bitcasts.size(); I != E; ++I) {
Instruction *BitcastAddr = Bitcasts[I];
const LifetimeMarkerInfo &LMI = BitcastLifetimeInfo[I];
assert(LMI.LifeStart &&
"Unsafe to sink bitcast without lifetime markers");
moveOrIgnoreLifetimeMarkers(LMI);
if (!definedInRegion(Blocks, BitcastAddr)) {
LLVM_DEBUG(dbgs() << "Sinking bitcast-of-alloca: " << *BitcastAddr
<< "\n");
SinkCands.insert(BitcastAddr);
}
}
}
}
bool CodeExtractor::isEligible() const {
if (Blocks.empty())
return false;
BasicBlock *Header = *Blocks.begin();
Function *F = Header->getParent();
// For functions with varargs, check that varargs handling is only done in the
// outlined function, i.e vastart and vaend are only used in outlined blocks.
if (AllowVarArgs && F->getFunctionType()->isVarArg()) {
auto containsVarArgIntrinsic = [](const Instruction &I) {
if (const CallInst *CI = dyn_cast<CallInst>(&I))
if (const Function *Callee = CI->getCalledFunction())
return Callee->getIntrinsicID() == Intrinsic::vastart ||
Callee->getIntrinsicID() == Intrinsic::vaend;
return false;
};
for (auto &BB : *F) {
if (Blocks.count(&BB))
continue;
if (llvm::any_of(BB, containsVarArgIntrinsic))
return false;
}
}
return true;
}
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 (auto &OI : II.operands()) {
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;
}
}
}
}
/// severSplitPHINodesOfEntry - 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::severSplitPHINodesOfEntry(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 = 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))) {
Instruction *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;
}
}
}
}
}
/// severSplitPHINodesOfExits - if PHI nodes in exit blocks have inputs from
/// outlined region, we split these PHIs on two: one with inputs from region
/// and other with remaining incoming blocks; then first PHIs are placed in
/// outlined region.
void CodeExtractor::severSplitPHINodesOfExits(
const SmallPtrSetImpl<BasicBlock *> &Exits) {
for (BasicBlock *ExitBB : Exits) {
BasicBlock *NewBB = nullptr;
for (PHINode &PN : ExitBB->phis()) {
// Find all incoming values from the outlining region.
SmallVector<unsigned, 2> IncomingVals;
for (unsigned i = 0; i < PN.getNumIncomingValues(); ++i)
if (Blocks.count(PN.getIncomingBlock(i)))
IncomingVals.push_back(i);
// Do not process PHI if there is one (or fewer) predecessor from region.
// If PHI has exactly one predecessor from region, only this one incoming
// will be replaced on codeRepl block, so it should be safe to skip PHI.
if (IncomingVals.size() <= 1)
continue;
// Create block for new PHIs and add it to the list of outlined if it
// wasn't done before.
if (!NewBB) {
NewBB = BasicBlock::Create(ExitBB->getContext(),
ExitBB->getName() + ".split",
ExitBB->getParent(), ExitBB);
SmallVector<BasicBlock *, 4> Preds(predecessors(ExitBB));
for (BasicBlock *PredBB : Preds)
if (Blocks.count(PredBB))
PredBB->getTerminator()->replaceUsesOfWith(ExitBB, NewBB);
BranchInst::Create(ExitBB, NewBB);
Blocks.insert(NewBB);
}
// Split this PHI.
PHINode *NewPN =
PHINode::Create(PN.getType(), IncomingVals.size(),
PN.getName() + ".ce", NewBB->getFirstNonPHI());
for (unsigned i : IncomingVals)
NewPN->addIncoming(PN.getIncomingValue(i), PN.getIncomingBlock(i));
for (unsigned i : reverse(IncomingVals))
PN.removeIncomingValue(i, false);
PN.addIncoming(NewPN, NewBB);
}
}
}
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) {
LLVM_DEBUG(dbgs() << "inputs: " << inputs.size() << "\n");
LLVM_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) {
LLVM_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) {
LLVM_DEBUG(dbgs() << "instr used in func: " << *output << "\n");
if (AggregateArgs)
paramTy.push_back(output->getType());
else
paramTy.push_back(PointerType::getUnqual(output->getType()));
}
LLVM_DEBUG({
dbgs() << "Function type: " << *RetTy << " f(";
for (Type *i : paramTy)
dbgs() << *i << ", ";
dbgs() << ")\n";
});
StructType *StructTy = nullptr;
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,
AllowVarArgs && oldFunction->isVarArg());
std::string SuffixToUse =
Suffix.empty()
? (header->getName().empty() ? "extracted" : header->getName().str())
: Suffix;
// Create the new function
Function *newFunction = Function::Create(
funcType, GlobalValue::InternalLinkage, oldFunction->getAddressSpace(),
oldFunction->getName() + "." + SuffixToUse, 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 and white-listed
// target independent 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.
for (const auto &Attr : oldFunction->getAttributes().getFnAttributes()) {
if (Attr.isStringAttribute()) {
if (Attr.getKindAsString() == "thunk")
continue;
} else
switch (Attr.getKindAsEnum()) {
// Those attributes cannot be propagated safely. Explicitly list them
// here so we get a warning if new attributes are added. This list also
// includes non-function attributes.
case Attribute::Alignment:
case Attribute::AllocSize:
case Attribute::ArgMemOnly:
case Attribute::Builtin:
case Attribute::ByVal:
case Attribute::Convergent:
case Attribute::Dereferenceable:
case Attribute::DereferenceableOrNull:
case Attribute::InAlloca:
case Attribute::InReg:
case Attribute::InaccessibleMemOnly:
case Attribute::InaccessibleMemOrArgMemOnly:
case Attribute::JumpTable:
case Attribute::Naked:
case Attribute::Nest:
case Attribute::NoAlias:
case Attribute::NoBuiltin:
case Attribute::NoCapture:
case Attribute::NoMerge:
case Attribute::NoReturn:
case Attribute::NoSync:
case Attribute::NoUndef:
case Attribute::None:
case Attribute::NonNull:
case Attribute::Preallocated:
case Attribute::ReadNone:
case Attribute::ReadOnly:
case Attribute::Returned:
case Attribute::ReturnsTwice:
case Attribute::SExt:
case Attribute::Speculatable:
case Attribute::StackAlignment:
case Attribute::StructRet:
case Attribute::SwiftError:
case Attribute::SwiftSelf:
case Attribute::WillReturn:
case Attribute::WriteOnly:
case Attribute::ZExt:
case Attribute::ImmArg:
case Attribute::ByRef:
case Attribute::EndAttrKinds:
case Attribute::EmptyKey:
case Attribute::TombstoneKey:
continue;
// Those attributes should be safe to propagate to the extracted function.
case Attribute::AlwaysInline:
case Attribute::Cold:
case Attribute::Hot:
case Attribute::NoRecurse:
case Attribute::InlineHint:
case Attribute::MinSize:
case Attribute::NoCallback:
case Attribute::NoDuplicate:
case Attribute::NoFree:
case Attribute::NoImplicitFloat:
case Attribute::NoInline:
case Attribute::NonLazyBind:
case Attribute::NoRedZone:
case Attribute::NoUnwind:
case Attribute::NullPointerIsValid:
case Attribute::OptForFuzzing:
case Attribute::OptimizeNone:
case Attribute::OptimizeForSize:
case Attribute::SafeStack:
case Attribute::ShadowCallStack:
case Attribute::SanitizeAddress:
case Attribute::SanitizeMemory:
case Attribute::SanitizeThread:
case Attribute::SanitizeHWAddress:
case Attribute::SanitizeMemTag:
case Attribute::SpeculativeLoadHardening:
case Attribute::StackProtect:
case Attribute::StackProtectReq:
case Attribute::StackProtectStrong:
case Attribute::StrictFP:
case Attribute::UWTable:
case Attribute::NoCfCheck:
case Attribute::MustProgress:
case Attribute::NoProfile:
break;
}
newFunction->addFnAttr(Attr);
}
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);
Instruction *TI = newFunction->begin()->getTerminator();
GetElementPtrInst *GEP = GetElementPtrInst::Create(
StructTy, &*AI, Idx, "gep_" + inputs[i]->getName(), TI);
RewriteVal = new LoadInst(StructTy->getElementType(i), 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 (auto &U : Users)
// The BasicBlock which contains the branch is not in the region
// modify the branch target to a new block
if (Instruction *I = dyn_cast<Instruction>(U))
if (I->isTerminator() && I->getFunction() == oldFunction &&
!Blocks.count(I->getParent()))
I->replaceUsesOfWith(header, newHeader);
return newFunction;
}
/// Erase lifetime.start markers which reference inputs to the extraction
/// region, and insert the referenced memory into \p LifetimesStart.
///
/// The extraction region is defined by a set of blocks (\p Blocks), and a set
/// of allocas which will be moved from the caller function into the extracted
/// function (\p SunkAllocas).
static void eraseLifetimeMarkersOnInputs(const SetVector<BasicBlock *> &Blocks,
const SetVector<Value *> &SunkAllocas,
SetVector<Value *> &LifetimesStart) {
for (BasicBlock *BB : Blocks) {
for (auto It = BB->begin(), End = BB->end(); It != End;) {
auto *II = dyn_cast<IntrinsicInst>(&*It);
++It;
if (!II || !II->isLifetimeStartOrEnd())
continue;
// Get the memory operand of the lifetime marker. If the underlying
// object is a sunk alloca, or is otherwise defined in the extraction
// region, the lifetime marker must not be erased.
Value *Mem = II->getOperand(1)->stripInBoundsOffsets();
if (SunkAllocas.count(Mem) || definedInRegion(Blocks, Mem))
continue;
if (II->getIntrinsicID() == Intrinsic::lifetime_start)
LifetimesStart.insert(Mem);
II->eraseFromParent();
}
}
}
/// Insert lifetime start/end markers surrounding the call to the new function
/// for objects defined in the caller.
static void insertLifetimeMarkersSurroundingCall(
Module *M, ArrayRef<Value *> LifetimesStart, ArrayRef<Value *> LifetimesEnd,
CallInst *TheCall) {
LLVMContext &Ctx = M->getContext();
auto Int8PtrTy = Type::getInt8PtrTy(Ctx);
auto NegativeOne = ConstantInt::getSigned(Type::getInt64Ty(Ctx), -1);
Instruction *Term = TheCall->getParent()->getTerminator();
// The memory argument to a lifetime marker must be a i8*. Cache any bitcasts
// needed to satisfy this requirement so they may be reused.
DenseMap<Value *, Value *> Bitcasts;
// Emit lifetime markers for the pointers given in \p Objects. Insert the
// markers before the call if \p InsertBefore, and after the call otherwise.
auto insertMarkers = [&](Function *MarkerFunc, ArrayRef<Value *> Objects,
bool InsertBefore) {
for (Value *Mem : Objects) {
assert((!isa<Instruction>(Mem) || cast<Instruction>(Mem)->getFunction() ==
TheCall->getFunction()) &&
"Input memory not defined in original function");
Value *&MemAsI8Ptr = Bitcasts[Mem];
if (!MemAsI8Ptr) {
if (Mem->getType() == Int8PtrTy)
MemAsI8Ptr = Mem;
else
MemAsI8Ptr =
CastInst::CreatePointerCast(Mem, Int8PtrTy, "lt.cast", TheCall);
}
auto Marker = CallInst::Create(MarkerFunc, {NegativeOne, MemAsI8Ptr});
if (InsertBefore)
Marker->insertBefore(TheCall);
else
Marker->insertBefore(Term);
}
};
if (!LifetimesStart.empty()) {
auto StartFn = llvm::Intrinsic::getDeclaration(
M, llvm::Intrinsic::lifetime_start, Int8PtrTy);
insertMarkers(StartFn, LifetimesStart, /*InsertBefore=*/true);
}
if (!LifetimesEnd.empty()) {
auto EndFn = llvm::Intrinsic::getDeclaration(
M, llvm::Intrinsic::lifetime_end, Int8PtrTy);
insertMarkers(EndFn, LifetimesEnd, /*InsertBefore=*/false);
}
}
/// emitCallAndSwitchStatement - This method sets up the caller side by adding
/// the call instruction, splitting any PHI nodes in the header block as
/// necessary.
CallInst *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();
CallInst *call = nullptr;
// Add inputs as params, or to be filled into the struct
unsigned ArgNo = 0;
SmallVector<unsigned, 1> SwiftErrorArgs;
for (Value *input : inputs) {
if (AggregateArgs)
StructValues.push_back(input);
else {
params.push_back(input);
if (input->isSwiftError())
SwiftErrorArgs.push_back(ArgNo);
}
++ArgNo;
}
// 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);
new StoreInst(StructValues[i], GEP, codeReplacer);
}
}
// Emit the call to the function
call = CallInst::Create(newFunction, params,
NumExitBlocks > 1 ? "targetBlock" : "");
// Add debug location to the new call, if the original function has debug
// info. In that case, the terminator of the entry block of the extracted
// function contains the first debug location of the extracted function,
// set in extractCodeRegion.
if (codeReplacer->getParent()->getSubprogram()) {
if (auto DL = newFunction->getEntryBlock().getTerminator()->getDebugLoc())
call->setDebugLoc(DL);
}
codeReplacer->getInstList().push_back(call);
// Set swifterror parameter attributes.
for (unsigned SwiftErrArgNo : SwiftErrorArgs) {
call->addParamAttr(SwiftErrArgNo, Attribute::SwiftError);
newFunction->addParamAttr(SwiftErrArgNo, Attribute::SwiftError);
}
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(outputs[i]->getType(), Output,
outputs[i]->getName() + ".reload",
codeReplacer);
Reloads.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) {
Instruction *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::Create(Context, brVal, NewTarget);
// Update the switch instruction.
TheSwitch->addCase(ConstantInt::get(Type::getInt16Ty(Context),
SuccNum),
OldTarget);
}
// rewrite the original branch instruction with this new target
TI->setSuccessor(i, NewTarget);
}
}
// Store the arguments right after the definition of output value.
// This should be proceeded after creating exit stubs to be ensure that invoke
// result restore will be placed in the outlined function.
Function::arg_iterator OAI = OutputArgBegin;
for (unsigned i = 0, e = outputs.size(); i != e; ++i) {
auto *OutI = dyn_cast<Instruction>(outputs[i]);
if (!OutI)
continue;
// Find proper insertion point.
BasicBlock::iterator InsertPt;
// In case OutI is an invoke, we insert the store at the beginning in the
// 'normal destination' BB. Otherwise we insert the store right after OutI.
if (auto *InvokeI = dyn_cast<InvokeInst>(OutI))
InsertPt = InvokeI->getNormalDest()->getFirstInsertionPt();
else if (auto *Phi = dyn_cast<PHINode>(OutI))
InsertPt = Phi->getParent()->getFirstInsertionPt();
else
InsertPt = std::next(OutI->getIterator());
Instruction *InsertBefore = &*InsertPt;
assert((InsertBefore->getFunction() == newFunction ||
Blocks.count(InsertBefore->getParent())) &&
"InsertPt should be in new function");
assert(OAI != newFunction->arg_end() &&
"Number of output arguments should match "
"the amount of defined values");
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, &*OAI, Idx, "gep_" + outputs[i]->getName(),
InsertBefore);
new StoreInst(outputs[i], GEP, InsertBefore);
// Since there should be only one struct argument aggregating
// all the output values, we shouldn't increment OAI, which always
// points to the struct argument, in this case.
} else {
new StoreInst(outputs[i], &*OAI, InsertBefore);
++OAI;
}
}
// 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;
}
// Insert lifetime markers around the reloads of any output values. The
// allocas output values are stored in are only in-use in the codeRepl block.
insertLifetimeMarkersSurroundingCall(M, ReloadOutputs, ReloadOutputs, call);
return call;
}
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) {
using Distribution = BlockFrequencyInfoImplBase::Distribution;
using BlockNode = BlockFrequencyInfoImplBase::BlockNode;
// Update the branch weights for the exit block.
Instruction *TI = CodeReplacer->getTerminator();
SmallVector<unsigned, 8> BranchWeights(TI->getNumSuccessors(), 0);
// Block Frequency distribution with dummy node.
Distribution BranchDist;
SmallVector<BranchProbability, 4> EdgeProbabilities(
TI->getNumSuccessors(), BranchProbability::getUnknown());
// 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
EdgeProbabilities[i] = BranchProbability::getZero();
}
// Check for no total weight.
if (BranchDist.Total == 0) {
BPI->setEdgeProbability(CodeReplacer, EdgeProbabilities);
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);
EdgeProbabilities[Weight.TargetNode.Index] = BP;
}
BPI->setEdgeProbability(CodeReplacer, EdgeProbabilities);
TI->setMetadata(
LLVMContext::MD_prof,
MDBuilder(TI->getContext()).createBranchWeights(BranchWeights));
}
/// Erase debug info intrinsics which refer to values in \p F but aren't in
/// \p F.
static void eraseDebugIntrinsicsWithNonLocalRefs(Function &F) {
for (Instruction &I : instructions(F)) {
SmallVector<DbgVariableIntrinsic *, 4> DbgUsers;
findDbgUsers(DbgUsers, &I);
for (DbgVariableIntrinsic *DVI : DbgUsers)
if (DVI->getFunction() != &F)
DVI->eraseFromParent();
}
}
/// Fix up the debug info in the old and new functions by pointing line
/// locations and debug intrinsics to the new subprogram scope, and by deleting
/// intrinsics which point to values outside of the new function.
static void fixupDebugInfoPostExtraction(Function &OldFunc, Function &NewFunc,
CallInst &TheCall) {
DISubprogram *OldSP = OldFunc.getSubprogram();
LLVMContext &Ctx = OldFunc.getContext();
if (!OldSP) {
// Erase any debug info the new function contains.
stripDebugInfo(NewFunc);
// Make sure the old function doesn't contain any non-local metadata refs.
eraseDebugIntrinsicsWithNonLocalRefs(NewFunc);
return;
}
// Create a subprogram for the new function. Leave out a description of the
// function arguments, as the parameters don't correspond to anything at the
// source level.
assert(OldSP->getUnit() && "Missing compile unit for subprogram");
DIBuilder DIB(*OldFunc.getParent(), /*AllowUnresolved=*/false,
OldSP->getUnit());
auto SPType = DIB.createSubroutineType(DIB.getOrCreateTypeArray(None));
DISubprogram::DISPFlags SPFlags = DISubprogram::SPFlagDefinition |
DISubprogram::SPFlagOptimized |
DISubprogram::SPFlagLocalToUnit;
auto NewSP = DIB.createFunction(
OldSP->getUnit(), NewFunc.getName(), NewFunc.getName(), OldSP->getFile(),
/*LineNo=*/0, SPType, /*ScopeLine=*/0, DINode::FlagZero, SPFlags);
NewFunc.setSubprogram(NewSP);
// Debug intrinsics in the new function need to be updated in one of two
// ways:
// 1) They need to be deleted, because they describe a value in the old
// function.
// 2) They need to point to fresh metadata, e.g. because they currently
// point to a variable in the wrong scope.
SmallDenseMap<DINode *, DINode *> RemappedMetadata;
SmallVector<Instruction *, 4> DebugIntrinsicsToDelete;
for (Instruction &I : instructions(NewFunc)) {
auto *DII = dyn_cast<DbgInfoIntrinsic>(&I);
if (!DII)
continue;
// Point the intrinsic to a fresh label within the new function.
if (auto *DLI = dyn_cast<DbgLabelInst>(&I)) {
DILabel *OldLabel = DLI->getLabel();
DINode *&NewLabel = RemappedMetadata[OldLabel];
if (!NewLabel)
NewLabel = DILabel::get(Ctx, NewSP, OldLabel->getName(),
OldLabel->getFile(), OldLabel->getLine());
DLI->setArgOperand(0, MetadataAsValue::get(Ctx, NewLabel));
continue;
}
// If the location isn't a constant or an instruction, delete the
// intrinsic.
auto *DVI = cast<DbgVariableIntrinsic>(DII);
Value *Location = DVI->getVariableLocation();
if (!Location ||
(!isa<Constant>(Location) && !isa<Instruction>(Location))) {
DebugIntrinsicsToDelete.push_back(DVI);
continue;
}
// If the variable location is an instruction but isn't in the new
// function, delete the intrinsic.
Instruction *LocationInst = dyn_cast<Instruction>(Location);
if (LocationInst && LocationInst->getFunction() != &NewFunc) {
DebugIntrinsicsToDelete.push_back(DVI);
continue;
}
// Point the intrinsic to a fresh variable within the new function.
DILocalVariable *OldVar = DVI->getVariable();
DINode *&NewVar = RemappedMetadata[OldVar];
if (!NewVar)
NewVar = DIB.createAutoVariable(
NewSP, OldVar->getName(), OldVar->getFile(), OldVar->getLine(),
OldVar->getType(), /*AlwaysPreserve=*/false, DINode::FlagZero,
OldVar->getAlignInBits());
DVI->setArgOperand(1, MetadataAsValue::get(Ctx, NewVar));
}
for (auto *DII : DebugIntrinsicsToDelete)
DII->eraseFromParent();
DIB.finalizeSubprogram(NewSP);
// Fix up the scope information attached to the line locations in the new
// function.
for (Instruction &I : instructions(NewFunc)) {
if (const DebugLoc &DL = I.getDebugLoc())
I.setDebugLoc(DILocation::get(Ctx, DL.getLine(), DL.getCol(), NewSP));
// Loop info metadata may contain line locations. Fix them up.
auto updateLoopInfoLoc = [&Ctx,
NewSP](const DILocation &Loc) -> DILocation * {
return DILocation::get(Ctx, Loc.getLine(), Loc.getColumn(), NewSP,
nullptr);
};
updateLoopMetadataDebugLocations(I, updateLoopInfoLoc);
}
if (!TheCall.getDebugLoc())
TheCall.setDebugLoc(DILocation::get(Ctx, 0, 0, OldSP));
eraseDebugIntrinsicsWithNonLocalRefs(NewFunc);
}
Function *
CodeExtractor::extractCodeRegion(const CodeExtractorAnalysisCache &CEAC) {
if (!isEligible())
return nullptr;
// Assumption: this is a single-entry code region, and the header is the first
// block in the region.
BasicBlock *header = *Blocks.begin();
Function *oldFunction = header->getParent();
// 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);
}
}
// Remove @llvm.assume calls that will be moved to the new function from the
// old function's assumption cache.
for (BasicBlock *Block : Blocks) {
for (auto It = Block->begin(), End = Block->end(); It != End;) {
Instruction *I = &*It;
++It;
if (match(I, m_Intrinsic<Intrinsic::assume>())) {
if (AC)
AC->unregisterAssumption(cast<CallInst>(I));
I->eraseFromParent();
}
}
}
// If we have any return instructions in the region, split those blocks so
// that the return is not in the region.
splitReturnBlocks();
// 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();
// If we have to split PHI nodes of the entry or exit blocks, do so now.
severSplitPHINodesOfEntry(header);
severSplitPHINodesOfExits(ExitBlocks);
// 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");
auto *BranchI = BranchInst::Create(header);
// If the original function has debug info, we have to add a debug location
// to the new branch instruction from the artificial entry block.
// We use the debug location of the first instruction in the extracted
// blocks, as there is no other equivalent line in the source code.
if (oldFunction->getSubprogram()) {
any_of(Blocks, [&BranchI](const BasicBlock *BB) {
return any_of(*BB, [&BranchI](const Instruction &I) {
if (!I.getDebugLoc())
return false;
BranchI->setDebugLoc(I.getDebugLoc());
return true;
});
});
}
newFuncRoot->getInstList().push_back(BranchI);
ValueSet inputs, outputs, SinkingCands, HoistingCands;
BasicBlock *CommonExit = nullptr;
findAllocas(CEAC, 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.
// Group the allocas at the start of the block, so that any bitcast uses of
// the allocas are well-defined.
AllocaInst *FirstSunkAlloca = nullptr;
for (auto *II : SinkingCands) {
if (auto *AI = dyn_cast<AllocaInst>(II)) {
AI->moveBefore(*newFuncRoot, newFuncRoot->getFirstInsertionPt());
if (!FirstSunkAlloca)
FirstSunkAlloca = AI;
}
}
assert((SinkingCands.empty() || FirstSunkAlloca) &&
"Did not expect a sink candidate without any allocas");
for (auto *II : SinkingCands) {
if (!isa<AllocaInst>(II)) {
cast<Instruction>(II)->moveAfter(FirstSunkAlloca);
}
}
if (!HoistingCands.empty()) {
auto *HoistToBlock = findOrCreateBlockForHoisting(CommonExit);
Instruction *TI = HoistToBlock->getTerminator();
for (auto *II : HoistingCands)
cast<Instruction>(II)->moveBefore(TI);
}
// Collect objects which are inputs to the extraction region and also
// referenced by lifetime start markers within it. The effects of these
// markers must be replicated in the calling function to prevent the stack
// coloring pass from merging slots which store input objects.
ValueSet LifetimesStart;
eraseLifetimeMarkersOnInputs(Blocks, SinkingCands, LifetimesStart);
// 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) {
auto Count = BFI->getProfileCountFromFreq(EntryFreq.getFrequency());
if (Count.hasValue())
newFunction->setEntryCount(
ProfileCount(Count.getValue(), Function::PCT_Real)); // FIXME
BFI->setBlockFreq(codeReplacer, EntryFreq.getFrequency());
}
CallInst *TheCall =
emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs);
moveCodeToFunction(newFunction);
// Replicate the effects of any lifetime start/end markers which referenced
// input objects in the extraction region by placing markers around the call.
insertLifetimeMarkersSurroundingCall(
oldFunction->getParent(), LifetimesStart.getArrayRef(), {}, TheCall);
// Propagate personality info to the new function if there is one.
if (oldFunction->hasPersonalityFn())
newFunction->setPersonalityFn(oldFunction->getPersonalityFn());
// 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 and exit blocks, 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);
}
for (BasicBlock *ExitBB : ExitBlocks)
for (PHINode &PN : ExitBB->phis()) {
Value *IncomingCodeReplacerVal = nullptr;
for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
// Ignore incoming values from outside of the extracted region.
if (!Blocks.count(PN.getIncomingBlock(i)))
continue;
// Ensure that there is only one incoming value from codeReplacer.
if (!IncomingCodeReplacerVal) {
PN.setIncomingBlock(i, codeReplacer);
IncomingCodeReplacerVal = PN.getIncomingValue(i);
} else
assert(IncomingCodeReplacerVal == PN.getIncomingValue(i) &&
"PHI has two incompatbile incoming values from codeRepl");
}
}
fixupDebugInfoPostExtraction(*oldFunction, *newFunction, *TheCall);
// Mark the new function `noreturn` if applicable. Terminators which resume
// exception propagation are treated as returning instructions. This is to
// avoid inserting traps after calls to outlined functions which unwind.
bool doesNotReturn = none_of(*newFunction, [](const BasicBlock &BB) {
const Instruction *Term = BB.getTerminator();
return isa<ReturnInst>(Term) || isa<ResumeInst>(Term);
});
if (doesNotReturn)
newFunction->setDoesNotReturn();
LLVM_DEBUG(if (verifyFunction(*newFunction, &errs())) {
newFunction->dump();
report_fatal_error("verification of newFunction failed!");
});
LLVM_DEBUG(if (verifyFunction(*oldFunction))
report_fatal_error("verification of oldFunction failed!"));
LLVM_DEBUG(if (AC && verifyAssumptionCache(*oldFunction, *newFunction, AC))
report_fatal_error("Stale Asumption cache for old Function!"));
return newFunction;
}
bool CodeExtractor::verifyAssumptionCache(const Function &OldFunc,
const Function &NewFunc,
AssumptionCache *AC) {
for (auto AssumeVH : AC->assumptions()) {
auto *I = dyn_cast_or_null<CallInst>(AssumeVH);
if (!I)
continue;
// There shouldn't be any llvm.assume intrinsics in the new function.
if (I->getFunction() != &OldFunc)
return true;
// There shouldn't be any stale affected values in the assumption cache
// that were previously in the old function, but that have now been moved
// to the new function.
for (auto AffectedValVH : AC->assumptionsFor(I->getOperand(0))) {
auto *AffectedCI = dyn_cast_or_null<CallInst>(AffectedValVH);
if (!AffectedCI)
continue;
if (AffectedCI->getFunction() != &OldFunc)
return true;
auto *AssumedInst = cast<Instruction>(AffectedCI->getOperand(0));
if (AssumedInst->getFunction() != &OldFunc)
return true;
}
}
return false;
}