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llvm-mirror/lib/Transforms/Utils/CodeExtractor.cpp
Nikita Popov d58a8fbeab [IR] Add elementtype attribute 
This implements the elementtype attribute specified in D105407. It
just adds the attribute and the specified verifier rules, but
doesn't yet make use of it anywhere.

Differential Revision: https://reviews.llvm.org/D106008
2021-07-15 18:04:26 +02:00

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//===- 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 (isa<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 (BasicBlock *Pred :
llvm::make_early_inc_range(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;
}
// 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::ElementType:
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::SwiftAsync:
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::NoSanitizeCoverage:
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::VScaleRange:
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 (Value *V : StructValues)
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;
}
auto IsInvalidLocation = [&NewFunc](Value *Location) {
// Location is invalid if it isn't a constant or an instruction, or is an
// instruction but isn't in the new function.
if (!Location ||
(!isa<Constant>(Location) && !isa<Instruction>(Location)))
return true;
Instruction *LocationInst = dyn_cast<Instruction>(Location);
return LocationInst && LocationInst->getFunction() != &NewFunc;
};
auto *DVI = cast<DbgVariableIntrinsic>(DII);
// If any of the used locations are invalid, delete the intrinsic.
if (any_of(DVI->location_ops(), IsInvalidLocation)) {
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->setVariable(cast<DILocalVariable>(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](Metadata *MD) -> Metadata * {
if (auto *Loc = dyn_cast_or_null<DILocation>(MD))
return DILocation::get(Ctx, Loc->getLine(), Loc->getColumn(), NewSP,
nullptr);
return MD;
};
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 (auto *AI = dyn_cast<AssumeInst>(I)) {
if (AC)
AC->unregisterAssumption(AI);
AI->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 (BasicBlock *Succ : successors(Block)) {
if (!Blocks.count(Succ)) {
// Update the branch weight for this successor.
if (BFI) {
BlockFrequency &BF = ExitWeights[Succ];
BF += BFI->getBlockFreq(Block) * BPI->getEdgeProbability(Block, Succ);
}
ExitBlocks.insert(Succ);
}
}
}
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;
}
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