maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/llvm/lib/CodeGen/WinEHPrepare.cpp

1083 lines
41 KiB
C++
Raw Blame History

//===-- WinEHPrepare - Prepare exception handling for code generation ---===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass lowers LLVM IR exception handling into something closer to what the
// backend wants for functions using a personality function from a runtime
// provided by MSVC. Functions with other personality functions are left alone
// and may be prepared by other passes. In particular, all supported MSVC
// personality functions require cleanup code to be outlined, and the C++
// personality requires catch handler code to be outlined.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Passes.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/EHPersonalities.h"
#include "llvm/CodeGen/WinEHFuncInfo.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
using namespace llvm;
#define DEBUG_TYPE "winehprepare"
static cl::opt<bool> DisableDemotion(
"disable-demotion", cl::Hidden,
cl::desc(
"Clone multicolor basic blocks but do not demote cross funclet values"),
cl::init(false));
static cl::opt<bool> DisableCleanups(
"disable-cleanups", cl::Hidden,
cl::desc("Do not remove implausible terminators or other similar cleanups"),
cl::init(false));
namespace {
class WinEHPrepare : public FunctionPass {
public:
static char ID; // Pass identification, replacement for typeid.
WinEHPrepare(const TargetMachine *TM = nullptr) : FunctionPass(ID) {}
bool runOnFunction(Function &Fn) override;
bool doFinalization(Module &M) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
const char *getPassName() const override {
return "Windows exception handling preparation";
}
private:
void insertPHIStores(PHINode *OriginalPHI, AllocaInst *SpillSlot);
void
insertPHIStore(BasicBlock *PredBlock, Value *PredVal, AllocaInst *SpillSlot,
SmallVectorImpl<std::pair<BasicBlock *, Value *>> &Worklist);
AllocaInst *insertPHILoads(PHINode *PN, Function &F);
void replaceUseWithLoad(Value *V, Use &U, AllocaInst *&SpillSlot,
DenseMap<BasicBlock *, Value *> &Loads, Function &F);
bool prepareExplicitEH(Function &F);
void replaceTerminatePadWithCleanup(Function &F);
void colorFunclets(Function &F);
void demotePHIsOnFunclets(Function &F);
void cloneCommonBlocks(Function &F);
void removeImplausibleTerminators(Function &F);
void cleanupPreparedFunclets(Function &F);
void verifyPreparedFunclets(Function &F);
// All fields are reset by runOnFunction.
EHPersonality Personality = EHPersonality::Unknown;
DenseMap<BasicBlock *, ColorVector> BlockColors;
MapVector<BasicBlock *, std::vector<BasicBlock *>> FuncletBlocks;
};
} // end anonymous namespace
char WinEHPrepare::ID = 0;
INITIALIZE_TM_PASS(WinEHPrepare, "winehprepare", "Prepare Windows exceptions",
false, false)
FunctionPass *llvm::createWinEHPass(const TargetMachine *TM) {
return new WinEHPrepare(TM);
}
bool WinEHPrepare::runOnFunction(Function &Fn) {
if (!Fn.hasPersonalityFn())
return false;
// Classify the personality to see what kind of preparation we need.
Personality = classifyEHPersonality(Fn.getPersonalityFn());
// Do nothing if this is not a funclet-based personality.
if (!isFuncletEHPersonality(Personality))
return false;
return prepareExplicitEH(Fn);
}
bool WinEHPrepare::doFinalization(Module &M) { return false; }
void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {}
static int addUnwindMapEntry(WinEHFuncInfo &FuncInfo, int ToState,
const BasicBlock *BB) {
CxxUnwindMapEntry UME;
UME.ToState = ToState;
UME.Cleanup = BB;
FuncInfo.CxxUnwindMap.push_back(UME);
return FuncInfo.getLastStateNumber();
}
static void addTryBlockMapEntry(WinEHFuncInfo &FuncInfo, int TryLow,
int TryHigh, int CatchHigh,
ArrayRef<const CatchPadInst *> Handlers) {
WinEHTryBlockMapEntry TBME;
TBME.TryLow = TryLow;
TBME.TryHigh = TryHigh;
TBME.CatchHigh = CatchHigh;
assert(TBME.TryLow <= TBME.TryHigh);
for (const CatchPadInst *CPI : Handlers) {
WinEHHandlerType HT;
Constant *TypeInfo = cast<Constant>(CPI->getArgOperand(0));
if (TypeInfo->isNullValue())
HT.TypeDescriptor = nullptr;
else
HT.TypeDescriptor = cast<GlobalVariable>(TypeInfo->stripPointerCasts());
HT.Adjectives = cast<ConstantInt>(CPI->getArgOperand(1))->getZExtValue();
HT.Handler = CPI->getParent();
if (isa<ConstantPointerNull>(CPI->getArgOperand(2)))
HT.CatchObj.Alloca = nullptr;
else
HT.CatchObj.Alloca = cast<AllocaInst>(CPI->getArgOperand(2));
TBME.HandlerArray.push_back(HT);
}
FuncInfo.TryBlockMap.push_back(TBME);
}
static BasicBlock *getCleanupRetUnwindDest(const CleanupPadInst *CleanupPad) {
for (const User *U : CleanupPad->users())
if (const auto *CRI = dyn_cast<CleanupReturnInst>(U))
return CRI->getUnwindDest();
return nullptr;
}
static void calculateStateNumbersForInvokes(const Function *Fn,
WinEHFuncInfo &FuncInfo) {
auto *F = const_cast<Function *>(Fn);
DenseMap<BasicBlock *, ColorVector> BlockColors = colorEHFunclets(*F);
for (BasicBlock &BB : *F) {
auto *II = dyn_cast<InvokeInst>(BB.getTerminator());
if (!II)
continue;
auto &BBColors = BlockColors[&BB];
assert(BBColors.size() == 1 &&
"multi-color BB not removed by preparation");
BasicBlock *FuncletEntryBB = BBColors.front();
BasicBlock *FuncletUnwindDest;
auto *FuncletPad =
dyn_cast<FuncletPadInst>(FuncletEntryBB->getFirstNonPHI());
assert(FuncletPad || FuncletEntryBB == &Fn->getEntryBlock());
if (!FuncletPad)
FuncletUnwindDest = nullptr;
else if (auto *CatchPad = dyn_cast<CatchPadInst>(FuncletPad))
FuncletUnwindDest = CatchPad->getCatchSwitch()->getUnwindDest();
else if (auto *CleanupPad = dyn_cast<CleanupPadInst>(FuncletPad))
FuncletUnwindDest = getCleanupRetUnwindDest(CleanupPad);
else
llvm_unreachable("unexpected funclet pad!");
BasicBlock *InvokeUnwindDest = II->getUnwindDest();
int BaseState = -1;
if (FuncletUnwindDest == InvokeUnwindDest) {
auto BaseStateI = FuncInfo.FuncletBaseStateMap.find(FuncletPad);
if (BaseStateI != FuncInfo.FuncletBaseStateMap.end())
BaseState = BaseStateI->second;
}
if (BaseState != -1) {
FuncInfo.InvokeStateMap[II] = BaseState;
} else {
Instruction *PadInst = InvokeUnwindDest->getFirstNonPHI();
assert(FuncInfo.EHPadStateMap.count(PadInst) && "EH Pad has no state!");
FuncInfo.InvokeStateMap[II] = FuncInfo.EHPadStateMap[PadInst];
}
}
}
// Given BB which ends in an unwind edge, return the EHPad that this BB belongs
// to. If the unwind edge came from an invoke, return null.
static const BasicBlock *getEHPadFromPredecessor(const BasicBlock *BB,
Value *ParentPad) {
const TerminatorInst *TI = BB->getTerminator();
if (isa<InvokeInst>(TI))
return nullptr;
if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(TI)) {
if (CatchSwitch->getParentPad() != ParentPad)
return nullptr;
return BB;
}
assert(!TI->isEHPad() && "unexpected EHPad!");
auto *CleanupPad = cast<CleanupReturnInst>(TI)->getCleanupPad();
if (CleanupPad->getParentPad() != ParentPad)
return nullptr;
return CleanupPad->getParent();
}
static void calculateCXXStateNumbers(WinEHFuncInfo &FuncInfo,
const Instruction *FirstNonPHI,
int ParentState) {
const BasicBlock *BB = FirstNonPHI->getParent();
assert(BB->isEHPad() && "not a funclet!");
if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(FirstNonPHI)) {
assert(FuncInfo.EHPadStateMap.count(CatchSwitch) == 0 &&
"shouldn't revist catch funclets!");
SmallVector<const CatchPadInst *, 2> Handlers;
for (const BasicBlock *CatchPadBB : CatchSwitch->handlers()) {
auto *CatchPad = cast<CatchPadInst>(CatchPadBB->getFirstNonPHI());
Handlers.push_back(CatchPad);
}
int TryLow = addUnwindMapEntry(FuncInfo, ParentState, nullptr);
FuncInfo.EHPadStateMap[CatchSwitch] = TryLow;
for (const BasicBlock *PredBlock : predecessors(BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock,
CatchSwitch->getParentPad())))
calculateCXXStateNumbers(FuncInfo, PredBlock->getFirstNonPHI(),
TryLow);
int CatchLow = addUnwindMapEntry(FuncInfo, ParentState, nullptr);
// catchpads are separate funclets in C++ EH due to the way rethrow works.
int TryHigh = CatchLow - 1;
for (const auto *CatchPad : Handlers) {
FuncInfo.FuncletBaseStateMap[CatchPad] = CatchLow;
for (const User *U : CatchPad->users()) {
const auto *UserI = cast<Instruction>(U);
if (UserI->isEHPad())
calculateCXXStateNumbers(FuncInfo, UserI, CatchLow);
}
}
int CatchHigh = FuncInfo.getLastStateNumber();
addTryBlockMapEntry(FuncInfo, TryLow, TryHigh, CatchHigh, Handlers);
DEBUG(dbgs() << "TryLow[" << BB->getName() << "]: " << TryLow << '\n');
DEBUG(dbgs() << "TryHigh[" << BB->getName() << "]: " << TryHigh << '\n');
DEBUG(dbgs() << "CatchHigh[" << BB->getName() << "]: " << CatchHigh
<< '\n');
} else {
auto *CleanupPad = cast<CleanupPadInst>(FirstNonPHI);
// It's possible for a cleanup to be visited twice: it might have multiple
// cleanupret instructions.
if (FuncInfo.EHPadStateMap.count(CleanupPad))
return;
int CleanupState = addUnwindMapEntry(FuncInfo, ParentState, BB);
FuncInfo.EHPadStateMap[CleanupPad] = CleanupState;
DEBUG(dbgs() << "Assigning state #" << CleanupState << " to BB "
<< BB->getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(BB)) {
if ((PredBlock = getEHPadFromPredecessor(PredBlock,
CleanupPad->getParentPad()))) {
calculateCXXStateNumbers(FuncInfo, PredBlock->getFirstNonPHI(),
CleanupState);
}
}
for (const User *U : CleanupPad->users()) {
const auto *UserI = cast<Instruction>(U);
if (UserI->isEHPad())
report_fatal_error("Cleanup funclets for the MSVC++ personality cannot "
"contain exceptional actions");
}
}
}
static int addSEHExcept(WinEHFuncInfo &FuncInfo, int ParentState,
const Function *Filter, const BasicBlock *Handler) {
SEHUnwindMapEntry Entry;
Entry.ToState = ParentState;
Entry.IsFinally = false;
Entry.Filter = Filter;
Entry.Handler = Handler;
FuncInfo.SEHUnwindMap.push_back(Entry);
return FuncInfo.SEHUnwindMap.size() - 1;
}
static int addSEHFinally(WinEHFuncInfo &FuncInfo, int ParentState,
const BasicBlock *Handler) {
SEHUnwindMapEntry Entry;
Entry.ToState = ParentState;
Entry.IsFinally = true;
Entry.Filter = nullptr;
Entry.Handler = Handler;
FuncInfo.SEHUnwindMap.push_back(Entry);
return FuncInfo.SEHUnwindMap.size() - 1;
}
static void calculateSEHStateNumbers(WinEHFuncInfo &FuncInfo,
const Instruction *FirstNonPHI,
int ParentState) {
const BasicBlock *BB = FirstNonPHI->getParent();
assert(BB->isEHPad() && "no a funclet!");
if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(FirstNonPHI)) {
assert(FuncInfo.EHPadStateMap.count(CatchSwitch) == 0 &&
"shouldn't revist catch funclets!");
// Extract the filter function and the __except basic block and create a
// state for them.
assert(CatchSwitch->getNumHandlers() == 1 &&
"SEH doesn't have multiple handlers per __try");
const auto *CatchPad =
cast<CatchPadInst>((*CatchSwitch->handler_begin())->getFirstNonPHI());
const BasicBlock *CatchPadBB = CatchPad->getParent();
const Constant *FilterOrNull =
cast<Constant>(CatchPad->getArgOperand(0)->stripPointerCasts());
const Function *Filter = dyn_cast<Function>(FilterOrNull);
assert((Filter || FilterOrNull->isNullValue()) &&
"unexpected filter value");
int TryState = addSEHExcept(FuncInfo, ParentState, Filter, CatchPadBB);
// Everything in the __try block uses TryState as its parent state.
FuncInfo.EHPadStateMap[CatchSwitch] = TryState;
DEBUG(dbgs() << "Assigning state #" << TryState << " to BB "
<< CatchPadBB->getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock,
CatchSwitch->getParentPad())))
calculateSEHStateNumbers(FuncInfo, PredBlock->getFirstNonPHI(),
TryState);
// Everything in the __except block unwinds to ParentState, just like code
// outside the __try.
for (const User *U : CatchPad->users()) {
const auto *UserI = cast<Instruction>(U);
if (UserI->isEHPad()) {
calculateSEHStateNumbers(FuncInfo, UserI, ParentState);
}
}
} else {
auto *CleanupPad = cast<CleanupPadInst>(FirstNonPHI);
// It's possible for a cleanup to be visited twice: it might have multiple
// cleanupret instructions.
if (FuncInfo.EHPadStateMap.count(CleanupPad))
return;
int CleanupState = addSEHFinally(FuncInfo, ParentState, BB);
FuncInfo.EHPadStateMap[CleanupPad] = CleanupState;
DEBUG(dbgs() << "Assigning state #" << CleanupState << " to BB "
<< BB->getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(BB))
if ((PredBlock =
getEHPadFromPredecessor(PredBlock, CleanupPad->getParentPad())))
calculateSEHStateNumbers(FuncInfo, PredBlock->getFirstNonPHI(),
CleanupState);
for (const User *U : CleanupPad->users()) {
const auto *UserI = cast<Instruction>(U);
if (UserI->isEHPad())
report_fatal_error("Cleanup funclets for the SEH personality cannot "
"contain exceptional actions");
}
}
}
static bool isTopLevelPadForMSVC(const Instruction *EHPad) {
if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(EHPad))
return isa<ConstantTokenNone>(CatchSwitch->getParentPad()) &&
CatchSwitch->unwindsToCaller();
if (auto *CleanupPad = dyn_cast<CleanupPadInst>(EHPad))
return isa<ConstantTokenNone>(CleanupPad->getParentPad()) &&
getCleanupRetUnwindDest(CleanupPad) == nullptr;
if (isa<CatchPadInst>(EHPad))
return false;
llvm_unreachable("unexpected EHPad!");
}
void llvm::calculateSEHStateNumbers(const Function *Fn,
WinEHFuncInfo &FuncInfo) {
// Don't compute state numbers twice.
if (!FuncInfo.SEHUnwindMap.empty())
return;
for (const BasicBlock &BB : *Fn) {
if (!BB.isEHPad())
continue;
const Instruction *FirstNonPHI = BB.getFirstNonPHI();
if (!isTopLevelPadForMSVC(FirstNonPHI))
continue;
::calculateSEHStateNumbers(FuncInfo, FirstNonPHI, -1);
}
calculateStateNumbersForInvokes(Fn, FuncInfo);
}
void llvm::calculateWinCXXEHStateNumbers(const Function *Fn,
WinEHFuncInfo &FuncInfo) {
// Return if it's already been done.
if (!FuncInfo.EHPadStateMap.empty())
return;
for (const BasicBlock &BB : *Fn) {
if (!BB.isEHPad())
continue;
const Instruction *FirstNonPHI = BB.getFirstNonPHI();
if (!isTopLevelPadForMSVC(FirstNonPHI))
continue;
calculateCXXStateNumbers(FuncInfo, FirstNonPHI, -1);
}
calculateStateNumbersForInvokes(Fn, FuncInfo);
}
static int addClrEHHandler(WinEHFuncInfo &FuncInfo, int ParentState,
ClrHandlerType HandlerType, uint32_t TypeToken,
const BasicBlock *Handler) {
ClrEHUnwindMapEntry Entry;
Entry.Parent = ParentState;
Entry.Handler = Handler;
Entry.HandlerType = HandlerType;
Entry.TypeToken = TypeToken;
FuncInfo.ClrEHUnwindMap.push_back(Entry);
return FuncInfo.ClrEHUnwindMap.size() - 1;
}
void llvm::calculateClrEHStateNumbers(const Function *Fn,
WinEHFuncInfo &FuncInfo) {
// Return if it's already been done.
if (!FuncInfo.EHPadStateMap.empty())
return;
SmallVector<std::pair<const Instruction *, int>, 8> Worklist;
// Each pad needs to be able to refer to its parent, so scan the function
// looking for top-level handlers and seed the worklist with them.
for (const BasicBlock &BB : *Fn) {
if (!BB.isEHPad())
continue;
if (BB.isLandingPad())
report_fatal_error("CoreCLR EH cannot use landingpads");
const Instruction *FirstNonPHI = BB.getFirstNonPHI();
if (!isTopLevelPadForMSVC(FirstNonPHI))
continue;
// queue this with sentinel parent state -1 to mean unwind to caller.
Worklist.emplace_back(FirstNonPHI, -1);
}
while (!Worklist.empty()) {
const Instruction *Pad;
int ParentState;
std::tie(Pad, ParentState) = Worklist.pop_back_val();
Value *ParentPad;
int PredState;
if (const CleanupPadInst *Cleanup = dyn_cast<CleanupPadInst>(Pad)) {
// A cleanup can have multiple exits; don't re-process after the first.
if (FuncInfo.EHPadStateMap.count(Cleanup))
continue;
// CoreCLR personality uses arity to distinguish faults from finallies.
const BasicBlock *PadBlock = Cleanup->getParent();
ClrHandlerType HandlerType =
(Cleanup->getNumOperands() ? ClrHandlerType::Fault
: ClrHandlerType::Finally);
int NewState =
addClrEHHandler(FuncInfo, ParentState, HandlerType, 0, PadBlock);
FuncInfo.EHPadStateMap[Cleanup] = NewState;
// Propagate the new state to all preds of the cleanup
ParentPad = Cleanup->getParentPad();
PredState = NewState;
} else if (const auto *CatchSwitch = dyn_cast<CatchSwitchInst>(Pad)) {
SmallVector<const CatchPadInst *, 1> Handlers;
for (const BasicBlock *CatchPadBB : CatchSwitch->handlers()) {
const auto *Catch = cast<CatchPadInst>(CatchPadBB->getFirstNonPHI());
Handlers.push_back(Catch);
}
FuncInfo.EHPadStateMap[CatchSwitch] = ParentState;
int NewState = ParentState;
for (auto HandlerI = Handlers.rbegin(), HandlerE = Handlers.rend();
HandlerI != HandlerE; ++HandlerI) {
const CatchPadInst *Catch = *HandlerI;
const BasicBlock *PadBlock = Catch->getParent();
uint32_t TypeToken = static_cast<uint32_t>(
cast<ConstantInt>(Catch->getArgOperand(0))->getZExtValue());
NewState = addClrEHHandler(FuncInfo, NewState, ClrHandlerType::Catch,
TypeToken, PadBlock);
FuncInfo.EHPadStateMap[Catch] = NewState;
}
for (const auto *CatchPad : Handlers) {
for (const User *U : CatchPad->users()) {
const auto *UserI = cast<Instruction>(U);
if (UserI->isEHPad())
Worklist.emplace_back(UserI, ParentState);
}
}
PredState = NewState;
ParentPad = CatchSwitch->getParentPad();
} else {
llvm_unreachable("Unexpected EH pad");
}
// Queue all predecessors with the given state
for (const BasicBlock *Pred : predecessors(Pad->getParent())) {
if ((Pred = getEHPadFromPredecessor(Pred, ParentPad)))
Worklist.emplace_back(Pred->getFirstNonPHI(), PredState);
}
}
calculateStateNumbersForInvokes(Fn, FuncInfo);
}
void WinEHPrepare::replaceTerminatePadWithCleanup(Function &F) {
if (Personality != EHPersonality::MSVC_CXX)
return;
for (BasicBlock &BB : F) {
Instruction *First = BB.getFirstNonPHI();
auto *TPI = dyn_cast<TerminatePadInst>(First);
if (!TPI)
continue;
if (TPI->getNumArgOperands() != 1)
report_fatal_error(
"Expected a unary terminatepad for MSVC C++ personalities!");
auto *TerminateFn = dyn_cast<Function>(TPI->getArgOperand(0));
if (!TerminateFn)
report_fatal_error("Function operand expected in terminatepad for MSVC "
"C++ personalities!");
// Insert the cleanuppad instruction.
auto *CPI =
CleanupPadInst::Create(TPI->getParentPad(), {},
Twine("terminatepad.for.", BB.getName()), &BB);
// Insert the call to the terminate instruction.
auto *CallTerminate = CallInst::Create(TerminateFn, {}, &BB);
CallTerminate->setDoesNotThrow();
CallTerminate->setDoesNotReturn();
CallTerminate->setCallingConv(TerminateFn->getCallingConv());
// Insert a new terminator for the cleanuppad using the same successor as
// the terminatepad.
CleanupReturnInst::Create(CPI, TPI->getUnwindDest(), &BB);
// Let's remove the terminatepad now that we've inserted the new
// instructions.
TPI->eraseFromParent();
}
}
void WinEHPrepare::colorFunclets(Function &F) {
BlockColors = colorEHFunclets(F);
// Invert the map from BB to colors to color to BBs.
for (BasicBlock &BB : F) {
ColorVector &Colors = BlockColors[&BB];
for (BasicBlock *Color : Colors)
FuncletBlocks[Color].push_back(&BB);
}
}
void llvm::calculateCatchReturnSuccessorColors(const Function *Fn,
WinEHFuncInfo &FuncInfo) {
for (const BasicBlock &BB : *Fn) {
const auto *CatchRet = dyn_cast<CatchReturnInst>(BB.getTerminator());
if (!CatchRet)
continue;
// A 'catchret' returns to the outer scope's color.
Value *ParentPad = CatchRet->getParentPad();
const BasicBlock *Color;
if (isa<ConstantTokenNone>(ParentPad))
Color = &Fn->getEntryBlock();
else
Color = cast<Instruction>(ParentPad)->getParent();
// Record the catchret successor's funclet membership.
FuncInfo.CatchRetSuccessorColorMap[CatchRet] = Color;
}
}
void WinEHPrepare::demotePHIsOnFunclets(Function &F) {
// Strip PHI nodes off of EH pads.
SmallVector<PHINode *, 16> PHINodes;
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) {
BasicBlock *BB = &*FI++;
if (!BB->isEHPad())
continue;
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
Instruction *I = &*BI++;
auto *PN = dyn_cast<PHINode>(I);
// Stop at the first non-PHI.
if (!PN)
break;
AllocaInst *SpillSlot = insertPHILoads(PN, F);
if (SpillSlot)
insertPHIStores(PN, SpillSlot);
PHINodes.push_back(PN);
}
}
for (auto *PN : PHINodes) {
// There may be lingering uses on other EH PHIs being removed
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
PN->eraseFromParent();
}
}
void WinEHPrepare::cloneCommonBlocks(Function &F) {
// We need to clone all blocks which belong to multiple funclets. Values are
// remapped throughout the funclet to propogate both the new instructions
// *and* the new basic blocks themselves.
for (auto &Funclets : FuncletBlocks) {
BasicBlock *FuncletPadBB = Funclets.first;
std::vector<BasicBlock *> &BlocksInFunclet = Funclets.second;
std::vector<std::pair<BasicBlock *, BasicBlock *>> Orig2Clone;
ValueToValueMapTy VMap;
for (BasicBlock *BB : BlocksInFunclet) {
ColorVector &ColorsForBB = BlockColors[BB];
// We don't need to do anything if the block is monochromatic.
size_t NumColorsForBB = ColorsForBB.size();
if (NumColorsForBB == 1)
continue;
DEBUG_WITH_TYPE("winehprepare-coloring",
dbgs() << " Cloning block \'" << BB->getName()
<< "\' for funclet \'" << FuncletPadBB->getName()
<< "\'.\n");
// Create a new basic block and copy instructions into it!
BasicBlock *CBB =
CloneBasicBlock(BB, VMap, Twine(".for.", FuncletPadBB->getName()));
// Insert the clone immediately after the original to ensure determinism
// and to keep the same relative ordering of any funclet's blocks.
CBB->insertInto(&F, BB->getNextNode());
// Add basic block mapping.
VMap[BB] = CBB;
// Record delta operations that we need to perform to our color mappings.
Orig2Clone.emplace_back(BB, CBB);
}
// If nothing was cloned, we're done cloning in this funclet.
if (Orig2Clone.empty())
continue;
// Update our color mappings to reflect that one block has lost a color and
// another has gained a color.
for (auto &BBMapping : Orig2Clone) {
BasicBlock *OldBlock = BBMapping.first;
BasicBlock *NewBlock = BBMapping.second;
BlocksInFunclet.push_back(NewBlock);
ColorVector &NewColors = BlockColors[NewBlock];
assert(NewColors.empty() && "A new block should only have one color!");
NewColors.push_back(FuncletPadBB);
DEBUG_WITH_TYPE("winehprepare-coloring",
dbgs() << " Assigned color \'" << FuncletPadBB->getName()
<< "\' to block \'" << NewBlock->getName()
<< "\'.\n");
BlocksInFunclet.erase(
std::remove(BlocksInFunclet.begin(), BlocksInFunclet.end(), OldBlock),
BlocksInFunclet.end());
ColorVector &OldColors = BlockColors[OldBlock];
OldColors.erase(
std::remove(OldColors.begin(), OldColors.end(), FuncletPadBB),
OldColors.end());
DEBUG_WITH_TYPE("winehprepare-coloring",
dbgs() << " Removed color \'" << FuncletPadBB->getName()
<< "\' from block \'" << OldBlock->getName()
<< "\'.\n");
}
// Loop over all of the instructions in this funclet, fixing up operand
// references as we go. This uses VMap to do all the hard work.
for (BasicBlock *BB : BlocksInFunclet)
// Loop over all instructions, fixing each one as we find it...
for (Instruction &I : *BB)
RemapInstruction(&I, VMap,
RF_IgnoreMissingEntries | RF_NoModuleLevelChanges);
auto UpdatePHIOnClonedBlock = [&](PHINode *PN, bool IsForOldBlock) {
unsigned NumPreds = PN->getNumIncomingValues();
for (unsigned PredIdx = 0, PredEnd = NumPreds; PredIdx != PredEnd;
++PredIdx) {
BasicBlock *IncomingBlock = PN->getIncomingBlock(PredIdx);
ColorVector &IncomingColors = BlockColors[IncomingBlock];
bool BlockInFunclet = IncomingColors.size() == 1 &&
IncomingColors.front() == FuncletPadBB;
if (IsForOldBlock != BlockInFunclet)
continue;
PN->removeIncomingValue(IncomingBlock, /*DeletePHIIfEmpty=*/false);
// Revisit the next entry.
--PredIdx;
--PredEnd;
}
};
for (auto &BBMapping : Orig2Clone) {
BasicBlock *OldBlock = BBMapping.first;
BasicBlock *NewBlock = BBMapping.second;
for (Instruction &OldI : *OldBlock) {
auto *OldPN = dyn_cast<PHINode>(&OldI);
if (!OldPN)
break;
UpdatePHIOnClonedBlock(OldPN, /*IsForOldBlock=*/true);
}
for (Instruction &NewI : *NewBlock) {
auto *NewPN = dyn_cast<PHINode>(&NewI);
if (!NewPN)
break;
UpdatePHIOnClonedBlock(NewPN, /*IsForOldBlock=*/false);
}
}
// Check to see if SuccBB has PHI nodes. If so, we need to add entries to
// the PHI nodes for NewBB now.
for (auto &BBMapping : Orig2Clone) {
BasicBlock *OldBlock = BBMapping.first;
BasicBlock *NewBlock = BBMapping.second;
for (BasicBlock *SuccBB : successors(NewBlock)) {
for (Instruction &SuccI : *SuccBB) {
auto *SuccPN = dyn_cast<PHINode>(&SuccI);
if (!SuccPN)
break;
// Ok, we have a PHI node. Figure out what the incoming value was for
// the OldBlock.
int OldBlockIdx = SuccPN->getBasicBlockIndex(OldBlock);
if (OldBlockIdx == -1)
break;
Value *IV = SuccPN->getIncomingValue(OldBlockIdx);
// Remap the value if necessary.
if (auto *Inst = dyn_cast<Instruction>(IV)) {
ValueToValueMapTy::iterator I = VMap.find(Inst);
if (I != VMap.end())
IV = I->second;
}
SuccPN->addIncoming(IV, NewBlock);
}
}
}
for (ValueToValueMapTy::value_type VT : VMap) {
// If there were values defined in BB that are used outside the funclet,
// then we now have to update all uses of the value to use either the
// original value, the cloned value, or some PHI derived value. This can
// require arbitrary PHI insertion, of which we are prepared to do, clean
// these up now.
SmallVector<Use *, 16> UsesToRename;
auto *OldI = dyn_cast<Instruction>(const_cast<Value *>(VT.first));
if (!OldI)
continue;
auto *NewI = cast<Instruction>(VT.second);
// Scan all uses of this instruction to see if it is used outside of its
// funclet, and if so, record them in UsesToRename.
for (Use &U : OldI->uses()) {
Instruction *UserI = cast<Instruction>(U.getUser());
BasicBlock *UserBB = UserI->getParent();
ColorVector &ColorsForUserBB = BlockColors[UserBB];
assert(!ColorsForUserBB.empty());
if (ColorsForUserBB.size() > 1 ||
*ColorsForUserBB.begin() != FuncletPadBB)
UsesToRename.push_back(&U);
}
// If there are no uses outside the block, we're done with this
// instruction.
if (UsesToRename.empty())
continue;
// We found a use of OldI outside of the funclet. Rename all uses of OldI
// that are outside its funclet to be uses of the appropriate PHI node
// etc.
SSAUpdater SSAUpdate;
SSAUpdate.Initialize(OldI->getType(), OldI->getName());
SSAUpdate.AddAvailableValue(OldI->getParent(), OldI);
SSAUpdate.AddAvailableValue(NewI->getParent(), NewI);
while (!UsesToRename.empty())
SSAUpdate.RewriteUseAfterInsertions(*UsesToRename.pop_back_val());
}
}
}
void WinEHPrepare::removeImplausibleTerminators(Function &F) {
// Remove implausible terminators and replace them with UnreachableInst.
for (auto &Funclet : FuncletBlocks) {
BasicBlock *FuncletPadBB = Funclet.first;
std::vector<BasicBlock *> &BlocksInFunclet = Funclet.second;
Instruction *FuncletPadInst = FuncletPadBB->getFirstNonPHI();
auto *CatchPad = dyn_cast<CatchPadInst>(FuncletPadInst);
auto *CleanupPad = dyn_cast<CleanupPadInst>(FuncletPadInst);
for (BasicBlock *BB : BlocksInFunclet) {
TerminatorInst *TI = BB->getTerminator();
// CatchPadInst and CleanupPadInst can't transfer control to a ReturnInst.
bool IsUnreachableRet = isa<ReturnInst>(TI) && (CatchPad || CleanupPad);
// The token consumed by a CatchReturnInst must match the funclet token.
bool IsUnreachableCatchret = false;
if (auto *CRI = dyn_cast<CatchReturnInst>(TI))
IsUnreachableCatchret = CRI->getCatchPad() != CatchPad;
// The token consumed by a CleanupReturnInst must match the funclet token.
bool IsUnreachableCleanupret = false;
if (auto *CRI = dyn_cast<CleanupReturnInst>(TI))
IsUnreachableCleanupret = CRI->getCleanupPad() != CleanupPad;
if (IsUnreachableRet || IsUnreachableCatchret ||
IsUnreachableCleanupret) {
// Loop through all of our successors and make sure they know that one
// of their predecessors is going away.
for (BasicBlock *SuccBB : TI->successors())
SuccBB->removePredecessor(BB);
new UnreachableInst(BB->getContext(), TI);
TI->eraseFromParent();
} else if (isa<InvokeInst>(TI)) {
// Invokes within a cleanuppad for the MSVC++ personality never
// transfer control to their unwind edge: the personality will
// terminate the program.
if (Personality == EHPersonality::MSVC_CXX && CleanupPad)
removeUnwindEdge(BB);
}
}
}
}
void WinEHPrepare::cleanupPreparedFunclets(Function &F) {
// Clean-up some of the mess we made by removing useles PHI nodes, trivial
// branches, etc.
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) {
BasicBlock *BB = &*FI++;
SimplifyInstructionsInBlock(BB);
ConstantFoldTerminator(BB, /*DeleteDeadConditions=*/true);
MergeBlockIntoPredecessor(BB);
}
// We might have some unreachable blocks after cleaning up some impossible
// control flow.
removeUnreachableBlocks(F);
}
void WinEHPrepare::verifyPreparedFunclets(Function &F) {
// Recolor the CFG to verify that all is well.
for (BasicBlock &BB : F) {
size_t NumColors = BlockColors[&BB].size();
assert(NumColors == 1 && "Expected monochromatic BB!");
if (NumColors == 0)
report_fatal_error("Uncolored BB!");
if (NumColors > 1)
report_fatal_error("Multicolor BB!");
if (!DisableDemotion) {
bool EHPadHasPHI = BB.isEHPad() && isa<PHINode>(BB.begin());
assert(!EHPadHasPHI && "EH Pad still has a PHI!");
if (EHPadHasPHI)
report_fatal_error("EH Pad still has a PHI!");
}
}
}
bool WinEHPrepare::prepareExplicitEH(Function &F) {
// Remove unreachable blocks. It is not valuable to assign them a color and
// their existence can trick us into thinking values are alive when they are
// not.
removeUnreachableBlocks(F);
replaceTerminatePadWithCleanup(F);
// Determine which blocks are reachable from which funclet entries.
colorFunclets(F);
cloneCommonBlocks(F);
if (!DisableDemotion)
demotePHIsOnFunclets(F);
if (!DisableCleanups) {
removeImplausibleTerminators(F);
cleanupPreparedFunclets(F);
}
verifyPreparedFunclets(F);
BlockColors.clear();
FuncletBlocks.clear();
return true;
}
// TODO: Share loads when one use dominates another, or when a catchpad exit
// dominates uses (needs dominators).
AllocaInst *WinEHPrepare::insertPHILoads(PHINode *PN, Function &F) {
BasicBlock *PHIBlock = PN->getParent();
AllocaInst *SpillSlot = nullptr;
Instruction *EHPad = PHIBlock->getFirstNonPHI();
if (!isa<TerminatorInst>(EHPad)) {
// If the EHPad isn't a terminator, then we can insert a load in this block
// that will dominate all uses.
SpillSlot = new AllocaInst(PN->getType(), nullptr,
Twine(PN->getName(), ".wineh.spillslot"),
&F.getEntryBlock().front());
Value *V = new LoadInst(SpillSlot, Twine(PN->getName(), ".wineh.reload"),
&*PHIBlock->getFirstInsertionPt());
PN->replaceAllUsesWith(V);
return SpillSlot;
}
// Otherwise, we have a PHI on a terminator EHPad, and we give up and insert
// loads of the slot before every use.
DenseMap<BasicBlock *, Value *> Loads;
for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end();
UI != UE;) {
Use &U = *UI++;
auto *UsingInst = cast<Instruction>(U.getUser());
if (isa<PHINode>(UsingInst) && UsingInst->getParent()->isEHPad()) {
// Use is on an EH pad phi. Leave it alone; we'll insert loads and
// stores for it separately.
continue;
}
replaceUseWithLoad(PN, U, SpillSlot, Loads, F);
}
return SpillSlot;
}
// TODO: improve store placement. Inserting at def is probably good, but need
// to be careful not to introduce interfering stores (needs liveness analysis).
// TODO: identify related phi nodes that can share spill slots, and share them
// (also needs liveness).
void WinEHPrepare::insertPHIStores(PHINode *OriginalPHI,
AllocaInst *SpillSlot) {
// Use a worklist of (Block, Value) pairs -- the given Value needs to be
// stored to the spill slot by the end of the given Block.
SmallVector<std::pair<BasicBlock *, Value *>, 4> Worklist;
Worklist.push_back({OriginalPHI->getParent(), OriginalPHI});
while (!Worklist.empty()) {
BasicBlock *EHBlock;
Value *InVal;
std::tie(EHBlock, InVal) = Worklist.pop_back_val();
PHINode *PN = dyn_cast<PHINode>(InVal);
if (PN && PN->getParent() == EHBlock) {
// The value is defined by another PHI we need to remove, with no room to
// insert a store after the PHI, so each predecessor needs to store its
// incoming value.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i < e; ++i) {
Value *PredVal = PN->getIncomingValue(i);
// Undef can safely be skipped.
if (isa<UndefValue>(PredVal))
continue;
insertPHIStore(PN->getIncomingBlock(i), PredVal, SpillSlot, Worklist);
}
} else {
// We need to store InVal, which dominates EHBlock, but can't put a store
// in EHBlock, so need to put stores in each predecessor.
for (BasicBlock *PredBlock : predecessors(EHBlock)) {
insertPHIStore(PredBlock, InVal, SpillSlot, Worklist);
}
}
}
}
void WinEHPrepare::insertPHIStore(
BasicBlock *PredBlock, Value *PredVal, AllocaInst *SpillSlot,
SmallVectorImpl<std::pair<BasicBlock *, Value *>> &Worklist) {
if (PredBlock->isEHPad() &&
isa<TerminatorInst>(PredBlock->getFirstNonPHI())) {
// Pred is unsplittable, so we need to queue it on the worklist.
Worklist.push_back({PredBlock, PredVal});
return;
}
// Otherwise, insert the store at the end of the basic block.
new StoreInst(PredVal, SpillSlot, PredBlock->getTerminator());
}
void WinEHPrepare::replaceUseWithLoad(Value *V, Use &U, AllocaInst *&SpillSlot,
DenseMap<BasicBlock *, Value *> &Loads,
Function &F) {
// Lazilly create the spill slot.
if (!SpillSlot)
SpillSlot = new AllocaInst(V->getType(), nullptr,
Twine(V->getName(), ".wineh.spillslot"),
&F.getEntryBlock().front());
auto *UsingInst = cast<Instruction>(U.getUser());
if (auto *UsingPHI = dyn_cast<PHINode>(UsingInst)) {
// If this is a PHI node, we can't insert a load of the value before
// the use. Instead insert the load in the predecessor block
// corresponding to the incoming value.
//
// Note that if there are multiple edges from a basic block to this
// PHI node that we cannot have multiple loads. The problem is that
// the resulting PHI node will have multiple values (from each load)
// coming in from the same block, which is illegal SSA form.
// For this reason, we keep track of and reuse loads we insert.
BasicBlock *IncomingBlock = UsingPHI->getIncomingBlock(U);
if (auto *CatchRet =
dyn_cast<CatchReturnInst>(IncomingBlock->getTerminator())) {
// Putting a load above a catchret and use on the phi would still leave
// a cross-funclet def/use. We need to split the edge, change the
// catchret to target the new block, and put the load there.
BasicBlock *PHIBlock = UsingInst->getParent();
BasicBlock *NewBlock = SplitEdge(IncomingBlock, PHIBlock);
// SplitEdge gives us:
// IncomingBlock:
// ...
// br label %NewBlock
// NewBlock:
// catchret label %PHIBlock
// But we need:
// IncomingBlock:
// ...
// catchret label %NewBlock
// NewBlock:
// br label %PHIBlock
// So move the terminators to each others' blocks and swap their
// successors.
BranchInst *Goto = cast<BranchInst>(IncomingBlock->getTerminator());
Goto->removeFromParent();
CatchRet->removeFromParent();
IncomingBlock->getInstList().push_back(CatchRet);
NewBlock->getInstList().push_back(Goto);
Goto->setSuccessor(0, PHIBlock);
CatchRet->setSuccessor(NewBlock);
// Update the color mapping for the newly split edge.
ColorVector &ColorsForPHIBlock = BlockColors[PHIBlock];
BlockColors[NewBlock] = ColorsForPHIBlock;
for (BasicBlock *FuncletPad : ColorsForPHIBlock)
FuncletBlocks[FuncletPad].push_back(NewBlock);
// Treat the new block as incoming for load insertion.
IncomingBlock = NewBlock;
}
Value *&Load = Loads[IncomingBlock];
// Insert the load into the predecessor block
if (!Load)
Load = new LoadInst(SpillSlot, Twine(V->getName(), ".wineh.reload"),
/*Volatile=*/false, IncomingBlock->getTerminator());
U.set(Load);
} else {
// Reload right before the old use.
auto *Load = new LoadInst(SpillSlot, Twine(V->getName(), ".wineh.reload"),
/*Volatile=*/false, UsingInst);
U.set(Load);
}
}
void WinEHFuncInfo::addIPToStateRange(const InvokeInst *II,
MCSymbol *InvokeBegin,
MCSymbol *InvokeEnd) {
assert(InvokeStateMap.count(II) &&
"should get invoke with precomputed state");
LabelToStateMap[InvokeBegin] = std::make_pair(InvokeStateMap[II], InvokeEnd);
}
Reference in New Issue View Git Blame Copy Permalink