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llvm-mirror/lib/CodeGen/WinEHPrepare.cpp
Kazu Hirata 38cc9ea5cc [CodeGen] Use range-based for loops (NFC)
2021-02-21 19:58:07 -08:00

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//===-- WinEHPrepare - Prepare exception handling for code generation ---===//
//
// 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 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/ADT/DenseMap.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/EHPersonalities.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/WinEHFuncInfo.h"
#include "llvm/IR/Verifier.h"
#include "llvm/InitializePasses.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.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 scopes"),
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));
static cl::opt<bool> DemoteCatchSwitchPHIOnlyOpt(
"demote-catchswitch-only", cl::Hidden,
cl::desc("Demote catchswitch BBs only (for wasm EH)"), cl::init(false));
namespace {
class WinEHPrepare : public FunctionPass {
public:
static char ID; // Pass identification, replacement for typeid.
WinEHPrepare(bool DemoteCatchSwitchPHIOnly = false)
: FunctionPass(ID), DemoteCatchSwitchPHIOnly(DemoteCatchSwitchPHIOnly) {}
bool runOnFunction(Function &Fn) override;
bool doFinalization(Module &M) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
StringRef 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 colorFunclets(Function &F);
void demotePHIsOnFunclets(Function &F, bool DemoteCatchSwitchPHIOnly);
void cloneCommonBlocks(Function &F);
void removeImplausibleInstructions(Function &F);
void cleanupPreparedFunclets(Function &F);
void verifyPreparedFunclets(Function &F);
bool DemoteCatchSwitchPHIOnly;
// All fields are reset by runOnFunction.
EHPersonality Personality = EHPersonality::Unknown;
const DataLayout *DL = nullptr;
DenseMap<BasicBlock *, ColorVector> BlockColors;
MapVector<BasicBlock *, std::vector<BasicBlock *>> FuncletBlocks;
};
} // end anonymous namespace
char WinEHPrepare::ID = 0;
INITIALIZE_PASS(WinEHPrepare, DEBUG_TYPE, "Prepare Windows exceptions",
false, false)
FunctionPass *llvm::createWinEHPass(bool DemoteCatchSwitchPHIOnly) {
return new WinEHPrepare(DemoteCatchSwitchPHIOnly);
}
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 scope-based personality.
if (!isScopedEHPersonality(Personality))
return false;
DL = &Fn.getParent()->getDataLayout();
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 (auto *AI =
dyn_cast<AllocaInst>(CPI->getArgOperand(2)->stripPointerCasts()))
HT.CatchObj.Alloca = AI;
else
HT.CatchObj.Alloca = nullptr;
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 Instruction *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();
}
// Starting from a EHPad, Backward walk through control-flow graph
// to produce two primary outputs:
// FuncInfo.EHPadStateMap[] and FuncInfo.CxxUnwindMap[]
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;
// MSVC FrameHandler3/4 on x64&Arm64 expect Catch Handlers in $tryMap$
// stored in pre-order (outer first, inner next), not post-order
// Add to map here. Fix the CatchHigh after children are processed
const Module *Mod = BB->getParent()->getParent();
bool IsPreOrder = Triple(Mod->getTargetTriple()).isArch64Bit();
if (IsPreOrder)
addTryBlockMapEntry(FuncInfo, TryLow, TryHigh, CatchLow, Handlers);
unsigned TBMEIdx = FuncInfo.TryBlockMap.size() - 1;
for (const auto *CatchPad : Handlers) {
FuncInfo.FuncletBaseStateMap[CatchPad] = CatchLow;
for (const User *U : CatchPad->users()) {
const auto *UserI = cast<Instruction>(U);
if (auto *InnerCatchSwitch = dyn_cast<CatchSwitchInst>(UserI)) {
BasicBlock *UnwindDest = InnerCatchSwitch->getUnwindDest();
if (!UnwindDest || UnwindDest == CatchSwitch->getUnwindDest())
calculateCXXStateNumbers(FuncInfo, UserI, CatchLow);
}
if (auto *InnerCleanupPad = dyn_cast<CleanupPadInst>(UserI)) {
BasicBlock *UnwindDest = getCleanupRetUnwindDest(InnerCleanupPad);
// If a nested cleanup pad reports a null unwind destination and the
// enclosing catch pad doesn't it must be post-dominated by an
// unreachable instruction.
if (!UnwindDest || UnwindDest == CatchSwitch->getUnwindDest())
calculateCXXStateNumbers(FuncInfo, UserI, CatchLow);
}
}
}
int CatchHigh = FuncInfo.getLastStateNumber();
// Now child Catches are processed, update CatchHigh
if (IsPreOrder)
FuncInfo.TryBlockMap[TBMEIdx].CatchHigh = CatchHigh;
else // PostOrder
addTryBlockMapEntry(FuncInfo, TryLow, TryHigh, CatchHigh, Handlers);
LLVM_DEBUG(dbgs() << "TryLow[" << BB->getName() << "]: " << TryLow << '\n');
LLVM_DEBUG(dbgs() << "TryHigh[" << BB->getName() << "]: " << TryHigh
<< '\n');
LLVM_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;
LLVM_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;
}
// Starting from a EHPad, Backward walk through control-flow graph
// to produce two primary outputs:
// FuncInfo.EHPadStateMap[] and FuncInfo.SEHUnwindMap[]
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;
LLVM_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 (auto *InnerCatchSwitch = dyn_cast<CatchSwitchInst>(UserI)) {
BasicBlock *UnwindDest = InnerCatchSwitch->getUnwindDest();
if (!UnwindDest || UnwindDest == CatchSwitch->getUnwindDest())
calculateSEHStateNumbers(FuncInfo, UserI, ParentState);
}
if (auto *InnerCleanupPad = dyn_cast<CleanupPadInst>(UserI)) {
BasicBlock *UnwindDest = getCleanupRetUnwindDest(InnerCleanupPad);
// If a nested cleanup pad reports a null unwind destination and the
// enclosing catch pad doesn't it must be post-dominated by an
// unreachable instruction.
if (!UnwindDest || UnwindDest == CatchSwitch->getUnwindDest())
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;
LLVM_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 HandlerParentState,
int TryParentState, ClrHandlerType HandlerType,
uint32_t TypeToken, const BasicBlock *Handler) {
ClrEHUnwindMapEntry Entry;
Entry.HandlerParentState = HandlerParentState;
Entry.TryParentState = TryParentState;
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;
// This numbering assigns one state number to each catchpad and cleanuppad.
// It also computes two tree-like relations over states:
// 1) Each state has a "HandlerParentState", which is the state of the next
// outer handler enclosing this state's handler (same as nearest ancestor
// per the ParentPad linkage on EH pads, but skipping over catchswitches).
// 2) Each state has a "TryParentState", which:
// a) for a catchpad that's not the last handler on its catchswitch, is
// the state of the next catchpad on that catchswitch
// b) for all other pads, is the state of the pad whose try region is the
// next outer try region enclosing this state's try region. The "try
// regions are not present as such in the IR, but will be inferred
// based on the placement of invokes and pads which reach each other
// by exceptional exits
// Catchswitches do not get their own states, but each gets mapped to the
// state of its first catchpad.
// Step one: walk down from outermost to innermost funclets, assigning each
// catchpad and cleanuppad a state number. Add an entry to the
// ClrEHUnwindMap for each state, recording its HandlerParentState and
// handler attributes. Record the TryParentState as well for each catchpad
// that's not the last on its catchswitch, but initialize all other entries'
// TryParentStates to a sentinel -1 value that the next pass will update.
// Seed a worklist with pads that have no parent.
SmallVector<std::pair<const Instruction *, int>, 8> Worklist;
for (const BasicBlock &BB : *Fn) {
const Instruction *FirstNonPHI = BB.getFirstNonPHI();
const Value *ParentPad;
if (const auto *CPI = dyn_cast<CleanupPadInst>(FirstNonPHI))
ParentPad = CPI->getParentPad();
else if (const auto *CSI = dyn_cast<CatchSwitchInst>(FirstNonPHI))
ParentPad = CSI->getParentPad();
else
continue;
if (isa<ConstantTokenNone>(ParentPad))
Worklist.emplace_back(FirstNonPHI, -1);
}
// Use the worklist to visit all pads, from outer to inner. Record
// HandlerParentState for all pads. Record TryParentState only for catchpads
// that aren't the last on their catchswitch (setting all other entries'
// TryParentStates to an initial value of -1). This loop is also responsible
// for setting the EHPadStateMap entry for all catchpads, cleanuppads, and
// catchswitches.
while (!Worklist.empty()) {
const Instruction *Pad;
int HandlerParentState;
std::tie(Pad, HandlerParentState) = Worklist.pop_back_val();
if (const auto *Cleanup = dyn_cast<CleanupPadInst>(Pad)) {
// Create the entry for this cleanup with the appropriate handler
// properties. Finally and fault handlers are distinguished by arity.
ClrHandlerType HandlerType =
(Cleanup->getNumArgOperands() ? ClrHandlerType::Fault
: ClrHandlerType::Finally);
int CleanupState = addClrEHHandler(FuncInfo, HandlerParentState, -1,
HandlerType, 0, Pad->getParent());
// Queue any child EH pads on the worklist.
for (const User *U : Cleanup->users())
if (const auto *I = dyn_cast<Instruction>(U))
if (I->isEHPad())
Worklist.emplace_back(I, CleanupState);
// Remember this pad's state.
FuncInfo.EHPadStateMap[Cleanup] = CleanupState;
} else {
// Walk the handlers of this catchswitch in reverse order since all but
// the last need to set the following one as its TryParentState.
const auto *CatchSwitch = cast<CatchSwitchInst>(Pad);
int CatchState = -1, FollowerState = -1;
SmallVector<const BasicBlock *, 4> CatchBlocks(CatchSwitch->handlers());
for (auto CBI = CatchBlocks.rbegin(), CBE = CatchBlocks.rend();
CBI != CBE; ++CBI, FollowerState = CatchState) {
const BasicBlock *CatchBlock = *CBI;
// Create the entry for this catch with the appropriate handler
// properties.
const auto *Catch = cast<CatchPadInst>(CatchBlock->getFirstNonPHI());
uint32_t TypeToken = static_cast<uint32_t>(
cast<ConstantInt>(Catch->getArgOperand(0))->getZExtValue());
CatchState =
addClrEHHandler(FuncInfo, HandlerParentState, FollowerState,
ClrHandlerType::Catch, TypeToken, CatchBlock);
// Queue any child EH pads on the worklist.
for (const User *U : Catch->users())
if (const auto *I = dyn_cast<Instruction>(U))
if (I->isEHPad())
Worklist.emplace_back(I, CatchState);
// Remember this catch's state.
FuncInfo.EHPadStateMap[Catch] = CatchState;
}
// Associate the catchswitch with the state of its first catch.
assert(CatchSwitch->getNumHandlers());
FuncInfo.EHPadStateMap[CatchSwitch] = CatchState;
}
}
// Step two: record the TryParentState of each state. For cleanuppads that
// don't have cleanuprets, we may need to infer this from their child pads,
// so visit pads in descendant-most to ancestor-most order.
for (auto Entry = FuncInfo.ClrEHUnwindMap.rbegin(),
End = FuncInfo.ClrEHUnwindMap.rend();
Entry != End; ++Entry) {
const Instruction *Pad =
Entry->Handler.get<const BasicBlock *>()->getFirstNonPHI();
// For most pads, the TryParentState is the state associated with the
// unwind dest of exceptional exits from it.
const BasicBlock *UnwindDest;
if (const auto *Catch = dyn_cast<CatchPadInst>(Pad)) {
// If a catch is not the last in its catchswitch, its TryParentState is
// the state associated with the next catch in the switch, even though
// that's not the unwind dest of exceptions escaping the catch. Those
// cases were already assigned a TryParentState in the first pass, so
// skip them.
if (Entry->TryParentState != -1)
continue;
// Otherwise, get the unwind dest from the catchswitch.
UnwindDest = Catch->getCatchSwitch()->getUnwindDest();
} else {
const auto *Cleanup = cast<CleanupPadInst>(Pad);
UnwindDest = nullptr;
for (const User *U : Cleanup->users()) {
if (auto *CleanupRet = dyn_cast<CleanupReturnInst>(U)) {
// Common and unambiguous case -- cleanupret indicates cleanup's
// unwind dest.
UnwindDest = CleanupRet->getUnwindDest();
break;
}
// Get an unwind dest for the user
const BasicBlock *UserUnwindDest = nullptr;
if (auto *Invoke = dyn_cast<InvokeInst>(U)) {
UserUnwindDest = Invoke->getUnwindDest();
} else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(U)) {
UserUnwindDest = CatchSwitch->getUnwindDest();
} else if (auto *ChildCleanup = dyn_cast<CleanupPadInst>(U)) {
int UserState = FuncInfo.EHPadStateMap[ChildCleanup];
int UserUnwindState =
FuncInfo.ClrEHUnwindMap[UserState].TryParentState;
if (UserUnwindState != -1)
UserUnwindDest = FuncInfo.ClrEHUnwindMap[UserUnwindState]
.Handler.get<const BasicBlock *>();
}
// Not having an unwind dest for this user might indicate that it
// doesn't unwind, so can't be taken as proof that the cleanup itself
// may unwind to caller (see e.g. SimplifyUnreachable and
// RemoveUnwindEdge).
if (!UserUnwindDest)
continue;
// Now we have an unwind dest for the user, but we need to see if it
// unwinds all the way out of the cleanup or if it stays within it.
const Instruction *UserUnwindPad = UserUnwindDest->getFirstNonPHI();
const Value *UserUnwindParent;
if (auto *CSI = dyn_cast<CatchSwitchInst>(UserUnwindPad))
UserUnwindParent = CSI->getParentPad();
else
UserUnwindParent =
cast<CleanupPadInst>(UserUnwindPad)->getParentPad();
// The unwind stays within the cleanup iff it targets a child of the
// cleanup.
if (UserUnwindParent == Cleanup)
continue;
// This unwind exits the cleanup, so its dest is the cleanup's dest.
UnwindDest = UserUnwindDest;
break;
}
}
// Record the state of the unwind dest as the TryParentState.
int UnwindDestState;
// If UnwindDest is null at this point, either the pad in question can
// be exited by unwind to caller, or it cannot be exited by unwind. In
// either case, reporting such cases as unwinding to caller is correct.
// This can lead to EH tables that "look strange" -- if this pad's is in
// a parent funclet which has other children that do unwind to an enclosing
// pad, the try region for this pad will be missing the "duplicate" EH
// clause entries that you'd expect to see covering the whole parent. That
// should be benign, since the unwind never actually happens. If it were
// an issue, we could add a subsequent pass that pushes unwind dests down
// from parents that have them to children that appear to unwind to caller.
if (!UnwindDest) {
UnwindDestState = -1;
} else {
UnwindDestState = FuncInfo.EHPadStateMap[UnwindDest->getFirstNonPHI()];
}
Entry->TryParentState = UnwindDestState;
}
// Step three: transfer information from pads to invokes.
calculateStateNumbersForInvokes(Fn, FuncInfo);
}
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 WinEHPrepare::demotePHIsOnFunclets(Function &F,
bool DemoteCatchSwitchPHIOnly) {
// Strip PHI nodes off of EH pads.
SmallVector<PHINode *, 16> PHINodes;
for (BasicBlock &BB : make_early_inc_range(F)) {
if (!BB.isEHPad())
continue;
if (DemoteCatchSwitchPHIOnly && !isa<CatchSwitchInst>(BB.getFirstNonPHI()))
continue;
for (Instruction &I : make_early_inc_range(BB)) {
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 propagate both the new instructions
// *and* the new basic blocks themselves.
for (auto &Funclets : FuncletBlocks) {
BasicBlock *FuncletPadBB = Funclets.first;
std::vector<BasicBlock *> &BlocksInFunclet = Funclets.second;
Value *FuncletToken;
if (FuncletPadBB == &F.getEntryBlock())
FuncletToken = ConstantTokenNone::get(F.getContext());
else
FuncletToken = FuncletPadBB->getFirstNonPHI();
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");
llvm::erase_value(BlocksInFunclet, OldBlock);
ColorVector &OldColors = BlockColors[OldBlock];
llvm::erase_value(OldColors, FuncletPadBB);
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_IgnoreMissingLocals | RF_NoModuleLevelChanges);
// Catchrets targeting cloned blocks need to be updated separately from
// the loop above because they are not in the current funclet.
SmallVector<CatchReturnInst *, 2> FixupCatchrets;
for (auto &BBMapping : Orig2Clone) {
BasicBlock *OldBlock = BBMapping.first;
BasicBlock *NewBlock = BBMapping.second;
FixupCatchrets.clear();
for (BasicBlock *Pred : predecessors(OldBlock))
if (auto *CatchRet = dyn_cast<CatchReturnInst>(Pred->getTerminator()))
if (CatchRet->getCatchSwitchParentPad() == FuncletToken)
FixupCatchrets.push_back(CatchRet);
for (CatchReturnInst *CatchRet : FixupCatchrets)
CatchRet->setSuccessor(NewBlock);
}
auto UpdatePHIOnClonedBlock = [&](PHINode *PN, bool IsForOldBlock) {
unsigned NumPreds = PN->getNumIncomingValues();
for (unsigned PredIdx = 0, PredEnd = NumPreds; PredIdx != PredEnd;
++PredIdx) {
BasicBlock *IncomingBlock = PN->getIncomingBlock(PredIdx);
bool EdgeTargetsFunclet;
if (auto *CRI =
dyn_cast<CatchReturnInst>(IncomingBlock->getTerminator())) {
EdgeTargetsFunclet = (CRI->getCatchSwitchParentPad() == FuncletToken);
} else {
ColorVector &IncomingColors = BlockColors[IncomingBlock];
assert(!IncomingColors.empty() && "Block not colored!");
assert((IncomingColors.size() == 1 ||
llvm::all_of(IncomingColors,
[&](BasicBlock *Color) {
return Color != FuncletPadBB;
})) &&
"Cloning should leave this funclet's blocks monochromatic");
EdgeTargetsFunclet = (IncomingColors.front() == FuncletPadBB);
}
if (IsForOldBlock != EdgeTargetsFunclet)
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 (PHINode &OldPN : OldBlock->phis()) {
UpdatePHIOnClonedBlock(&OldPN, /*IsForOldBlock=*/true);
}
for (PHINode &NewPN : NewBlock->phis()) {
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 (PHINode &SuccPN : SuccBB->phis()) {
// 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::removeImplausibleInstructions(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 *FirstNonPHI = FuncletPadBB->getFirstNonPHI();
auto *FuncletPad = dyn_cast<FuncletPadInst>(FirstNonPHI);
auto *CatchPad = dyn_cast_or_null<CatchPadInst>(FuncletPad);
auto *CleanupPad = dyn_cast_or_null<CleanupPadInst>(FuncletPad);
for (BasicBlock *BB : BlocksInFunclet) {
for (Instruction &I : *BB) {
auto *CB = dyn_cast<CallBase>(&I);
if (!CB)
continue;
Value *FuncletBundleOperand = nullptr;
if (auto BU = CB->getOperandBundle(LLVMContext::OB_funclet))
FuncletBundleOperand = BU->Inputs.front();
if (FuncletBundleOperand == FuncletPad)
continue;
// Skip call sites which are nounwind intrinsics or inline asm.
auto *CalledFn =
dyn_cast<Function>(CB->getCalledOperand()->stripPointerCasts());
if (CalledFn && ((CalledFn->isIntrinsic() && CB->doesNotThrow()) ||
CB->isInlineAsm()))
continue;
// This call site was not part of this funclet, remove it.
if (isa<InvokeInst>(CB)) {
// Remove the unwind edge if it was an invoke.
removeUnwindEdge(BB);
// Get a pointer to the new call.
BasicBlock::iterator CallI =
std::prev(BB->getTerminator()->getIterator());
auto *CI = cast<CallInst>(&*CallI);
changeToUnreachable(CI, /*UseLLVMTrap=*/false);
} else {
changeToUnreachable(&I, /*UseLLVMTrap=*/false);
}
// There are no more instructions in the block (except for unreachable),
// we are done.
break;
}
Instruction *TI = BB->getTerminator();
// CatchPadInst and CleanupPadInst can't transfer control to a ReturnInst.
bool IsUnreachableRet = isa<ReturnInst>(TI) && FuncletPad;
// 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) {
changeToUnreachable(TI, /*UseLLVMTrap=*/false);
} else if (isa<InvokeInst>(TI)) {
if (Personality == EHPersonality::MSVC_CXX && CleanupPad) {
// Invokes within a cleanuppad for the MSVC++ personality never
// transfer control to their unwind edge: the personality will
// terminate the program.
removeUnwindEdge(BB);
}
}
}
}
}
void WinEHPrepare::cleanupPreparedFunclets(Function &F) {
// Clean-up some of the mess we made by removing useles PHI nodes, trivial
// branches, etc.
for (BasicBlock &BB : llvm::make_early_inc_range(F)) {
SimplifyInstructionsInBlock(&BB);
ConstantFoldTerminator(&BB, /*DeleteDeadConditions=*/true);
MergeBlockIntoPredecessor(&BB);
}
// We might have some unreachable blocks after cleaning up some impossible
// control flow.
removeUnreachableBlocks(F);
}
#ifndef NDEBUG
void WinEHPrepare::verifyPreparedFunclets(Function &F) {
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!");
assert((DisableDemotion || !(BB.isEHPad() && isa<PHINode>(BB.begin()))) &&
"EH Pad still has a PHI!");
}
}
#endif
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);
// Determine which blocks are reachable from which funclet entries.
colorFunclets(F);
cloneCommonBlocks(F);
if (!DisableDemotion)
demotePHIsOnFunclets(F, DemoteCatchSwitchPHIOnly ||
DemoteCatchSwitchPHIOnlyOpt);
if (!DisableCleanups) {
assert(!verifyFunction(F, &dbgs()));
removeImplausibleInstructions(F);
assert(!verifyFunction(F, &dbgs()));
cleanupPreparedFunclets(F);
}
LLVM_DEBUG(verifyPreparedFunclets(F));
// Recolor the CFG to verify that all is well.
LLVM_DEBUG(colorFunclets(F));
LLVM_DEBUG(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 (!EHPad->isTerminator()) {
// 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(), DL->getAllocaAddrSpace(), nullptr,
Twine(PN->getName(), ".wineh.spillslot"),
&F.getEntryBlock().front());
Value *V = new LoadInst(PN->getType(), 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 (Use &U : llvm::make_early_inc_range(PN->uses())) {
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() && PredBlock->getFirstNonPHI()->isTerminator()) {
// 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(), DL->getAllocaAddrSpace(), 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.
// Grab a reference to the ColorVector to be inserted before getting the
// reference to the vector we are copying because inserting the new
// element in BlockColors might cause the map to be reallocated.
ColorVector &ColorsForNewBlock = BlockColors[NewBlock];
ColorVector &ColorsForPHIBlock = BlockColors[PHIBlock];
ColorsForNewBlock = 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(V->getType(), SpillSlot,
Twine(V->getName(), ".wineh.reload"),
/*isVolatile=*/false, IncomingBlock->getTerminator());
U.set(Load);
} else {
// Reload right before the old use.
auto *Load = new LoadInst(V->getType(), SpillSlot,
Twine(V->getName(), ".wineh.reload"),
/*isVolatile=*/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);
}
WinEHFuncInfo::WinEHFuncInfo() {}
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