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llvm-mirror/lib/CodeGen/WinEHPrepare.cpp
David Majnemer 1fad37bd8d [WinEH] Don't miscompile cleanups which conditionally unwind to caller 
A cleanup can have paths which unwind or end up in unreachable.
If there is an unreachable path *and* a path which unwinds to caller,
we would mistakenly inject an unwind path to a catchswitch on the
unreachable path.  This results in a verifier assertion firing because
the cleanup unwinds to two different places: to the caller and to the
catchswitch.

This occured because we used getCleanupRetUnwindDest to determine if the
cleanuppad had no cleanuprets.
This is incorrect, getCleanupRetUnwindDest returns null for cleanuprets
which unwind to caller.

llvm-svn: 258651
2016-01-23 23:54:33 +00:00

1336 lines
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//===-- 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/DenseMap.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/EHPersonalities.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/WinEHFuncInfo.h"
#include "llvm/IR/Verifier.h"
#include "llvm/MC/MCSymbol.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 colorFunclets(Function &F);
void demotePHIsOnFunclets(Function &F);
void cloneCommonBlocks(Function &F);
void removeImplausibleInstructions(Function &F);
void cleanupPreparedFunclets(Function &F);
void fixupNoReturnCleanupPads(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 (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 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 (auto *InnerCatchSwitch = dyn_cast<CatchSwitchInst>(UserI))
if (InnerCatchSwitch->getUnwindDest() == CatchSwitch->getUnwindDest())
calculateCXXStateNumbers(FuncInfo, UserI, CatchLow);
if (auto *InnerCleanupPad = dyn_cast<CleanupPadInst>(UserI))
if (getCleanupRetUnwindDest(InnerCleanupPad) ==
CatchSwitch->getUnwindDest())
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 (auto *InnerCatchSwitch = dyn_cast<CatchSwitchInst>(UserI))
if (InnerCatchSwitch->getUnwindDest() == CatchSwitch->getUnwindDest())
calculateSEHStateNumbers(FuncInfo, UserI, ParentState);
if (auto *InnerCleanupPad = dyn_cast<CleanupPadInst>(UserI))
if (getCleanupRetUnwindDest(InnerCleanupPad) ==
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;
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. Finaly 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);
FuncletBlocks.clear();
// 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) {
// 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;
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");
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);
// 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 (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::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) {
CallSite CS(&I);
if (!CS)
continue;
Value *FuncletBundleOperand = nullptr;
if (auto BU = CS.getOperandBundle(LLVMContext::OB_funclet))
FuncletBundleOperand = BU->Inputs.front();
if (FuncletBundleOperand == FuncletPad)
continue;
// Skip call sites which are nounwind intrinsics.
auto *CalledFn =
dyn_cast<Function>(CS.getCalledValue()->stripPointerCasts());
if (CalledFn && CalledFn->isIntrinsic() && CS.doesNotThrow())
continue;
// This call site was not part of this funclet, remove it.
if (CS.isInvoke()) {
// 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;
}
TerminatorInst *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 (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);
}
// Cleanuppads which are postdominated by unreachable will not unwind to any
// catchswitches, making them dead. This is problematic if the original source
// had a catch clause which could legitimately catch the exception, causing the
// cleanup to run.
//
// This is only a problem for C++ where down-stream catches cause cleanups to
// run.
void WinEHPrepare::fixupNoReturnCleanupPads(Function &F) {
// We only need to do this for C++ personality routines,
// skip this work for all others.
if (Personality != EHPersonality::MSVC_CXX)
return;
// Do a quick sanity check on the color map before we throw it away so as to
// avoid hiding latent bugs.
DEBUG(verifyPreparedFunclets(F));
// Re-color the funclets because cleanupPreparedFunclets might have
// invalidated FuncletBlocks.
colorFunclets(F);
// We create a unique catchswitch for each parent it will be nested within.
SmallDenseMap<Value *, CatchSwitchInst *> NewCatchSwitches;
// Create a new catchswitch+catchpad where the catchpad is post-dominated by
// unreachable.
auto GetOrCreateCatchSwitch = [&](Value *ParentPad) {
auto &CatchSwitch = NewCatchSwitches[ParentPad];
if (CatchSwitch)
return CatchSwitch;
auto *ParentBB = isa<ConstantTokenNone>(ParentPad)
? &F.getEntryBlock()
: cast<Instruction>(ParentPad)->getParent();
StringRef NameSuffix = ParentBB->getName();
BasicBlock *CatchSwitchBB = BasicBlock::Create(
F.getContext(), Twine("catchswitchbb.for.", NameSuffix));
CatchSwitchBB->insertInto(&F, ParentBB->getNextNode());
CatchSwitch = CatchSwitchInst::Create(ParentPad, /*UnwindDest=*/nullptr,
/*NumHandlers=*/1,
Twine("catchswitch.for.", NameSuffix),
CatchSwitchBB);
BasicBlock *CatchPadBB = BasicBlock::Create(
F.getContext(), Twine("catchpadbb.for.", NameSuffix));
CatchPadBB->insertInto(&F, CatchSwitchBB->getNextNode());
Value *CatchPadArgs[] = {
Constant::getNullValue(Type::getInt8PtrTy(F.getContext())),
ConstantInt::get(Type::getInt32Ty(F.getContext()), 64),
Constant::getNullValue(Type::getInt8PtrTy(F.getContext())),
};
CatchPadInst::Create(CatchSwitch, CatchPadArgs,
Twine("catchpad.for.", NameSuffix), CatchPadBB);
new UnreachableInst(F.getContext(), CatchPadBB);
CatchSwitch->addHandler(CatchPadBB);
return CatchSwitch;
};
// Look for all basic blocks which are within cleanups which are postdominated
// by unreachable.
for (auto &Funclets : FuncletBlocks) {
BasicBlock *FuncletPadBB = Funclets.first;
auto *CleanupPad = dyn_cast<CleanupPadInst>(FuncletPadBB->getFirstNonPHI());
// Skip over any non-cleanup funclets.
if (!CleanupPad)
continue;
// Skip over any cleanups have unwind targets, they do not need this.
if (any_of(CleanupPad->users(),
[](const User *U) { return isa<CleanupReturnInst>(U); }))
continue;
// Walk the blocks within the cleanup which end in 'unreachable'.
// We will replace the unreachable instruction with a cleanupret;
// this cleanupret will unwind to a catchswitch with a lone catch-all
// catchpad.
std::vector<BasicBlock *> &BlocksInFunclet = Funclets.second;
for (BasicBlock *BB : BlocksInFunclet) {
auto *UI = dyn_cast<UnreachableInst>(BB->getTerminator());
if (!UI)
continue;
// Remove the unreachable instruction.
UI->eraseFromParent();
// Add our new cleanupret.
auto *ParentPad = CleanupPad->getParentPad();
CatchSwitchInst *CatchSwitch = GetOrCreateCatchSwitch(ParentPad);
CleanupReturnInst::Create(CleanupPad, CatchSwitch->getParent(), BB);
}
}
// Update BlockColors and FuncletBlocks to maintain WinEHPrepare's
// invariants.
for (auto CatchSwitchKV : NewCatchSwitches) {
CatchSwitchInst *CatchSwitch = CatchSwitchKV.second;
BasicBlock *CatchSwitchBB = CatchSwitch->getParent();
assert(CatchSwitch->getNumSuccessors() == 1);
BasicBlock *CatchPadBB = CatchSwitch->getSuccessor(0);
assert(isa<CatchPadInst>(CatchPadBB->getFirstNonPHI()));
BlockColors.insert({CatchSwitchBB, ColorVector(CatchSwitchBB)});
FuncletBlocks[CatchSwitchBB] = {CatchSwitchBB};
BlockColors.insert({CatchPadBB, ColorVector(CatchPadBB)});
FuncletBlocks[CatchPadBB] = {CatchPadBB};
}
}
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!");
}
}
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);
if (!DisableCleanups) {
DEBUG(verifyFunction(F));
removeImplausibleInstructions(F);
DEBUG(verifyFunction(F));
cleanupPreparedFunclets(F);
}
fixupNoReturnCleanupPads(F);
DEBUG(verifyPreparedFunclets(F));
// Recolor the CFG to verify that all is well.
DEBUG(colorFunclets(F));
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 (!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);
}
WinEHFuncInfo::WinEHFuncInfo() {}
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