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llvm-project/llvm/lib/CodeGen/WinEHPrepare.cpp

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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/Analysis/CFG.h"
#include "llvm/Analysis/LibCallSemantics.h"
#include "llvm/CodeGen/WinEHFuncInfo.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
using namespace llvm;
#define DEBUG_TYPE "winehprepare"
static cl::opt<bool> DisableDemotion(
"disable-demotion", cl::Hidden,
cl::desc(
"Clone multicolor basic blocks but do not demote cross funclet values"),
cl::init(false));
static cl::opt<bool> DisableCleanups(
"disable-cleanups", cl::Hidden,
cl::desc("Do not remove implausible terminators or other similar cleanups"),
cl::init(false));
namespace {
class WinEHPrepare : public FunctionPass {
public:
static char ID; // Pass identification, replacement for typeid.
WinEHPrepare(const TargetMachine *TM = nullptr) : FunctionPass(ID) {}
bool runOnFunction(Function &Fn) override;
bool doFinalization(Module &M) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
const char *getPassName() const override {
return "Windows exception handling preparation";
}
private:
void insertPHIStores(PHINode *OriginalPHI, AllocaInst *SpillSlot);
void
insertPHIStore(BasicBlock *PredBlock, Value *PredVal, AllocaInst *SpillSlot,
SmallVectorImpl<std::pair<BasicBlock *, Value *>> &Worklist);
AllocaInst *insertPHILoads(PHINode *PN, Function &F);
void replaceUseWithLoad(Value *V, Use &U, AllocaInst *&SpillSlot,
DenseMap<BasicBlock *, Value *> &Loads, Function &F);
void demoteNonlocalUses(Value *V, std::set<BasicBlock *> &ColorsForBB,
Function &F);
bool prepareExplicitEH(Function &F,
SmallVectorImpl<BasicBlock *> &EntryBlocks);
void replaceTerminatePadWithCleanup(Function &F);
void colorFunclets(Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks);
void demotePHIsOnFunclets(Function &F);
void demoteUsesBetweenFunclets(Function &F);
void demoteArgumentUses(Function &F);
void cloneCommonBlocks(Function &F,
SmallVectorImpl<BasicBlock *> &EntryBlocks);
void removeImplausibleTerminators(Function &F);
void cleanupPreparedFunclets(Function &F);
void verifyPreparedFunclets(Function &F);
// All fields are reset by runOnFunction.
EHPersonality Personality = EHPersonality::Unknown;
std::map<BasicBlock *, std::set<BasicBlock *>> BlockColors;
std::map<BasicBlock *, std::set<BasicBlock *>> FuncletBlocks;
std::map<BasicBlock *, std::set<BasicBlock *>> FuncletChildren;
};
} // 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);
}
static void findFuncletEntryPoints(Function &Fn,
SmallVectorImpl<BasicBlock *> &EntryBlocks) {
EntryBlocks.push_back(&Fn.getEntryBlock());
for (BasicBlock &BB : Fn) {
Instruction *First = BB.getFirstNonPHI();
if (!First->isEHPad())
continue;
assert(!isa<LandingPadInst>(First) &&
"landingpad cannot be used with funclet EH personality");
// Find EH pad blocks that represent funclet start points.
if (!isa<CatchEndPadInst>(First) && !isa<CleanupEndPadInst>(First))
EntryBlocks.push_back(&BB);
}
}
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;
// 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(Fn);
SmallVector<BasicBlock *, 4> EntryBlocks;
findFuncletEntryPoints(Fn, EntryBlocks);
return prepareExplicitEH(Fn, EntryBlocks);
}
bool WinEHPrepare::doFinalization(Module &M) { return false; }
void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {}
static int addUnwindMapEntry(WinEHFuncInfo &FuncInfo, int ToState,
const BasicBlock *BB) {
CxxUnwindMapEntry UME;
UME.ToState = ToState;
UME.Cleanup = BB;
FuncInfo.CxxUnwindMap.push_back(UME);
return FuncInfo.getLastStateNumber();
}
static void addTryBlockMapEntry(WinEHFuncInfo &FuncInfo, int TryLow,
int TryHigh, int CatchHigh,
ArrayRef<const CatchPadInst *> Handlers) {
WinEHTryBlockMapEntry TBME;
TBME.TryLow = TryLow;
TBME.TryHigh = TryHigh;
TBME.CatchHigh = CatchHigh;
assert(TBME.TryLow <= TBME.TryHigh);
for (const CatchPadInst *CPI : Handlers) {
WinEHHandlerType HT;
Constant *TypeInfo = cast<Constant>(CPI->getArgOperand(0));
if (TypeInfo->isNullValue())
HT.TypeDescriptor = nullptr;
else
HT.TypeDescriptor = cast<GlobalVariable>(TypeInfo->stripPointerCasts());
HT.Adjectives = cast<ConstantInt>(CPI->getArgOperand(1))->getZExtValue();
HT.Handler = CPI->getParent();
if (isa<ConstantPointerNull>(CPI->getArgOperand(2)))
HT.CatchObj.Alloca = nullptr;
else
HT.CatchObj.Alloca = cast<AllocaInst>(CPI->getArgOperand(2));
TBME.HandlerArray.push_back(HT);
}
FuncInfo.TryBlockMap.push_back(TBME);
}
static const CatchPadInst *getSingleCatchPadPredecessor(const BasicBlock *BB) {
for (const BasicBlock *PredBlock : predecessors(BB))
if (auto *CPI = dyn_cast<CatchPadInst>(PredBlock->getFirstNonPHI()))
return CPI;
return nullptr;
}
/// Find all the catchpads that feed directly into the catchendpad. Frontends
/// using this personality should ensure that each catchendpad and catchpad has
/// one or zero catchpad predecessors.
///
/// The following C++ generates the IR after it:
/// try {
/// } catch (A) {
/// } catch (B) {
/// }
///
/// IR:
/// %catchpad.A
/// catchpad [i8* A typeinfo]
/// to label %catch.A unwind label %catchpad.B
/// %catchpad.B
/// catchpad [i8* B typeinfo]
/// to label %catch.B unwind label %endcatches
/// %endcatches
/// catchendblock unwind to caller
static void
findCatchPadsForCatchEndPad(const BasicBlock *CatchEndBB,
SmallVectorImpl<const CatchPadInst *> &Handlers) {
const CatchPadInst *CPI = getSingleCatchPadPredecessor(CatchEndBB);
while (CPI) {
Handlers.push_back(CPI);
CPI = getSingleCatchPadPredecessor(CPI->getParent());
}
// We've pushed these back into reverse source order. Reverse them to get
// the list back into source order.
std::reverse(Handlers.begin(), Handlers.end());
}
// 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) {
const TerminatorInst *TI = BB->getTerminator();
if (isa<InvokeInst>(TI))
return nullptr;
if (TI->isEHPad())
return BB;
return cast<CleanupReturnInst>(TI)->getCleanupPad()->getParent();
}
static void calculateExplicitCXXStateNumbers(WinEHFuncInfo &FuncInfo,
const BasicBlock &BB,
int ParentState) {
assert(BB.isEHPad());
const Instruction *FirstNonPHI = BB.getFirstNonPHI();
// All catchpad instructions will be handled when we process their
// respective catchendpad instruction.
if (isa<CatchPadInst>(FirstNonPHI))
return;
if (isa<CatchEndPadInst>(FirstNonPHI)) {
SmallVector<const CatchPadInst *, 2> Handlers;
findCatchPadsForCatchEndPad(&BB, Handlers);
const BasicBlock *FirstTryPad = Handlers.front()->getParent();
int TryLow = addUnwindMapEntry(FuncInfo, ParentState, nullptr);
FuncInfo.EHPadStateMap[Handlers.front()] = TryLow;
for (const BasicBlock *PredBlock : predecessors(FirstTryPad))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitCXXStateNumbers(FuncInfo, *PredBlock, TryLow);
int CatchLow = addUnwindMapEntry(FuncInfo, ParentState, nullptr);
// catchpads are separate funclets in C++ EH due to the way rethrow works.
// In SEH, they aren't, so no invokes will unwind to the catchendpad.
FuncInfo.EHPadStateMap[FirstNonPHI] = CatchLow;
int TryHigh = CatchLow - 1;
for (const BasicBlock *PredBlock : predecessors(&BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitCXXStateNumbers(FuncInfo, *PredBlock, CatchLow);
int CatchHigh = FuncInfo.getLastStateNumber();
addTryBlockMapEntry(FuncInfo, TryLow, TryHigh, CatchHigh, Handlers);
DEBUG(dbgs() << "TryLow[" << FirstTryPad->getName() << "]: " << TryLow
<< '\n');
DEBUG(dbgs() << "TryHigh[" << FirstTryPad->getName() << "]: " << TryHigh
<< '\n');
DEBUG(dbgs() << "CatchHigh[" << FirstTryPad->getName() << "]: " << CatchHigh
<< '\n');
} else if (isa<CleanupPadInst>(FirstNonPHI)) {
// A cleanup can have multiple exits; don't re-process after the first.
if (FuncInfo.EHPadStateMap.count(FirstNonPHI))
return;
int CleanupState = addUnwindMapEntry(FuncInfo, ParentState, &BB);
FuncInfo.EHPadStateMap[FirstNonPHI] = CleanupState;
DEBUG(dbgs() << "Assigning state #" << CleanupState << " to BB "
<< BB.getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(&BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitCXXStateNumbers(FuncInfo, *PredBlock, CleanupState);
} else if (auto *CEPI = dyn_cast<CleanupEndPadInst>(FirstNonPHI)) {
// Propagate ParentState to the cleanuppad in case it doesn't have
// any cleanuprets.
BasicBlock *CleanupBlock = CEPI->getCleanupPad()->getParent();
calculateExplicitCXXStateNumbers(FuncInfo, *CleanupBlock, ParentState);
// Anything unwinding through CleanupEndPadInst is in ParentState.
FuncInfo.EHPadStateMap[FirstNonPHI] = ParentState;
for (const BasicBlock *PredBlock : predecessors(&BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitCXXStateNumbers(FuncInfo, *PredBlock, ParentState);
} else if (isa<TerminatePadInst>(FirstNonPHI)) {
report_fatal_error("Not yet implemented!");
} else {
llvm_unreachable("unexpected EH Pad!");
}
}
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 calculateExplicitSEHStateNumbers(WinEHFuncInfo &FuncInfo,
const BasicBlock &BB,
int ParentState) {
assert(BB.isEHPad());
const Instruction *FirstNonPHI = BB.getFirstNonPHI();
// All catchpad instructions will be handled when we process their
// respective catchendpad instruction.
if (isa<CatchPadInst>(FirstNonPHI))
return;
if (isa<CatchEndPadInst>(FirstNonPHI)) {
// Extract the filter function and the __except basic block and create a
// state for them.
SmallVector<const CatchPadInst *, 1> Handlers;
findCatchPadsForCatchEndPad(&BB, Handlers);
assert(Handlers.size() == 1 &&
"SEH doesn't have multiple handlers per __try");
const CatchPadInst *CPI = Handlers.front();
const BasicBlock *CatchPadBB = CPI->getParent();
const Constant *FilterOrNull =
cast<Constant>(CPI->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[CPI] = TryState;
DEBUG(dbgs() << "Assigning state #" << TryState << " to BB "
<< CatchPadBB->getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(CatchPadBB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitSEHStateNumbers(FuncInfo, *PredBlock, TryState);
// Everything in the __except block unwinds to ParentState, just like code
// outside the __try.
FuncInfo.EHPadStateMap[FirstNonPHI] = ParentState;
DEBUG(dbgs() << "Assigning state #" << ParentState << " to BB "
<< BB.getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(&BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitSEHStateNumbers(FuncInfo, *PredBlock, ParentState);
} else if (isa<CleanupPadInst>(FirstNonPHI)) {
// A cleanup can have multiple exits; don't re-process after the first.
if (FuncInfo.EHPadStateMap.count(FirstNonPHI))
return;
int CleanupState = addSEHFinally(FuncInfo, ParentState, &BB);
FuncInfo.EHPadStateMap[FirstNonPHI] = CleanupState;
DEBUG(dbgs() << "Assigning state #" << CleanupState << " to BB "
<< BB.getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(&BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitSEHStateNumbers(FuncInfo, *PredBlock, CleanupState);
} else if (auto *CEPI = dyn_cast<CleanupEndPadInst>(FirstNonPHI)) {
// Propagate ParentState to the cleanuppad in case it doesn't have
// any cleanuprets.
BasicBlock *CleanupBlock = CEPI->getCleanupPad()->getParent();
calculateExplicitSEHStateNumbers(FuncInfo, *CleanupBlock, ParentState);
// Anything unwinding through CleanupEndPadInst is in ParentState.
FuncInfo.EHPadStateMap[FirstNonPHI] = ParentState;
DEBUG(dbgs() << "Assigning state #" << ParentState << " to BB "
<< BB.getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(&BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitSEHStateNumbers(FuncInfo, *PredBlock, ParentState);
} else if (isa<TerminatePadInst>(FirstNonPHI)) {
report_fatal_error("Not yet implemented!");
} else {
llvm_unreachable("unexpected EH Pad!");
}
}
/// Check if the EH Pad unwinds to caller. Cleanups are a little bit of a
/// special case because we have to look at the cleanupret instruction that uses
/// the cleanuppad.
static bool doesEHPadUnwindToCaller(const Instruction *EHPad) {
auto *CPI = dyn_cast<CleanupPadInst>(EHPad);
if (!CPI)
return EHPad->mayThrow();
// This cleanup does not return or unwind, so we say it unwinds to caller.
if (CPI->use_empty())
return true;
const Instruction *User = CPI->user_back();
if (auto *CRI = dyn_cast<CleanupReturnInst>(User))
return CRI->unwindsToCaller();
return cast<CleanupEndPadInst>(User)->unwindsToCaller();
}
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() || !doesEHPadUnwindToCaller(BB.getFirstNonPHI()))
continue;
calculateExplicitSEHStateNumbers(FuncInfo, BB, -1);
}
}
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;
if (BB.isLandingPad())
report_fatal_error("MSVC C++ EH cannot use landingpads");
const Instruction *FirstNonPHI = BB.getFirstNonPHI();
if (!doesEHPadUnwindToCaller(FirstNonPHI))
continue;
calculateExplicitCXXStateNumbers(FuncInfo, BB, -1);
}
}
static int addClrEHHandler(WinEHFuncInfo &FuncInfo, int ParentState,
ClrHandlerType HandlerType, uint32_t TypeToken,
const BasicBlock *Handler) {
ClrEHUnwindMapEntry Entry;
Entry.Parent = ParentState;
Entry.Handler = Handler;
Entry.HandlerType = HandlerType;
Entry.TypeToken = TypeToken;
FuncInfo.ClrEHUnwindMap.push_back(Entry);
return FuncInfo.ClrEHUnwindMap.size() - 1;
}
void llvm::calculateClrEHStateNumbers(const Function *Fn,
WinEHFuncInfo &FuncInfo) {
// Return if it's already been done.
if (!FuncInfo.EHPadStateMap.empty())
return;
SmallVector<std::pair<const Instruction *, int>, 8> Worklist;
// Each pad needs to be able to refer to its parent, so scan the function
// looking for top-level handlers and seed the worklist with them.
for (const BasicBlock &BB : *Fn) {
if (!BB.isEHPad())
continue;
if (BB.isLandingPad())
report_fatal_error("CoreCLR EH cannot use landingpads");
const Instruction *FirstNonPHI = BB.getFirstNonPHI();
if (!doesEHPadUnwindToCaller(FirstNonPHI))
continue;
// queue this with sentinel parent state -1 to mean unwind to caller.
Worklist.emplace_back(FirstNonPHI, -1);
}
while (!Worklist.empty()) {
const Instruction *Pad;
int ParentState;
std::tie(Pad, ParentState) = Worklist.pop_back_val();
int PredState;
if (const CleanupEndPadInst *EndPad = dyn_cast<CleanupEndPadInst>(Pad)) {
FuncInfo.EHPadStateMap[EndPad] = ParentState;
// Queue the cleanuppad, in case it doesn't have a cleanupret.
Worklist.emplace_back(EndPad->getCleanupPad(), ParentState);
// Preds of the endpad should get the parent state.
PredState = ParentState;
} else if (const CleanupPadInst *Cleanup = dyn_cast<CleanupPadInst>(Pad)) {
// A cleanup can have multiple exits; don't re-process after the first.
if (FuncInfo.EHPadStateMap.count(Pad))
continue;
// CoreCLR personality uses arity to distinguish faults from finallies.
const BasicBlock *PadBlock = Cleanup->getParent();
ClrHandlerType HandlerType =
(Cleanup->getNumOperands() ? ClrHandlerType::Fault
: ClrHandlerType::Finally);
int NewState =
addClrEHHandler(FuncInfo, ParentState, HandlerType, 0, PadBlock);
FuncInfo.EHPadStateMap[Cleanup] = NewState;
// Propagate the new state to all preds of the cleanup
PredState = NewState;
} else if (const CatchEndPadInst *EndPad = dyn_cast<CatchEndPadInst>(Pad)) {
FuncInfo.EHPadStateMap[EndPad] = ParentState;
// Preds of the endpad should get the parent state.
PredState = ParentState;
} else if (const CatchPadInst *Catch = dyn_cast<CatchPadInst>(Pad)) {
const BasicBlock *PadBlock = Catch->getParent();
uint32_t TypeToken = static_cast<uint32_t>(
cast<ConstantInt>(Catch->getArgOperand(0))->getZExtValue());
int NewState = addClrEHHandler(FuncInfo, ParentState,
ClrHandlerType::Catch, TypeToken, PadBlock);
FuncInfo.EHPadStateMap[Catch] = NewState;
// Preds of the catch get its state
PredState = NewState;
} else {
llvm_unreachable("Unexpected EH pad");
}
// Queue all predecessors with the given state
for (const BasicBlock *Pred : predecessors(Pad->getParent())) {
if ((Pred = getEHPadFromPredecessor(Pred)))
Worklist.emplace_back(Pred->getFirstNonPHI(), PredState);
}
}
}
void WinEHPrepare::replaceTerminatePadWithCleanup(Function &F) {
if (Personality != EHPersonality::MSVC_CXX)
return;
for (BasicBlock &BB : F) {
Instruction *First = BB.getFirstNonPHI();
auto *TPI = dyn_cast<TerminatePadInst>(First);
if (!TPI)
continue;
if (TPI->getNumArgOperands() != 1)
report_fatal_error(
"Expected a unary terminatepad for MSVC C++ personalities!");
auto *TerminateFn = dyn_cast<Function>(TPI->getArgOperand(0));
if (!TerminateFn)
report_fatal_error("Function operand expected in terminatepad for MSVC "
"C++ personalities!");
// Insert the cleanuppad instruction.
auto *CPI = CleanupPadInst::Create(
BB.getContext(), {}, Twine("terminatepad.for.", BB.getName()), &BB);
// Insert the call to the terminate instruction.
auto *CallTerminate = CallInst::Create(TerminateFn, {}, &BB);
CallTerminate->setDoesNotThrow();
CallTerminate->setDoesNotReturn();
CallTerminate->setCallingConv(TerminateFn->getCallingConv());
// Insert a new terminator for the cleanuppad using the same successor as
// the terminatepad.
CleanupReturnInst::Create(CPI, TPI->getUnwindDest(), &BB);
// Let's remove the terminatepad now that we've inserted the new
// instructions.
TPI->eraseFromParent();
}
}
static void
colorFunclets(Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks,
std::map<BasicBlock *, std::set<BasicBlock *>> &BlockColors,
std::map<BasicBlock *, std::set<BasicBlock *>> &FuncletBlocks,
std::map<BasicBlock *, std::set<BasicBlock *>> &FuncletChildren) {
SmallVector<std::pair<BasicBlock *, BasicBlock *>, 16> Worklist;
BasicBlock *EntryBlock = &F.getEntryBlock();
// Build up the color map, which maps each block to its set of 'colors'.
// For any block B, the "colors" of B are the set of funclets F (possibly
// including a root "funclet" representing the main function), such that
// F will need to directly contain B or a copy of B (where the term "directly
// contain" is used to distinguish from being "transitively contained" in
// a nested funclet).
// Use a CFG walk driven by a worklist of (block, color) pairs. The "color"
// sets attached during this processing to a block which is the entry of some
// funclet F is actually the set of F's parents -- i.e. the union of colors
// of all predecessors of F's entry. For all other blocks, the color sets
// are as defined above. A post-pass fixes up the block color map to reflect
// the same sense of "color" for funclet entries as for other blocks.
Worklist.push_back({EntryBlock, EntryBlock});
while (!Worklist.empty()) {
BasicBlock *Visiting;
BasicBlock *Color;
std::tie(Visiting, Color) = Worklist.pop_back_val();
Instruction *VisitingHead = Visiting->getFirstNonPHI();
if (VisitingHead->isEHPad() && !isa<CatchEndPadInst>(VisitingHead) &&
!isa<CleanupEndPadInst>(VisitingHead)) {
// Mark this as a funclet head as a member of itself.
FuncletBlocks[Visiting].insert(Visiting);
// Queue exits (i.e. successors of rets/endpads) with the parent color.
// Skip any exits that are catchendpads, since the parent color must then
// represent one of the catches chained to that catchendpad, but the
// catchendpad should get the color of the common parent of all its
// chained catches (i.e. the grandparent color of the current pad).
// We don't need to worry abou catchendpads going unvisited, since the
// catches chained to them must have unwind edges to them by which we will
// visit them.
for (User *U : VisitingHead->users()) {
if (auto *Exit = dyn_cast<TerminatorInst>(U)) {
for (BasicBlock *Succ : successors(Exit->getParent()))
if (!isa<CatchEndPadInst>(*Succ->getFirstNonPHI()))
if (BlockColors[Succ].insert(Color).second)
Worklist.push_back({Succ, Color});
}
}
// Handle CatchPad specially since its successors need different colors.
if (CatchPadInst *CatchPad = dyn_cast<CatchPadInst>(VisitingHead)) {
// Visit the normal successor with the color of the new EH pad, and
// visit the unwind successor with the color of the parent.
BasicBlock *NormalSucc = CatchPad->getNormalDest();
if (BlockColors[NormalSucc].insert(Visiting).second) {
Worklist.push_back({NormalSucc, Visiting});
}
BasicBlock *UnwindSucc = CatchPad->getUnwindDest();
if (BlockColors[UnwindSucc].insert(Color).second) {
Worklist.push_back({UnwindSucc, Color});
}
continue;
}
// Switch color to the current node, except for terminate pads which
// have no bodies and only unwind successors and so need their successors
// visited with the color of the parent.
if (!isa<TerminatePadInst>(VisitingHead))
Color = Visiting;
} else {
// Note that this is a member of the given color.
FuncletBlocks[Color].insert(Visiting);
}
TerminatorInst *Terminator = Visiting->getTerminator();
if (isa<CleanupReturnInst>(Terminator) ||
isa<CatchReturnInst>(Terminator) ||
isa<CleanupEndPadInst>(Terminator)) {
// These blocks' successors have already been queued with the parent
// color.
continue;
}
for (BasicBlock *Succ : successors(Visiting)) {
if (isa<CatchEndPadInst>(Succ->getFirstNonPHI())) {
// The catchendpad needs to be visited with the parent's color, not
// the current color. This will happen in the code above that visits
// any catchpad unwind successor with the parent color, so we can
// safely skip this successor here.
continue;
}
if (BlockColors[Succ].insert(Color).second) {
Worklist.push_back({Succ, Color});
}
}
}
// The processing above actually accumulated the parent set for this
// funclet into the color set for its entry; use the parent set to
// populate the children map, and reset the color set to include just
// the funclet itself (no instruction can target a funclet entry except on
// that transitions to the child funclet).
for (BasicBlock *FuncletEntry : EntryBlocks) {
std::set<BasicBlock *> &ColorMapItem = BlockColors[FuncletEntry];
for (BasicBlock *Parent : ColorMapItem)
FuncletChildren[Parent].insert(FuncletEntry);
ColorMapItem.clear();
ColorMapItem.insert(FuncletEntry);
}
}
void WinEHPrepare::colorFunclets(Function &F,
SmallVectorImpl<BasicBlock *> &EntryBlocks) {
::colorFunclets(F, EntryBlocks, BlockColors, FuncletBlocks, FuncletChildren);
}
void llvm::calculateCatchReturnSuccessorColors(const Function *Fn,
WinEHFuncInfo &FuncInfo) {
SmallVector<BasicBlock *, 4> EntryBlocks;
// colorFunclets needs the set of EntryBlocks, get them using
// findFuncletEntryPoints.
findFuncletEntryPoints(const_cast<Function &>(*Fn), EntryBlocks);
std::map<BasicBlock *, std::set<BasicBlock *>> BlockColors;
std::map<BasicBlock *, std::set<BasicBlock *>> FuncletBlocks;
std::map<BasicBlock *, std::set<BasicBlock *>> FuncletChildren;
// Figure out which basic blocks belong to which funclets.
colorFunclets(const_cast<Function &>(*Fn), EntryBlocks, BlockColors,
FuncletBlocks, FuncletChildren);
// We need to find the catchret successors. To do this, we must first find
// all the catchpad funclets.
for (auto &Funclet : FuncletBlocks) {
// Figure out what kind of funclet we are looking at; We only care about
// catchpads.
BasicBlock *FuncletPadBB = Funclet.first;
Instruction *FirstNonPHI = FuncletPadBB->getFirstNonPHI();
auto *CatchPad = dyn_cast<CatchPadInst>(FirstNonPHI);
if (!CatchPad)
continue;
// The users of a catchpad are always catchrets.
for (User *Exit : CatchPad->users()) {
auto *CatchReturn = dyn_cast<CatchReturnInst>(Exit);
if (!CatchReturn)
continue;
BasicBlock *CatchRetSuccessor = CatchReturn->getSuccessor();
std::set<BasicBlock *> &SuccessorColors = BlockColors[CatchRetSuccessor];
assert(SuccessorColors.size() == 1 && "Expected BB to be monochrome!");
BasicBlock *Color = *SuccessorColors.begin();
// Record the catchret successor's funclet membership.
FuncInfo.CatchRetSuccessorColorMap[CatchReturn] = Color;
}
}
}
void WinEHPrepare::demotePHIsOnFunclets(Function &F) {
// Strip PHI nodes off of EH pads.
SmallVector<PHINode *, 16> PHINodes;
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) {
BasicBlock *BB = &*FI++;
if (!BB->isEHPad())
continue;
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
Instruction *I = &*BI++;
auto *PN = dyn_cast<PHINode>(I);
// Stop at the first non-PHI.
if (!PN)
break;
AllocaInst *SpillSlot = insertPHILoads(PN, F);
if (SpillSlot)
insertPHIStores(PN, SpillSlot);
PHINodes.push_back(PN);
}
}
for (auto *PN : PHINodes) {
// There may be lingering uses on other EH PHIs being removed
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
PN->eraseFromParent();
}
}
void WinEHPrepare::demoteUsesBetweenFunclets(Function &F) {
// Turn all inter-funclet uses of a Value into loads and stores.
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) {
BasicBlock *BB = &*FI++;
std::set<BasicBlock *> &ColorsForBB = BlockColors[BB];
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
Instruction *I = &*BI++;
// Funclets are permitted to use static allocas.
if (auto *AI = dyn_cast<AllocaInst>(I))
if (AI->isStaticAlloca())
continue;
demoteNonlocalUses(I, ColorsForBB, F);
}
}
}
void WinEHPrepare::demoteArgumentUses(Function &F) {
// Also demote function parameters used in funclets.
std::set<BasicBlock *> &ColorsForEntry = BlockColors[&F.getEntryBlock()];
for (Argument &Arg : F.args())
demoteNonlocalUses(&Arg, ColorsForEntry, F);
}
void WinEHPrepare::cloneCommonBlocks(
Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks) {
// 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 (BasicBlock *FuncletPadBB : EntryBlocks) {
std::set<BasicBlock *> &BlocksInFunclet = FuncletBlocks[FuncletPadBB];
std::map<BasicBlock *, BasicBlock *> Orig2Clone;
ValueToValueMapTy VMap;
for (BasicBlock *BB : BlocksInFunclet) {
std::set<BasicBlock *> &ColorsForBB = BlockColors[BB];
// We don't need to do anything if the block is monochromatic.
size_t NumColorsForBB = ColorsForBB.size();
if (NumColorsForBB == 1)
continue;
// 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[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.insert(NewBlock);
BlockColors[NewBlock].insert(FuncletPadBB);
BlocksInFunclet.erase(OldBlock);
BlockColors[OldBlock].erase(FuncletPadBB);
}
// 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);
// 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();
std::set<BasicBlock *> &ColorsForUserBB = BlockColors[UserBB];
assert(!ColorsForUserBB.empty());
if (ColorsForUserBB.size() > 1 ||
*ColorsForUserBB.begin() != FuncletPadBB)
UsesToRename.push_back(&U);
}
// If there are no uses outside the block, we're done with this
// instruction.
if (UsesToRename.empty())
continue;
// We found a use of OldI outside of the funclet. Rename all uses of OldI
// that are outside its funclet to be uses of the appropriate PHI node
// etc.
SSAUpdater SSAUpdate;
SSAUpdate.Initialize(OldI->getType(), OldI->getName());
SSAUpdate.AddAvailableValue(OldI->getParent(), OldI);
SSAUpdate.AddAvailableValue(NewI->getParent(), NewI);
while (!UsesToRename.empty())
SSAUpdate.RewriteUseAfterInsertions(*UsesToRename.pop_back_val());
}
}
}
void WinEHPrepare::removeImplausibleTerminators(Function &F) {
// Remove implausible terminators and replace them with UnreachableInst.
for (auto &Funclet : FuncletBlocks) {
BasicBlock *FuncletPadBB = Funclet.first;
std::set<BasicBlock *> &BlocksInFunclet = Funclet.second;
Instruction *FirstNonPHI = FuncletPadBB->getFirstNonPHI();
auto *CatchPad = dyn_cast<CatchPadInst>(FirstNonPHI);
auto *CleanupPad = dyn_cast<CleanupPadInst>(FirstNonPHI);
for (BasicBlock *BB : BlocksInFunclet) {
TerminatorInst *TI = BB->getTerminator();
// CatchPadInst and CleanupPadInst can't transfer control to a ReturnInst.
bool IsUnreachableRet = isa<ReturnInst>(TI) && (CatchPad || CleanupPad);
// The token consumed by a CatchReturnInst must match the funclet token.
bool IsUnreachableCatchret = false;
if (auto *CRI = dyn_cast<CatchReturnInst>(TI))
IsUnreachableCatchret = CRI->getCatchPad() != CatchPad;
// The token consumed by a CleanupReturnInst must match the funclet token.
bool IsUnreachableCleanupret = false;
if (auto *CRI = dyn_cast<CleanupReturnInst>(TI))
IsUnreachableCleanupret = CRI->getCleanupPad() != CleanupPad;
// The token consumed by a CleanupEndPadInst must match the funclet token.
bool IsUnreachableCleanupendpad = false;
if (auto *CEPI = dyn_cast<CleanupEndPadInst>(TI))
IsUnreachableCleanupendpad = CEPI->getCleanupPad() != CleanupPad;
if (IsUnreachableRet || IsUnreachableCatchret ||
IsUnreachableCleanupret || IsUnreachableCleanupendpad) {
// Loop through all of our successors and make sure they know that one
// of their predecessors is going away.
for (BasicBlock *SuccBB : TI->successors())
SuccBB->removePredecessor(BB);
if (IsUnreachableCleanupendpad) {
// We can't simply replace a cleanupendpad with unreachable, because
// its predecessor edges are EH edges and unreachable is not an EH
// pad. Change all predecessors to the "unwind to caller" form.
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
PI != PE;) {
BasicBlock *Pred = *PI++;
removeUnwindEdge(Pred);
}
}
new UnreachableInst(BB->getContext(), TI);
TI->eraseFromParent();
}
// FIXME: Check for invokes/cleanuprets/cleanupendpads which unwind to
// implausible catchendpads (i.e. catchendpad not in immediate parent
// funclet).
}
}
}
void WinEHPrepare::cleanupPreparedFunclets(Function &F) {
// Clean-up some of the mess we made by removing useles PHI nodes, trivial
// branches, etc.
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) {
BasicBlock *BB = &*FI++;
SimplifyInstructionsInBlock(BB);
ConstantFoldTerminator(BB, /*DeleteDeadConditions=*/true);
MergeBlockIntoPredecessor(BB);
}
// We might have some unreachable blocks after cleaning up some impossible
// control flow.
removeUnreachableBlocks(F);
}
void WinEHPrepare::verifyPreparedFunclets(Function &F) {
// Recolor the CFG to verify that all is well.
for (BasicBlock &BB : F) {
size_t NumColors = BlockColors[&BB].size();
assert(NumColors == 1 && "Expected monochromatic BB!");
if (NumColors == 0)
report_fatal_error("Uncolored BB!");
if (NumColors > 1)
report_fatal_error("Multicolor BB!");
if (!DisableDemotion) {
bool EHPadHasPHI = BB.isEHPad() && isa<PHINode>(BB.begin());
assert(!EHPadHasPHI && "EH Pad still has a PHI!");
if (EHPadHasPHI)
report_fatal_error("EH Pad still has a PHI!");
}
}
}
bool WinEHPrepare::prepareExplicitEH(
Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks) {
replaceTerminatePadWithCleanup(F);
// Determine which blocks are reachable from which funclet entries.
colorFunclets(F, EntryBlocks);
if (!DisableDemotion) {
demotePHIsOnFunclets(F);
demoteUsesBetweenFunclets(F);
demoteArgumentUses(F);
}
cloneCommonBlocks(F, EntryBlocks);
if (!DisableCleanups) {
removeImplausibleTerminators(F);
cleanupPreparedFunclets(F);
}
verifyPreparedFunclets(F);
BlockColors.clear();
FuncletBlocks.clear();
FuncletChildren.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;
if (isa<CleanupPadInst>(PHIBlock->getFirstNonPHI())) {
// Insert a load in place of the PHI and replace 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;
}
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());
BasicBlock *UsingBB = UsingInst->getParent();
if (UsingBB->isEHPad()) {
// Use is on an EH pad phi. Leave it alone; we'll insert loads and
// stores for it separately.
assert(isa<PHINode>(UsingInst));
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<CleanupPadInst>(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());
}
// TODO: Share loads for same-funclet uses (requires dominators if funclets
// aren't properly nested).
void WinEHPrepare::demoteNonlocalUses(Value *V,
std::set<BasicBlock *> &ColorsForBB,
Function &F) {
// Tokens can only be used non-locally due to control flow involving
// unreachable edges. Don't try to demote the token usage, we'll simply
// delete the cloned user later.
if (isa<CatchPadInst>(V) || isa<CleanupPadInst>(V))
return;
DenseMap<BasicBlock *, Value *> Loads;
AllocaInst *SpillSlot = nullptr;
for (Value::use_iterator UI = V->use_begin(), UE = V->use_end(); UI != UE;) {
Use &U = *UI++;
auto *UsingInst = cast<Instruction>(U.getUser());
BasicBlock *UsingBB = UsingInst->getParent();
// Is the Use inside a block which is colored the same as the Def?
// If so, we don't need to escape the Def because we will clone
// ourselves our own private copy.
std::set<BasicBlock *> &ColorsForUsingBB = BlockColors[UsingBB];
if (ColorsForUsingBB == ColorsForBB)
continue;
replaceUseWithLoad(V, U, SpillSlot, Loads, F);
}
if (SpillSlot) {
// Insert stores of the computed value into the stack slot.
// We have to be careful if I is an invoke instruction,
// because we can't insert the store AFTER the terminator instruction.
BasicBlock::iterator InsertPt;
if (isa<Argument>(V)) {
InsertPt = F.getEntryBlock().getTerminator()->getIterator();
} else if (isa<TerminatorInst>(V)) {
auto *II = cast<InvokeInst>(V);
// We cannot demote invoke instructions to the stack if their normal
// edge is critical. Therefore, split the critical edge and create a
// basic block into which the store can be inserted.
if (!II->getNormalDest()->getSinglePredecessor()) {
unsigned SuccNum =
GetSuccessorNumber(II->getParent(), II->getNormalDest());
assert(isCriticalEdge(II, SuccNum) && "Expected a critical edge!");
BasicBlock *NewBlock = SplitCriticalEdge(II, SuccNum);
assert(NewBlock && "Unable to split critical edge.");
// Update the color mapping for the newly split edge.
std::set<BasicBlock *> &ColorsForUsingBB = BlockColors[II->getParent()];
BlockColors[NewBlock] = ColorsForUsingBB;
for (BasicBlock *FuncletPad : ColorsForUsingBB)
FuncletBlocks[FuncletPad].insert(NewBlock);
}
InsertPt = II->getNormalDest()->getFirstInsertionPt();
} else {
InsertPt = cast<Instruction>(V)->getIterator();
++InsertPt;
// Don't insert before PHI nodes or EH pad instrs.
for (; isa<PHINode>(InsertPt) || InsertPt->isEHPad(); ++InsertPt)
;
}
new StoreInst(V, SpillSlot, &*InsertPt);
}
}
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.
std::set<BasicBlock *> &ColorsForPHIBlock = BlockColors[PHIBlock];
BlockColors[NewBlock] = ColorsForPHIBlock;
for (BasicBlock *FuncletPad : ColorsForPHIBlock)
FuncletBlocks[FuncletPad].insert(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 BasicBlock *PadBB,
MCSymbol *InvokeBegin,
MCSymbol *InvokeEnd) {
assert(PadBB->isEHPad() && EHPadStateMap.count(PadBB->getFirstNonPHI()) &&
"should get EH pad BB with precomputed state");
InvokeToStateMap[InvokeBegin] =
std::make_pair(EHPadStateMap[PadBB->getFirstNonPHI()], InvokeEnd);
}
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