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llvm-6502/lib/CodeGen/WinEHPrepare.cpp
Reid Kleckner b2d414391a Make llvm.eh.actions an intrinsic and add docs for it 
These docs *don't* match the way WinEHPrepare uses them yet, and
verifier support isn't implemented either. The implementation will come
after the documentation text is reviewed and agreed upon.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232003 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-12 01:45:37 +00:00

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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. It snifs the personality function to see which kind of
// preparation is necessary. If the personality function uses the Itanium LSDA,
// this pass delegates to the DWARF EH preparation pass.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Passes.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Analysis/LibCallSemantics.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include <memory>
using namespace llvm;
using namespace llvm::PatternMatch;
#define DEBUG_TYPE "winehprepare"
namespace {
// This map is used to model frame variable usage during outlining, to
// construct a structure type to hold the frame variables in a frame
// allocation block, and to remap the frame variable allocas (including
// spill locations as needed) to GEPs that get the variable from the
// frame allocation structure.
typedef MapVector<Value *, TinyPtrVector<AllocaInst *>> FrameVarInfoMap;
typedef SmallSet<BasicBlock *, 4> VisitedBlockSet;
enum ActionType { Catch, Cleanup };
class LandingPadActions;
class ActionHandler;
class CatchHandler;
class CleanupHandler;
class LandingPadMap;
typedef DenseMap<const BasicBlock *, CatchHandler *> CatchHandlerMapTy;
typedef DenseMap<const BasicBlock *, CleanupHandler *> CleanupHandlerMapTy;
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:
bool prepareCPPEHHandlers(Function &F,
SmallVectorImpl<LandingPadInst *> &LPads);
bool outlineHandler(ActionHandler *Action, Function *SrcFn,
LandingPadInst *LPad, BasicBlock *StartBB,
FrameVarInfoMap &VarInfo);
void mapLandingPadBlocks(LandingPadInst *LPad, LandingPadActions &Actions);
CatchHandler *findCatchHandler(BasicBlock *BB, BasicBlock *&NextBB,
VisitedBlockSet &VisitedBlocks);
CleanupHandler *findCleanupHandler(BasicBlock *StartBB, BasicBlock *EndBB);
CatchHandlerMapTy CatchHandlerMap;
CleanupHandlerMapTy CleanupHandlerMap;
DenseMap<const LandingPadInst *, LandingPadMap> LPadMaps;
};
class WinEHFrameVariableMaterializer : public ValueMaterializer {
public:
WinEHFrameVariableMaterializer(Function *OutlinedFn,
FrameVarInfoMap &FrameVarInfo);
~WinEHFrameVariableMaterializer() {}
virtual Value *materializeValueFor(Value *V) override;
private:
FrameVarInfoMap &FrameVarInfo;
IRBuilder<> Builder;
};
class LandingPadMap {
public:
LandingPadMap() : OriginLPad(nullptr) {}
void mapLandingPad(const LandingPadInst *LPad);
bool isInitialized() { return OriginLPad != nullptr; }
bool mapIfEHPtrLoad(const LoadInst *Load) {
return mapIfEHLoad(Load, EHPtrStores, EHPtrStoreAddrs);
}
bool mapIfSelectorLoad(const LoadInst *Load) {
return mapIfEHLoad(Load, SelectorStores, SelectorStoreAddrs);
}
bool isLandingPadSpecificInst(const Instruction *Inst) const;
void remapSelector(ValueToValueMapTy &VMap, Value *MappedValue) const;
private:
bool mapIfEHLoad(const LoadInst *Load,
SmallVectorImpl<const StoreInst *> &Stores,
SmallVectorImpl<const Value *> &StoreAddrs);
const LandingPadInst *OriginLPad;
// We will normally only see one of each of these instructions, but
// if more than one occurs for some reason we can handle that.
TinyPtrVector<const ExtractValueInst *> ExtractedEHPtrs;
TinyPtrVector<const ExtractValueInst *> ExtractedSelectors;
// In optimized code, there will typically be at most one instance of
// each of the following, but in unoptimized IR it is not uncommon
// for the values to be stored, loaded and then stored again. In that
// case we will create a second entry for each store and store address.
SmallVector<const StoreInst *, 2> EHPtrStores;
SmallVector<const StoreInst *, 2> SelectorStores;
SmallVector<const Value *, 2> EHPtrStoreAddrs;
SmallVector<const Value *, 2> SelectorStoreAddrs;
};
class WinEHCloningDirectorBase : public CloningDirector {
public:
WinEHCloningDirectorBase(Function *HandlerFn,
FrameVarInfoMap &VarInfo,
LandingPadMap &LPadMap)
: Materializer(HandlerFn, VarInfo),
SelectorIDType(Type::getInt32Ty(HandlerFn->getContext())),
Int8PtrType(Type::getInt8PtrTy(HandlerFn->getContext())),
LPadMap(LPadMap) {}
CloningAction handleInstruction(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) override;
virtual CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) = 0;
virtual CloningAction handleEndCatch(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) = 0;
virtual CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) = 0;
virtual CloningAction handleInvoke(ValueToValueMapTy &VMap,
const InvokeInst *Invoke,
BasicBlock *NewBB) = 0;
virtual CloningAction handleResume(ValueToValueMapTy &VMap,
const ResumeInst *Resume,
BasicBlock *NewBB) = 0;
ValueMaterializer *getValueMaterializer() override { return &Materializer; }
protected:
WinEHFrameVariableMaterializer Materializer;
Type *SelectorIDType;
Type *Int8PtrType;
LandingPadMap &LPadMap;
};
class WinEHCatchDirector : public WinEHCloningDirectorBase {
public:
WinEHCatchDirector(Function *CatchFn, Value *Selector,
FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap)
: WinEHCloningDirectorBase(CatchFn, VarInfo, LPadMap),
CurrentSelector(Selector->stripPointerCasts()),
ExceptionObjectVar(nullptr) {}
CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) override;
CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
BasicBlock *NewBB) override;
CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) override;
CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
BasicBlock *NewBB) override;
CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
BasicBlock *NewBB) override;
const Value *getExceptionVar() { return ExceptionObjectVar; }
TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
private:
Value *CurrentSelector;
const Value *ExceptionObjectVar;
TinyPtrVector<BasicBlock *> ReturnTargets;
};
class WinEHCleanupDirector : public WinEHCloningDirectorBase {
public:
WinEHCleanupDirector(Function *CleanupFn,
FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap)
: WinEHCloningDirectorBase(CleanupFn, VarInfo, LPadMap) {}
CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) override;
CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
BasicBlock *NewBB) override;
CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) override;
CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
BasicBlock *NewBB) override;
CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
BasicBlock *NewBB) override;
};
class ActionHandler {
public:
ActionHandler(BasicBlock *BB, ActionType Type)
: StartBB(BB), Type(Type), OutlinedFn(nullptr) {}
ActionType getType() const { return Type; }
BasicBlock *getStartBlock() const { return StartBB; }
bool hasBeenOutlined() { return OutlinedFn != nullptr; }
void setOutlinedFunction(Function *F) { OutlinedFn = F; }
Function *getOutlinedFunction() { return OutlinedFn; }
private:
BasicBlock *StartBB;
ActionType Type;
Function *OutlinedFn;
};
class CatchHandler : public ActionHandler {
public:
CatchHandler(BasicBlock *BB, Constant *Selector, BasicBlock *NextBB)
: ActionHandler(BB, ActionType::Catch), Selector(Selector),
NextBB(NextBB), ExceptionObjectVar(nullptr) {}
// Method for support type inquiry through isa, cast, and dyn_cast:
static inline bool classof(const ActionHandler *H) {
return H->getType() == ActionType::Catch;
}
Constant *getSelector() const { return Selector; }
BasicBlock *getNextBB() const { return NextBB; }
const Value *getExceptionVar() { return ExceptionObjectVar; }
TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
void setExceptionVar(const Value *Val) { ExceptionObjectVar = Val; }
void setReturnTargets(TinyPtrVector<BasicBlock *> &Targets) {
ReturnTargets = Targets;
}
private:
Constant *Selector;
BasicBlock *NextBB;
const Value *ExceptionObjectVar;
TinyPtrVector<BasicBlock *> ReturnTargets;
};
class CleanupHandler : public ActionHandler {
public:
CleanupHandler(BasicBlock *BB) : ActionHandler(BB, ActionType::Cleanup) {}
// Method for support type inquiry through isa, cast, and dyn_cast:
static inline bool classof(const ActionHandler *H) {
return H->getType() == ActionType::Cleanup;
}
};
class LandingPadActions {
public:
LandingPadActions() : HasCleanupHandlers(false) {}
void insertCatchHandler(CatchHandler *Action) { Actions.push_back(Action); }
void insertCleanupHandler(CleanupHandler *Action) {
Actions.push_back(Action);
HasCleanupHandlers = true;
}
bool includesCleanup() const { return HasCleanupHandlers; }
SmallVectorImpl<ActionHandler *>::iterator begin() { return Actions.begin(); }
SmallVectorImpl<ActionHandler *>::iterator end() { return Actions.end(); }
private:
// Note that this class does not own the ActionHandler objects in this vector.
// The ActionHandlers are owned by the CatchHandlerMap and CleanupHandlerMap
// in the WinEHPrepare class.
SmallVector<ActionHandler *, 4> Actions;
bool HasCleanupHandlers;
};
} // 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) {
SmallVector<LandingPadInst *, 4> LPads;
SmallVector<ResumeInst *, 4> Resumes;
for (BasicBlock &BB : Fn) {
if (auto *LP = BB.getLandingPadInst())
LPads.push_back(LP);
if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
Resumes.push_back(Resume);
}
// No need to prepare functions that lack landing pads.
if (LPads.empty())
return false;
// Classify the personality to see what kind of preparation we need.
EHPersonality Pers = classifyEHPersonality(LPads.back()->getPersonalityFn());
// Do nothing if this is not an MSVC personality.
if (!isMSVCEHPersonality(Pers))
return false;
// FIXME: This only returns true if the C++ EH handlers were outlined.
// When that code is complete, it should always return whatever
// prepareCPPEHHandlers returns.
if (Pers == EHPersonality::MSVC_CXX && prepareCPPEHHandlers(Fn, LPads))
return true;
// FIXME: SEH Cleanups are unimplemented. Replace them with unreachable.
if (Resumes.empty())
return false;
for (ResumeInst *Resume : Resumes) {
IRBuilder<>(Resume).CreateUnreachable();
Resume->eraseFromParent();
}
return true;
}
bool WinEHPrepare::doFinalization(Module &M) {
return false;
}
void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {}
bool WinEHPrepare::prepareCPPEHHandlers(
Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
// These containers are used to re-map frame variables that are used in
// outlined catch and cleanup handlers. They will be populated as the
// handlers are outlined.
FrameVarInfoMap FrameVarInfo;
bool HandlersOutlined = false;
Module *M = F.getParent();
LLVMContext &Context = M->getContext();
// Create a new function to receive the handler contents.
PointerType *Int8PtrType = Type::getInt8PtrTy(Context);
Type *Int32Type = Type::getInt32Ty(Context);
Function *ActionIntrin = Intrinsic::getDeclaration(M, Intrinsic::eh_actions);
for (LandingPadInst *LPad : LPads) {
// Look for evidence that this landingpad has already been processed.
bool LPadHasActionList = false;
BasicBlock *LPadBB = LPad->getParent();
for (Instruction &Inst : LPadBB->getInstList()) {
// FIXME: Make this an intrinsic.
if (auto *IntrinCall = dyn_cast<IntrinsicInst>(&Inst)) {
if (IntrinCall->getIntrinsicID() == Intrinsic::eh_actions) {
LPadHasActionList = true;
break;
}
}
// FIXME: This is here to help with the development of nested landing pad
// outlining. It should be removed when that is finished.
if (isa<UnreachableInst>(Inst)) {
LPadHasActionList = true;
break;
}
}
// If we've already outlined the handlers for this landingpad,
// there's nothing more to do here.
if (LPadHasActionList)
continue;
LandingPadActions Actions;
mapLandingPadBlocks(LPad, Actions);
for (ActionHandler *Action : Actions) {
if (Action->hasBeenOutlined())
continue;
BasicBlock *StartBB = Action->getStartBlock();
if (outlineHandler(Action, &F, LPad, StartBB, FrameVarInfo)) {
HandlersOutlined = true;
}
} // End for each Action
// FIXME: We need a guard against partially outlined functions.
if (!HandlersOutlined)
continue;
// Replace the landing pad with a new llvm.eh.action based landing pad.
BasicBlock *NewLPadBB = BasicBlock::Create(Context, "lpad", &F, LPadBB);
assert(!isa<PHINode>(LPadBB->begin()));
Instruction *NewLPad = LPad->clone();
NewLPadBB->getInstList().push_back(NewLPad);
while (!pred_empty(LPadBB)) {
auto *pred = *pred_begin(LPadBB);
InvokeInst *Invoke = cast<InvokeInst>(pred->getTerminator());
Invoke->setUnwindDest(NewLPadBB);
}
// Add a call to describe the actions for this landing pad.
std::vector<Value *> ActionArgs;
ActionArgs.push_back(NewLPad);
for (ActionHandler *Action : Actions) {
if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
ActionArgs.push_back(ConstantInt::get(Int32Type, 0));
ActionArgs.push_back(CatchAction->getSelector());
Value *EHObj = const_cast<Value *>(CatchAction->getExceptionVar());
if (EHObj)
ActionArgs.push_back(EHObj);
else
ActionArgs.push_back(ConstantPointerNull::get(Int8PtrType));
} else {
ActionArgs.push_back(ConstantInt::get(Int32Type, 1));
}
Constant *HandlerPtr =
ConstantExpr::getBitCast(Action->getOutlinedFunction(), Int8PtrType);
ActionArgs.push_back(HandlerPtr);
}
CallInst *Recover =
CallInst::Create(ActionIntrin, ActionArgs, "recover", NewLPadBB);
// Add an indirect branch listing possible successors of the catch handlers.
IndirectBrInst *Branch = IndirectBrInst::Create(Recover, 0, NewLPadBB);
for (ActionHandler *Action : Actions) {
if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
for (auto *Target : CatchAction->getReturnTargets()) {
Branch->addDestination(Target);
}
}
}
} // End for each landingpad
// If nothing got outlined, there is no more processing to be done.
if (!HandlersOutlined)
return false;
// Delete any blocks that were only used by handlers that were outlined above.
removeUnreachableBlocks(F);
BasicBlock *Entry = &F.getEntryBlock();
IRBuilder<> Builder(F.getParent()->getContext());
Builder.SetInsertPoint(Entry->getFirstInsertionPt());
Function *FrameEscapeFn =
Intrinsic::getDeclaration(M, Intrinsic::frameescape);
Function *RecoverFrameFn =
Intrinsic::getDeclaration(M, Intrinsic::framerecover);
// Finally, replace all of the temporary allocas for frame variables used in
// the outlined handlers with calls to llvm.framerecover.
BasicBlock::iterator II = Entry->getFirstInsertionPt();
Instruction *AllocaInsertPt = II;
SmallVector<Value *, 8> AllocasToEscape;
for (auto &VarInfoEntry : FrameVarInfo) {
Value *ParentVal = VarInfoEntry.first;
TinyPtrVector<AllocaInst *> &Allocas = VarInfoEntry.second;
// If the mapped value isn't already an alloca, we need to spill it if it
// is a computed value or copy it if it is an argument.
AllocaInst *ParentAlloca = dyn_cast<AllocaInst>(ParentVal);
if (!ParentAlloca) {
if (auto *Arg = dyn_cast<Argument>(ParentVal)) {
// Lower this argument to a copy and then demote that to the stack.
// We can't just use the argument location because the handler needs
// it to be in the frame allocation block.
// Use 'select i8 true, %arg, undef' to simulate a 'no-op' instruction.
Value *TrueValue = ConstantInt::getTrue(Context);
Value *UndefValue = UndefValue::get(Arg->getType());
Instruction *SI =
SelectInst::Create(TrueValue, Arg, UndefValue,
Arg->getName() + ".tmp", AllocaInsertPt);
Arg->replaceAllUsesWith(SI);
// Reset the select operand, because it was clobbered by the RAUW above.
SI->setOperand(1, Arg);
ParentAlloca = DemoteRegToStack(*SI, true, SI);
} else if (auto *PN = dyn_cast<PHINode>(ParentVal)) {
ParentAlloca = DemotePHIToStack(PN, AllocaInsertPt);
} else {
Instruction *ParentInst = cast<Instruction>(ParentVal);
// FIXME: This is a work-around to temporarily handle the case where an
// instruction that is only used in handlers is not sunk.
// Without uses, DemoteRegToStack would just eliminate the value.
// This will fail if ParentInst is an invoke.
if (ParentInst->getNumUses() == 0) {
BasicBlock::iterator InsertPt = ParentInst;
++InsertPt;
ParentAlloca =
new AllocaInst(ParentInst->getType(), nullptr,
ParentInst->getName() + ".reg2mem", InsertPt);
new StoreInst(ParentInst, ParentAlloca, InsertPt);
} else {
ParentAlloca = DemoteRegToStack(*ParentInst, true, ParentInst);
}
}
}
// If the parent alloca is no longer used and only one of the handlers used
// it, erase the parent and leave the copy in the outlined handler.
if (ParentAlloca->getNumUses() == 0 && Allocas.size() == 1) {
ParentAlloca->eraseFromParent();
continue;
}
// Add this alloca to the list of things to escape.
AllocasToEscape.push_back(ParentAlloca);
// Next replace all outlined allocas that are mapped to it.
for (AllocaInst *TempAlloca : Allocas) {
Function *HandlerFn = TempAlloca->getParent()->getParent();
// FIXME: Sink this GEP into the blocks where it is used.
Builder.SetInsertPoint(TempAlloca);
Builder.SetCurrentDebugLocation(TempAlloca->getDebugLoc());
Value *RecoverArgs[] = {
Builder.CreateBitCast(&F, Int8PtrType, ""),
&(HandlerFn->getArgumentList().back()),
llvm::ConstantInt::get(Int32Type, AllocasToEscape.size() - 1)};
Value *RecoveredAlloca = Builder.CreateCall(RecoverFrameFn, RecoverArgs);
// Add a pointer bitcast if the alloca wasn't an i8.
if (RecoveredAlloca->getType() != TempAlloca->getType()) {
RecoveredAlloca->setName(Twine(TempAlloca->getName()) + ".i8");
RecoveredAlloca =
Builder.CreateBitCast(RecoveredAlloca, TempAlloca->getType());
}
TempAlloca->replaceAllUsesWith(RecoveredAlloca);
TempAlloca->removeFromParent();
RecoveredAlloca->takeName(TempAlloca);
delete TempAlloca;
}
} // End for each FrameVarInfo entry.
// Insert 'call void (...)* @llvm.frameescape(...)' at the end of the entry
// block.
Builder.SetInsertPoint(&F.getEntryBlock().back());
Builder.CreateCall(FrameEscapeFn, AllocasToEscape);
// Clean up the handler action maps we created for this function
DeleteContainerSeconds(CatchHandlerMap);
CatchHandlerMap.clear();
DeleteContainerSeconds(CleanupHandlerMap);
CleanupHandlerMap.clear();
return HandlersOutlined;
}
// This function examines a block to determine whether the block ends with a
// conditional branch to a catch handler based on a selector comparison.
// This function is used both by the WinEHPrepare::findSelectorComparison() and
// WinEHCleanupDirector::handleTypeIdFor().
static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
Constant *&Selector, BasicBlock *&NextBB) {
ICmpInst::Predicate Pred;
BasicBlock *TBB, *FBB;
Value *LHS, *RHS;
if (!match(BB->getTerminator(),
m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)), TBB, FBB)))
return false;
if (!match(LHS,
m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))) &&
!match(RHS, m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))))
return false;
if (Pred == CmpInst::ICMP_EQ) {
CatchHandler = TBB;
NextBB = FBB;
return true;
}
if (Pred == CmpInst::ICMP_NE) {
CatchHandler = FBB;
NextBB = TBB;
return true;
}
return false;
}
bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
LandingPadInst *LPad, BasicBlock *StartBB,
FrameVarInfoMap &VarInfo) {
Module *M = SrcFn->getParent();
LLVMContext &Context = M->getContext();
// Create a new function to receive the handler contents.
Type *Int8PtrType = Type::getInt8PtrTy(Context);
std::vector<Type *> ArgTys;
ArgTys.push_back(Int8PtrType);
ArgTys.push_back(Int8PtrType);
Function *Handler;
if (Action->getType() == Catch) {
FunctionType *FnType = FunctionType::get(Int8PtrType, ArgTys, false);
Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
SrcFn->getName() + ".catch", M);
} else {
FunctionType *FnType =
FunctionType::get(Type::getVoidTy(Context), ArgTys, false);
Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
SrcFn->getName() + ".cleanup", M);
}
// Generate a standard prolog to setup the frame recovery structure.
IRBuilder<> Builder(Context);
BasicBlock *Entry = BasicBlock::Create(Context, "entry");
Handler->getBasicBlockList().push_front(Entry);
Builder.SetInsertPoint(Entry);
Builder.SetCurrentDebugLocation(LPad->getDebugLoc());
std::unique_ptr<WinEHCloningDirectorBase> Director;
ValueToValueMapTy VMap;
LandingPadMap &LPadMap = LPadMaps[LPad];
if (!LPadMap.isInitialized())
LPadMap.mapLandingPad(LPad);
if (Action->getType() == Catch) {
Constant *SelectorType = cast<CatchHandler>(Action)->getSelector();
Director.reset(
new WinEHCatchDirector(Handler, SelectorType, VarInfo, LPadMap));
LPadMap.remapSelector(VMap, ConstantInt::get( Type::getInt32Ty(Context), 1));
} else {
Director.reset(new WinEHCleanupDirector(Handler, VarInfo, LPadMap));
}
SmallVector<ReturnInst *, 8> Returns;
ClonedCodeInfo OutlinedFunctionInfo;
// Skip over PHIs and, if applicable, landingpad instructions.
BasicBlock::iterator II = StartBB->getFirstInsertionPt();
CloneAndPruneIntoFromInst(Handler, SrcFn, II, VMap,
/*ModuleLevelChanges=*/false, Returns, "",
&OutlinedFunctionInfo, Director.get());
// Move all the instructions in the first cloned block into our entry block.
BasicBlock *FirstClonedBB = std::next(Function::iterator(Entry));
Entry->getInstList().splice(Entry->end(), FirstClonedBB->getInstList());
FirstClonedBB->eraseFromParent();
if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
WinEHCatchDirector *CatchDirector =
reinterpret_cast<WinEHCatchDirector *>(Director.get());
CatchAction->setExceptionVar(CatchDirector->getExceptionVar());
CatchAction->setReturnTargets(CatchDirector->getReturnTargets());
}
Action->setOutlinedFunction(Handler);
return true;
}
void LandingPadMap::mapLandingPad(const LandingPadInst *LPad) {
// Each instance of this class should only ever be used to map a single
// landing pad.
assert(OriginLPad == nullptr || OriginLPad == LPad);
// If the landing pad has already been mapped, there's nothing more to do.
if (OriginLPad == LPad)
return;
OriginLPad = LPad;
// The landingpad instruction returns an aggregate value. Typically, its
// value will be passed to a pair of extract value instructions and the
// results of those extracts are often passed to store instructions.
// In unoptimized code the stored value will often be loaded and then stored
// again.
for (auto *U : LPad->users()) {
const ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
if (!Extract)
continue;
assert(Extract->getNumIndices() == 1 &&
"Unexpected operation: extracting both landing pad values");
unsigned int Idx = *(Extract->idx_begin());
assert((Idx == 0 || Idx == 1) &&
"Unexpected operation: extracting an unknown landing pad element");
if (Idx == 0) {
// Element 0 doesn't directly corresponds to anything in the WinEH
// scheme.
// It will be stored to a memory location, then later loaded and finally
// the loaded value will be used as the argument to an
// llvm.eh.begincatch
// call. We're tracking it here so that we can skip the store and load.
ExtractedEHPtrs.push_back(Extract);
} else if (Idx == 1) {
// Element 1 corresponds to the filter selector. We'll map it to 1 for
// matching purposes, but it will also probably be stored to memory and
// reloaded, so we need to track the instuction so that we can map the
// loaded value too.
ExtractedSelectors.push_back(Extract);
}
// Look for stores of the extracted values.
for (auto *EU : Extract->users()) {
if (auto *Store = dyn_cast<StoreInst>(EU)) {
if (Idx == 1) {
SelectorStores.push_back(Store);
SelectorStoreAddrs.push_back(Store->getPointerOperand());
} else {
EHPtrStores.push_back(Store);
EHPtrStoreAddrs.push_back(Store->getPointerOperand());
}
}
}
}
}
bool LandingPadMap::isLandingPadSpecificInst(const Instruction *Inst) const {
if (Inst == OriginLPad)
return true;
for (auto *Extract : ExtractedEHPtrs) {
if (Inst == Extract)
return true;
}
for (auto *Extract : ExtractedSelectors) {
if (Inst == Extract)
return true;
}
for (auto *Store : EHPtrStores) {
if (Inst == Store)
return true;
}
for (auto *Store : SelectorStores) {
if (Inst == Store)
return true;
}
return false;
}
void LandingPadMap::remapSelector(ValueToValueMapTy &VMap,
Value *MappedValue) const {
// Remap all selector extract instructions to the specified value.
for (auto *Extract : ExtractedSelectors)
VMap[Extract] = MappedValue;
}
bool LandingPadMap::mapIfEHLoad(const LoadInst *Load,
SmallVectorImpl<const StoreInst *> &Stores,
SmallVectorImpl<const Value *> &StoreAddrs) {
// This makes the assumption that a store we've previously seen dominates
// this load instruction. That might seem like a rather huge assumption,
// but given the way that landingpads are constructed its fairly safe.
// FIXME: Add debug/assert code that verifies this.
const Value *LoadAddr = Load->getPointerOperand();
for (auto *StoreAddr : StoreAddrs) {
if (LoadAddr == StoreAddr) {
// Handle the common debug scenario where this loaded value is stored
// to a different location.
for (auto *U : Load->users()) {
if (auto *Store = dyn_cast<StoreInst>(U)) {
Stores.push_back(Store);
StoreAddrs.push_back(Store->getPointerOperand());
}
}
return true;
}
}
return false;
}
CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
// If this is one of the boilerplate landing pad instructions, skip it.
// The instruction will have already been remapped in VMap.
if (LPadMap.isLandingPadSpecificInst(Inst))
return CloningDirector::SkipInstruction;
if (auto *Load = dyn_cast<LoadInst>(Inst)) {
// Look for loads of (previously suppressed) landingpad values.
// The EHPtr load can be mapped to an undef value as it should only be used
// as an argument to llvm.eh.begincatch, but the selector value needs to be
// mapped to a constant value of 1. This value will be used to simplify the
// branching to always flow to the current handler.
if (LPadMap.mapIfSelectorLoad(Load)) {
VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
return CloningDirector::SkipInstruction;
}
if (LPadMap.mapIfEHPtrLoad(Load)) {
VMap[Inst] = UndefValue::get(Int8PtrType);
return CloningDirector::SkipInstruction;
}
// Any other loads just get cloned.
return CloningDirector::CloneInstruction;
}
// Nested landing pads will be cloned as stubs, with just the
// landingpad instruction and an unreachable instruction. When
// all landingpads have been outlined, we'll replace this with the
// llvm.eh.actions call and indirect branch created when the
// landing pad was outlined.
if (auto *NestedLPad = dyn_cast<LandingPadInst>(Inst)) {
Instruction *NewInst = NestedLPad->clone();
if (NestedLPad->hasName())
NewInst->setName(NestedLPad->getName());
// FIXME: Store this mapping somewhere else also.
VMap[NestedLPad] = NewInst;
BasicBlock::InstListType &InstList = NewBB->getInstList();
InstList.push_back(NewInst);
InstList.push_back(new UnreachableInst(NewBB->getContext()));
return CloningDirector::StopCloningBB;
}
if (auto *Invoke = dyn_cast<InvokeInst>(Inst))
return handleInvoke(VMap, Invoke, NewBB);
if (auto *Resume = dyn_cast<ResumeInst>(Inst))
return handleResume(VMap, Resume, NewBB);
if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
return handleBeginCatch(VMap, Inst, NewBB);
if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
return handleEndCatch(VMap, Inst, NewBB);
if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
return handleTypeIdFor(VMap, Inst, NewBB);
// Continue with the default cloning behavior.
return CloningDirector::CloneInstruction;
}
CloningDirector::CloningAction WinEHCatchDirector::handleBeginCatch(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
// The argument to the call is some form of the first element of the
// landingpad aggregate value, but that doesn't matter. It isn't used
// here.
// The second argument is an outparameter where the exception object will be
// stored. Typically the exception object is a scalar, but it can be an
// aggregate when catching by value.
// FIXME: Leave something behind to indicate where the exception object lives
// for this handler. Should it be part of llvm.eh.actions?
assert(ExceptionObjectVar == nullptr && "Multiple calls to "
"llvm.eh.begincatch found while "
"outlining catch handler.");
ExceptionObjectVar = Inst->getOperand(1)->stripPointerCasts();
return CloningDirector::SkipInstruction;
}
CloningDirector::CloningAction
WinEHCatchDirector::handleEndCatch(ValueToValueMapTy &VMap,
const Instruction *Inst, BasicBlock *NewBB) {
auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
// It might be interesting to track whether or not we are inside a catch
// function, but that might make the algorithm more brittle than it needs
// to be.
// The end catch call can occur in one of two places: either in a
// landingpad block that is part of the catch handlers exception mechanism,
// or at the end of the catch block. If it occurs in a landing pad, we must
// skip it and continue so that the landing pad gets cloned.
// FIXME: This case isn't fully supported yet and shouldn't turn up in any
// of the test cases until it is.
if (IntrinCall->getParent()->isLandingPad())
return CloningDirector::SkipInstruction;
// If an end catch occurs anywhere else the next instruction should be an
// unconditional branch instruction that we want to replace with a return
// to the the address of the branch target.
const BasicBlock *EndCatchBB = IntrinCall->getParent();
const TerminatorInst *Terminator = EndCatchBB->getTerminator();
const BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
assert(Branch && Branch->isUnconditional());
assert(std::next(BasicBlock::const_iterator(IntrinCall)) ==
BasicBlock::const_iterator(Branch));
BasicBlock *ContinueLabel = Branch->getSuccessor(0);
ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueLabel),
NewBB);
ReturnTargets.push_back(ContinueLabel);
// We just added a terminator to the cloned block.
// Tell the caller to stop processing the current basic block so that
// the branch instruction will be skipped.
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction WinEHCatchDirector::handleTypeIdFor(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
// This causes a replacement that will collapse the landing pad CFG based
// on the filter function we intend to match.
if (Selector == CurrentSelector)
VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
else
VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
// Tell the caller not to clone this instruction.
return CloningDirector::SkipInstruction;
}
CloningDirector::CloningAction
WinEHCatchDirector::handleInvoke(ValueToValueMapTy &VMap,
const InvokeInst *Invoke, BasicBlock *NewBB) {
return CloningDirector::CloneInstruction;
}
CloningDirector::CloningAction
WinEHCatchDirector::handleResume(ValueToValueMapTy &VMap,
const ResumeInst *Resume, BasicBlock *NewBB) {
// Resume instructions shouldn't be reachable from catch handlers.
// We still need to handle it, but it will be pruned.
BasicBlock::InstListType &InstList = NewBB->getInstList();
InstList.push_back(new UnreachableInst(NewBB->getContext()));
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleBeginCatch(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
// Catch blocks within cleanup handlers will always be unreachable.
// We'll insert an unreachable instruction now, but it will be pruned
// before the cloning process is complete.
BasicBlock::InstListType &InstList = NewBB->getInstList();
InstList.push_back(new UnreachableInst(NewBB->getContext()));
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleEndCatch(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
// Catch blocks within cleanup handlers will always be unreachable.
// We'll insert an unreachable instruction now, but it will be pruned
// before the cloning process is complete.
BasicBlock::InstListType &InstList = NewBB->getInstList();
InstList.push_back(new UnreachableInst(NewBB->getContext()));
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleTypeIdFor(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
// If we encounter a selector comparison while cloning a cleanup handler,
// we want to stop cloning immediately. Anything after the dispatch
// will be outlined into a different handler.
BasicBlock *CatchHandler;
Constant *Selector;
BasicBlock *NextBB;
if (isSelectorDispatch(const_cast<BasicBlock *>(Inst->getParent()),
CatchHandler, Selector, NextBB)) {
ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
return CloningDirector::StopCloningBB;
}
// If eg.typeid.for is called for any other reason, it can be ignored.
VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
return CloningDirector::SkipInstruction;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleInvoke(
ValueToValueMapTy &VMap, const InvokeInst *Invoke, BasicBlock *NewBB) {
// All invokes in cleanup handlers can be replaced with calls.
SmallVector<Value *, 16> CallArgs(Invoke->op_begin(), Invoke->op_end() - 3);
// Insert a normal call instruction...
CallInst *NewCall =
CallInst::Create(const_cast<Value *>(Invoke->getCalledValue()), CallArgs,
Invoke->getName(), NewBB);
NewCall->setCallingConv(Invoke->getCallingConv());
NewCall->setAttributes(Invoke->getAttributes());
NewCall->setDebugLoc(Invoke->getDebugLoc());
VMap[Invoke] = NewCall;
// Insert an unconditional branch to the normal destination.
BranchInst::Create(Invoke->getNormalDest(), NewBB);
// The unwind destination won't be cloned into the new function, so
// we don't need to clean up its phi nodes.
// We just added a terminator to the cloned block.
// Tell the caller to stop processing the current basic block.
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleResume(
ValueToValueMapTy &VMap, const ResumeInst *Resume, BasicBlock *NewBB) {
ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
// We just added a terminator to the cloned block.
// Tell the caller to stop processing the current basic block so that
// the branch instruction will be skipped.
return CloningDirector::StopCloningBB;
}
WinEHFrameVariableMaterializer::WinEHFrameVariableMaterializer(
Function *OutlinedFn, FrameVarInfoMap &FrameVarInfo)
: FrameVarInfo(FrameVarInfo), Builder(OutlinedFn->getContext()) {
Builder.SetInsertPoint(&OutlinedFn->getEntryBlock());
}
Value *WinEHFrameVariableMaterializer::materializeValueFor(Value *V) {
// If we're asked to materialize a value that is an instruction, we
// temporarily create an alloca in the outlined function and add this
// to the FrameVarInfo map. When all the outlining is complete, we'll
// collect these into a structure, spilling non-alloca values in the
// parent frame as necessary, and replace these temporary allocas with
// GEPs referencing the frame allocation block.
// If the value is an alloca, the mapping is direct.
if (auto *AV = dyn_cast<AllocaInst>(V)) {
AllocaInst *NewAlloca = dyn_cast<AllocaInst>(AV->clone());
Builder.Insert(NewAlloca, AV->getName());
FrameVarInfo[AV].push_back(NewAlloca);
return NewAlloca;
}
// For other types of instructions or arguments, we need an alloca based on
// the value's type and a load of the alloca. The alloca will be replaced
// by a GEP, but the load will stay. In the parent function, the value will
// be spilled to a location in the frame allocation block.
if (isa<Instruction>(V) || isa<Argument>(V)) {
AllocaInst *NewAlloca =
Builder.CreateAlloca(V->getType(), nullptr, "eh.temp.alloca");
FrameVarInfo[V].push_back(NewAlloca);
LoadInst *NewLoad = Builder.CreateLoad(NewAlloca, V->getName() + ".reload");
return NewLoad;
}
// Don't materialize other values.
return nullptr;
}
// This function maps the catch and cleanup handlers that are reachable from the
// specified landing pad. The landing pad sequence will have this basic shape:
//
// <cleanup handler>
// <selector comparison>
// <catch handler>
// <cleanup handler>
// <selector comparison>
// <catch handler>
// <cleanup handler>
// ...
//
// Any of the cleanup slots may be absent. The cleanup slots may be occupied by
// any arbitrary control flow, but all paths through the cleanup code must
// eventually reach the next selector comparison and no path can skip to a
// different selector comparisons, though some paths may terminate abnormally.
// Therefore, we will use a depth first search from the start of any given
// cleanup block and stop searching when we find the next selector comparison.
//
// If the landingpad instruction does not have a catch clause, we will assume
// that any instructions other than selector comparisons and catch handlers can
// be ignored. In practice, these will only be the boilerplate instructions.
//
// The catch handlers may also have any control structure, but we are only
// interested in the start of the catch handlers, so we don't need to actually
// follow the flow of the catch handlers. The start of the catch handlers can
// be located from the compare instructions, but they can be skipped in the
// flow by following the contrary branch.
void WinEHPrepare::mapLandingPadBlocks(LandingPadInst *LPad,
LandingPadActions &Actions) {
unsigned int NumClauses = LPad->getNumClauses();
unsigned int HandlersFound = 0;
BasicBlock *BB = LPad->getParent();
DEBUG(dbgs() << "Mapping landing pad: " << BB->getName() << "\n");
if (NumClauses == 0) {
// This landing pad contains only cleanup code.
CleanupHandler *Action = new CleanupHandler(BB);
CleanupHandlerMap[BB] = Action;
Actions.insertCleanupHandler(Action);
DEBUG(dbgs() << " Assuming cleanup code in block " << BB->getName()
<< "\n");
assert(LPad->isCleanup());
return;
}
VisitedBlockSet VisitedBlocks;
while (HandlersFound != NumClauses) {
BasicBlock *NextBB = nullptr;
// See if the clause we're looking for is a catch-all.
// If so, the catch begins immediately.
if (isa<ConstantPointerNull>(LPad->getClause(HandlersFound))) {
// The catch all must occur last.
assert(HandlersFound == NumClauses - 1);
// See if there is any interesting code executed before the catch.
if (auto *CleanupAction = findCleanupHandler(BB, BB)) {
// Add a cleanup entry to the list
Actions.insertCleanupHandler(CleanupAction);
DEBUG(dbgs() << " Found cleanup code in block "
<< CleanupAction->getStartBlock()->getName() << "\n");
}
// Add the catch handler to the action list.
CatchHandler *Action =
new CatchHandler(BB, LPad->getClause(HandlersFound), nullptr);
CatchHandlerMap[BB] = Action;
Actions.insertCatchHandler(Action);
DEBUG(dbgs() << " Catch all handler at block " << BB->getName() << "\n");
++HandlersFound;
continue;
}
CatchHandler *CatchAction = findCatchHandler(BB, NextBB, VisitedBlocks);
// See if there is any interesting code executed before the dispatch.
if (auto *CleanupAction =
findCleanupHandler(BB, CatchAction->getStartBlock())) {
// Add a cleanup entry to the list
Actions.insertCleanupHandler(CleanupAction);
DEBUG(dbgs() << " Found cleanup code in block "
<< CleanupAction->getStartBlock()->getName() << "\n");
}
assert(CatchAction);
++HandlersFound;
// Add the catch handler to the action list.
Actions.insertCatchHandler(CatchAction);
DEBUG(dbgs() << " Found catch dispatch in block "
<< CatchAction->getStartBlock()->getName() << "\n");
// Move on to the block after the catch handler.
BB = NextBB;
}
// See if there is any interesting code executed before the resume.
if (auto *CleanupAction = findCleanupHandler(BB, BB)) {
// Add a cleanup entry to the list
Actions.insertCleanupHandler(CleanupAction);
DEBUG(dbgs() << " Found cleanup code in block "
<< CleanupAction->getStartBlock()->getName() << "\n");
}
// It's possible that some optimization moved code into a landingpad that
// wasn't
// previously being used for cleanup. If that happens, we need to execute
// that
// extra code from a cleanup handler.
if (Actions.includesCleanup() && !LPad->isCleanup())
LPad->setCleanup(true);
}
// This function searches starting with the input block for the next
// block that terminates with a branch whose condition is based on a selector
// comparison. This may be the input block. See the mapLandingPadBlocks
// comments for a discussion of control flow assumptions.
//
CatchHandler *WinEHPrepare::findCatchHandler(BasicBlock *BB,
BasicBlock *&NextBB,
VisitedBlockSet &VisitedBlocks) {
// See if we've already found a catch handler use it.
// Call count() first to avoid creating a null entry for blocks
// we haven't seen before.
if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
CatchHandler *Action = cast<CatchHandler>(CatchHandlerMap[BB]);
NextBB = Action->getNextBB();
return Action;
}
// VisitedBlocks applies only to the current search. We still
// need to consider blocks that we've visited while mapping other
// landing pads.
VisitedBlocks.insert(BB);
BasicBlock *CatchBlock = nullptr;
Constant *Selector = nullptr;
// If this is the first time we've visited this block from any landing pad
// look to see if it is a selector dispatch block.
if (!CatchHandlerMap.count(BB)) {
if (isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
CatchHandler *Action = new CatchHandler(BB, Selector, NextBB);
CatchHandlerMap[BB] = Action;
return Action;
}
}
// Visit each successor, looking for the dispatch.
// FIXME: We expect to find the dispatch quickly, so this will probably
// work better as a breadth first search.
for (BasicBlock *Succ : successors(BB)) {
if (VisitedBlocks.count(Succ))
continue;
CatchHandler *Action = findCatchHandler(Succ, NextBB, VisitedBlocks);
if (Action)
return Action;
}
return nullptr;
}
// These are helper functions to combine repeated code from findCleanupHandler.
static CleanupHandler *createCleanupHandler(CleanupHandlerMapTy &CleanupHandlerMap,
BasicBlock *BB) {
CleanupHandler *Action = new CleanupHandler(BB);
CleanupHandlerMap[BB] = Action;
return Action;
}
// This function searches starting with the input block for the next block that
// contains code that is not part of a catch handler and would not be eliminated
// during handler outlining.
//
CleanupHandler *WinEHPrepare::findCleanupHandler(BasicBlock *StartBB,
BasicBlock *EndBB) {
// Here we will skip over the following:
//
// landing pad prolog:
//
// Unconditional branches
//
// Selector dispatch
//
// Resume pattern
//
// Anything else marks the start of an interesting block
BasicBlock *BB = StartBB;
// Anything other than an unconditional branch will kick us out of this loop
// one way or another.
while (BB) {
// If we've already scanned this block, don't scan it again. If it is
// a cleanup block, there will be an action in the CleanupHandlerMap.
// If we've scanned it and it is not a cleanup block, there will be a
// nullptr in the CleanupHandlerMap. If we have not scanned it, there will
// be no entry in the CleanupHandlerMap. We must call count() first to
// avoid creating a null entry for blocks we haven't scanned.
if (CleanupHandlerMap.count(BB)) {
if (auto *Action = CleanupHandlerMap[BB]) {
return cast<CleanupHandler>(Action);
} else {
// Here we handle the case where the cleanup handler map contains a
// value for this block but the value is a nullptr. This means that
// we have previously analyzed the block and determined that it did
// not contain any cleanup code. Based on the earlier analysis, we
// know the the block must end in either an unconditional branch, a
// resume or a conditional branch that is predicated on a comparison
// with a selector. Either the resume or the selector dispatch
// would terminate the search for cleanup code, so the unconditional
// branch is the only case for which we might need to continue
// searching.
if (BB == EndBB)
return nullptr;
BasicBlock *SuccBB;
if (!match(BB->getTerminator(), m_UnconditionalBr(SuccBB)))
return nullptr;
BB = SuccBB;
continue;
}
}
// Create an entry in the cleanup handler map for this block. Initially
// we create an entry that says this isn't a cleanup block. If we find
// cleanup code, the caller will replace this entry.
CleanupHandlerMap[BB] = nullptr;
TerminatorInst *Terminator = BB->getTerminator();
// Landing pad blocks have extra instructions we need to accept.
LandingPadMap *LPadMap = nullptr;
if (BB->isLandingPad()) {
LandingPadInst *LPad = BB->getLandingPadInst();
LPadMap = &LPadMaps[LPad];
if (!LPadMap->isInitialized())
LPadMap->mapLandingPad(LPad);
}
// Look for the bare resume pattern:
// %exn2 = load i8** %exn.slot
// %sel2 = load i32* %ehselector.slot
// %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn2, 0
// %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel2, 1
// resume { i8*, i32 } %lpad.val2
if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
InsertValueInst *Insert1 = nullptr;
InsertValueInst *Insert2 = nullptr;
if (!isa<PHINode>(Resume->getOperand(0))) {
Insert2 = dyn_cast<InsertValueInst>(Resume->getOperand(0));
if (!Insert2)
return createCleanupHandler(CleanupHandlerMap, BB);
Insert1 = dyn_cast<InsertValueInst>(Insert2->getAggregateOperand());
if (!Insert1)
return createCleanupHandler(CleanupHandlerMap, BB);
}
for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
II != IE; ++II) {
Instruction *Inst = II;
if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
continue;
if (Inst == Insert1 || Inst == Insert2 || Inst == Resume)
continue;
if (!Inst->hasOneUse() ||
(Inst->user_back() != Insert1 && Inst->user_back() != Insert2)) {
return createCleanupHandler(CleanupHandlerMap, BB);
}
}
return nullptr;
}
BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
if (Branch) {
if (Branch->isConditional()) {
// Look for the selector dispatch.
// %sel = load i32* %ehselector.slot
// %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
// %matches = icmp eq i32 %sel12, %2
// br i1 %matches, label %catch14, label %eh.resume
CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
if (!Compare || !Compare->isEquality())
return createCleanupHandler(CleanupHandlerMap, BB);
for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(),
IE = BB->end();
II != IE; ++II) {
Instruction *Inst = II;
if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
continue;
if (Inst == Compare || Inst == Branch)
continue;
if (!Inst->hasOneUse() || (Inst->user_back() != Compare))
return createCleanupHandler(CleanupHandlerMap, BB);
if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
continue;
if (!isa<LoadInst>(Inst))
return createCleanupHandler(CleanupHandlerMap, BB);
}
// The selector dispatch block should always terminate our search.
assert(BB == EndBB);
return nullptr;
} else {
// Look for empty blocks with unconditional branches.
for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(),
IE = BB->end();
II != IE; ++II) {
Instruction *Inst = II;
if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
continue;
if (Inst == Branch)
continue;
if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
continue;
// Anything else makes this interesting cleanup code.
return createCleanupHandler(CleanupHandlerMap, BB);
}
if (BB == EndBB)
return nullptr;
// The branch was unconditional.
BB = Branch->getSuccessor(0);
continue;
} // End else of if branch was conditional
} // End if Branch
// Anything else makes this interesting cleanup code.
return createCleanupHandler(CleanupHandlerMap, BB);
}
return nullptr;
}
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