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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/ADT/MapVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Analysis/LibCallSemantics.h"
#include "llvm/CodeGen/WinEHFuncInfo.h"
#include "llvm/IR/Dominators.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/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/PromoteMemToReg.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;
// TinyPtrVector cannot hold nullptr, so we need our own sentinel that isn't
// quite null.
AllocaInst *getCatchObjectSentinel() {
return static_cast<AllocaInst *>(nullptr) + 1;
}
typedef SmallSet<BasicBlock *, 4> VisitedBlockSet;
class LandingPadActions;
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) {
if (TM)
TheTriple = Triple(TM->getTargetTriple());
}
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 prepareExceptionHandlers(Function &F,
SmallVectorImpl<LandingPadInst *> &LPads);
void promoteLandingPadValues(LandingPadInst *LPad);
void demoteValuesLiveAcrossHandlers(Function &F,
SmallVectorImpl<LandingPadInst *> &LPads);
void findSEHEHReturnPoints(Function &F,
SetVector<BasicBlock *> &EHReturnBlocks);
void findCXXEHReturnPoints(Function &F,
SetVector<BasicBlock *> &EHReturnBlocks);
void getPossibleReturnTargets(Function *ParentF, Function *HandlerF,
SetVector<BasicBlock*> &Targets);
void completeNestedLandingPad(Function *ParentFn,
LandingPadInst *OutlinedLPad,
const LandingPadInst *OriginalLPad,
FrameVarInfoMap &VarInfo);
Function *createHandlerFunc(Type *RetTy, const Twine &Name, Module *M,
Value *&ParentFP);
bool outlineHandler(ActionHandler *Action, Function *SrcFn,
LandingPadInst *LPad, BasicBlock *StartBB,
FrameVarInfoMap &VarInfo);
void addStubInvokeToHandlerIfNeeded(Function *Handler, Value *PersonalityFn);
void mapLandingPadBlocks(LandingPadInst *LPad, LandingPadActions &Actions);
CatchHandler *findCatchHandler(BasicBlock *BB, BasicBlock *&NextBB,
VisitedBlockSet &VisitedBlocks);
void findCleanupHandlers(LandingPadActions &Actions, BasicBlock *StartBB,
BasicBlock *EndBB);
void processSEHCatchHandler(CatchHandler *Handler, BasicBlock *StartBB);
Triple TheTriple;
// All fields are reset by runOnFunction.
DominatorTree *DT = nullptr;
EHPersonality Personality = EHPersonality::Unknown;
CatchHandlerMapTy CatchHandlerMap;
CleanupHandlerMapTy CleanupHandlerMap;
DenseMap<const LandingPadInst *, LandingPadMap> LPadMaps;
// This maps landing pad instructions found in outlined handlers to
// the landing pad instruction in the parent function from which they
// were cloned. The cloned/nested landing pad is used as the key
// because the landing pad may be cloned into multiple handlers.
// This map will be used to add the llvm.eh.actions call to the nested
// landing pads after all handlers have been outlined.
DenseMap<LandingPadInst *, const LandingPadInst *> NestedLPtoOriginalLP;
// This maps blocks in the parent function which are destinations of
// catch handlers to cloned blocks in (other) outlined handlers. This
// handles the case where a nested landing pads has a catch handler that
// returns to a handler function rather than the parent function.
// The original block is used as the key here because there should only
// ever be one handler function from which the cloned block is not pruned.
// The original block will be pruned from the parent function after all
// handlers have been outlined. This map will be used to adjust the
// return instructions of handlers which return to the block that was
// outlined into a handler. This is done after all handlers have been
// outlined but before the outlined code is pruned from the parent function.
DenseMap<const BasicBlock *, BasicBlock *> LPadTargetBlocks;
// Map from outlined handler to call to llvm.frameaddress(1). Only used for
// 32-bit EH.
DenseMap<Function *, Value *> HandlerToParentFP;
AllocaInst *SEHExceptionCodeSlot = nullptr;
};
class WinEHFrameVariableMaterializer : public ValueMaterializer {
public:
WinEHFrameVariableMaterializer(Function *OutlinedFn, Value *ParentFP,
FrameVarInfoMap &FrameVarInfo);
~WinEHFrameVariableMaterializer() override {}
Value *materializeValueFor(Value *V) override;
void escapeCatchObject(Value *V);
private:
FrameVarInfoMap &FrameVarInfo;
IRBuilder<> Builder;
};
class LandingPadMap {
public:
LandingPadMap() : OriginLPad(nullptr) {}
void mapLandingPad(const LandingPadInst *LPad);
bool isInitialized() { return OriginLPad != nullptr; }
bool isOriginLandingPadBlock(const BasicBlock *BB) const;
bool isLandingPadSpecificInst(const Instruction *Inst) const;
void remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
Value *SelectorValue) const;
private:
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;
};
class WinEHCloningDirectorBase : public CloningDirector {
public:
WinEHCloningDirectorBase(Function *HandlerFn, Value *ParentFP,
FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap)
: Materializer(HandlerFn, ParentFP, VarInfo),
SelectorIDType(Type::getInt32Ty(HandlerFn->getContext())),
Int8PtrType(Type::getInt8PtrTy(HandlerFn->getContext())),
LPadMap(LPadMap), ParentFP(ParentFP) {}
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;
virtual CloningAction handleCompare(ValueToValueMapTy &VMap,
const CmpInst *Compare,
BasicBlock *NewBB) = 0;
virtual CloningAction handleLandingPad(ValueToValueMapTy &VMap,
const LandingPadInst *LPad,
BasicBlock *NewBB) = 0;
ValueMaterializer *getValueMaterializer() override { return &Materializer; }
protected:
WinEHFrameVariableMaterializer Materializer;
Type *SelectorIDType;
Type *Int8PtrType;
LandingPadMap &LPadMap;
/// The value representing the parent frame pointer.
Value *ParentFP;
};
class WinEHCatchDirector : public WinEHCloningDirectorBase {
public:
WinEHCatchDirector(
Function *CatchFn, Value *ParentFP, Value *Selector,
FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap,
DenseMap<LandingPadInst *, const LandingPadInst *> &NestedLPads)
: WinEHCloningDirectorBase(CatchFn, ParentFP, VarInfo, LPadMap),
CurrentSelector(Selector->stripPointerCasts()),
ExceptionObjectVar(nullptr), NestedLPtoOriginalLP(NestedLPads) {}
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;
CloningAction handleCompare(ValueToValueMapTy &VMap, const CmpInst *Compare,
BasicBlock *NewBB) override;
CloningAction handleLandingPad(ValueToValueMapTy &VMap,
const LandingPadInst *LPad,
BasicBlock *NewBB) override;
Value *getExceptionVar() { return ExceptionObjectVar; }
TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
private:
Value *CurrentSelector;
Value *ExceptionObjectVar;
TinyPtrVector<BasicBlock *> ReturnTargets;
// This will be a reference to the field of the same name in the WinEHPrepare
// object which instantiates this WinEHCatchDirector object.
DenseMap<LandingPadInst *, const LandingPadInst *> &NestedLPtoOriginalLP;
};
class WinEHCleanupDirector : public WinEHCloningDirectorBase {
public:
WinEHCleanupDirector(Function *CleanupFn, Value *ParentFP,
FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap)
: WinEHCloningDirectorBase(CleanupFn, ParentFP, 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;
CloningAction handleCompare(ValueToValueMapTy &VMap, const CmpInst *Compare,
BasicBlock *NewBB) override;
CloningAction handleLandingPad(ValueToValueMapTy &VMap,
const LandingPadInst *LPad,
BasicBlock *NewBB) override;
};
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 *> &actions() { return Actions; }
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) {
// No need to prepare outlined handlers.
if (Fn.hasFnAttribute("wineh-parent"))
return false;
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.
Personality = classifyEHPersonality(LPads.back()->getPersonalityFn());
// Do nothing if this is not an MSVC personality.
if (!isMSVCEHPersonality(Personality))
return false;
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
// If there were any landing pads, prepareExceptionHandlers will make changes.
prepareExceptionHandlers(Fn, LPads);
return true;
}
bool WinEHPrepare::doFinalization(Module &M) { return false; }
void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<DominatorTreeWrapperPass>();
}
static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
Constant *&Selector, BasicBlock *&NextBB);
// Finds blocks reachable from the starting set Worklist. Does not follow unwind
// edges or blocks listed in StopPoints.
static void findReachableBlocks(SmallPtrSetImpl<BasicBlock *> &ReachableBBs,
SetVector<BasicBlock *> &Worklist,
const SetVector<BasicBlock *> *StopPoints) {
while (!Worklist.empty()) {
BasicBlock *BB = Worklist.pop_back_val();
// Don't cross blocks that we should stop at.
if (StopPoints && StopPoints->count(BB))
continue;
if (!ReachableBBs.insert(BB).second)
continue; // Already visited.
// Don't follow unwind edges of invokes.
if (auto *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
Worklist.insert(II->getNormalDest());
continue;
}
// Otherwise, follow all successors.
Worklist.insert(succ_begin(BB), succ_end(BB));
}
}
// Attempt to find an instruction where a block can be split before
// a call to llvm.eh.begincatch and its operands. If the block
// begins with the begincatch call or one of its adjacent operands
// the block will not be split.
static Instruction *findBeginCatchSplitPoint(BasicBlock *BB,
IntrinsicInst *II) {
// If the begincatch call is already the first instruction in the block,
// don't split.
Instruction *FirstNonPHI = BB->getFirstNonPHI();
if (II == FirstNonPHI)
return nullptr;
// If either operand is in the same basic block as the instruction and
// isn't used by another instruction before the begincatch call, include it
// in the split block.
auto *Op0 = dyn_cast<Instruction>(II->getOperand(0));
auto *Op1 = dyn_cast<Instruction>(II->getOperand(1));
Instruction *I = II->getPrevNode();
Instruction *LastI = II;
while (I == Op0 || I == Op1) {
// If the block begins with one of the operands and there are no other
// instructions between the operand and the begincatch call, don't split.
if (I == FirstNonPHI)
return nullptr;
LastI = I;
I = I->getPrevNode();
}
// If there is at least one instruction in the block before the begincatch
// call and its operands, split the block at either the begincatch or
// its operand.
return LastI;
}
/// Find all points where exceptional control rejoins normal control flow via
/// llvm.eh.endcatch. Add them to the normal bb reachability worklist.
void WinEHPrepare::findCXXEHReturnPoints(
Function &F, SetVector<BasicBlock *> &EHReturnBlocks) {
for (auto BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
BasicBlock *BB = BBI;
for (Instruction &I : *BB) {
if (match(&I, m_Intrinsic<Intrinsic::eh_begincatch>())) {
Instruction *SplitPt =
findBeginCatchSplitPoint(BB, cast<IntrinsicInst>(&I));
if (SplitPt) {
// Split the block before the llvm.eh.begincatch call to allow
// cleanup and catch code to be distinguished later.
// Do not update BBI because we still need to process the
// portion of the block that we are splitting off.
SplitBlock(BB, SplitPt, DT);
break;
}
}
if (match(&I, m_Intrinsic<Intrinsic::eh_endcatch>())) {
// Split the block after the call to llvm.eh.endcatch if there is
// anything other than an unconditional branch, or if the successor
// starts with a phi.
auto *Br = dyn_cast<BranchInst>(I.getNextNode());
if (!Br || !Br->isUnconditional() ||
isa<PHINode>(Br->getSuccessor(0)->begin())) {
DEBUG(dbgs() << "splitting block " << BB->getName()
<< " with llvm.eh.endcatch\n");
BBI = SplitBlock(BB, I.getNextNode(), DT);
}
// The next BB is normal control flow.
EHReturnBlocks.insert(BB->getTerminator()->getSuccessor(0));
break;
}
}
}
}
static bool isCatchAllLandingPad(const BasicBlock *BB) {
const LandingPadInst *LP = BB->getLandingPadInst();
if (!LP)
return false;
unsigned N = LP->getNumClauses();
return (N > 0 && LP->isCatch(N - 1) &&
isa<ConstantPointerNull>(LP->getClause(N - 1)));
}
/// Find all points where exceptions control rejoins normal control flow via
/// selector dispatch.
void WinEHPrepare::findSEHEHReturnPoints(
Function &F, SetVector<BasicBlock *> &EHReturnBlocks) {
for (auto BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
BasicBlock *BB = BBI;
// If the landingpad is a catch-all, treat the whole lpad as if it is
// reachable from normal control flow.
// FIXME: This is imprecise. We need a better way of identifying where a
// catch-all starts and cleanups stop. As far as LLVM is concerned, there
// is no difference.
if (isCatchAllLandingPad(BB)) {
EHReturnBlocks.insert(BB);
continue;
}
BasicBlock *CatchHandler;
BasicBlock *NextBB;
Constant *Selector;
if (isSelectorDispatch(BB, CatchHandler, Selector, NextBB)) {
// Split the edge if there is a phi node. Returning from EH to a phi node
// is just as impossible as having a phi after an indirectbr.
if (isa<PHINode>(CatchHandler->begin())) {
DEBUG(dbgs() << "splitting EH return edge from " << BB->getName()
<< " to " << CatchHandler->getName() << '\n');
BBI = CatchHandler = SplitCriticalEdge(
BB, std::find(succ_begin(BB), succ_end(BB), CatchHandler));
}
EHReturnBlocks.insert(CatchHandler);
}
}
}
/// Ensure that all values live into and out of exception handlers are stored
/// in memory.
/// FIXME: This falls down when values are defined in one handler and live into
/// another handler. For example, a cleanup defines a value used only by a
/// catch handler.
void WinEHPrepare::demoteValuesLiveAcrossHandlers(
Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
DEBUG(dbgs() << "Demoting values live across exception handlers in function "
<< F.getName() << '\n');
// Build a set of all non-exceptional blocks and exceptional blocks.
// - Non-exceptional blocks are blocks reachable from the entry block while
// not following invoke unwind edges.
// - Exceptional blocks are blocks reachable from landingpads. Analysis does
// not follow llvm.eh.endcatch blocks, which mark a transition from
// exceptional to normal control.
SmallPtrSet<BasicBlock *, 4> NormalBlocks;
SmallPtrSet<BasicBlock *, 4> EHBlocks;
SetVector<BasicBlock *> EHReturnBlocks;
SetVector<BasicBlock *> Worklist;
if (Personality == EHPersonality::MSVC_CXX)
findCXXEHReturnPoints(F, EHReturnBlocks);
else
findSEHEHReturnPoints(F, EHReturnBlocks);
DEBUG({
dbgs() << "identified the following blocks as EH return points:\n";
for (BasicBlock *BB : EHReturnBlocks)
dbgs() << " " << BB->getName() << '\n';
});
// Join points should not have phis at this point, unless they are a
// landingpad, in which case we will demote their phis later.
#ifndef NDEBUG
for (BasicBlock *BB : EHReturnBlocks)
assert((BB->isLandingPad() || !isa<PHINode>(BB->begin())) &&
"non-lpad EH return block has phi");
#endif
// Normal blocks are the blocks reachable from the entry block and all EH
// return points.
Worklist = EHReturnBlocks;
Worklist.insert(&F.getEntryBlock());
findReachableBlocks(NormalBlocks, Worklist, nullptr);
DEBUG({
dbgs() << "marked the following blocks as normal:\n";
for (BasicBlock *BB : NormalBlocks)
dbgs() << " " << BB->getName() << '\n';
});
// Exceptional blocks are the blocks reachable from landingpads that don't
// cross EH return points.
Worklist.clear();
for (auto *LPI : LPads)
Worklist.insert(LPI->getParent());
findReachableBlocks(EHBlocks, Worklist, &EHReturnBlocks);
DEBUG({
dbgs() << "marked the following blocks as exceptional:\n";
for (BasicBlock *BB : EHBlocks)
dbgs() << " " << BB->getName() << '\n';
});
SetVector<Argument *> ArgsToDemote;
SetVector<Instruction *> InstrsToDemote;
for (BasicBlock &BB : F) {
bool IsNormalBB = NormalBlocks.count(&BB);
bool IsEHBB = EHBlocks.count(&BB);
if (!IsNormalBB && !IsEHBB)
continue; // Blocks that are neither normal nor EH are unreachable.
for (Instruction &I : BB) {
for (Value *Op : I.operands()) {
// Don't demote static allocas, constants, and labels.
if (isa<Constant>(Op) || isa<BasicBlock>(Op) || isa<InlineAsm>(Op))
continue;
auto *AI = dyn_cast<AllocaInst>(Op);
if (AI && AI->isStaticAlloca())
continue;
if (auto *Arg = dyn_cast<Argument>(Op)) {
if (IsEHBB) {
DEBUG(dbgs() << "Demoting argument " << *Arg
<< " used by EH instr: " << I << "\n");
ArgsToDemote.insert(Arg);
}
continue;
}
auto *OpI = cast<Instruction>(Op);
BasicBlock *OpBB = OpI->getParent();
// If a value is produced and consumed in the same BB, we don't need to
// demote it.
if (OpBB == &BB)
continue;
bool IsOpNormalBB = NormalBlocks.count(OpBB);
bool IsOpEHBB = EHBlocks.count(OpBB);
if (IsNormalBB != IsOpNormalBB || IsEHBB != IsOpEHBB) {
DEBUG({
dbgs() << "Demoting instruction live in-out from EH:\n";
dbgs() << "Instr: " << *OpI << '\n';
dbgs() << "User: " << I << '\n';
});
InstrsToDemote.insert(OpI);
}
}
}
}
// Demote values live into and out of handlers.
// FIXME: This demotion is inefficient. We should insert spills at the point
// of definition, insert one reload in each handler that uses the value, and
// insert reloads in the BB used to rejoin normal control flow.
Instruction *AllocaInsertPt = F.getEntryBlock().getFirstInsertionPt();
for (Instruction *I : InstrsToDemote)
DemoteRegToStack(*I, false, AllocaInsertPt);
// Demote arguments separately, and only for uses in EH blocks.
for (Argument *Arg : ArgsToDemote) {
auto *Slot = new AllocaInst(Arg->getType(), nullptr,
Arg->getName() + ".reg2mem", AllocaInsertPt);
SmallVector<User *, 4> Users(Arg->user_begin(), Arg->user_end());
for (User *U : Users) {
auto *I = dyn_cast<Instruction>(U);
if (I && EHBlocks.count(I->getParent())) {
auto *Reload = new LoadInst(Slot, Arg->getName() + ".reload", false, I);
U->replaceUsesOfWith(Arg, Reload);
}
}
new StoreInst(Arg, Slot, AllocaInsertPt);
}
// Demote landingpad phis, as the landingpad will be removed from the machine
// CFG.
for (LandingPadInst *LPI : LPads) {
BasicBlock *BB = LPI->getParent();
while (auto *Phi = dyn_cast<PHINode>(BB->begin()))
DemotePHIToStack(Phi, AllocaInsertPt);
}
DEBUG(dbgs() << "Demoted " << InstrsToDemote.size() << " instructions and "
<< ArgsToDemote.size() << " arguments for WinEHPrepare\n\n");
}
bool WinEHPrepare::prepareExceptionHandlers(
Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
// Don't run on functions that are already prepared.
for (LandingPadInst *LPad : LPads) {
BasicBlock *LPadBB = LPad->getParent();
for (Instruction &Inst : *LPadBB)
if (match(&Inst, m_Intrinsic<Intrinsic::eh_actions>()))
return false;
}
demoteValuesLiveAcrossHandlers(F, 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);
if (isAsynchronousEHPersonality(Personality)) {
// FIXME: Switch the ehptr type to i32 and then switch this.
SEHExceptionCodeSlot =
new AllocaInst(Int8PtrType, nullptr, "seh_exception_code",
F.getEntryBlock().getFirstInsertionPt());
}
// This container stores the llvm.eh.recover and IndirectBr instructions
// that make up the body of each landing pad after it has been outlined.
// We need to defer the population of the target list for the indirectbr
// until all landing pads have been outlined so that we can handle the
// case of blocks in the target that are reached only from nested
// landing pads.
SmallVector<std::pair<CallInst*, IndirectBrInst *>, 4> LPadImpls;
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) {
if (match(&Inst, m_Intrinsic<Intrinsic::eh_actions>())) {
LPadHasActionList = true;
break;
}
}
// If we've already outlined the handlers for this landingpad,
// there's nothing more to do here.
if (LPadHasActionList)
continue;
// If either of the values in the aggregate returned by the landing pad is
// extracted and stored to memory, promote the stored value to a register.
promoteLandingPadValues(LPad);
LandingPadActions Actions;
mapLandingPadBlocks(LPad, Actions);
HandlersOutlined |= !Actions.actions().empty();
for (ActionHandler *Action : Actions) {
if (Action->hasBeenProcessed())
continue;
BasicBlock *StartBB = Action->getStartBlock();
// SEH doesn't do any outlining for catches. Instead, pass the handler
// basic block addr to llvm.eh.actions and list the block as a return
// target.
if (isAsynchronousEHPersonality(Personality)) {
if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
processSEHCatchHandler(CatchAction, StartBB);
continue;
}
}
outlineHandler(Action, &F, LPad, StartBB, FrameVarInfo);
}
// Split the block after the landingpad instruction so that it is just a
// call to llvm.eh.actions followed by indirectbr.
assert(!isa<PHINode>(LPadBB->begin()) && "lpad phi not removed");
SplitBlock(LPadBB, LPad->getNextNode(), DT);
// Erase the branch inserted by the split so we can insert indirectbr.
LPadBB->getTerminator()->eraseFromParent();
// Replace all extracted values with undef and ultimately replace the
// landingpad with undef.
SmallVector<Instruction *, 4> SEHCodeUses;
SmallVector<Instruction *, 4> EHUndefs;
for (User *U : LPad->users()) {
auto *E = dyn_cast<ExtractValueInst>(U);
if (!E)
continue;
assert(E->getNumIndices() == 1 &&
"Unexpected operation: extracting both landing pad values");
unsigned Idx = *E->idx_begin();
assert((Idx == 0 || Idx == 1) && "unexpected index");
if (Idx == 0 && isAsynchronousEHPersonality(Personality))
SEHCodeUses.push_back(E);
else
EHUndefs.push_back(E);
}
for (Instruction *E : EHUndefs) {
E->replaceAllUsesWith(UndefValue::get(E->getType()));
E->eraseFromParent();
}
LPad->replaceAllUsesWith(UndefValue::get(LPad->getType()));
// Rewrite uses of the exception pointer to loads of an alloca.
for (Instruction *E : SEHCodeUses) {
SmallVector<Use *, 4> Uses;
for (Use &U : E->uses())
Uses.push_back(&U);
for (Use *U : Uses) {
auto *I = cast<Instruction>(U->getUser());
if (isa<ResumeInst>(I))
continue;
LoadInst *LI;
if (auto *Phi = dyn_cast<PHINode>(I))
LI = new LoadInst(SEHExceptionCodeSlot, "sehcode", false,
Phi->getIncomingBlock(*U));
else
LI = new LoadInst(SEHExceptionCodeSlot, "sehcode", false, I);
U->set(LI);
}
E->replaceAllUsesWith(UndefValue::get(E->getType()));
E->eraseFromParent();
}
// Add a call to describe the actions for this landing pad.
std::vector<Value *> ActionArgs;
for (ActionHandler *Action : Actions) {
// Action codes from docs are: 0 cleanup, 1 catch.
if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
ActionArgs.push_back(ConstantInt::get(Int32Type, 1));
ActionArgs.push_back(CatchAction->getSelector());
// Find the frame escape index of the exception object alloca in the
// parent.
int FrameEscapeIdx = -1;
Value *EHObj = const_cast<Value *>(CatchAction->getExceptionVar());
if (EHObj && !isa<ConstantPointerNull>(EHObj)) {
auto I = FrameVarInfo.find(EHObj);
assert(I != FrameVarInfo.end() &&
"failed to map llvm.eh.begincatch var");
FrameEscapeIdx = std::distance(FrameVarInfo.begin(), I);
}
ActionArgs.push_back(ConstantInt::get(Int32Type, FrameEscapeIdx));
} else {
ActionArgs.push_back(ConstantInt::get(Int32Type, 0));
}
ActionArgs.push_back(Action->getHandlerBlockOrFunc());
}
CallInst *Recover =
CallInst::Create(ActionIntrin, ActionArgs, "recover", LPadBB);
if (isAsynchronousEHPersonality(Personality)) {
// SEH can create the target list directly, since catch handlers
// are not outlined.
SetVector<BasicBlock *> ReturnTargets;
for (ActionHandler *Action : Actions) {
if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
const auto &CatchTargets = CatchAction->getReturnTargets();
ReturnTargets.insert(CatchTargets.begin(), CatchTargets.end());
}
}
IndirectBrInst *Branch =
IndirectBrInst::Create(Recover, ReturnTargets.size(), LPadBB);
for (BasicBlock *Target : ReturnTargets)
Branch->addDestination(Target);
} else {
// C++ EH must defer populating the targets to handle the case of
// targets that are reached indirectly through nested landing pads.
IndirectBrInst *Branch =
IndirectBrInst::Create(Recover, 0, LPadBB);
LPadImpls.push_back(std::make_pair(Recover, Branch));
}
} // End for each landingpad
// If nothing got outlined, there is no more processing to be done.
if (!HandlersOutlined)
return false;
// Replace any nested landing pad stubs with the correct action handler.
// This must be done before we remove unreachable blocks because it
// cleans up references to outlined blocks that will be deleted.
for (auto &LPadPair : NestedLPtoOriginalLP)
completeNestedLandingPad(&F, LPadPair.first, LPadPair.second, FrameVarInfo);
NestedLPtoOriginalLP.clear();
// Populate the indirectbr instructions' target lists if we deferred
// doing so above.
SetVector<BasicBlock*> CheckedTargets;
SmallVector<std::unique_ptr<ActionHandler>, 4> ActionList;
for (auto &LPadImplPair : LPadImpls) {
IntrinsicInst *Recover = cast<IntrinsicInst>(LPadImplPair.first);
IndirectBrInst *Branch = LPadImplPair.second;
// Get a list of handlers called by
parseEHActions(Recover, ActionList);
// Add an indirect branch listing possible successors of the catch handlers.
SetVector<BasicBlock *> ReturnTargets;
for (const auto &Action : ActionList) {
if (auto *CA = dyn_cast<CatchHandler>(Action.get())) {
Function *Handler = cast<Function>(CA->getHandlerBlockOrFunc());
getPossibleReturnTargets(&F, Handler, ReturnTargets);
}
}
ActionList.clear();
for (BasicBlock *Target : ReturnTargets) {
Branch->addDestination(Target);
// The target may be a block that we excepted to get pruned.
// If it is, it may contain a call to llvm.eh.endcatch.
if (CheckedTargets.insert(Target)) {
// Earlier preparations guarantee that all calls to llvm.eh.endcatch
// will be followed by an unconditional branch.
auto *Br = dyn_cast<BranchInst>(Target->getTerminator());
if (Br && Br->isUnconditional() &&
Br != Target->getFirstNonPHIOrDbgOrLifetime()) {
Instruction *Prev = Br->getPrevNode();
if (match(cast<Value>(Prev), m_Intrinsic<Intrinsic::eh_endcatch>()))
Prev->eraseFromParent();
}
}
}
}
LPadImpls.clear();
F.addFnAttr("wineh-parent", F.getName());
// 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);
SmallVector<Value *, 8> AllocasToEscape;
// Scan the entry block for an existing call to llvm.frameescape. We need to
// keep escaping those objects.
for (Instruction &I : F.front()) {
auto *II = dyn_cast<IntrinsicInst>(&I);
if (II && II->getIntrinsicID() == Intrinsic::frameescape) {
auto Args = II->arg_operands();
AllocasToEscape.append(Args.begin(), Args.end());
II->eraseFromParent();
break;
}
}
// Finally, replace all of the temporary allocas for frame variables used in
// the outlined handlers with calls to llvm.framerecover.
for (auto &VarInfoEntry : FrameVarInfo) {
Value *ParentVal = VarInfoEntry.first;
TinyPtrVector<AllocaInst *> &Allocas = VarInfoEntry.second;
AllocaInst *ParentAlloca = cast<AllocaInst>(ParentVal);
// FIXME: We should try to sink unescaped allocas from the parent frame into
// the child frame. If the alloca is escaped, we have to use the lifetime
// markers to ensure that the alloca is only live within the child frame.
// 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) {
if (TempAlloca == getCatchObjectSentinel())
continue; // Skip catch parameter sentinels.
Function *HandlerFn = TempAlloca->getParent()->getParent();
llvm::Value *FP = HandlerToParentFP[HandlerFn];
assert(FP);
// FIXME: Sink this framerecover into the blocks where it is used.
Builder.SetInsertPoint(TempAlloca);
Builder.SetCurrentDebugLocation(TempAlloca->getDebugLoc());
Value *RecoverArgs[] = {
Builder.CreateBitCast(&F, Int8PtrType, ""), FP,
llvm::ConstantInt::get(Int32Type, AllocasToEscape.size() - 1)};
Instruction *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 = cast<Instruction>(
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);
if (SEHExceptionCodeSlot) {
if (SEHExceptionCodeSlot->hasNUses(0))
SEHExceptionCodeSlot->eraseFromParent();
else if (isAllocaPromotable(SEHExceptionCodeSlot))
PromoteMemToReg(SEHExceptionCodeSlot, *DT);
}
// Clean up the handler action maps we created for this function
DeleteContainerSeconds(CatchHandlerMap);
CatchHandlerMap.clear();
DeleteContainerSeconds(CleanupHandlerMap);
CleanupHandlerMap.clear();
HandlerToParentFP.clear();
DT = nullptr;
SEHExceptionCodeSlot = nullptr;
return HandlersOutlined;
}
void WinEHPrepare::promoteLandingPadValues(LandingPadInst *LPad) {
// If the return values of the landing pad instruction are extracted and
// stored to memory, we want to promote the store locations to reg values.
SmallVector<AllocaInst *, 2> EHAllocas;
// 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()) {
ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
if (!Extract)
continue;
for (auto *EU : Extract->users()) {
if (auto *Store = dyn_cast<StoreInst>(EU)) {
auto *AV = cast<AllocaInst>(Store->getPointerOperand());
EHAllocas.push_back(AV);
}
}
}
// We can't do this without a dominator tree.
assert(DT);
if (!EHAllocas.empty()) {
PromoteMemToReg(EHAllocas, *DT);
EHAllocas.clear();
}
// After promotion, some extracts may be trivially dead. Remove them.
SmallVector<Value *, 4> Users(LPad->user_begin(), LPad->user_end());
for (auto *U : Users)
RecursivelyDeleteTriviallyDeadInstructions(U);
}
void WinEHPrepare::getPossibleReturnTargets(Function *ParentF,
Function *HandlerF,
SetVector<BasicBlock*> &Targets) {
for (BasicBlock &BB : *HandlerF) {
// If the handler contains landing pads, check for any
// handlers that may return directly to a block in the
// parent function.
if (auto *LPI = BB.getLandingPadInst()) {
IntrinsicInst *Recover = cast<IntrinsicInst>(LPI->getNextNode());
SmallVector<std::unique_ptr<ActionHandler>, 4> ActionList;
parseEHActions(Recover, ActionList);
for (const auto &Action : ActionList) {
if (auto *CH = dyn_cast<CatchHandler>(Action.get())) {
Function *NestedF = cast<Function>(CH->getHandlerBlockOrFunc());
getPossibleReturnTargets(ParentF, NestedF, Targets);
}
}
}
auto *Ret = dyn_cast<ReturnInst>(BB.getTerminator());
if (!Ret)
continue;
// Handler functions must always return a block address.
BlockAddress *BA = cast<BlockAddress>(Ret->getReturnValue());
// If this is the handler for a nested landing pad, the
// return address may have been remapped to a block in the
// parent handler. We're not interested in those.
if (BA->getFunction() != ParentF)
continue;
Targets.insert(BA->getBasicBlock());
}
}
void WinEHPrepare::completeNestedLandingPad(Function *ParentFn,
LandingPadInst *OutlinedLPad,
const LandingPadInst *OriginalLPad,
FrameVarInfoMap &FrameVarInfo) {
// Get the nested block and erase the unreachable instruction that was
// temporarily inserted as its terminator.
LLVMContext &Context = ParentFn->getContext();
BasicBlock *OutlinedBB = OutlinedLPad->getParent();
assert(isa<UnreachableInst>(OutlinedBB->getTerminator()));
OutlinedBB->getTerminator()->eraseFromParent();
// That should leave OutlinedLPad as the last instruction in its block.
assert(&OutlinedBB->back() == OutlinedLPad);
// The original landing pad will have already had its action intrinsic
// built by the outlining loop. We need to clone that into the outlined
// location. It may also be necessary to add references to the exception
// variables to the outlined handler in which this landing pad is nested
// and remap return instructions in the nested handlers that should return
// to an address in the outlined handler.
Function *OutlinedHandlerFn = OutlinedBB->getParent();
BasicBlock::const_iterator II = OriginalLPad;
++II;
// The instruction after the landing pad should now be a call to eh.actions.
const Instruction *Recover = II;
assert(match(Recover, m_Intrinsic<Intrinsic::eh_actions>()));
IntrinsicInst *EHActions = cast<IntrinsicInst>(Recover->clone());
// Remap the exception variables into the outlined function.
SmallVector<BlockAddress *, 4> ActionTargets;
SmallVector<std::unique_ptr<ActionHandler>, 4> ActionList;
parseEHActions(EHActions, ActionList);
for (const auto &Action : ActionList) {
auto *Catch = dyn_cast<CatchHandler>(Action.get());
if (!Catch)
continue;
// The dyn_cast to function here selects C++ catch handlers and skips
// SEH catch handlers.
auto *Handler = dyn_cast<Function>(Catch->getHandlerBlockOrFunc());
if (!Handler)
continue;
// Visit all the return instructions, looking for places that return
// to a location within OutlinedHandlerFn.
for (BasicBlock &NestedHandlerBB : *Handler) {
auto *Ret = dyn_cast<ReturnInst>(NestedHandlerBB.getTerminator());
if (!Ret)
continue;
// Handler functions must always return a block address.
BlockAddress *BA = cast<BlockAddress>(Ret->getReturnValue());
// The original target will have been in the main parent function,
// but if it is the address of a block that has been outlined, it
// should be a block that was outlined into OutlinedHandlerFn.
assert(BA->getFunction() == ParentFn);
// Ignore targets that aren't part of OutlinedHandlerFn.
if (!LPadTargetBlocks.count(BA->getBasicBlock()))
continue;
// If the return value is the address ofF a block that we
// previously outlined into the parent handler function, replace
// the return instruction and add the mapped target to the list
// of possible return addresses.
BasicBlock *MappedBB = LPadTargetBlocks[BA->getBasicBlock()];
assert(MappedBB->getParent() == OutlinedHandlerFn);
BlockAddress *NewBA = BlockAddress::get(OutlinedHandlerFn, MappedBB);
Ret->eraseFromParent();
ReturnInst::Create(Context, NewBA, &NestedHandlerBB);
ActionTargets.push_back(NewBA);
}
}
ActionList.clear();
OutlinedBB->getInstList().push_back(EHActions);
// Insert an indirect branch into the outlined landing pad BB.
IndirectBrInst *IBr = IndirectBrInst::Create(EHActions, 0, OutlinedBB);
// Add the previously collected action targets.
for (auto *Target : ActionTargets)
IBr->addDestination(Target->getBasicBlock());
}
// 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;
}
static bool isCatchBlock(BasicBlock *BB) {
for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
II != IE; ++II) {
if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_begincatch>()))
return true;
}
return false;
}
static BasicBlock *createStubLandingPad(Function *Handler,
Value *PersonalityFn) {
// FIXME: Finish this!
LLVMContext &Context = Handler->getContext();
BasicBlock *StubBB = BasicBlock::Create(Context, "stub");
Handler->getBasicBlockList().push_back(StubBB);
IRBuilder<> Builder(StubBB);
LandingPadInst *LPad = Builder.CreateLandingPad(
llvm::StructType::get(Type::getInt8PtrTy(Context),
Type::getInt32Ty(Context), nullptr),
PersonalityFn, 0);
// Insert a call to llvm.eh.actions so that we don't try to outline this lpad.
Function *ActionIntrin =
Intrinsic::getDeclaration(Handler->getParent(), Intrinsic::eh_actions);
Builder.CreateCall(ActionIntrin, {}, "recover");
LPad->setCleanup(true);
Builder.CreateUnreachable();
return StubBB;
}
// Cycles through the blocks in an outlined handler function looking for an
// invoke instruction and inserts an invoke of llvm.donothing with an empty
// landing pad if none is found. The code that generates the .xdata tables for
// the handler needs at least one landing pad to identify the parent function's
// personality.
void WinEHPrepare::addStubInvokeToHandlerIfNeeded(Function *Handler,
Value *PersonalityFn) {
ReturnInst *Ret = nullptr;
UnreachableInst *Unreached = nullptr;
for (BasicBlock &BB : *Handler) {
TerminatorInst *Terminator = BB.getTerminator();
// If we find an invoke, there is nothing to be done.
auto *II = dyn_cast<InvokeInst>(Terminator);
if (II)
return;
// If we've already recorded a return instruction, keep looking for invokes.
if (!Ret)
Ret = dyn_cast<ReturnInst>(Terminator);
// If we haven't recorded an unreachable instruction, try this terminator.
if (!Unreached)
Unreached = dyn_cast<UnreachableInst>(Terminator);
}
// If we got this far, the handler contains no invokes. We should have seen
// at least one return or unreachable instruction. We'll insert an invoke of
// llvm.donothing ahead of that instruction.
assert(Ret || Unreached);
TerminatorInst *Term;
if (Ret)
Term = Ret;
else
Term = Unreached;
BasicBlock *OldRetBB = Term->getParent();
BasicBlock *NewRetBB = SplitBlock(OldRetBB, Term, DT);
// SplitBlock adds an unconditional branch instruction at the end of the
// parent block. We want to replace that with an invoke call, so we can
// erase it now.
OldRetBB->getTerminator()->eraseFromParent();
BasicBlock *StubLandingPad = createStubLandingPad(Handler, PersonalityFn);
Function *F =
Intrinsic::getDeclaration(Handler->getParent(), Intrinsic::donothing);
InvokeInst::Create(F, NewRetBB, StubLandingPad, None, "", OldRetBB);
}
// FIXME: Consider sinking this into lib/Target/X86 somehow. TargetLowering
// usually doesn't build LLVM IR, so that's probably the wrong place.
Function *WinEHPrepare::createHandlerFunc(Type *RetTy, const Twine &Name,
Module *M, Value *&ParentFP) {
// x64 uses a two-argument prototype where the parent FP is the second
// argument. x86 uses no arguments, just the incoming EBP value.
LLVMContext &Context = M->getContext();
FunctionType *FnType;
if (TheTriple.getArch() == Triple::x86_64) {
Type *Int8PtrType = Type::getInt8PtrTy(Context);
Type *ArgTys[2] = {Int8PtrType, Int8PtrType};
FnType = FunctionType::get(RetTy, ArgTys, false);
} else {
FnType = FunctionType::get(RetTy, None, false);
}
Function *Handler =
Function::Create(FnType, GlobalVariable::InternalLinkage, Name, M);
BasicBlock *Entry = BasicBlock::Create(Context, "entry");
Handler->getBasicBlockList().push_front(Entry);
if (TheTriple.getArch() == Triple::x86_64) {
ParentFP = &(Handler->getArgumentList().back());
} else {
assert(M);
Function *FrameAddressFn =
Intrinsic::getDeclaration(M, Intrinsic::frameaddress);
Value *Args[1] = {ConstantInt::get(Type::getInt32Ty(Context), 1)};
ParentFP = CallInst::Create(FrameAddressFn, Args, "parent_fp",
&Handler->getEntryBlock());
}
return Handler;
}
bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
LandingPadInst *LPad, BasicBlock *StartBB,
FrameVarInfoMap &VarInfo) {
Module *M = SrcFn->getParent();
LLVMContext &Context = M->getContext();
Type *Int8PtrType = Type::getInt8PtrTy(Context);
// Create a new function to receive the handler contents.
Value *ParentFP;
Function *Handler;
if (Action->getType() == Catch) {
Handler = createHandlerFunc(Int8PtrType, SrcFn->getName() + ".catch", M,
ParentFP);
} else {
Handler = createHandlerFunc(Type::getVoidTy(Context),
SrcFn->getName() + ".cleanup", M, ParentFP);
}
HandlerToParentFP[Handler] = ParentFP;
Handler->addFnAttr("wineh-parent", SrcFn->getName());
BasicBlock *Entry = &Handler->getEntryBlock();
// Generate a standard prolog to setup the frame recovery structure.
IRBuilder<> Builder(Context);
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 (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
Constant *Sel = CatchAction->getSelector();
Director.reset(new WinEHCatchDirector(Handler, ParentFP, Sel,
VarInfo, LPadMap,
NestedLPtoOriginalLP));
LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
ConstantInt::get(Type::getInt32Ty(Context), 1));
} else {
Director.reset(
new WinEHCleanupDirector(Handler, ParentFP, VarInfo, LPadMap));
LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
UndefValue::get(Type::getInt32Ty(Context)));
}
SmallVector<ReturnInst *, 8> Returns;
ClonedCodeInfo OutlinedFunctionInfo;
// If the start block contains PHI nodes, we need to map them.
BasicBlock::iterator II = StartBB->begin();
while (auto *PN = dyn_cast<PHINode>(II)) {
bool Mapped = false;
// Look for PHI values that we have already mapped (such as the selector).
for (Value *Val : PN->incoming_values()) {
if (VMap.count(Val)) {
VMap[PN] = VMap[Val];
Mapped = true;
}
}
// If we didn't find a match for this value, map it as an undef.
if (!Mapped) {
VMap[PN] = UndefValue::get(PN->getType());
}
++II;
}
// The landing pad value may be used by PHI nodes. It will ultimately be
// eliminated, but we need it in the map for intermediate handling.
VMap[LPad] = UndefValue::get(LPad->getType());
// Skip over PHIs and, if applicable, landingpad instructions.
II = StartBB->getFirstInsertionPt();
CloneAndPruneIntoFromInst(Handler, SrcFn, II, VMap,
/*ModuleLevelChanges=*/false, Returns, "",
&OutlinedFunctionInfo, Director.get());
// Move all the instructions in the cloned "entry" block into our entry block.
// Depending on how the parent function was laid out, the block that will
// correspond to the outlined entry block may not be the first block in the
// list. We can recognize it, however, as the cloned block which has no
// predecessors. Any other block wouldn't have been cloned if it didn't
// have a predecessor which was also cloned.
Function::iterator ClonedIt = std::next(Function::iterator(Entry));
while (!pred_empty(ClonedIt))
++ClonedIt;
BasicBlock *ClonedEntryBB = ClonedIt;
assert(ClonedEntryBB);
Entry->getInstList().splice(Entry->end(), ClonedEntryBB->getInstList());
ClonedEntryBB->eraseFromParent();
// Make sure we can identify the handler's personality later.
addStubInvokeToHandlerIfNeeded(Handler, LPad->getPersonalityFn());
if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
WinEHCatchDirector *CatchDirector =
reinterpret_cast<WinEHCatchDirector *>(Director.get());
CatchAction->setExceptionVar(CatchDirector->getExceptionVar());
CatchAction->setReturnTargets(CatchDirector->getReturnTargets());
// Look for blocks that are not part of the landing pad that we just
// outlined but terminate with a call to llvm.eh.endcatch and a
// branch to a block that is in the handler we just outlined.
// These blocks will be part of a nested landing pad that intends to
// return to an address in this handler. This case is best handled
// after both landing pads have been outlined, so for now we'll just
// save the association of the blocks in LPadTargetBlocks. The
// return instructions which are created from these branches will be
// replaced after all landing pads have been outlined.
for (const auto MapEntry : VMap) {
// VMap maps all values and blocks that were just cloned, but dead
// blocks which were pruned will map to nullptr.
if (!isa<BasicBlock>(MapEntry.first) || MapEntry.second == nullptr)
continue;
const BasicBlock *MappedBB = cast<BasicBlock>(MapEntry.first);
for (auto *Pred : predecessors(const_cast<BasicBlock *>(MappedBB))) {
auto *Branch = dyn_cast<BranchInst>(Pred->getTerminator());
if (!Branch || !Branch->isUnconditional() || Pred->size() <= 1)
continue;
BasicBlock::iterator II = const_cast<BranchInst *>(Branch);
--II;
if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_endcatch>())) {
// This would indicate that a nested landing pad wants to return
// to a block that is outlined into two different handlers.
assert(!LPadTargetBlocks.count(MappedBB));
LPadTargetBlocks[MappedBB] = cast<BasicBlock>(MapEntry.second);
}
}
}
} // End if (CatchAction)
Action->setHandlerBlockOrFunc(Handler);
return true;
}
/// This BB must end in a selector dispatch. All we need to do is pass the
/// handler block to llvm.eh.actions and list it as a possible indirectbr
/// target.
void WinEHPrepare::processSEHCatchHandler(CatchHandler *CatchAction,
BasicBlock *StartBB) {
BasicBlock *HandlerBB;
BasicBlock *NextBB;
Constant *Selector;
bool Res = isSelectorDispatch(StartBB, HandlerBB, Selector, NextBB);
if (Res) {
// If this was EH dispatch, this must be a conditional branch to the handler
// block.
// FIXME: Handle instructions in the dispatch block. Currently we drop them,
// leading to crashes if some optimization hoists stuff here.
assert(CatchAction->getSelector() && HandlerBB &&
"expected catch EH dispatch");
} else {
// This must be a catch-all. Split the block after the landingpad.
assert(CatchAction->getSelector()->isNullValue() && "expected catch-all");
HandlerBB = SplitBlock(StartBB, StartBB->getFirstInsertionPt(), DT);
}
IRBuilder<> Builder(HandlerBB->getFirstInsertionPt());
Function *EHCodeFn = Intrinsic::getDeclaration(
StartBB->getParent()->getParent(), Intrinsic::eh_exceptioncode);
Value *Code = Builder.CreateCall(EHCodeFn, {}, "sehcode");
Code = Builder.CreateIntToPtr(Code, SEHExceptionCodeSlot->getAllocatedType());
Builder.CreateStore(Code, SEHExceptionCodeSlot);
CatchAction->setHandlerBlockOrFunc(BlockAddress::get(HandlerBB));
TinyPtrVector<BasicBlock *> Targets(HandlerBB);
CatchAction->setReturnTargets(Targets);
}
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 will have been promoted to reg values before
// this routine is called.
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) {
ExtractedEHPtrs.push_back(Extract);
} else if (Idx == 1) {
ExtractedSelectors.push_back(Extract);
}
}
}
bool LandingPadMap::isOriginLandingPadBlock(const BasicBlock *BB) const {
return BB->getLandingPadInst() == OriginLPad;
}
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;
}
return false;
}
void LandingPadMap::remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
Value *SelectorValue) const {
// Remap all landing pad extract instructions to the specified values.
for (auto *Extract : ExtractedEHPtrs)
VMap[Extract] = EHPtrValue;
for (auto *Extract : ExtractedSelectors)
VMap[Extract] = SelectorValue;
}
static bool isFrameAddressCall(const Value *V) {
return match(const_cast<Value *>(V),
m_Intrinsic<Intrinsic::frameaddress>(m_SpecificInt(0)));
}
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;
// 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 *LPad = dyn_cast<LandingPadInst>(Inst)) {
return handleLandingPad(VMap, LPad, NewBB);
}
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 (auto *Cmp = dyn_cast<CmpInst>(Inst))
return handleCompare(VMap, Cmp, 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);
// When outlining llvm.frameaddress(i32 0), remap that to the second argument,
// which is the FP of the parent.
if (isFrameAddressCall(Inst)) {
VMap[Inst] = ParentFP;
return CloningDirector::SkipInstruction;
}
// Continue with the default cloning behavior.
return CloningDirector::CloneInstruction;
}
CloningDirector::CloningAction WinEHCatchDirector::handleLandingPad(
ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
Instruction *NewInst = LPad->clone();
if (LPad->hasName())
NewInst->setName(LPad->getName());
// Save this correlation for later processing.
NestedLPtoOriginalLP[cast<LandingPadInst>(NewInst)] = LPad;
VMap[LPad] = NewInst;
BasicBlock::InstListType &InstList = NewBB->getInstList();
InstList.push_back(NewInst);
InstList.push_back(new UnreachableInst(NewBB->getContext()));
return CloningDirector::StopCloningBB;
}
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();
if (isa<ConstantPointerNull>(ExceptionObjectVar))
return CloningDirector::SkipInstruction;
assert(cast<AllocaInst>(ExceptionObjectVar)->isStaticAlloca() &&
"catch parameter is not static alloca");
Materializer.escapeCatchObject(ExceptionObjectVar);
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. However, a catch-all handler may call
// end catch from the original landing pad. If the call occurs in a nested
// landing pad block, we must skip it and continue so that the landing pad
// gets cloned.
auto *ParentBB = IntrinCall->getParent();
if (ParentBB->isLandingPad() && !LPadMap.isOriginLandingPadBlock(ParentBB))
return CloningDirector::SkipInstruction;
// If an end catch occurs anywhere else we want to terminate the handler
// with a return to the code that follows the endcatch call. If the
// next instruction is not an unconditional branch, we need to split the
// block to provide a clear target for the return instruction.
BasicBlock *ContinueBB;
auto Next = std::next(BasicBlock::const_iterator(IntrinCall));
const BranchInst *Branch = dyn_cast<BranchInst>(Next);
if (!Branch || !Branch->isUnconditional()) {
// We're interrupting the cloning process at this location, so the
// const_cast we're doing here will not cause a problem.
ContinueBB = SplitBlock(const_cast<BasicBlock *>(ParentBB),
const_cast<Instruction *>(cast<Instruction>(Next)));
} else {
ContinueBB = Branch->getSuccessor(0);
}
ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueBB), NewBB);
ReturnTargets.push_back(ContinueBB);
// 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
WinEHCatchDirector::handleCompare(ValueToValueMapTy &VMap,
const CmpInst *Compare, BasicBlock *NewBB) {
const IntrinsicInst *IntrinCall = nullptr;
if (match(Compare->getOperand(0), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
IntrinCall = dyn_cast<IntrinsicInst>(Compare->getOperand(0));
} else if (match(Compare->getOperand(1),
m_Intrinsic<Intrinsic::eh_typeid_for>())) {
IntrinCall = dyn_cast<IntrinsicInst>(Compare->getOperand(1));
}
if (IntrinCall) {
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->stripPointerCasts()) {
VMap[Compare] = ConstantInt::get(SelectorIDType, 1);
} else {
VMap[Compare] = ConstantInt::get(SelectorIDType, 0);
}
return CloningDirector::SkipInstruction;
}
return CloningDirector::CloneInstruction;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleLandingPad(
ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
// The MS runtime will terminate the process if an exception occurs in a
// cleanup handler, so we shouldn't encounter landing pads in the actual
// cleanup code, but they may appear in catch blocks. Depending on where
// we started cloning we may see one, but it will get dropped during dead
// block pruning.
Instruction *NewInst = new UnreachableInst(NewBB->getContext());
VMap[LPad] = NewInst;
BasicBlock::InstListType &InstList = NewBB->getInstList();
InstList.push_back(NewInst);
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleBeginCatch(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
// Cleanup code may flow into catch blocks or the catch block may be part
// of a branch that will be optimized away. We'll insert a return
// instruction now, but it may be pruned before the cloning process is
// complete.
ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleEndCatch(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
// Cleanup handlers nested within catch handlers may begin with a call to
// eh.endcatch. We can just ignore that instruction.
return CloningDirector::SkipInstruction;
}
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;
// Remap the operands.
llvm::RemapInstruction(NewCall, VMap, RF_None, nullptr, &Materializer);
// 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::CloneSuccessors;
}
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;
}
CloningDirector::CloningAction
WinEHCleanupDirector::handleCompare(ValueToValueMapTy &VMap,
const CmpInst *Compare, BasicBlock *NewBB) {
if (match(Compare->getOperand(0), m_Intrinsic<Intrinsic::eh_typeid_for>()) ||
match(Compare->getOperand(1), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
VMap[Compare] = ConstantInt::get(SelectorIDType, 1);
return CloningDirector::SkipInstruction;
}
return CloningDirector::CloneInstruction;
}
WinEHFrameVariableMaterializer::WinEHFrameVariableMaterializer(
Function *OutlinedFn, Value *ParentFP, FrameVarInfoMap &FrameVarInfo)
: FrameVarInfo(FrameVarInfo), Builder(OutlinedFn->getContext()) {
BasicBlock *EntryBB = &OutlinedFn->getEntryBlock();
// New allocas should be inserted in the entry block, but after the parent FP
// is established if it is an instruction.
Instruction *InsertPoint = EntryBB->getFirstInsertionPt();
if (auto *FPInst = dyn_cast<Instruction>(ParentFP))
InsertPoint = FPInst->getNextNode();
Builder.SetInsertPoint(EntryBB, InsertPoint);
}
Value *WinEHFrameVariableMaterializer::materializeValueFor(Value *V) {
// If we're asked to materialize a static alloca, we temporarily create an
// alloca in the outlined function and add this to the FrameVarInfo map. When
// all the outlining is complete, we'll replace these temporary allocas with
// calls to llvm.framerecover.
if (auto *AV = dyn_cast<AllocaInst>(V)) {
assert(AV->isStaticAlloca() &&
"cannot materialize un-demoted dynamic alloca");
AllocaInst *NewAlloca = dyn_cast<AllocaInst>(AV->clone());
Builder.Insert(NewAlloca, AV->getName());
FrameVarInfo[AV].push_back(NewAlloca);
return NewAlloca;
}
if (isa<Instruction>(V) || isa<Argument>(V)) {
Function *Parent = isa<Instruction>(V)
? cast<Instruction>(V)->getParent()->getParent()
: cast<Argument>(V)->getParent();
errs()
<< "Failed to demote instruction used in exception handler of function "
<< GlobalValue::getRealLinkageName(Parent->getName()) << ":\n";
errs() << " " << *V << '\n';
report_fatal_error("WinEHPrepare failed to demote instruction");
}
// Don't materialize other values.
return nullptr;
}
void WinEHFrameVariableMaterializer::escapeCatchObject(Value *V) {
// Catch parameter objects have to live in the parent frame. When we see a use
// of a catch parameter, add a sentinel to the multimap to indicate that it's
// used from another handler. This will prevent us from trying to sink the
// alloca into the handler and ensure that the catch parameter is present in
// the call to llvm.frameescape.
FrameVarInfo[V].push_back(getCatchObjectSentinel());
}
// 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) {
findCleanupHandlers(Actions, BB, nullptr);
return;
}
VisitedBlockSet VisitedBlocks;
while (HandlersFound != NumClauses) {
BasicBlock *NextBB = nullptr;
// Skip over filter clauses.
if (LPad->isFilter(HandlersFound)) {
++HandlersFound;
continue;
}
// See if the clause we're looking for is a catch-all.
// If so, the catch begins immediately.
Constant *ExpectedSelector =
LPad->getClause(HandlersFound)->stripPointerCasts();
if (isa<ConstantPointerNull>(ExpectedSelector)) {
// The catch all must occur last.
assert(HandlersFound == NumClauses - 1);
// There can be additional selector dispatches in the call chain that we
// need to ignore.
BasicBlock *CatchBlock = nullptr;
Constant *Selector;
while (BB && isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
DEBUG(dbgs() << " Found extra catch dispatch in block "
<< CatchBlock->getName() << "\n");
BB = NextBB;
}
// Add the catch handler to the action list.
CatchHandler *Action = nullptr;
if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
// If the CatchHandlerMap already has an entry for this BB, re-use it.
Action = CatchHandlerMap[BB];
assert(Action->getSelector() == ExpectedSelector);
} else {
// We don't expect a selector dispatch, but there may be a call to
// llvm.eh.begincatch, which separates catch handling code from
// cleanup code in the same control flow. This call looks for the
// begincatch intrinsic.
Action = findCatchHandler(BB, NextBB, VisitedBlocks);
if (Action) {
// For C++ EH, check if there is any interesting cleanup code before
// we begin the catch. This is important because cleanups cannot
// rethrow exceptions but code called from catches can. For SEH, it
// isn't important if some finally code before a catch-all is executed
// out of line or after recovering from the exception.
if (Personality == EHPersonality::MSVC_CXX)
findCleanupHandlers(Actions, BB, BB);
} else {
// If an action was not found, it means that the control flows
// directly into the catch-all handler and there is no cleanup code.
// That's an expected situation and we must create a catch action.
// Since this is a catch-all handler, the selector won't actually
// appear in the code anywhere. ExpectedSelector here is the constant
// null ptr that we got from the landing pad instruction.
Action = new CatchHandler(BB, ExpectedSelector, nullptr);
CatchHandlerMap[BB] = Action;
}
}
Actions.insertCatchHandler(Action);
DEBUG(dbgs() << " Catch all handler at block " << BB->getName() << "\n");
++HandlersFound;
// Once we reach a catch-all, don't expect to hit a resume instruction.
BB = nullptr;
break;
}
CatchHandler *CatchAction = findCatchHandler(BB, NextBB, VisitedBlocks);
assert(CatchAction);
// See if there is any interesting code executed before the dispatch.
findCleanupHandlers(Actions, BB, CatchAction->getStartBlock());
// When the source program contains multiple nested try blocks the catch
// handlers can get strung together in such a way that we can encounter
// a dispatch for a selector that we've already had a handler for.
if (CatchAction->getSelector()->stripPointerCasts() == ExpectedSelector) {
++HandlersFound;
// Add the catch handler to the action list.
DEBUG(dbgs() << " Found catch dispatch in block "
<< CatchAction->getStartBlock()->getName() << "\n");
Actions.insertCatchHandler(CatchAction);
} else {
// Under some circumstances optimized IR will flow unconditionally into a
// handler block without checking the selector. This can only happen if
// the landing pad has a catch-all handler and the handler for the
// preceeding catch clause is identical to the catch-call handler
// (typically an empty catch). In this case, the handler must be shared
// by all remaining clauses.
if (isa<ConstantPointerNull>(
CatchAction->getSelector()->stripPointerCasts())) {
DEBUG(dbgs() << " Applying early catch-all handler in block "
<< CatchAction->getStartBlock()->getName()
<< " to all remaining clauses.\n");
Actions.insertCatchHandler(CatchAction);
return;
}
DEBUG(dbgs() << " Found extra catch dispatch in block "
<< CatchAction->getStartBlock()->getName() << "\n");
}
// Move on to the block after the catch handler.
BB = NextBB;
}
// If we didn't wind up in a catch-all, see if there is any interesting code
// executed before the resume.
findCleanupHandlers(Actions, BB, BB);
// 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;
}
// If we encounter a block containing an llvm.eh.begincatch before we
// find a selector dispatch block, the handler is assumed to be
// reached unconditionally. This happens for catch-all blocks, but
// it can also happen for other catch handlers that have been combined
// with the catch-all handler during optimization.
if (isCatchBlock(BB)) {
PointerType *Int8PtrTy = Type::getInt8PtrTy(BB->getContext());
Constant *NullSelector = ConstantPointerNull::get(Int8PtrTy);
CatchHandler *Action = new CatchHandler(BB, NullSelector, nullptr);
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 findCleanupHandlers.
static void createCleanupHandler(LandingPadActions &Actions,
CleanupHandlerMapTy &CleanupHandlerMap,
BasicBlock *BB) {
CleanupHandler *Action = new CleanupHandler(BB);
CleanupHandlerMap[BB] = Action;
Actions.insertCleanupHandler(Action);
DEBUG(dbgs() << " Found cleanup code in block "
<< Action->getStartBlock()->getName() << "\n");
}
static CallSite matchOutlinedFinallyCall(BasicBlock *BB,
Instruction *MaybeCall) {
// Look for finally blocks that Clang has already outlined for us.
// %fp = call i8* @llvm.frameaddress(i32 0)
// call void @"fin$parent"(iN 1, i8* %fp)
if (isFrameAddressCall(MaybeCall) && MaybeCall != BB->getTerminator())
MaybeCall = MaybeCall->getNextNode();
CallSite FinallyCall(MaybeCall);
if (!FinallyCall || FinallyCall.arg_size() != 2)
return CallSite();
if (!match(FinallyCall.getArgument(0), m_SpecificInt(1)))
return CallSite();
if (!isFrameAddressCall(FinallyCall.getArgument(1)))
return CallSite();
return FinallyCall;
}
static BasicBlock *followSingleUnconditionalBranches(BasicBlock *BB) {
// Skip single ubr blocks.
while (BB->getFirstNonPHIOrDbg() == BB->getTerminator()) {
auto *Br = dyn_cast<BranchInst>(BB->getTerminator());
if (Br && Br->isUnconditional())
BB = Br->getSuccessor(0);
else
return BB;
}
return BB;
}
// 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.
//
void WinEHPrepare::findCleanupHandlers(LandingPadActions &Actions,
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) {
BB = followSingleUnconditionalBranches(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]) {
Actions.insertCleanupHandler(Action);
DEBUG(dbgs() << " Found cleanup code in block "
<< Action->getStartBlock()->getName() << "\n");
// FIXME: This cleanup might chain into another, and we need to discover
// that.
return;
} 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.
BasicBlock *SuccBB = followSingleUnconditionalBranches(BB);
if (SuccBB == BB || SuccBB == EndBB)
return;
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:
// %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn, 0
// %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel, 1
// resume { i8*, i32 } %lpad.val2
if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
InsertValueInst *Insert1 = nullptr;
InsertValueInst *Insert2 = nullptr;
Value *ResumeVal = Resume->getOperand(0);
// If the resume value isn't a phi or landingpad value, it should be a
// series of insertions. Identify them so we can avoid them when scanning
// for cleanups.
if (!isa<PHINode>(ResumeVal) && !isa<LandingPadInst>(ResumeVal)) {
Insert2 = dyn_cast<InsertValueInst>(ResumeVal);
if (!Insert2)
return createCleanupHandler(Actions, CleanupHandlerMap, BB);
Insert1 = dyn_cast<InsertValueInst>(Insert2->getAggregateOperand());
if (!Insert1)
return createCleanupHandler(Actions, 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(Actions, CleanupHandlerMap, BB);
}
}
return;
}
BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
if (Branch && Branch->isConditional()) {
// Look for the selector dispatch.
// %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
// %matches = icmp eq i32 %sel, %2
// br i1 %matches, label %catch14, label %eh.resume
CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
if (!Compare || !Compare->isEquality())
return createCleanupHandler(Actions, 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 (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
continue;
return createCleanupHandler(Actions, CleanupHandlerMap, BB);
}
// The selector dispatch block should always terminate our search.
assert(BB == EndBB);
return;
}
if (isAsynchronousEHPersonality(Personality)) {
// If this is a landingpad block, split the block at the first non-landing
// pad instruction.
Instruction *MaybeCall = BB->getFirstNonPHIOrDbg();
if (LPadMap) {
while (MaybeCall != BB->getTerminator() &&
LPadMap->isLandingPadSpecificInst(MaybeCall))
MaybeCall = MaybeCall->getNextNode();
}
// Look for outlined finally calls.
if (CallSite FinallyCall = matchOutlinedFinallyCall(BB, MaybeCall)) {
Function *Fin = FinallyCall.getCalledFunction();
assert(Fin && "outlined finally call should be direct");
auto *Action = new CleanupHandler(BB);
Action->setHandlerBlockOrFunc(Fin);
Actions.insertCleanupHandler(Action);
CleanupHandlerMap[BB] = Action;
DEBUG(dbgs() << " Found frontend-outlined finally call to "
<< Fin->getName() << " in block "
<< Action->getStartBlock()->getName() << "\n");
// Split the block if there were more interesting instructions and look
// for finally calls in the normal successor block.
BasicBlock *SuccBB = BB;
if (FinallyCall.getInstruction() != BB->getTerminator() &&
FinallyCall.getInstruction()->getNextNode() !=
BB->getTerminator()) {
SuccBB =
SplitBlock(BB, FinallyCall.getInstruction()->getNextNode(), DT);
} else {
if (FinallyCall.isInvoke()) {
SuccBB =
cast<InvokeInst>(FinallyCall.getInstruction())->getNormalDest();
} else {
SuccBB = BB->getUniqueSuccessor();
assert(SuccBB &&
"splitOutlinedFinallyCalls didn't insert a branch");
}
}
BB = SuccBB;
if (BB == EndBB)
return;
continue;
}
}
// Anything else is either a catch block or interesting cleanup code.
for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
II != IE; ++II) {
Instruction *Inst = II;
if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
continue;
// Unconditional branches fall through to this loop.
if (Inst == Branch)
continue;
// If this is a catch block, there is no cleanup code to be found.
if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
return;
// If this a nested landing pad, it may contain an endcatch call.
if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
return;
// Anything else makes this interesting cleanup code.
return createCleanupHandler(Actions, CleanupHandlerMap, BB);
}
// Only unconditional branches in empty blocks should get this far.
assert(Branch && Branch->isUnconditional());
if (BB == EndBB)
return;
BB = Branch->getSuccessor(0);
}
}
// This is a public function, declared in WinEHFuncInfo.h and is also
// referenced by WinEHNumbering in FunctionLoweringInfo.cpp.
void llvm::parseEHActions(
const IntrinsicInst *II,
SmallVectorImpl<std::unique_ptr<ActionHandler>> &Actions) {
for (unsigned I = 0, E = II->getNumArgOperands(); I != E;) {
uint64_t ActionKind =
cast<ConstantInt>(II->getArgOperand(I))->getZExtValue();
if (ActionKind == /*catch=*/1) {
auto *Selector = cast<Constant>(II->getArgOperand(I + 1));
ConstantInt *EHObjIndex = cast<ConstantInt>(II->getArgOperand(I + 2));
int64_t EHObjIndexVal = EHObjIndex->getSExtValue();
Constant *Handler = cast<Constant>(II->getArgOperand(I + 3));
I += 4;
auto CH = make_unique<CatchHandler>(/*BB=*/nullptr, Selector,
/*NextBB=*/nullptr);
CH->setHandlerBlockOrFunc(Handler);
CH->setExceptionVarIndex(EHObjIndexVal);
Actions.push_back(std::move(CH));
} else if (ActionKind == 0) {
Constant *Handler = cast<Constant>(II->getArgOperand(I + 1));
I += 2;
auto CH = make_unique<CleanupHandler>(/*BB=*/nullptr);
CH->setHandlerBlockOrFunc(Handler);
Actions.push_back(std::move(CH));
} else {
llvm_unreachable("Expected either a catch or cleanup handler!");
}
}
std::reverse(Actions.begin(), Actions.end());
}
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