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ccf132c096
llvm-mirror/lib/CodeGen/WinEHPrepare.cpp
David Majnemer ccf132c096 [WinEH] Create a separate MBB for funclet prologues 
Our current emission strategy is to emit the funclet prologue in the
CatchPad's normal destination.  This is problematic because
intra-funclet control flow to the normal destination is not erroneous
and results in us reevaluating the prologue if said control flow is
taken.

Instead, use the CatchPad's location for the funclet prologue.  This
correctly models our desire to have unwind edges evaluate the prologue
but edges to the normal destination result in typical control flow.

Differential Revision: http://reviews.llvm.org/D13424

llvm-svn: 249483
2015-10-06 23:31:59 +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 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/CFG.h"
#include "llvm/Analysis/LibCallSemantics.h"
#include "llvm/Analysis/TargetLibraryInfo.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/MC/MCSymbol.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#include <memory>
using namespace llvm;
using namespace llvm::PatternMatch;
#define DEBUG_TYPE "winehprepare"
static cl::opt<bool> DisableDemotion(
"disable-demotion", cl::Hidden,
cl::desc(
"Clone multicolor basic blocks but do not demote cross funclet values"),
cl::init(false));
static cl::opt<bool> DisableCleanups(
"disable-cleanups", cl::Hidden,
cl::desc("Do not remove implausible terminators or other similar cleanups"),
cl::init(false));
namespace {
// 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 = 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 identifyEHBlocks(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(Function *ParentFn, 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);
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);
void insertPHIStores(PHINode *OriginalPHI, AllocaInst *SpillSlot);
void
insertPHIStore(BasicBlock *PredBlock, Value *PredVal, AllocaInst *SpillSlot,
SmallVectorImpl<std::pair<BasicBlock *, Value *>> &Worklist);
AllocaInst *insertPHILoads(PHINode *PN, Function &F);
void replaceUseWithLoad(Value *V, Use &U, AllocaInst *&SpillSlot,
DenseMap<BasicBlock *, Value *> &Loads, Function &F);
void demoteNonlocalUses(Value *V, std::set<BasicBlock *> &ColorsForBB,
Function &F);
bool prepareExplicitEH(Function &F,
SmallVectorImpl<BasicBlock *> &EntryBlocks);
void replaceTerminatePadWithCleanup(Function &F);
void colorFunclets(Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks);
void demotePHIsOnFunclets(Function &F);
void demoteUsesBetweenFunclets(Function &F);
void demoteArgumentUses(Function &F);
void cloneCommonBlocks(Function &F,
SmallVectorImpl<BasicBlock *> &EntryBlocks);
void removeImplausibleTerminators(Function &F);
void cleanupPreparedFunclets(Function &F);
void verifyPreparedFunclets(Function &F);
Triple TheTriple;
// All fields are reset by runOnFunction.
DominatorTree *DT = nullptr;
const TargetLibraryInfo *LibInfo = nullptr;
EHPersonality Personality = EHPersonality::Unknown;
CatchHandlerMapTy CatchHandlerMap;
CleanupHandlerMapTy CleanupHandlerMap;
DenseMap<const LandingPadInst *, LandingPadMap> LPadMaps;
SmallPtrSet<BasicBlock *, 4> NormalBlocks;
SmallPtrSet<BasicBlock *, 4> EHBlocks;
SetVector<BasicBlock *> EHReturnBlocks;
// 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 parent local address. Only used for
// 32-bit EH.
DenseMap<Function *, Value *> HandlerToParentFP;
AllocaInst *SEHExceptionCodeSlot = nullptr;
std::map<BasicBlock *, std::set<BasicBlock *>> BlockColors;
std::map<BasicBlock *, std::set<BasicBlock *>> FuncletBlocks;
std::map<BasicBlock *, std::set<BasicBlock *>> FuncletChildren;
};
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 handleIndirectBr(ValueToValueMapTy &VMap,
const IndirectBrInst *IBr,
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,
DominatorTree *DT, SmallPtrSetImpl<BasicBlock *> &EHBlocks)
: WinEHCloningDirectorBase(CatchFn, ParentFP, VarInfo, LPadMap),
CurrentSelector(Selector->stripPointerCasts()),
ExceptionObjectVar(nullptr), NestedLPtoOriginalLP(NestedLPads),
DT(DT), EHBlocks(EHBlocks) {}
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 handleIndirectBr(ValueToValueMapTy &VMap,
const IndirectBrInst *IBr,
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;
DominatorTree *DT;
SmallPtrSetImpl<BasicBlock *> &EHBlocks;
};
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 handleIndirectBr(ValueToValueMapTy &VMap,
const IndirectBrInst *IBr,
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);
}
static bool
findExceptionalConstructs(Function &Fn,
SmallVectorImpl<LandingPadInst *> &LPads,
SmallVectorImpl<ResumeInst *> &Resumes,
SmallVectorImpl<BasicBlock *> &EntryBlocks) {
bool ForExplicitEH = false;
for (BasicBlock &BB : Fn) {
Instruction *First = BB.getFirstNonPHI();
if (auto *LP = dyn_cast<LandingPadInst>(First)) {
LPads.push_back(LP);
} else if (First->isEHPad()) {
if (!ForExplicitEH)
EntryBlocks.push_back(&Fn.getEntryBlock());
if (!isa<CatchEndPadInst>(First) && !isa<CleanupEndPadInst>(First))
EntryBlocks.push_back(&BB);
ForExplicitEH = true;
}
if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
Resumes.push_back(Resume);
}
return ForExplicitEH;
}
bool WinEHPrepare::runOnFunction(Function &Fn) {
if (!Fn.hasPersonalityFn())
return false;
// No need to prepare outlined handlers.
if (Fn.hasFnAttribute("wineh-parent"))
return false;
// Classify the personality to see what kind of preparation we need.
Personality = classifyEHPersonality(Fn.getPersonalityFn());
// Do nothing if this is not a funclet-based personality.
if (!isFuncletEHPersonality(Personality))
return false;
SmallVector<LandingPadInst *, 4> LPads;
SmallVector<ResumeInst *, 4> Resumes;
SmallVector<BasicBlock *, 4> EntryBlocks;
bool ForExplicitEH =
findExceptionalConstructs(Fn, LPads, Resumes, EntryBlocks);
if (ForExplicitEH)
return prepareExplicitEH(Fn, EntryBlocks);
// No need to prepare functions that lack landing pads.
if (LPads.empty())
return false;
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
LibInfo = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
// 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>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
}
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 are multiple predecessors. This creates a place
// where we can insert EH recovery code.
if (!CatchHandler->getSinglePredecessor()) {
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);
}
}
}
void WinEHPrepare::identifyEHBlocks(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.
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.
SetVector<BasicBlock *> Worklist;
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';
});
}
/// 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');
// identifyEHBlocks() should have been called before this function.
assert(!NormalBlocks.empty());
// Try to avoid demoting EH pointer and selector values. They get in the way
// of our pattern matching.
SmallPtrSet<Instruction *, 10> EHVals;
for (BasicBlock &BB : F) {
LandingPadInst *LP = BB.getLandingPadInst();
if (!LP)
continue;
EHVals.insert(LP);
for (User *U : LP->users()) {
auto *EI = dyn_cast<ExtractValueInst>(U);
if (!EI)
continue;
EHVals.insert(EI);
for (User *U2 : EI->users()) {
if (auto *PN = dyn_cast<PHINode>(U2))
EHVals.insert(PN);
}
}
}
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;
}
// Don't demote EH values.
auto *OpI = cast<Instruction>(Op);
if (EHVals.count(OpI))
continue;
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;
}
identifyEHBlocks(F, LPads);
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());
}
// In order to handle the case where one outlined catch handler returns
// to a block within another outlined catch handler that would otherwise
// be unreachable, we need to outline the nested landing pad before we
// outline the landing pad which encloses it.
if (!isAsynchronousEHPersonality(Personality))
std::sort(LPads.begin(), LPads.end(),
[this](LandingPadInst *const &L, LandingPadInst *const &R) {
return DT->properlyDominates(R->getParent(), L->getParent());
});
// 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.
while (!SEHCodeUses.empty()) {
Instruction *E = SEHCodeUses.pop_back_val();
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;
if (auto *Phi = dyn_cast<PHINode>(I))
SEHCodeUses.push_back(Phi);
else
U->set(new LoadInst(SEHExceptionCodeSlot, "sehcode", false, I));
}
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);
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);
if (!isAsynchronousEHPersonality(Personality)) {
// C++ EH must repopulate the targets later to handle the case of
// targets that are reached indirectly through nested landing pads.
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();
// Update the indirectbr instructions' target lists if necessary.
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();
// Clear any targets we already knew about.
for (unsigned int I = 0, E = Branch->getNumDestinations(); I < E; ++I) {
BasicBlock *KnownTarget = Branch->getDestination(I);
if (ReturnTargets.count(KnownTarget))
ReturnTargets.remove(KnownTarget);
}
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::localescape);
Function *RecoverFrameFn =
Intrinsic::getDeclaration(M, Intrinsic::localrecover);
SmallVector<Value *, 8> AllocasToEscape;
// Scan the entry block for an existing call to llvm.localescape. We need to
// keep escaping those objects.
for (Instruction &I : F.front()) {
auto *II = dyn_cast<IntrinsicInst>(&I);
if (II && II->getIntrinsicID() == Intrinsic::localescape) {
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.localrecover.
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 localrecover 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.localescape(...)' at the end of the entry
// block.
Builder.SetInsertPoint(&F.getEntryBlock().back());
Builder.CreateCall(FrameEscapeFn, AllocasToEscape);
if (SEHExceptionCodeSlot) {
if (isAllocaPromotable(SEHExceptionCodeSlot)) {
SmallPtrSet<BasicBlock *, 4> UserBlocks;
for (User *U : SEHExceptionCodeSlot->users()) {
if (auto *Inst = dyn_cast<Instruction>(U))
UserBlocks.insert(Inst->getParent());
}
PromoteMemToReg(SEHExceptionCodeSlot, *DT);
// After the promotion, kill off dead instructions.
for (BasicBlock *BB : UserBlocks)
SimplifyInstructionsInBlock(BB, LibInfo);
}
}
// Clean up the handler action maps we created for this function
DeleteContainerSeconds(CatchHandlerMap);
CatchHandlerMap.clear();
DeleteContainerSeconds(CleanupHandlerMap);
CleanupHandlerMap.clear();
HandlerToParentFP.clear();
DT = nullptr;
LibInfo = nullptr;
SEHExceptionCodeSlot = nullptr;
EHBlocks.clear();
NormalBlocks.clear();
EHReturnBlocks.clear();
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();
// If the nested landing pad was outlined before the landing pad that enclosed
// it, it will already be in outlined form. In that case, we just need to see
// if the returns and the enclosing branch instruction need to be updated.
IndirectBrInst *Branch =
dyn_cast<IndirectBrInst>(OutlinedBB->getTerminator());
if (!Branch) {
// If the landing pad wasn't in outlined form, it should be a stub with
// an unreachable terminator.
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;
const IntrinsicInst *EHActions = cast<IntrinsicInst>(Recover);
// Remap the return target in the nested handler.
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 an outlined handler function.
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();
if (Branch) {
// If the landing pad was already in outlined form, just update its targets.
for (unsigned int I = Branch->getNumDestinations(); I > 0; --I)
Branch->removeDestination(I);
// Add the previously collected action targets.
for (auto *Target : ActionTargets)
Branch->addDestination(Target->getBasicBlock());
} else {
// If the landing pad was previously stubbed out, fill in its outlined form.
IntrinsicInst *NewEHActions = cast<IntrinsicInst>(EHActions->clone());
OutlinedBB->getInstList().push_back(NewEHActions);
// Insert an indirect branch into the outlined landing pad BB.
IndirectBrInst *IBr = IndirectBrInst::Create(NewEHActions, 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) {
// 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),
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) {
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);
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(Function *ParentFn, 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();
Type *Int8PtrType = Type::getInt8PtrTy(Context);
FunctionType *FnType;
if (TheTriple.getArch() == Triple::x86_64) {
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);
Function *RecoverFPFn =
Intrinsic::getDeclaration(M, Intrinsic::x86_seh_recoverfp);
IRBuilder<> Builder(&Handler->getEntryBlock());
Value *EBP =
Builder.CreateCall(FrameAddressFn, {Builder.getInt32(1)}, "ebp");
Value *ParentI8Fn = Builder.CreateBitCast(ParentFn, Int8PtrType);
ParentFP = Builder.CreateCall(RecoverFPFn, {ParentI8Fn, EBP});
}
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(SrcFn, Int8PtrType, SrcFn->getName() + ".catch", M,
ParentFP);
} else {
Handler = createHandlerFunc(SrcFn, Type::getVoidTy(Context),
SrcFn->getName() + ".cleanup", M, ParentFP);
}
Handler->setPersonalityFn(SrcFn->getPersonalityFn());
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, DT,
EHBlocks));
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);
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 isLocalAddressCall(const Value *V) {
return match(const_cast<Value *>(V), m_Intrinsic<Intrinsic::localaddress>());
}
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 that have not already been outlined 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);
}
// Nested landing pads that have already been outlined will be cloned in their
// outlined form, but we need to intercept the ibr instruction to filter out
// targets that do not return to the handler we are outlining.
if (auto *IBr = dyn_cast<IndirectBrInst>(Inst)) {
return handleIndirectBr(VMap, IBr, 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.localaddress(), remap that to the second argument,
// which is the FP of the parent.
if (isLocalAddressCall(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) {
// If the instruction after the landing pad is a call to llvm.eh.actions
// the landing pad has already been outlined. In this case, we should
// clone it because it may return to a block in the handler we are
// outlining now that would otherwise be unreachable. The landing pads
// are sorted before outlining begins to enable this case to work
// properly.
const Instruction *NextI = LPad->getNextNode();
if (match(NextI, m_Intrinsic<Intrinsic::eh_actions>()))
return CloningDirector::CloneInstruction;
// If the landing pad hasn't been outlined yet, the landing pad we are
// outlining now does not dominate it and so it cannot return to a block
// in this handler. In that case, we can just insert a stub landing
// pad now and patch it up later.
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::handleIndirectBr(
ValueToValueMapTy &VMap,
const IndirectBrInst *IBr,
BasicBlock *NewBB) {
// If this indirect branch is not part of a landing pad block, just clone it.
const BasicBlock *ParentBB = IBr->getParent();
if (!ParentBB->isLandingPad())
return CloningDirector::CloneInstruction;
// If it is part of a landing pad, we want to filter out target blocks
// that are not part of the handler we are outlining.
const LandingPadInst *LPad = ParentBB->getLandingPadInst();
// Save this correlation for later processing.
NestedLPtoOriginalLP[cast<LandingPadInst>(VMap[LPad])] = LPad;
// We should only get here for landing pads that have already been outlined.
assert(match(LPad->getNextNode(), m_Intrinsic<Intrinsic::eh_actions>()));
// Copy the indirectbr, but only include targets that were previously
// identified as EH blocks and are dominated by the nested landing pad.
SetVector<const BasicBlock *> ReturnTargets;
for (int I = 0, E = IBr->getNumDestinations(); I < E; ++I) {
auto *TargetBB = IBr->getDestination(I);
if (EHBlocks.count(const_cast<BasicBlock*>(TargetBB)) &&
DT->dominates(ParentBB, TargetBB)) {
DEBUG(dbgs() << " Adding destination " << TargetBB->getName() << "\n");
ReturnTargets.insert(TargetBB);
}
}
IndirectBrInst *NewBranch =
IndirectBrInst::Create(const_cast<Value *>(IBr->getAddress()),
ReturnTargets.size(), NewBB);
for (auto *Target : ReturnTargets)
NewBranch->addDestination(const_cast<BasicBlock*>(Target));
// The operands and targets of the branch instruction are remapped later
// because it is a terminator. Tell the cloning code to clone the
// blocks we just added to the target list.
return CloningDirector::CloneSuccessors;
}
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::handleIndirectBr(
ValueToValueMapTy &VMap,
const IndirectBrInst *IBr,
BasicBlock *NewBB) {
// No special handling is required for cleanup cloning.
return CloningDirector::CloneInstruction;
}
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.localrecover.
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.localescape.
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
// preceding 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.localaddress()
// call void @"fin$parent"(iN 1, i8* %fp)
if (isLocalAddressCall(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 (!isLocalAddressCall(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 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 on x64, since those happen to match the
// prototype provided by the runtime.
if (TheTriple.getArch() == Triple::x86_64) {
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) {
assert(II->getIntrinsicID() == Intrinsic::eh_actions &&
"attempted to parse non eh.actions intrinsic");
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());
}
static int addUnwindMapEntry(WinEHFuncInfo &FuncInfo, int ToState,
const Value *V) {
WinEHUnwindMapEntry UME;
UME.ToState = ToState;
UME.Cleanup = V;
FuncInfo.UnwindMap.push_back(UME);
return FuncInfo.getLastStateNumber();
}
static void addTryBlockMapEntry(WinEHFuncInfo &FuncInfo, int TryLow,
int TryHigh, int CatchHigh,
ArrayRef<const CatchPadInst *> Handlers) {
WinEHTryBlockMapEntry TBME;
TBME.TryLow = TryLow;
TBME.TryHigh = TryHigh;
TBME.CatchHigh = CatchHigh;
assert(TBME.TryLow <= TBME.TryHigh);
for (const CatchPadInst *CPI : Handlers) {
WinEHHandlerType HT;
Constant *TypeInfo = cast<Constant>(CPI->getArgOperand(0));
if (TypeInfo->isNullValue())
HT.TypeDescriptor = nullptr;
else
HT.TypeDescriptor = cast<GlobalVariable>(TypeInfo->stripPointerCasts());
HT.Adjectives = cast<ConstantInt>(CPI->getArgOperand(1))->getZExtValue();
HT.Handler = CPI->getParent();
HT.CatchObjRecoverIdx = -2;
if (isa<ConstantPointerNull>(CPI->getArgOperand(2)))
HT.CatchObj.Alloca = nullptr;
else
HT.CatchObj.Alloca = cast<AllocaInst>(CPI->getArgOperand(2));
TBME.HandlerArray.push_back(HT);
}
FuncInfo.TryBlockMap.push_back(TBME);
}
static const CatchPadInst *getSingleCatchPadPredecessor(const BasicBlock *BB) {
for (const BasicBlock *PredBlock : predecessors(BB))
if (auto *CPI = dyn_cast<CatchPadInst>(PredBlock->getFirstNonPHI()))
return CPI;
return nullptr;
}
/// Find all the catchpads that feed directly into the catchendpad. Frontends
/// using this personality should ensure that each catchendpad and catchpad has
/// one or zero catchpad predecessors.
///
/// The following C++ generates the IR after it:
/// try {
/// } catch (A) {
/// } catch (B) {
/// }
///
/// IR:
/// %catchpad.A
/// catchpad [i8* A typeinfo]
/// to label %catch.A unwind label %catchpad.B
/// %catchpad.B
/// catchpad [i8* B typeinfo]
/// to label %catch.B unwind label %endcatches
/// %endcatches
/// catchendblock unwind to caller
static void
findCatchPadsForCatchEndPad(const BasicBlock *CatchEndBB,
SmallVectorImpl<const CatchPadInst *> &Handlers) {
const CatchPadInst *CPI = getSingleCatchPadPredecessor(CatchEndBB);
while (CPI) {
Handlers.push_back(CPI);
CPI = getSingleCatchPadPredecessor(CPI->getParent());
}
// We've pushed these back into reverse source order. Reverse them to get
// the list back into source order.
std::reverse(Handlers.begin(), Handlers.end());
}
// Given BB which ends in an unwind edge, return the EHPad that this BB belongs
// to. If the unwind edge came from an invoke, return null.
static const BasicBlock *getEHPadFromPredecessor(const BasicBlock *BB) {
const TerminatorInst *TI = BB->getTerminator();
if (isa<InvokeInst>(TI))
return nullptr;
if (TI->isEHPad())
return BB;
return cast<CleanupReturnInst>(TI)->getCleanupPad()->getParent();
}
static void calculateExplicitCXXStateNumbers(WinEHFuncInfo &FuncInfo,
const BasicBlock &BB,
int ParentState) {
assert(BB.isEHPad());
const Instruction *FirstNonPHI = BB.getFirstNonPHI();
// All catchpad instructions will be handled when we process their
// respective catchendpad instruction.
if (isa<CatchPadInst>(FirstNonPHI))
return;
if (isa<CatchEndPadInst>(FirstNonPHI)) {
SmallVector<const CatchPadInst *, 2> Handlers;
findCatchPadsForCatchEndPad(&BB, Handlers);
const BasicBlock *FirstTryPad = Handlers.front()->getParent();
int TryLow = addUnwindMapEntry(FuncInfo, ParentState, nullptr);
FuncInfo.EHPadStateMap[Handlers.front()] = TryLow;
for (const BasicBlock *PredBlock : predecessors(FirstTryPad))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitCXXStateNumbers(FuncInfo, *PredBlock, TryLow);
int CatchLow = addUnwindMapEntry(FuncInfo, ParentState, nullptr);
// catchpads are separate funclets in C++ EH due to the way rethrow works.
// In SEH, they aren't, so no invokes will unwind to the catchendpad.
FuncInfo.EHPadStateMap[FirstNonPHI] = CatchLow;
int TryHigh = CatchLow - 1;
for (const BasicBlock *PredBlock : predecessors(&BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitCXXStateNumbers(FuncInfo, *PredBlock, CatchLow);
int CatchHigh = FuncInfo.getLastStateNumber();
addTryBlockMapEntry(FuncInfo, TryLow, TryHigh, CatchHigh, Handlers);
DEBUG(dbgs() << "TryLow[" << FirstTryPad->getName() << "]: " << TryLow
<< '\n');
DEBUG(dbgs() << "TryHigh[" << FirstTryPad->getName() << "]: " << TryHigh
<< '\n');
DEBUG(dbgs() << "CatchHigh[" << FirstTryPad->getName() << "]: " << CatchHigh
<< '\n');
} else if (isa<CleanupPadInst>(FirstNonPHI)) {
int CleanupState = addUnwindMapEntry(FuncInfo, ParentState, &BB);
FuncInfo.EHPadStateMap[FirstNonPHI] = CleanupState;
DEBUG(dbgs() << "Assigning state #" << CleanupState << " to BB "
<< BB.getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(&BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitCXXStateNumbers(FuncInfo, *PredBlock, CleanupState);
} else if (isa<TerminatePadInst>(FirstNonPHI)) {
report_fatal_error("Not yet implemented!");
} else {
llvm_unreachable("unexpected EH Pad!");
}
}
static int addSEHExcept(WinEHFuncInfo &FuncInfo, int ParentState,
const Function *Filter, const BasicBlock *Handler) {
SEHUnwindMapEntry Entry;
Entry.ToState = ParentState;
Entry.IsFinally = false;
Entry.Filter = Filter;
Entry.Handler = Handler;
FuncInfo.SEHUnwindMap.push_back(Entry);
return FuncInfo.SEHUnwindMap.size() - 1;
}
static int addSEHFinally(WinEHFuncInfo &FuncInfo, int ParentState,
const BasicBlock *Handler) {
SEHUnwindMapEntry Entry;
Entry.ToState = ParentState;
Entry.IsFinally = true;
Entry.Filter = nullptr;
Entry.Handler = Handler;
FuncInfo.SEHUnwindMap.push_back(Entry);
return FuncInfo.SEHUnwindMap.size() - 1;
}
static void calculateExplicitSEHStateNumbers(WinEHFuncInfo &FuncInfo,
const BasicBlock &BB,
int ParentState) {
assert(BB.isEHPad());
const Instruction *FirstNonPHI = BB.getFirstNonPHI();
// All catchpad instructions will be handled when we process their
// respective catchendpad instruction.
if (isa<CatchPadInst>(FirstNonPHI))
return;
if (isa<CatchEndPadInst>(FirstNonPHI)) {
// Extract the filter function and the __except basic block and create a
// state for them.
SmallVector<const CatchPadInst *, 1> Handlers;
findCatchPadsForCatchEndPad(&BB, Handlers);
assert(Handlers.size() == 1 &&
"SEH doesn't have multiple handlers per __try");
const CatchPadInst *CPI = Handlers.front();
const BasicBlock *CatchPadBB = CPI->getParent();
const Constant *FilterOrNull =
cast<Constant>(CPI->getArgOperand(0)->stripPointerCasts());
const Function *Filter = dyn_cast<Function>(FilterOrNull);
assert((Filter || FilterOrNull->isNullValue()) &&
"unexpected filter value");
int TryState = addSEHExcept(FuncInfo, ParentState, Filter, CatchPadBB);
// Everything in the __try block uses TryState as its parent state.
FuncInfo.EHPadStateMap[CPI] = TryState;
DEBUG(dbgs() << "Assigning state #" << TryState << " to BB "
<< CatchPadBB->getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(CatchPadBB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitSEHStateNumbers(FuncInfo, *PredBlock, TryState);
// Everything in the __except block unwinds to ParentState, just like code
// outside the __try.
FuncInfo.EHPadStateMap[FirstNonPHI] = ParentState;
DEBUG(dbgs() << "Assigning state #" << ParentState << " to BB "
<< BB.getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(&BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitSEHStateNumbers(FuncInfo, *PredBlock, ParentState);
} else if (isa<CleanupPadInst>(FirstNonPHI)) {
int CleanupState = addSEHFinally(FuncInfo, ParentState, &BB);
FuncInfo.EHPadStateMap[FirstNonPHI] = CleanupState;
DEBUG(dbgs() << "Assigning state #" << CleanupState << " to BB "
<< BB.getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(&BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitSEHStateNumbers(FuncInfo, *PredBlock, CleanupState);
} else if (isa<CleanupEndPadInst>(FirstNonPHI)) {
// Anything unwinding through CleanupEndPadInst is in ParentState.
FuncInfo.EHPadStateMap[FirstNonPHI] = ParentState;
DEBUG(dbgs() << "Assigning state #" << ParentState << " to BB "
<< BB.getName() << '\n');
for (const BasicBlock *PredBlock : predecessors(&BB))
if ((PredBlock = getEHPadFromPredecessor(PredBlock)))
calculateExplicitSEHStateNumbers(FuncInfo, *PredBlock, ParentState);
} else if (isa<TerminatePadInst>(FirstNonPHI)) {
report_fatal_error("Not yet implemented!");
} else {
llvm_unreachable("unexpected EH Pad!");
}
}
/// Check if the EH Pad unwinds to caller. Cleanups are a little bit of a
/// special case because we have to look at the cleanupret instruction that uses
/// the cleanuppad.
static bool doesEHPadUnwindToCaller(const Instruction *EHPad) {
auto *CPI = dyn_cast<CleanupPadInst>(EHPad);
if (!CPI)
return EHPad->mayThrow();
// This cleanup does not return or unwind, so we say it unwinds to caller.
if (CPI->use_empty())
return true;
const Instruction *User = CPI->user_back();
if (auto *CRI = dyn_cast<CleanupReturnInst>(User))
return CRI->unwindsToCaller();
return cast<CleanupEndPadInst>(User)->unwindsToCaller();
}
void llvm::calculateSEHStateNumbers(const Function *Fn,
WinEHFuncInfo &FuncInfo) {
// Don't compute state numbers twice.
if (!FuncInfo.SEHUnwindMap.empty())
return;
for (const BasicBlock &BB : *Fn) {
if (!BB.isEHPad() || !doesEHPadUnwindToCaller(BB.getFirstNonPHI()))
continue;
calculateExplicitSEHStateNumbers(FuncInfo, BB, -1);
}
}
void llvm::calculateWinCXXEHStateNumbers(const Function *Fn,
WinEHFuncInfo &FuncInfo) {
// Return if it's already been done.
if (!FuncInfo.EHPadStateMap.empty())
return;
for (const BasicBlock &BB : *Fn) {
if (!BB.isEHPad())
continue;
if (BB.isLandingPad())
report_fatal_error("MSVC C++ EH cannot use landingpads");
const Instruction *FirstNonPHI = BB.getFirstNonPHI();
// Skip cleanupendpads; they are exits, not entries.
if (isa<CleanupEndPadInst>(FirstNonPHI))
continue;
if (!doesEHPadUnwindToCaller(FirstNonPHI))
continue;
calculateExplicitCXXStateNumbers(FuncInfo, BB, -1);
}
}
static int addClrEHHandler(WinEHFuncInfo &FuncInfo, int ParentState,
ClrHandlerType HandlerType, uint32_t TypeToken,
const BasicBlock *Handler) {
ClrEHUnwindMapEntry Entry;
Entry.Parent = ParentState;
Entry.Handler = Handler;
Entry.HandlerType = HandlerType;
Entry.TypeToken = TypeToken;
FuncInfo.ClrEHUnwindMap.push_back(Entry);
return FuncInfo.ClrEHUnwindMap.size() - 1;
}
void llvm::calculateClrEHStateNumbers(const Function *Fn,
WinEHFuncInfo &FuncInfo) {
// Return if it's already been done.
if (!FuncInfo.EHPadStateMap.empty())
return;
SmallVector<std::pair<const Instruction *, int>, 8> Worklist;
// Each pad needs to be able to refer to its parent, so scan the function
// looking for top-level handlers and seed the worklist with them.
for (const BasicBlock &BB : *Fn) {
if (!BB.isEHPad())
continue;
if (BB.isLandingPad())
report_fatal_error("CoreCLR EH cannot use landingpads");
const Instruction *FirstNonPHI = BB.getFirstNonPHI();
if (!doesEHPadUnwindToCaller(FirstNonPHI))
continue;
// queue this with sentinel parent state -1 to mean unwind to caller.
Worklist.emplace_back(FirstNonPHI, -1);
}
while (!Worklist.empty()) {
const Instruction *Pad;
int ParentState;
std::tie(Pad, ParentState) = Worklist.pop_back_val();
int PredState;
if (const CleanupEndPadInst *EndPad = dyn_cast<CleanupEndPadInst>(Pad)) {
FuncInfo.EHPadStateMap[EndPad] = ParentState;
// Queue the cleanuppad, in case it doesn't have a cleanupret.
Worklist.emplace_back(EndPad->getCleanupPad(), ParentState);
// Preds of the endpad should get the parent state.
PredState = ParentState;
} else if (const CleanupPadInst *Cleanup = dyn_cast<CleanupPadInst>(Pad)) {
// A cleanup can have multiple exits; don't re-process after the first.
if (FuncInfo.EHPadStateMap.count(Pad))
continue;
// CoreCLR personality uses arity to distinguish faults from finallies.
const BasicBlock *PadBlock = Cleanup->getParent();
ClrHandlerType HandlerType =
(Cleanup->getNumOperands() ? ClrHandlerType::Fault
: ClrHandlerType::Finally);
int NewState =
addClrEHHandler(FuncInfo, ParentState, HandlerType, 0, PadBlock);
FuncInfo.EHPadStateMap[Cleanup] = NewState;
// Propagate the new state to all preds of the cleanup
PredState = NewState;
} else if (const CatchEndPadInst *EndPad = dyn_cast<CatchEndPadInst>(Pad)) {
FuncInfo.EHPadStateMap[EndPad] = ParentState;
// Preds of the endpad should get the parent state.
PredState = ParentState;
} else if (const CatchPadInst *Catch = dyn_cast<CatchPadInst>(Pad)) {
const BasicBlock *Handler = Catch->getNormalDest();
uint32_t TypeToken = static_cast<uint32_t>(
cast<ConstantInt>(Catch->getArgOperand(0))->getZExtValue());
int NewState = addClrEHHandler(FuncInfo, ParentState,
ClrHandlerType::Catch, TypeToken, Handler);
FuncInfo.EHPadStateMap[Catch] = NewState;
// Preds of the catch get its state
PredState = NewState;
} else {
llvm_unreachable("Unexpected EH pad");
}
// Queue all predecessors with the given state
for (const BasicBlock *Pred : predecessors(Pad->getParent())) {
if ((Pred = getEHPadFromPredecessor(Pred)))
Worklist.emplace_back(Pred->getFirstNonPHI(), PredState);
}
}
}
void WinEHPrepare::replaceTerminatePadWithCleanup(Function &F) {
if (Personality != EHPersonality::MSVC_CXX)
return;
for (BasicBlock &BB : F) {
Instruction *First = BB.getFirstNonPHI();
auto *TPI = dyn_cast<TerminatePadInst>(First);
if (!TPI)
continue;
if (TPI->getNumArgOperands() != 1)
report_fatal_error(
"Expected a unary terminatepad for MSVC C++ personalities!");
auto *TerminateFn = dyn_cast<Function>(TPI->getArgOperand(0));
if (!TerminateFn)
report_fatal_error("Function operand expected in terminatepad for MSVC "
"C++ personalities!");
// Insert the cleanuppad instruction.
auto *CPI = CleanupPadInst::Create(
BB.getContext(), {}, Twine("terminatepad.for.", BB.getName()), &BB);
// Insert the call to the terminate instruction.
auto *CallTerminate = CallInst::Create(TerminateFn, {}, &BB);
CallTerminate->setDoesNotThrow();
CallTerminate->setDoesNotReturn();
CallTerminate->setCallingConv(TerminateFn->getCallingConv());
// Insert a new terminator for the cleanuppad using the same successor as
// the terminatepad.
CleanupReturnInst::Create(CPI, TPI->getUnwindDest(), &BB);
// Let's remove the terminatepad now that we've inserted the new
// instructions.
TPI->eraseFromParent();
}
}
static void
colorFunclets(Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks,
std::map<BasicBlock *, std::set<BasicBlock *>> &BlockColors,
std::map<BasicBlock *, std::set<BasicBlock *>> &FuncletBlocks,
std::map<BasicBlock *, std::set<BasicBlock *>> &FuncletChildren) {
SmallVector<std::pair<BasicBlock *, BasicBlock *>, 16> Worklist;
BasicBlock *EntryBlock = &F.getEntryBlock();
// Build up the color map, which maps each block to its set of 'colors'.
// For any block B, the "colors" of B are the set of funclets F (possibly
// including a root "funclet" representing the main function), such that
// F will need to directly contain B or a copy of B (where the term "directly
// contain" is used to distinguish from being "transitively contained" in
// a nested funclet).
// Use a CFG walk driven by a worklist of (block, color) pairs. The "color"
// sets attached during this processing to a block which is the entry of some
// funclet F is actually the set of F's parents -- i.e. the union of colors
// of all predecessors of F's entry. For all other blocks, the color sets
// are as defined above. A post-pass fixes up the block color map to reflect
// the same sense of "color" for funclet entries as for other blocks.
Worklist.push_back({EntryBlock, EntryBlock});
while (!Worklist.empty()) {
BasicBlock *Visiting;
BasicBlock *Color;
std::tie(Visiting, Color) = Worklist.pop_back_val();
Instruction *VisitingHead = Visiting->getFirstNonPHI();
if (VisitingHead->isEHPad() && !isa<CatchEndPadInst>(VisitingHead) &&
!isa<CleanupEndPadInst>(VisitingHead)) {
// Mark this as a funclet head as a member of itself.
FuncletBlocks[Visiting].insert(Visiting);
// Queue exits with the parent color.
for (User *Exit : VisitingHead->users()) {
for (BasicBlock *Succ :
successors(cast<Instruction>(Exit)->getParent())) {
if (BlockColors[Succ].insert(Color).second) {
Worklist.push_back({Succ, Color});
}
}
}
// Handle CatchPad specially since its successors need different colors.
if (CatchPadInst *CatchPad = dyn_cast<CatchPadInst>(VisitingHead)) {
// Visit the normal successor with the color of the new EH pad, and
// visit the unwind successor with the color of the parent.
BasicBlock *NormalSucc = CatchPad->getNormalDest();
if (BlockColors[NormalSucc].insert(Visiting).second) {
Worklist.push_back({NormalSucc, Visiting});
}
BasicBlock *UnwindSucc = CatchPad->getUnwindDest();
if (BlockColors[UnwindSucc].insert(Color).second) {
Worklist.push_back({UnwindSucc, Color});
}
continue;
}
// Switch color to the current node, except for terminate pads which
// have no bodies and only unwind successors and so need their successors
// visited with the color of the parent.
if (!isa<TerminatePadInst>(VisitingHead))
Color = Visiting;
} else {
// Note that this is a member of the given color.
FuncletBlocks[Color].insert(Visiting);
}
TerminatorInst *Terminator = Visiting->getTerminator();
if (isa<CleanupReturnInst>(Terminator) ||
isa<CatchReturnInst>(Terminator) ||
isa<CleanupEndPadInst>(Terminator)) {
// These blocks' successors have already been queued with the parent
// color.
continue;
}
for (BasicBlock *Succ : successors(Visiting)) {
if (isa<CatchEndPadInst>(Succ->getFirstNonPHI())) {
// The catchendpad needs to be visited with the parent's color, not
// the current color. This will happen in the code above that visits
// any catchpad unwind successor with the parent color, so we can
// safely skip this successor here.
continue;
}
if (BlockColors[Succ].insert(Color).second) {
Worklist.push_back({Succ, Color});
}
}
}
// The processing above actually accumulated the parent set for this
// funclet into the color set for its entry; use the parent set to
// populate the children map, and reset the color set to include just
// the funclet itself (no instruction can target a funclet entry except on
// that transitions to the child funclet).
for (BasicBlock *FuncletEntry : EntryBlocks) {
std::set<BasicBlock *> &ColorMapItem = BlockColors[FuncletEntry];
for (BasicBlock *Parent : ColorMapItem)
FuncletChildren[Parent].insert(FuncletEntry);
ColorMapItem.clear();
ColorMapItem.insert(FuncletEntry);
}
}
void WinEHPrepare::colorFunclets(Function &F,
SmallVectorImpl<BasicBlock *> &EntryBlocks) {
::colorFunclets(F, EntryBlocks, BlockColors, FuncletBlocks, FuncletChildren);
}
void llvm::calculateCatchReturnSuccessorColors(const Function *Fn,
WinEHFuncInfo &FuncInfo) {
SmallVector<LandingPadInst *, 4> LPads;
SmallVector<ResumeInst *, 4> Resumes;
SmallVector<BasicBlock *, 4> EntryBlocks;
// colorFunclets needs the set of EntryBlocks, get them using
// findExceptionalConstructs.
bool ForExplicitEH = findExceptionalConstructs(const_cast<Function &>(*Fn),
LPads, Resumes, EntryBlocks);
if (!ForExplicitEH)
return;
std::map<BasicBlock *, std::set<BasicBlock *>> BlockColors;
std::map<BasicBlock *, std::set<BasicBlock *>> FuncletBlocks;
std::map<BasicBlock *, std::set<BasicBlock *>> FuncletChildren;
// Figure out which basic blocks belong to which funclets.
colorFunclets(const_cast<Function &>(*Fn), EntryBlocks, BlockColors,
FuncletBlocks, FuncletChildren);
// We need to find the catchret successors. To do this, we must first find
// all the catchpad funclets.
for (auto &Funclet : FuncletBlocks) {
// Figure out what kind of funclet we are looking at; We only care about
// catchpads.
BasicBlock *FuncletPadBB = Funclet.first;
Instruction *FirstNonPHI = FuncletPadBB->getFirstNonPHI();
auto *CatchPad = dyn_cast<CatchPadInst>(FirstNonPHI);
if (!CatchPad)
continue;
// The users of a catchpad are always catchrets.
for (User *Exit : CatchPad->users()) {
auto *CatchReturn = cast<CatchReturnInst>(Exit);
BasicBlock *CatchRetSuccessor = CatchReturn->getSuccessor();
std::set<BasicBlock *> &SuccessorColors = BlockColors[CatchRetSuccessor];
assert(SuccessorColors.size() == 1 && "Expected BB to be monochrome!");
BasicBlock *Color = *SuccessorColors.begin();
if (auto *CPI = dyn_cast<CatchPadInst>(Color->getFirstNonPHI()))
Color = CPI->getNormalDest();
// Record the catchret successor's funclet membership.
FuncInfo.CatchRetSuccessorColorMap[CatchReturn] = Color;
}
}
}
void WinEHPrepare::demotePHIsOnFunclets(Function &F) {
// Strip PHI nodes off of EH pads.
SmallVector<PHINode *, 16> PHINodes;
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) {
BasicBlock *BB = FI++;
if (!BB->isEHPad())
continue;
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
Instruction *I = BI++;
auto *PN = dyn_cast<PHINode>(I);
// Stop at the first non-PHI.
if (!PN)
break;
AllocaInst *SpillSlot = insertPHILoads(PN, F);
if (SpillSlot)
insertPHIStores(PN, SpillSlot);
PHINodes.push_back(PN);
}
}
for (auto *PN : PHINodes) {
// There may be lingering uses on other EH PHIs being removed
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
PN->eraseFromParent();
}
}
void WinEHPrepare::demoteUsesBetweenFunclets(Function &F) {
// Turn all inter-funclet uses of a Value into loads and stores.
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) {
BasicBlock *BB = FI++;
std::set<BasicBlock *> &ColorsForBB = BlockColors[BB];
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
Instruction *I = BI++;
// Funclets are permitted to use static allocas.
if (auto *AI = dyn_cast<AllocaInst>(I))
if (AI->isStaticAlloca())
continue;
demoteNonlocalUses(I, ColorsForBB, F);
}
}
}
void WinEHPrepare::demoteArgumentUses(Function &F) {
// Also demote function parameters used in funclets.
std::set<BasicBlock *> &ColorsForEntry = BlockColors[&F.getEntryBlock()];
for (Argument &Arg : F.args())
demoteNonlocalUses(&Arg, ColorsForEntry, F);
}
void WinEHPrepare::cloneCommonBlocks(
Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks) {
// We need to clone all blocks which belong to multiple funclets. Values are
// remapped throughout the funclet to propogate both the new instructions
// *and* the new basic blocks themselves.
for (BasicBlock *FuncletPadBB : EntryBlocks) {
std::set<BasicBlock *> &BlocksInFunclet = FuncletBlocks[FuncletPadBB];
std::map<BasicBlock *, BasicBlock *> Orig2Clone;
ValueToValueMapTy VMap;
for (BasicBlock *BB : BlocksInFunclet) {
std::set<BasicBlock *> &ColorsForBB = BlockColors[BB];
// We don't need to do anything if the block is monochromatic.
size_t NumColorsForBB = ColorsForBB.size();
if (NumColorsForBB == 1)
continue;
// Create a new basic block and copy instructions into it!
BasicBlock *CBB =
CloneBasicBlock(BB, VMap, Twine(".for.", FuncletPadBB->getName()));
// Insert the clone immediately after the original to ensure determinism
// and to keep the same relative ordering of any funclet's blocks.
CBB->insertInto(&F, BB->getNextNode());
// Add basic block mapping.
VMap[BB] = CBB;
// Record delta operations that we need to perform to our color mappings.
Orig2Clone[BB] = CBB;
}
// Update our color mappings to reflect that one block has lost a color and
// another has gained a color.
for (auto &BBMapping : Orig2Clone) {
BasicBlock *OldBlock = BBMapping.first;
BasicBlock *NewBlock = BBMapping.second;
BlocksInFunclet.insert(NewBlock);
BlockColors[NewBlock].insert(FuncletPadBB);
BlocksInFunclet.erase(OldBlock);
BlockColors[OldBlock].erase(FuncletPadBB);
}
// Loop over all of the instructions in the function, fixing up operand
// references as we go. This uses VMap to do all the hard work.
for (BasicBlock *BB : BlocksInFunclet)
// Loop over all instructions, fixing each one as we find it...
for (Instruction &I : *BB)
RemapInstruction(&I, VMap, RF_IgnoreMissingEntries);
// Check to see if SuccBB has PHI nodes. If so, we need to add entries to
// the PHI nodes for NewBB now.
for (auto &BBMapping : Orig2Clone) {
BasicBlock *OldBlock = BBMapping.first;
BasicBlock *NewBlock = BBMapping.second;
for (BasicBlock *SuccBB : successors(NewBlock)) {
for (Instruction &SuccI : *SuccBB) {
auto *SuccPN = dyn_cast<PHINode>(&SuccI);
if (!SuccPN)
break;
// Ok, we have a PHI node. Figure out what the incoming value was for
// the OldBlock.
int OldBlockIdx = SuccPN->getBasicBlockIndex(OldBlock);
if (OldBlockIdx == -1)
break;
Value *IV = SuccPN->getIncomingValue(OldBlockIdx);
// Remap the value if necessary.
if (auto *Inst = dyn_cast<Instruction>(IV)) {
ValueToValueMapTy::iterator I = VMap.find(Inst);
if (I != VMap.end())
IV = I->second;
}
SuccPN->addIncoming(IV, NewBlock);
}
}
}
for (ValueToValueMapTy::value_type VT : VMap) {
// If there were values defined in BB that are used outside the funclet,
// then we now have to update all uses of the value to use either the
// original value, the cloned value, or some PHI derived value. This can
// require arbitrary PHI insertion, of which we are prepared to do, clean
// these up now.
SmallVector<Use *, 16> UsesToRename;
auto *OldI = dyn_cast<Instruction>(const_cast<Value *>(VT.first));
if (!OldI)
continue;
auto *NewI = cast<Instruction>(VT.second);
// Scan all uses of this instruction to see if it is used outside of its
// funclet, and if so, record them in UsesToRename.
for (Use &U : OldI->uses()) {
Instruction *UserI = cast<Instruction>(U.getUser());
BasicBlock *UserBB = UserI->getParent();
std::set<BasicBlock *> &ColorsForUserBB = BlockColors[UserBB];
assert(!ColorsForUserBB.empty());
if (ColorsForUserBB.size() > 1 ||
*ColorsForUserBB.begin() != FuncletPadBB)
UsesToRename.push_back(&U);
}
// If there are no uses outside the block, we're done with this
// instruction.
if (UsesToRename.empty())
continue;
// We found a use of OldI outside of the funclet. Rename all uses of OldI
// that are outside its funclet to be uses of the appropriate PHI node
// etc.
SSAUpdater SSAUpdate;
SSAUpdate.Initialize(OldI->getType(), OldI->getName());
SSAUpdate.AddAvailableValue(OldI->getParent(), OldI);
SSAUpdate.AddAvailableValue(NewI->getParent(), NewI);
while (!UsesToRename.empty())
SSAUpdate.RewriteUseAfterInsertions(*UsesToRename.pop_back_val());
}
}
}
void WinEHPrepare::removeImplausibleTerminators(Function &F) {
// Remove implausible terminators and replace them with UnreachableInst.
for (auto &Funclet : FuncletBlocks) {
BasicBlock *FuncletPadBB = Funclet.first;
std::set<BasicBlock *> &BlocksInFunclet = Funclet.second;
Instruction *FirstNonPHI = FuncletPadBB->getFirstNonPHI();
auto *CatchPad = dyn_cast<CatchPadInst>(FirstNonPHI);
auto *CleanupPad = dyn_cast<CleanupPadInst>(FirstNonPHI);
for (BasicBlock *BB : BlocksInFunclet) {
TerminatorInst *TI = BB->getTerminator();
// CatchPadInst and CleanupPadInst can't transfer control to a ReturnInst.
bool IsUnreachableRet = isa<ReturnInst>(TI) && (CatchPad || CleanupPad);
// The token consumed by a CatchReturnInst must match the funclet token.
bool IsUnreachableCatchret = false;
if (auto *CRI = dyn_cast<CatchReturnInst>(TI))
IsUnreachableCatchret = CRI->getCatchPad() != CatchPad;
// The token consumed by a CleanupReturnInst must match the funclet token.
bool IsUnreachableCleanupret = false;
if (auto *CRI = dyn_cast<CleanupReturnInst>(TI))
IsUnreachableCleanupret = CRI->getCleanupPad() != CleanupPad;
// The token consumed by a CleanupEndPadInst must match the funclet token.
bool IsUnreachableCleanupendpad = false;
if (auto *CEPI = dyn_cast<CleanupEndPadInst>(TI))
IsUnreachableCleanupendpad = CEPI->getCleanupPad() != CleanupPad;
if (IsUnreachableRet || IsUnreachableCatchret ||
IsUnreachableCleanupret || IsUnreachableCleanupendpad) {
// Loop through all of our successors and make sure they know that one
// of their predecessors is going away.
for (BasicBlock *SuccBB : TI->successors())
SuccBB->removePredecessor(BB);
if (IsUnreachableCleanupendpad) {
// We can't simply replace a cleanupendpad with unreachable, because
// its predecessor edges are EH edges and unreachable is not an EH
// pad. Change all predecessors to the "unwind to caller" form.
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
PI != PE;) {
BasicBlock *Pred = *PI++;
removeUnwindEdge(Pred);
}
}
new UnreachableInst(BB->getContext(), TI);
TI->eraseFromParent();
}
// FIXME: Check for invokes/cleanuprets/cleanupendpads which unwind to
// implausible catchendpads (i.e. catchendpad not in immediate parent
// funclet).
}
}
}
void WinEHPrepare::cleanupPreparedFunclets(Function &F) {
// Clean-up some of the mess we made by removing useles PHI nodes, trivial
// branches, etc.
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) {
BasicBlock *BB = FI++;
SimplifyInstructionsInBlock(BB);
ConstantFoldTerminator(BB, /*DeleteDeadConditions=*/true);
MergeBlockIntoPredecessor(BB);
}
// We might have some unreachable blocks after cleaning up some impossible
// control flow.
removeUnreachableBlocks(F);
}
void WinEHPrepare::verifyPreparedFunclets(Function &F) {
// Recolor the CFG to verify that all is well.
for (BasicBlock &BB : F) {
size_t NumColors = BlockColors[&BB].size();
assert(NumColors == 1 && "Expected monochromatic BB!");
if (NumColors == 0)
report_fatal_error("Uncolored BB!");
if (NumColors > 1)
report_fatal_error("Multicolor BB!");
if (!DisableDemotion) {
bool EHPadHasPHI = BB.isEHPad() && isa<PHINode>(BB.begin());
assert(!EHPadHasPHI && "EH Pad still has a PHI!");
if (EHPadHasPHI)
report_fatal_error("EH Pad still has a PHI!");
}
}
}
bool WinEHPrepare::prepareExplicitEH(
Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks) {
// Remove unreachable blocks. It is not valuable to assign them a color and
// their existence can trick us into thinking values are alive when they are
// not.
removeUnreachableBlocks(F);
replaceTerminatePadWithCleanup(F);
// Determine which blocks are reachable from which funclet entries.
colorFunclets(F, EntryBlocks);
if (!DisableDemotion) {
demotePHIsOnFunclets(F);
demoteUsesBetweenFunclets(F);
demoteArgumentUses(F);
}
cloneCommonBlocks(F, EntryBlocks);
if (!DisableCleanups) {
removeImplausibleTerminators(F);
cleanupPreparedFunclets(F);
}
verifyPreparedFunclets(F);
BlockColors.clear();
FuncletBlocks.clear();
FuncletChildren.clear();
return true;
}
// TODO: Share loads when one use dominates another, or when a catchpad exit
// dominates uses (needs dominators).
AllocaInst *WinEHPrepare::insertPHILoads(PHINode *PN, Function &F) {
BasicBlock *PHIBlock = PN->getParent();
AllocaInst *SpillSlot = nullptr;
if (isa<CleanupPadInst>(PHIBlock->getFirstNonPHI())) {
// Insert a load in place of the PHI and replace all uses.
SpillSlot = new AllocaInst(PN->getType(), nullptr,
Twine(PN->getName(), ".wineh.spillslot"),
F.getEntryBlock().begin());
Value *V = new LoadInst(SpillSlot, Twine(PN->getName(), ".wineh.reload"),
PHIBlock->getFirstInsertionPt());
PN->replaceAllUsesWith(V);
return SpillSlot;
}
DenseMap<BasicBlock *, Value *> Loads;
for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end();
UI != UE;) {
Use &U = *UI++;
auto *UsingInst = cast<Instruction>(U.getUser());
BasicBlock *UsingBB = UsingInst->getParent();
if (UsingBB->isEHPad()) {
// Use is on an EH pad phi. Leave it alone; we'll insert loads and
// stores for it separately.
assert(isa<PHINode>(UsingInst));
continue;
}
replaceUseWithLoad(PN, U, SpillSlot, Loads, F);
}
return SpillSlot;
}
// TODO: improve store placement. Inserting at def is probably good, but need
// to be careful not to introduce interfering stores (needs liveness analysis).
// TODO: identify related phi nodes that can share spill slots, and share them
// (also needs liveness).
void WinEHPrepare::insertPHIStores(PHINode *OriginalPHI,
AllocaInst *SpillSlot) {
// Use a worklist of (Block, Value) pairs -- the given Value needs to be
// stored to the spill slot by the end of the given Block.
SmallVector<std::pair<BasicBlock *, Value *>, 4> Worklist;
Worklist.push_back({OriginalPHI->getParent(), OriginalPHI});
while (!Worklist.empty()) {
BasicBlock *EHBlock;
Value *InVal;
std::tie(EHBlock, InVal) = Worklist.pop_back_val();
PHINode *PN = dyn_cast<PHINode>(InVal);
if (PN && PN->getParent() == EHBlock) {
// The value is defined by another PHI we need to remove, with no room to
// insert a store after the PHI, so each predecessor needs to store its
// incoming value.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i < e; ++i) {
Value *PredVal = PN->getIncomingValue(i);
// Undef can safely be skipped.
if (isa<UndefValue>(PredVal))
continue;
insertPHIStore(PN->getIncomingBlock(i), PredVal, SpillSlot, Worklist);
}
} else {
// We need to store InVal, which dominates EHBlock, but can't put a store
// in EHBlock, so need to put stores in each predecessor.
for (BasicBlock *PredBlock : predecessors(EHBlock)) {
insertPHIStore(PredBlock, InVal, SpillSlot, Worklist);
}
}
}
}
void WinEHPrepare::insertPHIStore(
BasicBlock *PredBlock, Value *PredVal, AllocaInst *SpillSlot,
SmallVectorImpl<std::pair<BasicBlock *, Value *>> &Worklist) {
if (PredBlock->isEHPad() &&
!isa<CleanupPadInst>(PredBlock->getFirstNonPHI())) {
// Pred is unsplittable, so we need to queue it on the worklist.
Worklist.push_back({PredBlock, PredVal});
return;
}
// Otherwise, insert the store at the end of the basic block.
new StoreInst(PredVal, SpillSlot, PredBlock->getTerminator());
}
// TODO: Share loads for same-funclet uses (requires dominators if funclets
// aren't properly nested).
void WinEHPrepare::demoteNonlocalUses(Value *V,
std::set<BasicBlock *> &ColorsForBB,
Function &F) {
// Tokens can only be used non-locally due to control flow involving
// unreachable edges. Don't try to demote the token usage, we'll simply
// delete the cloned user later.
if (isa<CatchPadInst>(V) || isa<CleanupPadInst>(V))
return;
DenseMap<BasicBlock *, Value *> Loads;
AllocaInst *SpillSlot = nullptr;
for (Value::use_iterator UI = V->use_begin(), UE = V->use_end(); UI != UE;) {
Use &U = *UI++;
auto *UsingInst = cast<Instruction>(U.getUser());
BasicBlock *UsingBB = UsingInst->getParent();
// Is the Use inside a block which is colored the same as the Def?
// If so, we don't need to escape the Def because we will clone
// ourselves our own private copy.
std::set<BasicBlock *> &ColorsForUsingBB = BlockColors[UsingBB];
if (ColorsForUsingBB == ColorsForBB)
continue;
replaceUseWithLoad(V, U, SpillSlot, Loads, F);
}
if (SpillSlot) {
// Insert stores of the computed value into the stack slot.
// We have to be careful if I is an invoke instruction,
// because we can't insert the store AFTER the terminator instruction.
BasicBlock::iterator InsertPt;
if (isa<Argument>(V)) {
InsertPt = F.getEntryBlock().getTerminator();
} else if (isa<TerminatorInst>(V)) {
auto *II = cast<InvokeInst>(V);
// We cannot demote invoke instructions to the stack if their normal
// edge is critical. Therefore, split the critical edge and create a
// basic block into which the store can be inserted.
if (!II->getNormalDest()->getSinglePredecessor()) {
unsigned SuccNum =
GetSuccessorNumber(II->getParent(), II->getNormalDest());
assert(isCriticalEdge(II, SuccNum) && "Expected a critical edge!");
BasicBlock *NewBlock = SplitCriticalEdge(II, SuccNum);
assert(NewBlock && "Unable to split critical edge.");
// Update the color mapping for the newly split edge.
std::set<BasicBlock *> &ColorsForUsingBB = BlockColors[II->getParent()];
BlockColors[NewBlock] = ColorsForUsingBB;
for (BasicBlock *FuncletPad : ColorsForUsingBB)
FuncletBlocks[FuncletPad].insert(NewBlock);
}
InsertPt = II->getNormalDest()->getFirstInsertionPt();
} else {
InsertPt = cast<Instruction>(V);
++InsertPt;
// Don't insert before PHI nodes or EH pad instrs.
for (; isa<PHINode>(InsertPt) || InsertPt->isEHPad(); ++InsertPt)
;
}
new StoreInst(V, SpillSlot, InsertPt);
}
}
void WinEHPrepare::replaceUseWithLoad(Value *V, Use &U, AllocaInst *&SpillSlot,
DenseMap<BasicBlock *, Value *> &Loads,
Function &F) {
// Lazilly create the spill slot.
if (!SpillSlot)
SpillSlot = new AllocaInst(V->getType(), nullptr,
Twine(V->getName(), ".wineh.spillslot"),
F.getEntryBlock().begin());
auto *UsingInst = cast<Instruction>(U.getUser());
if (auto *UsingPHI = dyn_cast<PHINode>(UsingInst)) {
// If this is a PHI node, we can't insert a load of the value before
// the use. Instead insert the load in the predecessor block
// corresponding to the incoming value.
//
// Note that if there are multiple edges from a basic block to this
// PHI node that we cannot have multiple loads. The problem is that
// the resulting PHI node will have multiple values (from each load)
// coming in from the same block, which is illegal SSA form.
// For this reason, we keep track of and reuse loads we insert.
BasicBlock *IncomingBlock = UsingPHI->getIncomingBlock(U);
if (auto *CatchRet =
dyn_cast<CatchReturnInst>(IncomingBlock->getTerminator())) {
// Putting a load above a catchret and use on the phi would still leave
// a cross-funclet def/use. We need to split the edge, change the
// catchret to target the new block, and put the load there.
BasicBlock *PHIBlock = UsingInst->getParent();
BasicBlock *NewBlock = SplitEdge(IncomingBlock, PHIBlock);
// SplitEdge gives us:
// IncomingBlock:
// ...
// br label %NewBlock
// NewBlock:
// catchret label %PHIBlock
// But we need:
// IncomingBlock:
// ...
// catchret label %NewBlock
// NewBlock:
// br label %PHIBlock
// So move the terminators to each others' blocks and swap their
// successors.
BranchInst *Goto = cast<BranchInst>(IncomingBlock->getTerminator());
Goto->removeFromParent();
CatchRet->removeFromParent();
IncomingBlock->getInstList().push_back(CatchRet);
NewBlock->getInstList().push_back(Goto);
Goto->setSuccessor(0, PHIBlock);
CatchRet->setSuccessor(NewBlock);
// Update the color mapping for the newly split edge.
std::set<BasicBlock *> &ColorsForPHIBlock = BlockColors[PHIBlock];
BlockColors[NewBlock] = ColorsForPHIBlock;
for (BasicBlock *FuncletPad : ColorsForPHIBlock)
FuncletBlocks[FuncletPad].insert(NewBlock);
// Treat the new block as incoming for load insertion.
IncomingBlock = NewBlock;
}
Value *&Load = Loads[IncomingBlock];
// Insert the load into the predecessor block
if (!Load)
Load = new LoadInst(SpillSlot, Twine(V->getName(), ".wineh.reload"),
/*Volatile=*/false, IncomingBlock->getTerminator());
U.set(Load);
} else {
// Reload right before the old use.
auto *Load = new LoadInst(SpillSlot, Twine(V->getName(), ".wineh.reload"),
/*Volatile=*/false, UsingInst);
U.set(Load);
}
}
void WinEHFuncInfo::addIPToStateRange(const BasicBlock *PadBB,
MCSymbol *InvokeBegin,
MCSymbol *InvokeEnd) {
assert(PadBB->isEHPad() && EHPadStateMap.count(PadBB->getFirstNonPHI()) &&
"should get EH pad BB with precomputed state");
InvokeToStateMap[InvokeBegin] =
std::make_pair(EHPadStateMap[PadBB->getFirstNonPHI()], InvokeEnd);
}
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