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37da701417
llvm-mirror/lib/CodeGen/WinEHPrepare.cpp
Reid Kleckner 37da701417 [WinEH] Demote values and phis live across exception handlers up front 
In particular, this handles SSA values that are live *out* of a handler.
The existing code only handles values that are live *in* to a handler.

It also handles phi nodes in the block where normal control should
resume after the end of a catch handler.  When EH return points have phi
nodes, we need to split the return edge. It is impossible for phi
elimination to emit copies in the previous block if that block gets
outlined. The indirectbr that we leave in the function is only notional,
and is eliminated from the MachineFunction CFG early on.

Reviewers: majnemer, andrew.w.kaylor

Differential Revision: http://reviews.llvm.org/D9158

llvm-svn: 235545
2015-04-22 21:05:21 +00:00

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//===-- WinEHPrepare - Prepare exception handling for code generation ---===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass lowers LLVM IR exception handling into something closer to what the
// backend wants. It snifs the personality function to see which kind of
// preparation is necessary. If the personality function uses the Itanium LSDA,
// this pass delegates to the DWARF EH preparation pass.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Passes.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Analysis/LibCallSemantics.h"
#include "llvm/CodeGen/WinEHFuncInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include <memory>
using namespace llvm;
using namespace llvm::PatternMatch;
#define DEBUG_TYPE "winehprepare"
namespace {
// This map is used to model frame variable usage during outlining, to
// construct a structure type to hold the frame variables in a frame
// allocation block, and to remap the frame variable allocas (including
// spill locations as needed) to GEPs that get the variable from the
// frame allocation structure.
typedef MapVector<Value *, TinyPtrVector<AllocaInst *>> FrameVarInfoMap;
// TinyPtrVector cannot hold nullptr, so we need our own sentinel that isn't
// quite null.
AllocaInst *getCatchObjectSentinel() {
return static_cast<AllocaInst *>(nullptr) + 1;
}
typedef SmallSet<BasicBlock *, 4> VisitedBlockSet;
class LandingPadActions;
class LandingPadMap;
typedef DenseMap<const BasicBlock *, CatchHandler *> CatchHandlerMapTy;
typedef DenseMap<const BasicBlock *, CleanupHandler *> CleanupHandlerMapTy;
class WinEHPrepare : public FunctionPass {
public:
static char ID; // Pass identification, replacement for typeid.
WinEHPrepare(const TargetMachine *TM = nullptr)
: FunctionPass(ID), DT(nullptr) {}
bool runOnFunction(Function &Fn) override;
bool doFinalization(Module &M) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
const char *getPassName() const override {
return "Windows exception handling preparation";
}
private:
bool prepareExceptionHandlers(Function &F,
SmallVectorImpl<LandingPadInst *> &LPads);
void promoteLandingPadValues(LandingPadInst *LPad);
void demoteValuesLiveAcrossHandlers(Function &F,
SmallVectorImpl<LandingPadInst *> &LPads);
void completeNestedLandingPad(Function *ParentFn,
LandingPadInst *OutlinedLPad,
const LandingPadInst *OriginalLPad,
FrameVarInfoMap &VarInfo);
bool outlineHandler(ActionHandler *Action, Function *SrcFn,
LandingPadInst *LPad, BasicBlock *StartBB,
FrameVarInfoMap &VarInfo);
void addStubInvokeToHandlerIfNeeded(Function *Handler, Value *PersonalityFn);
void mapLandingPadBlocks(LandingPadInst *LPad, LandingPadActions &Actions);
CatchHandler *findCatchHandler(BasicBlock *BB, BasicBlock *&NextBB,
VisitedBlockSet &VisitedBlocks);
void findCleanupHandlers(LandingPadActions &Actions, BasicBlock *StartBB,
BasicBlock *EndBB);
void processSEHCatchHandler(CatchHandler *Handler, BasicBlock *StartBB);
// All fields are reset by runOnFunction.
DominatorTree *DT;
EHPersonality Personality;
CatchHandlerMapTy CatchHandlerMap;
CleanupHandlerMapTy CleanupHandlerMap;
DenseMap<const LandingPadInst *, LandingPadMap> LPadMaps;
// This maps landing pad instructions found in outlined handlers to
// the landing pad instruction in the parent function from which they
// were cloned. The cloned/nested landing pad is used as the key
// because the landing pad may be cloned into multiple handlers.
// This map will be used to add the llvm.eh.actions call to the nested
// landing pads after all handlers have been outlined.
DenseMap<LandingPadInst *, const LandingPadInst *> NestedLPtoOriginalLP;
// This maps blocks in the parent function which are destinations of
// catch handlers to cloned blocks in (other) outlined handlers. This
// handles the case where a nested landing pads has a catch handler that
// returns to a handler function rather than the parent function.
// The original block is used as the key here because there should only
// ever be one handler function from which the cloned block is not pruned.
// The original block will be pruned from the parent function after all
// handlers have been outlined. This map will be used to adjust the
// return instructions of handlers which return to the block that was
// outlined into a handler. This is done after all handlers have been
// outlined but before the outlined code is pruned from the parent function.
DenseMap<const BasicBlock *, BasicBlock *> LPadTargetBlocks;
};
class WinEHFrameVariableMaterializer : public ValueMaterializer {
public:
WinEHFrameVariableMaterializer(Function *OutlinedFn,
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, FrameVarInfoMap &VarInfo,
LandingPadMap &LPadMap)
: Materializer(HandlerFn, VarInfo),
SelectorIDType(Type::getInt32Ty(HandlerFn->getContext())),
Int8PtrType(Type::getInt8PtrTy(HandlerFn->getContext())),
LPadMap(LPadMap) {
auto AI = HandlerFn->getArgumentList().begin();
++AI;
EstablisherFrame = AI;
}
CloningAction handleInstruction(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) override;
virtual CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) = 0;
virtual CloningAction handleEndCatch(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) = 0;
virtual CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) = 0;
virtual CloningAction handleInvoke(ValueToValueMapTy &VMap,
const InvokeInst *Invoke,
BasicBlock *NewBB) = 0;
virtual CloningAction handleResume(ValueToValueMapTy &VMap,
const ResumeInst *Resume,
BasicBlock *NewBB) = 0;
virtual CloningAction handleCompare(ValueToValueMapTy &VMap,
const CmpInst *Compare,
BasicBlock *NewBB) = 0;
virtual CloningAction handleLandingPad(ValueToValueMapTy &VMap,
const LandingPadInst *LPad,
BasicBlock *NewBB) = 0;
ValueMaterializer *getValueMaterializer() override { return &Materializer; }
protected:
WinEHFrameVariableMaterializer Materializer;
Type *SelectorIDType;
Type *Int8PtrType;
LandingPadMap &LPadMap;
/// The value representing the parent frame pointer.
Value *EstablisherFrame;
};
class WinEHCatchDirector : public WinEHCloningDirectorBase {
public:
WinEHCatchDirector(
Function *CatchFn, Value *Selector, FrameVarInfoMap &VarInfo,
LandingPadMap &LPadMap,
DenseMap<LandingPadInst *, const LandingPadInst *> &NestedLPads)
: WinEHCloningDirectorBase(CatchFn, VarInfo, LPadMap),
CurrentSelector(Selector->stripPointerCasts()),
ExceptionObjectVar(nullptr), NestedLPtoOriginalLP(NestedLPads) {}
CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) override;
CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
BasicBlock *NewBB) override;
CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) override;
CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
BasicBlock *NewBB) override;
CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
BasicBlock *NewBB) override;
CloningAction handleCompare(ValueToValueMapTy &VMap,
const CmpInst *Compare, BasicBlock *NewBB) override;
CloningAction handleLandingPad(ValueToValueMapTy &VMap,
const LandingPadInst *LPad,
BasicBlock *NewBB) override;
Value *getExceptionVar() { return ExceptionObjectVar; }
TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
private:
Value *CurrentSelector;
Value *ExceptionObjectVar;
TinyPtrVector<BasicBlock *> ReturnTargets;
// This will be a reference to the field of the same name in the WinEHPrepare
// object which instantiates this WinEHCatchDirector object.
DenseMap<LandingPadInst *, const LandingPadInst *> &NestedLPtoOriginalLP;
};
class WinEHCleanupDirector : public WinEHCloningDirectorBase {
public:
WinEHCleanupDirector(Function *CleanupFn, FrameVarInfoMap &VarInfo,
LandingPadMap &LPadMap)
: WinEHCloningDirectorBase(CleanupFn, VarInfo, LPadMap) {}
CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) override;
CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
BasicBlock *NewBB) override;
CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
const Instruction *Inst,
BasicBlock *NewBB) override;
CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
BasicBlock *NewBB) override;
CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
BasicBlock *NewBB) override;
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);
}
// FIXME: Remove this once the backend can handle the prepared IR.
static cl::opt<bool>
SEHPrepare("sehprepare", cl::Hidden,
cl::desc("Prepare functions with SEH personalities"));
bool WinEHPrepare::runOnFunction(Function &Fn) {
// No need to prepare outlined handlers.
if (Fn.hasFnAttribute("wineh-parent"))
return false;
SmallVector<LandingPadInst *, 4> LPads;
SmallVector<ResumeInst *, 4> Resumes;
for (BasicBlock &BB : Fn) {
if (auto *LP = BB.getLandingPadInst())
LPads.push_back(LP);
if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
Resumes.push_back(Resume);
}
// No need to prepare functions that lack landing pads.
if (LPads.empty())
return false;
// Classify the personality to see what kind of preparation we need.
Personality = classifyEHPersonality(LPads.back()->getPersonalityFn());
// Do nothing if this is not an MSVC personality.
if (!isMSVCEHPersonality(Personality))
return false;
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
if (isAsynchronousEHPersonality(Personality) && !SEHPrepare) {
// Replace all resume instructions with unreachable.
// FIXME: Remove this once the backend can handle the prepared IR.
for (ResumeInst *Resume : Resumes) {
IRBuilder<>(Resume).CreateUnreachable();
Resume->eraseFromParent();
}
return true;
}
// If there were any landing pads, prepareExceptionHandlers will make changes.
prepareExceptionHandlers(Fn, LPads);
return true;
}
bool WinEHPrepare::doFinalization(Module &M) { return false; }
void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<DominatorTreeWrapperPass>();
}
static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
Constant *&Selector, BasicBlock *&NextBB);
// Finds blocks reachable from the starting set Worklist. Does not follow unwind
// edges or blocks listed in StopPoints.
static void findReachableBlocks(SmallPtrSetImpl<BasicBlock *> &ReachableBBs,
SetVector<BasicBlock *> &Worklist,
const SetVector<BasicBlock *> *StopPoints) {
while (!Worklist.empty()) {
BasicBlock *BB = Worklist.pop_back_val();
// Don't cross blocks that we should stop at.
if (StopPoints && StopPoints->count(BB))
continue;
if (!ReachableBBs.insert(BB).second)
continue; // Already visited.
// Don't follow unwind edges of invokes.
if (auto *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
Worklist.insert(II->getNormalDest());
continue;
}
// Otherwise, follow all successors.
Worklist.insert(succ_begin(BB), succ_end(BB));
}
}
/// Find all points where exceptional control rejoins normal control flow via
/// llvm.eh.endcatch. Add them to the normal bb reachability worklist.
static void 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_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 = BB->splitBasicBlock(I.getNextNode(), "ehreturn");
}
// 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.
static void findSEHEHReturnPoints(Function &F,
SetVector<BasicBlock *> &EHReturnBlocks) {
for (auto BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
BasicBlock *BB = BBI;
// If the landingpad is a catch-all, treat the whole lpad as if it is
// reachable from normal control flow.
// FIXME: This is imprecise. We need a better way of identifying where a
// catch-all starts and cleanups stop. As far as LLVM is concerned, there
// is no difference.
if (isCatchAllLandingPad(BB)) {
EHReturnBlocks.insert(BB);
continue;
}
BasicBlock *CatchHandler;
BasicBlock *NextBB;
Constant *Selector;
if (isSelectorDispatch(BB, CatchHandler, Selector, NextBB)) {
// Split the edge if there is a phi node. Returning from EH to a phi node
// is just as impossible as having a phi after an indirectbr.
if (isa<PHINode>(CatchHandler->begin())) {
DEBUG(dbgs() << "splitting EH return edge from " << BB->getName()
<< " to " << CatchHandler->getName() << '\n');
BBI = CatchHandler = SplitCriticalEdge(
BB, std::find(succ_begin(BB), succ_end(BB), CatchHandler));
}
EHReturnBlocks.insert(CatchHandler);
}
}
}
/// Ensure that all values live into and out of exception handlers are stored
/// in memory.
/// FIXME: This falls down when values are defined in one handler and live into
/// another handler. For example, a cleanup defines a value used only by a
/// catch handler.
void WinEHPrepare::demoteValuesLiveAcrossHandlers(
Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
DEBUG(dbgs() << "Demoting values live across exception handlers in function "
<< F.getName() << '\n');
// Build a set of all non-exceptional blocks and exceptional blocks.
// - Non-exceptional blocks are blocks reachable from the entry block while
// not following invoke unwind edges.
// - Exceptional blocks are blocks reachable from landingpads. Analysis does
// not follow llvm.eh.endcatch blocks, which mark a transition from
// exceptional to normal control.
SmallPtrSet<BasicBlock *, 4> NormalBlocks;
SmallPtrSet<BasicBlock *, 4> EHBlocks;
SetVector<BasicBlock *> EHReturnBlocks;
SetVector<BasicBlock *> Worklist;
if (Personality == EHPersonality::MSVC_CXX)
findCXXEHReturnPoints(F, EHReturnBlocks);
else
findSEHEHReturnPoints(F, EHReturnBlocks);
DEBUG({
dbgs() << "identified the following blocks as EH return points:\n";
for (BasicBlock *BB : EHReturnBlocks)
dbgs() << " " << BB->getName() << '\n';
});
// Join points should not have phis at this point, unless they are a
// landingpad, in which case we will demote their phis later.
#ifndef NDEBUG
for (BasicBlock *BB : EHReturnBlocks)
assert((BB->isLandingPad() || !isa<PHINode>(BB->begin())) &&
"non-lpad EH return block has phi");
#endif
// Normal blocks are the blocks reachable from the entry block and all EH
// return points.
Worklist = EHReturnBlocks;
Worklist.insert(&F.getEntryBlock());
findReachableBlocks(NormalBlocks, Worklist, nullptr);
DEBUG({
dbgs() << "marked the following blocks as normal:\n";
for (BasicBlock *BB : NormalBlocks)
dbgs() << " " << BB->getName() << '\n';
});
// Exceptional blocks are the blocks reachable from landingpads that don't
// cross EH return points.
Worklist.clear();
for (auto *LPI : LPads)
Worklist.insert(LPI->getParent());
findReachableBlocks(EHBlocks, Worklist, &EHReturnBlocks);
DEBUG({
dbgs() << "marked the following blocks as exceptional:\n";
for (BasicBlock *BB : EHBlocks)
dbgs() << " " << BB->getName() << '\n';
});
SetVector<Argument *> ArgsToDemote;
SetVector<Instruction *> InstrsToDemote;
for (BasicBlock &BB : F) {
bool IsNormalBB = NormalBlocks.count(&BB);
bool IsEHBB = EHBlocks.count(&BB);
if (!IsNormalBB && !IsEHBB)
continue; // Blocks that are neither normal nor EH are unreachable.
for (Instruction &I : BB) {
for (Value *Op : I.operands()) {
// Don't demote static allocas, constants, and labels.
if (isa<Constant>(Op) || isa<BasicBlock>(Op) || isa<InlineAsm>(Op))
continue;
auto *AI = dyn_cast<AllocaInst>(Op);
if (AI && AI->isStaticAlloca())
continue;
if (auto *Arg = dyn_cast<Argument>(Op)) {
if (IsEHBB) {
DEBUG(dbgs() << "Demoting argument " << *Arg
<< " used by EH instr: " << I << "\n");
ArgsToDemote.insert(Arg);
}
continue;
}
auto *OpI = cast<Instruction>(Op);
BasicBlock *OpBB = OpI->getParent();
// If a value is produced and consumed in the same BB, we don't need to
// demote it.
if (OpBB == &BB)
continue;
bool IsOpNormalBB = NormalBlocks.count(OpBB);
bool IsOpEHBB = EHBlocks.count(OpBB);
if (IsNormalBB != IsOpNormalBB || IsEHBB != IsOpEHBB) {
DEBUG({
dbgs() << "Demoting instruction live in-out from EH:\n";
dbgs() << "Instr: " << *OpI << '\n';
dbgs() << "User: " << I << '\n';
});
InstrsToDemote.insert(OpI);
}
}
}
}
// Demote values live into and out of handlers.
// FIXME: This demotion is inefficient. We should insert spills at the point
// of definition, insert one reload in each handler that uses the value, and
// insert reloads in the BB used to rejoin normal control flow.
Instruction *AllocaInsertPt = F.getEntryBlock().getFirstInsertionPt();
for (Instruction *I : InstrsToDemote)
DemoteRegToStack(*I, false, AllocaInsertPt);
// Demote arguments separately, and only for uses in EH blocks.
for (Argument *Arg : ArgsToDemote) {
auto *Slot = new AllocaInst(Arg->getType(), nullptr,
Arg->getName() + ".reg2mem", AllocaInsertPt);
SmallVector<User *, 4> Users(Arg->user_begin(), Arg->user_end());
for (User *U : Users) {
auto *I = dyn_cast<Instruction>(U);
if (I && EHBlocks.count(I->getParent())) {
auto *Reload = new LoadInst(Slot, Arg->getName() + ".reload", false, I);
U->replaceUsesOfWith(Arg, Reload);
}
}
new StoreInst(Arg, Slot, AllocaInsertPt);
}
// Demote landingpad phis, as the landingpad will be removed from the machine
// CFG.
for (LandingPadInst *LPI : LPads) {
BasicBlock *BB = LPI->getParent();
while (auto *Phi = dyn_cast<PHINode>(BB->begin()))
DemotePHIToStack(Phi, AllocaInsertPt);
}
DEBUG(dbgs() << "Demoted " << InstrsToDemote.size() << " instructions and "
<< ArgsToDemote.size() << " arguments for WinEHPrepare\n\n");
}
bool WinEHPrepare::prepareExceptionHandlers(
Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
// Don't run on functions that are already prepared.
for (LandingPadInst *LPad : LPads) {
BasicBlock *LPadBB = LPad->getParent();
for (Instruction &Inst : *LPadBB)
if (match(&Inst, m_Intrinsic<Intrinsic::eh_actions>()))
return false;
}
demoteValuesLiveAcrossHandlers(F, LPads);
// These containers are used to re-map frame variables that are used in
// outlined catch and cleanup handlers. They will be populated as the
// handlers are outlined.
FrameVarInfoMap FrameVarInfo;
bool HandlersOutlined = false;
Module *M = F.getParent();
LLVMContext &Context = M->getContext();
// Create a new function to receive the handler contents.
PointerType *Int8PtrType = Type::getInt8PtrTy(Context);
Type *Int32Type = Type::getInt32Ty(Context);
Function *ActionIntrin = Intrinsic::getDeclaration(M, Intrinsic::eh_actions);
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;
}
// FIXME: This is here to help with the development of nested landing pad
// outlining. It should be removed when that is finished.
if (isa<UnreachableInst>(Inst)) {
LPadHasActionList = true;
break;
}
}
// If we've already outlined the handlers for this landingpad,
// there's nothing more to do here.
if (LPadHasActionList)
continue;
// 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);
}
// Replace the landing pad with a new llvm.eh.action based landing pad.
BasicBlock *NewLPadBB = BasicBlock::Create(Context, "lpad", &F, LPadBB);
assert(!isa<PHINode>(LPadBB->begin()));
auto *NewLPad = cast<LandingPadInst>(LPad->clone());
NewLPadBB->getInstList().push_back(NewLPad);
while (!pred_empty(LPadBB)) {
auto *pred = *pred_begin(LPadBB);
InvokeInst *Invoke = cast<InvokeInst>(pred->getTerminator());
Invoke->setUnwindDest(NewLPadBB);
}
// If anyone is still using the old landingpad value, just give them undef
// instead. The eh pointer and selector values are not real.
LPad->replaceAllUsesWith(UndefValue::get(LPad->getType()));
// Replace the mapping of any nested landing pad that previously mapped
// to this landing pad with a referenced to the cloned version.
for (auto &LPadPair : NestedLPtoOriginalLP) {
const LandingPadInst *OriginalLPad = LPadPair.second;
if (OriginalLPad == LPad) {
LPadPair.second = NewLPad;
}
}
// Replace uses of the old lpad in phis with this block and delete the old
// block.
LPadBB->replaceSuccessorsPhiUsesWith(NewLPadBB);
LPadBB->getTerminator()->eraseFromParent();
new UnreachableInst(LPadBB->getContext(), LPadBB);
// 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", NewLPadBB);
// Add an indirect branch listing possible successors of the catch handlers.
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(), NewLPadBB);
for (BasicBlock *Target : ReturnTargets)
Branch->addDestination(Target);
} // 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();
F.addFnAttr("wineh-parent", F.getName());
// Delete any blocks that were only used by handlers that were outlined above.
removeUnreachableBlocks(F);
BasicBlock *Entry = &F.getEntryBlock();
IRBuilder<> Builder(F.getParent()->getContext());
Builder.SetInsertPoint(Entry->getFirstInsertionPt());
Function *FrameEscapeFn =
Intrinsic::getDeclaration(M, Intrinsic::frameescape);
Function *RecoverFrameFn =
Intrinsic::getDeclaration(M, Intrinsic::framerecover);
SmallVector<Value *, 8> AllocasToEscape;
// Scan the entry block for an existing call to llvm.frameescape. We need to
// keep escaping those objects.
for (Instruction &I : F.front()) {
auto *II = dyn_cast<IntrinsicInst>(&I);
if (II && II->getIntrinsicID() == Intrinsic::frameescape) {
auto Args = II->arg_operands();
AllocasToEscape.append(Args.begin(), Args.end());
II->eraseFromParent();
break;
}
}
// Finally, replace all of the temporary allocas for frame variables used in
// the outlined handlers with calls to llvm.framerecover.
for (auto &VarInfoEntry : FrameVarInfo) {
Value *ParentVal = VarInfoEntry.first;
TinyPtrVector<AllocaInst *> &Allocas = VarInfoEntry.second;
AllocaInst *ParentAlloca = cast<AllocaInst>(ParentVal);
// FIXME: We should try to sink unescaped allocas from the parent frame into
// the child frame. If the alloca is escaped, we have to use the lifetime
// markers to ensure that the alloca is only live within the child frame.
// Add this alloca to the list of things to escape.
AllocasToEscape.push_back(ParentAlloca);
// Next replace all outlined allocas that are mapped to it.
for (AllocaInst *TempAlloca : Allocas) {
if (TempAlloca == getCatchObjectSentinel())
continue; // Skip catch parameter sentinels.
Function *HandlerFn = TempAlloca->getParent()->getParent();
// FIXME: Sink this GEP into the blocks where it is used.
Builder.SetInsertPoint(TempAlloca);
Builder.SetCurrentDebugLocation(TempAlloca->getDebugLoc());
Value *RecoverArgs[] = {
Builder.CreateBitCast(&F, Int8PtrType, ""),
&(HandlerFn->getArgumentList().back()),
llvm::ConstantInt::get(Int32Type, AllocasToEscape.size() - 1)};
Value *RecoveredAlloca = Builder.CreateCall(RecoverFrameFn, RecoverArgs);
// Add a pointer bitcast if the alloca wasn't an i8.
if (RecoveredAlloca->getType() != TempAlloca->getType()) {
RecoveredAlloca->setName(Twine(TempAlloca->getName()) + ".i8");
RecoveredAlloca =
Builder.CreateBitCast(RecoveredAlloca, TempAlloca->getType());
}
TempAlloca->replaceAllUsesWith(RecoveredAlloca);
TempAlloca->removeFromParent();
RecoveredAlloca->takeName(TempAlloca);
delete TempAlloca;
}
} // End for each FrameVarInfo entry.
// Insert 'call void (...)* @llvm.frameescape(...)' at the end of the entry
// block.
Builder.SetInsertPoint(&F.getEntryBlock().back());
Builder.CreateCall(FrameEscapeFn, AllocasToEscape);
// Clean up the handler action maps we created for this function
DeleteContainerSeconds(CatchHandlerMap);
CatchHandlerMap.clear();
DeleteContainerSeconds(CleanupHandlerMap);
CleanupHandlerMap.clear();
return HandlersOutlined;
}
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::completeNestedLandingPad(Function *ParentFn,
LandingPadInst *OutlinedLPad,
const LandingPadInst *OriginalLPad,
FrameVarInfoMap &FrameVarInfo) {
// Get the nested block and erase the unreachable instruction that was
// temporarily inserted as its terminator.
LLVMContext &Context = ParentFn->getContext();
BasicBlock *OutlinedBB = OutlinedLPad->getParent();
assert(isa<UnreachableInst>(OutlinedBB->getTerminator()));
OutlinedBB->getTerminator()->eraseFromParent();
// That should leave OutlinedLPad as the last instruction in its block.
assert(&OutlinedBB->back() == OutlinedLPad);
// The original landing pad will have already had its action intrinsic
// built by the outlining loop. We need to clone that into the outlined
// location. It may also be necessary to add references to the exception
// variables to the outlined handler in which this landing pad is nested
// and remap return instructions in the nested handlers that should return
// to an address in the outlined handler.
Function *OutlinedHandlerFn = OutlinedBB->getParent();
BasicBlock::const_iterator II = OriginalLPad;
++II;
// The instruction after the landing pad should now be a call to eh.actions.
const Instruction *Recover = II;
assert(match(Recover, m_Intrinsic<Intrinsic::eh_actions>()));
IntrinsicInst *EHActions = cast<IntrinsicInst>(Recover->clone());
// Remap the exception variables into the outlined function.
WinEHFrameVariableMaterializer Materializer(OutlinedHandlerFn, FrameVarInfo);
SmallVector<BlockAddress *, 4> ActionTargets;
SmallVector<ActionHandler *, 4> ActionList;
parseEHActions(EHActions, ActionList);
for (auto *Action : ActionList) {
auto *Catch = dyn_cast<CatchHandler>(Action);
if (!Catch)
continue;
// The dyn_cast to function here selects C++ catch handlers and skips
// SEH catch handlers.
auto *Handler = dyn_cast<Function>(Catch->getHandlerBlockOrFunc());
if (!Handler)
continue;
// Visit all the return instructions, looking for places that return
// to a location within OutlinedHandlerFn.
for (BasicBlock &NestedHandlerBB : *Handler) {
auto *Ret = dyn_cast<ReturnInst>(NestedHandlerBB.getTerminator());
if (!Ret)
continue;
// Handler functions must always return a block address.
BlockAddress *BA = cast<BlockAddress>(Ret->getReturnValue());
// The original target will have been in the main parent function,
// but if it is the address of a block that has been outlined, it
// should be a block that was outlined into OutlinedHandlerFn.
assert(BA->getFunction() == ParentFn);
// Ignore targets that aren't part of OutlinedHandlerFn.
if (!LPadTargetBlocks.count(BA->getBasicBlock()))
continue;
// If the return value is the address ofF a block that we
// previously outlined into the parent handler function, replace
// the return instruction and add the mapped target to the list
// of possible return addresses.
BasicBlock *MappedBB = LPadTargetBlocks[BA->getBasicBlock()];
assert(MappedBB->getParent() == OutlinedHandlerFn);
BlockAddress *NewBA = BlockAddress::get(OutlinedHandlerFn, MappedBB);
Ret->eraseFromParent();
ReturnInst::Create(Context, NewBA, &NestedHandlerBB);
ActionTargets.push_back(NewBA);
}
}
DeleteContainerPointers(ActionList);
ActionList.clear();
OutlinedBB->getInstList().push_back(EHActions);
// Insert an indirect branch into the outlined landing pad BB.
IndirectBrInst *IBr = IndirectBrInst::Create(EHActions, 0, OutlinedBB);
// Add the previously collected action targets.
for (auto *Target : ActionTargets)
IBr->addDestination(Target->getBasicBlock());
}
// This function examines a block to determine whether the block ends with a
// conditional branch to a catch handler based on a selector comparison.
// This function is used both by the WinEHPrepare::findSelectorComparison() and
// WinEHCleanupDirector::handleTypeIdFor().
static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
Constant *&Selector, BasicBlock *&NextBB) {
ICmpInst::Predicate Pred;
BasicBlock *TBB, *FBB;
Value *LHS, *RHS;
if (!match(BB->getTerminator(),
m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)), TBB, FBB)))
return false;
if (!match(LHS,
m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))) &&
!match(RHS, m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))))
return false;
if (Pred == CmpInst::ICMP_EQ) {
CatchHandler = TBB;
NextBB = FBB;
return true;
}
if (Pred == CmpInst::ICMP_NE) {
CatchHandler = FBB;
NextBB = TBB;
return true;
}
return false;
}
static bool isCatchBlock(BasicBlock *BB) {
for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
II != IE; ++II) {
if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_begincatch>()))
return true;
}
return false;
}
static BasicBlock *createStubLandingPad(Function *Handler,
Value *PersonalityFn) {
// FIXME: Finish this!
LLVMContext &Context = Handler->getContext();
BasicBlock *StubBB = BasicBlock::Create(Context, "stub");
Handler->getBasicBlockList().push_back(StubBB);
IRBuilder<> Builder(StubBB);
LandingPadInst *LPad = Builder.CreateLandingPad(
llvm::StructType::get(Type::getInt8PtrTy(Context),
Type::getInt32Ty(Context), nullptr),
PersonalityFn, 0);
LPad->setCleanup(true);
Builder.CreateUnreachable();
return StubBB;
}
// Cycles through the blocks in an outlined handler function looking for an
// invoke instruction and inserts an invoke of llvm.donothing with an empty
// landing pad if none is found. The code that generates the .xdata tables for
// the handler needs at least one landing pad to identify the parent function's
// personality.
void WinEHPrepare::addStubInvokeToHandlerIfNeeded(Function *Handler,
Value *PersonalityFn) {
ReturnInst *Ret = nullptr;
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)
continue;
// If we haven't recorded a return instruction yet, try this terminator.
Ret = dyn_cast<ReturnInst>(Terminator);
}
// If we got this far, the handler contains no invokes. We should have seen
// at least one return. We'll insert an invoke of llvm.donothing ahead of
// that return.
assert(Ret);
BasicBlock *OldRetBB = Ret->getParent();
BasicBlock *NewRetBB = SplitBlock(OldRetBB, Ret);
// SplitBlock adds an unconditional branch instruction at the end of the
// parent block. We want to replace that with an invoke call, so we can
// erase it now.
OldRetBB->getTerminator()->eraseFromParent();
BasicBlock *StubLandingPad = createStubLandingPad(Handler, PersonalityFn);
Function *F =
Intrinsic::getDeclaration(Handler->getParent(), Intrinsic::donothing);
InvokeInst::Create(F, NewRetBB, StubLandingPad, None, "", OldRetBB);
}
bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
LandingPadInst *LPad, BasicBlock *StartBB,
FrameVarInfoMap &VarInfo) {
Module *M = SrcFn->getParent();
LLVMContext &Context = M->getContext();
// Create a new function to receive the handler contents.
Type *Int8PtrType = Type::getInt8PtrTy(Context);
std::vector<Type *> ArgTys;
ArgTys.push_back(Int8PtrType);
ArgTys.push_back(Int8PtrType);
Function *Handler;
if (Action->getType() == Catch) {
FunctionType *FnType = FunctionType::get(Int8PtrType, ArgTys, false);
Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
SrcFn->getName() + ".catch", M);
} else {
FunctionType *FnType =
FunctionType::get(Type::getVoidTy(Context), ArgTys, false);
Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
SrcFn->getName() + ".cleanup", M);
}
Handler->addFnAttr("wineh-parent", SrcFn->getName());
// Generate a standard prolog to setup the frame recovery structure.
IRBuilder<> Builder(Context);
BasicBlock *Entry = BasicBlock::Create(Context, "entry");
Handler->getBasicBlockList().push_front(Entry);
Builder.SetInsertPoint(Entry);
Builder.SetCurrentDebugLocation(LPad->getDebugLoc());
std::unique_ptr<WinEHCloningDirectorBase> Director;
ValueToValueMapTy VMap;
LandingPadMap &LPadMap = LPadMaps[LPad];
if (!LPadMap.isInitialized())
LPadMap.mapLandingPad(LPad);
if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
Constant *Sel = CatchAction->getSelector();
Director.reset(new WinEHCatchDirector(Handler, Sel, VarInfo, LPadMap,
NestedLPtoOriginalLP));
LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
ConstantInt::get(Type::getInt32Ty(Context), 1));
} else {
Director.reset(new WinEHCleanupDirector(Handler, 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 first cloned block into our entry block.
BasicBlock *FirstClonedBB = std::next(Function::iterator(Entry));
Entry->getInstList().splice(Entry->end(), FirstClonedBB->getInstList());
FirstClonedBB->eraseFromParent();
// Make sure we can identify the handler's personality later.
addStubInvokeToHandlerIfNeeded(Handler, LPad->getPersonalityFn());
if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
WinEHCatchDirector *CatchDirector =
reinterpret_cast<WinEHCatchDirector *>(Director.get());
CatchAction->setExceptionVar(CatchDirector->getExceptionVar());
CatchAction->setReturnTargets(CatchDirector->getReturnTargets());
// Look for blocks that are not part of the landing pad that we just
// outlined but terminate with a call to llvm.eh.endcatch and a
// branch to a block that is in the handler we just outlined.
// These blocks will be part of a nested landing pad that intends to
// return to an address in this handler. This case is best handled
// after both landing pads have been outlined, so for now we'll just
// save the association of the blocks in LPadTargetBlocks. The
// return instructions which are created from these branches will be
// replaced after all landing pads have been outlined.
for (const auto MapEntry : VMap) {
// VMap maps all values and blocks that were just cloned, but dead
// blocks which were pruned will map to nullptr.
if (!isa<BasicBlock>(MapEntry.first) || MapEntry.second == nullptr)
continue;
const BasicBlock *MappedBB = cast<BasicBlock>(MapEntry.first);
for (auto *Pred : predecessors(const_cast<BasicBlock *>(MappedBB))) {
auto *Branch = dyn_cast<BranchInst>(Pred->getTerminator());
if (!Branch || !Branch->isUnconditional() || Pred->size() <= 1)
continue;
BasicBlock::iterator II = const_cast<BranchInst *>(Branch);
--II;
if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_endcatch>())) {
// This would indicate that a nested landing pad wants to return
// to a block that is outlined into two different handlers.
assert(!LPadTargetBlocks.count(MappedBB));
LPadTargetBlocks[MappedBB] = cast<BasicBlock>(MapEntry.second);
}
}
}
} // End if (CatchAction)
Action->setHandlerBlockOrFunc(Handler);
return true;
}
/// This BB must end in a selector dispatch. All we need to do is pass the
/// handler block to llvm.eh.actions and list it as a possible indirectbr
/// target.
void WinEHPrepare::processSEHCatchHandler(CatchHandler *CatchAction,
BasicBlock *StartBB) {
BasicBlock *HandlerBB;
BasicBlock *NextBB;
Constant *Selector;
bool Res = isSelectorDispatch(StartBB, HandlerBB, Selector, NextBB);
if (Res) {
// If this was EH dispatch, this must be a conditional branch to the handler
// block.
// FIXME: Handle instructions in the dispatch block. Currently we drop them,
// leading to crashes if some optimization hoists stuff here.
assert(CatchAction->getSelector() && HandlerBB &&
"expected catch EH dispatch");
} else {
// This must be a catch-all. Split the block after the landingpad.
assert(CatchAction->getSelector()->isNullValue() && "expected catch-all");
HandlerBB =
StartBB->splitBasicBlock(StartBB->getFirstInsertionPt(), "catch.all");
}
CatchAction->setHandlerBlockOrFunc(BlockAddress::get(HandlerBB));
TinyPtrVector<BasicBlock *> Targets(HandlerBB);
CatchAction->setReturnTargets(Targets);
}
void LandingPadMap::mapLandingPad(const LandingPadInst *LPad) {
// Each instance of this class should only ever be used to map a single
// landing pad.
assert(OriginLPad == nullptr || OriginLPad == LPad);
// If the landing pad has already been mapped, there's nothing more to do.
if (OriginLPad == LPad)
return;
OriginLPad = LPad;
// The landingpad instruction returns an aggregate value. Typically, its
// value will be passed to a pair of extract value instructions and the
// results of those extracts will have been promoted to reg values before
// this routine is called.
for (auto *U : LPad->users()) {
const ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
if (!Extract)
continue;
assert(Extract->getNumIndices() == 1 &&
"Unexpected operation: extracting both landing pad values");
unsigned int Idx = *(Extract->idx_begin());
assert((Idx == 0 || Idx == 1) &&
"Unexpected operation: extracting an unknown landing pad element");
if (Idx == 0) {
ExtractedEHPtrs.push_back(Extract);
} else if (Idx == 1) {
ExtractedSelectors.push_back(Extract);
}
}
}
bool LandingPadMap::isOriginLandingPadBlock(const BasicBlock *BB) const {
return BB->getLandingPadInst() == OriginLPad;
}
bool LandingPadMap::isLandingPadSpecificInst(const Instruction *Inst) const {
if (Inst == OriginLPad)
return true;
for (auto *Extract : ExtractedEHPtrs) {
if (Inst == Extract)
return true;
}
for (auto *Extract : ExtractedSelectors) {
if (Inst == Extract)
return true;
}
return false;
}
void LandingPadMap::remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
Value *SelectorValue) const {
// Remap all landing pad extract instructions to the specified values.
for (auto *Extract : ExtractedEHPtrs)
VMap[Extract] = EHPtrValue;
for (auto *Extract : ExtractedSelectors)
VMap[Extract] = SelectorValue;
}
static bool isFrameAddressCall(const Value *V) {
return match(const_cast<Value *>(V),
m_Intrinsic<Intrinsic::frameaddress>(m_SpecificInt(0)));
}
CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
// If this is one of the boilerplate landing pad instructions, skip it.
// The instruction will have already been remapped in VMap.
if (LPadMap.isLandingPadSpecificInst(Inst))
return CloningDirector::SkipInstruction;
// Nested landing pads will be cloned as stubs, with just the
// landingpad instruction and an unreachable instruction. When
// all landingpads have been outlined, we'll replace this with the
// llvm.eh.actions call and indirect branch created when the
// landing pad was outlined.
if (auto *LPad = dyn_cast<LandingPadInst>(Inst)) {
return handleLandingPad(VMap, LPad, NewBB);
}
if (auto *Invoke = dyn_cast<InvokeInst>(Inst))
return handleInvoke(VMap, Invoke, NewBB);
if (auto *Resume = dyn_cast<ResumeInst>(Inst))
return handleResume(VMap, Resume, NewBB);
if (auto *Cmp = dyn_cast<CmpInst>(Inst))
return handleCompare(VMap, Cmp, NewBB);
if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
return handleBeginCatch(VMap, Inst, NewBB);
if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
return handleEndCatch(VMap, Inst, NewBB);
if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
return handleTypeIdFor(VMap, Inst, NewBB);
// When outlining llvm.frameaddress(i32 0), remap that to the second argument,
// which is the FP of the parent.
if (isFrameAddressCall(Inst)) {
VMap[Inst] = EstablisherFrame;
return CloningDirector::SkipInstruction;
}
// Continue with the default cloning behavior.
return CloningDirector::CloneInstruction;
}
CloningDirector::CloningAction WinEHCatchDirector::handleLandingPad(
ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
Instruction *NewInst = LPad->clone();
if (LPad->hasName())
NewInst->setName(LPad->getName());
// Save this correlation for later processing.
NestedLPtoOriginalLP[cast<LandingPadInst>(NewInst)] = LPad;
VMap[LPad] = NewInst;
BasicBlock::InstListType &InstList = NewBB->getInstList();
InstList.push_back(NewInst);
InstList.push_back(new UnreachableInst(NewBB->getContext()));
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction WinEHCatchDirector::handleBeginCatch(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
// The argument to the call is some form of the first element of the
// landingpad aggregate value, but that doesn't matter. It isn't used
// here.
// The second argument is an outparameter where the exception object will be
// stored. Typically the exception object is a scalar, but it can be an
// aggregate when catching by value.
// FIXME: Leave something behind to indicate where the exception object lives
// for this handler. Should it be part of llvm.eh.actions?
assert(ExceptionObjectVar == nullptr && "Multiple calls to "
"llvm.eh.begincatch found while "
"outlining catch handler.");
ExceptionObjectVar = Inst->getOperand(1)->stripPointerCasts();
if (isa<ConstantPointerNull>(ExceptionObjectVar))
return CloningDirector::SkipInstruction;
assert(cast<AllocaInst>(ExceptionObjectVar)->isStaticAlloca() &&
"catch parameter is not static alloca");
Materializer.escapeCatchObject(ExceptionObjectVar);
return CloningDirector::SkipInstruction;
}
CloningDirector::CloningAction
WinEHCatchDirector::handleEndCatch(ValueToValueMapTy &VMap,
const Instruction *Inst, BasicBlock *NewBB) {
auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
// It might be interesting to track whether or not we are inside a catch
// function, but that might make the algorithm more brittle than it needs
// to be.
// The end catch call can occur in one of two places: either in a
// landingpad block that is part of the catch handlers exception mechanism,
// or at the end of the catch block. However, a catch-all handler may call
// end catch from the original landing pad. If the call occurs in a nested
// landing pad block, we must skip it and continue so that the landing pad
// gets cloned.
auto *ParentBB = IntrinCall->getParent();
if (ParentBB->isLandingPad() && !LPadMap.isOriginLandingPadBlock(ParentBB))
return CloningDirector::SkipInstruction;
// If an end catch occurs anywhere else we want to terminate the handler
// with a return to the code that follows the endcatch call. If the
// next instruction is not an unconditional branch, we need to split the
// block to provide a clear target for the return instruction.
BasicBlock *ContinueBB;
auto Next = std::next(BasicBlock::const_iterator(IntrinCall));
const BranchInst *Branch = dyn_cast<BranchInst>(Next);
if (!Branch || !Branch->isUnconditional()) {
// We're interrupting the cloning process at this location, so the
// const_cast we're doing here will not cause a problem.
ContinueBB = SplitBlock(const_cast<BasicBlock *>(ParentBB),
const_cast<Instruction *>(cast<Instruction>(Next)));
} else {
ContinueBB = Branch->getSuccessor(0);
}
ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueBB), NewBB);
ReturnTargets.push_back(ContinueBB);
// We just added a terminator to the cloned block.
// Tell the caller to stop processing the current basic block so that
// the branch instruction will be skipped.
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction WinEHCatchDirector::handleTypeIdFor(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
// This causes a replacement that will collapse the landing pad CFG based
// on the filter function we intend to match.
if (Selector == CurrentSelector)
VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
else
VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
// Tell the caller not to clone this instruction.
return CloningDirector::SkipInstruction;
}
CloningDirector::CloningAction
WinEHCatchDirector::handleInvoke(ValueToValueMapTy &VMap,
const InvokeInst *Invoke, BasicBlock *NewBB) {
return CloningDirector::CloneInstruction;
}
CloningDirector::CloningAction
WinEHCatchDirector::handleResume(ValueToValueMapTy &VMap,
const ResumeInst *Resume, BasicBlock *NewBB) {
// Resume instructions shouldn't be reachable from catch handlers.
// We still need to handle it, but it will be pruned.
BasicBlock::InstListType &InstList = NewBB->getInstList();
InstList.push_back(new UnreachableInst(NewBB->getContext()));
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction
WinEHCatchDirector::handleCompare(ValueToValueMapTy &VMap,
const CmpInst *Compare, BasicBlock *NewBB) {
const IntrinsicInst *IntrinCall = nullptr;
if (match(Compare->getOperand(0), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
IntrinCall = dyn_cast<IntrinsicInst>(Compare->getOperand(0));
} else if (match(Compare->getOperand(1), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
IntrinCall = dyn_cast<IntrinsicInst>(Compare->getOperand(1));
}
if (IntrinCall) {
Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
// This causes a replacement that will collapse the landing pad CFG based
// on the filter function we intend to match.
if (Selector == CurrentSelector->stripPointerCasts()) {
VMap[Compare] = ConstantInt::get(SelectorIDType, 1);
}
else {
VMap[Compare] = ConstantInt::get(SelectorIDType, 0);
}
return CloningDirector::SkipInstruction;
}
return CloningDirector::CloneInstruction;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleLandingPad(
ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
// The MS runtime will terminate the process if an exception occurs in a
// cleanup handler, so we shouldn't encounter landing pads in the actual
// cleanup code, but they may appear in catch blocks. Depending on where
// we started cloning we may see one, but it will get dropped during dead
// block pruning.
Instruction *NewInst = new UnreachableInst(NewBB->getContext());
VMap[LPad] = NewInst;
BasicBlock::InstListType &InstList = NewBB->getInstList();
InstList.push_back(NewInst);
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleBeginCatch(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
// Cleanup code may flow into catch blocks or the catch block may be part
// of a branch that will be optimized away. We'll insert a return
// instruction now, but it may be pruned before the cloning process is
// complete.
ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleEndCatch(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
// Cleanup handlers nested within catch handlers may begin with a call to
// eh.endcatch. We can just ignore that instruction.
return CloningDirector::SkipInstruction;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleTypeIdFor(
ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
// If we encounter a selector comparison while cloning a cleanup handler,
// we want to stop cloning immediately. Anything after the dispatch
// will be outlined into a different handler.
BasicBlock *CatchHandler;
Constant *Selector;
BasicBlock *NextBB;
if (isSelectorDispatch(const_cast<BasicBlock *>(Inst->getParent()),
CatchHandler, Selector, NextBB)) {
ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
return CloningDirector::StopCloningBB;
}
// If eg.typeid.for is called for any other reason, it can be ignored.
VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
return CloningDirector::SkipInstruction;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleInvoke(
ValueToValueMapTy &VMap, const InvokeInst *Invoke, BasicBlock *NewBB) {
// All invokes in cleanup handlers can be replaced with calls.
SmallVector<Value *, 16> CallArgs(Invoke->op_begin(), Invoke->op_end() - 3);
// Insert a normal call instruction...
CallInst *NewCall =
CallInst::Create(const_cast<Value *>(Invoke->getCalledValue()), CallArgs,
Invoke->getName(), NewBB);
NewCall->setCallingConv(Invoke->getCallingConv());
NewCall->setAttributes(Invoke->getAttributes());
NewCall->setDebugLoc(Invoke->getDebugLoc());
VMap[Invoke] = NewCall;
// Remap the operands.
llvm::RemapInstruction(NewCall, VMap, RF_None, nullptr, &Materializer);
// Insert an unconditional branch to the normal destination.
BranchInst::Create(Invoke->getNormalDest(), NewBB);
// The unwind destination won't be cloned into the new function, so
// we don't need to clean up its phi nodes.
// We just added a terminator to the cloned block.
// Tell the caller to stop processing the current basic block.
return CloningDirector::CloneSuccessors;
}
CloningDirector::CloningAction WinEHCleanupDirector::handleResume(
ValueToValueMapTy &VMap, const ResumeInst *Resume, BasicBlock *NewBB) {
ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
// We just added a terminator to the cloned block.
// Tell the caller to stop processing the current basic block so that
// the branch instruction will be skipped.
return CloningDirector::StopCloningBB;
}
CloningDirector::CloningAction
WinEHCleanupDirector::handleCompare(ValueToValueMapTy &VMap,
const CmpInst *Compare, BasicBlock *NewBB) {
if (match(Compare->getOperand(0), m_Intrinsic<Intrinsic::eh_typeid_for>()) ||
match(Compare->getOperand(1), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
VMap[Compare] = ConstantInt::get(SelectorIDType, 1);
return CloningDirector::SkipInstruction;
}
return CloningDirector::CloneInstruction;
}
WinEHFrameVariableMaterializer::WinEHFrameVariableMaterializer(
Function *OutlinedFn, FrameVarInfoMap &FrameVarInfo)
: FrameVarInfo(FrameVarInfo), Builder(OutlinedFn->getContext()) {
BasicBlock *EntryBB = &OutlinedFn->getEntryBlock();
Builder.SetInsertPoint(EntryBB, EntryBB->getFirstInsertionPt());
}
Value *WinEHFrameVariableMaterializer::materializeValueFor(Value *V) {
// If we're asked to materialize a static alloca, we temporarily create an
// alloca in the outlined function and add this to the FrameVarInfo map. When
// all the outlining is complete, we'll replace these temporary allocas with
// calls to llvm.framerecover.
if (auto *AV = dyn_cast<AllocaInst>(V)) {
assert(AV->isStaticAlloca() &&
"cannot materialize un-demoted dynamic alloca");
AllocaInst *NewAlloca = dyn_cast<AllocaInst>(AV->clone());
Builder.Insert(NewAlloca, AV->getName());
FrameVarInfo[AV].push_back(NewAlloca);
return NewAlloca;
}
if (isa<Instruction>(V) || isa<Argument>(V)) {
errs() << "Failed to demote instruction used in exception handler:\n";
errs() << " " << *V << '\n';
report_fatal_error("WinEHPrepare failed to demote instruction");
}
// Don't materialize other values.
return nullptr;
}
void WinEHFrameVariableMaterializer::escapeCatchObject(Value *V) {
// Catch parameter objects have to live in the parent frame. When we see a use
// of a catch parameter, add a sentinel to the multimap to indicate that it's
// used from another handler. This will prevent us from trying to sink the
// alloca into the handler and ensure that the catch parameter is present in
// the call to llvm.frameescape.
FrameVarInfo[V].push_back(getCatchObjectSentinel());
}
// This function maps the catch and cleanup handlers that are reachable from the
// specified landing pad. The landing pad sequence will have this basic shape:
//
// <cleanup handler>
// <selector comparison>
// <catch handler>
// <cleanup handler>
// <selector comparison>
// <catch handler>
// <cleanup handler>
// ...
//
// Any of the cleanup slots may be absent. The cleanup slots may be occupied by
// any arbitrary control flow, but all paths through the cleanup code must
// eventually reach the next selector comparison and no path can skip to a
// different selector comparisons, though some paths may terminate abnormally.
// Therefore, we will use a depth first search from the start of any given
// cleanup block and stop searching when we find the next selector comparison.
//
// If the landingpad instruction does not have a catch clause, we will assume
// that any instructions other than selector comparisons and catch handlers can
// be ignored. In practice, these will only be the boilerplate instructions.
//
// The catch handlers may also have any control structure, but we are only
// interested in the start of the catch handlers, so we don't need to actually
// follow the flow of the catch handlers. The start of the catch handlers can
// be located from the compare instructions, but they can be skipped in the
// flow by following the contrary branch.
void WinEHPrepare::mapLandingPadBlocks(LandingPadInst *LPad,
LandingPadActions &Actions) {
unsigned int NumClauses = LPad->getNumClauses();
unsigned int HandlersFound = 0;
BasicBlock *BB = LPad->getParent();
DEBUG(dbgs() << "Mapping landing pad: " << BB->getName() << "\n");
if (NumClauses == 0) {
findCleanupHandlers(Actions, BB, nullptr);
return;
}
VisitedBlockSet VisitedBlocks;
while (HandlersFound != NumClauses) {
BasicBlock *NextBB = nullptr;
// 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;
}
// 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);
// 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 {
// Since this is a catch-all handler, the selector won't actually appear
// in the code anywhere. ExpectedSelector here is the constant null ptr
// that we got from the landing pad instruction.
Action = new CatchHandler(BB, ExpectedSelector, nullptr);
CatchHandlerMap[BB] = Action;
}
Actions.insertCatchHandler(Action);
DEBUG(dbgs() << " Catch all handler at block " << BB->getName() << "\n");
++HandlersFound;
// Once we reach a catch-all, don't expect to hit a resume instruction.
BB = nullptr;
break;
}
CatchHandler *CatchAction = findCatchHandler(BB, NextBB, VisitedBlocks);
assert(CatchAction);
// See if there is any interesting code executed before the dispatch.
findCleanupHandlers(Actions, BB, CatchAction->getStartBlock());
// When the source program contains multiple nested try blocks the catch
// handlers can get strung together in such a way that we can encounter
// a dispatch for a selector that we've already had a handler for.
if (CatchAction->getSelector()->stripPointerCasts() == ExpectedSelector) {
++HandlersFound;
// Add the catch handler to the action list.
DEBUG(dbgs() << " Found catch dispatch in block "
<< CatchAction->getStartBlock()->getName() << "\n");
Actions.insertCatchHandler(CatchAction);
} else {
// Under some circumstances optimized IR will flow unconditionally into a
// handler block without checking the selector. This can only happen if
// the landing pad has a catch-all handler and the handler for the
// preceeding catch clause is identical to the catch-call handler
// (typically an empty catch). In this case, the handler must be shared
// by all remaining clauses.
if (isa<ConstantPointerNull>(
CatchAction->getSelector()->stripPointerCasts())) {
DEBUG(dbgs() << " Applying early catch-all handler in block "
<< CatchAction->getStartBlock()->getName()
<< " to all remaining clauses.\n");
Actions.insertCatchHandler(CatchAction);
return;
}
DEBUG(dbgs() << " Found extra catch dispatch in block "
<< CatchAction->getStartBlock()->getName() << "\n");
}
// Move on to the block after the catch handler.
BB = NextBB;
}
// If we didn't wind up in a catch-all, see if there is any interesting code
// executed before the resume.
findCleanupHandlers(Actions, BB, BB);
// It's possible that some optimization moved code into a landingpad that
// wasn't
// previously being used for cleanup. If that happens, we need to execute
// that
// extra code from a cleanup handler.
if (Actions.includesCleanup() && !LPad->isCleanup())
LPad->setCleanup(true);
}
// This function searches starting with the input block for the next
// block that terminates with a branch whose condition is based on a selector
// comparison. This may be the input block. See the mapLandingPadBlocks
// comments for a discussion of control flow assumptions.
//
CatchHandler *WinEHPrepare::findCatchHandler(BasicBlock *BB,
BasicBlock *&NextBB,
VisitedBlockSet &VisitedBlocks) {
// See if we've already found a catch handler use it.
// Call count() first to avoid creating a null entry for blocks
// we haven't seen before.
if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
CatchHandler *Action = cast<CatchHandler>(CatchHandlerMap[BB]);
NextBB = Action->getNextBB();
return Action;
}
// VisitedBlocks applies only to the current search. We still
// need to consider blocks that we've visited while mapping other
// landing pads.
VisitedBlocks.insert(BB);
BasicBlock *CatchBlock = nullptr;
Constant *Selector = nullptr;
// If this is the first time we've visited this block from any landing pad
// look to see if it is a selector dispatch block.
if (!CatchHandlerMap.count(BB)) {
if (isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
CatchHandler *Action = new CatchHandler(BB, Selector, NextBB);
CatchHandlerMap[BB] = Action;
return Action;
}
// If we encounter a block containing an llvm.eh.begincatch before we
// find a selector dispatch block, the handler is assumed to be
// reached unconditionally. This happens for catch-all blocks, but
// it can also happen for other catch handlers that have been combined
// with the catch-all handler during optimization.
if (isCatchBlock(BB)) {
PointerType *Int8PtrTy = Type::getInt8PtrTy(BB->getContext());
Constant *NullSelector = ConstantPointerNull::get(Int8PtrTy);
CatchHandler *Action = new CatchHandler(BB, NullSelector, nullptr);
CatchHandlerMap[BB] = Action;
return Action;
}
}
// Visit each successor, looking for the dispatch.
// FIXME: We expect to find the dispatch quickly, so this will probably
// work better as a breadth first search.
for (BasicBlock *Succ : successors(BB)) {
if (VisitedBlocks.count(Succ))
continue;
CatchHandler *Action = findCatchHandler(Succ, NextBB, VisitedBlocks);
if (Action)
return Action;
}
return nullptr;
}
// These are helper functions to combine repeated code from findCleanupHandlers.
static void createCleanupHandler(LandingPadActions &Actions,
CleanupHandlerMapTy &CleanupHandlerMap,
BasicBlock *BB) {
CleanupHandler *Action = new CleanupHandler(BB);
CleanupHandlerMap[BB] = Action;
Actions.insertCleanupHandler(Action);
DEBUG(dbgs() << " Found cleanup code in block "
<< Action->getStartBlock()->getName() << "\n");
}
static CallSite matchOutlinedFinallyCall(BasicBlock *BB,
Instruction *MaybeCall) {
// Look for finally blocks that Clang has already outlined for us.
// %fp = call i8* @llvm.frameaddress(i32 0)
// call void @"fin$parent"(iN 1, i8* %fp)
if (isFrameAddressCall(MaybeCall) && MaybeCall != BB->getTerminator())
MaybeCall = MaybeCall->getNextNode();
CallSite FinallyCall(MaybeCall);
if (!FinallyCall || FinallyCall.arg_size() != 2)
return CallSite();
if (!match(FinallyCall.getArgument(0), m_SpecificInt(1)))
return CallSite();
if (!isFrameAddressCall(FinallyCall.getArgument(1)))
return CallSite();
return FinallyCall;
}
static BasicBlock *followSingleUnconditionalBranches(BasicBlock *BB) {
// Skip single ubr blocks.
while (BB->getFirstNonPHIOrDbg() == BB->getTerminator()) {
auto *Br = dyn_cast<BranchInst>(BB->getTerminator());
if (Br && Br->isUnconditional())
BB = Br->getSuccessor(0);
else
return BB;
}
return BB;
}
// This function searches starting with the input block for the next block that
// contains code that is not part of a catch handler and would not be eliminated
// during handler outlining.
//
void WinEHPrepare::findCleanupHandlers(LandingPadActions &Actions,
BasicBlock *StartBB, BasicBlock *EndBB) {
// Here we will skip over the following:
//
// landing pad prolog:
//
// Unconditional branches
//
// Selector dispatch
//
// Resume pattern
//
// Anything else marks the start of an interesting block
BasicBlock *BB = StartBB;
// Anything other than an unconditional branch will kick us out of this loop
// one way or another.
while (BB) {
BB = followSingleUnconditionalBranches(BB);
// If we've already scanned this block, don't scan it again. If it is
// a cleanup block, there will be an action in the CleanupHandlerMap.
// If we've scanned it and it is not a cleanup block, there will be a
// nullptr in the CleanupHandlerMap. If we have not scanned it, there will
// be no entry in the CleanupHandlerMap. We must call count() first to
// avoid creating a null entry for blocks we haven't scanned.
if (CleanupHandlerMap.count(BB)) {
if (auto *Action = CleanupHandlerMap[BB]) {
Actions.insertCleanupHandler(Action);
DEBUG(dbgs() << " Found cleanup code in block "
<< Action->getStartBlock()->getName() << "\n");
// FIXME: This cleanup might chain into another, and we need to discover
// that.
return;
} else {
// Here we handle the case where the cleanup handler map contains a
// value for this block but the value is a nullptr. This means that
// we have previously analyzed the block and determined that it did
// not contain any cleanup code. Based on the earlier analysis, we
// know the the block must end in either an unconditional branch, a
// resume or a conditional branch that is predicated on a comparison
// with a selector. Either the resume or the selector dispatch
// would terminate the search for cleanup code, so the unconditional
// branch is the only case for which we might need to continue
// searching.
BasicBlock *SuccBB = followSingleUnconditionalBranches(BB);
if (SuccBB == BB || SuccBB == EndBB)
return;
BB = SuccBB;
continue;
}
}
// Create an entry in the cleanup handler map for this block. Initially
// we create an entry that says this isn't a cleanup block. If we find
// cleanup code, the caller will replace this entry.
CleanupHandlerMap[BB] = nullptr;
TerminatorInst *Terminator = BB->getTerminator();
// Landing pad blocks have extra instructions we need to accept.
LandingPadMap *LPadMap = nullptr;
if (BB->isLandingPad()) {
LandingPadInst *LPad = BB->getLandingPadInst();
LPadMap = &LPadMaps[LPad];
if (!LPadMap->isInitialized())
LPadMap->mapLandingPad(LPad);
}
// Look for the bare resume pattern:
// %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn, 0
// %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel, 1
// resume { i8*, i32 } %lpad.val2
if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
InsertValueInst *Insert1 = nullptr;
InsertValueInst *Insert2 = nullptr;
Value *ResumeVal = Resume->getOperand(0);
// If the resume value isn't a phi or landingpad value, it should be a
// series of insertions. Identify them so we can avoid them when scanning
// for cleanups.
if (!isa<PHINode>(ResumeVal) && !isa<LandingPadInst>(ResumeVal)) {
Insert2 = dyn_cast<InsertValueInst>(ResumeVal);
if (!Insert2)
return createCleanupHandler(Actions, CleanupHandlerMap, BB);
Insert1 = dyn_cast<InsertValueInst>(Insert2->getAggregateOperand());
if (!Insert1)
return createCleanupHandler(Actions, CleanupHandlerMap, BB);
}
for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
II != IE; ++II) {
Instruction *Inst = II;
if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
continue;
if (Inst == Insert1 || Inst == Insert2 || Inst == Resume)
continue;
if (!Inst->hasOneUse() ||
(Inst->user_back() != Insert1 && Inst->user_back() != Insert2)) {
return createCleanupHandler(Actions, CleanupHandlerMap, BB);
}
}
return;
}
BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
if (Branch && Branch->isConditional()) {
// Look for the selector dispatch.
// %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
// %matches = icmp eq i32 %sel, %2
// br i1 %matches, label %catch14, label %eh.resume
CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
if (!Compare || !Compare->isEquality())
return createCleanupHandler(Actions, CleanupHandlerMap, BB);
for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
II != IE; ++II) {
Instruction *Inst = II;
if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
continue;
if (Inst == Compare || Inst == Branch)
continue;
if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
continue;
return createCleanupHandler(Actions, CleanupHandlerMap, BB);
}
// The selector dispatch block should always terminate our search.
assert(BB == EndBB);
return;
}
if (isAsynchronousEHPersonality(Personality)) {
// If this is a landingpad block, split the block at the first non-landing
// pad instruction.
Instruction *MaybeCall = BB->getFirstNonPHIOrDbg();
if (LPadMap) {
while (MaybeCall != BB->getTerminator() &&
LPadMap->isLandingPadSpecificInst(MaybeCall))
MaybeCall = MaybeCall->getNextNode();
}
// Look for outlined finally calls.
if (CallSite FinallyCall = matchOutlinedFinallyCall(BB, MaybeCall)) {
Function *Fin = FinallyCall.getCalledFunction();
assert(Fin && "outlined finally call should be direct");
auto *Action = new CleanupHandler(BB);
Action->setHandlerBlockOrFunc(Fin);
Actions.insertCleanupHandler(Action);
CleanupHandlerMap[BB] = Action;
DEBUG(dbgs() << " Found frontend-outlined finally call to "
<< Fin->getName() << " in block "
<< Action->getStartBlock()->getName() << "\n");
// Split the block if there were more interesting instructions and look
// for finally calls in the normal successor block.
BasicBlock *SuccBB = BB;
if (FinallyCall.getInstruction() != BB->getTerminator() &&
FinallyCall.getInstruction()->getNextNode() != BB->getTerminator()) {
SuccBB = BB->splitBasicBlock(FinallyCall.getInstruction()->getNextNode());
} 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<ActionHandler *> &Actions) {
for (unsigned I = 0, E = II->getNumArgOperands(); I != E;) {
uint64_t ActionKind =
cast<ConstantInt>(II->getArgOperand(I))->getZExtValue();
if (ActionKind == /*catch=*/1) {
auto *Selector = cast<Constant>(II->getArgOperand(I + 1));
ConstantInt *EHObjIndex = cast<ConstantInt>(II->getArgOperand(I + 2));
int64_t EHObjIndexVal = EHObjIndex->getSExtValue();
Constant *Handler = cast<Constant>(II->getArgOperand(I + 3));
I += 4;
auto *CH = new CatchHandler(/*BB=*/nullptr, Selector, /*NextBB=*/nullptr);
CH->setHandlerBlockOrFunc(Handler);
CH->setExceptionVarIndex(EHObjIndexVal);
Actions.push_back(CH);
} else if (ActionKind == 0) {
Constant *Handler = cast<Constant>(II->getArgOperand(I + 1));
I += 2;
auto *CH = new CleanupHandler(/*BB=*/nullptr);
CH->setHandlerBlockOrFunc(Handler);
Actions.push_back(CH);
} else {
llvm_unreachable("Expected either a catch or cleanup handler!");
}
}
std::reverse(Actions.begin(), Actions.end());
}
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