//===----------------------------------------------------------------------===//
//
// This pass mulches exception handling code into a form adapted to code
-// generation. Required if using dwarf exception handling.
+// generation. Required if using dwarf exception handling.
//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "dwarfehprepare"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Analysis/Dominators.h"
#include "llvm/CodeGen/Passes.h"
-#include "llvm/Function.h"
-#include "llvm/Instructions.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/Module.h"
+#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/CFG.h"
+#include "llvm/Analysis/EHPersonalities.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/Support/IRBuilder.h"
#include "llvm/Target/TargetLowering.h"
-#include "llvm/Transforms/Utils/BasicBlockUtils.h"
-#include "llvm/Transforms/Utils/PromoteMemToReg.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
+#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
-STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved");
-STATISTIC(NumLonelyLandingPads, "Number of landing pads with no selector");
-STATISTIC(NumLonelySelectors, "Number of lonely selectors lowered");
-STATISTIC(NumLandingPadsSplit, "Number of landing pads split");
-STATISTIC(NumSelectorsAdjusted, "Number of selector results adjusted");
-STATISTIC(NumSelectorsSimplified, "Number of selectors truncated");
-STATISTIC(NumStackTempsIntroduced, "Number of stack temporaries introduced");
-STATISTIC(NumUnwindsLowered, "Number of unwind instructions lowered");
+#define DEBUG_TYPE "dwarfehprepare"
+
+STATISTIC(NumResumesLowered, "Number of resume calls lowered");
namespace {
class DwarfEHPrepare : public FunctionPass {
+ const TargetMachine *TM;
+
+ // RewindFunction - _Unwind_Resume or the target equivalent.
+ Constant *RewindFunction;
+
+ DominatorTree *DT;
const TargetLowering *TLI;
- // The eh.exception intrinsic.
- Function *ExceptionIntrinsic;
+ bool InsertUnwindResumeCalls(Function &Fn);
+ Value *GetExceptionObject(ResumeInst *RI);
+ size_t
+ pruneUnreachableResumes(Function &Fn,
+ SmallVectorImpl<ResumeInst *> &Resumes,
+ SmallVectorImpl<LandingPadInst *> &CleanupLPads);
- // The eh.selector intrinsic.
- Function *SelectorIntrinsic;
+ public:
+ static char ID; // Pass identification, replacement for typeid.
- // The eh.typeid.for intrinsic.
- Function *TypeIdIntrinsic;
+ // INITIALIZE_TM_PASS requires a default constructor, but it isn't used in
+ // practice.
+ DwarfEHPrepare()
+ : FunctionPass(ID), TM(nullptr), RewindFunction(nullptr), DT(nullptr),
+ TLI(nullptr) {}
- // _Unwind_Resume or the target equivalent.
- Constant *RewindFunction;
+ DwarfEHPrepare(const TargetMachine *TM)
+ : FunctionPass(ID), TM(TM), RewindFunction(nullptr), DT(nullptr),
+ TLI(nullptr) {}
- // _Unwind_RaiseException.
- Constant *UnwindFunction;
+ bool runOnFunction(Function &Fn) override;
- // Dominator info is used when turning stack temporaries into registers.
- DominatorTree *DT;
- DominanceFrontier *DF;
-
- // The function we are running on.
- Function *F;
-
- // The current context.
- LLVMContext *Context;
-
- // The personality and catch-all value for this function.
- Constant *Personality;
- Constant *CatchAll;
-
- // The landing pads for this function.
- typedef SmallPtrSet<BasicBlock*, 8> BBSet;
- BBSet LandingPads;
-
- // Stack temporary used to hold eh.exception values.
- AllocaInst *ExceptionValueVar;
-
- bool NormalizeLandingPads();
- bool LowerUnwinds();
- bool MoveSelectorCalls();
- bool RectifySelectorCalls();
- bool MoveExceptionValueCalls();
- bool AddMissingSelectors();
- bool FinishStackTemporaries();
- bool PromoteStackTemporaries();
-
- Instruction *CreateExceptionValueCall(BasicBlock *BB);
- Instruction *CreateValueLoad(BasicBlock *BB);
-
- /// CreateReadOfExceptionValue - Return the result of the eh.exception
- /// intrinsic by calling the intrinsic if in a landing pad, or loading
- /// it from the exception value variable otherwise.
- Instruction *CreateReadOfExceptionValue(BasicBlock *BB) {
- return LandingPads.count(BB) ?
- CreateExceptionValueCall(BB) : CreateValueLoad(BB);
+ bool doFinalization(Module &M) override {
+ RewindFunction = nullptr;
+ return false;
}
- public:
- static char ID; // Pass identification, replacement for typeid.
- DwarfEHPrepare(const TargetLowering *tli) :
- FunctionPass(&ID), TLI(tli), ExceptionIntrinsic(0),
- SelectorIntrinsic(0), TypeIdIntrinsic(0), RewindFunction(0),
- UnwindFunction(0) {}
-
- virtual bool runOnFunction(Function &Fn);
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
- const char *getPassName() const {
+ const char *getPassName() const override {
return "Exception handling preparation";
}
-
};
} // end anonymous namespace
char DwarfEHPrepare::ID = 0;
+INITIALIZE_TM_PASS_BEGIN(DwarfEHPrepare, "dwarfehprepare",
+ "Prepare DWARF exceptions", false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
+INITIALIZE_TM_PASS_END(DwarfEHPrepare, "dwarfehprepare",
+ "Prepare DWARF exceptions", false, false)
+
+FunctionPass *llvm::createDwarfEHPass(const TargetMachine *TM) {
+ return new DwarfEHPrepare(TM);
+}
-FunctionPass *llvm::createDwarfEHPass(const TargetLowering *tli) {
- return new DwarfEHPrepare(tli);
+void DwarfEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<TargetTransformInfoWrapperPass>();
+ AU.addRequired<DominatorTreeWrapperPass>();
}
-/// NormalizeLandingPads - Normalize and discover landing pads, noting them
-/// in the LandingPads set. A landing pad is normal if the only CFG edges
-/// that end at it are unwind edges from invoke instructions. If we inlined
-/// through an invoke we could have a normal branch from the previous
-/// unwind block through to the landing pad for the original invoke.
-/// Abnormal landing pads are fixed up by redirecting all unwind edges to
-/// a new basic block which falls through to the original.
-bool DwarfEHPrepare::NormalizeLandingPads() {
- bool Changed = false;
-
- for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
- TerminatorInst *TI = I->getTerminator();
- if (!isa<InvokeInst>(TI))
- continue;
- BasicBlock *LPad = TI->getSuccessor(1);
- // Skip landing pads that have already been normalized.
- if (LandingPads.count(LPad))
- continue;
-
- // Check that only invoke unwind edges end at the landing pad.
- bool OnlyUnwoundTo = true;
- for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad);
- PI != PE; ++PI) {
- TerminatorInst *PT = (*PI)->getTerminator();
- if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) {
- OnlyUnwoundTo = false;
- break;
+/// GetExceptionObject - Return the exception object from the value passed into
+/// the 'resume' instruction (typically an aggregate). Clean up any dead
+/// instructions, including the 'resume' instruction.
+Value *DwarfEHPrepare::GetExceptionObject(ResumeInst *RI) {
+ Value *V = RI->getOperand(0);
+ Value *ExnObj = nullptr;
+ InsertValueInst *SelIVI = dyn_cast<InsertValueInst>(V);
+ LoadInst *SelLoad = nullptr;
+ InsertValueInst *ExcIVI = nullptr;
+ bool EraseIVIs = false;
+
+ if (SelIVI) {
+ if (SelIVI->getNumIndices() == 1 && *SelIVI->idx_begin() == 1) {
+ ExcIVI = dyn_cast<InsertValueInst>(SelIVI->getOperand(0));
+ if (ExcIVI && isa<UndefValue>(ExcIVI->getOperand(0)) &&
+ ExcIVI->getNumIndices() == 1 && *ExcIVI->idx_begin() == 0) {
+ ExnObj = ExcIVI->getOperand(1);
+ SelLoad = dyn_cast<LoadInst>(SelIVI->getOperand(1));
+ EraseIVIs = true;
}
}
-
- if (OnlyUnwoundTo) {
- // Only unwind edges lead to the landing pad. Remember the landing pad.
- LandingPads.insert(LPad);
- continue;
- }
-
- // At least one normal edge ends at the landing pad. Redirect the unwind
- // edges to a new basic block which falls through into this one.
-
- // Create the new basic block.
- BasicBlock *NewBB = BasicBlock::Create(*Context,
- LPad->getName() + "_unwind_edge");
-
- // Insert it into the function right before the original landing pad.
- LPad->getParent()->getBasicBlockList().insert(LPad, NewBB);
-
- // Redirect unwind edges from the original landing pad to NewBB.
- for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) {
- TerminatorInst *PT = (*PI++)->getTerminator();
- if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad)
- // Unwind to the new block.
- PT->setSuccessor(1, NewBB);
- }
-
- // If there are any PHI nodes in LPad, we need to update them so that they
- // merge incoming values from NewBB instead.
- for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) {
- PHINode *PN = cast<PHINode>(II);
- pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB);
-
- // Check to see if all of the values coming in via unwind edges are the
- // same. If so, we don't need to create a new PHI node.
- Value *InVal = PN->getIncomingValueForBlock(*PB);
- for (pred_iterator PI = PB; PI != PE; ++PI) {
- if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) {
- InVal = 0;
- break;
- }
- }
-
- if (InVal == 0) {
- // Different unwind edges have different values. Create a new PHI node
- // in NewBB.
- PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind",
- NewBB);
- // Add an entry for each unwind edge, using the value from the old PHI.
- for (pred_iterator PI = PB; PI != PE; ++PI)
- NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI);
-
- // Now use this new PHI as the common incoming value for NewBB in PN.
- InVal = NewPN;
- }
-
- // Revector exactly one entry in the PHI node to come from NewBB
- // and delete all other entries that come from unwind edges. If
- // there are both normal and unwind edges from the same predecessor,
- // this leaves an entry for the normal edge.
- for (pred_iterator PI = PB; PI != PE; ++PI)
- PN->removeIncomingValue(*PI);
- PN->addIncoming(InVal, NewBB);
- }
-
- // Add a fallthrough from NewBB to the original landing pad.
- BranchInst::Create(LPad, NewBB);
-
- // Now update DominatorTree and DominanceFrontier analysis information.
- if (DT)
- DT->splitBlock(NewBB);
- if (DF)
- DF->splitBlock(NewBB);
-
- // Remember the newly constructed landing pad. The original landing pad
- // LPad is no longer a landing pad now that all unwind edges have been
- // revectored to NewBB.
- LandingPads.insert(NewBB);
- ++NumLandingPadsSplit;
- Changed = true;
- }
-
- return Changed;
-}
-
-/// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume,
-/// rethrowing any previously caught exception. This will crash horribly
-/// at runtime if there is no such exception: using unwind to throw a new
-/// exception is currently not supported.
-bool DwarfEHPrepare::LowerUnwinds() {
- SmallVector<TerminatorInst*, 16> UnwindInsts;
-
- for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
- TerminatorInst *TI = I->getTerminator();
- if (isa<UnwindInst>(TI))
- UnwindInsts.push_back(TI);
}
- if (UnwindInsts.empty()) return false;
+ if (!ExnObj)
+ ExnObj = ExtractValueInst::Create(RI->getOperand(0), 0, "exn.obj", RI);
- // Find the rewind function if we didn't already.
- if (!RewindFunction) {
- std::vector<const Type*>
- Params(1, Type::getInt8PtrTy(*Context));
- FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Context),
- Params, false);
- const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
- RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy);
- }
-
- for (SmallVectorImpl<TerminatorInst*>::iterator
- I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) {
- TerminatorInst *TI = *I;
-
- // Replace the unwind instruction with a call to _Unwind_Resume (or the
- // appropriate target equivalent) followed by an UnreachableInst.
-
- // Create the call...
- CallInst *CI = CallInst::Create(RewindFunction,
- CreateReadOfExceptionValue(TI->getParent()),
- "", TI);
- CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
- // ...followed by an UnreachableInst.
- new UnreachableInst(*Context, TI);
+ RI->eraseFromParent();
- // Nuke the unwind instruction.
- TI->eraseFromParent();
- ++NumUnwindsLowered;
+ if (EraseIVIs) {
+ if (SelIVI->use_empty())
+ SelIVI->eraseFromParent();
+ if (ExcIVI->use_empty())
+ ExcIVI->eraseFromParent();
+ if (SelLoad && SelLoad->use_empty())
+ SelLoad->eraseFromParent();
}
- return true;
+ return ExnObj;
}
-/// MoveSelectorCalls - Make sure that every call to eh.selector occurs in its
-/// own landing pad, the landing pad corresponding to the exception object.
-bool DwarfEHPrepare::MoveSelectorCalls() {
- // If the eh.selector intrinsic is not declared in the module then there is
- // nothing to do. Speed up compilation by checking for this common case.
- if (!F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_selector)))
- return false;
-
- // TODO: There is a lot of room for optimization here.
-
- bool Changed = false;
- BasicBlock *UnrBB = 0;
-
- for (Function::iterator BB = F->begin(); BB != F->end(); ++BB) {
- // If this basic block is not a landing pad then synthesize a landing pad
- // for every selector in it.
- bool SynthesizeLandingPad = !LandingPads.count(BB);
-
- for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE; ++II) {
- EHSelectorInst *SI = dyn_cast<EHSelectorInst>(II);
- // Only interested in eh.selector calls.
- if (!SI)
- continue;
-
- // Note the personality and catch-all for later use.
- Personality = cast<Constant>(SI->getOperand(2));
- CatchAll = cast<Constant>(SI->getOperand(SI->getNumOperands() - 1)
- ->stripPointerCasts());
-
- // The exception object.
- Value *Exception = SI->getOperand(1);
-
- if (!SynthesizeLandingPad) {
- // Did the exception come from unwinding to this landing pad or another?
- // If it comes from a different landing pad then we need to synthesize a
- // new landing pad for the selector.
- EHExceptionInst *EI = dyn_cast<EHExceptionInst>(Exception);
- SynthesizeLandingPad = !EI || EI->getParent() != BB;
- }
-
- if (!SynthesizeLandingPad) {
- // This is the first selector in this landing pad, and it is the landing
- // pad corresponding to the exception object. No need to do anything to
- // this selector, but any subsequent selectors in this landing pad will
- // need their own invoke in order to make them independent of this one.
- SynthesizeLandingPad = true;
- continue;
- }
-
- // Rethrow the exception and catch it again, generating a landing pad for
- // this selector to live in.
-
- // Find _Unwind_RaiseException if we didn't already.
- if (!UnwindFunction) {
- std::vector<const Type*> ArgTys(1, Type::getInt8PtrTy(*Context));
- const FunctionType *FTy =
- FunctionType::get(Type::getInt32Ty(*Context), ArgTys, true);
-
- const char *Name = "_Unwind_RaiseException";
- UnwindFunction = F->getParent()->getOrInsertFunction(Name, FTy);
- }
-
- // Create a basic block containing only an unreachable instruction if we
- // didn't already.
- if (!UnrBB) {
- UnrBB = BasicBlock::Create(*Context, "unreachable", F);
- new UnreachableInst(*Context, UnrBB);
+/// Replace resumes that are not reachable from a cleanup landing pad with
+/// unreachable and then simplify those blocks.
+size_t DwarfEHPrepare::pruneUnreachableResumes(
+ Function &Fn, SmallVectorImpl<ResumeInst *> &Resumes,
+ SmallVectorImpl<LandingPadInst *> &CleanupLPads) {
+ BitVector ResumeReachable(Resumes.size());
+ size_t ResumeIndex = 0;
+ for (auto *RI : Resumes) {
+ for (auto *LP : CleanupLPads) {
+ if (isPotentiallyReachable(LP, RI, DT)) {
+ ResumeReachable.set(ResumeIndex);
+ break;
}
-
- // Split the basic block before the selector.
- BasicBlock *NewBB = SplitBlock(BB, SI, this);
-
- // Replace the terminator with an invoke of _Unwind_RaiseException.
- BB->getTerminator()->eraseFromParent();
- InvokeInst::Create(UnwindFunction, UnrBB, NewBB, &Exception,
- 1 + &Exception, "", BB);
-
- // The split off basic block is now a landing pad.
- LandingPads.insert(NewBB);
-
- // Replace the exception argument in the selector call with a call to
- // eh.exception. This is not really necessary but it makes things more
- // regular.
- Exception = CreateExceptionValueCall(NewBB);
- SI->setOperand(1, Exception);
-
- ++NumLonelySelectors;
- Changed = true;
-
- // All instructions still in the original basic block have been scanned.
- // Move on to the next basic block.
- break;
}
+ ++ResumeIndex;
}
- return Changed;
+ // If everything is reachable, there is no change.
+ if (ResumeReachable.all())
+ return Resumes.size();
+
+ const TargetTransformInfo &TTI =
+ getAnalysis<TargetTransformInfoWrapperPass>().getTTI(Fn);
+ LLVMContext &Ctx = Fn.getContext();
+
+ // Otherwise, insert unreachable instructions and call simplifycfg.
+ size_t ResumesLeft = 0;
+ for (size_t I = 0, E = Resumes.size(); I < E; ++I) {
+ ResumeInst *RI = Resumes[I];
+ if (ResumeReachable[I]) {
+ Resumes[ResumesLeft++] = RI;
+ } else {
+ BasicBlock *BB = RI->getParent();
+ new UnreachableInst(Ctx, RI);
+ RI->eraseFromParent();
+ SimplifyCFG(BB, TTI, 1);
+ }
+ }
+ Resumes.resize(ResumesLeft);
+ return ResumesLeft;
}
-/// RectifySelectorCalls - Remove useless catch-all clauses from the ends of
-/// selectors, or correct the selector result for the presence of the catch-all
-/// if it is really needed.
-bool DwarfEHPrepare::RectifySelectorCalls() {
- // If the eh.selector intrinsic is not declared in the module then there is
- // nothing to do. Speed up compilation by checking for this common case.
- if (!F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_selector)))
- return false;
-
- bool Changed = false;
-
- for (BBSet::iterator I = LandingPads.begin(), E = LandingPads.end(); I != E;
- ++I)
- for (BasicBlock::iterator II = (*I)->begin(), IE = (*I)->end(); II != IE; )
- if (EHSelectorInst *SI = dyn_cast<EHSelectorInst>(II++)) {
- // Found a call to eh.selector. Check whether it has a catch-all in the
- // middle.
- unsigned LastIndex = 0;
- for (unsigned i = 3, e = SI->getNumOperands() - 1; i < e; ++i) {
- Value *V = SI->getOperand(i);
- if (V->stripPointerCasts() == CatchAll) {
- // A catch-all. The catch-all at the end was not needed.
- LastIndex = i;
- break;
- } else if (ConstantInt *FilterLength = dyn_cast<ConstantInt>(V)) {
- // A cleanup or a filter.
- unsigned Length = FilterLength->getZExtValue();
- if (Length == 0)
- // A cleanup - skip it.
- continue;
- if (Length == 1) {
- // A catch-all filter. Drop everything that follows.
- LastIndex = i;
- break;
- }
- // A filter, skip over the typeinfos.
- i += Length - 1;
- }
- }
-
- if (LastIndex) {
- // Drop the pointless catch-all from the end. In fact drop everything
- // after LastIndex as an optimization.
- SmallVector<Value*, 16> Args;
- Args.reserve(LastIndex);
- for (unsigned i = 1; i <= LastIndex; ++i)
- Args.push_back(SI->getOperand(i));
- CallInst *CI = CallInst::Create(SI->getOperand(0), Args.begin(),
- Args.end(), "", SI);
- CI->takeName(SI);
- SI->replaceAllUsesWith(CI);
- SI->eraseFromParent();
- ++NumSelectorsSimplified;
- } else if (!isa<ConstantInt>(CatchAll) && // Not a cleanup.
- !SI->use_empty()) {
- // Correct the selector value to return zero if the catch-all matches.
- Constant *Zero = ConstantInt::getNullValue(Type::getInt32Ty(*Context));
-
- // Create the new selector value, with placeholders instead of the
- // real operands and make everyone use it. The reason for this round
- // about approach is that the computation of the new value makes use
- // of the old value, so we can't just compute it then do RAUW.
- SelectInst *S = SelectInst::Create(ConstantInt::getFalse(*Context),
- Zero, Zero, "", II);
- SI->replaceAllUsesWith(S);
-
- // Now calculate the operands of the select.
- IRBuilder<> Builder(*I, S);
-
- // Find the eh.typeid.for intrinsic if we didn't already.
- if (!TypeIdIntrinsic)
- TypeIdIntrinsic = Intrinsic::getDeclaration(F->getParent(),
- Intrinsic::eh_typeid_for);
-
- // Obtain the id of the catch-all.
- Value *CatchAllId = Builder.CreateCall(TypeIdIntrinsic,
- ConstantExpr::getBitCast(CatchAll, Type::getInt8PtrTy(*Context)));
-
- // Compare it with the original selector result. If it matched then
- // the selector result is zero, otherwise it is the original selector.
- Value *MatchesCatchAll = Builder.CreateICmpEQ(SI, CatchAllId);
- S->setOperand(0, MatchesCatchAll);
- S->setOperand(2, SI);
- ++NumSelectorsAdjusted;
- }
-
- Changed = true;
- break;
- }
-
- return Changed;
-}
+/// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present
+/// into calls to the appropriate _Unwind_Resume function.
+bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
+ SmallVector<ResumeInst*, 16> Resumes;
+ SmallVector<LandingPadInst*, 16> CleanupLPads;
+ for (BasicBlock &BB : Fn) {
+ if (auto *RI = dyn_cast<ResumeInst>(BB.getTerminator()))
+ Resumes.push_back(RI);
+ if (auto *LP = BB.getLandingPadInst())
+ if (LP->isCleanup())
+ CleanupLPads.push_back(LP);
+ }
-/// Make sure every landing pad has a selector in it.
-bool DwarfEHPrepare::AddMissingSelectors() {
- if (!Personality)
- // We only know how to codegen invokes if there is a personality.
- // FIXME: This results in wrong code.
+ if (Resumes.empty())
return false;
- bool Changed = false;
-
- for (BBSet::iterator I = LandingPads.begin(), E = LandingPads.end(); I != E;
- ++I) {
- bool FoundSelector = false;
-
- // Check whether the landing pad already contains a call to eh.selector.
- for (BasicBlock::iterator II = (*I)->begin(), IE = (*I)->end(); II != IE;
- ++II)
- if (isa<EHSelectorInst>(II)) {
- FoundSelector = true;
- break;
- }
-
- if (FoundSelector)
- continue;
-
- // Find the eh.selector intrinsic if we didn't already.
- if (!SelectorIntrinsic)
- SelectorIntrinsic = Intrinsic::getDeclaration(F->getParent(),
- Intrinsic::eh_selector);
+ // Check the personality, don't do anything if it's funclet-based.
+ EHPersonality Pers = classifyEHPersonality(Fn.getPersonalityFn());
+ if (isFuncletEHPersonality(Pers))
+ return false;
- // Get the exception object.
- Instruction *Exception = CreateExceptionValueCall(*I);
+ LLVMContext &Ctx = Fn.getContext();
- Value *Args[3] = { Exception, Personality, CatchAll };
- CallInst *Selector = CallInst::Create(SelectorIntrinsic, Args, Args + 3);
- Selector->insertAfter(Exception);
+ size_t ResumesLeft = pruneUnreachableResumes(Fn, Resumes, CleanupLPads);
+ if (ResumesLeft == 0)
+ return true; // We pruned them all.
- ++NumLonelyLandingPads;
- Changed = true;
+ // Find the rewind function if we didn't already.
+ if (!RewindFunction) {
+ FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
+ Type::getInt8PtrTy(Ctx), false);
+ const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
+ RewindFunction = Fn.getParent()->getOrInsertFunction(RewindName, FTy);
}
- return Changed;
-}
+ // Create the basic block where the _Unwind_Resume call will live.
+ if (ResumesLeft == 1) {
+ // Instead of creating a new BB and PHI node, just append the call to
+ // _Unwind_Resume to the end of the single resume block.
+ ResumeInst *RI = Resumes.front();
+ BasicBlock *UnwindBB = RI->getParent();
+ Value *ExnObj = GetExceptionObject(RI);
-/// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from
-/// landing pads by replacing calls outside of landing pads with loads from a
-/// stack temporary. Move eh.exception calls inside landing pads to the start
-/// of the landing pad (optional, but may make things simpler for later passes).
-bool DwarfEHPrepare::MoveExceptionValueCalls() {
- // If the eh.exception intrinsic is not declared in the module then there is
- // nothing to do. Speed up compilation by checking for this common case.
- if (!ExceptionIntrinsic &&
- !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception)))
- return false;
+ // Call the _Unwind_Resume function.
+ CallInst *CI = CallInst::Create(RewindFunction, ExnObj, "", UnwindBB);
+ CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
- bool Changed = false;
-
- for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
- for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;)
- if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++))
- if (CI->getIntrinsicID() == Intrinsic::eh_exception) {
- if (!CI->use_empty()) {
- Value *ExceptionValue = CreateReadOfExceptionValue(BB);
- if (CI == ExceptionValue) {
- // The call was at the start of a landing pad - leave it alone.
- assert(LandingPads.count(BB) &&
- "Created eh.exception call outside landing pad!");
- continue;
- }
- CI->replaceAllUsesWith(ExceptionValue);
- }
- CI->eraseFromParent();
- ++NumExceptionValuesMoved;
- Changed = true;
- }
+ // We never expect _Unwind_Resume to return.
+ new UnreachableInst(Ctx, UnwindBB);
+ return true;
}
- return Changed;
-}
+ BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn);
+ PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), ResumesLeft,
+ "exn.obj", UnwindBB);
-/// FinishStackTemporaries - If we introduced a stack variable to hold the
-/// exception value then initialize it in each landing pad.
-bool DwarfEHPrepare::FinishStackTemporaries() {
- if (!ExceptionValueVar)
- // Nothing to do.
- return false;
+ // Extract the exception object from the ResumeInst and add it to the PHI node
+ // that feeds the _Unwind_Resume call.
+ for (ResumeInst *RI : Resumes) {
+ BasicBlock *Parent = RI->getParent();
+ BranchInst::Create(UnwindBB, Parent);
- bool Changed = false;
+ Value *ExnObj = GetExceptionObject(RI);
+ PN->addIncoming(ExnObj, Parent);
- // Make sure that there is a store of the exception value at the start of
- // each landing pad.
- for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end();
- LI != LE; ++LI) {
- Instruction *ExceptionValue = CreateReadOfExceptionValue(*LI);
- Instruction *Store = new StoreInst(ExceptionValue, ExceptionValueVar);
- Store->insertAfter(ExceptionValue);
- Changed = true;
+ ++NumResumesLowered;
}
- return Changed;
-}
-
-/// PromoteStackTemporaries - Turn any stack temporaries we introduced into
-/// registers if possible.
-bool DwarfEHPrepare::PromoteStackTemporaries() {
- if (ExceptionValueVar && DT && DF && isAllocaPromotable(ExceptionValueVar)) {
- // Turn the exception temporary into registers and phi nodes if possible.
- std::vector<AllocaInst*> Allocas(1, ExceptionValueVar);
- PromoteMemToReg(Allocas, *DT, *DF, *Context);
- return true;
- }
- return false;
-}
-
-/// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at
-/// the start of the basic block (unless there already is one, in which case
-/// the existing call is returned).
-Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) {
- Instruction *Start = BB->getFirstNonPHI();
- // Is this a call to eh.exception?
- if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start))
- if (CI->getIntrinsicID() == Intrinsic::eh_exception)
- // Reuse the existing call.
- return Start;
-
- // Find the eh.exception intrinsic if we didn't already.
- if (!ExceptionIntrinsic)
- ExceptionIntrinsic = Intrinsic::getDeclaration(F->getParent(),
- Intrinsic::eh_exception);
-
- // Create the call.
- return CallInst::Create(ExceptionIntrinsic, "eh.value.call", Start);
-}
-
-/// CreateValueLoad - Insert a load of the exception value stack variable
-/// (creating it if necessary) at the start of the basic block (unless
-/// there already is a load, in which case the existing load is returned).
-Instruction *DwarfEHPrepare::CreateValueLoad(BasicBlock *BB) {
- Instruction *Start = BB->getFirstNonPHI();
- // Is this a load of the exception temporary?
- if (ExceptionValueVar)
- if (LoadInst* LI = dyn_cast<LoadInst>(Start))
- if (LI->getPointerOperand() == ExceptionValueVar)
- // Reuse the existing load.
- return Start;
-
- // Create the temporary if we didn't already.
- if (!ExceptionValueVar) {
- ExceptionValueVar = new AllocaInst(PointerType::getUnqual(
- Type::getInt8Ty(*Context)), "eh.value", F->begin()->begin());
- ++NumStackTempsIntroduced;
- }
+ // Call the function.
+ CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB);
+ CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
- // Load the value.
- return new LoadInst(ExceptionValueVar, "eh.value.load", Start);
+ // We never expect _Unwind_Resume to return.
+ new UnreachableInst(Ctx, UnwindBB);
+ return true;
}
bool DwarfEHPrepare::runOnFunction(Function &Fn) {
- bool Changed = false;
-
- // Initialize internal state.
- DT = getAnalysisIfAvailable<DominatorTree>();
- DF = getAnalysisIfAvailable<DominanceFrontier>();
- ExceptionValueVar = 0;
- Personality = 0;
- CatchAll = 0;
- Context = &Fn.getContext();
- F = &Fn;
-
- // Ensure that only unwind edges end at landing pads (a landing pad is a
- // basic block where an invoke unwind edge ends).
- Changed |= NormalizeLandingPads();
-
- // Turn unwind instructions into libcalls.
- Changed |= LowerUnwinds();
-
- // Make sure that every call to eh.selector occurs in its own landing pad.
- Changed |= MoveSelectorCalls();
-
- // Remove useless catch-all clauses from the ends of selectors, or correct the
- // selector result for the presence of the catch-all if it is really needed.
- Changed |= RectifySelectorCalls();
-
- // Make sure every landing pad has a selector in it.
- Changed |= AddMissingSelectors();
-
- // Move eh.exception calls to landing pads.
- Changed |= MoveExceptionValueCalls();
-
- // Initialize any stack temporaries we introduced.
- Changed |= FinishStackTemporaries();
-
- // Turn any stack temporaries into registers if possible.
-//TODO if (!CompileFast)
-//TODO Changed |= PromoteStackTemporaries();
-
- LandingPads.clear();
-
+ assert(TM && "DWARF EH preparation requires a target machine");
+ DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ TLI = TM->getSubtargetImpl(Fn)->getTargetLowering();
+ bool Changed = InsertUnwindResumeCalls(Fn);
+ DT = nullptr;
+ TLI = nullptr;
return Changed;
}