//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "dwarfehprepare"
-#include "llvm/Function.h"
-#include "llvm/Instructions.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/Module.h"
-#include "llvm/Pass.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Analysis/Dominators.h"
#include "llvm/CodeGen/Passes.h"
-#include "llvm/MC/MCAsmInfo.h"
-#include "llvm/Support/CallSite.h"
+#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/CFG.h"
+#include "llvm/Analysis/LibCallSemantics.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/Target/TargetLowering.h"
-#include "llvm/Transforms/Utils/BasicBlockUtils.h"
-#include "llvm/Transforms/Utils/SSAUpdater.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
+#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
+#define DEBUG_TYPE "dwarfehprepare"
+
STATISTIC(NumResumesLowered, "Number of resume calls lowered");
namespace {
class DwarfEHPrepare : public FunctionPass {
const TargetMachine *TM;
- const TargetLowering *TLI;
// RewindFunction - _Unwind_Resume or the target equivalent.
Constant *RewindFunction;
+ DominatorTree *DT;
+ const TargetLowering *TLI;
+
bool InsertUnwindResumeCalls(Function &Fn);
+ Value *GetExceptionObject(ResumeInst *RI);
+ size_t
+ pruneUnreachableResumes(Function &Fn,
+ SmallVectorImpl<ResumeInst *> &Resumes,
+ SmallVectorImpl<LandingPadInst *> &CleanupLPads);
public:
static char ID; // Pass identification, replacement for typeid.
- DwarfEHPrepare(const TargetMachine *tm) :
- FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()),
- RewindFunction(0) {
- initializeDominatorTreePass(*PassRegistry::getPassRegistry());
- }
- virtual bool runOnFunction(Function &Fn);
+ // 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) {}
+
+ DwarfEHPrepare(const TargetMachine *TM)
+ : FunctionPass(ID), TM(TM), RewindFunction(nullptr), DT(nullptr),
+ TLI(nullptr) {}
- virtual void getAnalysisUsage(AnalysisUsage &AU) const { }
+ bool runOnFunction(Function &Fn) override;
- const char *getPassName() const {
+ bool doFinalization(Module &M) override {
+ RewindFunction = nullptr;
+ return false;
+ }
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+ 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);
+}
+
+void DwarfEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<TargetTransformInfoWrapperPass>();
+ AU.addRequired<DominatorTreeWrapperPass>();
+}
+
+/// 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 (!ExnObj)
+ ExnObj = ExtractValueInst::Create(RI->getOperand(0), 0, "exn.obj", RI);
-FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) {
- return new DwarfEHPrepare(tm);
+ RI->eraseFromParent();
+
+ if (EraseIVIs) {
+ if (SelIVI->use_empty())
+ SelIVI->eraseFromParent();
+ if (ExcIVI->use_empty())
+ ExcIVI->eraseFromParent();
+ if (SelLoad && SelLoad->use_empty())
+ SelLoad->eraseFromParent();
+ }
+
+ return ExnObj;
+}
+
+/// 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;
+ }
+ }
+ ++ResumeIndex;
+ }
+
+ // 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;
}
/// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present
/// into calls to the appropriate _Unwind_Resume function.
bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
- bool UsesNewEH = false;
SmallVector<ResumeInst*, 16> Resumes;
- for (Function::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
- TerminatorInst *TI = I->getTerminator();
- if (ResumeInst *RI = dyn_cast<ResumeInst>(TI))
+ SmallVector<LandingPadInst*, 16> CleanupLPads;
+ for (BasicBlock &BB : Fn) {
+ if (auto *RI = dyn_cast<ResumeInst>(BB.getTerminator()))
Resumes.push_back(RI);
- else if (InvokeInst *II = dyn_cast<InvokeInst>(TI))
- UsesNewEH = II->getUnwindDest()->isLandingPad();
+ if (auto *LP = BB.getLandingPadInst())
+ if (LP->isCleanup())
+ CleanupLPads.push_back(LP);
}
if (Resumes.empty())
- return UsesNewEH;
+ return false;
+
+ // Check the personality, don't do anything if it's for MSVC.
+ EHPersonality Pers = classifyEHPersonality(Fn.getPersonalityFn());
+ if (isMSVCEHPersonality(Pers))
+ return false;
+
+ LLVMContext &Ctx = Fn.getContext();
+
+ size_t ResumesLeft = pruneUnreachableResumes(Fn, Resumes, CleanupLPads);
+ if (ResumesLeft == 0)
+ return true; // We pruned them all.
// Find the rewind function if we didn't already.
if (!RewindFunction) {
- LLVMContext &Ctx = Resumes[0]->getContext();
FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
Type::getInt8PtrTy(Ctx), false);
const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
}
// Create the basic block where the _Unwind_Resume call will live.
- LLVMContext &Ctx = Fn.getContext();
+ 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);
+
+ // Call the _Unwind_Resume function.
+ CallInst *CI = CallInst::Create(RewindFunction, ExnObj, "", UnwindBB);
+ CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
+
+ // We never expect _Unwind_Resume to return.
+ new UnreachableInst(Ctx, UnwindBB);
+ return true;
+ }
+
BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn);
- PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), Resumes.size(),
+ PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), ResumesLeft,
"exn.obj", UnwindBB);
// Extract the exception object from the ResumeInst and add it to the PHI node
// that feeds the _Unwind_Resume call.
- for (SmallVectorImpl<ResumeInst*>::iterator
- I = Resumes.begin(), E = Resumes.end(); I != E; ++I) {
- ResumeInst *RI = *I;
- BranchInst::Create(UnwindBB, RI->getParent());
- ExtractValueInst *ExnObj = ExtractValueInst::Create(RI->getOperand(0),
- 0, "exn.obj", RI);
- PN->addIncoming(ExnObj, RI->getParent());
- RI->eraseFromParent();
+ for (ResumeInst *RI : Resumes) {
+ BasicBlock *Parent = RI->getParent();
+ BranchInst::Create(UnwindBB, Parent);
+
+ Value *ExnObj = GetExceptionObject(RI);
+ PN->addIncoming(ExnObj, Parent);
+
++NumResumesLowered;
}
}
bool DwarfEHPrepare::runOnFunction(Function &Fn) {
+ 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;
}
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