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Instead, run both EH preparation passes, and have them both ignore functions with unrecognized EH personalities. Pass delegation involved some hacky code for creating an AnalysisResolver that we don't need now. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231995 91177308-0d34-0410-b5e6-96231b3b80d8
270 lines
8.7 KiB
C++
270 lines
8.7 KiB
C++
//===-- DwarfEHPrepare - Prepare exception handling for code generation ---===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass mulches exception handling code into a form adapted to code
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// generation. Required if using dwarf exception handling.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/ADT/BitVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/CFG.h"
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#include "llvm/Analysis/LibCallSemantics.h"
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#include "llvm/Analysis/TargetTransformInfo.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Target/TargetLowering.h"
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#include "llvm/Target/TargetSubtargetInfo.h"
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#include "llvm/Transforms/Utils/Local.h"
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using namespace llvm;
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#define DEBUG_TYPE "dwarfehprepare"
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STATISTIC(NumResumesLowered, "Number of resume calls lowered");
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namespace {
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class DwarfEHPrepare : public FunctionPass {
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const TargetMachine *TM;
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// RewindFunction - _Unwind_Resume or the target equivalent.
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Constant *RewindFunction;
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DominatorTree *DT;
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const TargetLowering *TLI;
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bool InsertUnwindResumeCalls(Function &Fn);
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Value *GetExceptionObject(ResumeInst *RI);
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size_t
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pruneUnreachableResumes(Function &Fn,
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SmallVectorImpl<ResumeInst *> &Resumes,
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SmallVectorImpl<LandingPadInst *> &CleanupLPads);
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public:
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static char ID; // Pass identification, replacement for typeid.
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// INITIALIZE_TM_PASS requires a default constructor, but it isn't used in
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// practice.
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DwarfEHPrepare()
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: FunctionPass(ID), TM(nullptr), RewindFunction(nullptr), DT(nullptr),
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TLI(nullptr) {}
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DwarfEHPrepare(const TargetMachine *TM)
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: FunctionPass(ID), TM(TM), RewindFunction(nullptr), DT(nullptr),
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TLI(nullptr) {}
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bool runOnFunction(Function &Fn) override;
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bool doFinalization(Module &M) override {
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RewindFunction = nullptr;
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return false;
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override;
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const char *getPassName() const override {
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return "Exception handling preparation";
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}
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};
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} // end anonymous namespace
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char DwarfEHPrepare::ID = 0;
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INITIALIZE_TM_PASS_BEGIN(DwarfEHPrepare, "dwarfehprepare",
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"Prepare DWARF exceptions", false, false)
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INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
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INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
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INITIALIZE_TM_PASS_END(DwarfEHPrepare, "dwarfehprepare",
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"Prepare DWARF exceptions", false, false)
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FunctionPass *llvm::createDwarfEHPass(const TargetMachine *TM) {
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return new DwarfEHPrepare(TM);
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}
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void DwarfEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<TargetTransformInfoWrapperPass>();
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AU.addRequired<DominatorTreeWrapperPass>();
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}
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/// GetExceptionObject - Return the exception object from the value passed into
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/// the 'resume' instruction (typically an aggregate). Clean up any dead
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/// instructions, including the 'resume' instruction.
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Value *DwarfEHPrepare::GetExceptionObject(ResumeInst *RI) {
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Value *V = RI->getOperand(0);
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Value *ExnObj = nullptr;
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InsertValueInst *SelIVI = dyn_cast<InsertValueInst>(V);
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LoadInst *SelLoad = nullptr;
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InsertValueInst *ExcIVI = nullptr;
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bool EraseIVIs = false;
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if (SelIVI) {
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if (SelIVI->getNumIndices() == 1 && *SelIVI->idx_begin() == 1) {
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ExcIVI = dyn_cast<InsertValueInst>(SelIVI->getOperand(0));
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if (ExcIVI && isa<UndefValue>(ExcIVI->getOperand(0)) &&
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ExcIVI->getNumIndices() == 1 && *ExcIVI->idx_begin() == 0) {
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ExnObj = ExcIVI->getOperand(1);
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SelLoad = dyn_cast<LoadInst>(SelIVI->getOperand(1));
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EraseIVIs = true;
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}
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}
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}
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if (!ExnObj)
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ExnObj = ExtractValueInst::Create(RI->getOperand(0), 0, "exn.obj", RI);
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RI->eraseFromParent();
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if (EraseIVIs) {
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if (SelIVI->use_empty())
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SelIVI->eraseFromParent();
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if (ExcIVI->use_empty())
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ExcIVI->eraseFromParent();
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if (SelLoad && SelLoad->use_empty())
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SelLoad->eraseFromParent();
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}
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return ExnObj;
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}
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/// Replace resumes that are not reachable from a cleanup landing pad with
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/// unreachable and then simplify those blocks.
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size_t DwarfEHPrepare::pruneUnreachableResumes(
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Function &Fn, SmallVectorImpl<ResumeInst *> &Resumes,
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SmallVectorImpl<LandingPadInst *> &CleanupLPads) {
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BitVector ResumeReachable(Resumes.size());
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size_t ResumeIndex = 0;
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for (auto *RI : Resumes) {
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for (auto *LP : CleanupLPads) {
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if (isPotentiallyReachable(LP, RI, DT)) {
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ResumeReachable.set(ResumeIndex);
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break;
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}
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}
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++ResumeIndex;
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}
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// If everything is reachable, there is no change.
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if (ResumeReachable.all())
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return Resumes.size();
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const TargetTransformInfo &TTI =
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getAnalysis<TargetTransformInfoWrapperPass>().getTTI(Fn);
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LLVMContext &Ctx = Fn.getContext();
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// Otherwise, insert unreachable instructions and call simplifycfg.
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size_t ResumesLeft = 0;
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for (size_t I = 0, E = Resumes.size(); I < E; ++I) {
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ResumeInst *RI = Resumes[I];
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if (ResumeReachable[I]) {
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Resumes[ResumesLeft++] = RI;
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} else {
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BasicBlock *BB = RI->getParent();
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new UnreachableInst(Ctx, RI);
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RI->eraseFromParent();
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SimplifyCFG(BB, TTI, 1);
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}
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}
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Resumes.resize(ResumesLeft);
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return ResumesLeft;
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}
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/// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present
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/// into calls to the appropriate _Unwind_Resume function.
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bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
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SmallVector<ResumeInst*, 16> Resumes;
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SmallVector<LandingPadInst*, 16> CleanupLPads;
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bool FoundLP = false;
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for (BasicBlock &BB : Fn) {
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if (auto *RI = dyn_cast<ResumeInst>(BB.getTerminator()))
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Resumes.push_back(RI);
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if (auto *LP = BB.getLandingPadInst()) {
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if (LP->isCleanup())
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CleanupLPads.push_back(LP);
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// Check the personality on the first landingpad. Don't do anything if
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// it's for MSVC.
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if (!FoundLP) {
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FoundLP = true;
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EHPersonality Pers = classifyEHPersonality(LP->getPersonalityFn());
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if (isMSVCEHPersonality(Pers))
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return false;
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}
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}
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}
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if (Resumes.empty())
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return false;
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LLVMContext &Ctx = Fn.getContext();
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size_t ResumesLeft = pruneUnreachableResumes(Fn, Resumes, CleanupLPads);
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if (ResumesLeft == 0)
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return true; // We pruned them all.
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// Find the rewind function if we didn't already.
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if (!RewindFunction) {
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FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
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Type::getInt8PtrTy(Ctx), false);
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const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
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RewindFunction = Fn.getParent()->getOrInsertFunction(RewindName, FTy);
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}
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// Create the basic block where the _Unwind_Resume call will live.
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if (ResumesLeft == 1) {
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// Instead of creating a new BB and PHI node, just append the call to
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// _Unwind_Resume to the end of the single resume block.
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ResumeInst *RI = Resumes.front();
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BasicBlock *UnwindBB = RI->getParent();
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Value *ExnObj = GetExceptionObject(RI);
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// Call the _Unwind_Resume function.
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CallInst *CI = CallInst::Create(RewindFunction, ExnObj, "", UnwindBB);
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CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
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// We never expect _Unwind_Resume to return.
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new UnreachableInst(Ctx, UnwindBB);
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return true;
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}
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BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn);
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PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), ResumesLeft,
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"exn.obj", UnwindBB);
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// Extract the exception object from the ResumeInst and add it to the PHI node
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// that feeds the _Unwind_Resume call.
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for (ResumeInst *RI : Resumes) {
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BasicBlock *Parent = RI->getParent();
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BranchInst::Create(UnwindBB, Parent);
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Value *ExnObj = GetExceptionObject(RI);
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PN->addIncoming(ExnObj, Parent);
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++NumResumesLowered;
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}
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// Call the function.
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CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB);
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CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
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// We never expect _Unwind_Resume to return.
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new UnreachableInst(Ctx, UnwindBB);
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return true;
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}
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bool DwarfEHPrepare::runOnFunction(Function &Fn) {
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assert(TM && "DWARF EH preparation requires a target machine");
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DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
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TLI = TM->getSubtargetImpl(Fn)->getTargetLowering();
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bool Changed = InsertUnwindResumeCalls(Fn);
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DT = nullptr;
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TLI = nullptr;
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return Changed;
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}
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