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e1c77ca37a
pointer to a dead function. To make sure it's valid, doFinalization nullptrs RewindFunction just like the constructor and so it will be found on next run. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217737 91177308-0d34-0410-b5e6-96231b3b80d8
187 lines
6.1 KiB
C++
187 lines
6.1 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/Statistic.h"
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#include "llvm/IR/CallSite.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/IntrinsicInst.h"
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#include "llvm/IR/Module.h"
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#include "llvm/MC/MCAsmInfo.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/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/SSAUpdater.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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bool InsertUnwindResumeCalls(Function &Fn);
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Value *GetExceptionObject(ResumeInst *RI);
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public:
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static char ID; // Pass identification, replacement for typeid.
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DwarfEHPrepare(const TargetMachine *TM)
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: FunctionPass(ID), TM(TM), RewindFunction(nullptr) {
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initializeDominatorTreeWrapperPassPass(*PassRegistry::getPassRegistry());
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}
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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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FunctionPass *llvm::createDwarfEHPass(const TargetMachine *TM) {
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return new DwarfEHPrepare(TM);
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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->getNumUses() == 0)
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SelIVI->eraseFromParent();
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if (ExcIVI->getNumUses() == 0)
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ExcIVI->eraseFromParent();
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if (SelLoad && SelLoad->getNumUses() == 0)
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SelLoad->eraseFromParent();
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}
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return ExnObj;
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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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for (Function::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
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TerminatorInst *TI = I->getTerminator();
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if (ResumeInst *RI = dyn_cast<ResumeInst>(TI))
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Resumes.push_back(RI);
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}
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if (Resumes.empty())
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return false;
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// Find the rewind function if we didn't already.
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const TargetLowering *TLI = TM->getSubtargetImpl()->getTargetLowering();
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if (!RewindFunction) {
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LLVMContext &Ctx = Resumes[0]->getContext();
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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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LLVMContext &Ctx = Fn.getContext();
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unsigned ResumesSize = Resumes.size();
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if (ResumesSize == 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), ResumesSize,
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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 (SmallVectorImpl<ResumeInst*>::iterator
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I = Resumes.begin(), E = Resumes.end(); I != E; ++I) {
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ResumeInst *RI = *I;
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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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bool Changed = InsertUnwindResumeCalls(Fn);
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return Changed;
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}
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