mirror of
https://github.com/c64scene-ar/llvm-6502.git
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90b8e791ac
This doesn't pass 'ninja check-llvm' for me. Lots of tests, including the ones updated, fail with crashes and other explosions. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229952 91177308-0d34-0410-b5e6-96231b3b80d8
391 lines
15 KiB
C++
391 lines
15 KiB
C++
//===-- WinEHPrepare - 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 lowers LLVM IR exception handling into something closer to what the
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// backend wants. It snifs the personality function to see which kind of
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// preparation is necessary. If the personality function uses the Itanium LSDA,
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// this pass delegates to the DWARF EH preparation pass.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/Analysis/LibCallSemantics.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/IRBuilder.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/IR/PatternMatch.h"
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#include "llvm/Pass.h"
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#include "llvm/Transforms/Utils/Cloning.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include <memory>
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using namespace llvm;
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using namespace llvm::PatternMatch;
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#define DEBUG_TYPE "winehprepare"
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namespace {
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class WinEHPrepare : public FunctionPass {
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std::unique_ptr<FunctionPass> DwarfPrepare;
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public:
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static char ID; // Pass identification, replacement for typeid.
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WinEHPrepare(const TargetMachine *TM = nullptr)
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: FunctionPass(ID), DwarfPrepare(createDwarfEHPass(TM)) {}
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bool runOnFunction(Function &Fn) override;
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bool doFinalization(Module &M) override;
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void getAnalysisUsage(AnalysisUsage &AU) const override;
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const char *getPassName() const override {
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return "Windows exception handling preparation";
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}
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private:
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bool prepareCPPEHHandlers(Function &F,
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SmallVectorImpl<LandingPadInst *> &LPads);
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bool outlineCatchHandler(Function *SrcFn, Constant *SelectorType,
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LandingPadInst *LPad, StructType *EHDataStructTy);
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};
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class WinEHCatchDirector : public CloningDirector {
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public:
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WinEHCatchDirector(LandingPadInst *LPI, Value *Selector, Value *EHObj)
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: LPI(LPI), CurrentSelector(Selector->stripPointerCasts()), EHObj(EHObj),
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SelectorIDType(Type::getInt32Ty(LPI->getContext())),
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Int8PtrType(Type::getInt8PtrTy(LPI->getContext())) {}
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CloningAction handleInstruction(ValueToValueMapTy &VMap,
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const Instruction *Inst,
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BasicBlock *NewBB) override;
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private:
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LandingPadInst *LPI;
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Value *CurrentSelector;
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Value *EHObj;
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Type *SelectorIDType;
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Type *Int8PtrType;
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const Value *ExtractedEHPtr;
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const Value *ExtractedSelector;
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const Value *EHPtrStoreAddr;
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const Value *SelectorStoreAddr;
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};
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} // end anonymous namespace
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char WinEHPrepare::ID = 0;
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INITIALIZE_TM_PASS(WinEHPrepare, "winehprepare", "Prepare Windows exceptions",
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false, false)
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FunctionPass *llvm::createWinEHPass(const TargetMachine *TM) {
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return new WinEHPrepare(TM);
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}
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static bool isMSVCPersonality(EHPersonality Pers) {
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return Pers == EHPersonality::MSVC_Win64SEH ||
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Pers == EHPersonality::MSVC_CXX;
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}
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bool WinEHPrepare::runOnFunction(Function &Fn) {
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SmallVector<LandingPadInst *, 4> LPads;
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SmallVector<ResumeInst *, 4> Resumes;
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for (BasicBlock &BB : Fn) {
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if (auto *LP = BB.getLandingPadInst())
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LPads.push_back(LP);
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if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
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Resumes.push_back(Resume);
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}
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// No need to prepare functions that lack landing pads.
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if (LPads.empty())
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return false;
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// Classify the personality to see what kind of preparation we need.
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EHPersonality Pers = classifyEHPersonality(LPads.back()->getPersonalityFn());
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// Delegate through to the DWARF pass if this is unrecognized.
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if (!isMSVCPersonality(Pers))
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return DwarfPrepare->runOnFunction(Fn);
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// FIXME: This only returns true if the C++ EH handlers were outlined.
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// When that code is complete, it should always return whatever
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// prepareCPPEHHandlers returns.
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if (Pers == EHPersonality::MSVC_CXX && prepareCPPEHHandlers(Fn, LPads))
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return true;
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// FIXME: SEH Cleanups are unimplemented. Replace them with unreachable.
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if (Resumes.empty())
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return false;
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for (ResumeInst *Resume : Resumes) {
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IRBuilder<>(Resume).CreateUnreachable();
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Resume->eraseFromParent();
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}
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return true;
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}
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bool WinEHPrepare::doFinalization(Module &M) {
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return DwarfPrepare->doFinalization(M);
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}
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void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
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DwarfPrepare->getAnalysisUsage(AU);
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}
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bool WinEHPrepare::prepareCPPEHHandlers(
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Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
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// FIXME: Find all frame variable references in the handlers
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// to populate the structure elements.
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SmallVector<Type *, 2> AllocStructTys;
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AllocStructTys.push_back(Type::getInt32Ty(F.getContext())); // EH state
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AllocStructTys.push_back(Type::getInt8PtrTy(F.getContext())); // EH object
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StructType *EHDataStructTy =
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StructType::create(F.getContext(), AllocStructTys,
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"struct." + F.getName().str() + ".ehdata");
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bool HandlersOutlined = false;
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for (LandingPadInst *LPad : LPads) {
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// Look for evidence that this landingpad has already been processed.
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bool LPadHasActionList = false;
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BasicBlock *LPadBB = LPad->getParent();
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for (Instruction &Inst : LPadBB->getInstList()) {
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// FIXME: Make this an intrinsic.
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if (auto *Call = dyn_cast<CallInst>(&Inst))
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if (Call->getCalledFunction()->getName() == "llvm.eh.actions") {
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LPadHasActionList = true;
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break;
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}
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}
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// If we've already outlined the handlers for this landingpad,
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// there's nothing more to do here.
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if (LPadHasActionList)
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continue;
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for (unsigned Idx = 0, NumClauses = LPad->getNumClauses(); Idx < NumClauses;
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++Idx) {
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if (LPad->isCatch(Idx))
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HandlersOutlined =
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outlineCatchHandler(&F, LPad->getClause(Idx), LPad, EHDataStructTy);
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} // End for each clause
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} // End for each landingpad
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return HandlersOutlined;
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}
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bool WinEHPrepare::outlineCatchHandler(Function *SrcFn, Constant *SelectorType,
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LandingPadInst *LPad,
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StructType *EHDataStructTy) {
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Module *M = SrcFn->getParent();
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LLVMContext &Context = M->getContext();
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// Create a new function to receive the handler contents.
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Type *Int8PtrType = Type::getInt8PtrTy(Context);
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std::vector<Type *> ArgTys;
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ArgTys.push_back(Int8PtrType);
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ArgTys.push_back(Int8PtrType);
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FunctionType *FnType = FunctionType::get(Int8PtrType, ArgTys, false);
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Function *CatchHandler = Function::Create(
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FnType, GlobalVariable::ExternalLinkage, SrcFn->getName() + ".catch", M);
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// Generate a standard prolog to setup the frame recovery structure.
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IRBuilder<> Builder(Context);
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BasicBlock *Entry = BasicBlock::Create(Context, "catch.entry");
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CatchHandler->getBasicBlockList().push_front(Entry);
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Builder.SetInsertPoint(Entry);
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Builder.SetCurrentDebugLocation(LPad->getDebugLoc());
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// The outlined handler will be called with the parent's frame pointer as
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// its second argument. To enable the handler to access variables from
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// the parent frame, we use that pointer to get locate a special block
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// of memory that was allocated using llvm.eh.allocateframe for this
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// purpose. During the outlining process we will determine which frame
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// variables are used in handlers and create a structure that maps these
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// variables into the frame allocation block.
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//
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// The frame allocation block also contains an exception state variable
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// used by the runtime and a pointer to the exception object pointer
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// which will be filled in by the runtime for use in the handler.
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Function *RecoverFrameFn =
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Intrinsic::getDeclaration(M, Intrinsic::framerecover);
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Value *RecoverArgs[] = {Builder.CreateBitCast(SrcFn, Int8PtrType, ""),
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&(CatchHandler->getArgumentList().back())};
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CallInst *EHAlloc =
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Builder.CreateCall(RecoverFrameFn, RecoverArgs, "eh.alloc");
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Value *EHData =
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Builder.CreateBitCast(EHAlloc, EHDataStructTy->getPointerTo(), "ehdata");
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Value *EHObjPtr =
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Builder.CreateConstInBoundsGEP2_32(EHData, 0, 1, "eh.obj.ptr");
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// This will give us a raw pointer to the exception object, which
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// corresponds to the formal parameter of the catch statement. If the
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// handler uses this object, we will generate code during the outlining
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// process to cast the pointer to the appropriate type and deference it
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// as necessary. The un-outlined landing pad code represents the
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// exception object as the result of the llvm.eh.begincatch call.
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Value *EHObj = Builder.CreateLoad(EHObjPtr, false, "eh.obj");
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ValueToValueMapTy VMap;
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// FIXME: Map other values referenced in the filter handler.
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WinEHCatchDirector Director(LPad, SelectorType, EHObj);
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SmallVector<ReturnInst *, 8> Returns;
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ClonedCodeInfo InlinedFunctionInfo;
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BasicBlock::iterator II = LPad;
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CloneAndPruneIntoFromInst(CatchHandler, SrcFn, ++II, VMap,
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/*ModuleLevelChanges=*/false, Returns, "",
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&InlinedFunctionInfo,
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SrcFn->getParent()->getDataLayout(), &Director);
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// Move all the instructions in the first cloned block into our entry block.
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BasicBlock *FirstClonedBB = std::next(Function::iterator(Entry));
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Entry->getInstList().splice(Entry->end(), FirstClonedBB->getInstList());
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FirstClonedBB->eraseFromParent();
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return true;
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}
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CloningDirector::CloningAction WinEHCatchDirector::handleInstruction(
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ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
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// Intercept instructions which extract values from the landing pad aggregate.
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if (auto *Extract = dyn_cast<ExtractValueInst>(Inst)) {
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if (Extract->getAggregateOperand() == LPI) {
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assert(Extract->getNumIndices() == 1 &&
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"Unexpected operation: extracting both landing pad values");
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assert((*(Extract->idx_begin()) == 0 || *(Extract->idx_begin()) == 1) &&
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"Unexpected operation: extracting an unknown landing pad element");
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if (*(Extract->idx_begin()) == 0) {
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// Element 0 doesn't directly corresponds to anything in the WinEH scheme.
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// It will be stored to a memory location, then later loaded and finally
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// the loaded value will be used as the argument to an llvm.eh.begincatch
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// call. We're tracking it here so that we can skip the store and load.
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ExtractedEHPtr = Inst;
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} else {
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// Element 1 corresponds to the filter selector. We'll map it to 1 for
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// matching purposes, but it will also probably be stored to memory and
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// reloaded, so we need to track the instuction so that we can map the
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// loaded value too.
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VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
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ExtractedSelector = Inst;
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}
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// Tell the caller not to clone this instruction.
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return CloningDirector::SkipInstruction;
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}
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// Other extract value instructions just get cloned.
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return CloningDirector::CloneInstruction;
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}
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if (auto *Store = dyn_cast<StoreInst>(Inst)) {
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// Look for and suppress stores of the extracted landingpad values.
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const Value *StoredValue = Store->getValueOperand();
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if (StoredValue == ExtractedEHPtr) {
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EHPtrStoreAddr = Store->getPointerOperand();
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return CloningDirector::SkipInstruction;
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}
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if (StoredValue == ExtractedSelector) {
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SelectorStoreAddr = Store->getPointerOperand();
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return CloningDirector::SkipInstruction;
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}
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// Any other store just gets cloned.
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return CloningDirector::CloneInstruction;
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}
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if (auto *Load = dyn_cast<LoadInst>(Inst)) {
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// Look for loads of (previously suppressed) landingpad values.
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// The EHPtr load can be ignored (it should only be used as
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// an argument to llvm.eh.begincatch), but the selector value
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// needs to be mapped to a constant value of 1 to be used to
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// simplify the branching to always flow to the current handler.
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const Value *LoadAddr = Load->getPointerOperand();
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if (LoadAddr == EHPtrStoreAddr) {
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VMap[Inst] = UndefValue::get(Int8PtrType);
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return CloningDirector::SkipInstruction;
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}
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if (LoadAddr == SelectorStoreAddr) {
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VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
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return CloningDirector::SkipInstruction;
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}
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// Any other loads just get cloned.
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return CloningDirector::CloneInstruction;
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}
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if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>())) {
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// The argument to the call is some form of the first element of the
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// landingpad aggregate value, but that doesn't matter. It isn't used
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// here.
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// The return value of this instruction, however, is used to access the
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// EH object pointer. We have generated an instruction to get that value
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// from the EH alloc block, so we can just map to that here.
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VMap[Inst] = EHObj;
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return CloningDirector::SkipInstruction;
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}
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if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>())) {
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auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
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// It might be interesting to track whether or not we are inside a catch
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// function, but that might make the algorithm more brittle than it needs
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// to be.
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// The end catch call can occur in one of two places: either in a
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// landingpad
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// block that is part of the catch handlers exception mechanism, or at the
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// end of the catch block. If it occurs in a landing pad, we must skip it
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// and continue so that the landing pad gets cloned.
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// FIXME: This case isn't fully supported yet and shouldn't turn up in any
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// of the test cases until it is.
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if (IntrinCall->getParent()->isLandingPad())
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return CloningDirector::SkipInstruction;
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// If an end catch occurs anywhere else the next instruction should be an
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// unconditional branch instruction that we want to replace with a return
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// to the the address of the branch target.
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const BasicBlock *EndCatchBB = IntrinCall->getParent();
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const TerminatorInst *Terminator = EndCatchBB->getTerminator();
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const BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
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assert(Branch && Branch->isUnconditional());
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assert(std::next(BasicBlock::const_iterator(IntrinCall)) ==
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BasicBlock::const_iterator(Branch));
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ReturnInst::Create(NewBB->getContext(),
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BlockAddress::get(Branch->getSuccessor(0)), NewBB);
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// We just added a terminator to the cloned block.
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// Tell the caller to stop processing the current basic block so that
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// the branch instruction will be skipped.
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return CloningDirector::StopCloningBB;
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}
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if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>())) {
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auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
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Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
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// This causes a replacement that will collapse the landing pad CFG based
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// on the filter function we intend to match.
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if (Selector == CurrentSelector)
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VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
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else
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VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
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// Tell the caller not to clone this instruction.
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return CloningDirector::SkipInstruction;
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}
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// Continue with the default cloning behavior.
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return CloningDirector::CloneInstruction;
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}
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