1334 lines
53 KiB
C++
1334 lines
53 KiB
C++
//===--- CGVTables.cpp - Emit LLVM Code for C++ vtables -------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This contains code dealing with C++ code generation of virtual tables.
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//
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//===----------------------------------------------------------------------===//
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#include "CGCXXABI.h"
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#include "CodeGenFunction.h"
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#include "CodeGenModule.h"
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#include "clang/AST/Attr.h"
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#include "clang/AST/CXXInheritance.h"
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#include "clang/AST/RecordLayout.h"
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#include "clang/Basic/CodeGenOptions.h"
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#include "clang/CodeGen/CGFunctionInfo.h"
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#include "clang/CodeGen/ConstantInitBuilder.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/Support/Format.h"
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#include "llvm/Transforms/Utils/Cloning.h"
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#include <algorithm>
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#include <cstdio>
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using namespace clang;
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using namespace CodeGen;
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CodeGenVTables::CodeGenVTables(CodeGenModule &CGM)
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: CGM(CGM), VTContext(CGM.getContext().getVTableContext()) {}
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llvm::Constant *CodeGenModule::GetAddrOfThunk(StringRef Name, llvm::Type *FnTy,
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GlobalDecl GD) {
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return GetOrCreateLLVMFunction(Name, FnTy, GD, /*ForVTable=*/true,
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/*DontDefer=*/true, /*IsThunk=*/true);
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}
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static void setThunkProperties(CodeGenModule &CGM, const ThunkInfo &Thunk,
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llvm::Function *ThunkFn, bool ForVTable,
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GlobalDecl GD) {
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CGM.setFunctionLinkage(GD, ThunkFn);
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CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD,
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!Thunk.Return.isEmpty());
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// Set the right visibility.
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CGM.setGVProperties(ThunkFn, GD);
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if (!CGM.getCXXABI().exportThunk()) {
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ThunkFn->setDLLStorageClass(llvm::GlobalValue::DefaultStorageClass);
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ThunkFn->setDSOLocal(true);
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}
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if (CGM.supportsCOMDAT() && ThunkFn->isWeakForLinker())
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ThunkFn->setComdat(CGM.getModule().getOrInsertComdat(ThunkFn->getName()));
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}
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#ifndef NDEBUG
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static bool similar(const ABIArgInfo &infoL, CanQualType typeL,
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const ABIArgInfo &infoR, CanQualType typeR) {
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return (infoL.getKind() == infoR.getKind() &&
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(typeL == typeR ||
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(isa<PointerType>(typeL) && isa<PointerType>(typeR)) ||
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(isa<ReferenceType>(typeL) && isa<ReferenceType>(typeR))));
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}
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#endif
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static RValue PerformReturnAdjustment(CodeGenFunction &CGF,
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QualType ResultType, RValue RV,
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const ThunkInfo &Thunk) {
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// Emit the return adjustment.
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bool NullCheckValue = !ResultType->isReferenceType();
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llvm::BasicBlock *AdjustNull = nullptr;
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llvm::BasicBlock *AdjustNotNull = nullptr;
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llvm::BasicBlock *AdjustEnd = nullptr;
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llvm::Value *ReturnValue = RV.getScalarVal();
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if (NullCheckValue) {
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AdjustNull = CGF.createBasicBlock("adjust.null");
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AdjustNotNull = CGF.createBasicBlock("adjust.notnull");
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AdjustEnd = CGF.createBasicBlock("adjust.end");
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llvm::Value *IsNull = CGF.Builder.CreateIsNull(ReturnValue);
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CGF.Builder.CreateCondBr(IsNull, AdjustNull, AdjustNotNull);
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CGF.EmitBlock(AdjustNotNull);
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}
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auto ClassDecl = ResultType->getPointeeType()->getAsCXXRecordDecl();
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auto ClassAlign = CGF.CGM.getClassPointerAlignment(ClassDecl);
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ReturnValue = CGF.CGM.getCXXABI().performReturnAdjustment(CGF,
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Address(ReturnValue, ClassAlign),
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Thunk.Return);
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if (NullCheckValue) {
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CGF.Builder.CreateBr(AdjustEnd);
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CGF.EmitBlock(AdjustNull);
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CGF.Builder.CreateBr(AdjustEnd);
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CGF.EmitBlock(AdjustEnd);
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llvm::PHINode *PHI = CGF.Builder.CreatePHI(ReturnValue->getType(), 2);
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PHI->addIncoming(ReturnValue, AdjustNotNull);
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PHI->addIncoming(llvm::Constant::getNullValue(ReturnValue->getType()),
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AdjustNull);
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ReturnValue = PHI;
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}
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return RValue::get(ReturnValue);
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}
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/// This function clones a function's DISubprogram node and enters it into
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/// a value map with the intent that the map can be utilized by the cloner
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/// to short-circuit Metadata node mapping.
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/// Furthermore, the function resolves any DILocalVariable nodes referenced
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/// by dbg.value intrinsics so they can be properly mapped during cloning.
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static void resolveTopLevelMetadata(llvm::Function *Fn,
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llvm::ValueToValueMapTy &VMap) {
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// Clone the DISubprogram node and put it into the Value map.
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auto *DIS = Fn->getSubprogram();
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if (!DIS)
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return;
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auto *NewDIS = DIS->replaceWithDistinct(DIS->clone());
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VMap.MD()[DIS].reset(NewDIS);
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// Find all llvm.dbg.declare intrinsics and resolve the DILocalVariable nodes
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// they are referencing.
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for (auto &BB : Fn->getBasicBlockList()) {
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for (auto &I : BB) {
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if (auto *DII = dyn_cast<llvm::DbgVariableIntrinsic>(&I)) {
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auto *DILocal = DII->getVariable();
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if (!DILocal->isResolved())
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DILocal->resolve();
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}
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}
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}
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}
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// This function does roughly the same thing as GenerateThunk, but in a
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// very different way, so that va_start and va_end work correctly.
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// FIXME: This function assumes "this" is the first non-sret LLVM argument of
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// a function, and that there is an alloca built in the entry block
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// for all accesses to "this".
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// FIXME: This function assumes there is only one "ret" statement per function.
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// FIXME: Cloning isn't correct in the presence of indirect goto!
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// FIXME: This implementation of thunks bloats codesize by duplicating the
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// function definition. There are alternatives:
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// 1. Add some sort of stub support to LLVM for cases where we can
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// do a this adjustment, then a sibcall.
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// 2. We could transform the definition to take a va_list instead of an
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// actual variable argument list, then have the thunks (including a
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// no-op thunk for the regular definition) call va_start/va_end.
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// There's a bit of per-call overhead for this solution, but it's
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// better for codesize if the definition is long.
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llvm::Function *
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CodeGenFunction::GenerateVarArgsThunk(llvm::Function *Fn,
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const CGFunctionInfo &FnInfo,
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GlobalDecl GD, const ThunkInfo &Thunk) {
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const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
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const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
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QualType ResultType = FPT->getReturnType();
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// Get the original function
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assert(FnInfo.isVariadic());
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llvm::Type *Ty = CGM.getTypes().GetFunctionType(FnInfo);
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llvm::Value *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
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llvm::Function *BaseFn = cast<llvm::Function>(Callee);
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// Cloning can't work if we don't have a definition. The Microsoft ABI may
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// require thunks when a definition is not available. Emit an error in these
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// cases.
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if (!MD->isDefined()) {
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CGM.ErrorUnsupported(MD, "return-adjusting thunk with variadic arguments");
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return Fn;
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}
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assert(!BaseFn->isDeclaration() && "cannot clone undefined variadic method");
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// Clone to thunk.
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llvm::ValueToValueMapTy VMap;
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// We are cloning a function while some Metadata nodes are still unresolved.
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// Ensure that the value mapper does not encounter any of them.
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resolveTopLevelMetadata(BaseFn, VMap);
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llvm::Function *NewFn = llvm::CloneFunction(BaseFn, VMap);
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Fn->replaceAllUsesWith(NewFn);
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NewFn->takeName(Fn);
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Fn->eraseFromParent();
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Fn = NewFn;
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// "Initialize" CGF (minimally).
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CurFn = Fn;
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// Get the "this" value
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llvm::Function::arg_iterator AI = Fn->arg_begin();
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if (CGM.ReturnTypeUsesSRet(FnInfo))
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++AI;
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// Find the first store of "this", which will be to the alloca associated
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// with "this".
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Address ThisPtr(&*AI, CGM.getClassPointerAlignment(MD->getParent()));
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llvm::BasicBlock *EntryBB = &Fn->front();
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llvm::BasicBlock::iterator ThisStore =
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std::find_if(EntryBB->begin(), EntryBB->end(), [&](llvm::Instruction &I) {
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return isa<llvm::StoreInst>(I) &&
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I.getOperand(0) == ThisPtr.getPointer();
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});
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assert(ThisStore != EntryBB->end() &&
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"Store of this should be in entry block?");
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// Adjust "this", if necessary.
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Builder.SetInsertPoint(&*ThisStore);
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llvm::Value *AdjustedThisPtr =
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CGM.getCXXABI().performThisAdjustment(*this, ThisPtr, Thunk.This);
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AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr,
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ThisStore->getOperand(0)->getType());
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ThisStore->setOperand(0, AdjustedThisPtr);
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if (!Thunk.Return.isEmpty()) {
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// Fix up the returned value, if necessary.
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for (llvm::BasicBlock &BB : *Fn) {
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llvm::Instruction *T = BB.getTerminator();
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if (isa<llvm::ReturnInst>(T)) {
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RValue RV = RValue::get(T->getOperand(0));
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T->eraseFromParent();
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Builder.SetInsertPoint(&BB);
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RV = PerformReturnAdjustment(*this, ResultType, RV, Thunk);
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Builder.CreateRet(RV.getScalarVal());
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break;
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}
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}
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}
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return Fn;
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}
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void CodeGenFunction::StartThunk(llvm::Function *Fn, GlobalDecl GD,
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const CGFunctionInfo &FnInfo,
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bool IsUnprototyped) {
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assert(!CurGD.getDecl() && "CurGD was already set!");
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CurGD = GD;
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CurFuncIsThunk = true;
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// Build FunctionArgs.
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const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
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QualType ThisType = MD->getThisType();
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QualType ResultType;
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if (IsUnprototyped)
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ResultType = CGM.getContext().VoidTy;
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else if (CGM.getCXXABI().HasThisReturn(GD))
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ResultType = ThisType;
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else if (CGM.getCXXABI().hasMostDerivedReturn(GD))
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ResultType = CGM.getContext().VoidPtrTy;
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else
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ResultType = MD->getType()->castAs<FunctionProtoType>()->getReturnType();
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FunctionArgList FunctionArgs;
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// Create the implicit 'this' parameter declaration.
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CGM.getCXXABI().buildThisParam(*this, FunctionArgs);
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// Add the rest of the parameters, if we have a prototype to work with.
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if (!IsUnprototyped) {
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FunctionArgs.append(MD->param_begin(), MD->param_end());
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if (isa<CXXDestructorDecl>(MD))
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CGM.getCXXABI().addImplicitStructorParams(*this, ResultType,
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FunctionArgs);
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}
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// Start defining the function.
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auto NL = ApplyDebugLocation::CreateEmpty(*this);
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StartFunction(GlobalDecl(), ResultType, Fn, FnInfo, FunctionArgs,
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MD->getLocation());
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// Create a scope with an artificial location for the body of this function.
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auto AL = ApplyDebugLocation::CreateArtificial(*this);
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// Since we didn't pass a GlobalDecl to StartFunction, do this ourselves.
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CGM.getCXXABI().EmitInstanceFunctionProlog(*this);
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CXXThisValue = CXXABIThisValue;
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CurCodeDecl = MD;
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CurFuncDecl = MD;
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}
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void CodeGenFunction::FinishThunk() {
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// Clear these to restore the invariants expected by
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// StartFunction/FinishFunction.
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CurCodeDecl = nullptr;
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CurFuncDecl = nullptr;
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FinishFunction();
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}
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void CodeGenFunction::EmitCallAndReturnForThunk(llvm::FunctionCallee Callee,
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const ThunkInfo *Thunk,
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bool IsUnprototyped) {
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assert(isa<CXXMethodDecl>(CurGD.getDecl()) &&
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"Please use a new CGF for this thunk");
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const CXXMethodDecl *MD = cast<CXXMethodDecl>(CurGD.getDecl());
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// Adjust the 'this' pointer if necessary
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llvm::Value *AdjustedThisPtr =
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Thunk ? CGM.getCXXABI().performThisAdjustment(
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*this, LoadCXXThisAddress(), Thunk->This)
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: LoadCXXThis();
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// If perfect forwarding is required a variadic method, a method using
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// inalloca, or an unprototyped thunk, use musttail. Emit an error if this
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// thunk requires a return adjustment, since that is impossible with musttail.
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if (CurFnInfo->usesInAlloca() || CurFnInfo->isVariadic() || IsUnprototyped) {
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if (Thunk && !Thunk->Return.isEmpty()) {
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if (IsUnprototyped)
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CGM.ErrorUnsupported(
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MD, "return-adjusting thunk with incomplete parameter type");
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else if (CurFnInfo->isVariadic())
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llvm_unreachable("shouldn't try to emit musttail return-adjusting "
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"thunks for variadic functions");
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else
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CGM.ErrorUnsupported(
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MD, "non-trivial argument copy for return-adjusting thunk");
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}
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EmitMustTailThunk(CurGD, AdjustedThisPtr, Callee);
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return;
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}
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// Start building CallArgs.
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CallArgList CallArgs;
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QualType ThisType = MD->getThisType();
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CallArgs.add(RValue::get(AdjustedThisPtr), ThisType);
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if (isa<CXXDestructorDecl>(MD))
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CGM.getCXXABI().adjustCallArgsForDestructorThunk(*this, CurGD, CallArgs);
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#ifndef NDEBUG
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unsigned PrefixArgs = CallArgs.size() - 1;
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#endif
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// Add the rest of the arguments.
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for (const ParmVarDecl *PD : MD->parameters())
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EmitDelegateCallArg(CallArgs, PD, SourceLocation());
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const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
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#ifndef NDEBUG
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const CGFunctionInfo &CallFnInfo = CGM.getTypes().arrangeCXXMethodCall(
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CallArgs, FPT, RequiredArgs::forPrototypePlus(FPT, 1), PrefixArgs);
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assert(CallFnInfo.getRegParm() == CurFnInfo->getRegParm() &&
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CallFnInfo.isNoReturn() == CurFnInfo->isNoReturn() &&
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CallFnInfo.getCallingConvention() == CurFnInfo->getCallingConvention());
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assert(isa<CXXDestructorDecl>(MD) || // ignore dtor return types
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similar(CallFnInfo.getReturnInfo(), CallFnInfo.getReturnType(),
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CurFnInfo->getReturnInfo(), CurFnInfo->getReturnType()));
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assert(CallFnInfo.arg_size() == CurFnInfo->arg_size());
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for (unsigned i = 0, e = CurFnInfo->arg_size(); i != e; ++i)
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assert(similar(CallFnInfo.arg_begin()[i].info,
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CallFnInfo.arg_begin()[i].type,
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CurFnInfo->arg_begin()[i].info,
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CurFnInfo->arg_begin()[i].type));
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#endif
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// Determine whether we have a return value slot to use.
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QualType ResultType = CGM.getCXXABI().HasThisReturn(CurGD)
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? ThisType
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: CGM.getCXXABI().hasMostDerivedReturn(CurGD)
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? CGM.getContext().VoidPtrTy
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: FPT->getReturnType();
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ReturnValueSlot Slot;
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if (!ResultType->isVoidType() &&
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(CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect ||
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hasAggregateEvaluationKind(ResultType)))
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Slot = ReturnValueSlot(ReturnValue, ResultType.isVolatileQualified(),
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/*IsUnused=*/false, /*IsExternallyDestructed=*/true);
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// Now emit our call.
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llvm::CallBase *CallOrInvoke;
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RValue RV = EmitCall(*CurFnInfo, CGCallee::forDirect(Callee, CurGD), Slot,
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CallArgs, &CallOrInvoke);
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// Consider return adjustment if we have ThunkInfo.
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if (Thunk && !Thunk->Return.isEmpty())
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RV = PerformReturnAdjustment(*this, ResultType, RV, *Thunk);
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else if (llvm::CallInst* Call = dyn_cast<llvm::CallInst>(CallOrInvoke))
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Call->setTailCallKind(llvm::CallInst::TCK_Tail);
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// Emit return.
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if (!ResultType->isVoidType() && Slot.isNull())
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CGM.getCXXABI().EmitReturnFromThunk(*this, RV, ResultType);
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// Disable the final ARC autorelease.
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AutoreleaseResult = false;
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FinishThunk();
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}
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void CodeGenFunction::EmitMustTailThunk(GlobalDecl GD,
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llvm::Value *AdjustedThisPtr,
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llvm::FunctionCallee Callee) {
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// Emitting a musttail call thunk doesn't use any of the CGCall.cpp machinery
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// to translate AST arguments into LLVM IR arguments. For thunks, we know
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// that the caller prototype more or less matches the callee prototype with
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// the exception of 'this'.
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SmallVector<llvm::Value *, 8> Args;
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for (llvm::Argument &A : CurFn->args())
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Args.push_back(&A);
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// Set the adjusted 'this' pointer.
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const ABIArgInfo &ThisAI = CurFnInfo->arg_begin()->info;
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if (ThisAI.isDirect()) {
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const ABIArgInfo &RetAI = CurFnInfo->getReturnInfo();
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int ThisArgNo = RetAI.isIndirect() && !RetAI.isSRetAfterThis() ? 1 : 0;
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llvm::Type *ThisType = Args[ThisArgNo]->getType();
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if (ThisType != AdjustedThisPtr->getType())
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AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, ThisType);
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Args[ThisArgNo] = AdjustedThisPtr;
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} else {
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assert(ThisAI.isInAlloca() && "this is passed directly or inalloca");
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Address ThisAddr = GetAddrOfLocalVar(CXXABIThisDecl);
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llvm::Type *ThisType = ThisAddr.getElementType();
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if (ThisType != AdjustedThisPtr->getType())
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AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, ThisType);
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Builder.CreateStore(AdjustedThisPtr, ThisAddr);
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}
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// Emit the musttail call manually. Even if the prologue pushed cleanups, we
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// don't actually want to run them.
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llvm::CallInst *Call = Builder.CreateCall(Callee, Args);
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Call->setTailCallKind(llvm::CallInst::TCK_MustTail);
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// Apply the standard set of call attributes.
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unsigned CallingConv;
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llvm::AttributeList Attrs;
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CGM.ConstructAttributeList(Callee.getCallee()->getName(), *CurFnInfo, GD,
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Attrs, CallingConv, /*AttrOnCallSite=*/true);
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Call->setAttributes(Attrs);
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Call->setCallingConv(static_cast<llvm::CallingConv::ID>(CallingConv));
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if (Call->getType()->isVoidTy())
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Builder.CreateRetVoid();
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else
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Builder.CreateRet(Call);
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// Finish the function to maintain CodeGenFunction invariants.
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// FIXME: Don't emit unreachable code.
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EmitBlock(createBasicBlock());
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FinishThunk();
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}
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void CodeGenFunction::generateThunk(llvm::Function *Fn,
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const CGFunctionInfo &FnInfo, GlobalDecl GD,
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const ThunkInfo &Thunk,
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bool IsUnprototyped) {
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StartThunk(Fn, GD, FnInfo, IsUnprototyped);
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// Create a scope with an artificial location for the body of this function.
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auto AL = ApplyDebugLocation::CreateArtificial(*this);
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|
|
// Get our callee. Use a placeholder type if this method is unprototyped so
|
|
// that CodeGenModule doesn't try to set attributes.
|
|
llvm::Type *Ty;
|
|
if (IsUnprototyped)
|
|
Ty = llvm::StructType::get(getLLVMContext());
|
|
else
|
|
Ty = CGM.getTypes().GetFunctionType(FnInfo);
|
|
|
|
llvm::Constant *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
|
|
|
|
// Fix up the function type for an unprototyped musttail call.
|
|
if (IsUnprototyped)
|
|
Callee = llvm::ConstantExpr::getBitCast(Callee, Fn->getType());
|
|
|
|
// Make the call and return the result.
|
|
EmitCallAndReturnForThunk(llvm::FunctionCallee(Fn->getFunctionType(), Callee),
|
|
&Thunk, IsUnprototyped);
|
|
}
|
|
|
|
static bool shouldEmitVTableThunk(CodeGenModule &CGM, const CXXMethodDecl *MD,
|
|
bool IsUnprototyped, bool ForVTable) {
|
|
// Always emit thunks in the MS C++ ABI. We cannot rely on other TUs to
|
|
// provide thunks for us.
|
|
if (CGM.getTarget().getCXXABI().isMicrosoft())
|
|
return true;
|
|
|
|
// In the Itanium C++ ABI, vtable thunks are provided by TUs that provide
|
|
// definitions of the main method. Therefore, emitting thunks with the vtable
|
|
// is purely an optimization. Emit the thunk if optimizations are enabled and
|
|
// all of the parameter types are complete.
|
|
if (ForVTable)
|
|
return CGM.getCodeGenOpts().OptimizationLevel && !IsUnprototyped;
|
|
|
|
// Always emit thunks along with the method definition.
|
|
return true;
|
|
}
|
|
|
|
llvm::Constant *CodeGenVTables::maybeEmitThunk(GlobalDecl GD,
|
|
const ThunkInfo &TI,
|
|
bool ForVTable) {
|
|
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
|
|
|
|
// First, get a declaration. Compute the mangled name. Don't worry about
|
|
// getting the function prototype right, since we may only need this
|
|
// declaration to fill in a vtable slot.
|
|
SmallString<256> Name;
|
|
MangleContext &MCtx = CGM.getCXXABI().getMangleContext();
|
|
llvm::raw_svector_ostream Out(Name);
|
|
if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD))
|
|
MCtx.mangleCXXDtorThunk(DD, GD.getDtorType(), TI.This, Out);
|
|
else
|
|
MCtx.mangleThunk(MD, TI, Out);
|
|
llvm::Type *ThunkVTableTy = CGM.getTypes().GetFunctionTypeForVTable(GD);
|
|
llvm::Constant *Thunk = CGM.GetAddrOfThunk(Name, ThunkVTableTy, GD);
|
|
|
|
// If we don't need to emit a definition, return this declaration as is.
|
|
bool IsUnprototyped = !CGM.getTypes().isFuncTypeConvertible(
|
|
MD->getType()->castAs<FunctionType>());
|
|
if (!shouldEmitVTableThunk(CGM, MD, IsUnprototyped, ForVTable))
|
|
return Thunk;
|
|
|
|
// Arrange a function prototype appropriate for a function definition. In some
|
|
// cases in the MS ABI, we may need to build an unprototyped musttail thunk.
|
|
const CGFunctionInfo &FnInfo =
|
|
IsUnprototyped ? CGM.getTypes().arrangeUnprototypedMustTailThunk(MD)
|
|
: CGM.getTypes().arrangeGlobalDeclaration(GD);
|
|
llvm::FunctionType *ThunkFnTy = CGM.getTypes().GetFunctionType(FnInfo);
|
|
|
|
// If the type of the underlying GlobalValue is wrong, we'll have to replace
|
|
// it. It should be a declaration.
|
|
llvm::Function *ThunkFn = cast<llvm::Function>(Thunk->stripPointerCasts());
|
|
if (ThunkFn->getFunctionType() != ThunkFnTy) {
|
|
llvm::GlobalValue *OldThunkFn = ThunkFn;
|
|
|
|
assert(OldThunkFn->isDeclaration() && "Shouldn't replace non-declaration");
|
|
|
|
// Remove the name from the old thunk function and get a new thunk.
|
|
OldThunkFn->setName(StringRef());
|
|
ThunkFn = llvm::Function::Create(ThunkFnTy, llvm::Function::ExternalLinkage,
|
|
Name.str(), &CGM.getModule());
|
|
CGM.SetLLVMFunctionAttributes(MD, FnInfo, ThunkFn);
|
|
|
|
// If needed, replace the old thunk with a bitcast.
|
|
if (!OldThunkFn->use_empty()) {
|
|
llvm::Constant *NewPtrForOldDecl =
|
|
llvm::ConstantExpr::getBitCast(ThunkFn, OldThunkFn->getType());
|
|
OldThunkFn->replaceAllUsesWith(NewPtrForOldDecl);
|
|
}
|
|
|
|
// Remove the old thunk.
|
|
OldThunkFn->eraseFromParent();
|
|
}
|
|
|
|
bool ABIHasKeyFunctions = CGM.getTarget().getCXXABI().hasKeyFunctions();
|
|
bool UseAvailableExternallyLinkage = ForVTable && ABIHasKeyFunctions;
|
|
|
|
if (!ThunkFn->isDeclaration()) {
|
|
if (!ABIHasKeyFunctions || UseAvailableExternallyLinkage) {
|
|
// There is already a thunk emitted for this function, do nothing.
|
|
return ThunkFn;
|
|
}
|
|
|
|
setThunkProperties(CGM, TI, ThunkFn, ForVTable, GD);
|
|
return ThunkFn;
|
|
}
|
|
|
|
// If this will be unprototyped, add the "thunk" attribute so that LLVM knows
|
|
// that the return type is meaningless. These thunks can be used to call
|
|
// functions with differing return types, and the caller is required to cast
|
|
// the prototype appropriately to extract the correct value.
|
|
if (IsUnprototyped)
|
|
ThunkFn->addFnAttr("thunk");
|
|
|
|
CGM.SetLLVMFunctionAttributesForDefinition(GD.getDecl(), ThunkFn);
|
|
|
|
// Thunks for variadic methods are special because in general variadic
|
|
// arguments cannot be perfectly forwarded. In the general case, clang
|
|
// implements such thunks by cloning the original function body. However, for
|
|
// thunks with no return adjustment on targets that support musttail, we can
|
|
// use musttail to perfectly forward the variadic arguments.
|
|
bool ShouldCloneVarArgs = false;
|
|
if (!IsUnprototyped && ThunkFn->isVarArg()) {
|
|
ShouldCloneVarArgs = true;
|
|
if (TI.Return.isEmpty()) {
|
|
switch (CGM.getTriple().getArch()) {
|
|
case llvm::Triple::x86_64:
|
|
case llvm::Triple::x86:
|
|
case llvm::Triple::aarch64:
|
|
ShouldCloneVarArgs = false;
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (ShouldCloneVarArgs) {
|
|
if (UseAvailableExternallyLinkage)
|
|
return ThunkFn;
|
|
ThunkFn =
|
|
CodeGenFunction(CGM).GenerateVarArgsThunk(ThunkFn, FnInfo, GD, TI);
|
|
} else {
|
|
// Normal thunk body generation.
|
|
CodeGenFunction(CGM).generateThunk(ThunkFn, FnInfo, GD, TI, IsUnprototyped);
|
|
}
|
|
|
|
setThunkProperties(CGM, TI, ThunkFn, ForVTable, GD);
|
|
return ThunkFn;
|
|
}
|
|
|
|
void CodeGenVTables::EmitThunks(GlobalDecl GD) {
|
|
const CXXMethodDecl *MD =
|
|
cast<CXXMethodDecl>(GD.getDecl())->getCanonicalDecl();
|
|
|
|
// We don't need to generate thunks for the base destructor.
|
|
if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
|
|
return;
|
|
|
|
const VTableContextBase::ThunkInfoVectorTy *ThunkInfoVector =
|
|
VTContext->getThunkInfo(GD);
|
|
|
|
if (!ThunkInfoVector)
|
|
return;
|
|
|
|
for (const ThunkInfo& Thunk : *ThunkInfoVector)
|
|
maybeEmitThunk(GD, Thunk, /*ForVTable=*/false);
|
|
}
|
|
|
|
void CodeGenVTables::addRelativeComponent(ConstantArrayBuilder &builder,
|
|
llvm::Constant *component,
|
|
unsigned vtableAddressPoint,
|
|
bool vtableHasLocalLinkage,
|
|
bool isCompleteDtor) const {
|
|
// No need to get the offset of a nullptr.
|
|
if (component->isNullValue())
|
|
return builder.add(llvm::ConstantInt::get(CGM.Int32Ty, 0));
|
|
|
|
auto *globalVal =
|
|
cast<llvm::GlobalValue>(component->stripPointerCastsAndAliases());
|
|
llvm::Module &module = CGM.getModule();
|
|
|
|
// We don't want to copy the linkage of the vtable exactly because we still
|
|
// want the stub/proxy to be emitted for properly calculating the offset.
|
|
// Examples where there would be no symbol emitted are available_externally
|
|
// and private linkages.
|
|
auto stubLinkage = vtableHasLocalLinkage ? llvm::GlobalValue::InternalLinkage
|
|
: llvm::GlobalValue::ExternalLinkage;
|
|
|
|
llvm::Constant *target;
|
|
if (auto *func = dyn_cast<llvm::Function>(globalVal)) {
|
|
target = llvm::DSOLocalEquivalent::get(func);
|
|
} else {
|
|
llvm::SmallString<16> rttiProxyName(globalVal->getName());
|
|
rttiProxyName.append(".rtti_proxy");
|
|
|
|
// The RTTI component may not always be emitted in the same linkage unit as
|
|
// the vtable. As a general case, we can make a dso_local proxy to the RTTI
|
|
// that points to the actual RTTI struct somewhere. This will result in a
|
|
// GOTPCREL relocation when taking the relative offset to the proxy.
|
|
llvm::GlobalVariable *proxy = module.getNamedGlobal(rttiProxyName);
|
|
if (!proxy) {
|
|
proxy = new llvm::GlobalVariable(module, globalVal->getType(),
|
|
/*isConstant=*/true, stubLinkage,
|
|
globalVal, rttiProxyName);
|
|
proxy->setDSOLocal(true);
|
|
proxy->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
|
|
if (!proxy->hasLocalLinkage()) {
|
|
proxy->setVisibility(llvm::GlobalValue::HiddenVisibility);
|
|
proxy->setComdat(module.getOrInsertComdat(rttiProxyName));
|
|
}
|
|
}
|
|
target = proxy;
|
|
}
|
|
|
|
builder.addRelativeOffsetToPosition(CGM.Int32Ty, target,
|
|
/*position=*/vtableAddressPoint);
|
|
}
|
|
|
|
bool CodeGenVTables::useRelativeLayout() const {
|
|
return CGM.getTarget().getCXXABI().isItaniumFamily() &&
|
|
CGM.getItaniumVTableContext().isRelativeLayout();
|
|
}
|
|
|
|
llvm::Type *CodeGenVTables::getVTableComponentType() const {
|
|
if (useRelativeLayout())
|
|
return CGM.Int32Ty;
|
|
return CGM.Int8PtrTy;
|
|
}
|
|
|
|
static void AddPointerLayoutOffset(const CodeGenModule &CGM,
|
|
ConstantArrayBuilder &builder,
|
|
CharUnits offset) {
|
|
builder.add(llvm::ConstantExpr::getIntToPtr(
|
|
llvm::ConstantInt::get(CGM.PtrDiffTy, offset.getQuantity()),
|
|
CGM.Int8PtrTy));
|
|
}
|
|
|
|
static void AddRelativeLayoutOffset(const CodeGenModule &CGM,
|
|
ConstantArrayBuilder &builder,
|
|
CharUnits offset) {
|
|
builder.add(llvm::ConstantInt::get(CGM.Int32Ty, offset.getQuantity()));
|
|
}
|
|
|
|
void CodeGenVTables::addVTableComponent(ConstantArrayBuilder &builder,
|
|
const VTableLayout &layout,
|
|
unsigned componentIndex,
|
|
llvm::Constant *rtti,
|
|
unsigned &nextVTableThunkIndex,
|
|
unsigned vtableAddressPoint,
|
|
bool vtableHasLocalLinkage) {
|
|
auto &component = layout.vtable_components()[componentIndex];
|
|
|
|
auto addOffsetConstant =
|
|
useRelativeLayout() ? AddRelativeLayoutOffset : AddPointerLayoutOffset;
|
|
|
|
switch (component.getKind()) {
|
|
case VTableComponent::CK_VCallOffset:
|
|
return addOffsetConstant(CGM, builder, component.getVCallOffset());
|
|
|
|
case VTableComponent::CK_VBaseOffset:
|
|
return addOffsetConstant(CGM, builder, component.getVBaseOffset());
|
|
|
|
case VTableComponent::CK_OffsetToTop:
|
|
return addOffsetConstant(CGM, builder, component.getOffsetToTop());
|
|
|
|
case VTableComponent::CK_RTTI:
|
|
if (useRelativeLayout())
|
|
return addRelativeComponent(builder, rtti, vtableAddressPoint,
|
|
vtableHasLocalLinkage,
|
|
/*isCompleteDtor=*/false);
|
|
else
|
|
return builder.add(llvm::ConstantExpr::getBitCast(rtti, CGM.Int8PtrTy));
|
|
|
|
case VTableComponent::CK_FunctionPointer:
|
|
case VTableComponent::CK_CompleteDtorPointer:
|
|
case VTableComponent::CK_DeletingDtorPointer: {
|
|
GlobalDecl GD;
|
|
|
|
// Get the right global decl.
|
|
switch (component.getKind()) {
|
|
default:
|
|
llvm_unreachable("Unexpected vtable component kind");
|
|
case VTableComponent::CK_FunctionPointer:
|
|
GD = component.getFunctionDecl();
|
|
break;
|
|
case VTableComponent::CK_CompleteDtorPointer:
|
|
GD = GlobalDecl(component.getDestructorDecl(), Dtor_Complete);
|
|
break;
|
|
case VTableComponent::CK_DeletingDtorPointer:
|
|
GD = GlobalDecl(component.getDestructorDecl(), Dtor_Deleting);
|
|
break;
|
|
}
|
|
|
|
if (CGM.getLangOpts().CUDA) {
|
|
// Emit NULL for methods we can't codegen on this
|
|
// side. Otherwise we'd end up with vtable with unresolved
|
|
// references.
|
|
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
|
|
// OK on device side: functions w/ __device__ attribute
|
|
// OK on host side: anything except __device__-only functions.
|
|
bool CanEmitMethod =
|
|
CGM.getLangOpts().CUDAIsDevice
|
|
? MD->hasAttr<CUDADeviceAttr>()
|
|
: (MD->hasAttr<CUDAHostAttr>() || !MD->hasAttr<CUDADeviceAttr>());
|
|
if (!CanEmitMethod)
|
|
return builder.add(llvm::ConstantExpr::getNullValue(CGM.Int8PtrTy));
|
|
// Method is acceptable, continue processing as usual.
|
|
}
|
|
|
|
auto getSpecialVirtualFn = [&](StringRef name) -> llvm::Constant * {
|
|
// FIXME(PR43094): When merging comdat groups, lld can select a local
|
|
// symbol as the signature symbol even though it cannot be accessed
|
|
// outside that symbol's TU. The relative vtables ABI would make
|
|
// __cxa_pure_virtual and __cxa_deleted_virtual local symbols, and
|
|
// depending on link order, the comdat groups could resolve to the one
|
|
// with the local symbol. As a temporary solution, fill these components
|
|
// with zero. We shouldn't be calling these in the first place anyway.
|
|
if (useRelativeLayout())
|
|
return llvm::ConstantPointerNull::get(CGM.Int8PtrTy);
|
|
|
|
// For NVPTX devices in OpenMP emit special functon as null pointers,
|
|
// otherwise linking ends up with unresolved references.
|
|
if (CGM.getLangOpts().OpenMP && CGM.getLangOpts().OpenMPIsDevice &&
|
|
CGM.getTriple().isNVPTX())
|
|
return llvm::ConstantPointerNull::get(CGM.Int8PtrTy);
|
|
llvm::FunctionType *fnTy =
|
|
llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
|
|
llvm::Constant *fn = cast<llvm::Constant>(
|
|
CGM.CreateRuntimeFunction(fnTy, name).getCallee());
|
|
if (auto f = dyn_cast<llvm::Function>(fn))
|
|
f->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
|
|
return llvm::ConstantExpr::getBitCast(fn, CGM.Int8PtrTy);
|
|
};
|
|
|
|
llvm::Constant *fnPtr;
|
|
|
|
// Pure virtual member functions.
|
|
if (cast<CXXMethodDecl>(GD.getDecl())->isPure()) {
|
|
if (!PureVirtualFn)
|
|
PureVirtualFn =
|
|
getSpecialVirtualFn(CGM.getCXXABI().GetPureVirtualCallName());
|
|
fnPtr = PureVirtualFn;
|
|
|
|
// Deleted virtual member functions.
|
|
} else if (cast<CXXMethodDecl>(GD.getDecl())->isDeleted()) {
|
|
if (!DeletedVirtualFn)
|
|
DeletedVirtualFn =
|
|
getSpecialVirtualFn(CGM.getCXXABI().GetDeletedVirtualCallName());
|
|
fnPtr = DeletedVirtualFn;
|
|
|
|
// Thunks.
|
|
} else if (nextVTableThunkIndex < layout.vtable_thunks().size() &&
|
|
layout.vtable_thunks()[nextVTableThunkIndex].first ==
|
|
componentIndex) {
|
|
auto &thunkInfo = layout.vtable_thunks()[nextVTableThunkIndex].second;
|
|
|
|
nextVTableThunkIndex++;
|
|
fnPtr = maybeEmitThunk(GD, thunkInfo, /*ForVTable=*/true);
|
|
|
|
// Otherwise we can use the method definition directly.
|
|
} else {
|
|
llvm::Type *fnTy = CGM.getTypes().GetFunctionTypeForVTable(GD);
|
|
fnPtr = CGM.GetAddrOfFunction(GD, fnTy, /*ForVTable=*/true);
|
|
}
|
|
|
|
if (useRelativeLayout()) {
|
|
return addRelativeComponent(
|
|
builder, fnPtr, vtableAddressPoint, vtableHasLocalLinkage,
|
|
component.getKind() == VTableComponent::CK_CompleteDtorPointer);
|
|
} else
|
|
return builder.add(llvm::ConstantExpr::getBitCast(fnPtr, CGM.Int8PtrTy));
|
|
}
|
|
|
|
case VTableComponent::CK_UnusedFunctionPointer:
|
|
if (useRelativeLayout())
|
|
return builder.add(llvm::ConstantExpr::getNullValue(CGM.Int32Ty));
|
|
else
|
|
return builder.addNullPointer(CGM.Int8PtrTy);
|
|
}
|
|
|
|
llvm_unreachable("Unexpected vtable component kind");
|
|
}
|
|
|
|
llvm::Type *CodeGenVTables::getVTableType(const VTableLayout &layout) {
|
|
SmallVector<llvm::Type *, 4> tys;
|
|
llvm::Type *componentType = getVTableComponentType();
|
|
for (unsigned i = 0, e = layout.getNumVTables(); i != e; ++i)
|
|
tys.push_back(llvm::ArrayType::get(componentType, layout.getVTableSize(i)));
|
|
|
|
return llvm::StructType::get(CGM.getLLVMContext(), tys);
|
|
}
|
|
|
|
void CodeGenVTables::createVTableInitializer(ConstantStructBuilder &builder,
|
|
const VTableLayout &layout,
|
|
llvm::Constant *rtti,
|
|
bool vtableHasLocalLinkage) {
|
|
llvm::Type *componentType = getVTableComponentType();
|
|
|
|
const auto &addressPoints = layout.getAddressPointIndices();
|
|
unsigned nextVTableThunkIndex = 0;
|
|
for (unsigned vtableIndex = 0, endIndex = layout.getNumVTables();
|
|
vtableIndex != endIndex; ++vtableIndex) {
|
|
auto vtableElem = builder.beginArray(componentType);
|
|
|
|
size_t vtableStart = layout.getVTableOffset(vtableIndex);
|
|
size_t vtableEnd = vtableStart + layout.getVTableSize(vtableIndex);
|
|
for (size_t componentIndex = vtableStart; componentIndex < vtableEnd;
|
|
++componentIndex) {
|
|
addVTableComponent(vtableElem, layout, componentIndex, rtti,
|
|
nextVTableThunkIndex, addressPoints[vtableIndex],
|
|
vtableHasLocalLinkage);
|
|
}
|
|
vtableElem.finishAndAddTo(builder);
|
|
}
|
|
}
|
|
|
|
llvm::GlobalVariable *CodeGenVTables::GenerateConstructionVTable(
|
|
const CXXRecordDecl *RD, const BaseSubobject &Base, bool BaseIsVirtual,
|
|
llvm::GlobalVariable::LinkageTypes Linkage,
|
|
VTableAddressPointsMapTy &AddressPoints) {
|
|
if (CGDebugInfo *DI = CGM.getModuleDebugInfo())
|
|
DI->completeClassData(Base.getBase());
|
|
|
|
std::unique_ptr<VTableLayout> VTLayout(
|
|
getItaniumVTableContext().createConstructionVTableLayout(
|
|
Base.getBase(), Base.getBaseOffset(), BaseIsVirtual, RD));
|
|
|
|
// Add the address points.
|
|
AddressPoints = VTLayout->getAddressPoints();
|
|
|
|
// Get the mangled construction vtable name.
|
|
SmallString<256> OutName;
|
|
llvm::raw_svector_ostream Out(OutName);
|
|
cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
|
|
.mangleCXXCtorVTable(RD, Base.getBaseOffset().getQuantity(),
|
|
Base.getBase(), Out);
|
|
SmallString<256> Name(OutName);
|
|
|
|
bool UsingRelativeLayout = getItaniumVTableContext().isRelativeLayout();
|
|
bool VTableAliasExists =
|
|
UsingRelativeLayout && CGM.getModule().getNamedAlias(Name);
|
|
if (VTableAliasExists) {
|
|
// We previously made the vtable hidden and changed its name.
|
|
Name.append(".local");
|
|
}
|
|
|
|
llvm::Type *VTType = getVTableType(*VTLayout);
|
|
|
|
// Construction vtable symbols are not part of the Itanium ABI, so we cannot
|
|
// guarantee that they actually will be available externally. Instead, when
|
|
// emitting an available_externally VTT, we provide references to an internal
|
|
// linkage construction vtable. The ABI only requires complete-object vtables
|
|
// to be the same for all instances of a type, not construction vtables.
|
|
if (Linkage == llvm::GlobalVariable::AvailableExternallyLinkage)
|
|
Linkage = llvm::GlobalVariable::InternalLinkage;
|
|
|
|
unsigned Align = CGM.getDataLayout().getABITypeAlignment(VTType);
|
|
|
|
// Create the variable that will hold the construction vtable.
|
|
llvm::GlobalVariable *VTable =
|
|
CGM.CreateOrReplaceCXXRuntimeVariable(Name, VTType, Linkage, Align);
|
|
|
|
// V-tables are always unnamed_addr.
|
|
VTable->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
|
|
|
|
llvm::Constant *RTTI = CGM.GetAddrOfRTTIDescriptor(
|
|
CGM.getContext().getTagDeclType(Base.getBase()));
|
|
|
|
// Create and set the initializer.
|
|
ConstantInitBuilder builder(CGM);
|
|
auto components = builder.beginStruct();
|
|
createVTableInitializer(components, *VTLayout, RTTI,
|
|
VTable->hasLocalLinkage());
|
|
components.finishAndSetAsInitializer(VTable);
|
|
|
|
// Set properties only after the initializer has been set to ensure that the
|
|
// GV is treated as definition and not declaration.
|
|
assert(!VTable->isDeclaration() && "Shouldn't set properties on declaration");
|
|
CGM.setGVProperties(VTable, RD);
|
|
|
|
CGM.EmitVTableTypeMetadata(RD, VTable, *VTLayout.get());
|
|
|
|
if (UsingRelativeLayout && !VTable->isDSOLocal())
|
|
GenerateRelativeVTableAlias(VTable, OutName);
|
|
|
|
return VTable;
|
|
}
|
|
|
|
// If the VTable is not dso_local, then we will not be able to indicate that
|
|
// the VTable does not need a relocation and move into rodata. A frequent
|
|
// time this can occur is for classes that should be made public from a DSO
|
|
// (like in libc++). For cases like these, we can make the vtable hidden or
|
|
// private and create a public alias with the same visibility and linkage as
|
|
// the original vtable type.
|
|
void CodeGenVTables::GenerateRelativeVTableAlias(llvm::GlobalVariable *VTable,
|
|
llvm::StringRef AliasNameRef) {
|
|
assert(getItaniumVTableContext().isRelativeLayout() &&
|
|
"Can only use this if the relative vtable ABI is used");
|
|
assert(!VTable->isDSOLocal() && "This should be called only if the vtable is "
|
|
"not guaranteed to be dso_local");
|
|
|
|
// If the vtable is available_externally, we shouldn't (or need to) generate
|
|
// an alias for it in the first place since the vtable won't actually by
|
|
// emitted in this compilation unit.
|
|
if (VTable->hasAvailableExternallyLinkage())
|
|
return;
|
|
|
|
// Create a new string in the event the alias is already the name of the
|
|
// vtable. Using the reference directly could lead to use of an inititialized
|
|
// value in the module's StringMap.
|
|
llvm::SmallString<256> AliasName(AliasNameRef);
|
|
VTable->setName(AliasName + ".local");
|
|
|
|
auto Linkage = VTable->getLinkage();
|
|
assert(llvm::GlobalAlias::isValidLinkage(Linkage) &&
|
|
"Invalid vtable alias linkage");
|
|
|
|
llvm::GlobalAlias *VTableAlias = CGM.getModule().getNamedAlias(AliasName);
|
|
if (!VTableAlias) {
|
|
VTableAlias = llvm::GlobalAlias::create(VTable->getValueType(),
|
|
VTable->getAddressSpace(), Linkage,
|
|
AliasName, &CGM.getModule());
|
|
} else {
|
|
assert(VTableAlias->getValueType() == VTable->getValueType());
|
|
assert(VTableAlias->getLinkage() == Linkage);
|
|
}
|
|
VTableAlias->setVisibility(VTable->getVisibility());
|
|
VTableAlias->setUnnamedAddr(VTable->getUnnamedAddr());
|
|
|
|
// Both of these imply dso_local for the vtable.
|
|
if (!VTable->hasComdat()) {
|
|
// If this is in a comdat, then we shouldn't make the linkage private due to
|
|
// an issue in lld where private symbols can be used as the key symbol when
|
|
// choosing the prevelant group. This leads to "relocation refers to a
|
|
// symbol in a discarded section".
|
|
VTable->setLinkage(llvm::GlobalValue::PrivateLinkage);
|
|
} else {
|
|
// We should at least make this hidden since we don't want to expose it.
|
|
VTable->setVisibility(llvm::GlobalValue::HiddenVisibility);
|
|
}
|
|
|
|
VTableAlias->setAliasee(VTable);
|
|
}
|
|
|
|
static bool shouldEmitAvailableExternallyVTable(const CodeGenModule &CGM,
|
|
const CXXRecordDecl *RD) {
|
|
return CGM.getCodeGenOpts().OptimizationLevel > 0 &&
|
|
CGM.getCXXABI().canSpeculativelyEmitVTable(RD);
|
|
}
|
|
|
|
/// Compute the required linkage of the vtable for the given class.
|
|
///
|
|
/// Note that we only call this at the end of the translation unit.
|
|
llvm::GlobalVariable::LinkageTypes
|
|
CodeGenModule::getVTableLinkage(const CXXRecordDecl *RD) {
|
|
if (!RD->isExternallyVisible())
|
|
return llvm::GlobalVariable::InternalLinkage;
|
|
|
|
// We're at the end of the translation unit, so the current key
|
|
// function is fully correct.
|
|
const CXXMethodDecl *keyFunction = Context.getCurrentKeyFunction(RD);
|
|
if (keyFunction && !RD->hasAttr<DLLImportAttr>()) {
|
|
// If this class has a key function, use that to determine the
|
|
// linkage of the vtable.
|
|
const FunctionDecl *def = nullptr;
|
|
if (keyFunction->hasBody(def))
|
|
keyFunction = cast<CXXMethodDecl>(def);
|
|
|
|
switch (keyFunction->getTemplateSpecializationKind()) {
|
|
case TSK_Undeclared:
|
|
case TSK_ExplicitSpecialization:
|
|
assert((def || CodeGenOpts.OptimizationLevel > 0 ||
|
|
CodeGenOpts.getDebugInfo() != codegenoptions::NoDebugInfo) &&
|
|
"Shouldn't query vtable linkage without key function, "
|
|
"optimizations, or debug info");
|
|
if (!def && CodeGenOpts.OptimizationLevel > 0)
|
|
return llvm::GlobalVariable::AvailableExternallyLinkage;
|
|
|
|
if (keyFunction->isInlined())
|
|
return !Context.getLangOpts().AppleKext ?
|
|
llvm::GlobalVariable::LinkOnceODRLinkage :
|
|
llvm::Function::InternalLinkage;
|
|
|
|
return llvm::GlobalVariable::ExternalLinkage;
|
|
|
|
case TSK_ImplicitInstantiation:
|
|
return !Context.getLangOpts().AppleKext ?
|
|
llvm::GlobalVariable::LinkOnceODRLinkage :
|
|
llvm::Function::InternalLinkage;
|
|
|
|
case TSK_ExplicitInstantiationDefinition:
|
|
return !Context.getLangOpts().AppleKext ?
|
|
llvm::GlobalVariable::WeakODRLinkage :
|
|
llvm::Function::InternalLinkage;
|
|
|
|
case TSK_ExplicitInstantiationDeclaration:
|
|
llvm_unreachable("Should not have been asked to emit this");
|
|
}
|
|
}
|
|
|
|
// -fapple-kext mode does not support weak linkage, so we must use
|
|
// internal linkage.
|
|
if (Context.getLangOpts().AppleKext)
|
|
return llvm::Function::InternalLinkage;
|
|
|
|
llvm::GlobalVariable::LinkageTypes DiscardableODRLinkage =
|
|
llvm::GlobalValue::LinkOnceODRLinkage;
|
|
llvm::GlobalVariable::LinkageTypes NonDiscardableODRLinkage =
|
|
llvm::GlobalValue::WeakODRLinkage;
|
|
if (RD->hasAttr<DLLExportAttr>()) {
|
|
// Cannot discard exported vtables.
|
|
DiscardableODRLinkage = NonDiscardableODRLinkage;
|
|
} else if (RD->hasAttr<DLLImportAttr>()) {
|
|
// Imported vtables are available externally.
|
|
DiscardableODRLinkage = llvm::GlobalVariable::AvailableExternallyLinkage;
|
|
NonDiscardableODRLinkage = llvm::GlobalVariable::AvailableExternallyLinkage;
|
|
}
|
|
|
|
switch (RD->getTemplateSpecializationKind()) {
|
|
case TSK_Undeclared:
|
|
case TSK_ExplicitSpecialization:
|
|
case TSK_ImplicitInstantiation:
|
|
return DiscardableODRLinkage;
|
|
|
|
case TSK_ExplicitInstantiationDeclaration:
|
|
// Explicit instantiations in MSVC do not provide vtables, so we must emit
|
|
// our own.
|
|
if (getTarget().getCXXABI().isMicrosoft())
|
|
return DiscardableODRLinkage;
|
|
return shouldEmitAvailableExternallyVTable(*this, RD)
|
|
? llvm::GlobalVariable::AvailableExternallyLinkage
|
|
: llvm::GlobalVariable::ExternalLinkage;
|
|
|
|
case TSK_ExplicitInstantiationDefinition:
|
|
return NonDiscardableODRLinkage;
|
|
}
|
|
|
|
llvm_unreachable("Invalid TemplateSpecializationKind!");
|
|
}
|
|
|
|
/// This is a callback from Sema to tell us that a particular vtable is
|
|
/// required to be emitted in this translation unit.
|
|
///
|
|
/// This is only called for vtables that _must_ be emitted (mainly due to key
|
|
/// functions). For weak vtables, CodeGen tracks when they are needed and
|
|
/// emits them as-needed.
|
|
void CodeGenModule::EmitVTable(CXXRecordDecl *theClass) {
|
|
VTables.GenerateClassData(theClass);
|
|
}
|
|
|
|
void
|
|
CodeGenVTables::GenerateClassData(const CXXRecordDecl *RD) {
|
|
if (CGDebugInfo *DI = CGM.getModuleDebugInfo())
|
|
DI->completeClassData(RD);
|
|
|
|
if (RD->getNumVBases())
|
|
CGM.getCXXABI().emitVirtualInheritanceTables(RD);
|
|
|
|
CGM.getCXXABI().emitVTableDefinitions(*this, RD);
|
|
}
|
|
|
|
/// At this point in the translation unit, does it appear that can we
|
|
/// rely on the vtable being defined elsewhere in the program?
|
|
///
|
|
/// The response is really only definitive when called at the end of
|
|
/// the translation unit.
|
|
///
|
|
/// The only semantic restriction here is that the object file should
|
|
/// not contain a vtable definition when that vtable is defined
|
|
/// strongly elsewhere. Otherwise, we'd just like to avoid emitting
|
|
/// vtables when unnecessary.
|
|
bool CodeGenVTables::isVTableExternal(const CXXRecordDecl *RD) {
|
|
assert(RD->isDynamicClass() && "Non-dynamic classes have no VTable.");
|
|
|
|
// We always synthesize vtables if they are needed in the MS ABI. MSVC doesn't
|
|
// emit them even if there is an explicit template instantiation.
|
|
if (CGM.getTarget().getCXXABI().isMicrosoft())
|
|
return false;
|
|
|
|
// If we have an explicit instantiation declaration (and not a
|
|
// definition), the vtable is defined elsewhere.
|
|
TemplateSpecializationKind TSK = RD->getTemplateSpecializationKind();
|
|
if (TSK == TSK_ExplicitInstantiationDeclaration)
|
|
return true;
|
|
|
|
// Otherwise, if the class is an instantiated template, the
|
|
// vtable must be defined here.
|
|
if (TSK == TSK_ImplicitInstantiation ||
|
|
TSK == TSK_ExplicitInstantiationDefinition)
|
|
return false;
|
|
|
|
// Otherwise, if the class doesn't have a key function (possibly
|
|
// anymore), the vtable must be defined here.
|
|
const CXXMethodDecl *keyFunction = CGM.getContext().getCurrentKeyFunction(RD);
|
|
if (!keyFunction)
|
|
return false;
|
|
|
|
// Otherwise, if we don't have a definition of the key function, the
|
|
// vtable must be defined somewhere else.
|
|
return !keyFunction->hasBody();
|
|
}
|
|
|
|
/// Given that we're currently at the end of the translation unit, and
|
|
/// we've emitted a reference to the vtable for this class, should
|
|
/// we define that vtable?
|
|
static bool shouldEmitVTableAtEndOfTranslationUnit(CodeGenModule &CGM,
|
|
const CXXRecordDecl *RD) {
|
|
// If vtable is internal then it has to be done.
|
|
if (!CGM.getVTables().isVTableExternal(RD))
|
|
return true;
|
|
|
|
// If it's external then maybe we will need it as available_externally.
|
|
return shouldEmitAvailableExternallyVTable(CGM, RD);
|
|
}
|
|
|
|
/// Given that at some point we emitted a reference to one or more
|
|
/// vtables, and that we are now at the end of the translation unit,
|
|
/// decide whether we should emit them.
|
|
void CodeGenModule::EmitDeferredVTables() {
|
|
#ifndef NDEBUG
|
|
// Remember the size of DeferredVTables, because we're going to assume
|
|
// that this entire operation doesn't modify it.
|
|
size_t savedSize = DeferredVTables.size();
|
|
#endif
|
|
|
|
for (const CXXRecordDecl *RD : DeferredVTables)
|
|
if (shouldEmitVTableAtEndOfTranslationUnit(*this, RD))
|
|
VTables.GenerateClassData(RD);
|
|
else if (shouldOpportunisticallyEmitVTables())
|
|
OpportunisticVTables.push_back(RD);
|
|
|
|
assert(savedSize == DeferredVTables.size() &&
|
|
"deferred extra vtables during vtable emission?");
|
|
DeferredVTables.clear();
|
|
}
|
|
|
|
bool CodeGenModule::HasLTOVisibilityPublicStd(const CXXRecordDecl *RD) {
|
|
if (!getCodeGenOpts().LTOVisibilityPublicStd)
|
|
return false;
|
|
|
|
const DeclContext *DC = RD;
|
|
while (1) {
|
|
auto *D = cast<Decl>(DC);
|
|
DC = DC->getParent();
|
|
if (isa<TranslationUnitDecl>(DC->getRedeclContext())) {
|
|
if (auto *ND = dyn_cast<NamespaceDecl>(D))
|
|
if (const IdentifierInfo *II = ND->getIdentifier())
|
|
if (II->isStr("std") || II->isStr("stdext"))
|
|
return true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
bool CodeGenModule::HasHiddenLTOVisibility(const CXXRecordDecl *RD) {
|
|
LinkageInfo LV = RD->getLinkageAndVisibility();
|
|
if (!isExternallyVisible(LV.getLinkage()))
|
|
return true;
|
|
|
|
if (RD->hasAttr<LTOVisibilityPublicAttr>() || RD->hasAttr<UuidAttr>())
|
|
return false;
|
|
|
|
if (getTriple().isOSBinFormatCOFF()) {
|
|
if (RD->hasAttr<DLLExportAttr>() || RD->hasAttr<DLLImportAttr>())
|
|
return false;
|
|
} else {
|
|
if (LV.getVisibility() != HiddenVisibility)
|
|
return false;
|
|
}
|
|
|
|
return !HasLTOVisibilityPublicStd(RD);
|
|
}
|
|
|
|
llvm::GlobalObject::VCallVisibility CodeGenModule::GetVCallVisibilityLevel(
|
|
const CXXRecordDecl *RD, llvm::DenseSet<const CXXRecordDecl *> &Visited) {
|
|
// If we have already visited this RD (which means this is a recursive call
|
|
// since the initial call should have an empty Visited set), return the max
|
|
// visibility. The recursive calls below compute the min between the result
|
|
// of the recursive call and the current TypeVis, so returning the max here
|
|
// ensures that it will have no effect on the current TypeVis.
|
|
if (!Visited.insert(RD).second)
|
|
return llvm::GlobalObject::VCallVisibilityTranslationUnit;
|
|
|
|
LinkageInfo LV = RD->getLinkageAndVisibility();
|
|
llvm::GlobalObject::VCallVisibility TypeVis;
|
|
if (!isExternallyVisible(LV.getLinkage()))
|
|
TypeVis = llvm::GlobalObject::VCallVisibilityTranslationUnit;
|
|
else if (HasHiddenLTOVisibility(RD))
|
|
TypeVis = llvm::GlobalObject::VCallVisibilityLinkageUnit;
|
|
else
|
|
TypeVis = llvm::GlobalObject::VCallVisibilityPublic;
|
|
|
|
for (auto B : RD->bases())
|
|
if (B.getType()->getAsCXXRecordDecl()->isDynamicClass())
|
|
TypeVis = std::min(
|
|
TypeVis,
|
|
GetVCallVisibilityLevel(B.getType()->getAsCXXRecordDecl(), Visited));
|
|
|
|
for (auto B : RD->vbases())
|
|
if (B.getType()->getAsCXXRecordDecl()->isDynamicClass())
|
|
TypeVis = std::min(
|
|
TypeVis,
|
|
GetVCallVisibilityLevel(B.getType()->getAsCXXRecordDecl(), Visited));
|
|
|
|
return TypeVis;
|
|
}
|
|
|
|
void CodeGenModule::EmitVTableTypeMetadata(const CXXRecordDecl *RD,
|
|
llvm::GlobalVariable *VTable,
|
|
const VTableLayout &VTLayout) {
|
|
if (!getCodeGenOpts().LTOUnit)
|
|
return;
|
|
|
|
CharUnits PointerWidth =
|
|
Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
|
|
|
|
typedef std::pair<const CXXRecordDecl *, unsigned> AddressPoint;
|
|
std::vector<AddressPoint> AddressPoints;
|
|
for (auto &&AP : VTLayout.getAddressPoints())
|
|
AddressPoints.push_back(std::make_pair(
|
|
AP.first.getBase(), VTLayout.getVTableOffset(AP.second.VTableIndex) +
|
|
AP.second.AddressPointIndex));
|
|
|
|
// Sort the address points for determinism.
|
|
llvm::sort(AddressPoints, [this](const AddressPoint &AP1,
|
|
const AddressPoint &AP2) {
|
|
if (&AP1 == &AP2)
|
|
return false;
|
|
|
|
std::string S1;
|
|
llvm::raw_string_ostream O1(S1);
|
|
getCXXABI().getMangleContext().mangleTypeName(
|
|
QualType(AP1.first->getTypeForDecl(), 0), O1);
|
|
O1.flush();
|
|
|
|
std::string S2;
|
|
llvm::raw_string_ostream O2(S2);
|
|
getCXXABI().getMangleContext().mangleTypeName(
|
|
QualType(AP2.first->getTypeForDecl(), 0), O2);
|
|
O2.flush();
|
|
|
|
if (S1 < S2)
|
|
return true;
|
|
if (S1 != S2)
|
|
return false;
|
|
|
|
return AP1.second < AP2.second;
|
|
});
|
|
|
|
ArrayRef<VTableComponent> Comps = VTLayout.vtable_components();
|
|
for (auto AP : AddressPoints) {
|
|
// Create type metadata for the address point.
|
|
AddVTableTypeMetadata(VTable, PointerWidth * AP.second, AP.first);
|
|
|
|
// The class associated with each address point could also potentially be
|
|
// used for indirect calls via a member function pointer, so we need to
|
|
// annotate the address of each function pointer with the appropriate member
|
|
// function pointer type.
|
|
for (unsigned I = 0; I != Comps.size(); ++I) {
|
|
if (Comps[I].getKind() != VTableComponent::CK_FunctionPointer)
|
|
continue;
|
|
llvm::Metadata *MD = CreateMetadataIdentifierForVirtualMemPtrType(
|
|
Context.getMemberPointerType(
|
|
Comps[I].getFunctionDecl()->getType(),
|
|
Context.getRecordType(AP.first).getTypePtr()));
|
|
VTable->addTypeMetadata((PointerWidth * I).getQuantity(), MD);
|
|
}
|
|
}
|
|
|
|
if (getCodeGenOpts().VirtualFunctionElimination ||
|
|
getCodeGenOpts().WholeProgramVTables) {
|
|
llvm::DenseSet<const CXXRecordDecl *> Visited;
|
|
llvm::GlobalObject::VCallVisibility TypeVis =
|
|
GetVCallVisibilityLevel(RD, Visited);
|
|
if (TypeVis != llvm::GlobalObject::VCallVisibilityPublic)
|
|
VTable->setVCallVisibilityMetadata(TypeVis);
|
|
}
|
|
}
|