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llvm-project/clang/lib/CodeGen/CGDeclCXX.cpp

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//===--- CGDeclCXX.cpp - Emit LLVM Code for C++ declarations --------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This contains code dealing with code generation of C++ declarations
//
//===----------------------------------------------------------------------===//
#include "CodeGenFunction.h"
#include "CGCXXABI.h"
#include "CGObjCRuntime.h"
#include "clang/Frontend/CodeGenOptions.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/Support/Path.h"
using namespace clang;
using namespace CodeGen;
static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D,
llvm::Constant *DeclPtr) {
assert(D.hasGlobalStorage() && "VarDecl must have global storage!");
assert(!D.getType()->isReferenceType() &&
"Should not call EmitDeclInit on a reference!");
ASTContext &Context = CGF.getContext();
CharUnits alignment = Context.getDeclAlign(&D);
QualType type = D.getType();
LValue lv = CGF.MakeAddrLValue(DeclPtr, type, alignment);
const Expr *Init = D.getInit();
switch (CGF.getEvaluationKind(type)) {
case TEK_Scalar: {
CodeGenModule &CGM = CGF.CGM;
if (lv.isObjCStrong())
CGM.getObjCRuntime().EmitObjCGlobalAssign(CGF, CGF.EmitScalarExpr(Init),
DeclPtr, D.getTLSKind());
else if (lv.isObjCWeak())
CGM.getObjCRuntime().EmitObjCWeakAssign(CGF, CGF.EmitScalarExpr(Init),
DeclPtr);
else
CGF.EmitScalarInit(Init, &D, lv, false);
return;
}
case TEK_Complex:
CGF.EmitComplexExprIntoLValue(Init, lv, /*isInit*/ true);
return;
case TEK_Aggregate:
CGF.EmitAggExpr(Init, AggValueSlot::forLValue(lv,AggValueSlot::IsDestructed,
AggValueSlot::DoesNotNeedGCBarriers,
AggValueSlot::IsNotAliased));
return;
}
llvm_unreachable("bad evaluation kind");
}
/// Emit code to cause the destruction of the given variable with
/// static storage duration.
static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
llvm::Constant *addr) {
CodeGenModule &CGM = CGF.CGM;
// FIXME: __attribute__((cleanup)) ?
QualType type = D.getType();
QualType::DestructionKind dtorKind = type.isDestructedType();
switch (dtorKind) {
case QualType::DK_none:
return;
case QualType::DK_cxx_destructor:
break;
case QualType::DK_objc_strong_lifetime:
case QualType::DK_objc_weak_lifetime:
// We don't care about releasing objects during process teardown.
assert(!D.getTLSKind() && "should have rejected this");
return;
}
llvm::Constant *function;
llvm::Constant *argument;
// Special-case non-array C++ destructors, where there's a function
// with the right signature that we can just call.
const CXXRecordDecl *record = nullptr;
if (dtorKind == QualType::DK_cxx_destructor &&
(record = type->getAsCXXRecordDecl())) {
assert(!record->hasTrivialDestructor());
CXXDestructorDecl *dtor = record->getDestructor();
function = CGM.getAddrOfCXXStructor(dtor, StructorType::Complete);
argument = llvm::ConstantExpr::getBitCast(
addr, CGF.getTypes().ConvertType(type)->getPointerTo());
// Otherwise, the standard logic requires a helper function.
} else {
function = CodeGenFunction(CGM)
.generateDestroyHelper(addr, type, CGF.getDestroyer(dtorKind),
CGF.needsEHCleanup(dtorKind), &D);
argument = llvm::Constant::getNullValue(CGF.Int8PtrTy);
}
CGM.getCXXABI().registerGlobalDtor(CGF, D, function, argument);
}
/// Emit code to cause the variable at the given address to be considered as
/// constant from this point onwards.
static void EmitDeclInvariant(CodeGenFunction &CGF, const VarDecl &D,
llvm::Constant *Addr) {
// Don't emit the intrinsic if we're not optimizing.
if (!CGF.CGM.getCodeGenOpts().OptimizationLevel)
return;
// Grab the llvm.invariant.start intrinsic.
llvm::Intrinsic::ID InvStartID = llvm::Intrinsic::invariant_start;
llvm::Constant *InvariantStart = CGF.CGM.getIntrinsic(InvStartID);
// Emit a call with the size in bytes of the object.
CharUnits WidthChars = CGF.getContext().getTypeSizeInChars(D.getType());
uint64_t Width = WidthChars.getQuantity();
llvm::Value *Args[2] = { llvm::ConstantInt::getSigned(CGF.Int64Ty, Width),
llvm::ConstantExpr::getBitCast(Addr, CGF.Int8PtrTy)};
CGF.Builder.CreateCall(InvariantStart, Args);
}
void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
llvm::Constant *DeclPtr,
bool PerformInit) {
const Expr *Init = D.getInit();
QualType T = D.getType();
if (!T->isReferenceType()) {
if (PerformInit)
EmitDeclInit(*this, D, DeclPtr);
if (CGM.isTypeConstant(D.getType(), true))
EmitDeclInvariant(*this, D, DeclPtr);
else
EmitDeclDestroy(*this, D, DeclPtr);
return;
}
assert(PerformInit && "cannot have constant initializer which needs "
"destruction for reference");
unsigned Alignment = getContext().getDeclAlign(&D).getQuantity();
RValue RV = EmitReferenceBindingToExpr(Init);
EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, Alignment, T);
}
/// Create a stub function, suitable for being passed to atexit,
/// which passes the given address to the given destructor function.
llvm::Constant *CodeGenFunction::createAtExitStub(const VarDecl &VD,
llvm::Constant *dtor,
llvm::Constant *addr) {
// Get the destructor function type, void(*)(void).
llvm::FunctionType *ty = llvm::FunctionType::get(CGM.VoidTy, false);
SmallString<256> FnName;
{
llvm::raw_svector_ostream Out(FnName);
CGM.getCXXABI().getMangleContext().mangleDynamicAtExitDestructor(&VD, Out);
}
llvm::Function *fn = CGM.CreateGlobalInitOrDestructFunction(ty, FnName.str(),
VD.getLocation());
CodeGenFunction CGF(CGM);
CGF.StartFunction(&VD, CGM.getContext().VoidTy, fn,
CGM.getTypes().arrangeNullaryFunction(), FunctionArgList());
llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr);
// Make sure the call and the callee agree on calling convention.
if (llvm::Function *dtorFn =
dyn_cast<llvm::Function>(dtor->stripPointerCasts()))
call->setCallingConv(dtorFn->getCallingConv());
CGF.FinishFunction();
return fn;
}
/// Register a global destructor using the C atexit runtime function.
void CodeGenFunction::registerGlobalDtorWithAtExit(const VarDecl &VD,
llvm::Constant *dtor,
llvm::Constant *addr) {
// Create a function which calls the destructor.
llvm::Constant *dtorStub = createAtExitStub(VD, dtor, addr);
// extern "C" int atexit(void (*f)(void));
llvm::FunctionType *atexitTy =
llvm::FunctionType::get(IntTy, dtorStub->getType(), false);
llvm::Constant *atexit =
CGM.CreateRuntimeFunction(atexitTy, "atexit");
if (llvm::Function *atexitFn = dyn_cast<llvm::Function>(atexit))
atexitFn->setDoesNotThrow();
EmitNounwindRuntimeCall(atexit, dtorStub);
}
void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D,
llvm::GlobalVariable *DeclPtr,
bool PerformInit) {
// If we've been asked to forbid guard variables, emit an error now.
// This diagnostic is hard-coded for Darwin's use case; we can find
// better phrasing if someone else needs it.
if (CGM.getCodeGenOpts().ForbidGuardVariables)
CGM.Error(D.getLocation(),
"this initialization requires a guard variable, which "
"the kernel does not support");
CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr, PerformInit);
}
llvm::Function *CodeGenModule::CreateGlobalInitOrDestructFunction(
llvm::FunctionType *FTy, const Twine &Name, SourceLocation Loc, bool TLS) {
llvm::Function *Fn =
llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
Name, &getModule());
if (!getLangOpts().AppleKext && !TLS) {
// Set the section if needed.
if (const char *Section = getTarget().getStaticInitSectionSpecifier())
Fn->setSection(Section);
}
Fn->setCallingConv(getRuntimeCC());
if (!getLangOpts().Exceptions)
Fn->setDoesNotThrow();
if (!isInSanitizerBlacklist(Fn, Loc)) {
if (getLangOpts().Sanitize.Address)
Fn->addFnAttr(llvm::Attribute::SanitizeAddress);
if (getLangOpts().Sanitize.Thread)
Fn->addFnAttr(llvm::Attribute::SanitizeThread);
if (getLangOpts().Sanitize.Memory)
Fn->addFnAttr(llvm::Attribute::SanitizeMemory);
}
return Fn;
}
/// Create a global pointer to a function that will initialize a global
/// variable. The user has requested that this pointer be emitted in a specific
/// section.
void CodeGenModule::EmitPointerToInitFunc(const VarDecl *D,
llvm::GlobalVariable *GV,
llvm::Function *InitFunc,
InitSegAttr *ISA) {
llvm::GlobalVariable *PtrArray = new llvm::GlobalVariable(
TheModule, InitFunc->getType(), /*isConstant=*/true,
llvm::GlobalValue::PrivateLinkage, InitFunc, "__cxx_init_fn_ptr");
PtrArray->setSection(ISA->getSection());
addUsedGlobal(PtrArray);
// If the GV is already in a comdat group, then we have to join it.
llvm::Comdat *C = GV->getComdat();
// LinkOnce and Weak linkage are lowered down to a single-member comdat group.
// Make an explicit group so we can join it.
if (!C && (GV->hasWeakLinkage() || GV->hasLinkOnceLinkage())) {
C = TheModule.getOrInsertComdat(GV->getName());
GV->setComdat(C);
}
if (C)
PtrArray->setComdat(C);
}
void
CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
llvm::GlobalVariable *Addr,
bool PerformInit) {
llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
SmallString<256> FnName;
{
llvm::raw_svector_ostream Out(FnName);
getCXXABI().getMangleContext().mangleDynamicInitializer(D, Out);
}
// Create a variable initialization function.
llvm::Function *Fn =
CreateGlobalInitOrDestructFunction(FTy, FnName.str(), D->getLocation());
auto *ISA = D->getAttr<InitSegAttr>();
CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr,
PerformInit);
llvm::GlobalVariable *COMDATKey =
supportsCOMDAT() && D->isExternallyVisible() ? Addr : nullptr;
if (D->getTLSKind()) {
// FIXME: Should we support init_priority for thread_local?
// FIXME: Ideally, initialization of instantiated thread_local static data
// members of class templates should not trigger initialization of other
// entities in the TU.
// FIXME: We only need to register one __cxa_thread_atexit function for the
// entire TU.
CXXThreadLocalInits.push_back(Fn);
CXXThreadLocalInitVars.push_back(Addr);
} else if (PerformInit && ISA) {
EmitPointerToInitFunc(D, Addr, Fn, ISA);
DelayedCXXInitPosition.erase(D);
} else if (auto *IPA = D->getAttr<InitPriorityAttr>()) {
OrderGlobalInits Key(IPA->getPriority(), PrioritizedCXXGlobalInits.size());
PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
DelayedCXXInitPosition.erase(D);
} else if (isTemplateInstantiation(D->getTemplateSpecializationKind())) {
// C++ [basic.start.init]p2:
// Definitions of explicitly specialized class template static data
// members have ordered initialization. Other class template static data
// members (i.e., implicitly or explicitly instantiated specializations)
// have unordered initialization.
//
// As a consequence, we can put them into their own llvm.global_ctors entry.
//
// If the global is externally visible, put the initializer into a COMDAT
// group with the global being initialized. On most platforms, this is a
// minor startup time optimization. In the MS C++ ABI, there are no guard
// variables, so this COMDAT key is required for correctness.
AddGlobalCtor(Fn, 65535, COMDATKey);
DelayedCXXInitPosition.erase(D);
} else if (D->hasAttr<SelectAnyAttr>()) {
// SelectAny globals will be comdat-folded. Put the initializer into a COMDAT
// group associated with the global, so the initializers get folded too.
AddGlobalCtor(Fn, 65535, COMDATKey);
DelayedCXXInitPosition.erase(D);
} else {
llvm::DenseMap<const Decl *, unsigned>::iterator I =
DelayedCXXInitPosition.find(D);
if (I == DelayedCXXInitPosition.end()) {
CXXGlobalInits.push_back(Fn);
} else {
assert(CXXGlobalInits[I->second] == nullptr);
CXXGlobalInits[I->second] = Fn;
DelayedCXXInitPosition.erase(I);
}
}
}
void CodeGenModule::EmitCXXThreadLocalInitFunc() {
getCXXABI().EmitThreadLocalInitFuncs(
*this, CXXThreadLocals, CXXThreadLocalInits, CXXThreadLocalInitVars);
CXXThreadLocalInits.clear();
CXXThreadLocalInitVars.clear();
CXXThreadLocals.clear();
}
void
CodeGenModule::EmitCXXGlobalInitFunc() {
while (!CXXGlobalInits.empty() && !CXXGlobalInits.back())
CXXGlobalInits.pop_back();
if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty())
return;
llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
// Create our global initialization function.
if (!PrioritizedCXXGlobalInits.empty()) {
SmallVector<llvm::Function *, 8> LocalCXXGlobalInits;
llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(),
PrioritizedCXXGlobalInits.end());
// Iterate over "chunks" of ctors with same priority and emit each chunk
// into separate function. Note - everything is sorted first by priority,
// second - by lex order, so we emit ctor functions in proper order.
for (SmallVectorImpl<GlobalInitData >::iterator
I = PrioritizedCXXGlobalInits.begin(),
E = PrioritizedCXXGlobalInits.end(); I != E; ) {
SmallVectorImpl<GlobalInitData >::iterator
PrioE = std::upper_bound(I + 1, E, *I, GlobalInitPriorityCmp());
LocalCXXGlobalInits.clear();
unsigned Priority = I->first.priority;
// Compute the function suffix from priority. Prepend with zeroes to make
// sure the function names are also ordered as priorities.
std::string PrioritySuffix = llvm::utostr(Priority);
// Priority is always <= 65535 (enforced by sema).
PrioritySuffix = std::string(6-PrioritySuffix.size(), '0')+PrioritySuffix;
llvm::Function *Fn = CreateGlobalInitOrDestructFunction(
FTy, "_GLOBAL__I_" + PrioritySuffix);
for (; I < PrioE; ++I)
LocalCXXGlobalInits.push_back(I->second);
CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, LocalCXXGlobalInits);
AddGlobalCtor(Fn, Priority);
}
}
SmallString<128> FileName;
SourceManager &SM = Context.getSourceManager();
if (const FileEntry *MainFile = SM.getFileEntryForID(SM.getMainFileID())) {
// Include the filename in the symbol name. Including "sub_" matches gcc and
// makes sure these symbols appear lexicographically behind the symbols with
// priority emitted above.
FileName = llvm::sys::path::filename(MainFile->getName());
} else {
FileName = SmallString<128>("<null>");
}
for (size_t i = 0; i < FileName.size(); ++i) {
// Replace everything that's not [a-zA-Z0-9._] with a _. This set happens
// to be the set of C preprocessing numbers.
if (!isPreprocessingNumberBody(FileName[i]))
FileName[i] = '_';
}
llvm::Function *Fn = CreateGlobalInitOrDestructFunction(
FTy, llvm::Twine("_GLOBAL__sub_I_", FileName));
CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, CXXGlobalInits);
AddGlobalCtor(Fn);
CXXGlobalInits.clear();
PrioritizedCXXGlobalInits.clear();
}
void CodeGenModule::EmitCXXGlobalDtorFunc() {
if (CXXGlobalDtors.empty())
return;
llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
// Create our global destructor function.
llvm::Function *Fn = CreateGlobalInitOrDestructFunction(FTy, "_GLOBAL__D_a");
CodeGenFunction(*this).GenerateCXXGlobalDtorsFunc(Fn, CXXGlobalDtors);
AddGlobalDtor(Fn);
}
/// Emit the code necessary to initialize the given global variable.
void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
const VarDecl *D,
llvm::GlobalVariable *Addr,
bool PerformInit) {
// Check if we need to emit debug info for variable initializer.
if (D->hasAttr<NoDebugAttr>())
DebugInfo = nullptr; // disable debug info indefinitely for this function
StartFunction(GlobalDecl(D), getContext().VoidTy, Fn,
getTypes().arrangeNullaryFunction(),
FunctionArgList(), D->getLocation(),
D->getInit()->getExprLoc());
// Use guarded initialization if the global variable is weak. This
// occurs for, e.g., instantiated static data members and
// definitions explicitly marked weak.
if (Addr->hasWeakLinkage() || Addr->hasLinkOnceLinkage()) {
EmitCXXGuardedInit(*D, Addr, PerformInit);
} else {
EmitCXXGlobalVarDeclInit(*D, Addr, PerformInit);
}
FinishFunction();
}
void
CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
ArrayRef<llvm::Function *> Decls,
llvm::GlobalVariable *Guard) {
{
ArtificialLocation AL(*this, Builder);
StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
getTypes().arrangeNullaryFunction(), FunctionArgList());
// Emit an artificial location for this function.
AL.Emit();
llvm::BasicBlock *ExitBlock = nullptr;
if (Guard) {
// If we have a guard variable, check whether we've already performed
// these initializations. This happens for TLS initialization functions.
llvm::Value *GuardVal = Builder.CreateLoad(Guard);
llvm::Value *Uninit = Builder.CreateIsNull(GuardVal,
"guard.uninitialized");
// Mark as initialized before initializing anything else. If the
// initializers use previously-initialized thread_local vars, that's
// probably supposed to be OK, but the standard doesn't say.
Builder.CreateStore(llvm::ConstantInt::get(GuardVal->getType(),1), Guard);
llvm::BasicBlock *InitBlock = createBasicBlock("init");
ExitBlock = createBasicBlock("exit");
Builder.CreateCondBr(Uninit, InitBlock, ExitBlock);
EmitBlock(InitBlock);
}
RunCleanupsScope Scope(*this);
// When building in Objective-C++ ARC mode, create an autorelease pool
// around the global initializers.
if (getLangOpts().ObjCAutoRefCount && getLangOpts().CPlusPlus) {
llvm::Value *token = EmitObjCAutoreleasePoolPush();
EmitObjCAutoreleasePoolCleanup(token);
}
for (unsigned i = 0, e = Decls.size(); i != e; ++i)
if (Decls[i])
EmitRuntimeCall(Decls[i]);
Scope.ForceCleanup();
if (ExitBlock) {
Builder.CreateBr(ExitBlock);
EmitBlock(ExitBlock);
}
}
FinishFunction();
}
void CodeGenFunction::GenerateCXXGlobalDtorsFunc(llvm::Function *Fn,
const std::vector<std::pair<llvm::WeakVH, llvm::Constant*> >
&DtorsAndObjects) {
{
ArtificialLocation AL(*this, Builder);
StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
getTypes().arrangeNullaryFunction(), FunctionArgList());
// Emit an artificial location for this function.
AL.Emit();
// Emit the dtors, in reverse order from construction.
for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) {
llvm::Value *Callee = DtorsAndObjects[e - i - 1].first;
llvm::CallInst *CI = Builder.CreateCall(Callee,
DtorsAndObjects[e - i - 1].second);
// Make sure the call and the callee agree on calling convention.
if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
CI->setCallingConv(F->getCallingConv());
}
}
FinishFunction();
}
/// generateDestroyHelper - Generates a helper function which, when
/// invoked, destroys the given object.
llvm::Function *CodeGenFunction::generateDestroyHelper(
llvm::Constant *addr, QualType type, Destroyer *destroyer,
bool useEHCleanupForArray, const VarDecl *VD) {
FunctionArgList args;
ImplicitParamDecl dst(getContext(), nullptr, SourceLocation(), nullptr,
getContext().VoidPtrTy);
args.push_back(&dst);
const CGFunctionInfo &FI = CGM.getTypes().arrangeFreeFunctionDeclaration(
getContext().VoidTy, args, FunctionType::ExtInfo(), /*variadic=*/false);
llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI);
llvm::Function *fn = CGM.CreateGlobalInitOrDestructFunction(
FTy, "__cxx_global_array_dtor", VD->getLocation());
StartFunction(VD, getContext().VoidTy, fn, FI, args);
emitDestroy(addr, type, destroyer, useEHCleanupForArray);
FinishFunction();
return fn;
}
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