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//===--- CGBlocks.cpp - Emit LLVM Code for declarations ---------*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This contains code to emit blocks.
#include "CGBlocks.h"
#include "CGDebugInfo.h"
#include "CGObjCRuntime.h"
#include "CGOpenCLRuntime.h"
#include "CodeGenFunction.h"
#include "CodeGenModule.h"
#include "ConstantEmitter.h"
#include "TargetInfo.h"
#include "clang/AST/DeclObjC.h"
#include "clang/CodeGen/ConstantInitBuilder.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Module.h"
#include <algorithm>
#include <cstdio>
using namespace clang;
using namespace CodeGen;
CGBlockInfo::CGBlockInfo(const BlockDecl *block, StringRef name)
: Name(name), CXXThisIndex(0), CanBeGlobal(false), NeedsCopyDispose(false),
HasCXXObject(false), UsesStret(false), HasCapturedVariableLayout(false),
LocalAddress(Address::invalid()), StructureType(nullptr), Block(block),
DominatingIP(nullptr) {
// Skip asm prefix, if any. 'name' is usually taken directly from
// the mangled name of the enclosing function.
if (!name.empty() && name[0] == '\01')
name = name.substr(1);
// Anchor the vtable to this translation unit.
BlockByrefHelpers::~BlockByrefHelpers() {}
/// Build the given block as a global block.
static llvm::Constant *buildGlobalBlock(CodeGenModule &CGM,
const CGBlockInfo &blockInfo,
llvm::Constant *blockFn);
/// Build the helper function to copy a block.
static llvm::Constant *buildCopyHelper(CodeGenModule &CGM,
const CGBlockInfo &blockInfo) {
return CodeGenFunction(CGM).GenerateCopyHelperFunction(blockInfo);
/// Build the helper function to dispose of a block.
static llvm::Constant *buildDisposeHelper(CodeGenModule &CGM,
const CGBlockInfo &blockInfo) {
return CodeGenFunction(CGM).GenerateDestroyHelperFunction(blockInfo);
/// buildBlockDescriptor - Build the block descriptor meta-data for a block.
/// buildBlockDescriptor is accessed from 5th field of the Block_literal
/// meta-data and contains stationary information about the block literal.
/// Its definition will have 4 (or optinally 6) words.
/// \code
/// struct Block_descriptor {
/// unsigned long reserved;
/// unsigned long size; // size of Block_literal metadata in bytes.
/// void *copy_func_helper_decl; // optional copy helper.
/// void *destroy_func_decl; // optioanl destructor helper.
/// void *block_method_encoding_address; // @encode for block literal signature.
/// void *block_layout_info; // encoding of captured block variables.
/// };
/// \endcode
static llvm::Constant *buildBlockDescriptor(CodeGenModule &CGM,
const CGBlockInfo &blockInfo) {
ASTContext &C = CGM.getContext();
llvm::IntegerType *ulong =
llvm::PointerType *i8p = nullptr;
if (CGM.getLangOpts().OpenCL)
i8p =
CGM.getLLVMContext(), C.getTargetAddressSpace(LangAS::opencl_constant));
i8p = CGM.VoidPtrTy;
ConstantInitBuilder builder(CGM);
auto elements = builder.beginStruct();
// reserved
elements.addInt(ulong, 0);
// Size
// FIXME: What is the right way to say this doesn't fit? We should give
// a user diagnostic in that case. Better fix would be to change the
// API to size_t.
elements.addInt(ulong, blockInfo.BlockSize.getQuantity());
// Optional copy/dispose helpers.
if (blockInfo.NeedsCopyDispose) {
// copy_func_helper_decl
elements.add(buildCopyHelper(CGM, blockInfo));
// destroy_func_decl
elements.add(buildDisposeHelper(CGM, blockInfo));
// Signature. Mandatory ObjC-style method descriptor @encode sequence.
std::string typeAtEncoding =
CGM.GetAddrOfConstantCString(typeAtEncoding).getPointer(), i8p));
// GC layout.
if (C.getLangOpts().ObjC1) {
if (CGM.getLangOpts().getGC() != LangOptions::NonGC)
elements.add(CGM.getObjCRuntime().BuildGCBlockLayout(CGM, blockInfo));
elements.add(CGM.getObjCRuntime().BuildRCBlockLayout(CGM, blockInfo));
unsigned AddrSpace = 0;
if (C.getLangOpts().OpenCL)
AddrSpace = C.getTargetAddressSpace(LangAS::opencl_constant);
llvm::GlobalVariable *global =
/*constant*/ true,
return llvm::ConstantExpr::getBitCast(global, CGM.getBlockDescriptorType());
Purely notional variadic template describing the layout of a block.
template <class _ResultType, class... _ParamTypes, class... _CaptureTypes>
struct Block_literal {
/// Initialized to one of:
/// extern void *_NSConcreteStackBlock[];
/// extern void *_NSConcreteGlobalBlock[];
/// In theory, we could start one off malloc'ed by setting
/// BLOCK_NEEDS_FREE, giving it a refcount of 1, and using
/// this isa:
/// extern void *_NSConcreteMallocBlock[];
struct objc_class *isa;
/// These are the flags (with corresponding bit number) that the
/// compiler is actually supposed to know about.
/// 25. BLOCK_HAS_COPY_DISPOSE - indicates that the block
/// descriptor provides copy and dispose helper functions
/// 26. BLOCK_HAS_CXX_OBJ - indicates that there's a captured
/// object with a nontrivial destructor or copy constructor
/// 28. BLOCK_IS_GLOBAL - indicates that the block is allocated
/// as global memory
/// 29. BLOCK_USE_STRET - indicates that the block function
/// uses stret, which objc_msgSend needs to know about
/// 30. BLOCK_HAS_SIGNATURE - indicates that the block has an
/// @encoded signature string
/// And we're not supposed to manipulate these:
/// 24. BLOCK_NEEDS_FREE - indicates that the block has been moved
/// to malloc'ed memory
/// 27. BLOCK_IS_GC - indicates that the block has been moved to
/// to GC-allocated memory
/// Additionally, the bottom 16 bits are a reference count which
/// should be zero on the stack.
int flags;
/// Reserved; should be zero-initialized.
int reserved;
/// Function pointer generated from block literal.
_ResultType (*invoke)(Block_literal *, _ParamTypes...);
/// Block description metadata generated from block literal.
struct Block_descriptor *block_descriptor;
/// Captured values follow.
_CapturesTypes captures...;
namespace {
/// A chunk of data that we actually have to capture in the block.
struct BlockLayoutChunk {
CharUnits Alignment;
CharUnits Size;
Qualifiers::ObjCLifetime Lifetime;
const BlockDecl::Capture *Capture; // null for 'this'
llvm::Type *Type;
QualType FieldType;
BlockLayoutChunk(CharUnits align, CharUnits size,
Qualifiers::ObjCLifetime lifetime,
const BlockDecl::Capture *capture,
llvm::Type *type, QualType fieldType)
: Alignment(align), Size(size), Lifetime(lifetime),
Capture(capture), Type(type), FieldType(fieldType) {}
/// Tell the block info that this chunk has the given field index.
void setIndex(CGBlockInfo &info, unsigned index, CharUnits offset) {
if (!Capture) {
info.CXXThisIndex = index;
info.CXXThisOffset = offset;
} else {
auto C = CGBlockInfo::Capture::makeIndex(index, offset, FieldType);
info.Captures.insert({Capture->getVariable(), C});
/// Order by 1) all __strong together 2) next, all byfref together 3) next,
/// all __weak together. Preserve descending alignment in all situations.
bool operator<(const BlockLayoutChunk &left, const BlockLayoutChunk &right) {
if (left.Alignment != right.Alignment)
return left.Alignment > right.Alignment;
auto getPrefOrder = [](const BlockLayoutChunk &chunk) {
if (chunk.Capture && chunk.Capture->isByRef())
return 1;
if (chunk.Lifetime == Qualifiers::OCL_Strong)
return 0;
if (chunk.Lifetime == Qualifiers::OCL_Weak)
return 2;
return 3;
return getPrefOrder(left) < getPrefOrder(right);
} // end anonymous namespace
/// Determines if the given type is safe for constant capture in C++.
static bool isSafeForCXXConstantCapture(QualType type) {
const RecordType *recordType =
// Only records can be unsafe.
if (!recordType) return true;
const auto *record = cast<CXXRecordDecl>(recordType->getDecl());
// Maintain semantics for classes with non-trivial dtors or copy ctors.
if (!record->hasTrivialDestructor()) return false;
if (record->hasNonTrivialCopyConstructor()) return false;
// Otherwise, we just have to make sure there aren't any mutable
// fields that might have changed since initialization.
return !record->hasMutableFields();
/// It is illegal to modify a const object after initialization.
/// Therefore, if a const object has a constant initializer, we don't
/// actually need to keep storage for it in the block; we'll just
/// rematerialize it at the start of the block function. This is
/// acceptable because we make no promises about address stability of
/// captured variables.
static llvm::Constant *tryCaptureAsConstant(CodeGenModule &CGM,
CodeGenFunction *CGF,
const VarDecl *var) {
// Return if this is a function parameter. We shouldn't try to
// rematerialize default arguments of function parameters.
if (isa<ParmVarDecl>(var))
return nullptr;
QualType type = var->getType();
// We can only do this if the variable is const.
if (!type.isConstQualified()) return nullptr;
// Furthermore, in C++ we have to worry about mutable fields:
// C++ []p4:
// Except that any class member declared mutable can be
// modified, any attempt to modify a const object during its
// lifetime results in undefined behavior.
if (CGM.getLangOpts().CPlusPlus && !isSafeForCXXConstantCapture(type))
return nullptr;
// If the variable doesn't have any initializer (shouldn't this be
// invalid?), it's not clear what we should do. Maybe capture as
// zero?
const Expr *init = var->getInit();
if (!init) return nullptr;
return ConstantEmitter(CGM, CGF).tryEmitAbstractForInitializer(*var);
/// Get the low bit of a nonzero character count. This is the
/// alignment of the nth byte if the 0th byte is universally aligned.
static CharUnits getLowBit(CharUnits v) {
return CharUnits::fromQuantity(v.getQuantity() & (~v.getQuantity() + 1));
static void initializeForBlockHeader(CodeGenModule &CGM, CGBlockInfo &info,
SmallVectorImpl<llvm::Type*> &elementTypes) {
if (CGM.getLangOpts().OpenCL) {
// The header is basically 'struct { int; int; generic void *;
// custom_fields; }'. Assert that struct is packed.
auto GenericAS =
auto GenPtrAlign =
CharUnits::fromQuantity(CGM.getTarget().getPointerAlign(GenericAS) / 8);
auto GenPtrSize =
CharUnits::fromQuantity(CGM.getTarget().getPointerWidth(GenericAS) / 8);
assert(CGM.getIntSize() <= GenPtrSize);
assert(CGM.getIntAlign() <= GenPtrAlign);
assert((2 * CGM.getIntSize()).isMultipleOf(GenPtrAlign));
elementTypes.push_back(CGM.IntTy); /* total size */
elementTypes.push_back(CGM.IntTy); /* align */
.getGenericVoidPointerType()); /* invoke function */
unsigned Offset =
2 * CGM.getIntSize().getQuantity() + GenPtrSize.getQuantity();
unsigned BlockAlign = GenPtrAlign.getQuantity();
if (auto *Helper =
CGM.getTargetCodeGenInfo().getTargetOpenCLBlockHelper()) {
for (auto I : Helper->getCustomFieldTypes()) /* custom fields */ {
// TargetOpenCLBlockHelp needs to make sure the struct is packed.
// If necessary, add padding fields to the custom fields.
unsigned Align = CGM.getDataLayout().getABITypeAlignment(I);
if (BlockAlign < Align)
BlockAlign = Align;
assert(Offset % Align == 0);
Offset += CGM.getDataLayout().getTypeAllocSize(I);
info.BlockAlign = CharUnits::fromQuantity(BlockAlign);
info.BlockSize = CharUnits::fromQuantity(Offset);
} else {
// The header is basically 'struct { void *; int; int; void *; void *; }'.
// Assert that that struct is packed.
assert(CGM.getIntSize() <= CGM.getPointerSize());
assert(CGM.getIntAlign() <= CGM.getPointerAlign());
assert((2 * CGM.getIntSize()).isMultipleOf(CGM.getPointerAlign()));
info.BlockAlign = CGM.getPointerAlign();
info.BlockSize = 3 * CGM.getPointerSize() + 2 * CGM.getIntSize();
static QualType getCaptureFieldType(const CodeGenFunction &CGF,
const BlockDecl::Capture &CI) {
const VarDecl *VD = CI.getVariable();
// If the variable is captured by an enclosing block or lambda expression,
// use the type of the capture field.
if (CGF.BlockInfo && CI.isNested())
return CGF.BlockInfo->getCapture(VD).fieldType();
if (auto *FD = CGF.LambdaCaptureFields.lookup(VD))
return FD->getType();
return VD->getType();
/// Compute the layout of the given block. Attempts to lay the block
/// out with minimal space requirements.
static void computeBlockInfo(CodeGenModule &CGM, CodeGenFunction *CGF,
CGBlockInfo &info) {
ASTContext &C = CGM.getContext();
const BlockDecl *block = info.getBlockDecl();
SmallVector<llvm::Type*, 8> elementTypes;
initializeForBlockHeader(CGM, info, elementTypes);
bool hasNonConstantCustomFields = false;
if (auto *OpenCLHelper =
hasNonConstantCustomFields =
if (!block->hasCaptures() && !hasNonConstantCustomFields) {
info.StructureType =
llvm::StructType::get(CGM.getLLVMContext(), elementTypes, true);
info.CanBeGlobal = true;
else if (C.getLangOpts().ObjC1 &&
CGM.getLangOpts().getGC() == LangOptions::NonGC)
info.HasCapturedVariableLayout = true;
// Collect the layout chunks.
SmallVector<BlockLayoutChunk, 16> layout;
layout.reserve(block->capturesCXXThis() +
(block->capture_end() - block->capture_begin()));
CharUnits maxFieldAlign;
// First, 'this'.
if (block->capturesCXXThis()) {
assert(CGF && CGF->CurFuncDecl && isa<CXXMethodDecl>(CGF->CurFuncDecl) &&
"Can't capture 'this' outside a method");
QualType thisType = cast<CXXMethodDecl>(CGF->CurFuncDecl)->getThisType(C);
// Theoretically, this could be in a different address space, so
// don't assume standard pointer size/align.
llvm::Type *llvmType = CGM.getTypes().ConvertType(thisType);
std::pair<CharUnits,CharUnits> tinfo
= CGM.getContext().getTypeInfoInChars(thisType);
maxFieldAlign = std::max(maxFieldAlign, tinfo.second);
layout.push_back(BlockLayoutChunk(tinfo.second, tinfo.first,
nullptr, llvmType, thisType));
// Next, all the block captures.
for (const auto &CI : block->captures()) {
const VarDecl *variable = CI.getVariable();
if (CI.isByRef()) {
// We have to copy/dispose of the __block reference.
info.NeedsCopyDispose = true;
// Just use void* instead of a pointer to the byref type.
CharUnits align = CGM.getPointerAlign();
maxFieldAlign = std::max(maxFieldAlign, align);
layout.push_back(BlockLayoutChunk(align, CGM.getPointerSize(),
Qualifiers::OCL_None, &CI,
CGM.VoidPtrTy, variable->getType()));
// Otherwise, build a layout chunk with the size and alignment of
// the declaration.
if (llvm::Constant *constant = tryCaptureAsConstant(CGM, CGF, variable)) {
info.Captures[variable] = CGBlockInfo::Capture::makeConstant(constant);
// If we have a lifetime qualifier, honor it for capture purposes.
// That includes *not* copying it if it's __unsafe_unretained.
Qualifiers::ObjCLifetime lifetime =
if (lifetime) {
switch (lifetime) {
case Qualifiers::OCL_None: llvm_unreachable("impossible");
case Qualifiers::OCL_ExplicitNone:
case Qualifiers::OCL_Autoreleasing:
case Qualifiers::OCL_Strong:
case Qualifiers::OCL_Weak:
info.NeedsCopyDispose = true;
// Block pointers require copy/dispose. So do Objective-C pointers.
} else if (variable->getType()->isObjCRetainableType()) {
// But honor the inert __unsafe_unretained qualifier, which doesn't
// actually make it into the type system.
if (variable->getType()->isObjCInertUnsafeUnretainedType()) {
lifetime = Qualifiers::OCL_ExplicitNone;
} else {
info.NeedsCopyDispose = true;
// used for mrr below.
lifetime = Qualifiers::OCL_Strong;
// So do types that require non-trivial copy construction.
} else if (CI.hasCopyExpr()) {
info.NeedsCopyDispose = true;
info.HasCXXObject = true;
// And so do types with destructors.
} else if (CGM.getLangOpts().CPlusPlus) {
if (const CXXRecordDecl *record =
variable->getType()->getAsCXXRecordDecl()) {
if (!record->hasTrivialDestructor()) {
info.HasCXXObject = true;
info.NeedsCopyDispose = true;
QualType VT = getCaptureFieldType(*CGF, CI);
CharUnits size = C.getTypeSizeInChars(VT);
CharUnits align = C.getDeclAlign(variable);
maxFieldAlign = std::max(maxFieldAlign, align);
llvm::Type *llvmType =
BlockLayoutChunk(align, size, lifetime, &CI, llvmType, VT));
// If that was everything, we're done here.
if (layout.empty()) {
info.StructureType =
llvm::StructType::get(CGM.getLLVMContext(), elementTypes, true);
info.CanBeGlobal = true;
// Sort the layout by alignment. We have to use a stable sort here
// to get reproducible results. There should probably be an
// llvm::array_pod_stable_sort.
std::stable_sort(layout.begin(), layout.end());
// Needed for blocks layout info.
info.BlockHeaderForcedGapOffset = info.BlockSize;
info.BlockHeaderForcedGapSize = CharUnits::Zero();
CharUnits &blockSize = info.BlockSize;
info.BlockAlign = std::max(maxFieldAlign, info.BlockAlign);
// Assuming that the first byte in the header is maximally aligned,
// get the alignment of the first byte following the header.
CharUnits endAlign = getLowBit(blockSize);
// If the end of the header isn't satisfactorily aligned for the
// maximum thing, look for things that are okay with the header-end
// alignment, and keep appending them until we get something that's
// aligned right. This algorithm is only guaranteed optimal if
// that condition is satisfied at some point; otherwise we can get
// things like:
// header // next byte has alignment 4
// something_with_size_5; // next byte has alignment 1
// something_with_alignment_8;
// which has 7 bytes of padding, as opposed to the naive solution
// which might have less (?).
if (endAlign < maxFieldAlign) {
li = layout.begin() + 1, le = layout.end();
// Look for something that the header end is already
// satisfactorily aligned for.
for (; li != le && endAlign < li->Alignment; ++li)
// If we found something that's naturally aligned for the end of
// the header, keep adding things...
if (li != le) {
SmallVectorImpl<BlockLayoutChunk>::iterator first = li;
for (; li != le; ++li) {
assert(endAlign >= li->Alignment);
li->setIndex(info, elementTypes.size(), blockSize);
blockSize += li->Size;
endAlign = getLowBit(blockSize);
// ...until we get to the alignment of the maximum field.
if (endAlign >= maxFieldAlign) {
// Don't re-append everything we just appended.
layout.erase(first, li);
assert(endAlign == getLowBit(blockSize));
// At this point, we just have to add padding if the end align still
// isn't aligned right.
if (endAlign < maxFieldAlign) {
CharUnits newBlockSize = blockSize.alignTo(maxFieldAlign);
CharUnits padding = newBlockSize - blockSize;
// If we haven't yet added any fields, remember that there was an
// initial gap; this need to go into the block layout bit map.
if (blockSize == info.BlockHeaderForcedGapOffset) {
info.BlockHeaderForcedGapSize = padding;
blockSize = newBlockSize;
endAlign = getLowBit(blockSize); // might be > maxFieldAlign
assert(endAlign >= maxFieldAlign);
assert(endAlign == getLowBit(blockSize));
// Slam everything else on now. This works because they have
// strictly decreasing alignment and we expect that size is always a
// multiple of alignment.
for (SmallVectorImpl<BlockLayoutChunk>::iterator
li = layout.begin(), le = layout.end(); li != le; ++li) {
if (endAlign < li->Alignment) {
// size may not be multiple of alignment. This can only happen with
// an over-aligned variable. We will be adding a padding field to
// make the size be multiple of alignment.
CharUnits padding = li->Alignment - endAlign;
blockSize += padding;
endAlign = getLowBit(blockSize);
assert(endAlign >= li->Alignment);
li->setIndex(info, elementTypes.size(), blockSize);
blockSize += li->Size;
endAlign = getLowBit(blockSize);
info.StructureType =
llvm::StructType::get(CGM.getLLVMContext(), elementTypes, true);
/// Enter the scope of a block. This should be run at the entrance to
/// a full-expression so that the block's cleanups are pushed at the
/// right place in the stack.
static void enterBlockScope(CodeGenFunction &CGF, BlockDecl *block) {
// Allocate the block info and place it at the head of the list.
CGBlockInfo &blockInfo =
*new CGBlockInfo(block, CGF.CurFn->getName());
blockInfo.NextBlockInfo = CGF.FirstBlockInfo;
CGF.FirstBlockInfo = &blockInfo;
// Compute information about the layout, etc., of this block,
// pushing cleanups as necessary.
computeBlockInfo(CGF.CGM, &CGF, blockInfo);
// Nothing else to do if it can be global.
if (blockInfo.CanBeGlobal) return;
// Make the allocation for the block.
blockInfo.LocalAddress = CGF.CreateTempAlloca(blockInfo.StructureType,
blockInfo.BlockAlign, "block");
// If there are cleanups to emit, enter them (but inactive).
if (!blockInfo.NeedsCopyDispose) return;
// Walk through the captures (in order) and find the ones not
// captured by constant.
for (const auto &CI : block->captures()) {
// Ignore __block captures; there's nothing special in the
// on-stack block that we need to do for them.
if (CI.isByRef()) continue;
// Ignore variables that are constant-captured.
const VarDecl *variable = CI.getVariable();
CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
if (capture.isConstant()) continue;
// Ignore objects that aren't destructed.
QualType VT = getCaptureFieldType(CGF, CI);
QualType::DestructionKind dtorKind = VT.isDestructedType();
if (dtorKind == QualType::DK_none) continue;
CodeGenFunction::Destroyer *destroyer;
// Block captures count as local values and have imprecise semantics.
// They also can't be arrays, so need to worry about that.
// For const-qualified captures, emit clang.arc.use to ensure the captured
// object doesn't get released while we are still depending on its validity
// within the block.
if (VT.isConstQualified() &&
VT.getObjCLifetime() == Qualifiers::OCL_Strong &&
CGF.CGM.getCodeGenOpts().OptimizationLevel != 0) {
assert(CGF.CGM.getLangOpts().ObjCAutoRefCount &&
"expected ObjC ARC to be enabled");
destroyer = CodeGenFunction::emitARCIntrinsicUse;
} else if (dtorKind == QualType::DK_objc_strong_lifetime) {
destroyer = CodeGenFunction::destroyARCStrongImprecise;
} else {
destroyer = CGF.getDestroyer(dtorKind);
// GEP down to the address.
Address addr = CGF.Builder.CreateStructGEP(blockInfo.LocalAddress,
// We can use that GEP as the dominating IP.
if (!blockInfo.DominatingIP)
blockInfo.DominatingIP = cast<llvm::Instruction>(addr.getPointer());
CleanupKind cleanupKind = InactiveNormalCleanup;
bool useArrayEHCleanup = CGF.needsEHCleanup(dtorKind);
if (useArrayEHCleanup)
cleanupKind = InactiveNormalAndEHCleanup;
CGF.pushDestroy(cleanupKind, addr, VT,
destroyer, useArrayEHCleanup);
// Remember where that cleanup was.
/// Enter a full-expression with a non-trivial number of objects to
/// clean up. This is in this file because, at the moment, the only
/// kind of cleanup object is a BlockDecl*.
void CodeGenFunction::enterNonTrivialFullExpression(const ExprWithCleanups *E) {
assert(E->getNumObjects() != 0);
ArrayRef<ExprWithCleanups::CleanupObject> cleanups = E->getObjects();
for (ArrayRef<ExprWithCleanups::CleanupObject>::iterator
i = cleanups.begin(), e = cleanups.end(); i != e; ++i) {
enterBlockScope(*this, *i);
/// Find the layout for the given block in a linked list and remove it.
static CGBlockInfo *findAndRemoveBlockInfo(CGBlockInfo **head,
const BlockDecl *block) {
while (true) {
assert(head && *head);
CGBlockInfo *cur = *head;
// If this is the block we're looking for, splice it out of the list.
if (cur->getBlockDecl() == block) {
*head = cur->NextBlockInfo;
return cur;
head = &cur->NextBlockInfo;
/// Destroy a chain of block layouts.
void CodeGenFunction::destroyBlockInfos(CGBlockInfo *head) {
assert(head && "destroying an empty chain");
do {
CGBlockInfo *cur = head;
head = cur->NextBlockInfo;
delete cur;
} while (head != nullptr);
/// Emit a block literal expression in the current function.
llvm::Value *CodeGenFunction::EmitBlockLiteral(const BlockExpr *blockExpr,
llvm::Function **InvokeF) {
// If the block has no captures, we won't have a pre-computed
// layout for it.
if (!blockExpr->getBlockDecl()->hasCaptures()) {
// The block literal is emitted as a global variable, and the block invoke
// function has to be extracted from its initializer.
if (llvm::Constant *Block = CGM.getAddrOfGlobalBlockIfEmitted(blockExpr)) {
if (InvokeF) {
auto *GV = cast<llvm::GlobalVariable>(
auto *BlockInit = cast<llvm::ConstantStruct>(GV->getInitializer());
*InvokeF = cast<llvm::Function>(
return Block;
CGBlockInfo blockInfo(blockExpr->getBlockDecl(), CurFn->getName());
computeBlockInfo(CGM, this, blockInfo);
blockInfo.BlockExpression = blockExpr;
return EmitBlockLiteral(blockInfo, InvokeF);
// Find the block info for this block and take ownership of it.
std::unique_ptr<CGBlockInfo> blockInfo;
blockInfo->BlockExpression = blockExpr;
return EmitBlockLiteral(*blockInfo, InvokeF);
llvm::Value *CodeGenFunction::EmitBlockLiteral(const CGBlockInfo &blockInfo,
llvm::Function **InvokeF) {
bool IsOpenCL = CGM.getContext().getLangOpts().OpenCL;
auto GenVoidPtrTy =
IsOpenCL ? CGM.getOpenCLRuntime().getGenericVoidPointerType() : VoidPtrTy;
LangAS GenVoidPtrAddr = IsOpenCL ? LangAS::opencl_generic : LangAS::Default;
auto GenVoidPtrSize = CharUnits::fromQuantity(
CGM.getContext().getTargetAddressSpace(GenVoidPtrAddr)) /
// Using the computed layout, generate the actual block function.
bool isLambdaConv = blockInfo.getBlockDecl()->isConversionFromLambda();
auto *InvokeFn = CodeGenFunction(CGM, true).GenerateBlockFunction(
CurGD, blockInfo, LocalDeclMap, isLambdaConv, blockInfo.CanBeGlobal);
if (InvokeF)
*InvokeF = InvokeFn;
auto *blockFn = llvm::ConstantExpr::getPointerCast(InvokeFn, GenVoidPtrTy);
// If there is nothing to capture, we can emit this as a global block.
if (blockInfo.CanBeGlobal)
return CGM.getAddrOfGlobalBlockIfEmitted(blockInfo.BlockExpression);
// Otherwise, we have to emit this as a local block.
Address blockAddr = blockInfo.LocalAddress;
assert(blockAddr.isValid() && "block has no address!");
llvm::Constant *isa;
llvm::Constant *descriptor;
BlockFlags flags;
if (!IsOpenCL) {
isa = llvm::ConstantExpr::getBitCast(CGM.getNSConcreteStackBlock(),
// Build the block descriptor.
descriptor = buildBlockDescriptor(CGM, blockInfo);
// Compute the initial on-stack block flags.
if (blockInfo.HasCapturedVariableLayout)
if (blockInfo.NeedsCopyDispose)
if (blockInfo.HasCXXObject)
if (blockInfo.UsesStret)
auto projectField =
[&](unsigned index, CharUnits offset, const Twine &name) -> Address {
return Builder.CreateStructGEP(blockAddr, index, offset, name);
auto storeField =
[&](llvm::Value *value, unsigned index, CharUnits offset,
const Twine &name) {
Builder.CreateStore(value, projectField(index, offset, name));
// Initialize the block header.
// We assume all the header fields are densely packed.
unsigned index = 0;
CharUnits offset;
auto addHeaderField =
[&](llvm::Value *value, CharUnits size, const Twine &name) {
storeField(value, index, offset, name);
offset += size;
if (!IsOpenCL) {
addHeaderField(isa, getPointerSize(), "block.isa");
addHeaderField(llvm::ConstantInt::get(IntTy, flags.getBitMask()),
getIntSize(), "block.flags");
addHeaderField(llvm::ConstantInt::get(IntTy, 0), getIntSize(),
} else {
llvm::ConstantInt::get(IntTy, blockInfo.BlockSize.getQuantity()),
getIntSize(), "block.size");
llvm::ConstantInt::get(IntTy, blockInfo.BlockAlign.getQuantity()),
getIntSize(), "block.align");
addHeaderField(blockFn, GenVoidPtrSize, "block.invoke");
if (!IsOpenCL)
addHeaderField(descriptor, getPointerSize(), "block.descriptor");
else if (auto *Helper =
CGM.getTargetCodeGenInfo().getTargetOpenCLBlockHelper()) {
for (auto I : Helper->getCustomFieldValues(*this, blockInfo)) {
// Finally, capture all the values into the block.
const BlockDecl *blockDecl = blockInfo.getBlockDecl();
// First, 'this'.
if (blockDecl->capturesCXXThis()) {
Address addr = projectField(blockInfo.CXXThisIndex, blockInfo.CXXThisOffset,
Builder.CreateStore(LoadCXXThis(), addr);
// Next, captured variables.
for (const auto &CI : blockDecl->captures()) {
const VarDecl *variable = CI.getVariable();
const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
// Ignore constant captures.
if (capture.isConstant()) continue;
QualType type = capture.fieldType();
// This will be a [[type]]*, except that a byref entry will just be
// an i8**.
Address blockField =
projectField(capture.getIndex(), capture.getOffset(), "block.captured");
// Compute the address of the thing we're going to move into the
// block literal.
Address src = Address::invalid();
if (blockDecl->isConversionFromLambda()) {
// The lambda capture in a lambda's conversion-to-block-pointer is
// special; we'll simply emit it directly.
src = Address::invalid();
} else if (CI.isByRef()) {
if (BlockInfo && CI.isNested()) {
// We need to use the capture from the enclosing block.
const CGBlockInfo::Capture &enclosingCapture =
// This is a [[type]]*, except that a byref entry wil just be an i8**.
src = Builder.CreateStructGEP(LoadBlockStruct(),
} else {
auto I = LocalDeclMap.find(variable);
assert(I != LocalDeclMap.end());
src = I->second;
} else {
DeclRefExpr declRef(const_cast<VarDecl *>(variable),
/*RefersToEnclosingVariableOrCapture*/ CI.isNested(),
type.getNonReferenceType(), VK_LValue,
src = EmitDeclRefLValue(&declRef).getAddress();
// For byrefs, we just write the pointer to the byref struct into
// the block field. There's no need to chase the forwarding
// pointer at this point, since we're building something that will
// live a shorter life than the stack byref anyway.
if (CI.isByRef()) {
// Get a void* that points to the byref struct.
llvm::Value *byrefPointer;
if (CI.isNested())
byrefPointer = Builder.CreateLoad(src, "byref.capture");
byrefPointer = Builder.CreateBitCast(src.getPointer(), VoidPtrTy);
// Write that void* into the capture field.
Builder.CreateStore(byrefPointer, blockField);
// If we have a copy constructor, evaluate that into the block field.
} else if (const Expr *copyExpr = CI.getCopyExpr()) {
if (blockDecl->isConversionFromLambda()) {
// If we have a lambda conversion, emit the expression
// directly into the block instead.
AggValueSlot Slot =
AggValueSlot::forAddr(blockField, Qualifiers(),
EmitAggExpr(copyExpr, Slot);
} else {
EmitSynthesizedCXXCopyCtor(blockField, src, copyExpr);
// If it's a reference variable, copy the reference into the block field.
} else if (type->isReferenceType()) {
Builder.CreateStore(src.getPointer(), blockField);
// If type is const-qualified, copy the value into the block field.
} else if (type.isConstQualified() &&
type.getObjCLifetime() == Qualifiers::OCL_Strong &&
CGM.getCodeGenOpts().OptimizationLevel != 0) {
llvm::Value *value = Builder.CreateLoad(src, "captured");
Builder.CreateStore(value, blockField);
// If this is an ARC __strong block-pointer variable, don't do a
// block copy.
// TODO: this can be generalized into the normal initialization logic:
// we should never need to do a block-copy when initializing a local
// variable, because the local variable's lifetime should be strictly
// contained within the stack block's.
} else if (type.getObjCLifetime() == Qualifiers::OCL_Strong &&
type->isBlockPointerType()) {
// Load the block and do a simple retain.
llvm::Value *value = Builder.CreateLoad(src, "block.captured_block");
value = EmitARCRetainNonBlock(value);
// Do a primitive store to the block field.
Builder.CreateStore(value, blockField);
// Otherwise, fake up a POD copy into the block field.
} else {
// Fake up a new variable so that EmitScalarInit doesn't think
// we're referring to the variable in its own initializer.
ImplicitParamDecl BlockFieldPseudoVar(getContext(), type,
// We use one of these or the other depending on whether the
// reference is nested.
DeclRefExpr declRef(const_cast<VarDecl *>(variable),
/*RefersToEnclosingVariableOrCapture*/ CI.isNested(),
type, VK_LValue, SourceLocation());
ImplicitCastExpr l2r(ImplicitCastExpr::OnStack, type, CK_LValueToRValue,
&declRef, VK_RValue);
// FIXME: Pass a specific location for the expr init so that the store is
// attributed to a reasonable location - otherwise it may be attributed to
// locations of subexpressions in the initialization.
EmitExprAsInit(&l2r, &BlockFieldPseudoVar,
MakeAddrLValue(blockField, type, AlignmentSource::Decl),
/*captured by init*/ false);
// Activate the cleanup if layout pushed one.
if (!CI.isByRef()) {
EHScopeStack::stable_iterator cleanup = capture.getCleanup();
if (cleanup.isValid())
ActivateCleanupBlock(cleanup, blockInfo.DominatingIP);
// Cast to the converted block-pointer type, which happens (somewhat
// unfortunately) to be a pointer to function type.
llvm::Value *result = Builder.CreatePointerCast(
blockAddr.getPointer(), ConvertType(blockInfo.getBlockExpr()->getType()));
return result;
llvm::Type *CodeGenModule::getBlockDescriptorType() {
if (BlockDescriptorType)
return BlockDescriptorType;
llvm::Type *UnsignedLongTy =
// struct __block_descriptor {
// unsigned long reserved;
// unsigned long block_size;
// // later, the following will be added
// struct {
// void (*copyHelper)();
// void (*copyHelper)();
// } helpers; // !!! optional
// const char *signature; // the block signature
// const char *layout; // reserved
// };
BlockDescriptorType = llvm::StructType::create(
"struct.__block_descriptor", UnsignedLongTy, UnsignedLongTy);
// Now form a pointer to that.
unsigned AddrSpace = 0;
if (getLangOpts().OpenCL)
AddrSpace = getContext().getTargetAddressSpace(LangAS::opencl_constant);
BlockDescriptorType = llvm::PointerType::get(BlockDescriptorType, AddrSpace);
return BlockDescriptorType;
llvm::Type *CodeGenModule::getGenericBlockLiteralType() {
if (GenericBlockLiteralType)
return GenericBlockLiteralType;
llvm::Type *BlockDescPtrTy = getBlockDescriptorType();
if (getLangOpts().OpenCL) {
// struct __opencl_block_literal_generic {
// int __size;
// int __align;
// __generic void *__invoke;
// /* custom fields */
// };
SmallVector<llvm::Type *, 8> StructFields(
{IntTy, IntTy, getOpenCLRuntime().getGenericVoidPointerType()});
if (auto *Helper = getTargetCodeGenInfo().getTargetOpenCLBlockHelper()) {
for (auto I : Helper->getCustomFieldTypes())
GenericBlockLiteralType = llvm::StructType::create(
StructFields, "struct.__opencl_block_literal_generic");
} else {
// struct __block_literal_generic {
// void *__isa;
// int __flags;
// int __reserved;
// void (*__invoke)(void *);
// struct __block_descriptor *__descriptor;
// };
GenericBlockLiteralType =
llvm::StructType::create("struct.__block_literal_generic", VoidPtrTy,
IntTy, IntTy, VoidPtrTy, BlockDescPtrTy);
return GenericBlockLiteralType;
RValue CodeGenFunction::EmitBlockCallExpr(const CallExpr *E,
ReturnValueSlot ReturnValue) {
const BlockPointerType *BPT =
llvm::Value *BlockPtr = EmitScalarExpr(E->getCallee());
// Get a pointer to the generic block literal.
// For OpenCL we generate generic AS void ptr to be able to reuse the same
// block definition for blocks with captures generated as private AS local
// variables and without captures generated as global AS program scope
// variables.
unsigned AddrSpace = 0;
if (getLangOpts().OpenCL)
AddrSpace = getContext().getTargetAddressSpace(LangAS::opencl_generic);
llvm::Type *BlockLiteralTy =
llvm::PointerType::get(CGM.getGenericBlockLiteralType(), AddrSpace);
// Bitcast the callee to a block literal.
BlockPtr =
Builder.CreatePointerCast(BlockPtr, BlockLiteralTy, "block.literal");
// Get the function pointer from the literal.
llvm::Value *FuncPtr =
Builder.CreateStructGEP(CGM.getGenericBlockLiteralType(), BlockPtr,
CGM.getLangOpts().OpenCL ? 2 : 3);
// Add the block literal.
CallArgList Args;
QualType VoidPtrQualTy = getContext().VoidPtrTy;
llvm::Type *GenericVoidPtrTy = VoidPtrTy;
if (getLangOpts().OpenCL) {
GenericVoidPtrTy = CGM.getOpenCLRuntime().getGenericVoidPointerType();
VoidPtrQualTy =
getContext().VoidTy, LangAS::opencl_generic));
BlockPtr = Builder.CreatePointerCast(BlockPtr, GenericVoidPtrTy);
Args.add(RValue::get(BlockPtr), VoidPtrQualTy);
QualType FnType = BPT->getPointeeType();
// And the rest of the arguments.
EmitCallArgs(Args, FnType->getAs<FunctionProtoType>(), E->arguments());
// Load the function.
llvm::Value *Func = Builder.CreateAlignedLoad(FuncPtr, getPointerAlign());
const FunctionType *FuncTy = FnType->castAs<FunctionType>();
const CGFunctionInfo &FnInfo =
CGM.getTypes().arrangeBlockFunctionCall(Args, FuncTy);
// Cast the function pointer to the right type.
llvm::Type *BlockFTy = CGM.getTypes().GetFunctionType(FnInfo);
llvm::Type *BlockFTyPtr = llvm::PointerType::getUnqual(BlockFTy);
Func = Builder.CreatePointerCast(Func, BlockFTyPtr);
// Prepare the callee.
CGCallee Callee(CGCalleeInfo(), Func);
// And call the block.
return EmitCall(FnInfo, Callee, ReturnValue, Args);
Address CodeGenFunction::GetAddrOfBlockDecl(const VarDecl *variable,
bool isByRef) {
assert(BlockInfo && "evaluating block ref without block information?");
const CGBlockInfo::Capture &capture = BlockInfo->getCapture(variable);
// Handle constant captures.
if (capture.isConstant()) return LocalDeclMap.find(variable)->second;
Address addr =
Builder.CreateStructGEP(LoadBlockStruct(), capture.getIndex(),
capture.getOffset(), "block.capture.addr");
if (isByRef) {
// addr should be a void** right now. Load, then cast the result
// to byref*.
auto &byrefInfo = getBlockByrefInfo(variable);
addr = Address(Builder.CreateLoad(addr), byrefInfo.ByrefAlignment);
auto byrefPointerType = llvm::PointerType::get(byrefInfo.Type, 0);
addr = Builder.CreateBitCast(addr, byrefPointerType, "byref.addr");
addr = emitBlockByrefAddress(addr, byrefInfo, /*follow*/ true,
if (capture.fieldType()->isReferenceType())
addr = EmitLoadOfReference(MakeAddrLValue(addr, capture.fieldType()));
return addr;
void CodeGenModule::setAddrOfGlobalBlock(const BlockExpr *BE,
llvm::Constant *Addr) {
bool Ok = EmittedGlobalBlocks.insert(std::make_pair(BE, Addr)).second;
assert(Ok && "Trying to replace an already-existing global block!");
llvm::Constant *
CodeGenModule::GetAddrOfGlobalBlock(const BlockExpr *BE,
StringRef Name) {
if (llvm::Constant *Block = getAddrOfGlobalBlockIfEmitted(BE))
return Block;
CGBlockInfo blockInfo(BE->getBlockDecl(), Name);
blockInfo.BlockExpression = BE;
// Compute information about the layout, etc., of this block.
computeBlockInfo(*this, nullptr, blockInfo);
// Using that metadata, generate the actual block function.
CodeGenFunction::DeclMapTy LocalDeclMap;
GlobalDecl(), blockInfo, LocalDeclMap,
/*IsLambdaConversionToBlock*/ false, /*BuildGlobalBlock*/ true);
return getAddrOfGlobalBlockIfEmitted(BE);
static llvm::Constant *buildGlobalBlock(CodeGenModule &CGM,
const CGBlockInfo &blockInfo,
llvm::Constant *blockFn) {
// Callers should detect this case on their own: calling this function
// generally requires computing layout information, which is a waste of time
// if we've already emitted this block.
assert(!CGM.getAddrOfGlobalBlockIfEmitted(blockInfo.BlockExpression) &&
"Refusing to re-emit a global block.");
// Generate the constants for the block literal initializer.
ConstantInitBuilder builder(CGM);
auto fields = builder.beginStruct();
bool IsOpenCL = CGM.getLangOpts().OpenCL;
if (!IsOpenCL) {
// isa
// __flags
if (blockInfo.UsesStret)
fields.addInt(CGM.IntTy, flags.getBitMask());
// Reserved
fields.addInt(CGM.IntTy, 0);
} else {
fields.addInt(CGM.IntTy, blockInfo.BlockSize.getQuantity());
fields.addInt(CGM.IntTy, blockInfo.BlockAlign.getQuantity());
// Function
if (!IsOpenCL) {
// Descriptor
fields.add(buildBlockDescriptor(CGM, blockInfo));
} else if (auto *Helper =
CGM.getTargetCodeGenInfo().getTargetOpenCLBlockHelper()) {
for (auto I : Helper->getCustomFieldValues(CGM, blockInfo)) {
unsigned AddrSpace = 0;
if (CGM.getContext().getLangOpts().OpenCL)
AddrSpace = CGM.getContext().getTargetAddressSpace(LangAS::opencl_global);
llvm::Constant *literal = fields.finishAndCreateGlobal(
"__block_literal_global", blockInfo.BlockAlign,
/*constant*/ true, llvm::GlobalVariable::InternalLinkage, AddrSpace);
// Return a constant of the appropriately-casted type.
llvm::Type *RequiredType =
llvm::Constant *Result =
llvm::ConstantExpr::getPointerCast(literal, RequiredType);
CGM.setAddrOfGlobalBlock(blockInfo.BlockExpression, Result);
return Result;
void CodeGenFunction::setBlockContextParameter(const ImplicitParamDecl *D,
unsigned argNum,
llvm::Value *arg) {
assert(BlockInfo && "not emitting prologue of block invocation function?!");
// Allocate a stack slot like for any local variable to guarantee optimal
// debug info at -O0. The mem2reg pass will eliminate it when optimizing.
Address alloc = CreateMemTemp(D->getType(), D->getName() + ".addr");
Builder.CreateStore(arg, alloc);
if (CGDebugInfo *DI = getDebugInfo()) {
if (CGM.getCodeGenOpts().getDebugInfo() >=
codegenoptions::LimitedDebugInfo) {
*BlockInfo, D->getName(), argNum,
cast<llvm::AllocaInst>(alloc.getPointer()), Builder);
SourceLocation StartLoc = BlockInfo->getBlockExpr()->getBody()->getLocStart();
ApplyDebugLocation Scope(*this, StartLoc);
// Instead of messing around with LocalDeclMap, just set the value
// directly as BlockPointer.
BlockPointer = Builder.CreatePointerCast(
? getContext().getTargetAddressSpace(LangAS::opencl_generic)
: 0),
Address CodeGenFunction::LoadBlockStruct() {
assert(BlockInfo && "not in a block invocation function!");
assert(BlockPointer && "no block pointer set!");
return Address(BlockPointer, BlockInfo->BlockAlign);
llvm::Function *
CodeGenFunction::GenerateBlockFunction(GlobalDecl GD,
const CGBlockInfo &blockInfo,
const DeclMapTy &ldm,
bool IsLambdaConversionToBlock,
bool BuildGlobalBlock) {
const BlockDecl *blockDecl = blockInfo.getBlockDecl();
CurGD = GD;
CurEHLocation = blockInfo.getBlockExpr()->getLocEnd();
BlockInfo = &blockInfo;
// Arrange for local static and local extern declarations to appear
// to be local to this function as well, in case they're directly
// referenced in a block.
for (DeclMapTy::const_iterator i = ldm.begin(), e = ldm.end(); i != e; ++i) {
const auto *var = dyn_cast<VarDecl>(i->first);
if (var && !var->hasLocalStorage())
setAddrOfLocalVar(var, i->second);
// Begin building the function declaration.
// Build the argument list.
FunctionArgList args;
// The first argument is the block pointer. Just take it as a void*
// and cast it later.
QualType selfTy = getContext().VoidPtrTy;
// For OpenCL passed block pointer can be private AS local variable or
// global AS program scope variable (for the case with and without captures).
// Generic AS is used therefore to be able to accommodate both private and
// generic AS in one implementation.
if (getLangOpts().OpenCL)
selfTy = getContext().getPointerType(getContext().getAddrSpaceQualType(
getContext().VoidTy, LangAS::opencl_generic));
IdentifierInfo *II = &CGM.getContext().Idents.get(".block_descriptor");
ImplicitParamDecl SelfDecl(getContext(), const_cast<BlockDecl *>(blockDecl),
SourceLocation(), II, selfTy,
// Now add the rest of the parameters.
args.append(blockDecl->param_begin(), blockDecl->param_end());
// Create the function declaration.
const FunctionProtoType *fnType = blockInfo.getBlockExpr()->getFunctionType();
const CGFunctionInfo &fnInfo =
CGM.getTypes().arrangeBlockFunctionDeclaration(fnType, args);
if (CGM.ReturnSlotInterferesWithArgs(fnInfo))
blockInfo.UsesStret = true;
llvm::FunctionType *fnLLVMType = CGM.getTypes().GetFunctionType(fnInfo);
StringRef name = CGM.getBlockMangledName(GD, blockDecl);
llvm::Function *fn = llvm::Function::Create(
fnLLVMType, llvm::GlobalValue::InternalLinkage, name, &CGM.getModule());
CGM.SetInternalFunctionAttributes(blockDecl, fn, fnInfo);
if (BuildGlobalBlock) {
auto GenVoidPtrTy = getContext().getLangOpts().OpenCL
? CGM.getOpenCLRuntime().getGenericVoidPointerType()
: VoidPtrTy;
buildGlobalBlock(CGM, blockInfo,
llvm::ConstantExpr::getPointerCast(fn, GenVoidPtrTy));
// Begin generating the function.
StartFunction(blockDecl, fnType->getReturnType(), fn, fnInfo, args,
// Okay. Undo some of what StartFunction did.
// At -O0 we generate an explicit alloca for the BlockPointer, so the RA
// won't delete the dbg.declare intrinsics for captured variables.
llvm::Value *BlockPointerDbgLoc = BlockPointer;
if (CGM.getCodeGenOpts().OptimizationLevel == 0) {
// Allocate a stack slot for it, so we can point the debugger to it
Address Alloca = CreateTempAlloca(BlockPointer->getType(),
// Set the DebugLocation to empty, so the store is recognized as a
// frame setup instruction by llvm::DwarfDebug::beginFunction().
auto NL = ApplyDebugLocation::CreateEmpty(*this);
Builder.CreateStore(BlockPointer, Alloca);
BlockPointerDbgLoc = Alloca.getPointer();
// If we have a C++ 'this' reference, go ahead and force it into
// existence now.
if (blockDecl->capturesCXXThis()) {
Address addr =
Builder.CreateStructGEP(LoadBlockStruct(), blockInfo.CXXThisIndex,
blockInfo.CXXThisOffset, "block.captured-this");
CXXThisValue = Builder.CreateLoad(addr, "this");
// Also force all the constant captures.
for (const auto &CI : blockDecl->captures()) {
const VarDecl *variable = CI.getVariable();
const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
if (!capture.isConstant()) continue;
CharUnits align = getContext().getDeclAlign(variable);
Address alloca =
CreateMemTemp(variable->getType(), align, "block.captured-const");
Builder.CreateStore(capture.getConstant(), alloca);
setAddrOfLocalVar(variable, alloca);
// Save a spot to insert the debug information for all the DeclRefExprs.
llvm::BasicBlock *entry = Builder.GetInsertBlock();
llvm::BasicBlock::iterator entry_ptr = Builder.GetInsertPoint();
if (IsLambdaConversionToBlock)
else {
PGO.assignRegionCounters(GlobalDecl(blockDecl), fn);
// Remember where we were...
llvm::BasicBlock *resume = Builder.GetInsertBlock();
// Go back to the entry.
Builder.SetInsertPoint(entry, entry_ptr);
// Emit debug information for all the DeclRefExprs.
// FIXME: also for 'this'
if (CGDebugInfo *DI = getDebugInfo()) {
for (const auto &CI : blockDecl->captures()) {
const VarDecl *variable = CI.getVariable();
DI->EmitLocation(Builder, variable->getLocation());
if (CGM.getCodeGenOpts().getDebugInfo() >=
codegenoptions::LimitedDebugInfo) {
const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
if (capture.isConstant()) {
auto addr = LocalDeclMap.find(variable)->second;
DI->EmitDeclareOfAutoVariable(variable, addr.getPointer(),
variable, BlockPointerDbgLoc, Builder, blockInfo,
entry_ptr == entry->end() ? nullptr : &*entry_ptr);
// Recover location if it was changed in the above loop.
// And resume where we left off.
if (resume == nullptr)
return fn;
namespace {
/// Represents a type of copy/destroy operation that should be performed for an
/// entity that's captured by a block.
enum class BlockCaptureEntityKind {
CXXRecord, // Copy or destroy
BlockObject, // Assign or release
/// Represents a captured entity that requires extra operations in order for
/// this entity to be copied or destroyed correctly.
struct BlockCaptureManagedEntity {
BlockCaptureEntityKind Kind;
BlockFieldFlags Flags;
const BlockDecl::Capture &CI;
const CGBlockInfo::Capture &Capture;
BlockCaptureManagedEntity(BlockCaptureEntityKind Type, BlockFieldFlags Flags,
const BlockDecl::Capture &CI,
const CGBlockInfo::Capture &Capture)
: Kind(Type), Flags(Flags), CI(CI), Capture(Capture) {}
} // end anonymous namespace
static std::pair<BlockCaptureEntityKind, BlockFieldFlags>
computeCopyInfoForBlockCapture(const BlockDecl::Capture &CI, QualType T,
const LangOptions &LangOpts) {
if (CI.getCopyExpr()) {
// don't bother computing flags
return std::make_pair(BlockCaptureEntityKind::CXXRecord, BlockFieldFlags());
BlockFieldFlags Flags;
if (CI.isByRef()) {
if (T.isObjCGCWeak())
return std::make_pair(BlockCaptureEntityKind::BlockObject, Flags);
if (!T->isObjCRetainableType())
// For all other types, the memcpy is fine.
return std::make_pair(BlockCaptureEntityKind::None, Flags);
bool isBlockPointer = T->isBlockPointerType();
if (isBlockPointer)
// Special rules for ARC captures:
Qualifiers QS = T.getQualifiers();
// We need to register __weak direct captures with the runtime.
if (QS.getObjCLifetime() == Qualifiers::OCL_Weak)
return std::make_pair(BlockCaptureEntityKind::ARCWeak, Flags);
// We need to retain the copied value for __strong direct captures.
if (QS.getObjCLifetime() == Qualifiers::OCL_Strong) {
// If it's a block pointer, we have to copy the block and
// assign that to the destination pointer, so we might as
// well use _Block_object_assign. Otherwise we can avoid that.
return std::make_pair(!isBlockPointer ? BlockCaptureEntityKind::ARCStrong
: BlockCaptureEntityKind::BlockObject,
// Non-ARC captures of retainable pointers are strong and
// therefore require a call to _Block_object_assign.
if (!QS.getObjCLifetime() && !LangOpts.ObjCAutoRefCount)
return std::make_pair(BlockCaptureEntityKind::BlockObject, Flags);
// Otherwise the memcpy is fine.
return std::make_pair(BlockCaptureEntityKind::None, Flags);
/// Find the set of block captures that need to be explicitly copied or destroy.
static void findBlockCapturedManagedEntities(
const CGBlockInfo &BlockInfo, const LangOptions &LangOpts,
SmallVectorImpl<BlockCaptureManagedEntity> &ManagedCaptures,
llvm::function_ref<std::pair<BlockCaptureEntityKind, BlockFieldFlags>(
const BlockDecl::Capture &, QualType, const LangOptions &)>
Predicate) {
for (const auto &CI : BlockInfo.getBlockDecl()->captures()) {
const VarDecl *Variable = CI.getVariable();
const CGBlockInfo::Capture &Capture = BlockInfo.getCapture(Variable);
if (Capture.isConstant())
auto Info = Predicate(CI, Variable->getType(), LangOpts);
if (Info.first != BlockCaptureEntityKind::None)
ManagedCaptures.emplace_back(Info.first, Info.second, CI, Capture);
/// Generate the copy-helper function for a block closure object:
/// static void block_copy_helper(block_t *dst, block_t *src);
/// The runtime will have previously initialized 'dst' by doing a
/// bit-copy of 'src'.
/// Note that this copies an entire block closure object to the heap;
/// it should not be confused with a 'byref copy helper', which moves
/// the contents of an individual __block variable to the heap.
llvm::Constant *
CodeGenFunction::GenerateCopyHelperFunction(const CGBlockInfo &blockInfo) {
ASTContext &C = getContext();
FunctionArgList args;
ImplicitParamDecl DstDecl(getContext(), C.VoidPtrTy,
ImplicitParamDecl SrcDecl(getContext(), C.VoidPtrTy,
const CGFunctionInfo &FI =
CGM.getTypes().arrangeBuiltinFunctionDeclaration(C.VoidTy, args);
// FIXME: it would be nice if these were mergeable with things with
// identical semantics.
llvm::FunctionType *LTy = CGM.getTypes().GetFunctionType(FI);
llvm::Function *Fn =
llvm::Function::Create(LTy, llvm::GlobalValue::InternalLinkage,
"__copy_helper_block_", &CGM.getModule());
IdentifierInfo *II
= &CGM.getContext().Idents.get("__copy_helper_block_");
FunctionDecl *FD = FunctionDecl::Create(C,
SourceLocation(), II, C.VoidTy,
nullptr, SC_Static,
CGM.SetInternalFunctionAttributes(nullptr, Fn, FI);
StartFunction(FD, C.VoidTy, Fn, FI, args);
ApplyDebugLocation NL{*this, blockInfo.getBlockExpr()->getLocStart()};
llvm::Type *structPtrTy = blockInfo.StructureType->getPointerTo();
Address src = GetAddrOfLocalVar(&SrcDecl);
src = Address(Builder.CreateLoad(src), blockInfo.BlockAlign);
src = Builder.CreateBitCast(src, structPtrTy, "block.source");
Address dst = GetAddrOfLocalVar(&DstDecl);
dst = Address(Builder.CreateLoad(dst), blockInfo.BlockAlign);
dst = Builder.CreateBitCast(dst, structPtrTy, "block.dest");
SmallVector<BlockCaptureManagedEntity, 4> CopiedCaptures;
findBlockCapturedManagedEntities(blockInfo, getLangOpts(), CopiedCaptures,
for (const auto &CopiedCapture : CopiedCaptures) {
const BlockDecl::Capture &CI = CopiedCapture.CI;
const CGBlockInfo::Capture &capture = CopiedCapture.Capture;
BlockFieldFlags flags = CopiedCapture.Flags;
unsigned index = capture.getIndex();
Address srcField = Builder.CreateStructGEP(src, index, capture.getOffset());
Address dstField = Builder.CreateStructGEP(dst, index, capture.getOffset());
// If there's an explicit copy expression, we do that.
if (CI.getCopyExpr()) {
assert(CopiedCapture.Kind == BlockCaptureEntityKind::CXXRecord);
EmitSynthesizedCXXCopyCtor(dstField, srcField, CI.getCopyExpr());
} else if (CopiedCapture.Kind == BlockCaptureEntityKind::ARCWeak) {
EmitARCCopyWeak(dstField, srcField);
} else {
llvm::Value *srcValue = Builder.CreateLoad(srcField, "blockcopy.src");
if (CopiedCapture.Kind == BlockCaptureEntityKind::ARCStrong) {
// At -O0, store null into the destination field (so that the
// storeStrong doesn't over-release) and then call storeStrong.
// This is a workaround to not having an initStrong call.
if (CGM.getCodeGenOpts().OptimizationLevel == 0) {
auto *ty = cast<llvm::PointerType>(srcValue->getType());
llvm::Value *null = llvm::ConstantPointerNull::get(ty);
Builder.CreateStore(null, dstField);
EmitARCStoreStrongCall(dstField, srcValue, true);
// With optimization enabled, take advantage of the fact that
// the blocks runtime guarantees a memcpy of the block data, and
// just emit a retain of the src field.
} else {
// We don't need this anymore, so kill it. It's not quite
// worth the annoyance to avoid creating it in the first place.
} else {
assert(CopiedCapture.Kind == BlockCaptureEntityKind::BlockObject);
srcValue = Builder.CreateBitCast(srcValue, VoidPtrTy);
llvm::Value *dstAddr =
Builder.CreateBitCast(dstField.getPointer(), VoidPtrTy);
llvm::Value *args[] = {
dstAddr, srcValue, llvm::ConstantInt::get(Int32Ty, flags.getBitMask())
const VarDecl *variable = CI.getVariable();
bool copyCanThrow = false;
if (CI.isByRef() && variable->getType()->getAsCXXRecordDecl()) {
const Expr *copyExpr =
if (copyExpr) {
copyCanThrow = true; // FIXME: reuse the noexcept logic
if (copyCanThrow) {
EmitRuntimeCallOrInvoke(CGM.getBlockObjectAssign(), args);
} else {
EmitNounwindRuntimeCall(CGM.getBlockObjectAssign(), args);
return llvm::ConstantExpr::getBitCast(Fn, VoidPtrTy);
static std::pair<BlockCaptureEntityKind, BlockFieldFlags>
computeDestroyInfoForBlockCapture(const BlockDecl::Capture &CI, QualType T,
const LangOptions &LangOpts) {
BlockFieldFlags Flags;
if (CI.isByRef()) {
if (T.isObjCGCWeak())
return std::make_pair(BlockCaptureEntityKind::BlockObject, Flags);
if (const CXXRecordDecl *Record = T->getAsCXXRecordDecl()) {
if (Record->hasTrivialDestructor())
return std::make_pair(BlockCaptureEntityKind::None, BlockFieldFlags());
return std::make_pair(BlockCaptureEntityKind::CXXRecord, BlockFieldFlags());
// Other types don't need to be destroy explicitly.
if (!T->isObjCRetainableType())
return std::make_pair(BlockCaptureEntityKind::None, Flags);
if (T->isBlockPointerType())
// Special rules for ARC captures.
Qualifiers QS = T.getQualifiers();
// Use objc_storeStrong for __strong direct captures; the
// dynamic tools really like it when we do this.
if (QS.getObjCLifetime() == Qualifiers::OCL_Strong)
return std::make_pair(BlockCaptureEntityKind::ARCStrong, Flags);
// Support __weak direct captures.
if (QS.getObjCLifetime() == Qualifiers::OCL_Weak)
return std::make_pair(BlockCaptureEntityKind::ARCWeak, Flags);
// Non-ARC captures are strong, and we need to use
// _Block_object_dispose.
if (!QS.hasObjCLifetime() && !LangOpts.ObjCAutoRefCount)
return std::make_pair(BlockCaptureEntityKind::BlockObject, Flags);
// Otherwise, we have nothing to do.
return std::make_pair(BlockCaptureEntityKind::None, Flags);
/// Generate the destroy-helper function for a block closure object:
/// static void block_destroy_helper(block_t *theBlock);
/// Note that this destroys a heap-allocated block closure object;
/// it should not be confused with a 'byref destroy helper', which
/// destroys the heap-allocated contents of an individual __block
/// variable.
llvm::Constant *
CodeGenFunction::GenerateDestroyHelperFunction(const CGBlockInfo &blockInfo) {
ASTContext &C = getContext();
FunctionArgList args;
ImplicitParamDecl SrcDecl(getContext(), C.VoidPtrTy,
const CGFunctionInfo &FI =
CGM.getTypes().arrangeBuiltinFunctionDeclaration(C.VoidTy, args);
// FIXME: We'd like to put these into a mergable by content, with
// internal linkage.
llvm::FunctionType *LTy = CGM.getTypes().GetFunctionType(FI);
llvm::Function *Fn =
llvm::Function::Create(LTy, llvm::GlobalValue::InternalLinkage,
"__destroy_helper_block_", &CGM.getModule());
IdentifierInfo *II
= &CGM.getContext().Idents.get("__destroy_helper_block_");
FunctionDecl *FD = FunctionDecl::Create(C, C.getTranslationUnitDecl(),
SourceLocation(), II, C.VoidTy,
nullptr, SC_Static,
false, false);
CGM.SetInternalFunctionAttributes(nullptr, Fn, FI);
StartFunction(FD, C.VoidTy, Fn, FI, args);
ApplyDebugLocation NL{*this, blockInfo.getBlockExpr()->getLocStart()};
llvm::Type *structPtrTy = blockInfo.StructureType->getPointerTo();
Address src = GetAddrOfLocalVar(&SrcDecl);
src = Address(Builder.CreateLoad(src), blockInfo.BlockAlign);
src = Builder.CreateBitCast(src, structPtrTy, "block");
CodeGenFunction::RunCleanupsScope cleanups(*this);
SmallVector<BlockCaptureManagedEntity, 4> DestroyedCaptures;
findBlockCapturedManagedEntities(blockInfo, getLangOpts(), DestroyedCaptures,
for (const auto &DestroyedCapture : DestroyedCaptures) {
const BlockDecl::Capture &CI = DestroyedCapture.CI;
const CGBlockInfo::Capture &capture = DestroyedCapture.Capture;
BlockFieldFlags flags = DestroyedCapture.Flags;
Address srcField =
Builder.CreateStructGEP(src, capture.getIndex(), capture.getOffset());
// If the captured record has a destructor then call it.
if (DestroyedCapture.Kind == BlockCaptureEntityKind::CXXRecord) {
const auto *Dtor =
PushDestructorCleanup(Dtor, srcField);
// If this is a __weak capture, emit the release directly.
} else if (DestroyedCapture.Kind == BlockCaptureEntityKind::ARCWeak) {
// Destroy strong objects with a call if requested.
} else if (DestroyedCapture.Kind == BlockCaptureEntityKind::ARCStrong) {
EmitARCDestroyStrong(srcField, ARCImpreciseLifetime);
// Otherwise we call _Block_object_dispose. It wouldn't be too
// hard to just emit this as a cleanup if we wanted to make sure
// that things were done in reverse.
} else {
assert(DestroyedCapture.Kind == BlockCaptureEntityKind::BlockObject);
llvm::Value *value = Builder.CreateLoad(srcField);
value = Builder.CreateBitCast(value, VoidPtrTy);
BuildBlockRelease(value, flags);
return llvm::ConstantExpr::getBitCast(Fn, VoidPtrTy);
namespace {
/// Emits the copy/dispose helper functions for a __block object of id type.
class ObjectByrefHelpers final : public BlockByrefHelpers {
BlockFieldFlags Flags;
ObjectByrefHelpers(CharUnits alignment, BlockFieldFlags flags)
: BlockByrefHelpers(alignment), Flags(flags) {}
void emitCopy(CodeGenFunction &CGF, Address destField,
Address srcField) override {
destField = CGF.Builder.CreateBitCast(destField, CGF.VoidPtrTy);
srcField = CGF.Builder.CreateBitCast(srcField, CGF.VoidPtrPtrTy);
llvm::Value *srcValue = CGF.Builder.CreateLoad(srcField);
unsigned flags = (Flags | BLOCK_BYREF_CALLER).getBitMask();
llvm::Value *flagsVal = llvm::ConstantInt::get(CGF.Int32Ty, flags);
llvm::Value *fn = CGF.CGM.getBlockObjectAssign();
llvm::Value *args[] = { destField.getPointer(), srcValue, flagsVal };
CGF.EmitNounwindRuntimeCall(fn, args);
void emitDispose(CodeGenFunction &CGF, Address field) override {
field = CGF.Builder.CreateBitCast(field, CGF.Int8PtrTy->getPointerTo(0));
llvm::Value *value = CGF.Builder.CreateLoad(field);
CGF.BuildBlockRelease(value, Flags | BLOCK_BYREF_CALLER);
void profileImpl(llvm::FoldingSetNodeID &id) const override {
/// Emits the copy/dispose helpers for an ARC __block __weak variable.
class ARCWeakByrefHelpers final : public BlockByrefHelpers {
ARCWeakByrefHelpers(CharUnits alignment) : BlockByrefHelpers(alignment) {}
void emitCopy(CodeGenFunction &CGF, Address destField,
Address srcField) override {
CGF.EmitARCMoveWeak(destField, srcField);
void emitDispose(CodeGenFunction &CGF, Address field) override {
void profileImpl(llvm::FoldingSetNodeID &id) const override {
// 0 is distinguishable from all pointers and byref flags
/// Emits the copy/dispose helpers for an ARC __block __strong variable
/// that's not of block-pointer type.
class ARCStrongByrefHelpers final : public BlockByrefHelpers {
ARCStrongByrefHelpers(CharUnits alignment) : BlockByrefHelpers(alignment) {}
void emitCopy(CodeGenFunction &CGF, Address destField,
Address srcField) override {
// Do a "move" by copying the value and then zeroing out the old
// variable.
llvm::Value *value = CGF.Builder.CreateLoad(srcField);
llvm::Value *null =
if (CGF.CGM.getCodeGenOpts().OptimizationLevel == 0) {
CGF.Builder.CreateStore(null, destField);
CGF.EmitARCStoreStrongCall(destField, value, /*ignored*/ true);
CGF.EmitARCStoreStrongCall(srcField, null, /*ignored*/ true);
CGF.Builder.CreateStore(value, destField);
CGF.Builder.CreateStore(null, srcField);
void emitDispose(CodeGenFunction &CGF, Address field) override {
CGF.EmitARCDestroyStrong(field, ARCImpreciseLifetime);
void profileImpl(llvm::FoldingSetNodeID &id) const override {
// 1 is distinguishable from all pointers and byref flags
/// Emits the copy/dispose helpers for an ARC __block __strong
/// variable that's of block-pointer type.
class ARCStrongBlockByrefHelpers final : public BlockByrefHelpers {
ARCStrongBlockByrefHelpers(CharUnits alignment)
: BlockByrefHelpers(alignment) {}
void emitCopy(CodeGenFunction &CGF, Address destField,
Address srcField) override {
// Do the copy with objc_retainBlock; that's all that
// _Block_object_assign would do anyway, and we'd have to pass the
// right arguments to make sure it doesn't get no-op'ed.
llvm::Value *oldValue = CGF.Builder.CreateLoad(srcField);
llvm::Value *copy = CGF.EmitARCRetainBlock(oldValue, /*mandatory*/ true);
CGF.Builder.CreateStore(copy, destField);
void emitDispose(CodeGenFunction &CGF, Address field) override {
CGF.EmitARCDestroyStrong(field, ARCImpreciseLifetime);
void profileImpl(llvm::FoldingSetNodeID &id) const override {
// 2 is distinguishable from all pointers and byref flags
/// Emits the copy/dispose helpers for a __block variable with a
/// nontrivial copy constructor or destructor.
class CXXByrefHelpers final : public BlockByrefHelpers {
QualType VarType;
const Expr *CopyExpr;
CXXByrefHelpers(CharUnits alignment, QualType type,
const Expr *copyExpr)
: BlockByrefHelpers(alignment), VarType(type), CopyExpr(copyExpr) {}
bool needsCopy() const override { return CopyExpr != nullptr; }
void emitCopy(CodeGenFunction &CGF, Address destField,
Address srcField) override {
if (!CopyExpr) return;
CGF.EmitSynthesizedCXXCopyCtor(destField, srcField, CopyExpr);
void emitDispose(CodeGenFunction &CGF, Address field) override {
EHScopeStack::stable_iterator cleanupDepth = CGF.EHStack.stable_begin();
CGF.PushDestructorCleanup(VarType, field);
void profileImpl(llvm::FoldingSetNodeID &id) const override {
} // end anonymous namespace
static llvm::Constant *
generateByrefCopyHelper(CodeGenFunction &CGF, const BlockByrefInfo &byrefInfo,
BlockByrefHelpers &generator) {
ASTContext &Context = CGF.getContext();
QualType R = Context.VoidTy;
FunctionArgList args;
ImplicitParamDecl Dst(CGF.getContext(), Context.VoidPtrTy,
ImplicitParamDecl Src(CGF.getContext(), Context.VoidPtrTy,
const CGFunctionInfo &FI =
CGF.CGM.getTypes().arrangeBuiltinFunctionDeclaration(R, args);
llvm::FunctionType *LTy = CGF.CGM.getTypes().GetFunctionType(FI);
// FIXME: We'd like to put these into a mergable by content, with
// internal linkage.
llvm::Function *Fn =
llvm::Function::Create(LTy, llvm::GlobalValue::InternalLinkage,
"__Block_byref_object_copy_", &CGF.CGM.getModule());
IdentifierInfo *II
= &Context.Idents.get("__Block_byref_object_copy_");
FunctionDecl *FD = FunctionDecl::Create(Context,
SourceLocation(), II, R, nullptr,
false, false);
CGF.CGM.SetInternalFunctionAttributes(nullptr, Fn, FI);
CGF.StartFunction(FD, R, Fn, FI, args);
if (generator.needsCopy()) {
llvm::Type *byrefPtrType = byrefInfo.Type->getPointerTo(0);
// dst->x
Address destField = CGF.GetAddrOfLocalVar(&Dst);
destField = Address(CGF.Builder.CreateLoad(destField),
destField = CGF.Builder.CreateBitCast(destField, byrefPtrType);
destField = CGF.emitBlockByrefAddress(destField, byrefInfo, false,
// src->x
Address srcField = CGF.GetAddrOfLocalVar(&Src);
srcField = Address(CGF.Builder.CreateLoad(srcField),
srcField = CGF.Builder.CreateBitCast(srcField, byrefPtrType);
srcField = CGF.emitBlockByrefAddress(srcField, byrefInfo, false,
generator.emitCopy(CGF, destField, srcField);
return llvm::ConstantExpr::getBitCast(Fn, CGF.Int8PtrTy);
/// Build the copy helper for a __block variable.
static llvm::Constant *buildByrefCopyHelper(CodeGenModule &CGM,
const BlockByrefInfo &byrefInfo,
BlockByrefHelpers &generator) {
CodeGenFunction CGF(CGM);
return generateByrefCopyHelper(CGF, byrefInfo, generator);
/// Generate code for a __block variable's dispose helper.
static llvm::Constant *
generateByrefDisposeHelper(CodeGenFunction &CGF,
const BlockByrefInfo &byrefInfo,
BlockByrefHelpers &generator) {
ASTContext &Context = CGF.getContext();
QualType R = Context.VoidTy;
FunctionArgList args;
ImplicitParamDecl Src(CGF.getContext(), Context.VoidPtrTy,
const CGFunctionInfo &FI =
CGF.CGM.getTypes().arrangeBuiltinFunctionDeclaration(R, args);
llvm::FunctionType *LTy = CGF.CGM.getTypes().GetFunctionType(FI);
// FIXME: We'd like to put these into a mergable by content, with
// internal linkage.
llvm::Function *Fn =
llvm::Function::Create(LTy, llvm::GlobalValue::InternalLinkage,
IdentifierInfo *II
= &Context.Idents.get("__Block_byref_object_dispose_");
FunctionDecl *FD = FunctionDecl::Create(Context,
SourceLocation(), II, R, nullptr,
false, false);
CGF.CGM.SetInternalFunctionAttributes(nullptr, Fn, FI);
CGF.StartFunction(FD, R, Fn, FI, args);
if (generator.needsDispose()) {
Address addr = CGF.GetAddrOfLocalVar(&Src);
addr = Address(CGF.Builder.CreateLoad(addr), byrefInfo.ByrefAlignment);
auto byrefPtrType = byrefInfo.Type->getPointerTo(0);
addr = CGF.Builder.CreateBitCast(addr, byrefPtrType);
addr = CGF.emitBlockByrefAddress(addr, byrefInfo, false, "object");
generator.emitDispose(CGF, addr);
return llvm::ConstantExpr::getBitCast(Fn, CGF.Int8PtrTy);
/// Build the dispose helper for a __block variable.
static llvm::Constant *buildByrefDisposeHelper(CodeGenModule &CGM,
const BlockByrefInfo &byrefInfo,
BlockByrefHelpers &generator) {
CodeGenFunction CGF(CGM);
return generateByrefDisposeHelper(CGF, byrefInfo, generator);
/// Lazily build the copy and dispose helpers for a __block variable
/// with the given information.
template <class T>
static T *buildByrefHelpers(CodeGenModule &CGM, const BlockByrefInfo &byrefInfo,
T &&generator) {
llvm::FoldingSetNodeID id;
void *insertPos;
BlockByrefHelpers *node
= CGM.ByrefHelpersCache.FindNodeOrInsertPos(id, insertPos);
if (node) return static_cast<T*>(node);
generator.CopyHelper = buildByrefCopyHelper(CGM, byrefInfo, generator);
generator.DisposeHelper = buildByrefDisposeHelper(CGM, byrefInfo, generator);
T *copy = new (CGM.getContext()) T(std::forward<T>(generator));
CGM.ByrefHelpersCache.InsertNode(copy, insertPos);
return copy;
/// Build the copy and dispose helpers for the given __block variable
/// emission. Places the helpers in the global cache. Returns null
/// if no helpers are required.
BlockByrefHelpers *
CodeGenFunction::buildByrefHelpers(llvm::StructType &byrefType,
const AutoVarEmission &emission) {
const VarDecl &var = *emission.Variable;
QualType type = var.getType();
auto &byrefInfo = getBlockByrefInfo(&var);
// The alignment we care about for the purposes of uniquing byref
// helpers is the alignment of the actual byref value field.
CharUnits valueAlignment =
if (const CXXRecordDecl *record = type->getAsCXXRecordDecl()) {
const Expr *copyExpr = CGM.getContext().getBlockVarCopyInits(&var);
if (!copyExpr && record->hasTrivialDestructor()) return nullptr;
return ::buildByrefHelpers(
CGM, byrefInfo, CXXByrefHelpers(valueAlignment, type, copyExpr));
// Otherwise, if we don't have a retainable type, there's nothing to do.
// that the runtime does extra copies.
if (!type->isObjCRetainableType()) return nullptr;
Qualifiers qs = type.getQualifiers();
// If we have lifetime, that dominates.
if (Qualifiers::ObjCLifetime lifetime = qs.getObjCLifetime()) {
switch (lifetime) {
case Qualifiers::OCL_None: llvm_unreachable("impossible");
// These are just bits as far as the runtime is concerned.
case Qualifiers::OCL_ExplicitNone:
case Qualifiers::OCL_Autoreleasing:
return nullptr;
// Tell the runtime that this is ARC __weak, called by the
// byref routines.
case Qualifiers::OCL_Weak:
return ::buildByrefHelpers(CGM, byrefInfo,
// ARC __strong __block variables need to be retained.
case Qualifiers::OCL_Strong:
// Block pointers need to be copied, and there's no direct
// transfer possible.
if (type->isBlockPointerType()) {
return ::buildByrefHelpers(CGM, byrefInfo,
// Otherwise, we transfer ownership of the retain from the stack
// to the heap.
} else {
return ::buildByrefHelpers(CGM, byrefInfo,
llvm_unreachable("fell out of lifetime switch!");
BlockFieldFlags flags;
if (type->isBlockPointerType()) {
} else if (CGM.getContext().isObjCNSObjectType(type) ||
type->isObjCObjectPointerType()) {
} else {
return nullptr;
if (type.isObjCGCWeak())
return ::buildByrefHelpers(CGM, byrefInfo,
ObjectByrefHelpers(valueAlignment, flags));
Address CodeGenFunction::emitBlockByrefAddress(Address baseAddr,
const VarDecl *var,
bool followForward) {
auto &info = getBlockByrefInfo(var);
return emitBlockByrefAddress(baseAddr, info, followForward, var->getName());
Address CodeGenFunction::emitBlockByrefAddress(Address baseAddr,
const BlockByrefInfo &info,
bool followForward,
const llvm::Twine &name) {
// Chase the forwarding address if requested.
if (followForward) {
Address forwardingAddr =
Builder.CreateStructGEP(baseAddr, 1, getPointerSize(), "forwarding");
baseAddr = Address(Builder.CreateLoad(forwardingAddr), info.ByrefAlignment);
return Builder.CreateStructGEP(baseAddr, info.FieldIndex,
info.FieldOffset, name);
/// BuildByrefInfo - This routine changes a __block variable declared as T x
/// into:
/// struct {
/// void *__isa;
/// void *__forwarding;
/// int32_t __flags;
/// int32_t __size;
/// void *__copy_helper; // only if needed
/// void *__destroy_helper; // only if needed
/// void *__byref_variable_layout;// only if needed
/// char padding[X]; // only if needed
/// T x;
/// } x
const BlockByrefInfo &CodeGenFunction::getBlockByrefInfo(const VarDecl *D) {
auto it = BlockByrefInfos.find(D);
if (it != BlockByrefInfos.end())
return it->second;
llvm::StructType *byrefType =
"struct.__block_byref_" + D->getNameAsString());
QualType Ty = D->getType();
CharUnits size;
SmallVector<llvm::Type *, 8> types;
// void *__isa;
size += getPointerSize();
// void *__forwarding;
size += getPointerSize();
// int32_t __flags;
size += CharUnits::fromQuantity(4);
// int32_t __size;
size += CharUnits::fromQuantity(4);
// Note that this must match *exactly* the logic in buildByrefHelpers.
bool hasCopyAndDispose = getContext().BlockRequiresCopying(Ty, D);
if (hasCopyAndDispose) {
/// void *__copy_helper;
size += getPointerSize();
/// void *__destroy_helper;
size += getPointerSize();
bool HasByrefExtendedLayout = false;
Qualifiers::ObjCLifetime Lifetime;
if (getContext().getByrefLifetime(Ty, Lifetime, HasByrefExtendedLayout) &&
HasByrefExtendedLayout) {
/// void *__byref_variable_layout;
size += CharUnits::fromQuantity(PointerSizeInBytes);
// T x;
llvm::Type *varTy = ConvertTypeForMem(Ty);
bool packed = false;
CharUnits varAlign = getContext().getDeclAlign(D);
CharUnits varOffset = size.alignTo(varAlign);
// We may have to insert padding.
if (varOffset != size) {
llvm::Type *paddingTy =
llvm::ArrayType::get(Int8Ty, (varOffset - size).getQuantity());
size = varOffset;
// Conversely, we might have to prevent LLVM from inserting padding.
} else if (CGM.getDataLayout().getABITypeAlignment(varTy)
> varAlign.getQuantity()) {
packed = true;
byrefType->setBody(types, packed);
BlockByrefInfo info;
info.Type = byrefType;
info.FieldIndex = types.size() - 1;
info.FieldOffset = varOffset;
info.ByrefAlignment = std::max(varAlign, getPointerAlign());
auto pair = BlockByrefInfos.insert({D, info});
assert(pair.second && "info was inserted recursively?");
return pair.first->second;
/// Initialize the structural components of a __block variable, i.e.
/// everything but the actual object.
void CodeGenFunction::emitByrefStructureInit(const AutoVarEmission &emission) {
// Find the address of the local.
Address addr = emission.Addr;
// That's an alloca of the byref structure type.
llvm::StructType *byrefType = cast<llvm::StructType>(
unsigned nextHeaderIndex = 0;
CharUnits nextHeaderOffset;
auto storeHeaderField = [&](llvm::Value *value, CharUnits fieldSize,
const Twine &name) {
auto fieldAddr = Builder.CreateStructGEP(addr, nextHeaderIndex,
nextHeaderOffset, name);
Builder.CreateStore(value, fieldAddr);
nextHeaderOffset += fieldSize;
// Build the byref helpers if necessary. This is null if we don't need any.
BlockByrefHelpers *helpers = buildByrefHelpers(*byrefType, emission);
const VarDecl &D = *emission.Variable;
QualType type = D.getType();
bool HasByrefExtendedLayout;
Qualifiers::ObjCLifetime ByrefLifetime;
bool ByRefHasLifetime =
getContext().getByrefLifetime(type, ByrefLifetime, HasByrefExtendedLayout);
llvm::Value *V;
// Initialize the 'isa', which is just 0 or 1.
int isa = 0;
if (type.isObjCGCWeak())
isa = 1;
V = Builder.CreateIntToPtr(Builder.getInt32(isa), Int8PtrTy, "isa");
storeHeaderField(V, getPointerSize(), "byref.isa");
// Store the address of the variable into its own forwarding pointer.
storeHeaderField(addr.getPointer(), getPointerSize(), "byref.forwarding");
// Blocks ABI:
// c) the flags field is set to either 0 if no helper functions are
// needed or BLOCK_BYREF_HAS_COPY_DISPOSE if they are,
BlockFlags flags;
if (helpers) flags |= BLOCK_BYREF_HAS_COPY_DISPOSE;
if (ByRefHasLifetime) {
if (HasByrefExtendedLayout) flags |= BLOCK_BYREF_LAYOUT_EXTENDED;
else switch (ByrefLifetime) {
case Qualifiers::OCL_Strong:
case Qualifiers::OCL_Weak:
case Qualifiers::OCL_ExplicitNone:
case Qualifiers::OCL_None:
if (!type->isObjCObjectPointerType() && !type->isBlockPointerType())
if (CGM.getLangOpts().ObjCGCBitmapPrint) {
printf("\n Inline flag for BYREF variable layout (%d):", flags.getBitMask());
BlockFlags ThisFlag(flags.getBitMask() & BLOCK_BYREF_LAYOUT_MASK);
storeHeaderField(llvm::ConstantInt::get(IntTy, flags.getBitMask()),
getIntSize(), "byref.flags");
CharUnits byrefSize = CGM.GetTargetTypeStoreSize(byrefType);
V = llvm::ConstantInt::get(IntTy, byrefSize.getQuantity());
storeHeaderField(V, getIntSize(), "byref.size");
if (helpers) {
storeHeaderField(helpers->CopyHelper, getPointerSize(),
storeHeaderField(helpers->DisposeHelper, getPointerSize(),
if (ByRefHasLifetime && HasByrefExtendedLayout) {
auto layoutInfo = CGM.getObjCRuntime().BuildByrefLayout(CGM, type);
storeHeaderField(layoutInfo, getPointerSize(), "byref.layout");
void CodeGenFunction::BuildBlockRelease(llvm::Value *V, BlockFieldFlags flags) {
llvm::Value *F = CGM.getBlockObjectDispose();
llvm::Value *args[] = {
Builder.CreateBitCast(V, Int8PtrTy),
llvm::ConstantInt::get(Int32Ty, flags.getBitMask())
EmitNounwindRuntimeCall(F, args); // FIXME: throwing destructors?
namespace {
/// Release a __block variable.
struct CallBlockRelease final : EHScopeStack::Cleanup {
llvm::Value *Addr;
CallBlockRelease(llvm::Value *Addr) : Addr(Addr) {}
void Emit(CodeGenFunction &CGF, Flags flags) override {
// Should we be passing FIELD_IS_WEAK here?
CGF.BuildBlockRelease(Addr, BLOCK_FIELD_IS_BYREF);
} // end anonymous namespace
/// Enter a cleanup to destroy a __block variable. Note that this
/// cleanup should be a no-op if the variable hasn't left the stack
/// yet; if a cleanup is required for the variable itself, that needs
/// to be done externally.
void CodeGenFunction::enterByrefCleanup(const AutoVarEmission &emission) {
// We don't enter this cleanup if we're in pure-GC mode.
if (CGM.getLangOpts().getGC() == LangOptions::GCOnly)
/// Adjust the declaration of something from the blocks API.
static void configureBlocksRuntimeObject(CodeGenModule &CGM,
llvm::Constant *C) {
auto *GV = cast<llvm::GlobalValue>(C->stripPointerCasts());
if (CGM.getTarget().getTriple().isOSBinFormatCOFF()) {
IdentifierInfo &II = CGM.getContext().Idents.get(C->getName());
TranslationUnitDecl *TUDecl = CGM.getContext().getTranslationUnitDecl();
DeclContext *DC = TranslationUnitDecl::castToDeclContext(TUDecl);
assert((isa<llvm::Function>(C->stripPointerCasts()) ||
isa<llvm::GlobalVariable>(C->stripPointerCasts())) &&
"expected Function or GlobalVariable");
const NamedDecl *ND = nullptr;
for (const auto &Result : DC->lookup(&II))
if ((ND = dyn_cast<FunctionDecl>(Result)) ||
(ND = dyn_cast<VarDecl>(Result)))
// TODO: support static blocks runtime
if (GV->isDeclaration() && (!ND || !ND->hasAttr<DLLExportAttr>())) {
} else {
if (!CGM.getLangOpts().BlocksRuntimeOptional)
if (GV->isDeclaration() && GV->hasExternalLinkage())
llvm::Constant *CodeGenModule::getBlockObjectDispose() {
if (BlockObjectDispose)
return BlockObjectDispose;
llvm::Type *args[] = { Int8PtrTy, Int32Ty };
llvm::FunctionType *fty
= llvm::FunctionType::get(VoidTy, args, false);
BlockObjectDispose = CreateRuntimeFunction(fty, "_Block_object_dispose");
configureBlocksRuntimeObject(*this, BlockObjectDispose);
return BlockObjectDispose;
llvm::Constant *CodeGenModule::getBlockObjectAssign() {
if (BlockObjectAssign)
return BlockObjectAssign;
llvm::Type *args[] = { Int8PtrTy, Int8PtrTy, Int32Ty };
llvm::FunctionType *fty
= llvm::FunctionType::get(VoidTy, args, false);
BlockObjectAssign = CreateRuntimeFunction(fty, "_Block_object_assign");
configureBlocksRuntimeObject(*this, BlockObjectAssign);
return BlockObjectAssign;
llvm::Constant *CodeGenModule::getNSConcreteGlobalBlock() {
if (NSConcreteGlobalBlock)
return NSConcreteGlobalBlock;
NSConcreteGlobalBlock = GetOrCreateLLVMGlobal("_NSConcreteGlobalBlock",
configureBlocksRuntimeObject(*this, NSConcreteGlobalBlock);
return NSConcreteGlobalBlock;
llvm::Constant *CodeGenModule::getNSConcreteStackBlock() {
if (NSConcreteStackBlock)
return NSConcreteStackBlock;
NSConcreteStackBlock = GetOrCreateLLVMGlobal("_NSConcreteStackBlock",
configureBlocksRuntimeObject(*this, NSConcreteStackBlock);
return NSConcreteStackBlock;