Add the clang library to the repo (with some of my changes, too).

1 files changed, 2044 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGBlocks.cpp b/clang/lib/CodeGen/CGBlocks.cpp
new file mode 100644
index 0000000..f8c7bcd
--- /dev/null
+++ b/clang/lib/CodeGen/CGBlocks.cpp
@@ -0,0 +1,2044 @@
+//===--- CGBlocks.cpp - Emit LLVM Code for 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 to emit blocks.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CGDebugInfo.h"
+#include "CodeGenFunction.h"
+#include "CGObjCRuntime.h"
+#include "CodeGenModule.h"
+#include "CGBlocks.h"
+#include "clang/AST/DeclObjC.h"
+#include "llvm/Module.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/Target/TargetData.h"
+#include <algorithm>
+
+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), StructureType(0), Block(block),
+    DominatingIP(0) {
+    
+  // 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.
+CodeGenModule::ByrefHelpers::~ByrefHelpers() {}
+
+/// 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 dipose of a block.
+static llvm::Constant *buildDisposeHelper(CodeGenModule &CGM,
+                                          const CGBlockInfo &blockInfo) {
+  return CodeGenFunction(CGM).GenerateDestroyHelperFunction(blockInfo);
+}
+
+/// Build the block descriptor constant for a block.
+static llvm::Constant *buildBlockDescriptor(CodeGenModule &CGM,
+                                            const CGBlockInfo &blockInfo) {
+  ASTContext &C = CGM.getContext();
+
+  llvm::Type *ulong = CGM.getTypes().ConvertType(C.UnsignedLongTy);
+  llvm::Type *i8p = CGM.getTypes().ConvertType(C.VoidPtrTy);
+
+  SmallVector<llvm::Constant*, 6> elements;
+
+  // reserved
+  elements.push_back(llvm::ConstantInt::get(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.push_back(llvm::ConstantInt::get(ulong,
+                                            blockInfo.BlockSize.getQuantity()));
+
+  // Optional copy/dispose helpers.
+  if (blockInfo.NeedsCopyDispose) {
+    // copy_func_helper_decl
+    elements.push_back(buildCopyHelper(CGM, blockInfo));
+
+    // destroy_func_decl
+    elements.push_back(buildDisposeHelper(CGM, blockInfo));
+  }
+
+  // Signature.  Mandatory ObjC-style method descriptor @encode sequence.
+  std::string typeAtEncoding =
+    CGM.getContext().getObjCEncodingForBlock(blockInfo.getBlockExpr());
+  elements.push_back(llvm::ConstantExpr::getBitCast(
+                          CGM.GetAddrOfConstantCString(typeAtEncoding), i8p));
+  
+  // GC layout.
+  if (C.getLangOpts().ObjC1)
+    elements.push_back(CGM.getObjCRuntime().BuildGCBlockLayout(CGM, blockInfo));
+  else
+    elements.push_back(llvm::Constant::getNullValue(i8p));
+
+  llvm::Constant *init = llvm::ConstantStruct::getAnon(elements);
+
+  llvm::GlobalVariable *global =
+    new llvm::GlobalVariable(CGM.getModule(), init->getType(), true,
+                             llvm::GlobalValue::InternalLinkage,
+                             init, "__block_descriptor_tmp");
+
+  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...;
+  };
+ */
+
+/// The number of fields in a block header.
+const unsigned BlockHeaderSize = 5;
+
+namespace {
+  /// A chunk of data that we actually have to capture in the block.
+  struct BlockLayoutChunk {
+    CharUnits Alignment;
+    CharUnits Size;
+    const BlockDecl::Capture *Capture; // null for 'this'
+    llvm::Type *Type;
+
+    BlockLayoutChunk(CharUnits align, CharUnits size,
+                     const BlockDecl::Capture *capture,
+                     llvm::Type *type)
+      : Alignment(align), Size(size), Capture(capture), Type(type) {}
+
+    /// Tell the block info that this chunk has the given field index.
+    void setIndex(CGBlockInfo &info, unsigned index) {
+      if (!Capture)
+        info.CXXThisIndex = index;
+      else
+        info.Captures[Capture->getVariable()]
+          = CGBlockInfo::Capture::makeIndex(index);
+    }
+  };
+
+  /// Order by descending alignment.
+  bool operator<(const BlockLayoutChunk &left, const BlockLayoutChunk &right) {
+    return left.Alignment > right.Alignment;
+  }
+}
+
+/// Determines if the given type is safe for constant capture in C++.
+static bool isSafeForCXXConstantCapture(QualType type) {
+  const RecordType *recordType =
+    type->getBaseElementTypeUnsafe()->getAs<RecordType>();
+
+  // Only records can be unsafe.
+  if (!recordType) return true;
+
+  const CXXRecordDecl *record = cast<CXXRecordDecl>(recordType->getDecl());
+
+  // Maintain semantics for classes with non-trivial dtors or copy ctors.
+  if (!record->hasTrivialDestructor()) return false;
+  if (!record->hasTrivialCopyConstructor()) 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) {
+  QualType type = var->getType();
+
+  // We can only do this if the variable is const.
+  if (!type.isConstQualified()) return 0;
+
+  // Furthermore, in C++ we have to worry about mutable fields:
+  // C++ [dcl.type.cv]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 0;
+
+  // 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 0;
+
+  return CGM.EmitConstantInit(*var, CGF);
+}
+
+/// 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) {
+  ASTContext &C = CGM.getContext();
+
+  // The header is basically a 'struct { void *; int; int; void *; void *; }'.
+  CharUnits ptrSize, ptrAlign, intSize, intAlign;
+  llvm::tie(ptrSize, ptrAlign) = C.getTypeInfoInChars(C.VoidPtrTy);
+  llvm::tie(intSize, intAlign) = C.getTypeInfoInChars(C.IntTy);
+
+  // Are there crazy embedded platforms where this isn't true?
+  assert(intSize <= ptrSize && "layout assumptions horribly violated");
+
+  CharUnits headerSize = ptrSize;
+  if (2 * intSize < ptrAlign) headerSize += ptrSize;
+  else headerSize += 2 * intSize;
+  headerSize += 2 * ptrSize;
+
+  info.BlockAlign = ptrAlign;
+  info.BlockSize = headerSize;
+
+  assert(elementTypes.empty());
+  llvm::Type *i8p = CGM.getTypes().ConvertType(C.VoidPtrTy);
+  llvm::Type *intTy = CGM.getTypes().ConvertType(C.IntTy);
+  elementTypes.push_back(i8p);
+  elementTypes.push_back(intTy);
+  elementTypes.push_back(intTy);
+  elementTypes.push_back(i8p);
+  elementTypes.push_back(CGM.getBlockDescriptorType());
+
+  assert(elementTypes.size() == BlockHeaderSize);
+}
+
+/// 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);
+
+  if (!block->hasCaptures()) {
+    info.StructureType =
+      llvm::StructType::get(CGM.getLLVMContext(), elementTypes, true);
+    info.CanBeGlobal = true;
+    return;
+  }
+
+  // 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()) {
+    const DeclContext *DC = block->getDeclContext();
+    for (; isa<BlockDecl>(DC); DC = cast<BlockDecl>(DC)->getDeclContext())
+      ;
+    QualType thisType;
+    if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(DC))
+      thisType = C.getPointerType(C.getRecordType(RD));
+    else
+      thisType = cast<CXXMethodDecl>(DC)->getThisType(C);
+
+    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, 0, llvmType));
+  }
+
+  // Next, all the block captures.
+  for (BlockDecl::capture_const_iterator ci = block->capture_begin(),
+         ce = block->capture_end(); ci != ce; ++ci) {
+    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.
+      QualType byRefPtrTy = C.VoidPtrTy;
+
+      llvm::Type *llvmType = CGM.getTypes().ConvertType(byRefPtrTy);
+      std::pair<CharUnits,CharUnits> tinfo
+        = CGM.getContext().getTypeInfoInChars(byRefPtrTy);
+      maxFieldAlign = std::max(maxFieldAlign, tinfo.second);
+
+      layout.push_back(BlockLayoutChunk(tinfo.second, tinfo.first,
+                                        &*ci, llvmType));
+      continue;
+    }
+
+    // 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);
+      continue;
+    }
+
+    // If we have a lifetime qualifier, honor it for capture purposes.
+    // That includes *not* copying it if it's __unsafe_unretained.
+    if (Qualifiers::ObjCLifetime lifetime 
+          = variable->getType().getObjCLifetime()) {
+      switch (lifetime) {
+      case Qualifiers::OCL_None: llvm_unreachable("impossible");
+      case Qualifiers::OCL_ExplicitNone:
+      case Qualifiers::OCL_Autoreleasing:
+        break;
+
+      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()) {
+      info.NeedsCopyDispose = true;
+
+    // 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 = variable->getType();
+    CharUnits size = C.getTypeSizeInChars(VT);
+    CharUnits align = C.getDeclAlign(variable);
+    
+    maxFieldAlign = std::max(maxFieldAlign, align);
+
+    llvm::Type *llvmType =
+      CGM.getTypes().ConvertTypeForMem(VT);
+    
+    layout.push_back(BlockLayoutChunk(align, size, &*ci, llvmType));
+  }
+
+  // If that was everything, we're done here.
+  if (layout.empty()) {
+    info.StructureType =
+      llvm::StructType::get(CGM.getLLVMContext(), elementTypes, true);
+    info.CanBeGlobal = true;
+    return;
+  }
+
+  // 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());
+
+  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) {
+    SmallVectorImpl<BlockLayoutChunk>::iterator
+      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());
+        elementTypes.push_back(li->Type);
+        blockSize += li->Size;
+        endAlign = getLowBit(blockSize);
+
+        // ...until we get to the alignment of the maximum field.
+        if (endAlign >= maxFieldAlign)
+          break;
+      }
+
+      // Don't re-append everything we just appended.
+      layout.erase(first, li);
+    }
+  }
+
+  // At this point, we just have to add padding if the end align still
+  // isn't aligned right.
+  if (endAlign < maxFieldAlign) {
+    CharUnits padding = maxFieldAlign - endAlign;
+
+    elementTypes.push_back(llvm::ArrayType::get(CGM.Int8Ty,
+                                                padding.getQuantity()));
+    blockSize += padding;
+
+    endAlign = getLowBit(blockSize);
+    assert(endAlign >= maxFieldAlign);
+  }
+
+  // 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) {
+    assert(endAlign >= li->Alignment);
+    li->setIndex(info, elementTypes.size());
+    elementTypes.push_back(li->Type);
+    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) {
+  assert(CGF.HaveInsertPoint());
+
+  // 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.Address =
+    CGF.CreateTempAlloca(blockInfo.StructureType, "block");
+  blockInfo.Address->setAlignment(blockInfo.BlockAlign.getQuantity());
+
+  // 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 (BlockDecl::capture_const_iterator ci = block->capture_begin(),
+         ce = block->capture_end(); ci != ce; ++ci) {
+    // 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::DestructionKind dtorKind =
+      variable->getType().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.
+    if (dtorKind == QualType::DK_objc_strong_lifetime) {
+      destroyer = CodeGenFunction::destroyARCStrongImprecise;
+    } else {
+      destroyer = CGF.getDestroyer(dtorKind);
+    }
+
+    // GEP down to the address.
+    llvm::Value *addr = CGF.Builder.CreateStructGEP(blockInfo.Address,
+                                                    capture.getIndex());
+
+    // We can use that GEP as the dominating IP.
+    if (!blockInfo.DominatingIP)
+      blockInfo.DominatingIP = cast<llvm::Instruction>(addr);
+
+    CleanupKind cleanupKind = InactiveNormalCleanup;
+    bool useArrayEHCleanup = CGF.needsEHCleanup(dtorKind);
+    if (useArrayEHCleanup) 
+      cleanupKind = InactiveNormalAndEHCleanup;
+
+    CGF.pushDestroy(cleanupKind, addr, variable->getType(),
+                    destroyer, useArrayEHCleanup);
+
+    // Remember where that cleanup was.
+    capture.setCleanup(CGF.EHStack.stable_begin());
+  }
+}
+
+/// 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 != 0);
+}
+
+/// Emit a block literal expression in the current function.
+llvm::Value *CodeGenFunction::EmitBlockLiteral(const BlockExpr *blockExpr) {
+  // If the block has no captures, we won't have a pre-computed
+  // layout for it.
+  if (!blockExpr->getBlockDecl()->hasCaptures()) {
+    CGBlockInfo blockInfo(blockExpr->getBlockDecl(), CurFn->getName());
+    computeBlockInfo(CGM, this, blockInfo);
+    blockInfo.BlockExpression = blockExpr;
+    return EmitBlockLiteral(blockInfo);
+  }
+
+  // Find the block info for this block and take ownership of it.
+  OwningPtr<CGBlockInfo> blockInfo;
+  blockInfo.reset(findAndRemoveBlockInfo(&FirstBlockInfo,
+                                         blockExpr->getBlockDecl()));
+
+  blockInfo->BlockExpression = blockExpr;
+  return EmitBlockLiteral(*blockInfo);
+}
+
+llvm::Value *CodeGenFunction::EmitBlockLiteral(const CGBlockInfo &blockInfo) {
+  // Using the computed layout, generate the actual block function.
+  bool isLambdaConv = blockInfo.getBlockDecl()->isConversionFromLambda();
+  llvm::Constant *blockFn
+    = CodeGenFunction(CGM).GenerateBlockFunction(CurGD, blockInfo,
+                                                 CurFuncDecl, LocalDeclMap,
+                                                 isLambdaConv);
+  blockFn = llvm::ConstantExpr::getBitCast(blockFn, VoidPtrTy);
+
+  // If there is nothing to capture, we can emit this as a global block.
+  if (blockInfo.CanBeGlobal)
+    return buildGlobalBlock(CGM, blockInfo, blockFn);
+
+  // Otherwise, we have to emit this as a local block.
+
+  llvm::Constant *isa = CGM.getNSConcreteStackBlock();
+  isa = llvm::ConstantExpr::getBitCast(isa, VoidPtrTy);
+
+  // Build the block descriptor.
+  llvm::Constant *descriptor = buildBlockDescriptor(CGM, blockInfo);
+
+  llvm::AllocaInst *blockAddr = blockInfo.Address;
+  assert(blockAddr && "block has no address!");
+
+  // Compute the initial on-stack block flags.
+  BlockFlags flags = BLOCK_HAS_SIGNATURE;
+  if (blockInfo.NeedsCopyDispose) flags |= BLOCK_HAS_COPY_DISPOSE;
+  if (blockInfo.HasCXXObject) flags |= BLOCK_HAS_CXX_OBJ;
+  if (blockInfo.UsesStret) flags |= BLOCK_USE_STRET;
+
+  // Initialize the block literal.
+  Builder.CreateStore(isa, Builder.CreateStructGEP(blockAddr, 0, "block.isa"));
+  Builder.CreateStore(llvm::ConstantInt::get(IntTy, flags.getBitMask()),
+                      Builder.CreateStructGEP(blockAddr, 1, "block.flags"));
+  Builder.CreateStore(llvm::ConstantInt::get(IntTy, 0),
+                      Builder.CreateStructGEP(blockAddr, 2, "block.reserved"));
+  Builder.CreateStore(blockFn, Builder.CreateStructGEP(blockAddr, 3,
+                                                       "block.invoke"));
+  Builder.CreateStore(descriptor, Builder.CreateStructGEP(blockAddr, 4,
+                                                          "block.descriptor"));
+
+  // Finally, capture all the values into the block.
+  const BlockDecl *blockDecl = blockInfo.getBlockDecl();
+
+  // First, 'this'.
+  if (blockDecl->capturesCXXThis()) {
+    llvm::Value *addr = Builder.CreateStructGEP(blockAddr,
+                                                blockInfo.CXXThisIndex,
+                                                "block.captured-this.addr");
+    Builder.CreateStore(LoadCXXThis(), addr);
+  }
+
+  // Next, captured variables.
+  for (BlockDecl::capture_const_iterator ci = blockDecl->capture_begin(),
+         ce = blockDecl->capture_end(); ci != ce; ++ci) {
+    const VarDecl *variable = ci->getVariable();
+    const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
+
+    // Ignore constant captures.
+    if (capture.isConstant()) continue;
+
+    QualType type = variable->getType();
+
+    // This will be a [[type]]*, except that a byref entry will just be
+    // an i8**.
+    llvm::Value *blockField =
+      Builder.CreateStructGEP(blockAddr, capture.getIndex(),
+                              "block.captured");
+
+    // Compute the address of the thing we're going to move into the
+    // block literal.
+    llvm::Value *src;
+    if (ci->isNested()) {
+      // We need to use the capture from the enclosing block.
+      const CGBlockInfo::Capture &enclosingCapture =
+        BlockInfo->getCapture(variable);
+
+      // This is a [[type]]*, except that a byref entry wil just be an i8**.
+      src = Builder.CreateStructGEP(LoadBlockStruct(),
+                                    enclosingCapture.getIndex(),
+                                    "block.capture.addr");
+    } else if (blockDecl->isConversionFromLambda()) {
+      // The lambda capture in a lambda's conversion-to-block-pointer is
+      // special; we'll simply emit it directly.
+      src = 0;
+    } else {
+      // This is a [[type]]*.
+      src = LocalDeclMap[variable];
+    }
+
+    // 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.
+      if (ci->isNested())
+        src = Builder.CreateLoad(src, "byref.capture");
+      else
+        src = Builder.CreateBitCast(src, VoidPtrTy);
+
+      // Write that void* into the capture field.
+      Builder.CreateStore(src, 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.
+        CharUnits Align = getContext().getTypeAlignInChars(type);
+        AggValueSlot Slot =
+            AggValueSlot::forAddr(blockField, Align, Qualifiers(),
+                                  AggValueSlot::IsDestructed,
+                                  AggValueSlot::DoesNotNeedGCBarriers,
+                                  AggValueSlot::IsNotAliased);
+        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(Builder.CreateLoad(src, "ref.val"), 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(/*DC*/ 0, SourceLocation(),
+                                            /*name*/ 0, type);
+
+      // We use one of these or the other depending on whether the
+      // reference is nested.
+      DeclRefExpr declRef(const_cast<VarDecl*>(variable),
+                          /*refersToEnclosing*/ ci->isNested(), type,
+                          VK_LValue, SourceLocation());
+
+      ImplicitCastExpr l2r(ImplicitCastExpr::OnStack, type, CK_LValueToRValue,
+                           &declRef, VK_RValue);
+      EmitExprAsInit(&l2r, &blockFieldPseudoVar,
+                     MakeAddrLValue(blockField, type,
+                                    getContext().getDeclAlign(variable)),
+                     /*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.CreateBitCast(blockAddr,
+                          ConvertType(blockInfo.getBlockExpr()->getType()));
+
+  return result;
+}
+
+
+llvm::Type *CodeGenModule::getBlockDescriptorType() {
+  if (BlockDescriptorType)
+    return BlockDescriptorType;
+
+  llvm::Type *UnsignedLongTy =
+    getTypes().ConvertType(getContext().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, NULL);
+
+  // Now form a pointer to that.
+  BlockDescriptorType = llvm::PointerType::getUnqual(BlockDescriptorType);
+  return BlockDescriptorType;
+}
+
+llvm::Type *CodeGenModule::getGenericBlockLiteralType() {
+  if (GenericBlockLiteralType)
+    return GenericBlockLiteralType;
+
+  llvm::Type *BlockDescPtrTy = getBlockDescriptorType();
+
+  // 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, NULL);
+
+  return GenericBlockLiteralType;
+}
+
+
+RValue CodeGenFunction::EmitBlockCallExpr(const CallExpr* E, 
+                                          ReturnValueSlot ReturnValue) {
+  const BlockPointerType *BPT =
+    E->getCallee()->getType()->getAs<BlockPointerType>();
+
+  llvm::Value *Callee = EmitScalarExpr(E->getCallee());
+
+  // Get a pointer to the generic block literal.
+  llvm::Type *BlockLiteralTy =
+    llvm::PointerType::getUnqual(CGM.getGenericBlockLiteralType());
+
+  // Bitcast the callee to a block literal.
+  llvm::Value *BlockLiteral =
+    Builder.CreateBitCast(Callee, BlockLiteralTy, "block.literal");
+
+  // Get the function pointer from the literal.
+  llvm::Value *FuncPtr = Builder.CreateStructGEP(BlockLiteral, 3);
+
+  BlockLiteral = Builder.CreateBitCast(BlockLiteral, VoidPtrTy);
+
+  // Add the block literal.
+  CallArgList Args;
+  Args.add(RValue::get(BlockLiteral), getContext().VoidPtrTy);
+
+  QualType FnType = BPT->getPointeeType();
+
+  // And the rest of the arguments.
+  EmitCallArgs(Args, FnType->getAs<FunctionProtoType>(),
+               E->arg_begin(), E->arg_end());
+
+  // Load the function.
+  llvm::Value *Func = Builder.CreateLoad(FuncPtr);
+
+  const FunctionType *FuncTy = FnType->castAs<FunctionType>();
+  const CGFunctionInfo &FnInfo =
+    CGM.getTypes().arrangeFunctionCall(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.CreateBitCast(Func, BlockFTyPtr);
+
+  // And call the block.
+  return EmitCall(FnInfo, Func, ReturnValue, Args);
+}
+
+llvm::Value *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[variable];
+
+  llvm::Value *addr =
+    Builder.CreateStructGEP(LoadBlockStruct(), capture.getIndex(),
+                            "block.capture.addr");
+
+  if (isByRef) {
+    // addr should be a void** right now.  Load, then cast the result
+    // to byref*.
+
+    addr = Builder.CreateLoad(addr);
+    llvm::PointerType *byrefPointerType
+      = llvm::PointerType::get(BuildByRefType(variable), 0);
+    addr = Builder.CreateBitCast(addr, byrefPointerType,
+                                 "byref.addr");
+
+    // Follow the forwarding pointer.
+    addr = Builder.CreateStructGEP(addr, 1, "byref.forwarding");
+    addr = Builder.CreateLoad(addr, "byref.addr.forwarded");
+
+    // Cast back to byref* and GEP over to the actual object.
+    addr = Builder.CreateBitCast(addr, byrefPointerType);
+    addr = Builder.CreateStructGEP(addr, getByRefValueLLVMField(variable), 
+                                   variable->getNameAsString());
+  }
+
+  if (variable->getType()->isReferenceType())
+    addr = Builder.CreateLoad(addr, "ref.tmp");
+
+  return addr;
+}
+
+llvm::Constant *
+CodeGenModule::GetAddrOfGlobalBlock(const BlockExpr *blockExpr,
+                                    const char *name) {
+  CGBlockInfo blockInfo(blockExpr->getBlockDecl(), name);
+  blockInfo.BlockExpression = blockExpr;
+
+  // Compute information about the layout, etc., of this block.
+  computeBlockInfo(*this, 0, blockInfo);
+
+  // Using that metadata, generate the actual block function.
+  llvm::Constant *blockFn;
+  {
+    llvm::DenseMap<const Decl*, llvm::Value*> LocalDeclMap;
+    blockFn = CodeGenFunction(*this).GenerateBlockFunction(GlobalDecl(),
+                                                           blockInfo,
+                                                           0, LocalDeclMap,
+                                                           false);
+  }
+  blockFn = llvm::ConstantExpr::getBitCast(blockFn, VoidPtrTy);
+
+  return buildGlobalBlock(*this, blockInfo, blockFn);
+}
+
+static llvm::Constant *buildGlobalBlock(CodeGenModule &CGM,
+                                        const CGBlockInfo &blockInfo,
+                                        llvm::Constant *blockFn) {
+  assert(blockInfo.CanBeGlobal);
+
+  // Generate the constants for the block literal initializer.
+  llvm::Constant *fields[BlockHeaderSize];
+
+  // isa
+  fields[0] = CGM.getNSConcreteGlobalBlock();
+
+  // __flags
+  BlockFlags flags = BLOCK_IS_GLOBAL | BLOCK_HAS_SIGNATURE;
+  if (blockInfo.UsesStret) flags |= BLOCK_USE_STRET;
+                                      
+  fields[1] = llvm::ConstantInt::get(CGM.IntTy, flags.getBitMask());
+
+  // Reserved
+  fields[2] = llvm::Constant::getNullValue(CGM.IntTy);
+
+  // Function
+  fields[3] = blockFn;
+
+  // Descriptor
+  fields[4] = buildBlockDescriptor(CGM, blockInfo);
+
+  llvm::Constant *init = llvm::ConstantStruct::getAnon(fields);
+
+  llvm::GlobalVariable *literal =
+    new llvm::GlobalVariable(CGM.getModule(),
+                             init->getType(),
+                             /*constant*/ true,
+                             llvm::GlobalVariable::InternalLinkage,
+                             init,
+                             "__block_literal_global");
+  literal->setAlignment(blockInfo.BlockAlign.getQuantity());
+
+  // Return a constant of the appropriately-casted type.
+  llvm::Type *requiredType =
+    CGM.getTypes().ConvertType(blockInfo.getBlockExpr()->getType());
+  return llvm::ConstantExpr::getBitCast(literal, requiredType);
+}
+
+llvm::Function *
+CodeGenFunction::GenerateBlockFunction(GlobalDecl GD,
+                                       const CGBlockInfo &blockInfo,
+                                       const Decl *outerFnDecl,
+                                       const DeclMapTy &ldm,
+                                       bool IsLambdaConversionToBlock) {
+  const BlockDecl *blockDecl = blockInfo.getBlockDecl();
+
+  // Check if we should generate debug info for this block function.
+  if (CGM.getModuleDebugInfo())
+    DebugInfo = CGM.getModuleDebugInfo();
+
+  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 VarDecl *var = dyn_cast<VarDecl>(i->first);
+    if (var && !var->hasLocalStorage())
+      LocalDeclMap[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;
+  IdentifierInfo *II = &CGM.getContext().Idents.get(".block_descriptor");
+
+  ImplicitParamDecl selfDecl(const_cast<BlockDecl*>(blockDecl),
+                             SourceLocation(), II, selfTy);
+  args.push_back(&selfDecl);
+
+  // Now add the rest of the parameters.
+  for (BlockDecl::param_const_iterator i = blockDecl->param_begin(),
+       e = blockDecl->param_end(); i != e; ++i)
+    args.push_back(*i);
+
+  // Create the function declaration.
+  const FunctionProtoType *fnType = blockInfo.getBlockExpr()->getFunctionType();
+  const CGFunctionInfo &fnInfo =
+    CGM.getTypes().arrangeFunctionDeclaration(fnType->getResultType(), args,
+                                              fnType->getExtInfo(),
+                                              fnType->isVariadic());
+  if (CGM.ReturnTypeUsesSRet(fnInfo))
+    blockInfo.UsesStret = true;
+
+  llvm::FunctionType *fnLLVMType = CGM.getTypes().GetFunctionType(fnInfo);
+
+  MangleBuffer name;
+  CGM.getBlockMangledName(GD, name, blockDecl);
+  llvm::Function *fn =
+    llvm::Function::Create(fnLLVMType, llvm::GlobalValue::InternalLinkage, 
+                           name.getString(), &CGM.getModule());
+  CGM.SetInternalFunctionAttributes(blockDecl, fn, fnInfo);
+
+  // Begin generating the function.
+  StartFunction(blockDecl, fnType->getResultType(), fn, fnInfo, args,
+                blockInfo.getBlockExpr()->getBody()->getLocStart());
+  CurFuncDecl = outerFnDecl; // StartFunction sets this to blockDecl
+
+  // Okay.  Undo some of what StartFunction did.
+  
+  // Pull the 'self' reference out of the local decl map.
+  llvm::Value *blockAddr = LocalDeclMap[&selfDecl];
+  LocalDeclMap.erase(&selfDecl);
+  BlockPointer = Builder.CreateBitCast(blockAddr,
+                                       blockInfo.StructureType->getPointerTo(),
+                                       "block");
+
+  // If we have a C++ 'this' reference, go ahead and force it into
+  // existence now.
+  if (blockDecl->capturesCXXThis()) {
+    llvm::Value *addr = Builder.CreateStructGEP(BlockPointer,
+                                                blockInfo.CXXThisIndex,
+                                                "block.captured-this");
+    CXXThisValue = Builder.CreateLoad(addr, "this");
+  }
+
+  // LoadObjCSelf() expects there to be an entry for 'self' in LocalDeclMap;
+  // appease it.
+  if (const ObjCMethodDecl *method
+        = dyn_cast_or_null<ObjCMethodDecl>(CurFuncDecl)) {
+    const VarDecl *self = method->getSelfDecl();
+
+    // There might not be a capture for 'self', but if there is...
+    if (blockInfo.Captures.count(self)) {
+      const CGBlockInfo::Capture &capture = blockInfo.getCapture(self);
+      llvm::Value *selfAddr = Builder.CreateStructGEP(BlockPointer,
+                                                      capture.getIndex(),
+                                                      "block.captured-self");
+      LocalDeclMap[self] = selfAddr;
+    }
+  }
+
+  // Also force all the constant captures.
+  for (BlockDecl::capture_const_iterator ci = blockDecl->capture_begin(),
+         ce = blockDecl->capture_end(); ci != ce; ++ci) {
+    const VarDecl *variable = ci->getVariable();
+    const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
+    if (!capture.isConstant()) continue;
+
+    unsigned align = getContext().getDeclAlign(variable).getQuantity();
+
+    llvm::AllocaInst *alloca =
+      CreateMemTemp(variable->getType(), "block.captured-const");
+    alloca->setAlignment(align);
+
+    Builder.CreateStore(capture.getConstant(), alloca, align);
+
+    LocalDeclMap[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();
+  --entry_ptr;
+
+  if (IsLambdaConversionToBlock)
+    EmitLambdaBlockInvokeBody();
+  else
+    EmitStmt(blockDecl->getBody());
+
+  // Remember where we were...
+  llvm::BasicBlock *resume = Builder.GetInsertBlock();
+
+  // Go back to the entry.
+  ++entry_ptr;
+  Builder.SetInsertPoint(entry, entry_ptr);
+
+  // Emit debug information for all the DeclRefExprs.
+  // FIXME: also for 'this'
+  if (CGDebugInfo *DI = getDebugInfo()) {
+    for (BlockDecl::capture_const_iterator ci = blockDecl->capture_begin(),
+           ce = blockDecl->capture_end(); ci != ce; ++ci) {
+      const VarDecl *variable = ci->getVariable();
+      DI->EmitLocation(Builder, variable->getLocation());
+
+      const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
+      if (capture.isConstant()) {
+        DI->EmitDeclareOfAutoVariable(variable, LocalDeclMap[variable],
+                                      Builder);
+        continue;
+      }
+
+      DI->EmitDeclareOfBlockDeclRefVariable(variable, BlockPointer,
+                                            Builder, blockInfo);
+    }
+  }
+
+  // And resume where we left off.
+  if (resume == 0)
+    Builder.ClearInsertionPoint();
+  else
+    Builder.SetInsertPoint(resume);
+
+  FinishFunction(cast<CompoundStmt>(blockDecl->getBody())->getRBracLoc());
+
+  return fn;
+}
+
+/*
+    notes.push_back(HelperInfo());
+    HelperInfo &note = notes.back();
+    note.index = capture.getIndex();
+    note.RequiresCopying = (ci->hasCopyExpr() || BlockRequiresCopying(type));
+    note.cxxbar_import = ci->getCopyExpr();
+
+    if (ci->isByRef()) {
+      note.flag = BLOCK_FIELD_IS_BYREF;
+      if (type.isObjCGCWeak())
+        note.flag |= BLOCK_FIELD_IS_WEAK;
+    } else if (type->isBlockPointerType()) {
+      note.flag = BLOCK_FIELD_IS_BLOCK;
+    } else {
+      note.flag = BLOCK_FIELD_IS_OBJECT;
+    }
+ */
+
+
+
+llvm::Constant *
+CodeGenFunction::GenerateCopyHelperFunction(const CGBlockInfo &blockInfo) {
+  ASTContext &C = getContext();
+
+  FunctionArgList args;
+  ImplicitParamDecl dstDecl(0, SourceLocation(), 0, C.VoidPtrTy);
+  args.push_back(&dstDecl);
+  ImplicitParamDecl srcDecl(0, SourceLocation(), 0, C.VoidPtrTy);
+  args.push_back(&srcDecl);
+
+  const CGFunctionInfo &FI =
+    CGM.getTypes().arrangeFunctionDeclaration(C.VoidTy, args,
+                                              FunctionType::ExtInfo(),
+                                              /*variadic*/ false);
+
+  // 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_");
+
+  // Check if we should generate debug info for this block helper function.
+  if (CGM.getModuleDebugInfo())
+    DebugInfo = CGM.getModuleDebugInfo();
+
+  FunctionDecl *FD = FunctionDecl::Create(C,
+                                          C.getTranslationUnitDecl(),
+                                          SourceLocation(),
+                                          SourceLocation(), II, C.VoidTy, 0,
+                                          SC_Static,
+                                          SC_None,
+                                          false,
+                                          false);
+  StartFunction(FD, C.VoidTy, Fn, FI, args, SourceLocation());
+
+  llvm::Type *structPtrTy = blockInfo.StructureType->getPointerTo();
+
+  llvm::Value *src = GetAddrOfLocalVar(&srcDecl);
+  src = Builder.CreateLoad(src);
+  src = Builder.CreateBitCast(src, structPtrTy, "block.source");
+
+  llvm::Value *dst = GetAddrOfLocalVar(&dstDecl);
+  dst = Builder.CreateLoad(dst);
+  dst = Builder.CreateBitCast(dst, structPtrTy, "block.dest");
+
+  const BlockDecl *blockDecl = blockInfo.getBlockDecl();
+
+  for (BlockDecl::capture_const_iterator ci = blockDecl->capture_begin(),
+         ce = blockDecl->capture_end(); ci != ce; ++ci) {
+    const VarDecl *variable = ci->getVariable();
+    QualType type = variable->getType();
+
+    const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
+    if (capture.isConstant()) continue;
+
+    const Expr *copyExpr = ci->getCopyExpr();
+    BlockFieldFlags flags;
+
+    bool isARCWeakCapture = false;
+
+    if (copyExpr) {
+      assert(!ci->isByRef());
+      // don't bother computing flags
+
+    } else if (ci->isByRef()) {
+      flags = BLOCK_FIELD_IS_BYREF;
+      if (type.isObjCGCWeak())
+        flags |= BLOCK_FIELD_IS_WEAK;
+
+    } else if (type->isObjCRetainableType()) {
+      flags = BLOCK_FIELD_IS_OBJECT;
+      if (type->isBlockPointerType())
+        flags = BLOCK_FIELD_IS_BLOCK;
+
+      // Special rules for ARC captures:
+      if (getLangOpts().ObjCAutoRefCount) {
+        Qualifiers qs = type.getQualifiers();
+
+        // Don't generate special copy logic for a captured object
+        // unless it's __strong or __weak.
+        if (!qs.hasStrongOrWeakObjCLifetime())
+          continue;
+
+        // Support __weak direct captures.
+        if (qs.getObjCLifetime() == Qualifiers::OCL_Weak)
+          isARCWeakCapture = true;
+      }
+    } else {
+      continue;
+    }
+
+    unsigned index = capture.getIndex();
+    llvm::Value *srcField = Builder.CreateStructGEP(src, index);
+    llvm::Value *dstField = Builder.CreateStructGEP(dst, index);
+
+    // If there's an explicit copy expression, we do that.
+    if (copyExpr) {
+      EmitSynthesizedCXXCopyCtor(dstField, srcField, copyExpr);
+    } else if (isARCWeakCapture) {
+      EmitARCCopyWeak(dstField, srcField);
+    } else {
+      llvm::Value *srcValue = Builder.CreateLoad(srcField, "blockcopy.src");
+      srcValue = Builder.CreateBitCast(srcValue, VoidPtrTy);
+      llvm::Value *dstAddr = Builder.CreateBitCast(dstField, VoidPtrTy);
+      Builder.CreateCall3(CGM.getBlockObjectAssign(), dstAddr, srcValue,
+                          llvm::ConstantInt::get(Int32Ty, flags.getBitMask()));
+    }
+  }
+
+  FinishFunction();
+
+  return llvm::ConstantExpr::getBitCast(Fn, VoidPtrTy);
+}
+
+llvm::Constant *
+CodeGenFunction::GenerateDestroyHelperFunction(const CGBlockInfo &blockInfo) {
+  ASTContext &C = getContext();
+
+  FunctionArgList args;
+  ImplicitParamDecl srcDecl(0, SourceLocation(), 0, C.VoidPtrTy);
+  args.push_back(&srcDecl);
+
+  const CGFunctionInfo &FI =
+    CGM.getTypes().arrangeFunctionDeclaration(C.VoidTy, args,
+                                              FunctionType::ExtInfo(),
+                                              /*variadic*/ false);
+
+  // 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());
+
+  // Check if we should generate debug info for this block destroy function.
+  if (CGM.getModuleDebugInfo())
+    DebugInfo = CGM.getModuleDebugInfo();
+
+  IdentifierInfo *II
+    = &CGM.getContext().Idents.get("__destroy_helper_block_");
+
+  FunctionDecl *FD = FunctionDecl::Create(C, C.getTranslationUnitDecl(),
+                                          SourceLocation(),
+                                          SourceLocation(), II, C.VoidTy, 0,
+                                          SC_Static,
+                                          SC_None,
+                                          false, false);
+  StartFunction(FD, C.VoidTy, Fn, FI, args, SourceLocation());
+
+  llvm::Type *structPtrTy = blockInfo.StructureType->getPointerTo();
+
+  llvm::Value *src = GetAddrOfLocalVar(&srcDecl);
+  src = Builder.CreateLoad(src);
+  src = Builder.CreateBitCast(src, structPtrTy, "block");
+
+  const BlockDecl *blockDecl = blockInfo.getBlockDecl();
+
+  CodeGenFunction::RunCleanupsScope cleanups(*this);
+
+  for (BlockDecl::capture_const_iterator ci = blockDecl->capture_begin(),
+         ce = blockDecl->capture_end(); ci != ce; ++ci) {
+    const VarDecl *variable = ci->getVariable();
+    QualType type = variable->getType();
+
+    const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
+    if (capture.isConstant()) continue;
+
+    BlockFieldFlags flags;
+    const CXXDestructorDecl *dtor = 0;
+
+    bool isARCWeakCapture = false;
+
+    if (ci->isByRef()) {
+      flags = BLOCK_FIELD_IS_BYREF;
+      if (type.isObjCGCWeak())
+        flags |= BLOCK_FIELD_IS_WEAK;
+    } else if (const CXXRecordDecl *record = type->getAsCXXRecordDecl()) {
+      if (record->hasTrivialDestructor())
+        continue;
+      dtor = record->getDestructor();
+    } else if (type->isObjCRetainableType()) {
+      flags = BLOCK_FIELD_IS_OBJECT;
+      if (type->isBlockPointerType())
+        flags = BLOCK_FIELD_IS_BLOCK;
+
+      // Special rules for ARC captures.
+      if (getLangOpts().ObjCAutoRefCount) {
+        Qualifiers qs = type.getQualifiers();
+
+        // Don't generate special dispose logic for a captured object
+        // unless it's __strong or __weak.
+        if (!qs.hasStrongOrWeakObjCLifetime())
+          continue;
+
+        // Support __weak direct captures.
+        if (qs.getObjCLifetime() == Qualifiers::OCL_Weak)
+          isARCWeakCapture = true;
+      }
+    } else {
+      continue;
+    }
+
+    unsigned index = capture.getIndex();
+    llvm::Value *srcField = Builder.CreateStructGEP(src, index);
+
+    // If there's an explicit copy expression, we do that.
+    if (dtor) {
+      PushDestructorCleanup(dtor, srcField);
+
+    // If this is a __weak capture, emit the release directly.
+    } else if (isARCWeakCapture) {
+      EmitARCDestroyWeak(srcField);
+
+    // 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 {
+      llvm::Value *value = Builder.CreateLoad(srcField);
+      value = Builder.CreateBitCast(value, VoidPtrTy);
+      BuildBlockRelease(value, flags);
+    }
+  }
+
+  cleanups.ForceCleanup();
+
+  FinishFunction();
+
+  return llvm::ConstantExpr::getBitCast(Fn, VoidPtrTy);
+}
+
+namespace {
+
+/// Emits the copy/dispose helper functions for a __block object of id type.
+class ObjectByrefHelpers : public CodeGenModule::ByrefHelpers {
+  BlockFieldFlags Flags;
+
+public:
+  ObjectByrefHelpers(CharUnits alignment, BlockFieldFlags flags)
+    : ByrefHelpers(alignment), Flags(flags) {}
+
+  void emitCopy(CodeGenFunction &CGF, llvm::Value *destField,
+                llvm::Value *srcField) {
+    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();
+    CGF.Builder.CreateCall3(fn, destField, srcValue, flagsVal);
+  }
+
+  void emitDispose(CodeGenFunction &CGF, llvm::Value *field) {
+    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 {
+    id.AddInteger(Flags.getBitMask());
+  }
+};
+
+/// Emits the copy/dispose helpers for an ARC __block __weak variable.
+class ARCWeakByrefHelpers : public CodeGenModule::ByrefHelpers {
+public:
+  ARCWeakByrefHelpers(CharUnits alignment) : ByrefHelpers(alignment) {}
+
+  void emitCopy(CodeGenFunction &CGF, llvm::Value *destField,
+                llvm::Value *srcField) {
+    CGF.EmitARCMoveWeak(destField, srcField);
+  }
+
+  void emitDispose(CodeGenFunction &CGF, llvm::Value *field) {
+    CGF.EmitARCDestroyWeak(field);
+  }
+
+  void profileImpl(llvm::FoldingSetNodeID &id) const {
+    // 0 is distinguishable from all pointers and byref flags
+    id.AddInteger(0);
+  }
+};
+
+/// Emits the copy/dispose helpers for an ARC __block __strong variable
+/// that's not of block-pointer type.
+class ARCStrongByrefHelpers : public CodeGenModule::ByrefHelpers {
+public:
+  ARCStrongByrefHelpers(CharUnits alignment) : ByrefHelpers(alignment) {}
+
+  void emitCopy(CodeGenFunction &CGF, llvm::Value *destField,
+                llvm::Value *srcField) {
+    // Do a "move" by copying the value and then zeroing out the old
+    // variable.
+
+    llvm::LoadInst *value = CGF.Builder.CreateLoad(srcField);
+    value->setAlignment(Alignment.getQuantity());
+    
+    llvm::Value *null =
+      llvm::ConstantPointerNull::get(cast<llvm::PointerType>(value->getType()));
+
+    llvm::StoreInst *store = CGF.Builder.CreateStore(value, destField);
+    store->setAlignment(Alignment.getQuantity());
+
+    store = CGF.Builder.CreateStore(null, srcField);
+    store->setAlignment(Alignment.getQuantity());
+  }
+
+  void emitDispose(CodeGenFunction &CGF, llvm::Value *field) {
+    llvm::LoadInst *value = CGF.Builder.CreateLoad(field);
+    value->setAlignment(Alignment.getQuantity());
+
+    CGF.EmitARCRelease(value, /*precise*/ false);
+  }
+
+  void profileImpl(llvm::FoldingSetNodeID &id) const {
+    // 1 is distinguishable from all pointers and byref flags
+    id.AddInteger(1);
+  }
+};
+
+/// Emits the copy/dispose helpers for an ARC __block __strong
+/// variable that's of block-pointer type.
+class ARCStrongBlockByrefHelpers : public CodeGenModule::ByrefHelpers {
+public:
+  ARCStrongBlockByrefHelpers(CharUnits alignment) : ByrefHelpers(alignment) {}
+
+  void emitCopy(CodeGenFunction &CGF, llvm::Value *destField,
+                llvm::Value *srcField) {
+    // 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::LoadInst *oldValue = CGF.Builder.CreateLoad(srcField);
+    oldValue->setAlignment(Alignment.getQuantity());
+
+    llvm::Value *copy = CGF.EmitARCRetainBlock(oldValue, /*mandatory*/ true);
+
+    llvm::StoreInst *store = CGF.Builder.CreateStore(copy, destField);
+    store->setAlignment(Alignment.getQuantity());
+  }
+
+  void emitDispose(CodeGenFunction &CGF, llvm::Value *field) {
+    llvm::LoadInst *value = CGF.Builder.CreateLoad(field);
+    value->setAlignment(Alignment.getQuantity());
+
+    CGF.EmitARCRelease(value, /*precise*/ false);
+  }
+
+  void profileImpl(llvm::FoldingSetNodeID &id) const {
+    // 2 is distinguishable from all pointers and byref flags
+    id.AddInteger(2);
+  }
+};
+
+/// Emits the copy/dispose helpers for a __block variable with a
+/// nontrivial copy constructor or destructor.
+class CXXByrefHelpers : public CodeGenModule::ByrefHelpers {
+  QualType VarType;
+  const Expr *CopyExpr;
+
+public:
+  CXXByrefHelpers(CharUnits alignment, QualType type,
+                  const Expr *copyExpr)
+    : ByrefHelpers(alignment), VarType(type), CopyExpr(copyExpr) {}
+
+  bool needsCopy() const { return CopyExpr != 0; }
+  void emitCopy(CodeGenFunction &CGF, llvm::Value *destField,
+                llvm::Value *srcField) {
+    if (!CopyExpr) return;
+    CGF.EmitSynthesizedCXXCopyCtor(destField, srcField, CopyExpr);
+  }
+
+  void emitDispose(CodeGenFunction &CGF, llvm::Value *field) {
+    EHScopeStack::stable_iterator cleanupDepth = CGF.EHStack.stable_begin();
+    CGF.PushDestructorCleanup(VarType, field);
+    CGF.PopCleanupBlocks(cleanupDepth);
+  }
+
+  void profileImpl(llvm::FoldingSetNodeID &id) const {
+    id.AddPointer(VarType.getCanonicalType().getAsOpaquePtr());
+  }
+};
+} // end anonymous namespace
+
+static llvm::Constant *
+generateByrefCopyHelper(CodeGenFunction &CGF,
+                        llvm::StructType &byrefType,
+                        CodeGenModule::ByrefHelpers &byrefInfo) {
+  ASTContext &Context = CGF.getContext();
+
+  QualType R = Context.VoidTy;
+
+  FunctionArgList args;
+  ImplicitParamDecl dst(0, SourceLocation(), 0, Context.VoidPtrTy);
+  args.push_back(&dst);
+
+  ImplicitParamDecl src(0, SourceLocation(), 0, Context.VoidPtrTy);
+  args.push_back(&src);
+
+  const CGFunctionInfo &FI =
+    CGF.CGM.getTypes().arrangeFunctionDeclaration(R, args,
+                                                  FunctionType::ExtInfo(),
+                                                  /*variadic*/ false);
+
+  CodeGenTypes &Types = CGF.CGM.getTypes();
+  llvm::FunctionType *LTy = Types.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,
+                                          Context.getTranslationUnitDecl(),
+                                          SourceLocation(),
+                                          SourceLocation(), II, R, 0,
+                                          SC_Static,
+                                          SC_None,
+                                          false, false);
+
+  CGF.StartFunction(FD, R, Fn, FI, args, SourceLocation());
+
+  if (byrefInfo.needsCopy()) {
+    llvm::Type *byrefPtrType = byrefType.getPointerTo(0);
+
+    // dst->x
+    llvm::Value *destField = CGF.GetAddrOfLocalVar(&dst);
+    destField = CGF.Builder.CreateLoad(destField);
+    destField = CGF.Builder.CreateBitCast(destField, byrefPtrType);
+    destField = CGF.Builder.CreateStructGEP(destField, 6, "x");
+
+    // src->x
+    llvm::Value *srcField = CGF.GetAddrOfLocalVar(&src);
+    srcField = CGF.Builder.CreateLoad(srcField);
+    srcField = CGF.Builder.CreateBitCast(srcField, byrefPtrType);
+    srcField = CGF.Builder.CreateStructGEP(srcField, 6, "x");
+
+    byrefInfo.emitCopy(CGF, destField, srcField);
+  }  
+
+  CGF.FinishFunction();
+
+  return llvm::ConstantExpr::getBitCast(Fn, CGF.Int8PtrTy);
+}
+
+/// Build the copy helper for a __block variable.
+static llvm::Constant *buildByrefCopyHelper(CodeGenModule &CGM,
+                                            llvm::StructType &byrefType,
+                                            CodeGenModule::ByrefHelpers &info) {
+  CodeGenFunction CGF(CGM);
+  return generateByrefCopyHelper(CGF, byrefType, info);
+}
+
+/// Generate code for a __block variable's dispose helper.
+static llvm::Constant *
+generateByrefDisposeHelper(CodeGenFunction &CGF,
+                           llvm::StructType &byrefType,
+                           CodeGenModule::ByrefHelpers &byrefInfo) {
+  ASTContext &Context = CGF.getContext();
+  QualType R = Context.VoidTy;
+
+  FunctionArgList args;
+  ImplicitParamDecl src(0, SourceLocation(), 0, Context.VoidPtrTy);
+  args.push_back(&src);
+
+  const CGFunctionInfo &FI =
+    CGF.CGM.getTypes().arrangeFunctionDeclaration(R, args,
+                                                  FunctionType::ExtInfo(),
+                                                  /*variadic*/ false);
+
+  CodeGenTypes &Types = CGF.CGM.getTypes();
+  llvm::FunctionType *LTy = Types.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_dispose_",
+                           &CGF.CGM.getModule());
+
+  IdentifierInfo *II
+    = &Context.Idents.get("__Block_byref_object_dispose_");
+
+  FunctionDecl *FD = FunctionDecl::Create(Context,
+                                          Context.getTranslationUnitDecl(),
+                                          SourceLocation(),
+                                          SourceLocation(), II, R, 0,
+                                          SC_Static,
+                                          SC_None,
+                                          false, false);
+  CGF.StartFunction(FD, R, Fn, FI, args, SourceLocation());
+
+  if (byrefInfo.needsDispose()) {
+    llvm::Value *V = CGF.GetAddrOfLocalVar(&src);
+    V = CGF.Builder.CreateLoad(V);
+    V = CGF.Builder.CreateBitCast(V, byrefType.getPointerTo(0));
+    V = CGF.Builder.CreateStructGEP(V, 6, "x");
+
+    byrefInfo.emitDispose(CGF, V);
+  }
+
+  CGF.FinishFunction();
+
+  return llvm::ConstantExpr::getBitCast(Fn, CGF.Int8PtrTy);
+}
+
+/// Build the dispose helper for a __block variable.
+static llvm::Constant *buildByrefDisposeHelper(CodeGenModule &CGM,
+                                              llvm::StructType &byrefType,
+                                            CodeGenModule::ByrefHelpers &info) {
+  CodeGenFunction CGF(CGM);
+  return generateByrefDisposeHelper(CGF, byrefType, info);
+}
+
+/// 
+template <class T> static T *buildByrefHelpers(CodeGenModule &CGM,
+                                               llvm::StructType &byrefTy,
+                                               T &byrefInfo) {
+  // Increase the field's alignment to be at least pointer alignment,
+  // since the layout of the byref struct will guarantee at least that.
+  byrefInfo.Alignment = std::max(byrefInfo.Alignment,
+                              CharUnits::fromQuantity(CGM.PointerAlignInBytes));
+
+  llvm::FoldingSetNodeID id;
+  byrefInfo.Profile(id);
+
+  void *insertPos;
+  CodeGenModule::ByrefHelpers *node
+    = CGM.ByrefHelpersCache.FindNodeOrInsertPos(id, insertPos);
+  if (node) return static_cast<T*>(node);
+
+  byrefInfo.CopyHelper = buildByrefCopyHelper(CGM, byrefTy, byrefInfo);
+  byrefInfo.DisposeHelper = buildByrefDisposeHelper(CGM, byrefTy, byrefInfo);
+
+  T *copy = new (CGM.getContext()) T(byrefInfo);
+  CGM.ByrefHelpersCache.InsertNode(copy, insertPos);
+  return copy;
+}
+
+CodeGenModule::ByrefHelpers *
+CodeGenFunction::buildByrefHelpers(llvm::StructType &byrefType,
+                                   const AutoVarEmission &emission) {
+  const VarDecl &var = *emission.Variable;
+  QualType type = var.getType();
+
+  if (const CXXRecordDecl *record = type->getAsCXXRecordDecl()) {
+    const Expr *copyExpr = CGM.getContext().getBlockVarCopyInits(&var);
+    if (!copyExpr && record->hasTrivialDestructor()) return 0;
+
+    CXXByrefHelpers byrefInfo(emission.Alignment, type, copyExpr);
+    return ::buildByrefHelpers(CGM, byrefType, byrefInfo);
+  }
+
+  // Otherwise, if we don't have a retainable type, there's nothing to do.
+  // that the runtime does extra copies.
+  if (!type->isObjCRetainableType()) return 0;
+
+  Qualifiers qs = type.getQualifiers();
+
+  // If we have lifetime, that dominates.
+  if (Qualifiers::ObjCLifetime lifetime = qs.getObjCLifetime()) {
+    assert(getLangOpts().ObjCAutoRefCount);
+
+    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 0;
+
+    // Tell the runtime that this is ARC __weak, called by the
+    // byref routines.
+    case Qualifiers::OCL_Weak: {
+      ARCWeakByrefHelpers byrefInfo(emission.Alignment);
+      return ::buildByrefHelpers(CGM, byrefType, 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()) {
+        ARCStrongBlockByrefHelpers byrefInfo(emission.Alignment);
+        return ::buildByrefHelpers(CGM, byrefType, byrefInfo);
+
+      // Otherwise, we transfer ownership of the retain from the stack
+      // to the heap.
+      } else {
+        ARCStrongByrefHelpers byrefInfo(emission.Alignment);
+        return ::buildByrefHelpers(CGM, byrefType, byrefInfo);
+      }
+    }
+    llvm_unreachable("fell out of lifetime switch!");
+  }
+
+  BlockFieldFlags flags;
+  if (type->isBlockPointerType()) {
+    flags |= BLOCK_FIELD_IS_BLOCK;
+  } else if (CGM.getContext().isObjCNSObjectType(type) || 
+             type->isObjCObjectPointerType()) {
+    flags |= BLOCK_FIELD_IS_OBJECT;
+  } else {
+    return 0;
+  }
+
+  if (type.isObjCGCWeak())
+    flags |= BLOCK_FIELD_IS_WEAK;
+
+  ObjectByrefHelpers byrefInfo(emission.Alignment, flags);
+  return ::buildByrefHelpers(CGM, byrefType, byrefInfo);
+}
+
+unsigned CodeGenFunction::getByRefValueLLVMField(const ValueDecl *VD) const {
+  assert(ByRefValueInfo.count(VD) && "Did not find value!");
+  
+  return ByRefValueInfo.find(VD)->second.second;
+}
+
+llvm::Value *CodeGenFunction::BuildBlockByrefAddress(llvm::Value *BaseAddr,
+                                                     const VarDecl *V) {
+  llvm::Value *Loc = Builder.CreateStructGEP(BaseAddr, 1, "forwarding");
+  Loc = Builder.CreateLoad(Loc);
+  Loc = Builder.CreateStructGEP(Loc, getByRefValueLLVMField(V),
+                                V->getNameAsString());
+  return Loc;
+}
+
+/// BuildByRefType - 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
+///        char padding[X];           // only if needed
+///        T x;
+///      } x
+///
+llvm::Type *CodeGenFunction::BuildByRefType(const VarDecl *D) {
+  std::pair<llvm::Type *, unsigned> &Info = ByRefValueInfo[D];
+  if (Info.first)
+    return Info.first;
+  
+  QualType Ty = D->getType();
+
+  SmallVector<llvm::Type *, 8> types;
+  
+  llvm::StructType *ByRefType =
+    llvm::StructType::create(getLLVMContext(),
+                             "struct.__block_byref_" + D->getNameAsString());
+  
+  // void *__isa;
+  types.push_back(Int8PtrTy);
+  
+  // void *__forwarding;
+  types.push_back(llvm::PointerType::getUnqual(ByRefType));
+  
+  // int32_t __flags;
+  types.push_back(Int32Ty);
+    
+  // int32_t __size;
+  types.push_back(Int32Ty);
+
+  bool HasCopyAndDispose =
+       (Ty->isObjCRetainableType()) || getContext().getBlockVarCopyInits(D);
+  if (HasCopyAndDispose) {
+    /// void *__copy_helper;
+    types.push_back(Int8PtrTy);
+    
+    /// void *__destroy_helper;
+    types.push_back(Int8PtrTy);
+  }
+
+  bool Packed = false;
+  CharUnits Align = getContext().getDeclAlign(D);
+  if (Align > getContext().toCharUnitsFromBits(Target.getPointerAlign(0))) {
+    // We have to insert padding.
+    
+    // The struct above has 2 32-bit integers.
+    unsigned CurrentOffsetInBytes = 4 * 2;
+    
+    // And either 2 or 4 pointers.
+    CurrentOffsetInBytes += (HasCopyAndDispose ? 4 : 2) *
+      CGM.getTargetData().getTypeAllocSize(Int8PtrTy);
+    
+    // Align the offset.
+    unsigned AlignedOffsetInBytes = 
+      llvm::RoundUpToAlignment(CurrentOffsetInBytes, Align.getQuantity());
+    
+    unsigned NumPaddingBytes = AlignedOffsetInBytes - CurrentOffsetInBytes;
+    if (NumPaddingBytes > 0) {
+      llvm::Type *Ty = Int8Ty;
+      // FIXME: We need a sema error for alignment larger than the minimum of
+      // the maximal stack alignment and the alignment of malloc on the system.
+      if (NumPaddingBytes > 1)
+        Ty = llvm::ArrayType::get(Ty, NumPaddingBytes);
+    
+      types.push_back(Ty);
+
+      // We want a packed struct.
+      Packed = true;
+    }
+  }
+
+  // T x;
+  types.push_back(ConvertTypeForMem(Ty));
+  
+  ByRefType->setBody(types, Packed);
+  
+  Info.first = ByRefType;
+  
+  Info.second = types.size() - 1;
+  
+  return Info.first;
+}
+
+/// 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.
+  llvm::Value *addr = emission.Address;
+
+  // That's an alloca of the byref structure type.
+  llvm::StructType *byrefType = cast<llvm::StructType>(
+                 cast<llvm::PointerType>(addr->getType())->getElementType());
+
+  // Build the byref helpers if necessary.  This is null if we don't need any.
+  CodeGenModule::ByrefHelpers *helpers =
+    buildByrefHelpers(*byrefType, emission);
+
+  const VarDecl &D = *emission.Variable;
+  QualType type = D.getType();
+
+  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");
+  Builder.CreateStore(V, Builder.CreateStructGEP(addr, 0, "byref.isa"));
+
+  // Store the address of the variable into its own forwarding pointer.
+  Builder.CreateStore(addr,
+                      Builder.CreateStructGEP(addr, 1, "byref.forwarding"));
+
+  // Blocks ABI:
+  //   c) the flags field is set to either 0 if no helper functions are
+  //      needed or BLOCK_HAS_COPY_DISPOSE if they are,
+  BlockFlags flags;
+  if (helpers) flags |= BLOCK_HAS_COPY_DISPOSE;
+  Builder.CreateStore(llvm::ConstantInt::get(IntTy, flags.getBitMask()),
+                      Builder.CreateStructGEP(addr, 2, "byref.flags"));
+
+  CharUnits byrefSize = CGM.GetTargetTypeStoreSize(byrefType);
+  V = llvm::ConstantInt::get(IntTy, byrefSize.getQuantity());
+  Builder.CreateStore(V, Builder.CreateStructGEP(addr, 3, "byref.size"));
+
+  if (helpers) {
+    llvm::Value *copy_helper = Builder.CreateStructGEP(addr, 4);
+    Builder.CreateStore(helpers->CopyHelper, copy_helper);
+
+    llvm::Value *destroy_helper = Builder.CreateStructGEP(addr, 5);
+    Builder.CreateStore(helpers->DisposeHelper, destroy_helper);
+  }
+}
+
+void CodeGenFunction::BuildBlockRelease(llvm::Value *V, BlockFieldFlags flags) {
+  llvm::Value *F = CGM.getBlockObjectDispose();
+  llvm::Value *N;
+  V = Builder.CreateBitCast(V, Int8PtrTy);
+  N = llvm::ConstantInt::get(Int32Ty, flags.getBitMask());
+  Builder.CreateCall2(F, V, N);
+}
+
+namespace {
+  struct CallBlockRelease : EHScopeStack::Cleanup {
+    llvm::Value *Addr;
+    CallBlockRelease(llvm::Value *Addr) : Addr(Addr) {}
+
+    void Emit(CodeGenFunction &CGF, Flags flags) {
+      // Should we be passing FIELD_IS_WEAK here?
+      CGF.BuildBlockRelease(Addr, BLOCK_FIELD_IS_BYREF);
+    }
+  };
+}
+
+/// 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)
+    return;
+
+  EHStack.pushCleanup<CallBlockRelease>(NormalAndEHCleanup, emission.Address);
+}
+
+/// Adjust the declaration of something from the blocks API.
+static void configureBlocksRuntimeObject(CodeGenModule &CGM,
+                                         llvm::Constant *C) {
+  if (!CGM.getLangOpts().BlocksRuntimeOptional) return;
+
+  llvm::GlobalValue *GV = cast<llvm::GlobalValue>(C->stripPointerCasts());
+  if (GV->isDeclaration() &&
+      GV->getLinkage() == llvm::GlobalValue::ExternalLinkage)
+    GV->setLinkage(llvm::GlobalValue::ExternalWeakLinkage);
+}
+
+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",
+                                                Int8PtrTy->getPointerTo(), 0);
+  configureBlocksRuntimeObject(*this, NSConcreteGlobalBlock);
+  return NSConcreteGlobalBlock;
+}
+
+llvm::Constant *CodeGenModule::getNSConcreteStackBlock() {
+  if (NSConcreteStackBlock)
+    return NSConcreteStackBlock;
+
+  NSConcreteStackBlock = GetOrCreateLLVMGlobal("_NSConcreteStackBlock",
+                                               Int8PtrTy->getPointerTo(), 0);
+  configureBlocksRuntimeObject(*this, NSConcreteStackBlock);
+  return NSConcreteStackBlock;  
+}