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1 //===--- CGBlocks.cpp - Emit LLVM Code for declarations ---------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This contains code to emit blocks.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "CGBlocks.h"
15 #include "CGDebugInfo.h"
16 #include "CGObjCRuntime.h"
17 #include "CodeGenFunction.h"
18 #include "CodeGenModule.h"
19 #include "clang/AST/DeclObjC.h"
20 #include "llvm/ADT/SmallSet.h"
21 #include "llvm/IR/CallSite.h"
22 #include "llvm/IR/DataLayout.h"
23 #include "llvm/IR/Module.h"
24 #include <algorithm>
25 #include <cstdio>
26 
27 using namespace clang;
28 using namespace CodeGen;
29 
CGBlockInfo(const BlockDecl * block,StringRef name)30 CGBlockInfo::CGBlockInfo(const BlockDecl *block, StringRef name)
31   : Name(name), CXXThisIndex(0), CanBeGlobal(false), NeedsCopyDispose(false),
32     HasCXXObject(false), UsesStret(false), HasCapturedVariableLayout(false),
33     LocalAddress(Address::invalid()), StructureType(nullptr), Block(block),
34     DominatingIP(nullptr) {
35 
36   // Skip asm prefix, if any.  'name' is usually taken directly from
37   // the mangled name of the enclosing function.
38   if (!name.empty() && name[0] == '\01')
39     name = name.substr(1);
40 }
41 
42 // Anchor the vtable to this translation unit.
~BlockByrefHelpers()43 BlockByrefHelpers::~BlockByrefHelpers() {}
44 
45 /// Build the given block as a global block.
46 static llvm::Constant *buildGlobalBlock(CodeGenModule &CGM,
47                                         const CGBlockInfo &blockInfo,
48                                         llvm::Constant *blockFn);
49 
50 /// Build the helper function to copy a block.
buildCopyHelper(CodeGenModule & CGM,const CGBlockInfo & blockInfo)51 static llvm::Constant *buildCopyHelper(CodeGenModule &CGM,
52                                        const CGBlockInfo &blockInfo) {
53   return CodeGenFunction(CGM).GenerateCopyHelperFunction(blockInfo);
54 }
55 
56 /// Build the helper function to dispose of a block.
buildDisposeHelper(CodeGenModule & CGM,const CGBlockInfo & blockInfo)57 static llvm::Constant *buildDisposeHelper(CodeGenModule &CGM,
58                                           const CGBlockInfo &blockInfo) {
59   return CodeGenFunction(CGM).GenerateDestroyHelperFunction(blockInfo);
60 }
61 
62 /// buildBlockDescriptor - Build the block descriptor meta-data for a block.
63 /// buildBlockDescriptor is accessed from 5th field of the Block_literal
64 /// meta-data and contains stationary information about the block literal.
65 /// Its definition will have 4 (or optinally 6) words.
66 /// \code
67 /// struct Block_descriptor {
68 ///   unsigned long reserved;
69 ///   unsigned long size;  // size of Block_literal metadata in bytes.
70 ///   void *copy_func_helper_decl;  // optional copy helper.
71 ///   void *destroy_func_decl; // optioanl destructor helper.
72 ///   void *block_method_encoding_address; // @encode for block literal signature.
73 ///   void *block_layout_info; // encoding of captured block variables.
74 /// };
75 /// \endcode
buildBlockDescriptor(CodeGenModule & CGM,const CGBlockInfo & blockInfo)76 static llvm::Constant *buildBlockDescriptor(CodeGenModule &CGM,
77                                             const CGBlockInfo &blockInfo) {
78   ASTContext &C = CGM.getContext();
79 
80   llvm::Type *ulong = CGM.getTypes().ConvertType(C.UnsignedLongTy);
81   llvm::Type *i8p = nullptr;
82   if (CGM.getLangOpts().OpenCL)
83     i8p =
84       llvm::Type::getInt8PtrTy(
85            CGM.getLLVMContext(), C.getTargetAddressSpace(LangAS::opencl_constant));
86   else
87     i8p = CGM.getTypes().ConvertType(C.VoidPtrTy);
88 
89   SmallVector<llvm::Constant*, 6> elements;
90 
91   // reserved
92   elements.push_back(llvm::ConstantInt::get(ulong, 0));
93 
94   // Size
95   // FIXME: What is the right way to say this doesn't fit?  We should give
96   // a user diagnostic in that case.  Better fix would be to change the
97   // API to size_t.
98   elements.push_back(llvm::ConstantInt::get(ulong,
99                                             blockInfo.BlockSize.getQuantity()));
100 
101   // Optional copy/dispose helpers.
102   if (blockInfo.NeedsCopyDispose) {
103     // copy_func_helper_decl
104     elements.push_back(buildCopyHelper(CGM, blockInfo));
105 
106     // destroy_func_decl
107     elements.push_back(buildDisposeHelper(CGM, blockInfo));
108   }
109 
110   // Signature.  Mandatory ObjC-style method descriptor @encode sequence.
111   std::string typeAtEncoding =
112     CGM.getContext().getObjCEncodingForBlock(blockInfo.getBlockExpr());
113   elements.push_back(llvm::ConstantExpr::getBitCast(
114     CGM.GetAddrOfConstantCString(typeAtEncoding).getPointer(), i8p));
115 
116   // GC layout.
117   if (C.getLangOpts().ObjC1) {
118     if (CGM.getLangOpts().getGC() != LangOptions::NonGC)
119       elements.push_back(CGM.getObjCRuntime().BuildGCBlockLayout(CGM, blockInfo));
120     else
121       elements.push_back(CGM.getObjCRuntime().BuildRCBlockLayout(CGM, blockInfo));
122   }
123   else
124     elements.push_back(llvm::Constant::getNullValue(i8p));
125 
126   llvm::Constant *init = llvm::ConstantStruct::getAnon(elements);
127 
128   llvm::GlobalVariable *global =
129     new llvm::GlobalVariable(CGM.getModule(), init->getType(), true,
130                              llvm::GlobalValue::InternalLinkage,
131                              init, "__block_descriptor_tmp");
132 
133   return llvm::ConstantExpr::getBitCast(global, CGM.getBlockDescriptorType());
134 }
135 
136 /*
137   Purely notional variadic template describing the layout of a block.
138 
139   template <class _ResultType, class... _ParamTypes, class... _CaptureTypes>
140   struct Block_literal {
141     /// Initialized to one of:
142     ///   extern void *_NSConcreteStackBlock[];
143     ///   extern void *_NSConcreteGlobalBlock[];
144     ///
145     /// In theory, we could start one off malloc'ed by setting
146     /// BLOCK_NEEDS_FREE, giving it a refcount of 1, and using
147     /// this isa:
148     ///   extern void *_NSConcreteMallocBlock[];
149     struct objc_class *isa;
150 
151     /// These are the flags (with corresponding bit number) that the
152     /// compiler is actually supposed to know about.
153     ///  25. BLOCK_HAS_COPY_DISPOSE - indicates that the block
154     ///   descriptor provides copy and dispose helper functions
155     ///  26. BLOCK_HAS_CXX_OBJ - indicates that there's a captured
156     ///   object with a nontrivial destructor or copy constructor
157     ///  28. BLOCK_IS_GLOBAL - indicates that the block is allocated
158     ///   as global memory
159     ///  29. BLOCK_USE_STRET - indicates that the block function
160     ///   uses stret, which objc_msgSend needs to know about
161     ///  30. BLOCK_HAS_SIGNATURE - indicates that the block has an
162     ///   @encoded signature string
163     /// And we're not supposed to manipulate these:
164     ///  24. BLOCK_NEEDS_FREE - indicates that the block has been moved
165     ///   to malloc'ed memory
166     ///  27. BLOCK_IS_GC - indicates that the block has been moved to
167     ///   to GC-allocated memory
168     /// Additionally, the bottom 16 bits are a reference count which
169     /// should be zero on the stack.
170     int flags;
171 
172     /// Reserved;  should be zero-initialized.
173     int reserved;
174 
175     /// Function pointer generated from block literal.
176     _ResultType (*invoke)(Block_literal *, _ParamTypes...);
177 
178     /// Block description metadata generated from block literal.
179     struct Block_descriptor *block_descriptor;
180 
181     /// Captured values follow.
182     _CapturesTypes captures...;
183   };
184  */
185 
186 /// The number of fields in a block header.
187 const unsigned BlockHeaderSize = 5;
188 
189 namespace {
190   /// A chunk of data that we actually have to capture in the block.
191   struct BlockLayoutChunk {
192     CharUnits Alignment;
193     CharUnits Size;
194     Qualifiers::ObjCLifetime Lifetime;
195     const BlockDecl::Capture *Capture; // null for 'this'
196     llvm::Type *Type;
197 
BlockLayoutChunk__anon125376670111::BlockLayoutChunk198     BlockLayoutChunk(CharUnits align, CharUnits size,
199                      Qualifiers::ObjCLifetime lifetime,
200                      const BlockDecl::Capture *capture,
201                      llvm::Type *type)
202       : Alignment(align), Size(size), Lifetime(lifetime),
203         Capture(capture), Type(type) {}
204 
205     /// Tell the block info that this chunk has the given field index.
setIndex__anon125376670111::BlockLayoutChunk206     void setIndex(CGBlockInfo &info, unsigned index, CharUnits offset) {
207       if (!Capture) {
208         info.CXXThisIndex = index;
209         info.CXXThisOffset = offset;
210       } else {
211         info.Captures.insert({Capture->getVariable(),
212                               CGBlockInfo::Capture::makeIndex(index, offset)});
213       }
214     }
215   };
216 
217   /// Order by 1) all __strong together 2) next, all byfref together 3) next,
218   /// all __weak together. Preserve descending alignment in all situations.
operator <(const BlockLayoutChunk & left,const BlockLayoutChunk & right)219   bool operator<(const BlockLayoutChunk &left, const BlockLayoutChunk &right) {
220     if (left.Alignment != right.Alignment)
221       return left.Alignment > right.Alignment;
222 
223     auto getPrefOrder = [](const BlockLayoutChunk &chunk) {
224       if (chunk.Capture && chunk.Capture->isByRef())
225         return 1;
226       if (chunk.Lifetime == Qualifiers::OCL_Strong)
227         return 0;
228       if (chunk.Lifetime == Qualifiers::OCL_Weak)
229         return 2;
230       return 3;
231     };
232 
233     return getPrefOrder(left) < getPrefOrder(right);
234   }
235 } // end anonymous namespace
236 
237 /// Determines if the given type is safe for constant capture in C++.
isSafeForCXXConstantCapture(QualType type)238 static bool isSafeForCXXConstantCapture(QualType type) {
239   const RecordType *recordType =
240     type->getBaseElementTypeUnsafe()->getAs<RecordType>();
241 
242   // Only records can be unsafe.
243   if (!recordType) return true;
244 
245   const auto *record = cast<CXXRecordDecl>(recordType->getDecl());
246 
247   // Maintain semantics for classes with non-trivial dtors or copy ctors.
248   if (!record->hasTrivialDestructor()) return false;
249   if (record->hasNonTrivialCopyConstructor()) return false;
250 
251   // Otherwise, we just have to make sure there aren't any mutable
252   // fields that might have changed since initialization.
253   return !record->hasMutableFields();
254 }
255 
256 /// It is illegal to modify a const object after initialization.
257 /// Therefore, if a const object has a constant initializer, we don't
258 /// actually need to keep storage for it in the block; we'll just
259 /// rematerialize it at the start of the block function.  This is
260 /// acceptable because we make no promises about address stability of
261 /// captured variables.
tryCaptureAsConstant(CodeGenModule & CGM,CodeGenFunction * CGF,const VarDecl * var)262 static llvm::Constant *tryCaptureAsConstant(CodeGenModule &CGM,
263                                             CodeGenFunction *CGF,
264                                             const VarDecl *var) {
265   // Return if this is a function paramter. We shouldn't try to
266   // rematerialize default arguments of function parameters.
267   if (isa<ParmVarDecl>(var))
268     return nullptr;
269 
270   QualType type = var->getType();
271 
272   // We can only do this if the variable is const.
273   if (!type.isConstQualified()) return nullptr;
274 
275   // Furthermore, in C++ we have to worry about mutable fields:
276   // C++ [dcl.type.cv]p4:
277   //   Except that any class member declared mutable can be
278   //   modified, any attempt to modify a const object during its
279   //   lifetime results in undefined behavior.
280   if (CGM.getLangOpts().CPlusPlus && !isSafeForCXXConstantCapture(type))
281     return nullptr;
282 
283   // If the variable doesn't have any initializer (shouldn't this be
284   // invalid?), it's not clear what we should do.  Maybe capture as
285   // zero?
286   const Expr *init = var->getInit();
287   if (!init) return nullptr;
288 
289   return CGM.EmitConstantInit(*var, CGF);
290 }
291 
292 /// Get the low bit of a nonzero character count.  This is the
293 /// alignment of the nth byte if the 0th byte is universally aligned.
getLowBit(CharUnits v)294 static CharUnits getLowBit(CharUnits v) {
295   return CharUnits::fromQuantity(v.getQuantity() & (~v.getQuantity() + 1));
296 }
297 
initializeForBlockHeader(CodeGenModule & CGM,CGBlockInfo & info,SmallVectorImpl<llvm::Type * > & elementTypes)298 static void initializeForBlockHeader(CodeGenModule &CGM, CGBlockInfo &info,
299                              SmallVectorImpl<llvm::Type*> &elementTypes) {
300   // The header is basically 'struct { void *; int; int; void *; void *; }'.
301   // Assert that that struct is packed.
302   assert(CGM.getIntSize() <= CGM.getPointerSize());
303   assert(CGM.getIntAlign() <= CGM.getPointerAlign());
304   assert((2 * CGM.getIntSize()).isMultipleOf(CGM.getPointerAlign()));
305 
306   info.BlockAlign = CGM.getPointerAlign();
307   info.BlockSize = 3 * CGM.getPointerSize() + 2 * CGM.getIntSize();
308 
309   assert(elementTypes.empty());
310   elementTypes.push_back(CGM.VoidPtrTy);
311   elementTypes.push_back(CGM.IntTy);
312   elementTypes.push_back(CGM.IntTy);
313   elementTypes.push_back(CGM.VoidPtrTy);
314   elementTypes.push_back(CGM.getBlockDescriptorType());
315 
316   assert(elementTypes.size() == BlockHeaderSize);
317 }
318 
319 /// Compute the layout of the given block.  Attempts to lay the block
320 /// out with minimal space requirements.
computeBlockInfo(CodeGenModule & CGM,CodeGenFunction * CGF,CGBlockInfo & info)321 static void computeBlockInfo(CodeGenModule &CGM, CodeGenFunction *CGF,
322                              CGBlockInfo &info) {
323   ASTContext &C = CGM.getContext();
324   const BlockDecl *block = info.getBlockDecl();
325 
326   SmallVector<llvm::Type*, 8> elementTypes;
327   initializeForBlockHeader(CGM, info, elementTypes);
328 
329   if (!block->hasCaptures()) {
330     info.StructureType =
331       llvm::StructType::get(CGM.getLLVMContext(), elementTypes, true);
332     info.CanBeGlobal = true;
333     return;
334   }
335   else if (C.getLangOpts().ObjC1 &&
336            CGM.getLangOpts().getGC() == LangOptions::NonGC)
337     info.HasCapturedVariableLayout = true;
338 
339   // Collect the layout chunks.
340   SmallVector<BlockLayoutChunk, 16> layout;
341   layout.reserve(block->capturesCXXThis() +
342                  (block->capture_end() - block->capture_begin()));
343 
344   CharUnits maxFieldAlign;
345 
346   // First, 'this'.
347   if (block->capturesCXXThis()) {
348     assert(CGF && CGF->CurFuncDecl && isa<CXXMethodDecl>(CGF->CurFuncDecl) &&
349            "Can't capture 'this' outside a method");
350     QualType thisType = cast<CXXMethodDecl>(CGF->CurFuncDecl)->getThisType(C);
351 
352     // Theoretically, this could be in a different address space, so
353     // don't assume standard pointer size/align.
354     llvm::Type *llvmType = CGM.getTypes().ConvertType(thisType);
355     std::pair<CharUnits,CharUnits> tinfo
356       = CGM.getContext().getTypeInfoInChars(thisType);
357     maxFieldAlign = std::max(maxFieldAlign, tinfo.second);
358 
359     layout.push_back(BlockLayoutChunk(tinfo.second, tinfo.first,
360                                       Qualifiers::OCL_None,
361                                       nullptr, llvmType));
362   }
363 
364   // Next, all the block captures.
365   for (const auto &CI : block->captures()) {
366     const VarDecl *variable = CI.getVariable();
367 
368     if (CI.isByRef()) {
369       // We have to copy/dispose of the __block reference.
370       info.NeedsCopyDispose = true;
371 
372       // Just use void* instead of a pointer to the byref type.
373       CharUnits align = CGM.getPointerAlign();
374       maxFieldAlign = std::max(maxFieldAlign, align);
375 
376       layout.push_back(BlockLayoutChunk(align, CGM.getPointerSize(),
377                                         Qualifiers::OCL_None, &CI,
378                                         CGM.VoidPtrTy));
379       continue;
380     }
381 
382     // Otherwise, build a layout chunk with the size and alignment of
383     // the declaration.
384     if (llvm::Constant *constant = tryCaptureAsConstant(CGM, CGF, variable)) {
385       info.Captures[variable] = CGBlockInfo::Capture::makeConstant(constant);
386       continue;
387     }
388 
389     // If we have a lifetime qualifier, honor it for capture purposes.
390     // That includes *not* copying it if it's __unsafe_unretained.
391     Qualifiers::ObjCLifetime lifetime =
392       variable->getType().getObjCLifetime();
393     if (lifetime) {
394       switch (lifetime) {
395       case Qualifiers::OCL_None: llvm_unreachable("impossible");
396       case Qualifiers::OCL_ExplicitNone:
397       case Qualifiers::OCL_Autoreleasing:
398         break;
399 
400       case Qualifiers::OCL_Strong:
401       case Qualifiers::OCL_Weak:
402         info.NeedsCopyDispose = true;
403       }
404 
405     // Block pointers require copy/dispose.  So do Objective-C pointers.
406     } else if (variable->getType()->isObjCRetainableType()) {
407       // But honor the inert __unsafe_unretained qualifier, which doesn't
408       // actually make it into the type system.
409        if (variable->getType()->isObjCInertUnsafeUnretainedType()) {
410         lifetime = Qualifiers::OCL_ExplicitNone;
411       } else {
412         info.NeedsCopyDispose = true;
413         // used for mrr below.
414         lifetime = Qualifiers::OCL_Strong;
415       }
416 
417     // So do types that require non-trivial copy construction.
418     } else if (CI.hasCopyExpr()) {
419       info.NeedsCopyDispose = true;
420       info.HasCXXObject = true;
421 
422     // And so do types with destructors.
423     } else if (CGM.getLangOpts().CPlusPlus) {
424       if (const CXXRecordDecl *record =
425             variable->getType()->getAsCXXRecordDecl()) {
426         if (!record->hasTrivialDestructor()) {
427           info.HasCXXObject = true;
428           info.NeedsCopyDispose = true;
429         }
430       }
431     }
432 
433     QualType VT = variable->getType();
434     CharUnits size = C.getTypeSizeInChars(VT);
435     CharUnits align = C.getDeclAlign(variable);
436 
437     maxFieldAlign = std::max(maxFieldAlign, align);
438 
439     llvm::Type *llvmType =
440       CGM.getTypes().ConvertTypeForMem(VT);
441 
442     layout.push_back(BlockLayoutChunk(align, size, lifetime, &CI, llvmType));
443   }
444 
445   // If that was everything, we're done here.
446   if (layout.empty()) {
447     info.StructureType =
448       llvm::StructType::get(CGM.getLLVMContext(), elementTypes, true);
449     info.CanBeGlobal = true;
450     return;
451   }
452 
453   // Sort the layout by alignment.  We have to use a stable sort here
454   // to get reproducible results.  There should probably be an
455   // llvm::array_pod_stable_sort.
456   std::stable_sort(layout.begin(), layout.end());
457 
458   // Needed for blocks layout info.
459   info.BlockHeaderForcedGapOffset = info.BlockSize;
460   info.BlockHeaderForcedGapSize = CharUnits::Zero();
461 
462   CharUnits &blockSize = info.BlockSize;
463   info.BlockAlign = std::max(maxFieldAlign, info.BlockAlign);
464 
465   // Assuming that the first byte in the header is maximally aligned,
466   // get the alignment of the first byte following the header.
467   CharUnits endAlign = getLowBit(blockSize);
468 
469   // If the end of the header isn't satisfactorily aligned for the
470   // maximum thing, look for things that are okay with the header-end
471   // alignment, and keep appending them until we get something that's
472   // aligned right.  This algorithm is only guaranteed optimal if
473   // that condition is satisfied at some point; otherwise we can get
474   // things like:
475   //   header                 // next byte has alignment 4
476   //   something_with_size_5; // next byte has alignment 1
477   //   something_with_alignment_8;
478   // which has 7 bytes of padding, as opposed to the naive solution
479   // which might have less (?).
480   if (endAlign < maxFieldAlign) {
481     SmallVectorImpl<BlockLayoutChunk>::iterator
482       li = layout.begin() + 1, le = layout.end();
483 
484     // Look for something that the header end is already
485     // satisfactorily aligned for.
486     for (; li != le && endAlign < li->Alignment; ++li)
487       ;
488 
489     // If we found something that's naturally aligned for the end of
490     // the header, keep adding things...
491     if (li != le) {
492       SmallVectorImpl<BlockLayoutChunk>::iterator first = li;
493       for (; li != le; ++li) {
494         assert(endAlign >= li->Alignment);
495 
496         li->setIndex(info, elementTypes.size(), blockSize);
497         elementTypes.push_back(li->Type);
498         blockSize += li->Size;
499         endAlign = getLowBit(blockSize);
500 
501         // ...until we get to the alignment of the maximum field.
502         if (endAlign >= maxFieldAlign) {
503           break;
504         }
505       }
506       // Don't re-append everything we just appended.
507       layout.erase(first, li);
508     }
509   }
510 
511   assert(endAlign == getLowBit(blockSize));
512 
513   // At this point, we just have to add padding if the end align still
514   // isn't aligned right.
515   if (endAlign < maxFieldAlign) {
516     CharUnits newBlockSize = blockSize.alignTo(maxFieldAlign);
517     CharUnits padding = newBlockSize - blockSize;
518 
519     // If we haven't yet added any fields, remember that there was an
520     // initial gap; this need to go into the block layout bit map.
521     if (blockSize == info.BlockHeaderForcedGapOffset) {
522       info.BlockHeaderForcedGapSize = padding;
523     }
524 
525     elementTypes.push_back(llvm::ArrayType::get(CGM.Int8Ty,
526                                                 padding.getQuantity()));
527     blockSize = newBlockSize;
528     endAlign = getLowBit(blockSize); // might be > maxFieldAlign
529   }
530 
531   assert(endAlign >= maxFieldAlign);
532   assert(endAlign == getLowBit(blockSize));
533   // Slam everything else on now.  This works because they have
534   // strictly decreasing alignment and we expect that size is always a
535   // multiple of alignment.
536   for (SmallVectorImpl<BlockLayoutChunk>::iterator
537          li = layout.begin(), le = layout.end(); li != le; ++li) {
538     if (endAlign < li->Alignment) {
539       // size may not be multiple of alignment. This can only happen with
540       // an over-aligned variable. We will be adding a padding field to
541       // make the size be multiple of alignment.
542       CharUnits padding = li->Alignment - endAlign;
543       elementTypes.push_back(llvm::ArrayType::get(CGM.Int8Ty,
544                                                   padding.getQuantity()));
545       blockSize += padding;
546       endAlign = getLowBit(blockSize);
547     }
548     assert(endAlign >= li->Alignment);
549     li->setIndex(info, elementTypes.size(), blockSize);
550     elementTypes.push_back(li->Type);
551     blockSize += li->Size;
552     endAlign = getLowBit(blockSize);
553   }
554 
555   info.StructureType =
556     llvm::StructType::get(CGM.getLLVMContext(), elementTypes, true);
557 }
558 
559 /// Enter the scope of a block.  This should be run at the entrance to
560 /// a full-expression so that the block's cleanups are pushed at the
561 /// right place in the stack.
enterBlockScope(CodeGenFunction & CGF,BlockDecl * block)562 static void enterBlockScope(CodeGenFunction &CGF, BlockDecl *block) {
563   assert(CGF.HaveInsertPoint());
564 
565   // Allocate the block info and place it at the head of the list.
566   CGBlockInfo &blockInfo =
567     *new CGBlockInfo(block, CGF.CurFn->getName());
568   blockInfo.NextBlockInfo = CGF.FirstBlockInfo;
569   CGF.FirstBlockInfo = &blockInfo;
570 
571   // Compute information about the layout, etc., of this block,
572   // pushing cleanups as necessary.
573   computeBlockInfo(CGF.CGM, &CGF, blockInfo);
574 
575   // Nothing else to do if it can be global.
576   if (blockInfo.CanBeGlobal) return;
577 
578   // Make the allocation for the block.
579   blockInfo.LocalAddress = CGF.CreateTempAlloca(blockInfo.StructureType,
580                                                 blockInfo.BlockAlign, "block");
581 
582   // If there are cleanups to emit, enter them (but inactive).
583   if (!blockInfo.NeedsCopyDispose) return;
584 
585   // Walk through the captures (in order) and find the ones not
586   // captured by constant.
587   for (const auto &CI : block->captures()) {
588     // Ignore __block captures; there's nothing special in the
589     // on-stack block that we need to do for them.
590     if (CI.isByRef()) continue;
591 
592     // Ignore variables that are constant-captured.
593     const VarDecl *variable = CI.getVariable();
594     CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
595     if (capture.isConstant()) continue;
596 
597     // Ignore objects that aren't destructed.
598     QualType::DestructionKind dtorKind =
599       variable->getType().isDestructedType();
600     if (dtorKind == QualType::DK_none) continue;
601 
602     CodeGenFunction::Destroyer *destroyer;
603 
604     // Block captures count as local values and have imprecise semantics.
605     // They also can't be arrays, so need to worry about that.
606     if (dtorKind == QualType::DK_objc_strong_lifetime) {
607       destroyer = CodeGenFunction::destroyARCStrongImprecise;
608     } else {
609       destroyer = CGF.getDestroyer(dtorKind);
610     }
611 
612     // GEP down to the address.
613     Address addr = CGF.Builder.CreateStructGEP(blockInfo.LocalAddress,
614                                                capture.getIndex(),
615                                                capture.getOffset());
616 
617     // We can use that GEP as the dominating IP.
618     if (!blockInfo.DominatingIP)
619       blockInfo.DominatingIP = cast<llvm::Instruction>(addr.getPointer());
620 
621     CleanupKind cleanupKind = InactiveNormalCleanup;
622     bool useArrayEHCleanup = CGF.needsEHCleanup(dtorKind);
623     if (useArrayEHCleanup)
624       cleanupKind = InactiveNormalAndEHCleanup;
625 
626     CGF.pushDestroy(cleanupKind, addr, variable->getType(),
627                     destroyer, useArrayEHCleanup);
628 
629     // Remember where that cleanup was.
630     capture.setCleanup(CGF.EHStack.stable_begin());
631   }
632 }
633 
634 /// Enter a full-expression with a non-trivial number of objects to
635 /// clean up.  This is in this file because, at the moment, the only
636 /// kind of cleanup object is a BlockDecl*.
enterNonTrivialFullExpression(const ExprWithCleanups * E)637 void CodeGenFunction::enterNonTrivialFullExpression(const ExprWithCleanups *E) {
638   assert(E->getNumObjects() != 0);
639   ArrayRef<ExprWithCleanups::CleanupObject> cleanups = E->getObjects();
640   for (ArrayRef<ExprWithCleanups::CleanupObject>::iterator
641          i = cleanups.begin(), e = cleanups.end(); i != e; ++i) {
642     enterBlockScope(*this, *i);
643   }
644 }
645 
646 /// Find the layout for the given block in a linked list and remove it.
findAndRemoveBlockInfo(CGBlockInfo ** head,const BlockDecl * block)647 static CGBlockInfo *findAndRemoveBlockInfo(CGBlockInfo **head,
648                                            const BlockDecl *block) {
649   while (true) {
650     assert(head && *head);
651     CGBlockInfo *cur = *head;
652 
653     // If this is the block we're looking for, splice it out of the list.
654     if (cur->getBlockDecl() == block) {
655       *head = cur->NextBlockInfo;
656       return cur;
657     }
658 
659     head = &cur->NextBlockInfo;
660   }
661 }
662 
663 /// Destroy a chain of block layouts.
destroyBlockInfos(CGBlockInfo * head)664 void CodeGenFunction::destroyBlockInfos(CGBlockInfo *head) {
665   assert(head && "destroying an empty chain");
666   do {
667     CGBlockInfo *cur = head;
668     head = cur->NextBlockInfo;
669     delete cur;
670   } while (head != nullptr);
671 }
672 
673 /// Emit a block literal expression in the current function.
EmitBlockLiteral(const BlockExpr * blockExpr)674 llvm::Value *CodeGenFunction::EmitBlockLiteral(const BlockExpr *blockExpr) {
675   // If the block has no captures, we won't have a pre-computed
676   // layout for it.
677   if (!blockExpr->getBlockDecl()->hasCaptures()) {
678     CGBlockInfo blockInfo(blockExpr->getBlockDecl(), CurFn->getName());
679     computeBlockInfo(CGM, this, blockInfo);
680     blockInfo.BlockExpression = blockExpr;
681     return EmitBlockLiteral(blockInfo);
682   }
683 
684   // Find the block info for this block and take ownership of it.
685   std::unique_ptr<CGBlockInfo> blockInfo;
686   blockInfo.reset(findAndRemoveBlockInfo(&FirstBlockInfo,
687                                          blockExpr->getBlockDecl()));
688 
689   blockInfo->BlockExpression = blockExpr;
690   return EmitBlockLiteral(*blockInfo);
691 }
692 
EmitBlockLiteral(const CGBlockInfo & blockInfo)693 llvm::Value *CodeGenFunction::EmitBlockLiteral(const CGBlockInfo &blockInfo) {
694   // Using the computed layout, generate the actual block function.
695   bool isLambdaConv = blockInfo.getBlockDecl()->isConversionFromLambda();
696   llvm::Constant *blockFn
697     = CodeGenFunction(CGM, true).GenerateBlockFunction(CurGD, blockInfo,
698                                                        LocalDeclMap,
699                                                        isLambdaConv);
700   blockFn = llvm::ConstantExpr::getBitCast(blockFn, VoidPtrTy);
701 
702   // If there is nothing to capture, we can emit this as a global block.
703   if (blockInfo.CanBeGlobal)
704     return buildGlobalBlock(CGM, blockInfo, blockFn);
705 
706   // Otherwise, we have to emit this as a local block.
707 
708   llvm::Constant *isa = CGM.getNSConcreteStackBlock();
709   isa = llvm::ConstantExpr::getBitCast(isa, VoidPtrTy);
710 
711   // Build the block descriptor.
712   llvm::Constant *descriptor = buildBlockDescriptor(CGM, blockInfo);
713 
714   Address blockAddr = blockInfo.LocalAddress;
715   assert(blockAddr.isValid() && "block has no address!");
716 
717   // Compute the initial on-stack block flags.
718   BlockFlags flags = BLOCK_HAS_SIGNATURE;
719   if (blockInfo.HasCapturedVariableLayout) flags |= BLOCK_HAS_EXTENDED_LAYOUT;
720   if (blockInfo.NeedsCopyDispose) flags |= BLOCK_HAS_COPY_DISPOSE;
721   if (blockInfo.HasCXXObject) flags |= BLOCK_HAS_CXX_OBJ;
722   if (blockInfo.UsesStret) flags |= BLOCK_USE_STRET;
723 
724   auto projectField =
725     [&](unsigned index, CharUnits offset, const Twine &name) -> Address {
726       return Builder.CreateStructGEP(blockAddr, index, offset, name);
727     };
728   auto storeField =
729     [&](llvm::Value *value, unsigned index, CharUnits offset,
730         const Twine &name) {
731       Builder.CreateStore(value, projectField(index, offset, name));
732     };
733 
734   // Initialize the block header.
735   {
736     // We assume all the header fields are densely packed.
737     unsigned index = 0;
738     CharUnits offset;
739     auto addHeaderField =
740       [&](llvm::Value *value, CharUnits size, const Twine &name) {
741         storeField(value, index, offset, name);
742         offset += size;
743         index++;
744       };
745 
746     addHeaderField(isa, getPointerSize(), "block.isa");
747     addHeaderField(llvm::ConstantInt::get(IntTy, flags.getBitMask()),
748                    getIntSize(), "block.flags");
749     addHeaderField(llvm::ConstantInt::get(IntTy, 0),
750                    getIntSize(), "block.reserved");
751     addHeaderField(blockFn, getPointerSize(), "block.invoke");
752     addHeaderField(descriptor, getPointerSize(), "block.descriptor");
753   }
754 
755   // Finally, capture all the values into the block.
756   const BlockDecl *blockDecl = blockInfo.getBlockDecl();
757 
758   // First, 'this'.
759   if (blockDecl->capturesCXXThis()) {
760     Address addr = projectField(blockInfo.CXXThisIndex, blockInfo.CXXThisOffset,
761                                 "block.captured-this.addr");
762     Builder.CreateStore(LoadCXXThis(), addr);
763   }
764 
765   // Next, captured variables.
766   for (const auto &CI : blockDecl->captures()) {
767     const VarDecl *variable = CI.getVariable();
768     const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
769 
770     // Ignore constant captures.
771     if (capture.isConstant()) continue;
772 
773     QualType type = variable->getType();
774 
775     // This will be a [[type]]*, except that a byref entry will just be
776     // an i8**.
777     Address blockField =
778       projectField(capture.getIndex(), capture.getOffset(), "block.captured");
779 
780     // Compute the address of the thing we're going to move into the
781     // block literal.
782     Address src = Address::invalid();
783 
784     if (blockDecl->isConversionFromLambda()) {
785       // The lambda capture in a lambda's conversion-to-block-pointer is
786       // special; we'll simply emit it directly.
787       src = Address::invalid();
788     } else if (CI.isByRef()) {
789       if (BlockInfo && CI.isNested()) {
790         // We need to use the capture from the enclosing block.
791         const CGBlockInfo::Capture &enclosingCapture =
792             BlockInfo->getCapture(variable);
793 
794         // This is a [[type]]*, except that a byref entry wil just be an i8**.
795         src = Builder.CreateStructGEP(LoadBlockStruct(),
796                                       enclosingCapture.getIndex(),
797                                       enclosingCapture.getOffset(),
798                                       "block.capture.addr");
799       } else {
800         auto I = LocalDeclMap.find(variable);
801         assert(I != LocalDeclMap.end());
802         src = I->second;
803       }
804     } else {
805       DeclRefExpr declRef(const_cast<VarDecl *>(variable),
806                           /*RefersToEnclosingVariableOrCapture*/ CI.isNested(),
807                           type.getNonReferenceType(), VK_LValue,
808                           SourceLocation());
809       src = EmitDeclRefLValue(&declRef).getAddress();
810     };
811 
812     // For byrefs, we just write the pointer to the byref struct into
813     // the block field.  There's no need to chase the forwarding
814     // pointer at this point, since we're building something that will
815     // live a shorter life than the stack byref anyway.
816     if (CI.isByRef()) {
817       // Get a void* that points to the byref struct.
818       llvm::Value *byrefPointer;
819       if (CI.isNested())
820         byrefPointer = Builder.CreateLoad(src, "byref.capture");
821       else
822         byrefPointer = Builder.CreateBitCast(src.getPointer(), VoidPtrTy);
823 
824       // Write that void* into the capture field.
825       Builder.CreateStore(byrefPointer, blockField);
826 
827     // If we have a copy constructor, evaluate that into the block field.
828     } else if (const Expr *copyExpr = CI.getCopyExpr()) {
829       if (blockDecl->isConversionFromLambda()) {
830         // If we have a lambda conversion, emit the expression
831         // directly into the block instead.
832         AggValueSlot Slot =
833             AggValueSlot::forAddr(blockField, Qualifiers(),
834                                   AggValueSlot::IsDestructed,
835                                   AggValueSlot::DoesNotNeedGCBarriers,
836                                   AggValueSlot::IsNotAliased);
837         EmitAggExpr(copyExpr, Slot);
838       } else {
839         EmitSynthesizedCXXCopyCtor(blockField, src, copyExpr);
840       }
841 
842     // If it's a reference variable, copy the reference into the block field.
843     } else if (type->isReferenceType()) {
844       Builder.CreateStore(src.getPointer(), blockField);
845 
846     // If this is an ARC __strong block-pointer variable, don't do a
847     // block copy.
848     //
849     // TODO: this can be generalized into the normal initialization logic:
850     // we should never need to do a block-copy when initializing a local
851     // variable, because the local variable's lifetime should be strictly
852     // contained within the stack block's.
853     } else if (type.getObjCLifetime() == Qualifiers::OCL_Strong &&
854                type->isBlockPointerType()) {
855       // Load the block and do a simple retain.
856       llvm::Value *value = Builder.CreateLoad(src, "block.captured_block");
857       value = EmitARCRetainNonBlock(value);
858 
859       // Do a primitive store to the block field.
860       Builder.CreateStore(value, blockField);
861 
862     // Otherwise, fake up a POD copy into the block field.
863     } else {
864       // Fake up a new variable so that EmitScalarInit doesn't think
865       // we're referring to the variable in its own initializer.
866       ImplicitParamDecl blockFieldPseudoVar(getContext(), /*DC*/ nullptr,
867                                             SourceLocation(), /*name*/ nullptr,
868                                             type);
869 
870       // We use one of these or the other depending on whether the
871       // reference is nested.
872       DeclRefExpr declRef(const_cast<VarDecl *>(variable),
873                           /*RefersToEnclosingVariableOrCapture*/ CI.isNested(),
874                           type, VK_LValue, SourceLocation());
875 
876       ImplicitCastExpr l2r(ImplicitCastExpr::OnStack, type, CK_LValueToRValue,
877                            &declRef, VK_RValue);
878       // FIXME: Pass a specific location for the expr init so that the store is
879       // attributed to a reasonable location - otherwise it may be attributed to
880       // locations of subexpressions in the initialization.
881       EmitExprAsInit(&l2r, &blockFieldPseudoVar,
882                      MakeAddrLValue(blockField, type, AlignmentSource::Decl),
883                      /*captured by init*/ false);
884     }
885 
886     // Activate the cleanup if layout pushed one.
887     if (!CI.isByRef()) {
888       EHScopeStack::stable_iterator cleanup = capture.getCleanup();
889       if (cleanup.isValid())
890         ActivateCleanupBlock(cleanup, blockInfo.DominatingIP);
891     }
892   }
893 
894   // Cast to the converted block-pointer type, which happens (somewhat
895   // unfortunately) to be a pointer to function type.
896   llvm::Value *result =
897     Builder.CreateBitCast(blockAddr.getPointer(),
898                           ConvertType(blockInfo.getBlockExpr()->getType()));
899 
900   return result;
901 }
902 
903 
getBlockDescriptorType()904 llvm::Type *CodeGenModule::getBlockDescriptorType() {
905   if (BlockDescriptorType)
906     return BlockDescriptorType;
907 
908   llvm::Type *UnsignedLongTy =
909     getTypes().ConvertType(getContext().UnsignedLongTy);
910 
911   // struct __block_descriptor {
912   //   unsigned long reserved;
913   //   unsigned long block_size;
914   //
915   //   // later, the following will be added
916   //
917   //   struct {
918   //     void (*copyHelper)();
919   //     void (*copyHelper)();
920   //   } helpers;                // !!! optional
921   //
922   //   const char *signature;   // the block signature
923   //   const char *layout;      // reserved
924   // };
925   BlockDescriptorType =
926     llvm::StructType::create("struct.__block_descriptor",
927                              UnsignedLongTy, UnsignedLongTy, nullptr);
928 
929   // Now form a pointer to that.
930   BlockDescriptorType = llvm::PointerType::getUnqual(BlockDescriptorType);
931   return BlockDescriptorType;
932 }
933 
getGenericBlockLiteralType()934 llvm::Type *CodeGenModule::getGenericBlockLiteralType() {
935   if (GenericBlockLiteralType)
936     return GenericBlockLiteralType;
937 
938   llvm::Type *BlockDescPtrTy = getBlockDescriptorType();
939 
940   // struct __block_literal_generic {
941   //   void *__isa;
942   //   int __flags;
943   //   int __reserved;
944   //   void (*__invoke)(void *);
945   //   struct __block_descriptor *__descriptor;
946   // };
947   GenericBlockLiteralType =
948     llvm::StructType::create("struct.__block_literal_generic",
949                              VoidPtrTy, IntTy, IntTy, VoidPtrTy,
950                              BlockDescPtrTy, nullptr);
951 
952   return GenericBlockLiteralType;
953 }
954 
EmitBlockCallExpr(const CallExpr * E,ReturnValueSlot ReturnValue)955 RValue CodeGenFunction::EmitBlockCallExpr(const CallExpr *E,
956                                           ReturnValueSlot ReturnValue) {
957   const BlockPointerType *BPT =
958     E->getCallee()->getType()->getAs<BlockPointerType>();
959 
960   llvm::Value *Callee = EmitScalarExpr(E->getCallee());
961 
962   // Get a pointer to the generic block literal.
963   llvm::Type *BlockLiteralTy =
964     llvm::PointerType::getUnqual(CGM.getGenericBlockLiteralType());
965 
966   // Bitcast the callee to a block literal.
967   llvm::Value *BlockLiteral =
968     Builder.CreateBitCast(Callee, BlockLiteralTy, "block.literal");
969 
970   // Get the function pointer from the literal.
971   llvm::Value *FuncPtr =
972     Builder.CreateStructGEP(CGM.getGenericBlockLiteralType(), BlockLiteral, 3);
973 
974   BlockLiteral = Builder.CreateBitCast(BlockLiteral, VoidPtrTy);
975 
976   // Add the block literal.
977   CallArgList Args;
978   Args.add(RValue::get(BlockLiteral), getContext().VoidPtrTy);
979 
980   QualType FnType = BPT->getPointeeType();
981 
982   // And the rest of the arguments.
983   EmitCallArgs(Args, FnType->getAs<FunctionProtoType>(), E->arguments());
984 
985   // Load the function.
986   llvm::Value *Func = Builder.CreateAlignedLoad(FuncPtr, getPointerAlign());
987 
988   const FunctionType *FuncTy = FnType->castAs<FunctionType>();
989   const CGFunctionInfo &FnInfo =
990     CGM.getTypes().arrangeBlockFunctionCall(Args, FuncTy);
991 
992   // Cast the function pointer to the right type.
993   llvm::Type *BlockFTy = CGM.getTypes().GetFunctionType(FnInfo);
994 
995   llvm::Type *BlockFTyPtr = llvm::PointerType::getUnqual(BlockFTy);
996   Func = Builder.CreateBitCast(Func, BlockFTyPtr);
997 
998   // And call the block.
999   return EmitCall(FnInfo, Func, ReturnValue, Args);
1000 }
1001 
GetAddrOfBlockDecl(const VarDecl * variable,bool isByRef)1002 Address CodeGenFunction::GetAddrOfBlockDecl(const VarDecl *variable,
1003                                             bool isByRef) {
1004   assert(BlockInfo && "evaluating block ref without block information?");
1005   const CGBlockInfo::Capture &capture = BlockInfo->getCapture(variable);
1006 
1007   // Handle constant captures.
1008   if (capture.isConstant()) return LocalDeclMap.find(variable)->second;
1009 
1010   Address addr =
1011     Builder.CreateStructGEP(LoadBlockStruct(), capture.getIndex(),
1012                             capture.getOffset(), "block.capture.addr");
1013 
1014   if (isByRef) {
1015     // addr should be a void** right now.  Load, then cast the result
1016     // to byref*.
1017 
1018     auto &byrefInfo = getBlockByrefInfo(variable);
1019     addr = Address(Builder.CreateLoad(addr), byrefInfo.ByrefAlignment);
1020 
1021     auto byrefPointerType = llvm::PointerType::get(byrefInfo.Type, 0);
1022     addr = Builder.CreateBitCast(addr, byrefPointerType, "byref.addr");
1023 
1024     addr = emitBlockByrefAddress(addr, byrefInfo, /*follow*/ true,
1025                                  variable->getName());
1026   }
1027 
1028   if (auto refType = variable->getType()->getAs<ReferenceType>()) {
1029     addr = EmitLoadOfReference(addr, refType);
1030   }
1031 
1032   return addr;
1033 }
1034 
1035 llvm::Constant *
GetAddrOfGlobalBlock(const BlockExpr * blockExpr,const char * name)1036 CodeGenModule::GetAddrOfGlobalBlock(const BlockExpr *blockExpr,
1037                                     const char *name) {
1038   CGBlockInfo blockInfo(blockExpr->getBlockDecl(), name);
1039   blockInfo.BlockExpression = blockExpr;
1040 
1041   // Compute information about the layout, etc., of this block.
1042   computeBlockInfo(*this, nullptr, blockInfo);
1043 
1044   // Using that metadata, generate the actual block function.
1045   llvm::Constant *blockFn;
1046   {
1047     CodeGenFunction::DeclMapTy LocalDeclMap;
1048     blockFn = CodeGenFunction(*this).GenerateBlockFunction(GlobalDecl(),
1049                                                            blockInfo,
1050                                                            LocalDeclMap,
1051                                                            false);
1052   }
1053   blockFn = llvm::ConstantExpr::getBitCast(blockFn, VoidPtrTy);
1054 
1055   return buildGlobalBlock(*this, blockInfo, blockFn);
1056 }
1057 
buildGlobalBlock(CodeGenModule & CGM,const CGBlockInfo & blockInfo,llvm::Constant * blockFn)1058 static llvm::Constant *buildGlobalBlock(CodeGenModule &CGM,
1059                                         const CGBlockInfo &blockInfo,
1060                                         llvm::Constant *blockFn) {
1061   assert(blockInfo.CanBeGlobal);
1062 
1063   // Generate the constants for the block literal initializer.
1064   llvm::Constant *fields[BlockHeaderSize];
1065 
1066   // isa
1067   fields[0] = CGM.getNSConcreteGlobalBlock();
1068 
1069   // __flags
1070   BlockFlags flags = BLOCK_IS_GLOBAL | BLOCK_HAS_SIGNATURE;
1071   if (blockInfo.UsesStret) flags |= BLOCK_USE_STRET;
1072 
1073   fields[1] = llvm::ConstantInt::get(CGM.IntTy, flags.getBitMask());
1074 
1075   // Reserved
1076   fields[2] = llvm::Constant::getNullValue(CGM.IntTy);
1077 
1078   // Function
1079   fields[3] = blockFn;
1080 
1081   // Descriptor
1082   fields[4] = buildBlockDescriptor(CGM, blockInfo);
1083 
1084   llvm::Constant *init = llvm::ConstantStruct::getAnon(fields);
1085 
1086   llvm::GlobalVariable *literal =
1087     new llvm::GlobalVariable(CGM.getModule(),
1088                              init->getType(),
1089                              /*constant*/ true,
1090                              llvm::GlobalVariable::InternalLinkage,
1091                              init,
1092                              "__block_literal_global");
1093   literal->setAlignment(blockInfo.BlockAlign.getQuantity());
1094 
1095   // Return a constant of the appropriately-casted type.
1096   llvm::Type *requiredType =
1097     CGM.getTypes().ConvertType(blockInfo.getBlockExpr()->getType());
1098   return llvm::ConstantExpr::getBitCast(literal, requiredType);
1099 }
1100 
setBlockContextParameter(const ImplicitParamDecl * D,unsigned argNum,llvm::Value * arg)1101 void CodeGenFunction::setBlockContextParameter(const ImplicitParamDecl *D,
1102                                                unsigned argNum,
1103                                                llvm::Value *arg) {
1104   assert(BlockInfo && "not emitting prologue of block invocation function?!");
1105 
1106   llvm::Value *localAddr = nullptr;
1107   if (CGM.getCodeGenOpts().OptimizationLevel == 0) {
1108     // Allocate a stack slot to let the debug info survive the RA.
1109     Address alloc = CreateMemTemp(D->getType(), D->getName() + ".addr");
1110     Builder.CreateStore(arg, alloc);
1111     localAddr = Builder.CreateLoad(alloc);
1112   }
1113 
1114   if (CGDebugInfo *DI = getDebugInfo()) {
1115     if (CGM.getCodeGenOpts().getDebugInfo() >=
1116         codegenoptions::LimitedDebugInfo) {
1117       DI->setLocation(D->getLocation());
1118       DI->EmitDeclareOfBlockLiteralArgVariable(*BlockInfo, arg, argNum,
1119                                                localAddr, Builder);
1120     }
1121   }
1122 
1123   SourceLocation StartLoc = BlockInfo->getBlockExpr()->getBody()->getLocStart();
1124   ApplyDebugLocation Scope(*this, StartLoc);
1125 
1126   // Instead of messing around with LocalDeclMap, just set the value
1127   // directly as BlockPointer.
1128   BlockPointer = Builder.CreateBitCast(arg,
1129                                        BlockInfo->StructureType->getPointerTo(),
1130                                        "block");
1131 }
1132 
LoadBlockStruct()1133 Address CodeGenFunction::LoadBlockStruct() {
1134   assert(BlockInfo && "not in a block invocation function!");
1135   assert(BlockPointer && "no block pointer set!");
1136   return Address(BlockPointer, BlockInfo->BlockAlign);
1137 }
1138 
1139 llvm::Function *
GenerateBlockFunction(GlobalDecl GD,const CGBlockInfo & blockInfo,const DeclMapTy & ldm,bool IsLambdaConversionToBlock)1140 CodeGenFunction::GenerateBlockFunction(GlobalDecl GD,
1141                                        const CGBlockInfo &blockInfo,
1142                                        const DeclMapTy &ldm,
1143                                        bool IsLambdaConversionToBlock) {
1144   const BlockDecl *blockDecl = blockInfo.getBlockDecl();
1145 
1146   CurGD = GD;
1147 
1148   CurEHLocation = blockInfo.getBlockExpr()->getLocEnd();
1149 
1150   BlockInfo = &blockInfo;
1151 
1152   // Arrange for local static and local extern declarations to appear
1153   // to be local to this function as well, in case they're directly
1154   // referenced in a block.
1155   for (DeclMapTy::const_iterator i = ldm.begin(), e = ldm.end(); i != e; ++i) {
1156     const auto *var = dyn_cast<VarDecl>(i->first);
1157     if (var && !var->hasLocalStorage())
1158       setAddrOfLocalVar(var, i->second);
1159   }
1160 
1161   // Begin building the function declaration.
1162 
1163   // Build the argument list.
1164   FunctionArgList args;
1165 
1166   // The first argument is the block pointer.  Just take it as a void*
1167   // and cast it later.
1168   QualType selfTy = getContext().VoidPtrTy;
1169   IdentifierInfo *II = &CGM.getContext().Idents.get(".block_descriptor");
1170 
1171   ImplicitParamDecl selfDecl(getContext(), const_cast<BlockDecl*>(blockDecl),
1172                              SourceLocation(), II, selfTy);
1173   args.push_back(&selfDecl);
1174 
1175   // Now add the rest of the parameters.
1176   args.append(blockDecl->param_begin(), blockDecl->param_end());
1177 
1178   // Create the function declaration.
1179   const FunctionProtoType *fnType = blockInfo.getBlockExpr()->getFunctionType();
1180   const CGFunctionInfo &fnInfo =
1181     CGM.getTypes().arrangeBlockFunctionDeclaration(fnType, args);
1182   if (CGM.ReturnSlotInterferesWithArgs(fnInfo))
1183     blockInfo.UsesStret = true;
1184 
1185   llvm::FunctionType *fnLLVMType = CGM.getTypes().GetFunctionType(fnInfo);
1186 
1187   StringRef name = CGM.getBlockMangledName(GD, blockDecl);
1188   llvm::Function *fn = llvm::Function::Create(
1189       fnLLVMType, llvm::GlobalValue::InternalLinkage, name, &CGM.getModule());
1190   CGM.SetInternalFunctionAttributes(blockDecl, fn, fnInfo);
1191 
1192   // Begin generating the function.
1193   StartFunction(blockDecl, fnType->getReturnType(), fn, fnInfo, args,
1194                 blockDecl->getLocation(),
1195                 blockInfo.getBlockExpr()->getBody()->getLocStart());
1196 
1197   // Okay.  Undo some of what StartFunction did.
1198 
1199   // At -O0 we generate an explicit alloca for the BlockPointer, so the RA
1200   // won't delete the dbg.declare intrinsics for captured variables.
1201   llvm::Value *BlockPointerDbgLoc = BlockPointer;
1202   if (CGM.getCodeGenOpts().OptimizationLevel == 0) {
1203     // Allocate a stack slot for it, so we can point the debugger to it
1204     Address Alloca = CreateTempAlloca(BlockPointer->getType(),
1205                                       getPointerAlign(),
1206                                       "block.addr");
1207     // Set the DebugLocation to empty, so the store is recognized as a
1208     // frame setup instruction by llvm::DwarfDebug::beginFunction().
1209     auto NL = ApplyDebugLocation::CreateEmpty(*this);
1210     Builder.CreateStore(BlockPointer, Alloca);
1211     BlockPointerDbgLoc = Alloca.getPointer();
1212   }
1213 
1214   // If we have a C++ 'this' reference, go ahead and force it into
1215   // existence now.
1216   if (blockDecl->capturesCXXThis()) {
1217     Address addr =
1218       Builder.CreateStructGEP(LoadBlockStruct(), blockInfo.CXXThisIndex,
1219                               blockInfo.CXXThisOffset, "block.captured-this");
1220     CXXThisValue = Builder.CreateLoad(addr, "this");
1221   }
1222 
1223   // Also force all the constant captures.
1224   for (const auto &CI : blockDecl->captures()) {
1225     const VarDecl *variable = CI.getVariable();
1226     const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
1227     if (!capture.isConstant()) continue;
1228 
1229     CharUnits align = getContext().getDeclAlign(variable);
1230     Address alloca =
1231       CreateMemTemp(variable->getType(), align, "block.captured-const");
1232 
1233     Builder.CreateStore(capture.getConstant(), alloca);
1234 
1235     setAddrOfLocalVar(variable, alloca);
1236   }
1237 
1238   // Save a spot to insert the debug information for all the DeclRefExprs.
1239   llvm::BasicBlock *entry = Builder.GetInsertBlock();
1240   llvm::BasicBlock::iterator entry_ptr = Builder.GetInsertPoint();
1241   --entry_ptr;
1242 
1243   if (IsLambdaConversionToBlock)
1244     EmitLambdaBlockInvokeBody();
1245   else {
1246     PGO.assignRegionCounters(GlobalDecl(blockDecl), fn);
1247     incrementProfileCounter(blockDecl->getBody());
1248     EmitStmt(blockDecl->getBody());
1249   }
1250 
1251   // Remember where we were...
1252   llvm::BasicBlock *resume = Builder.GetInsertBlock();
1253 
1254   // Go back to the entry.
1255   ++entry_ptr;
1256   Builder.SetInsertPoint(entry, entry_ptr);
1257 
1258   // Emit debug information for all the DeclRefExprs.
1259   // FIXME: also for 'this'
1260   if (CGDebugInfo *DI = getDebugInfo()) {
1261     for (const auto &CI : blockDecl->captures()) {
1262       const VarDecl *variable = CI.getVariable();
1263       DI->EmitLocation(Builder, variable->getLocation());
1264 
1265       if (CGM.getCodeGenOpts().getDebugInfo() >=
1266           codegenoptions::LimitedDebugInfo) {
1267         const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
1268         if (capture.isConstant()) {
1269           auto addr = LocalDeclMap.find(variable)->second;
1270           DI->EmitDeclareOfAutoVariable(variable, addr.getPointer(),
1271                                         Builder);
1272           continue;
1273         }
1274 
1275         DI->EmitDeclareOfBlockDeclRefVariable(
1276             variable, BlockPointerDbgLoc, Builder, blockInfo,
1277             entry_ptr == entry->end() ? nullptr : &*entry_ptr);
1278       }
1279     }
1280     // Recover location if it was changed in the above loop.
1281     DI->EmitLocation(Builder,
1282                      cast<CompoundStmt>(blockDecl->getBody())->getRBracLoc());
1283   }
1284 
1285   // And resume where we left off.
1286   if (resume == nullptr)
1287     Builder.ClearInsertionPoint();
1288   else
1289     Builder.SetInsertPoint(resume);
1290 
1291   FinishFunction(cast<CompoundStmt>(blockDecl->getBody())->getRBracLoc());
1292 
1293   return fn;
1294 }
1295 
1296 /*
1297     notes.push_back(HelperInfo());
1298     HelperInfo &note = notes.back();
1299     note.index = capture.getIndex();
1300     note.RequiresCopying = (ci->hasCopyExpr() || BlockRequiresCopying(type));
1301     note.cxxbar_import = ci->getCopyExpr();
1302 
1303     if (ci->isByRef()) {
1304       note.flag = BLOCK_FIELD_IS_BYREF;
1305       if (type.isObjCGCWeak())
1306         note.flag |= BLOCK_FIELD_IS_WEAK;
1307     } else if (type->isBlockPointerType()) {
1308       note.flag = BLOCK_FIELD_IS_BLOCK;
1309     } else {
1310       note.flag = BLOCK_FIELD_IS_OBJECT;
1311     }
1312  */
1313 
1314 /// Generate the copy-helper function for a block closure object:
1315 ///   static void block_copy_helper(block_t *dst, block_t *src);
1316 /// The runtime will have previously initialized 'dst' by doing a
1317 /// bit-copy of 'src'.
1318 ///
1319 /// Note that this copies an entire block closure object to the heap;
1320 /// it should not be confused with a 'byref copy helper', which moves
1321 /// the contents of an individual __block variable to the heap.
1322 llvm::Constant *
GenerateCopyHelperFunction(const CGBlockInfo & blockInfo)1323 CodeGenFunction::GenerateCopyHelperFunction(const CGBlockInfo &blockInfo) {
1324   ASTContext &C = getContext();
1325 
1326   FunctionArgList args;
1327   ImplicitParamDecl dstDecl(getContext(), nullptr, SourceLocation(), nullptr,
1328                             C.VoidPtrTy);
1329   args.push_back(&dstDecl);
1330   ImplicitParamDecl srcDecl(getContext(), nullptr, SourceLocation(), nullptr,
1331                             C.VoidPtrTy);
1332   args.push_back(&srcDecl);
1333 
1334   const CGFunctionInfo &FI =
1335     CGM.getTypes().arrangeBuiltinFunctionDeclaration(C.VoidTy, args);
1336 
1337   // FIXME: it would be nice if these were mergeable with things with
1338   // identical semantics.
1339   llvm::FunctionType *LTy = CGM.getTypes().GetFunctionType(FI);
1340 
1341   llvm::Function *Fn =
1342     llvm::Function::Create(LTy, llvm::GlobalValue::InternalLinkage,
1343                            "__copy_helper_block_", &CGM.getModule());
1344 
1345   IdentifierInfo *II
1346     = &CGM.getContext().Idents.get("__copy_helper_block_");
1347 
1348   FunctionDecl *FD = FunctionDecl::Create(C,
1349                                           C.getTranslationUnitDecl(),
1350                                           SourceLocation(),
1351                                           SourceLocation(), II, C.VoidTy,
1352                                           nullptr, SC_Static,
1353                                           false,
1354                                           false);
1355 
1356   CGM.SetInternalFunctionAttributes(nullptr, Fn, FI);
1357 
1358   auto NL = ApplyDebugLocation::CreateEmpty(*this);
1359   StartFunction(FD, C.VoidTy, Fn, FI, args);
1360   // Create a scope with an artificial location for the body of this function.
1361   auto AL = ApplyDebugLocation::CreateArtificial(*this);
1362   llvm::Type *structPtrTy = blockInfo.StructureType->getPointerTo();
1363 
1364   Address src = GetAddrOfLocalVar(&srcDecl);
1365   src = Address(Builder.CreateLoad(src), blockInfo.BlockAlign);
1366   src = Builder.CreateBitCast(src, structPtrTy, "block.source");
1367 
1368   Address dst = GetAddrOfLocalVar(&dstDecl);
1369   dst = Address(Builder.CreateLoad(dst), blockInfo.BlockAlign);
1370   dst = Builder.CreateBitCast(dst, structPtrTy, "block.dest");
1371 
1372   const BlockDecl *blockDecl = blockInfo.getBlockDecl();
1373 
1374   for (const auto &CI : blockDecl->captures()) {
1375     const VarDecl *variable = CI.getVariable();
1376     QualType type = variable->getType();
1377 
1378     const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
1379     if (capture.isConstant()) continue;
1380 
1381     const Expr *copyExpr = CI.getCopyExpr();
1382     BlockFieldFlags flags;
1383 
1384     bool useARCWeakCopy = false;
1385     bool useARCStrongCopy = false;
1386 
1387     if (copyExpr) {
1388       assert(!CI.isByRef());
1389       // don't bother computing flags
1390 
1391     } else if (CI.isByRef()) {
1392       flags = BLOCK_FIELD_IS_BYREF;
1393       if (type.isObjCGCWeak())
1394         flags |= BLOCK_FIELD_IS_WEAK;
1395 
1396     } else if (type->isObjCRetainableType()) {
1397       flags = BLOCK_FIELD_IS_OBJECT;
1398       bool isBlockPointer = type->isBlockPointerType();
1399       if (isBlockPointer)
1400         flags = BLOCK_FIELD_IS_BLOCK;
1401 
1402       // Special rules for ARC captures:
1403       Qualifiers qs = type.getQualifiers();
1404 
1405       // We need to register __weak direct captures with the runtime.
1406       if (qs.getObjCLifetime() == Qualifiers::OCL_Weak) {
1407         useARCWeakCopy = true;
1408 
1409       // We need to retain the copied value for __strong direct captures.
1410       } else if (qs.getObjCLifetime() == Qualifiers::OCL_Strong) {
1411         // If it's a block pointer, we have to copy the block and
1412         // assign that to the destination pointer, so we might as
1413         // well use _Block_object_assign.  Otherwise we can avoid that.
1414         if (!isBlockPointer)
1415           useARCStrongCopy = true;
1416 
1417       // Non-ARC captures of retainable pointers are strong and
1418       // therefore require a call to _Block_object_assign.
1419       } else if (!qs.getObjCLifetime() && !getLangOpts().ObjCAutoRefCount) {
1420         // fall through
1421 
1422       // Otherwise the memcpy is fine.
1423       } else {
1424         continue;
1425       }
1426 
1427     // For all other types, the memcpy is fine.
1428     } else {
1429       continue;
1430     }
1431 
1432     unsigned index = capture.getIndex();
1433     Address srcField = Builder.CreateStructGEP(src, index, capture.getOffset());
1434     Address dstField = Builder.CreateStructGEP(dst, index, capture.getOffset());
1435 
1436     // If there's an explicit copy expression, we do that.
1437     if (copyExpr) {
1438       EmitSynthesizedCXXCopyCtor(dstField, srcField, copyExpr);
1439     } else if (useARCWeakCopy) {
1440       EmitARCCopyWeak(dstField, srcField);
1441     } else {
1442       llvm::Value *srcValue = Builder.CreateLoad(srcField, "blockcopy.src");
1443       if (useARCStrongCopy) {
1444         // At -O0, store null into the destination field (so that the
1445         // storeStrong doesn't over-release) and then call storeStrong.
1446         // This is a workaround to not having an initStrong call.
1447         if (CGM.getCodeGenOpts().OptimizationLevel == 0) {
1448           auto *ty = cast<llvm::PointerType>(srcValue->getType());
1449           llvm::Value *null = llvm::ConstantPointerNull::get(ty);
1450           Builder.CreateStore(null, dstField);
1451           EmitARCStoreStrongCall(dstField, srcValue, true);
1452 
1453         // With optimization enabled, take advantage of the fact that
1454         // the blocks runtime guarantees a memcpy of the block data, and
1455         // just emit a retain of the src field.
1456         } else {
1457           EmitARCRetainNonBlock(srcValue);
1458 
1459           // We don't need this anymore, so kill it.  It's not quite
1460           // worth the annoyance to avoid creating it in the first place.
1461           cast<llvm::Instruction>(dstField.getPointer())->eraseFromParent();
1462         }
1463       } else {
1464         srcValue = Builder.CreateBitCast(srcValue, VoidPtrTy);
1465         llvm::Value *dstAddr =
1466           Builder.CreateBitCast(dstField.getPointer(), VoidPtrTy);
1467         llvm::Value *args[] = {
1468           dstAddr, srcValue, llvm::ConstantInt::get(Int32Ty, flags.getBitMask())
1469         };
1470 
1471         bool copyCanThrow = false;
1472         if (CI.isByRef() && variable->getType()->getAsCXXRecordDecl()) {
1473           const Expr *copyExpr =
1474             CGM.getContext().getBlockVarCopyInits(variable);
1475           if (copyExpr) {
1476             copyCanThrow = true; // FIXME: reuse the noexcept logic
1477           }
1478         }
1479 
1480         if (copyCanThrow) {
1481           EmitRuntimeCallOrInvoke(CGM.getBlockObjectAssign(), args);
1482         } else {
1483           EmitNounwindRuntimeCall(CGM.getBlockObjectAssign(), args);
1484         }
1485       }
1486     }
1487   }
1488 
1489   FinishFunction();
1490 
1491   return llvm::ConstantExpr::getBitCast(Fn, VoidPtrTy);
1492 }
1493 
1494 /// Generate the destroy-helper function for a block closure object:
1495 ///   static void block_destroy_helper(block_t *theBlock);
1496 ///
1497 /// Note that this destroys a heap-allocated block closure object;
1498 /// it should not be confused with a 'byref destroy helper', which
1499 /// destroys the heap-allocated contents of an individual __block
1500 /// variable.
1501 llvm::Constant *
GenerateDestroyHelperFunction(const CGBlockInfo & blockInfo)1502 CodeGenFunction::GenerateDestroyHelperFunction(const CGBlockInfo &blockInfo) {
1503   ASTContext &C = getContext();
1504 
1505   FunctionArgList args;
1506   ImplicitParamDecl srcDecl(getContext(), nullptr, SourceLocation(), nullptr,
1507                             C.VoidPtrTy);
1508   args.push_back(&srcDecl);
1509 
1510   const CGFunctionInfo &FI =
1511     CGM.getTypes().arrangeBuiltinFunctionDeclaration(C.VoidTy, args);
1512 
1513   // FIXME: We'd like to put these into a mergable by content, with
1514   // internal linkage.
1515   llvm::FunctionType *LTy = CGM.getTypes().GetFunctionType(FI);
1516 
1517   llvm::Function *Fn =
1518     llvm::Function::Create(LTy, llvm::GlobalValue::InternalLinkage,
1519                            "__destroy_helper_block_", &CGM.getModule());
1520 
1521   IdentifierInfo *II
1522     = &CGM.getContext().Idents.get("__destroy_helper_block_");
1523 
1524   FunctionDecl *FD = FunctionDecl::Create(C, C.getTranslationUnitDecl(),
1525                                           SourceLocation(),
1526                                           SourceLocation(), II, C.VoidTy,
1527                                           nullptr, SC_Static,
1528                                           false, false);
1529 
1530   CGM.SetInternalFunctionAttributes(nullptr, Fn, FI);
1531 
1532   // Create a scope with an artificial location for the body of this function.
1533   auto NL = ApplyDebugLocation::CreateEmpty(*this);
1534   StartFunction(FD, C.VoidTy, Fn, FI, args);
1535   auto AL = ApplyDebugLocation::CreateArtificial(*this);
1536 
1537   llvm::Type *structPtrTy = blockInfo.StructureType->getPointerTo();
1538 
1539   Address src = GetAddrOfLocalVar(&srcDecl);
1540   src = Address(Builder.CreateLoad(src), blockInfo.BlockAlign);
1541   src = Builder.CreateBitCast(src, structPtrTy, "block");
1542 
1543   const BlockDecl *blockDecl = blockInfo.getBlockDecl();
1544 
1545   CodeGenFunction::RunCleanupsScope cleanups(*this);
1546 
1547   for (const auto &CI : blockDecl->captures()) {
1548     const VarDecl *variable = CI.getVariable();
1549     QualType type = variable->getType();
1550 
1551     const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
1552     if (capture.isConstant()) continue;
1553 
1554     BlockFieldFlags flags;
1555     const CXXDestructorDecl *dtor = nullptr;
1556 
1557     bool useARCWeakDestroy = false;
1558     bool useARCStrongDestroy = false;
1559 
1560     if (CI.isByRef()) {
1561       flags = BLOCK_FIELD_IS_BYREF;
1562       if (type.isObjCGCWeak())
1563         flags |= BLOCK_FIELD_IS_WEAK;
1564     } else if (const CXXRecordDecl *record = type->getAsCXXRecordDecl()) {
1565       if (record->hasTrivialDestructor())
1566         continue;
1567       dtor = record->getDestructor();
1568     } else if (type->isObjCRetainableType()) {
1569       flags = BLOCK_FIELD_IS_OBJECT;
1570       if (type->isBlockPointerType())
1571         flags = BLOCK_FIELD_IS_BLOCK;
1572 
1573       // Special rules for ARC captures.
1574       Qualifiers qs = type.getQualifiers();
1575 
1576       // Use objc_storeStrong for __strong direct captures; the
1577       // dynamic tools really like it when we do this.
1578       if (qs.getObjCLifetime() == Qualifiers::OCL_Strong) {
1579         useARCStrongDestroy = true;
1580 
1581       // Support __weak direct captures.
1582       } else if (qs.getObjCLifetime() == Qualifiers::OCL_Weak) {
1583         useARCWeakDestroy = true;
1584 
1585       // Non-ARC captures are strong, and we need to use _Block_object_dispose.
1586       } else if (!qs.hasObjCLifetime() && !getLangOpts().ObjCAutoRefCount) {
1587         // fall through
1588 
1589       // Otherwise, we have nothing to do.
1590       } else {
1591         continue;
1592       }
1593     } else {
1594       continue;
1595     }
1596 
1597     Address srcField =
1598       Builder.CreateStructGEP(src, capture.getIndex(), capture.getOffset());
1599 
1600     // If there's an explicit copy expression, we do that.
1601     if (dtor) {
1602       PushDestructorCleanup(dtor, srcField);
1603 
1604     // If this is a __weak capture, emit the release directly.
1605     } else if (useARCWeakDestroy) {
1606       EmitARCDestroyWeak(srcField);
1607 
1608     // Destroy strong objects with a call if requested.
1609     } else if (useARCStrongDestroy) {
1610       EmitARCDestroyStrong(srcField, ARCImpreciseLifetime);
1611 
1612     // Otherwise we call _Block_object_dispose.  It wouldn't be too
1613     // hard to just emit this as a cleanup if we wanted to make sure
1614     // that things were done in reverse.
1615     } else {
1616       llvm::Value *value = Builder.CreateLoad(srcField);
1617       value = Builder.CreateBitCast(value, VoidPtrTy);
1618       BuildBlockRelease(value, flags);
1619     }
1620   }
1621 
1622   cleanups.ForceCleanup();
1623 
1624   FinishFunction();
1625 
1626   return llvm::ConstantExpr::getBitCast(Fn, VoidPtrTy);
1627 }
1628 
1629 namespace {
1630 
1631 /// Emits the copy/dispose helper functions for a __block object of id type.
1632 class ObjectByrefHelpers final : public BlockByrefHelpers {
1633   BlockFieldFlags Flags;
1634 
1635 public:
ObjectByrefHelpers(CharUnits alignment,BlockFieldFlags flags)1636   ObjectByrefHelpers(CharUnits alignment, BlockFieldFlags flags)
1637     : BlockByrefHelpers(alignment), Flags(flags) {}
1638 
emitCopy(CodeGenFunction & CGF,Address destField,Address srcField)1639   void emitCopy(CodeGenFunction &CGF, Address destField,
1640                 Address srcField) override {
1641     destField = CGF.Builder.CreateBitCast(destField, CGF.VoidPtrTy);
1642 
1643     srcField = CGF.Builder.CreateBitCast(srcField, CGF.VoidPtrPtrTy);
1644     llvm::Value *srcValue = CGF.Builder.CreateLoad(srcField);
1645 
1646     unsigned flags = (Flags | BLOCK_BYREF_CALLER).getBitMask();
1647 
1648     llvm::Value *flagsVal = llvm::ConstantInt::get(CGF.Int32Ty, flags);
1649     llvm::Value *fn = CGF.CGM.getBlockObjectAssign();
1650 
1651     llvm::Value *args[] = { destField.getPointer(), srcValue, flagsVal };
1652     CGF.EmitNounwindRuntimeCall(fn, args);
1653   }
1654 
emitDispose(CodeGenFunction & CGF,Address field)1655   void emitDispose(CodeGenFunction &CGF, Address field) override {
1656     field = CGF.Builder.CreateBitCast(field, CGF.Int8PtrTy->getPointerTo(0));
1657     llvm::Value *value = CGF.Builder.CreateLoad(field);
1658 
1659     CGF.BuildBlockRelease(value, Flags | BLOCK_BYREF_CALLER);
1660   }
1661 
profileImpl(llvm::FoldingSetNodeID & id) const1662   void profileImpl(llvm::FoldingSetNodeID &id) const override {
1663     id.AddInteger(Flags.getBitMask());
1664   }
1665 };
1666 
1667 /// Emits the copy/dispose helpers for an ARC __block __weak variable.
1668 class ARCWeakByrefHelpers final : public BlockByrefHelpers {
1669 public:
ARCWeakByrefHelpers(CharUnits alignment)1670   ARCWeakByrefHelpers(CharUnits alignment) : BlockByrefHelpers(alignment) {}
1671 
emitCopy(CodeGenFunction & CGF,Address destField,Address srcField)1672   void emitCopy(CodeGenFunction &CGF, Address destField,
1673                 Address srcField) override {
1674     CGF.EmitARCMoveWeak(destField, srcField);
1675   }
1676 
emitDispose(CodeGenFunction & CGF,Address field)1677   void emitDispose(CodeGenFunction &CGF, Address field) override {
1678     CGF.EmitARCDestroyWeak(field);
1679   }
1680 
profileImpl(llvm::FoldingSetNodeID & id) const1681   void profileImpl(llvm::FoldingSetNodeID &id) const override {
1682     // 0 is distinguishable from all pointers and byref flags
1683     id.AddInteger(0);
1684   }
1685 };
1686 
1687 /// Emits the copy/dispose helpers for an ARC __block __strong variable
1688 /// that's not of block-pointer type.
1689 class ARCStrongByrefHelpers final : public BlockByrefHelpers {
1690 public:
ARCStrongByrefHelpers(CharUnits alignment)1691   ARCStrongByrefHelpers(CharUnits alignment) : BlockByrefHelpers(alignment) {}
1692 
emitCopy(CodeGenFunction & CGF,Address destField,Address srcField)1693   void emitCopy(CodeGenFunction &CGF, Address destField,
1694                 Address srcField) override {
1695     // Do a "move" by copying the value and then zeroing out the old
1696     // variable.
1697 
1698     llvm::Value *value = CGF.Builder.CreateLoad(srcField);
1699 
1700     llvm::Value *null =
1701       llvm::ConstantPointerNull::get(cast<llvm::PointerType>(value->getType()));
1702 
1703     if (CGF.CGM.getCodeGenOpts().OptimizationLevel == 0) {
1704       CGF.Builder.CreateStore(null, destField);
1705       CGF.EmitARCStoreStrongCall(destField, value, /*ignored*/ true);
1706       CGF.EmitARCStoreStrongCall(srcField, null, /*ignored*/ true);
1707       return;
1708     }
1709     CGF.Builder.CreateStore(value, destField);
1710     CGF.Builder.CreateStore(null, srcField);
1711   }
1712 
emitDispose(CodeGenFunction & CGF,Address field)1713   void emitDispose(CodeGenFunction &CGF, Address field) override {
1714     CGF.EmitARCDestroyStrong(field, ARCImpreciseLifetime);
1715   }
1716 
profileImpl(llvm::FoldingSetNodeID & id) const1717   void profileImpl(llvm::FoldingSetNodeID &id) const override {
1718     // 1 is distinguishable from all pointers and byref flags
1719     id.AddInteger(1);
1720   }
1721 };
1722 
1723 /// Emits the copy/dispose helpers for an ARC __block __strong
1724 /// variable that's of block-pointer type.
1725 class ARCStrongBlockByrefHelpers final : public BlockByrefHelpers {
1726 public:
ARCStrongBlockByrefHelpers(CharUnits alignment)1727   ARCStrongBlockByrefHelpers(CharUnits alignment)
1728     : BlockByrefHelpers(alignment) {}
1729 
emitCopy(CodeGenFunction & CGF,Address destField,Address srcField)1730   void emitCopy(CodeGenFunction &CGF, Address destField,
1731                 Address srcField) override {
1732     // Do the copy with objc_retainBlock; that's all that
1733     // _Block_object_assign would do anyway, and we'd have to pass the
1734     // right arguments to make sure it doesn't get no-op'ed.
1735     llvm::Value *oldValue = CGF.Builder.CreateLoad(srcField);
1736     llvm::Value *copy = CGF.EmitARCRetainBlock(oldValue, /*mandatory*/ true);
1737     CGF.Builder.CreateStore(copy, destField);
1738   }
1739 
emitDispose(CodeGenFunction & CGF,Address field)1740   void emitDispose(CodeGenFunction &CGF, Address field) override {
1741     CGF.EmitARCDestroyStrong(field, ARCImpreciseLifetime);
1742   }
1743 
profileImpl(llvm::FoldingSetNodeID & id) const1744   void profileImpl(llvm::FoldingSetNodeID &id) const override {
1745     // 2 is distinguishable from all pointers and byref flags
1746     id.AddInteger(2);
1747   }
1748 };
1749 
1750 /// Emits the copy/dispose helpers for a __block variable with a
1751 /// nontrivial copy constructor or destructor.
1752 class CXXByrefHelpers final : public BlockByrefHelpers {
1753   QualType VarType;
1754   const Expr *CopyExpr;
1755 
1756 public:
CXXByrefHelpers(CharUnits alignment,QualType type,const Expr * copyExpr)1757   CXXByrefHelpers(CharUnits alignment, QualType type,
1758                   const Expr *copyExpr)
1759     : BlockByrefHelpers(alignment), VarType(type), CopyExpr(copyExpr) {}
1760 
needsCopy() const1761   bool needsCopy() const override { return CopyExpr != nullptr; }
emitCopy(CodeGenFunction & CGF,Address destField,Address srcField)1762   void emitCopy(CodeGenFunction &CGF, Address destField,
1763                 Address srcField) override {
1764     if (!CopyExpr) return;
1765     CGF.EmitSynthesizedCXXCopyCtor(destField, srcField, CopyExpr);
1766   }
1767 
emitDispose(CodeGenFunction & CGF,Address field)1768   void emitDispose(CodeGenFunction &CGF, Address field) override {
1769     EHScopeStack::stable_iterator cleanupDepth = CGF.EHStack.stable_begin();
1770     CGF.PushDestructorCleanup(VarType, field);
1771     CGF.PopCleanupBlocks(cleanupDepth);
1772   }
1773 
profileImpl(llvm::FoldingSetNodeID & id) const1774   void profileImpl(llvm::FoldingSetNodeID &id) const override {
1775     id.AddPointer(VarType.getCanonicalType().getAsOpaquePtr());
1776   }
1777 };
1778 } // end anonymous namespace
1779 
1780 static llvm::Constant *
generateByrefCopyHelper(CodeGenFunction & CGF,const BlockByrefInfo & byrefInfo,BlockByrefHelpers & generator)1781 generateByrefCopyHelper(CodeGenFunction &CGF, const BlockByrefInfo &byrefInfo,
1782                         BlockByrefHelpers &generator) {
1783   ASTContext &Context = CGF.getContext();
1784 
1785   QualType R = Context.VoidTy;
1786 
1787   FunctionArgList args;
1788   ImplicitParamDecl dst(CGF.getContext(), nullptr, SourceLocation(), nullptr,
1789                         Context.VoidPtrTy);
1790   args.push_back(&dst);
1791 
1792   ImplicitParamDecl src(CGF.getContext(), nullptr, SourceLocation(), nullptr,
1793                         Context.VoidPtrTy);
1794   args.push_back(&src);
1795 
1796   const CGFunctionInfo &FI =
1797     CGF.CGM.getTypes().arrangeBuiltinFunctionDeclaration(R, args);
1798 
1799   llvm::FunctionType *LTy = CGF.CGM.getTypes().GetFunctionType(FI);
1800 
1801   // FIXME: We'd like to put these into a mergable by content, with
1802   // internal linkage.
1803   llvm::Function *Fn =
1804     llvm::Function::Create(LTy, llvm::GlobalValue::InternalLinkage,
1805                            "__Block_byref_object_copy_", &CGF.CGM.getModule());
1806 
1807   IdentifierInfo *II
1808     = &Context.Idents.get("__Block_byref_object_copy_");
1809 
1810   FunctionDecl *FD = FunctionDecl::Create(Context,
1811                                           Context.getTranslationUnitDecl(),
1812                                           SourceLocation(),
1813                                           SourceLocation(), II, R, nullptr,
1814                                           SC_Static,
1815                                           false, false);
1816 
1817   CGF.CGM.SetInternalFunctionAttributes(nullptr, Fn, FI);
1818 
1819   CGF.StartFunction(FD, R, Fn, FI, args);
1820 
1821   if (generator.needsCopy()) {
1822     llvm::Type *byrefPtrType = byrefInfo.Type->getPointerTo(0);
1823 
1824     // dst->x
1825     Address destField = CGF.GetAddrOfLocalVar(&dst);
1826     destField = Address(CGF.Builder.CreateLoad(destField),
1827                         byrefInfo.ByrefAlignment);
1828     destField = CGF.Builder.CreateBitCast(destField, byrefPtrType);
1829     destField = CGF.emitBlockByrefAddress(destField, byrefInfo, false,
1830                                           "dest-object");
1831 
1832     // src->x
1833     Address srcField = CGF.GetAddrOfLocalVar(&src);
1834     srcField = Address(CGF.Builder.CreateLoad(srcField),
1835                        byrefInfo.ByrefAlignment);
1836     srcField = CGF.Builder.CreateBitCast(srcField, byrefPtrType);
1837     srcField = CGF.emitBlockByrefAddress(srcField, byrefInfo, false,
1838                                          "src-object");
1839 
1840     generator.emitCopy(CGF, destField, srcField);
1841   }
1842 
1843   CGF.FinishFunction();
1844 
1845   return llvm::ConstantExpr::getBitCast(Fn, CGF.Int8PtrTy);
1846 }
1847 
1848 /// Build the copy helper for a __block variable.
buildByrefCopyHelper(CodeGenModule & CGM,const BlockByrefInfo & byrefInfo,BlockByrefHelpers & generator)1849 static llvm::Constant *buildByrefCopyHelper(CodeGenModule &CGM,
1850                                             const BlockByrefInfo &byrefInfo,
1851                                             BlockByrefHelpers &generator) {
1852   CodeGenFunction CGF(CGM);
1853   return generateByrefCopyHelper(CGF, byrefInfo, generator);
1854 }
1855 
1856 /// Generate code for a __block variable's dispose helper.
1857 static llvm::Constant *
generateByrefDisposeHelper(CodeGenFunction & CGF,const BlockByrefInfo & byrefInfo,BlockByrefHelpers & generator)1858 generateByrefDisposeHelper(CodeGenFunction &CGF,
1859                            const BlockByrefInfo &byrefInfo,
1860                            BlockByrefHelpers &generator) {
1861   ASTContext &Context = CGF.getContext();
1862   QualType R = Context.VoidTy;
1863 
1864   FunctionArgList args;
1865   ImplicitParamDecl src(CGF.getContext(), nullptr, SourceLocation(), nullptr,
1866                         Context.VoidPtrTy);
1867   args.push_back(&src);
1868 
1869   const CGFunctionInfo &FI =
1870     CGF.CGM.getTypes().arrangeBuiltinFunctionDeclaration(R, args);
1871 
1872   llvm::FunctionType *LTy = CGF.CGM.getTypes().GetFunctionType(FI);
1873 
1874   // FIXME: We'd like to put these into a mergable by content, with
1875   // internal linkage.
1876   llvm::Function *Fn =
1877     llvm::Function::Create(LTy, llvm::GlobalValue::InternalLinkage,
1878                            "__Block_byref_object_dispose_",
1879                            &CGF.CGM.getModule());
1880 
1881   IdentifierInfo *II
1882     = &Context.Idents.get("__Block_byref_object_dispose_");
1883 
1884   FunctionDecl *FD = FunctionDecl::Create(Context,
1885                                           Context.getTranslationUnitDecl(),
1886                                           SourceLocation(),
1887                                           SourceLocation(), II, R, nullptr,
1888                                           SC_Static,
1889                                           false, false);
1890 
1891   CGF.CGM.SetInternalFunctionAttributes(nullptr, Fn, FI);
1892 
1893   CGF.StartFunction(FD, R, Fn, FI, args);
1894 
1895   if (generator.needsDispose()) {
1896     Address addr = CGF.GetAddrOfLocalVar(&src);
1897     addr = Address(CGF.Builder.CreateLoad(addr), byrefInfo.ByrefAlignment);
1898     auto byrefPtrType = byrefInfo.Type->getPointerTo(0);
1899     addr = CGF.Builder.CreateBitCast(addr, byrefPtrType);
1900     addr = CGF.emitBlockByrefAddress(addr, byrefInfo, false, "object");
1901 
1902     generator.emitDispose(CGF, addr);
1903   }
1904 
1905   CGF.FinishFunction();
1906 
1907   return llvm::ConstantExpr::getBitCast(Fn, CGF.Int8PtrTy);
1908 }
1909 
1910 /// Build the dispose helper for a __block variable.
buildByrefDisposeHelper(CodeGenModule & CGM,const BlockByrefInfo & byrefInfo,BlockByrefHelpers & generator)1911 static llvm::Constant *buildByrefDisposeHelper(CodeGenModule &CGM,
1912                                                const BlockByrefInfo &byrefInfo,
1913                                                BlockByrefHelpers &generator) {
1914   CodeGenFunction CGF(CGM);
1915   return generateByrefDisposeHelper(CGF, byrefInfo, generator);
1916 }
1917 
1918 /// Lazily build the copy and dispose helpers for a __block variable
1919 /// with the given information.
1920 template <class T>
buildByrefHelpers(CodeGenModule & CGM,const BlockByrefInfo & byrefInfo,T && generator)1921 static T *buildByrefHelpers(CodeGenModule &CGM, const BlockByrefInfo &byrefInfo,
1922                             T &&generator) {
1923   llvm::FoldingSetNodeID id;
1924   generator.Profile(id);
1925 
1926   void *insertPos;
1927   BlockByrefHelpers *node
1928     = CGM.ByrefHelpersCache.FindNodeOrInsertPos(id, insertPos);
1929   if (node) return static_cast<T*>(node);
1930 
1931   generator.CopyHelper = buildByrefCopyHelper(CGM, byrefInfo, generator);
1932   generator.DisposeHelper = buildByrefDisposeHelper(CGM, byrefInfo, generator);
1933 
1934   T *copy = new (CGM.getContext()) T(std::move(generator));
1935   CGM.ByrefHelpersCache.InsertNode(copy, insertPos);
1936   return copy;
1937 }
1938 
1939 /// Build the copy and dispose helpers for the given __block variable
1940 /// emission.  Places the helpers in the global cache.  Returns null
1941 /// if no helpers are required.
1942 BlockByrefHelpers *
buildByrefHelpers(llvm::StructType & byrefType,const AutoVarEmission & emission)1943 CodeGenFunction::buildByrefHelpers(llvm::StructType &byrefType,
1944                                    const AutoVarEmission &emission) {
1945   const VarDecl &var = *emission.Variable;
1946   QualType type = var.getType();
1947 
1948   auto &byrefInfo = getBlockByrefInfo(&var);
1949 
1950   // The alignment we care about for the purposes of uniquing byref
1951   // helpers is the alignment of the actual byref value field.
1952   CharUnits valueAlignment =
1953     byrefInfo.ByrefAlignment.alignmentAtOffset(byrefInfo.FieldOffset);
1954 
1955   if (const CXXRecordDecl *record = type->getAsCXXRecordDecl()) {
1956     const Expr *copyExpr = CGM.getContext().getBlockVarCopyInits(&var);
1957     if (!copyExpr && record->hasTrivialDestructor()) return nullptr;
1958 
1959     return ::buildByrefHelpers(
1960         CGM, byrefInfo, CXXByrefHelpers(valueAlignment, type, copyExpr));
1961   }
1962 
1963   // Otherwise, if we don't have a retainable type, there's nothing to do.
1964   // that the runtime does extra copies.
1965   if (!type->isObjCRetainableType()) return nullptr;
1966 
1967   Qualifiers qs = type.getQualifiers();
1968 
1969   // If we have lifetime, that dominates.
1970   if (Qualifiers::ObjCLifetime lifetime = qs.getObjCLifetime()) {
1971     switch (lifetime) {
1972     case Qualifiers::OCL_None: llvm_unreachable("impossible");
1973 
1974     // These are just bits as far as the runtime is concerned.
1975     case Qualifiers::OCL_ExplicitNone:
1976     case Qualifiers::OCL_Autoreleasing:
1977       return nullptr;
1978 
1979     // Tell the runtime that this is ARC __weak, called by the
1980     // byref routines.
1981     case Qualifiers::OCL_Weak:
1982       return ::buildByrefHelpers(CGM, byrefInfo,
1983                                  ARCWeakByrefHelpers(valueAlignment));
1984 
1985     // ARC __strong __block variables need to be retained.
1986     case Qualifiers::OCL_Strong:
1987       // Block pointers need to be copied, and there's no direct
1988       // transfer possible.
1989       if (type->isBlockPointerType()) {
1990         return ::buildByrefHelpers(CGM, byrefInfo,
1991                                    ARCStrongBlockByrefHelpers(valueAlignment));
1992 
1993       // Otherwise, we transfer ownership of the retain from the stack
1994       // to the heap.
1995       } else {
1996         return ::buildByrefHelpers(CGM, byrefInfo,
1997                                    ARCStrongByrefHelpers(valueAlignment));
1998       }
1999     }
2000     llvm_unreachable("fell out of lifetime switch!");
2001   }
2002 
2003   BlockFieldFlags flags;
2004   if (type->isBlockPointerType()) {
2005     flags |= BLOCK_FIELD_IS_BLOCK;
2006   } else if (CGM.getContext().isObjCNSObjectType(type) ||
2007              type->isObjCObjectPointerType()) {
2008     flags |= BLOCK_FIELD_IS_OBJECT;
2009   } else {
2010     return nullptr;
2011   }
2012 
2013   if (type.isObjCGCWeak())
2014     flags |= BLOCK_FIELD_IS_WEAK;
2015 
2016   return ::buildByrefHelpers(CGM, byrefInfo,
2017                              ObjectByrefHelpers(valueAlignment, flags));
2018 }
2019 
emitBlockByrefAddress(Address baseAddr,const VarDecl * var,bool followForward)2020 Address CodeGenFunction::emitBlockByrefAddress(Address baseAddr,
2021                                                const VarDecl *var,
2022                                                bool followForward) {
2023   auto &info = getBlockByrefInfo(var);
2024   return emitBlockByrefAddress(baseAddr, info, followForward, var->getName());
2025 }
2026 
emitBlockByrefAddress(Address baseAddr,const BlockByrefInfo & info,bool followForward,const llvm::Twine & name)2027 Address CodeGenFunction::emitBlockByrefAddress(Address baseAddr,
2028                                                const BlockByrefInfo &info,
2029                                                bool followForward,
2030                                                const llvm::Twine &name) {
2031   // Chase the forwarding address if requested.
2032   if (followForward) {
2033     Address forwardingAddr =
2034       Builder.CreateStructGEP(baseAddr, 1, getPointerSize(), "forwarding");
2035     baseAddr = Address(Builder.CreateLoad(forwardingAddr), info.ByrefAlignment);
2036   }
2037 
2038   return Builder.CreateStructGEP(baseAddr, info.FieldIndex,
2039                                  info.FieldOffset, name);
2040 }
2041 
2042 /// BuildByrefInfo - This routine changes a __block variable declared as T x
2043 ///   into:
2044 ///
2045 ///      struct {
2046 ///        void *__isa;
2047 ///        void *__forwarding;
2048 ///        int32_t __flags;
2049 ///        int32_t __size;
2050 ///        void *__copy_helper;       // only if needed
2051 ///        void *__destroy_helper;    // only if needed
2052 ///        void *__byref_variable_layout;// only if needed
2053 ///        char padding[X];           // only if needed
2054 ///        T x;
2055 ///      } x
2056 ///
getBlockByrefInfo(const VarDecl * D)2057 const BlockByrefInfo &CodeGenFunction::getBlockByrefInfo(const VarDecl *D) {
2058   auto it = BlockByrefInfos.find(D);
2059   if (it != BlockByrefInfos.end())
2060     return it->second;
2061 
2062   llvm::StructType *byrefType =
2063     llvm::StructType::create(getLLVMContext(),
2064                              "struct.__block_byref_" + D->getNameAsString());
2065 
2066   QualType Ty = D->getType();
2067 
2068   CharUnits size;
2069   SmallVector<llvm::Type *, 8> types;
2070 
2071   // void *__isa;
2072   types.push_back(Int8PtrTy);
2073   size += getPointerSize();
2074 
2075   // void *__forwarding;
2076   types.push_back(llvm::PointerType::getUnqual(byrefType));
2077   size += getPointerSize();
2078 
2079   // int32_t __flags;
2080   types.push_back(Int32Ty);
2081   size += CharUnits::fromQuantity(4);
2082 
2083   // int32_t __size;
2084   types.push_back(Int32Ty);
2085   size += CharUnits::fromQuantity(4);
2086 
2087   // Note that this must match *exactly* the logic in buildByrefHelpers.
2088   bool hasCopyAndDispose = getContext().BlockRequiresCopying(Ty, D);
2089   if (hasCopyAndDispose) {
2090     /// void *__copy_helper;
2091     types.push_back(Int8PtrTy);
2092     size += getPointerSize();
2093 
2094     /// void *__destroy_helper;
2095     types.push_back(Int8PtrTy);
2096     size += getPointerSize();
2097   }
2098 
2099   bool HasByrefExtendedLayout = false;
2100   Qualifiers::ObjCLifetime Lifetime;
2101   if (getContext().getByrefLifetime(Ty, Lifetime, HasByrefExtendedLayout) &&
2102       HasByrefExtendedLayout) {
2103     /// void *__byref_variable_layout;
2104     types.push_back(Int8PtrTy);
2105     size += CharUnits::fromQuantity(PointerSizeInBytes);
2106   }
2107 
2108   // T x;
2109   llvm::Type *varTy = ConvertTypeForMem(Ty);
2110 
2111   bool packed = false;
2112   CharUnits varAlign = getContext().getDeclAlign(D);
2113   CharUnits varOffset = size.alignTo(varAlign);
2114 
2115   // We may have to insert padding.
2116   if (varOffset != size) {
2117     llvm::Type *paddingTy =
2118       llvm::ArrayType::get(Int8Ty, (varOffset - size).getQuantity());
2119 
2120     types.push_back(paddingTy);
2121     size = varOffset;
2122 
2123   // Conversely, we might have to prevent LLVM from inserting padding.
2124   } else if (CGM.getDataLayout().getABITypeAlignment(varTy)
2125                > varAlign.getQuantity()) {
2126     packed = true;
2127   }
2128   types.push_back(varTy);
2129 
2130   byrefType->setBody(types, packed);
2131 
2132   BlockByrefInfo info;
2133   info.Type = byrefType;
2134   info.FieldIndex = types.size() - 1;
2135   info.FieldOffset = varOffset;
2136   info.ByrefAlignment = std::max(varAlign, getPointerAlign());
2137 
2138   auto pair = BlockByrefInfos.insert({D, info});
2139   assert(pair.second && "info was inserted recursively?");
2140   return pair.first->second;
2141 }
2142 
2143 /// Initialize the structural components of a __block variable, i.e.
2144 /// everything but the actual object.
emitByrefStructureInit(const AutoVarEmission & emission)2145 void CodeGenFunction::emitByrefStructureInit(const AutoVarEmission &emission) {
2146   // Find the address of the local.
2147   Address addr = emission.Addr;
2148 
2149   // That's an alloca of the byref structure type.
2150   llvm::StructType *byrefType = cast<llvm::StructType>(
2151     cast<llvm::PointerType>(addr.getPointer()->getType())->getElementType());
2152 
2153   unsigned nextHeaderIndex = 0;
2154   CharUnits nextHeaderOffset;
2155   auto storeHeaderField = [&](llvm::Value *value, CharUnits fieldSize,
2156                               const Twine &name) {
2157     auto fieldAddr = Builder.CreateStructGEP(addr, nextHeaderIndex,
2158                                              nextHeaderOffset, name);
2159     Builder.CreateStore(value, fieldAddr);
2160 
2161     nextHeaderIndex++;
2162     nextHeaderOffset += fieldSize;
2163   };
2164 
2165   // Build the byref helpers if necessary.  This is null if we don't need any.
2166   BlockByrefHelpers *helpers = buildByrefHelpers(*byrefType, emission);
2167 
2168   const VarDecl &D = *emission.Variable;
2169   QualType type = D.getType();
2170 
2171   bool HasByrefExtendedLayout;
2172   Qualifiers::ObjCLifetime ByrefLifetime;
2173   bool ByRefHasLifetime =
2174     getContext().getByrefLifetime(type, ByrefLifetime, HasByrefExtendedLayout);
2175 
2176   llvm::Value *V;
2177 
2178   // Initialize the 'isa', which is just 0 or 1.
2179   int isa = 0;
2180   if (type.isObjCGCWeak())
2181     isa = 1;
2182   V = Builder.CreateIntToPtr(Builder.getInt32(isa), Int8PtrTy, "isa");
2183   storeHeaderField(V, getPointerSize(), "byref.isa");
2184 
2185   // Store the address of the variable into its own forwarding pointer.
2186   storeHeaderField(addr.getPointer(), getPointerSize(), "byref.forwarding");
2187 
2188   // Blocks ABI:
2189   //   c) the flags field is set to either 0 if no helper functions are
2190   //      needed or BLOCK_BYREF_HAS_COPY_DISPOSE if they are,
2191   BlockFlags flags;
2192   if (helpers) flags |= BLOCK_BYREF_HAS_COPY_DISPOSE;
2193   if (ByRefHasLifetime) {
2194     if (HasByrefExtendedLayout) flags |= BLOCK_BYREF_LAYOUT_EXTENDED;
2195       else switch (ByrefLifetime) {
2196         case Qualifiers::OCL_Strong:
2197           flags |= BLOCK_BYREF_LAYOUT_STRONG;
2198           break;
2199         case Qualifiers::OCL_Weak:
2200           flags |= BLOCK_BYREF_LAYOUT_WEAK;
2201           break;
2202         case Qualifiers::OCL_ExplicitNone:
2203           flags |= BLOCK_BYREF_LAYOUT_UNRETAINED;
2204           break;
2205         case Qualifiers::OCL_None:
2206           if (!type->isObjCObjectPointerType() && !type->isBlockPointerType())
2207             flags |= BLOCK_BYREF_LAYOUT_NON_OBJECT;
2208           break;
2209         default:
2210           break;
2211       }
2212     if (CGM.getLangOpts().ObjCGCBitmapPrint) {
2213       printf("\n Inline flag for BYREF variable layout (%d):", flags.getBitMask());
2214       if (flags & BLOCK_BYREF_HAS_COPY_DISPOSE)
2215         printf(" BLOCK_BYREF_HAS_COPY_DISPOSE");
2216       if (flags & BLOCK_BYREF_LAYOUT_MASK) {
2217         BlockFlags ThisFlag(flags.getBitMask() & BLOCK_BYREF_LAYOUT_MASK);
2218         if (ThisFlag ==  BLOCK_BYREF_LAYOUT_EXTENDED)
2219           printf(" BLOCK_BYREF_LAYOUT_EXTENDED");
2220         if (ThisFlag ==  BLOCK_BYREF_LAYOUT_STRONG)
2221           printf(" BLOCK_BYREF_LAYOUT_STRONG");
2222         if (ThisFlag == BLOCK_BYREF_LAYOUT_WEAK)
2223           printf(" BLOCK_BYREF_LAYOUT_WEAK");
2224         if (ThisFlag == BLOCK_BYREF_LAYOUT_UNRETAINED)
2225           printf(" BLOCK_BYREF_LAYOUT_UNRETAINED");
2226         if (ThisFlag == BLOCK_BYREF_LAYOUT_NON_OBJECT)
2227           printf(" BLOCK_BYREF_LAYOUT_NON_OBJECT");
2228       }
2229       printf("\n");
2230     }
2231   }
2232   storeHeaderField(llvm::ConstantInt::get(IntTy, flags.getBitMask()),
2233                    getIntSize(), "byref.flags");
2234 
2235   CharUnits byrefSize = CGM.GetTargetTypeStoreSize(byrefType);
2236   V = llvm::ConstantInt::get(IntTy, byrefSize.getQuantity());
2237   storeHeaderField(V, getIntSize(), "byref.size");
2238 
2239   if (helpers) {
2240     storeHeaderField(helpers->CopyHelper, getPointerSize(),
2241                      "byref.copyHelper");
2242     storeHeaderField(helpers->DisposeHelper, getPointerSize(),
2243                      "byref.disposeHelper");
2244   }
2245 
2246   if (ByRefHasLifetime && HasByrefExtendedLayout) {
2247     auto layoutInfo = CGM.getObjCRuntime().BuildByrefLayout(CGM, type);
2248     storeHeaderField(layoutInfo, getPointerSize(), "byref.layout");
2249   }
2250 }
2251 
BuildBlockRelease(llvm::Value * V,BlockFieldFlags flags)2252 void CodeGenFunction::BuildBlockRelease(llvm::Value *V, BlockFieldFlags flags) {
2253   llvm::Value *F = CGM.getBlockObjectDispose();
2254   llvm::Value *args[] = {
2255     Builder.CreateBitCast(V, Int8PtrTy),
2256     llvm::ConstantInt::get(Int32Ty, flags.getBitMask())
2257   };
2258   EmitNounwindRuntimeCall(F, args); // FIXME: throwing destructors?
2259 }
2260 
2261 namespace {
2262   /// Release a __block variable.
2263   struct CallBlockRelease final : EHScopeStack::Cleanup {
2264     llvm::Value *Addr;
CallBlockRelease__anon125376670811::CallBlockRelease2265     CallBlockRelease(llvm::Value *Addr) : Addr(Addr) {}
2266 
Emit__anon125376670811::CallBlockRelease2267     void Emit(CodeGenFunction &CGF, Flags flags) override {
2268       // Should we be passing FIELD_IS_WEAK here?
2269       CGF.BuildBlockRelease(Addr, BLOCK_FIELD_IS_BYREF);
2270     }
2271   };
2272 } // end anonymous namespace
2273 
2274 /// Enter a cleanup to destroy a __block variable.  Note that this
2275 /// cleanup should be a no-op if the variable hasn't left the stack
2276 /// yet; if a cleanup is required for the variable itself, that needs
2277 /// to be done externally.
enterByrefCleanup(const AutoVarEmission & emission)2278 void CodeGenFunction::enterByrefCleanup(const AutoVarEmission &emission) {
2279   // We don't enter this cleanup if we're in pure-GC mode.
2280   if (CGM.getLangOpts().getGC() == LangOptions::GCOnly)
2281     return;
2282 
2283   EHStack.pushCleanup<CallBlockRelease>(NormalAndEHCleanup,
2284                                         emission.Addr.getPointer());
2285 }
2286 
2287 /// Adjust the declaration of something from the blocks API.
configureBlocksRuntimeObject(CodeGenModule & CGM,llvm::Constant * C)2288 static void configureBlocksRuntimeObject(CodeGenModule &CGM,
2289                                          llvm::Constant *C) {
2290   auto *GV = cast<llvm::GlobalValue>(C->stripPointerCasts());
2291 
2292   if (CGM.getTarget().getTriple().isOSBinFormatCOFF()) {
2293     IdentifierInfo &II = CGM.getContext().Idents.get(C->getName());
2294     TranslationUnitDecl *TUDecl = CGM.getContext().getTranslationUnitDecl();
2295     DeclContext *DC = TranslationUnitDecl::castToDeclContext(TUDecl);
2296 
2297     assert((isa<llvm::Function>(C->stripPointerCasts()) ||
2298             isa<llvm::GlobalVariable>(C->stripPointerCasts())) &&
2299            "expected Function or GlobalVariable");
2300 
2301     const NamedDecl *ND = nullptr;
2302     for (const auto &Result : DC->lookup(&II))
2303       if ((ND = dyn_cast<FunctionDecl>(Result)) ||
2304           (ND = dyn_cast<VarDecl>(Result)))
2305         break;
2306 
2307     // TODO: support static blocks runtime
2308     if (GV->isDeclaration() && (!ND || !ND->hasAttr<DLLExportAttr>())) {
2309       GV->setDLLStorageClass(llvm::GlobalValue::DLLImportStorageClass);
2310       GV->setLinkage(llvm::GlobalValue::ExternalLinkage);
2311     } else {
2312       GV->setDLLStorageClass(llvm::GlobalValue::DLLExportStorageClass);
2313       GV->setLinkage(llvm::GlobalValue::ExternalLinkage);
2314     }
2315   }
2316 
2317   if (!CGM.getLangOpts().BlocksRuntimeOptional)
2318     return;
2319 
2320   if (GV->isDeclaration() && GV->hasExternalLinkage())
2321     GV->setLinkage(llvm::GlobalValue::ExternalWeakLinkage);
2322 }
2323 
getBlockObjectDispose()2324 llvm::Constant *CodeGenModule::getBlockObjectDispose() {
2325   if (BlockObjectDispose)
2326     return BlockObjectDispose;
2327 
2328   llvm::Type *args[] = { Int8PtrTy, Int32Ty };
2329   llvm::FunctionType *fty
2330     = llvm::FunctionType::get(VoidTy, args, false);
2331   BlockObjectDispose = CreateRuntimeFunction(fty, "_Block_object_dispose");
2332   configureBlocksRuntimeObject(*this, BlockObjectDispose);
2333   return BlockObjectDispose;
2334 }
2335 
getBlockObjectAssign()2336 llvm::Constant *CodeGenModule::getBlockObjectAssign() {
2337   if (BlockObjectAssign)
2338     return BlockObjectAssign;
2339 
2340   llvm::Type *args[] = { Int8PtrTy, Int8PtrTy, Int32Ty };
2341   llvm::FunctionType *fty
2342     = llvm::FunctionType::get(VoidTy, args, false);
2343   BlockObjectAssign = CreateRuntimeFunction(fty, "_Block_object_assign");
2344   configureBlocksRuntimeObject(*this, BlockObjectAssign);
2345   return BlockObjectAssign;
2346 }
2347 
getNSConcreteGlobalBlock()2348 llvm::Constant *CodeGenModule::getNSConcreteGlobalBlock() {
2349   if (NSConcreteGlobalBlock)
2350     return NSConcreteGlobalBlock;
2351 
2352   NSConcreteGlobalBlock = GetOrCreateLLVMGlobal("_NSConcreteGlobalBlock",
2353                                                 Int8PtrTy->getPointerTo(),
2354                                                 nullptr);
2355   configureBlocksRuntimeObject(*this, NSConcreteGlobalBlock);
2356   return NSConcreteGlobalBlock;
2357 }
2358 
getNSConcreteStackBlock()2359 llvm::Constant *CodeGenModule::getNSConcreteStackBlock() {
2360   if (NSConcreteStackBlock)
2361     return NSConcreteStackBlock;
2362 
2363   NSConcreteStackBlock = GetOrCreateLLVMGlobal("_NSConcreteStackBlock",
2364                                                Int8PtrTy->getPointerTo(),
2365                                                nullptr);
2366   configureBlocksRuntimeObject(*this, NSConcreteStackBlock);
2367   return NSConcreteStackBlock;
2368 }
2369