1 //===-- CGBlocks.h - state for LLVM CodeGen for blocks ----------*- 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 is the internal state used for llvm translation for block literals.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_LIB_CODEGEN_CGBLOCKS_H
15 #define LLVM_CLANG_LIB_CODEGEN_CGBLOCKS_H
16 
17 #include "CGBuilder.h"
18 #include "CGCall.h"
19 #include "CGValue.h"
20 #include "CodeGenFunction.h"
21 #include "CodeGenTypes.h"
22 #include "clang/AST/CharUnits.h"
23 #include "clang/AST/Expr.h"
24 #include "clang/AST/ExprCXX.h"
25 #include "clang/AST/ExprObjC.h"
26 #include "clang/AST/Type.h"
27 #include "clang/Basic/TargetInfo.h"
28 
29 namespace llvm {
30 class Constant;
31 class Function;
32 class GlobalValue;
33 class DataLayout;
34 class FunctionType;
35 class PointerType;
36 class Value;
37 class LLVMContext;
38 }
39 
40 namespace clang {
41 namespace CodeGen {
42 
43 class CGBlockInfo;
44 
45 // Flags stored in __block variables.
46 enum BlockByrefFlags {
47   BLOCK_BYREF_HAS_COPY_DISPOSE         = (1   << 25), // compiler
48   BLOCK_BYREF_LAYOUT_MASK              = (0xF << 28), // compiler
49   BLOCK_BYREF_LAYOUT_EXTENDED          = (1   << 28),
50   BLOCK_BYREF_LAYOUT_NON_OBJECT        = (2   << 28),
51   BLOCK_BYREF_LAYOUT_STRONG            = (3   << 28),
52   BLOCK_BYREF_LAYOUT_WEAK              = (4   << 28),
53   BLOCK_BYREF_LAYOUT_UNRETAINED        = (5   << 28)
54 };
55 
56 enum BlockLiteralFlags {
57   BLOCK_IS_NOESCAPE      =  (1 << 23),
58   BLOCK_HAS_COPY_DISPOSE =  (1 << 25),
59   BLOCK_HAS_CXX_OBJ =       (1 << 26),
60   BLOCK_IS_GLOBAL =         (1 << 28),
61   BLOCK_USE_STRET =         (1 << 29),
62   BLOCK_HAS_SIGNATURE  =    (1 << 30),
63   BLOCK_HAS_EXTENDED_LAYOUT = (1u << 31)
64 };
65 class BlockFlags {
66   uint32_t flags;
67 
68 public:
BlockFlags(uint32_t flags)69   BlockFlags(uint32_t flags) : flags(flags) {}
BlockFlags()70   BlockFlags() : flags(0) {}
BlockFlags(BlockLiteralFlags flag)71   BlockFlags(BlockLiteralFlags flag) : flags(flag) {}
BlockFlags(BlockByrefFlags flag)72   BlockFlags(BlockByrefFlags flag) : flags(flag) {}
73 
getBitMask()74   uint32_t getBitMask() const { return flags; }
empty()75   bool empty() const { return flags == 0; }
76 
77   friend BlockFlags operator|(BlockFlags l, BlockFlags r) {
78     return BlockFlags(l.flags | r.flags);
79   }
80   friend BlockFlags &operator|=(BlockFlags &l, BlockFlags r) {
81     l.flags |= r.flags;
82     return l;
83   }
84   friend bool operator&(BlockFlags l, BlockFlags r) {
85     return (l.flags & r.flags);
86   }
87   bool operator==(BlockFlags r) {
88     return (flags == r.flags);
89   }
90 };
91 inline BlockFlags operator|(BlockLiteralFlags l, BlockLiteralFlags r) {
92   return BlockFlags(l) | BlockFlags(r);
93 }
94 
95 enum BlockFieldFlag_t {
96   BLOCK_FIELD_IS_OBJECT   = 0x03,  /* id, NSObject, __attribute__((NSObject)),
97                                     block, ... */
98   BLOCK_FIELD_IS_BLOCK    = 0x07,  /* a block variable */
99 
100   BLOCK_FIELD_IS_BYREF    = 0x08,  /* the on stack structure holding the __block
101                                     variable */
102   BLOCK_FIELD_IS_WEAK     = 0x10,  /* declared __weak, only used in byref copy
103                                     helpers */
104   BLOCK_FIELD_IS_ARC      = 0x40,  /* field has ARC-specific semantics */
105   BLOCK_BYREF_CALLER      = 128,   /* called from __block (byref) copy/dispose
106                                       support routines */
107   BLOCK_BYREF_CURRENT_MAX = 256
108 };
109 
110 class BlockFieldFlags {
111   uint32_t flags;
112 
BlockFieldFlags(uint32_t flags)113   BlockFieldFlags(uint32_t flags) : flags(flags) {}
114 public:
BlockFieldFlags()115   BlockFieldFlags() : flags(0) {}
BlockFieldFlags(BlockFieldFlag_t flag)116   BlockFieldFlags(BlockFieldFlag_t flag) : flags(flag) {}
117 
getBitMask()118   uint32_t getBitMask() const { return flags; }
empty()119   bool empty() const { return flags == 0; }
120 
121   /// Answers whether the flags indicate that this field is an object
122   /// or block pointer that requires _Block_object_assign/dispose.
isSpecialPointer()123   bool isSpecialPointer() const { return flags & BLOCK_FIELD_IS_OBJECT; }
124 
125   friend BlockFieldFlags operator|(BlockFieldFlags l, BlockFieldFlags r) {
126     return BlockFieldFlags(l.flags | r.flags);
127   }
128   friend BlockFieldFlags &operator|=(BlockFieldFlags &l, BlockFieldFlags r) {
129     l.flags |= r.flags;
130     return l;
131   }
132   friend bool operator&(BlockFieldFlags l, BlockFieldFlags r) {
133     return (l.flags & r.flags);
134   }
135   bool operator==(BlockFieldFlags Other) const {
136     return flags == Other.flags;
137   }
138 };
139 inline BlockFieldFlags operator|(BlockFieldFlag_t l, BlockFieldFlag_t r) {
140   return BlockFieldFlags(l) | BlockFieldFlags(r);
141 }
142 
143 /// Information about the layout of a __block variable.
144 class BlockByrefInfo {
145 public:
146   llvm::StructType *Type;
147   unsigned FieldIndex;
148   CharUnits ByrefAlignment;
149   CharUnits FieldOffset;
150 };
151 
152 /// CGBlockInfo - Information to generate a block literal.
153 class CGBlockInfo {
154 public:
155   /// Name - The name of the block, kindof.
156   StringRef Name;
157 
158   /// The field index of 'this' within the block, if there is one.
159   unsigned CXXThisIndex;
160 
161   class Capture {
162     uintptr_t Data;
163     EHScopeStack::stable_iterator Cleanup;
164     CharUnits::QuantityType Offset;
165 
166     /// Type of the capture field. Normally, this is identical to the type of
167     /// the capture's VarDecl, but can be different if there is an enclosing
168     /// lambda.
169     QualType FieldType;
170 
171   public:
isIndex()172     bool isIndex() const { return (Data & 1) != 0; }
isConstant()173     bool isConstant() const { return !isIndex(); }
174 
getIndex()175     unsigned getIndex() const {
176       assert(isIndex());
177       return Data >> 1;
178     }
getOffset()179     CharUnits getOffset() const {
180       assert(isIndex());
181       return CharUnits::fromQuantity(Offset);
182     }
getCleanup()183     EHScopeStack::stable_iterator getCleanup() const {
184       assert(isIndex());
185       return Cleanup;
186     }
setCleanup(EHScopeStack::stable_iterator cleanup)187     void setCleanup(EHScopeStack::stable_iterator cleanup) {
188       assert(isIndex());
189       Cleanup = cleanup;
190     }
191 
getConstant()192     llvm::Value *getConstant() const {
193       assert(isConstant());
194       return reinterpret_cast<llvm::Value*>(Data);
195     }
196 
fieldType()197     QualType fieldType() const {
198       return FieldType;
199     }
200 
makeIndex(unsigned index,CharUnits offset,QualType FieldType)201     static Capture makeIndex(unsigned index, CharUnits offset,
202                              QualType FieldType) {
203       Capture v;
204       v.Data = (index << 1) | 1;
205       v.Offset = offset.getQuantity();
206       v.FieldType = FieldType;
207       return v;
208     }
209 
makeConstant(llvm::Value * value)210     static Capture makeConstant(llvm::Value *value) {
211       Capture v;
212       v.Data = reinterpret_cast<uintptr_t>(value);
213       return v;
214     }
215   };
216 
217   /// CanBeGlobal - True if the block can be global, i.e. it has
218   /// no non-constant captures.
219   bool CanBeGlobal : 1;
220 
221   /// True if the block has captures that would necessitate custom copy or
222   /// dispose helper functions if the block were escaping.
223   bool NeedsCopyDispose : 1;
224 
225   /// HasCXXObject - True if the block's custom copy/dispose functions
226   /// need to be run even in GC mode.
227   bool HasCXXObject : 1;
228 
229   /// UsesStret : True if the block uses an stret return.  Mutable
230   /// because it gets set later in the block-creation process.
231   mutable bool UsesStret : 1;
232 
233   /// HasCapturedVariableLayout : True if block has captured variables
234   /// and their layout meta-data has been generated.
235   bool HasCapturedVariableLayout : 1;
236 
237   /// Indicates whether an object of a non-external C++ class is captured. This
238   /// bit is used to determine the linkage of the block copy/destroy helper
239   /// functions.
240   bool CapturesNonExternalType : 1;
241 
242   /// The mapping of allocated indexes within the block.
243   llvm::DenseMap<const VarDecl*, Capture> Captures;
244 
245   Address LocalAddress;
246   llvm::StructType *StructureType;
247   const BlockDecl *Block;
248   const BlockExpr *BlockExpression;
249   CharUnits BlockSize;
250   CharUnits BlockAlign;
251   CharUnits CXXThisOffset;
252 
253   // Offset of the gap caused by block header having a smaller
254   // alignment than the alignment of the block descriptor. This
255   // is the gap offset before the first capturued field.
256   CharUnits BlockHeaderForcedGapOffset;
257   // Gap size caused by aligning first field after block header.
258   // This could be zero if no forced alignment is required.
259   CharUnits BlockHeaderForcedGapSize;
260 
261   /// An instruction which dominates the full-expression that the
262   /// block is inside.
263   llvm::Instruction *DominatingIP;
264 
265   /// The next block in the block-info chain.  Invalid if this block
266   /// info is not part of the CGF's block-info chain, which is true
267   /// if it corresponds to a global block or a block whose expression
268   /// has been encountered.
269   CGBlockInfo *NextBlockInfo;
270 
getCapture(const VarDecl * var)271   const Capture &getCapture(const VarDecl *var) const {
272     return const_cast<CGBlockInfo*>(this)->getCapture(var);
273   }
getCapture(const VarDecl * var)274   Capture &getCapture(const VarDecl *var) {
275     llvm::DenseMap<const VarDecl*, Capture>::iterator
276       it = Captures.find(var);
277     assert(it != Captures.end() && "no entry for variable!");
278     return it->second;
279   }
280 
getBlockDecl()281   const BlockDecl *getBlockDecl() const { return Block; }
getBlockExpr()282   const BlockExpr *getBlockExpr() const {
283     assert(BlockExpression);
284     assert(BlockExpression->getBlockDecl() == Block);
285     return BlockExpression;
286   }
287 
288   CGBlockInfo(const BlockDecl *blockDecl, StringRef Name);
289 
290   // Indicates whether the block needs a custom copy or dispose function.
needsCopyDisposeHelpers()291   bool needsCopyDisposeHelpers() const {
292     return NeedsCopyDispose && !Block->doesNotEscape();
293   }
294 };
295 
296 }  // end namespace CodeGen
297 }  // end namespace clang
298 
299 #endif
300