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      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 #include "llvm/IR/Module.h"
     29 
     30 namespace llvm {
     31 class Module;
     32 class Constant;
     33 class Function;
     34 class GlobalValue;
     35 class DataLayout;
     36 class FunctionType;
     37 class PointerType;
     38 class Value;
     39 class LLVMContext;
     40 }
     41 
     42 namespace clang {
     43 
     44 namespace CodeGen {
     45 
     46 class CodeGenModule;
     47 class CGBlockInfo;
     48 
     49 // Flags stored in __block variables.
     50 enum BlockByrefFlags {
     51   BLOCK_BYREF_HAS_COPY_DISPOSE         = (1   << 25), // compiler
     52   BLOCK_BYREF_LAYOUT_MASK              = (0xF << 28), // compiler
     53   BLOCK_BYREF_LAYOUT_EXTENDED          = (1   << 28),
     54   BLOCK_BYREF_LAYOUT_NON_OBJECT        = (2   << 28),
     55   BLOCK_BYREF_LAYOUT_STRONG            = (3   << 28),
     56   BLOCK_BYREF_LAYOUT_WEAK              = (4   << 28),
     57   BLOCK_BYREF_LAYOUT_UNRETAINED        = (5   << 28)
     58 };
     59 
     60 enum BlockLiteralFlags {
     61   BLOCK_HAS_COPY_DISPOSE =  (1 << 25),
     62   BLOCK_HAS_CXX_OBJ =       (1 << 26),
     63   BLOCK_IS_GLOBAL =         (1 << 28),
     64   BLOCK_USE_STRET =         (1 << 29),
     65   BLOCK_HAS_SIGNATURE  =    (1 << 30),
     66   BLOCK_HAS_EXTENDED_LAYOUT = (1 << 31)
     67 };
     68 class BlockFlags {
     69   uint32_t flags;
     70 
     71 public:
     72   BlockFlags(uint32_t flags) : flags(flags) {}
     73   BlockFlags() : flags(0) {}
     74   BlockFlags(BlockLiteralFlags flag) : flags(flag) {}
     75   BlockFlags(BlockByrefFlags flag) : flags(flag) {}
     76 
     77   uint32_t getBitMask() const { return flags; }
     78   bool empty() const { return flags == 0; }
     79 
     80   friend BlockFlags operator|(BlockFlags l, BlockFlags r) {
     81     return BlockFlags(l.flags | r.flags);
     82   }
     83   friend BlockFlags &operator|=(BlockFlags &l, BlockFlags r) {
     84     l.flags |= r.flags;
     85     return l;
     86   }
     87   friend bool operator&(BlockFlags l, BlockFlags r) {
     88     return (l.flags & r.flags);
     89   }
     90   bool operator==(BlockFlags r) {
     91     return (flags == r.flags);
     92   }
     93 };
     94 inline BlockFlags operator|(BlockLiteralFlags l, BlockLiteralFlags r) {
     95   return BlockFlags(l) | BlockFlags(r);
     96 }
     97 
     98 enum BlockFieldFlag_t {
     99   BLOCK_FIELD_IS_OBJECT   = 0x03,  /* id, NSObject, __attribute__((NSObject)),
    100                                     block, ... */
    101   BLOCK_FIELD_IS_BLOCK    = 0x07,  /* a block variable */
    102 
    103   BLOCK_FIELD_IS_BYREF    = 0x08,  /* the on stack structure holding the __block
    104                                     variable */
    105   BLOCK_FIELD_IS_WEAK     = 0x10,  /* declared __weak, only used in byref copy
    106                                     helpers */
    107   BLOCK_FIELD_IS_ARC      = 0x40,  /* field has ARC-specific semantics */
    108   BLOCK_BYREF_CALLER      = 128,   /* called from __block (byref) copy/dispose
    109                                       support routines */
    110   BLOCK_BYREF_CURRENT_MAX = 256
    111 };
    112 
    113 class BlockFieldFlags {
    114   uint32_t flags;
    115 
    116   BlockFieldFlags(uint32_t flags) : flags(flags) {}
    117 public:
    118   BlockFieldFlags() : flags(0) {}
    119   BlockFieldFlags(BlockFieldFlag_t flag) : flags(flag) {}
    120 
    121   uint32_t getBitMask() const { return flags; }
    122   bool empty() const { return flags == 0; }
    123 
    124   /// Answers whether the flags indicate that this field is an object
    125   /// or block pointer that requires _Block_object_assign/dispose.
    126   bool isSpecialPointer() const { return flags & BLOCK_FIELD_IS_OBJECT; }
    127 
    128   friend BlockFieldFlags operator|(BlockFieldFlags l, BlockFieldFlags r) {
    129     return BlockFieldFlags(l.flags | r.flags);
    130   }
    131   friend BlockFieldFlags &operator|=(BlockFieldFlags &l, BlockFieldFlags r) {
    132     l.flags |= r.flags;
    133     return l;
    134   }
    135   friend bool operator&(BlockFieldFlags l, BlockFieldFlags r) {
    136     return (l.flags & r.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   public:
    167     bool isIndex() const { return (Data & 1) != 0; }
    168     bool isConstant() const { return !isIndex(); }
    169 
    170     unsigned getIndex() const {
    171       assert(isIndex());
    172       return Data >> 1;
    173     }
    174     CharUnits getOffset() const {
    175       assert(isIndex());
    176       return CharUnits::fromQuantity(Offset);
    177     }
    178     EHScopeStack::stable_iterator getCleanup() const {
    179       assert(isIndex());
    180       return Cleanup;
    181     }
    182     void setCleanup(EHScopeStack::stable_iterator cleanup) {
    183       assert(isIndex());
    184       Cleanup = cleanup;
    185     }
    186 
    187     llvm::Value *getConstant() const {
    188       assert(isConstant());
    189       return reinterpret_cast<llvm::Value*>(Data);
    190     }
    191 
    192     static Capture makeIndex(unsigned index, CharUnits offset) {
    193       Capture v;
    194       v.Data = (index << 1) | 1;
    195       v.Offset = offset.getQuantity();
    196       return v;
    197     }
    198 
    199     static Capture makeConstant(llvm::Value *value) {
    200       Capture v;
    201       v.Data = reinterpret_cast<uintptr_t>(value);
    202       return v;
    203     }
    204   };
    205 
    206   /// CanBeGlobal - True if the block can be global, i.e. it has
    207   /// no non-constant captures.
    208   bool CanBeGlobal : 1;
    209 
    210   /// True if the block needs a custom copy or dispose function.
    211   bool NeedsCopyDispose : 1;
    212 
    213   /// HasCXXObject - True if the block's custom copy/dispose functions
    214   /// need to be run even in GC mode.
    215   bool HasCXXObject : 1;
    216 
    217   /// UsesStret : True if the block uses an stret return.  Mutable
    218   /// because it gets set later in the block-creation process.
    219   mutable bool UsesStret : 1;
    220 
    221   /// HasCapturedVariableLayout : True if block has captured variables
    222   /// and their layout meta-data has been generated.
    223   bool HasCapturedVariableLayout : 1;
    224 
    225   /// The mapping of allocated indexes within the block.
    226   llvm::DenseMap<const VarDecl*, Capture> Captures;
    227 
    228   Address LocalAddress;
    229   llvm::StructType *StructureType;
    230   const BlockDecl *Block;
    231   const BlockExpr *BlockExpression;
    232   CharUnits BlockSize;
    233   CharUnits BlockAlign;
    234   CharUnits CXXThisOffset;
    235 
    236   // Offset of the gap caused by block header having a smaller
    237   // alignment than the alignment of the block descriptor. This
    238   // is the gap offset before the first capturued field.
    239   CharUnits BlockHeaderForcedGapOffset;
    240   // Gap size caused by aligning first field after block header.
    241   // This could be zero if no forced alignment is required.
    242   CharUnits BlockHeaderForcedGapSize;
    243 
    244   /// An instruction which dominates the full-expression that the
    245   /// block is inside.
    246   llvm::Instruction *DominatingIP;
    247 
    248   /// The next block in the block-info chain.  Invalid if this block
    249   /// info is not part of the CGF's block-info chain, which is true
    250   /// if it corresponds to a global block or a block whose expression
    251   /// has been encountered.
    252   CGBlockInfo *NextBlockInfo;
    253 
    254   const Capture &getCapture(const VarDecl *var) const {
    255     return const_cast<CGBlockInfo*>(this)->getCapture(var);
    256   }
    257   Capture &getCapture(const VarDecl *var) {
    258     llvm::DenseMap<const VarDecl*, Capture>::iterator
    259       it = Captures.find(var);
    260     assert(it != Captures.end() && "no entry for variable!");
    261     return it->second;
    262   }
    263 
    264   const BlockDecl *getBlockDecl() const { return Block; }
    265   const BlockExpr *getBlockExpr() const {
    266     assert(BlockExpression);
    267     assert(BlockExpression->getBlockDecl() == Block);
    268     return BlockExpression;
    269   }
    270 
    271   CGBlockInfo(const BlockDecl *blockDecl, StringRef Name);
    272 };
    273 
    274 }  // end namespace CodeGen
    275 }  // end namespace clang
    276 
    277 #endif
    278