clang/lib/CodeGen/CGBlocks.h

   1 //===-- CGBlocks.h - state for LLVM CodeGen for blocks ----------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This is the internal state used for llvm translation for block literals.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_CLANG_LIB_CODEGEN_CGBLOCKS_H
  14 #define LLVM_CLANG_LIB_CODEGEN_CGBLOCKS_H
  15
  16 #include "CGBuilder.h"
  17 #include "CGCall.h"
  18 #include "CGValue.h"
  19 #include "CodeGenFunction.h"
  20 #include "CodeGenTypes.h"
  21 #include "clang/AST/CharUnits.h"
  22 #include "clang/AST/Expr.h"
  23 #include "clang/AST/ExprCXX.h"
  24 #include "clang/AST/ExprObjC.h"
  25 #include "clang/AST/Type.h"
  26 #include "clang/Basic/TargetInfo.h"
  27
  28 namespace llvm {
  29 class Value;
  30 }
  31
  32 namespace clang {
  33 namespace CodeGen {
  34
  35 class CGBlockInfo;
  36
  37 // Flags stored in __block variables.
  38 enum BlockByrefFlags {
  39   BLOCK_BYREF_HAS_COPY_DISPOSE         = (1   << 25), // compiler
  40   BLOCK_BYREF_LAYOUT_MASK              = (0xF << 28), // compiler
  41   BLOCK_BYREF_LAYOUT_EXTENDED          = (1   << 28),
  42   BLOCK_BYREF_LAYOUT_NON_OBJECT        = (2   << 28),
  43   BLOCK_BYREF_LAYOUT_STRONG            = (3   << 28),
  44   BLOCK_BYREF_LAYOUT_WEAK              = (4   << 28),
  45   BLOCK_BYREF_LAYOUT_UNRETAINED        = (5   << 28)
  46 };
  47
  48 enum BlockLiteralFlags {
  49   BLOCK_IS_NOESCAPE      =  (1 << 23),
  50   BLOCK_HAS_COPY_DISPOSE =  (1 << 25),
  51   BLOCK_HAS_CXX_OBJ =       (1 << 26),
  52   BLOCK_IS_GLOBAL =         (1 << 28),
  53   BLOCK_USE_STRET =         (1 << 29),
  54   BLOCK_HAS_SIGNATURE  =    (1 << 30),
  55   BLOCK_HAS_EXTENDED_LAYOUT = (1u << 31)
  56 };
  57 class BlockFlags {
  58   uint32_t flags;
  59
  60 public:
  61   BlockFlags(uint32_t flags) : flags(flags) {}
  62   BlockFlags() : flags(0) {}
  63   BlockFlags(BlockLiteralFlags flag) : flags(flag) {}
  64   BlockFlags(BlockByrefFlags flag) : flags(flag) {}
  65
  66   uint32_t getBitMask() const { return flags; }
  67   bool empty() const { return flags == 0; }
  68
  69   friend BlockFlags operator|(BlockFlags l, BlockFlags r) {
  70     return BlockFlags(l.flags | r.flags);
  71   }
  72   friend BlockFlags &operator|=(BlockFlags &l, BlockFlags r) {
  73     l.flags |= r.flags;
  74     return l;
  75   }
  76   friend bool operator&(BlockFlags l, BlockFlags r) {
  77     return (l.flags & r.flags);
  78   }
  79   bool operator==(BlockFlags r) {
  80     return (flags == r.flags);
  81   }
  82 };
  83 inline BlockFlags operator|(BlockLiteralFlags l, BlockLiteralFlags r) {
  84   return BlockFlags(l) | BlockFlags(r);
  85 }
  86
  87 enum BlockFieldFlag_t {
  88   BLOCK_FIELD_IS_OBJECT   = 0x03,  /* id, NSObject, __attribute__((NSObject)),
  89                                     block, ... */
  90   BLOCK_FIELD_IS_BLOCK    = 0x07,  /* a block variable */
  91
  92   BLOCK_FIELD_IS_BYREF    = 0x08,  /* the on stack structure holding the __block
  93                                     variable */
  94   BLOCK_FIELD_IS_WEAK     = 0x10,  /* declared __weak, only used in byref copy
  95                                     helpers */
  96   BLOCK_FIELD_IS_ARC      = 0x40,  /* field has ARC-specific semantics */
  97   BLOCK_BYREF_CALLER      = 128,   /* called from __block (byref) copy/dispose
  98                                       support routines */
  99   BLOCK_BYREF_CURRENT_MAX = 256
 100 };
 101
 102 class BlockFieldFlags {
 103   uint32_t flags;
 104
 105   BlockFieldFlags(uint32_t flags) : flags(flags) {}
 106 public:
 107   BlockFieldFlags() : flags(0) {}
 108   BlockFieldFlags(BlockFieldFlag_t flag) : flags(flag) {}
 109
 110   uint32_t getBitMask() const { return flags; }
 111   bool empty() const { return flags == 0; }
 112
 113   /// Answers whether the flags indicate that this field is an object
 114   /// or block pointer that requires _Block_object_assign/dispose.
 115   bool isSpecialPointer() const { return flags & BLOCK_FIELD_IS_OBJECT; }
 116
 117   friend BlockFieldFlags operator|(BlockFieldFlags l, BlockFieldFlags r) {
 118     return BlockFieldFlags(l.flags | r.flags);
 119   }
 120   friend BlockFieldFlags &operator|=(BlockFieldFlags &l, BlockFieldFlags r) {
 121     l.flags |= r.flags;
 122     return l;
 123   }
 124   friend bool operator&(BlockFieldFlags l, BlockFieldFlags r) {
 125     return (l.flags & r.flags);
 126   }
 127   bool operator==(BlockFieldFlags Other) const {
 128     return flags == Other.flags;
 129   }
 130 };
 131 inline BlockFieldFlags operator|(BlockFieldFlag_t l, BlockFieldFlag_t r) {
 132   return BlockFieldFlags(l) | BlockFieldFlags(r);
 133 }
 134
 135 /// Information about the layout of a __block variable.
 136 class BlockByrefInfo {
 137 public:
 138   llvm::StructType *Type;
 139   unsigned FieldIndex;
 140   CharUnits ByrefAlignment;
 141   CharUnits FieldOffset;
 142 };
 143
 144 /// Represents a type of copy/destroy operation that should be performed for an
 145 /// entity that's captured by a block.
 146 enum class BlockCaptureEntityKind {
 147   None,
 148   CXXRecord, // Copy or destroy
 149   ARCWeak,
 150   ARCStrong,
 151   NonTrivialCStruct,
 152   BlockObject, // Assign or release
 153 };
 154
 155 /// CGBlockInfo - Information to generate a block literal.
 156 class CGBlockInfo {
 157 public:
 158   /// Name - The name of the block, kindof.
 159   StringRef Name;
 160
 161   /// The field index of 'this' within the block, if there is one.
 162   unsigned CXXThisIndex;
 163
 164   class Capture {
 165     uintptr_t Data;
 166     EHScopeStack::stable_iterator Cleanup;
 167     CharUnits::QuantityType Offset;
 168
 169     /// Type of the capture field. Normally, this is identical to the type of
 170     /// the capture's VarDecl, but can be different if there is an enclosing
 171     /// lambda.
 172     QualType FieldType;
 173
 174   public:
 175     bool isIndex() const { return (Data & 1) != 0; }
 176     bool isConstant() const { return !isIndex(); }
 177
 178     unsigned getIndex() const {
 179       assert(isIndex());
 180       return Data >> 1;
 181     }
 182     CharUnits getOffset() const {
 183       assert(isIndex());
 184       return CharUnits::fromQuantity(Offset);
 185     }
 186     EHScopeStack::stable_iterator getCleanup() const {
 187       assert(isIndex());
 188       return Cleanup;
 189     }
 190     void setCleanup(EHScopeStack::stable_iterator cleanup) {
 191       assert(isIndex());
 192       Cleanup = cleanup;
 193     }
 194
 195     llvm::Value *getConstant() const {
 196       assert(isConstant());
 197       return reinterpret_cast<llvm::Value*>(Data);
 198     }
 199
 200     QualType fieldType() const {
 201       return FieldType;
 202     }
 203
 204     static Capture
 205     makeIndex(unsigned index, CharUnits offset, QualType FieldType,
 206               BlockCaptureEntityKind CopyKind, BlockFieldFlags CopyFlags,
 207               BlockCaptureEntityKind DisposeKind, BlockFieldFlags DisposeFlags,
 208               const BlockDecl::Capture *Cap) {
 209       Capture v;
 210       v.Data = (index << 1) | 1;
 211       v.Offset = offset.getQuantity();
 212       v.FieldType = FieldType;
 213       v.CopyKind = CopyKind;
 214       v.CopyFlags = CopyFlags;
 215       v.DisposeKind = DisposeKind;
 216       v.DisposeFlags = DisposeFlags;
 217       v.Cap = Cap;
 218       return v;
 219     }
 220
 221     static Capture makeConstant(llvm::Value *value,
 222                                 const BlockDecl::Capture *Cap) {
 223       Capture v;
 224       v.Data = reinterpret_cast<uintptr_t>(value);
 225       v.Cap = Cap;
 226       return v;
 227     }
 228
 229     bool isConstantOrTrivial() const {
 230       return CopyKind == BlockCaptureEntityKind::None &&
 231              DisposeKind == BlockCaptureEntityKind::None;
 232     }
 233
 234     BlockCaptureEntityKind CopyKind = BlockCaptureEntityKind::None,
 235                            DisposeKind = BlockCaptureEntityKind::None;
 236     BlockFieldFlags CopyFlags, DisposeFlags;
 237     const BlockDecl::Capture *Cap;
 238   };
 239
 240   /// CanBeGlobal - True if the block can be global, i.e. it has
 241   /// no non-constant captures.
 242   bool CanBeGlobal : 1;
 243
 244   /// True if the block has captures that would necessitate custom copy or
 245   /// dispose helper functions if the block were escaping.
 246   bool NeedsCopyDispose : 1;
 247
 248   /// Indicates whether the block is non-escaping.
 249   bool NoEscape : 1;
 250
 251   /// HasCXXObject - True if the block's custom copy/dispose functions
 252   /// need to be run even in GC mode.
 253   bool HasCXXObject : 1;
 254
 255   /// UsesStret : True if the block uses an stret return.  Mutable
 256   /// because it gets set later in the block-creation process.
 257   mutable bool UsesStret : 1;
 258
 259   /// HasCapturedVariableLayout : True if block has captured variables
 260   /// and their layout meta-data has been generated.
 261   bool HasCapturedVariableLayout : 1;
 262
 263   /// Indicates whether an object of a non-external C++ class is captured. This
 264   /// bit is used to determine the linkage of the block copy/destroy helper
 265   /// functions.
 266   bool CapturesNonExternalType : 1;
 267
 268   /// Mapping from variables to pointers to captures in SortedCaptures.
 269   llvm::DenseMap<const VarDecl *, Capture *> Captures;
 270
 271   /// The block's captures. Non-constant captures are sorted by their offsets.
 272   llvm::SmallVector<Capture, 4> SortedCaptures;
 273
 274   Address LocalAddress;
 275   llvm::StructType *StructureType;
 276   const BlockDecl *Block;
 277   const BlockExpr *BlockExpression;
 278   CharUnits BlockSize;
 279   CharUnits BlockAlign;
 280   CharUnits CXXThisOffset;
 281
 282   // Offset of the gap caused by block header having a smaller
 283   // alignment than the alignment of the block descriptor. This
 284   // is the gap offset before the first capturued field.
 285   CharUnits BlockHeaderForcedGapOffset;
 286   // Gap size caused by aligning first field after block header.
 287   // This could be zero if no forced alignment is required.
 288   CharUnits BlockHeaderForcedGapSize;
 289
 290   void buildCaptureMap() {
 291     for (auto &C : SortedCaptures)
 292       Captures[C.Cap->getVariable()] = &C;
 293   }
 294
 295   const Capture &getCapture(const VarDecl *var) const {
 296     return const_cast<CGBlockInfo*>(this)->getCapture(var);
 297   }
 298   Capture &getCapture(const VarDecl *var) {
 299     auto it = Captures.find(var);
 300     assert(it != Captures.end() && "no entry for variable!");
 301     return *it->second;
 302   }
 303
 304   const BlockDecl *getBlockDecl() const { return Block; }
 305   const BlockExpr *getBlockExpr() const {
 306     assert(BlockExpression);
 307     assert(BlockExpression->getBlockDecl() == Block);
 308     return BlockExpression;
 309   }
 310
 311   CGBlockInfo(const BlockDecl *blockDecl, StringRef Name);
 312 };
 313
 314 }  // end namespace CodeGen
 315 }  // end namespace clang
 316
 317 #endif