clang/lib/Sema/TypeLocBuilder.h

   1 //===--- TypeLocBuilder.h - Type Source Info collector ----------*- 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 file defines TypeLocBuilder, a class for building TypeLocs
  10 //  bottom-up.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_CLANG_LIB_SEMA_TYPELOCBUILDER_H
  15 #define LLVM_CLANG_LIB_SEMA_TYPELOCBUILDER_H
  16
  17 #include "clang/AST/ASTContext.h"
  18 #include "clang/AST/TypeLoc.h"
  19
  20 namespace clang {
  21
  22 class TypeLocBuilder {
  23   enum { InlineCapacity = 8 * sizeof(SourceLocation) };
  24
  25   /// The underlying location-data buffer.  Data grows from the end
  26   /// of the buffer backwards.
  27   char *Buffer;
  28
  29   /// The capacity of the current buffer.
  30   size_t Capacity;
  31
  32   /// The index of the first occupied byte in the buffer.
  33   size_t Index;
  34
  35 #ifndef NDEBUG
  36   /// The last type pushed on this builder.
  37   QualType LastTy;
  38 #endif
  39
  40   /// The inline buffer.
  41   enum { BufferMaxAlignment = alignof(void *) };
  42   alignas(BufferMaxAlignment) char InlineBuffer[InlineCapacity];
  43   unsigned NumBytesAtAlign4;
  44   bool AtAlign8;
  45
  46 public:
  47   TypeLocBuilder()
  48       : Buffer(InlineBuffer), Capacity(InlineCapacity), Index(InlineCapacity),
  49         NumBytesAtAlign4(0), AtAlign8(false) {}
  50
  51   ~TypeLocBuilder() {
  52     if (Buffer != InlineBuffer)
  53       delete[] Buffer;
  54   }
  55
  56   /// Ensures that this buffer has at least as much capacity as described.
  57   void reserve(size_t Requested) {
  58     if (Requested > Capacity)
  59       // For now, match the request exactly.
  60       grow(Requested);
  61   }
  62
  63   /// Pushes a copy of the given TypeLoc onto this builder.  The builder
  64   /// must be empty for this to work.
  65   void pushFullCopy(TypeLoc L);
  66
  67   /// Pushes space for a typespec TypeLoc.  Invalidates any TypeLocs
  68   /// previously retrieved from this builder.
  69   TypeSpecTypeLoc pushTypeSpec(QualType T) {
  70     size_t LocalSize = TypeSpecTypeLoc::LocalDataSize;
  71     unsigned LocalAlign = TypeSpecTypeLoc::LocalDataAlignment;
  72     return pushImpl(T, LocalSize, LocalAlign).castAs<TypeSpecTypeLoc>();
  73   }
  74
  75   /// Resets this builder to the newly-initialized state.
  76   void clear() {
  77 #ifndef NDEBUG
  78     LastTy = QualType();
  79 #endif
  80     Index = Capacity;
  81     NumBytesAtAlign4 = 0;
  82     AtAlign8 = false;
  83   }
  84
  85   /// Tell the TypeLocBuilder that the type it is storing has been
  86   /// modified in some safe way that doesn't affect type-location information.
  87   void TypeWasModifiedSafely(QualType T) {
  88 #ifndef NDEBUG
  89     LastTy = T;
  90 #endif
  91   }
  92
  93   /// Pushes space for a new TypeLoc of the given type.  Invalidates
  94   /// any TypeLocs previously retrieved from this builder.
  95   template <class TyLocType> TyLocType push(QualType T) {
  96     TyLocType Loc = TypeLoc(T, nullptr).castAs<TyLocType>();
  97     size_t LocalSize = Loc.getLocalDataSize();
  98     unsigned LocalAlign = Loc.getLocalDataAlignment();
  99     return pushImpl(T, LocalSize, LocalAlign).castAs<TyLocType>();
 100   }
 101
 102   /// Creates a TypeSourceInfo for the given type.
 103   TypeSourceInfo *getTypeSourceInfo(ASTContext& Context, QualType T) {
 104 #ifndef NDEBUG
 105     assert(T == LastTy && "type doesn't match last type pushed!");
 106 #endif
 107
 108     size_t FullDataSize = Capacity - Index;
 109     TypeSourceInfo *DI = Context.CreateTypeSourceInfo(T, FullDataSize);
 110     memcpy(DI->getTypeLoc().getOpaqueData(), &Buffer[Index], FullDataSize);
 111     return DI;
 112   }
 113
 114   /// Copies the type-location information to the given AST context and
 115   /// returns a \c TypeLoc referring into the AST context.
 116   TypeLoc getTypeLocInContext(ASTContext &Context, QualType T) {
 117 #ifndef NDEBUG
 118     assert(T == LastTy && "type doesn't match last type pushed!");
 119 #endif
 120
 121     size_t FullDataSize = Capacity - Index;
 122     void *Mem = Context.Allocate(FullDataSize);
 123     memcpy(Mem, &Buffer[Index], FullDataSize);
 124     return TypeLoc(T, Mem);
 125   }
 126
 127 private:
 128
 129   TypeLoc pushImpl(QualType T, size_t LocalSize, unsigned LocalAlignment);
 130
 131   /// Grow to the given capacity.
 132   void grow(size_t NewCapacity);
 133
 134   /// Retrieve a temporary TypeLoc that refers into this \c TypeLocBuilder
 135   /// object.
 136   ///
 137   /// The resulting \c TypeLoc should only be used so long as the
 138   /// \c TypeLocBuilder is active and has not had more type information
 139   /// pushed into it.
 140   TypeLoc getTemporaryTypeLoc(QualType T) {
 141 #ifndef NDEBUG
 142     assert(LastTy == T && "type doesn't match last type pushed!");
 143 #endif
 144     return TypeLoc(T, &Buffer[Index]);
 145   }
 146 };
 147
 148 }
 149
 150 #endif