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, NumBytesAtAlign8;
44 
45 public:
46   TypeLocBuilder()
47       : Buffer(InlineBuffer), Capacity(InlineCapacity), Index(InlineCapacity),
48         NumBytesAtAlign4(0), NumBytesAtAlign8(0) {}
49 
50   ~TypeLocBuilder() {
51     if (Buffer != InlineBuffer)
52       delete[] Buffer;
53   }
54 
55   /// Ensures that this buffer has at least as much capacity as described.
56   void reserve(size_t Requested) {
57     if (Requested > Capacity)
58       // For now, match the request exactly.
59       grow(Requested);
60   }
61 
62   /// Pushes a copy of the given TypeLoc onto this builder.  The builder
63   /// must be empty for this to work.
64   void pushFullCopy(TypeLoc L);
65 
66   /// Pushes space for a typespec TypeLoc.  Invalidates any TypeLocs
67   /// previously retrieved from this builder.
68   TypeSpecTypeLoc pushTypeSpec(QualType T) {
69     size_t LocalSize = TypeSpecTypeLoc::LocalDataSize;
70     unsigned LocalAlign = TypeSpecTypeLoc::LocalDataAlignment;
71     return pushImpl(T, LocalSize, LocalAlign).castAs<TypeSpecTypeLoc>();
72   }
73 
74   /// Resets this builder to the newly-initialized state.
75   void clear() {
76 #ifndef NDEBUG
77     LastTy = QualType();
78 #endif
79     Index = Capacity;
80     NumBytesAtAlign4 = NumBytesAtAlign8 = 0;
81   }
82 
83   /// Tell the TypeLocBuilder that the type it is storing has been
84   /// modified in some safe way that doesn't affect type-location information.
85   void TypeWasModifiedSafely(QualType T) {
86 #ifndef NDEBUG
87     LastTy = T;
88 #endif
89   }
90 
91   /// Pushes space for a new TypeLoc of the given type.  Invalidates
92   /// any TypeLocs previously retrieved from this builder.
93   template <class TyLocType> TyLocType push(QualType T) {
94     TyLocType Loc = TypeLoc(T, nullptr).castAs<TyLocType>();
95     size_t LocalSize = Loc.getLocalDataSize();
96     unsigned LocalAlign = Loc.getLocalDataAlignment();
97     return pushImpl(T, LocalSize, LocalAlign).castAs<TyLocType>();
98   }
99 
100   /// Creates a TypeSourceInfo for the given type.
101   TypeSourceInfo *getTypeSourceInfo(ASTContext& Context, QualType T) {
102 #ifndef NDEBUG
103     assert(T == LastTy && "type doesn't match last type pushed!");
104 #endif
105 
106     size_t FullDataSize = Capacity - Index;
107     TypeSourceInfo *DI = Context.CreateTypeSourceInfo(T, FullDataSize);
108     memcpy(DI->getTypeLoc().getOpaqueData(), &Buffer[Index], FullDataSize);
109     return DI;
110   }
111 
112   /// Copies the type-location information to the given AST context and
113   /// returns a \c TypeLoc referring into the AST context.
114   TypeLoc getTypeLocInContext(ASTContext &Context, QualType T) {
115 #ifndef NDEBUG
116     assert(T == LastTy && "type doesn't match last type pushed!");
117 #endif
118 
119     size_t FullDataSize = Capacity - Index;
120     void *Mem = Context.Allocate(FullDataSize);
121     memcpy(Mem, &Buffer[Index], FullDataSize);
122     return TypeLoc(T, Mem);
123   }
124 
125 private:
126 
127   TypeLoc pushImpl(QualType T, size_t LocalSize, unsigned LocalAlignment);
128 
129   /// Grow to the given capacity.
130   void grow(size_t NewCapacity);
131 
132   /// Retrieve a temporary TypeLoc that refers into this \c TypeLocBuilder
133   /// object.
134   ///
135   /// The resulting \c TypeLoc should only be used so long as the
136   /// \c TypeLocBuilder is active and has not had more type information
137   /// pushed into it.
138   TypeLoc getTemporaryTypeLoc(QualType T) {
139 #ifndef NDEBUG
140     assert(LastTy == T && "type doesn't match last type pushed!");
141 #endif
142     return TypeLoc(T, &Buffer[Index]);
143   }
144 };
145 
146 }
147 
148 #endif
149