clang  6.0.0svn
ConstantInitFuture.h
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1 //===- ConstantInitFuture.h - "Future" constant initializers ----*- 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 class defines the ConstantInitFuture class. This is split out
11 // from ConstantInitBuilder.h in order to allow APIs to work with it
12 // without having to include that entire header. This is particularly
13 // important because it is often useful to be able to default-construct
14 // a future in, say, a default argument.
15 //
16 //===----------------------------------------------------------------------===//
17 
18 #ifndef LLVM_CLANG_CODEGEN_CONSTANTINITFUTURE_H
19 #define LLVM_CLANG_CODEGEN_CONSTANTINITFUTURE_H
20 
21 #include "llvm/ADT/PointerUnion.h"
22 #include "llvm/IR/Constant.h"
23 
24 // Forward-declare ConstantInitBuilderBase and give it a
25 // PointerLikeTypeTraits specialization so that we can safely use it
26 // in a PointerUnion below.
27 namespace clang {
28 namespace CodeGen {
29 class ConstantInitBuilderBase;
30 }
31 }
32 namespace llvm {
33 template <>
36 
37  static inline void *getAsVoidPointer(T p) { return p; }
38  static inline T getFromVoidPointer(void *p) {return static_cast<T>(p);}
39  enum { NumLowBitsAvailable = 2 };
40 };
41 }
42 
43 namespace clang {
44 namespace CodeGen {
45 
46 /// A "future" for a completed constant initializer, which can be passed
47 /// around independently of any sub-builders (but not the original parent).
49  using PairTy = llvm::PointerUnion<ConstantInitBuilderBase*, llvm::Constant*>;
50 
51  PairTy Data;
52 
55 
56 public:
58 
59  /// A future can be explicitly created from a fixed initializer.
60  explicit ConstantInitFuture(llvm::Constant *initializer) : Data(initializer) {
61  assert(initializer && "creating null future");
62  }
63 
64  /// Is this future non-null?
65  explicit operator bool() const { return bool(Data); }
66 
67  /// Return the type of the initializer.
68  llvm::Type *getType() const;
69 
70  /// Abandon this initializer.
71  void abandon();
72 
73  /// Install the initializer into a global variable. This cannot
74  /// be called multiple times.
75  void installInGlobal(llvm::GlobalVariable *global);
76 
77  void *getOpaqueValue() const { return Data.getOpaqueValue(); }
78  static ConstantInitFuture getFromOpaqueValue(void *value) {
79  ConstantInitFuture result;
80  result.Data = PairTy::getFromOpaqueValue(value);
81  return result;
82  }
83  enum {
84  NumLowBitsAvailable =
86  };
87 };
88 
89 } // end namespace CodeGen
90 } // end namespace clang
91 
92 namespace llvm {
93 
94 template <>
97 
98  static inline void *getAsVoidPointer(T future) {
99  return future.getOpaqueValue();
100  }
101  static inline T getFromVoidPointer(void *p) {
102  return T::getFromOpaqueValue(p);
103  }
104  enum { NumLowBitsAvailable = T::NumLowBitsAvailable };
105 };
106 
107 } // end namespace llvm
108 
109 #endif
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The l-value was considered opaque, so the alignment was determined from a type.
ConstantInitFuture(llvm::Constant *initializer)
A future can be explicitly created from a fixed initializer.
A "future" for a completed constant initializer, which can be passed around independently of any sub-...
Dataflow Directional Tag Classes.
static ConstantInitFuture getFromOpaqueValue(void *value)