1 | //===- ConstantInitFuture.h - "Future" constant initializers ----*- 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 class defines the ConstantInitFuture class. This is split out |
10 | // from ConstantInitBuilder.h in order to allow APIs to work with it |
11 | // without having to include that entire header. This is particularly |
12 | // important because it is often useful to be able to default-construct |
13 | // a future in, say, a default argument. |
14 | // |
15 | //===----------------------------------------------------------------------===// |
16 | |
17 | #ifndef LLVM_CLANG_CODEGEN_CONSTANTINITFUTURE_H |
18 | #define LLVM_CLANG_CODEGEN_CONSTANTINITFUTURE_H |
19 | |
20 | #include "llvm/ADT/PointerUnion.h" |
21 | #include "llvm/IR/Constant.h" |
22 | |
23 | // Forward-declare ConstantInitBuilderBase and give it a |
24 | // PointerLikeTypeTraits specialization so that we can safely use it |
25 | // in a PointerUnion below. |
26 | namespace clang { |
27 | namespace CodeGen { |
28 | class ConstantInitBuilderBase; |
29 | } |
30 | } |
31 | namespace llvm { |
32 | template <> |
33 | struct PointerLikeTypeTraits< ::clang::CodeGen::ConstantInitBuilderBase*> { |
34 | using T = ::clang::CodeGen::ConstantInitBuilderBase*; |
35 | |
36 | static inline void *getAsVoidPointer(T p) { return p; } |
37 | static inline T getFromVoidPointer(void *p) {return static_cast<T>(p);} |
38 | static constexpr int NumLowBitsAvailable = 2; |
39 | }; |
40 | } |
41 | |
42 | namespace clang { |
43 | namespace CodeGen { |
44 | |
45 | /// A "future" for a completed constant initializer, which can be passed |
46 | /// around independently of any sub-builders (but not the original parent). |
47 | class ConstantInitFuture { |
48 | using PairTy = llvm::PointerUnion<ConstantInitBuilderBase*, llvm::Constant*>; |
49 | |
50 | PairTy Data; |
51 | |
52 | friend class ConstantInitBuilderBase; |
53 | explicit ConstantInitFuture(ConstantInitBuilderBase *builder); |
54 | |
55 | public: |
56 | ConstantInitFuture() {} |
57 | |
58 | /// A future can be explicitly created from a fixed initializer. |
59 | explicit ConstantInitFuture(llvm::Constant *initializer) : Data(initializer) { |
60 | assert(initializer && "creating null future" ); |
61 | } |
62 | |
63 | /// Is this future non-null? |
64 | explicit operator bool() const { return bool(Data); } |
65 | |
66 | /// Return the type of the initializer. |
67 | llvm::Type *getType() const; |
68 | |
69 | /// Abandon this initializer. |
70 | void abandon(); |
71 | |
72 | /// Install the initializer into a global variable. This cannot |
73 | /// be called multiple times. |
74 | void installInGlobal(llvm::GlobalVariable *global); |
75 | |
76 | void *getOpaqueValue() const { return Data.getOpaqueValue(); } |
77 | static ConstantInitFuture getFromOpaqueValue(void *value) { |
78 | ConstantInitFuture result; |
79 | result.Data = PairTy::getFromOpaqueValue(VP: value); |
80 | return result; |
81 | } |
82 | static constexpr int NumLowBitsAvailable = |
83 | llvm::PointerLikeTypeTraits<PairTy>::NumLowBitsAvailable; |
84 | }; |
85 | |
86 | } // end namespace CodeGen |
87 | } // end namespace clang |
88 | |
89 | namespace llvm { |
90 | |
91 | template <> |
92 | struct PointerLikeTypeTraits< ::clang::CodeGen::ConstantInitFuture> { |
93 | using T = ::clang::CodeGen::ConstantInitFuture; |
94 | |
95 | static inline void *getAsVoidPointer(T future) { |
96 | return future.getOpaqueValue(); |
97 | } |
98 | static inline T getFromVoidPointer(void *p) { |
99 | return T::getFromOpaqueValue(value: p); |
100 | } |
101 | static constexpr int NumLowBitsAvailable = T::NumLowBitsAvailable; |
102 | }; |
103 | |
104 | } // end namespace llvm |
105 | |
106 | #endif |
107 | |