1 //===-- llvm/GlobalObject.h - Class to represent global objects -*- 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 represents an independent object. That is, a function or a global
10 // variable, but not an alias.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_IR_GLOBALOBJECT_H
15 #define LLVM_IR_GLOBALOBJECT_H
16 
17 #include "llvm/ADT/StringRef.h"
18 #include "llvm/IR/GlobalValue.h"
19 #include "llvm/IR/Value.h"
20 #include "llvm/Support/Alignment.h"
21 
22 namespace llvm {
23 
24 class Comdat;
25 class Metadata;
26 
27 class GlobalObject : public GlobalValue {
28 public:
29   // VCallVisibility - values for visibility metadata attached to vtables. This
30   // describes the scope in which a virtual call could end up being dispatched
31   // through this vtable.
32   enum VCallVisibility {
33     // Type is potentially visible to external code.
34     VCallVisibilityPublic = 0,
35     // Type is only visible to code which will be in the current Module after
36     // LTO internalization.
37     VCallVisibilityLinkageUnit = 1,
38     // Type is only visible to code in the current Module.
39     VCallVisibilityTranslationUnit = 2,
40   };
41 
42 protected:
43   GlobalObject(Type *Ty, ValueTy VTy, Use *Ops, unsigned NumOps,
44                LinkageTypes Linkage, const Twine &Name,
45                unsigned AddressSpace = 0)
GlobalValue(Ty,VTy,Ops,NumOps,Linkage,Name,AddressSpace)46       : GlobalValue(Ty, VTy, Ops, NumOps, Linkage, Name, AddressSpace) {
47     setGlobalValueSubClassData(0);
48   }
49   ~GlobalObject();
50 
51   Comdat *ObjComdat = nullptr;
52   enum {
53     LastAlignmentBit = 5,
54     LastCodeModelBit = 8,
55     HasSectionHashEntryBit,
56 
57     GlobalObjectBits,
58   };
59   static const unsigned GlobalObjectSubClassDataBits =
60       GlobalValueSubClassDataBits - GlobalObjectBits;
61 
62 private:
63   static const unsigned AlignmentBits = LastAlignmentBit + 1;
64   static const unsigned AlignmentMask = (1 << AlignmentBits) - 1;
65   static const unsigned GlobalObjectMask = (1 << GlobalObjectBits) - 1;
66 
67 public:
68   GlobalObject(const GlobalObject &) = delete;
69 
70   /// FIXME: Remove this function once transition to Align is over.
getAlignment()71   uint64_t getAlignment() const {
72     MaybeAlign Align = getAlign();
73     return Align ? Align->value() : 0;
74   }
75 
76   /// Returns the alignment of the given variable or function.
77   ///
78   /// Note that for functions this is the alignment of the code, not the
79   /// alignment of a function pointer.
getAlign()80   MaybeAlign getAlign() const {
81     unsigned Data = getGlobalValueSubClassData();
82     unsigned AlignmentData = Data & AlignmentMask;
83     return decodeMaybeAlign(AlignmentData);
84   }
85 
86   /// Sets the alignment attribute of the GlobalObject.
87   void setAlignment(Align Align);
88 
89   /// Sets the alignment attribute of the GlobalObject.
90   /// This method will be deprecated as the alignment property should always be
91   /// defined.
92   void setAlignment(MaybeAlign Align);
93 
getGlobalObjectSubClassData()94   unsigned getGlobalObjectSubClassData() const {
95     unsigned ValueData = getGlobalValueSubClassData();
96     return ValueData >> GlobalObjectBits;
97   }
98 
setGlobalObjectSubClassData(unsigned Val)99   void setGlobalObjectSubClassData(unsigned Val) {
100     unsigned OldData = getGlobalValueSubClassData();
101     setGlobalValueSubClassData((OldData & GlobalObjectMask) |
102                                (Val << GlobalObjectBits));
103     assert(getGlobalObjectSubClassData() == Val && "representation error");
104   }
105 
106   /// Check if this global has a custom object file section.
107   ///
108   /// This is more efficient than calling getSection() and checking for an empty
109   /// string.
hasSection()110   bool hasSection() const {
111     return getGlobalValueSubClassData() & (1 << HasSectionHashEntryBit);
112   }
113 
114   /// Get the custom section of this global if it has one.
115   ///
116   /// If this global does not have a custom section, this will be empty and the
117   /// default object file section (.text, .data, etc) will be used.
getSection()118   StringRef getSection() const {
119     return hasSection() ? getSectionImpl() : StringRef();
120   }
121 
122   /// Change the section for this global.
123   ///
124   /// Setting the section to the empty string tells LLVM to choose an
125   /// appropriate default object file section.
126   void setSection(StringRef S);
127 
hasComdat()128   bool hasComdat() const { return getComdat() != nullptr; }
getComdat()129   const Comdat *getComdat() const { return ObjComdat; }
getComdat()130   Comdat *getComdat() { return ObjComdat; }
131   void setComdat(Comdat *C);
132 
133   using Value::addMetadata;
134   using Value::clearMetadata;
135   using Value::eraseMetadata;
136   using Value::eraseMetadataIf;
137   using Value::getAllMetadata;
138   using Value::getMetadata;
139   using Value::hasMetadata;
140   using Value::setMetadata;
141 
142   /// Copy metadata from Src, adjusting offsets by Offset.
143   void copyMetadata(const GlobalObject *Src, unsigned Offset);
144 
145   void addTypeMetadata(unsigned Offset, Metadata *TypeID);
146   void setVCallVisibilityMetadata(VCallVisibility Visibility);
147   VCallVisibility getVCallVisibility() const;
148 
149   /// Returns true if the alignment of the value can be unilaterally
150   /// increased.
151   ///
152   /// Note that for functions this is the alignment of the code, not the
153   /// alignment of a function pointer.
154   bool canIncreaseAlignment() const;
155 
156 protected:
157   void copyAttributesFrom(const GlobalObject *Src);
158 
159 public:
160   // Methods for support type inquiry through isa, cast, and dyn_cast:
classof(const Value * V)161   static bool classof(const Value *V) {
162     return V->getValueID() == Value::FunctionVal ||
163            V->getValueID() == Value::GlobalVariableVal ||
164            V->getValueID() == Value::GlobalIFuncVal;
165   }
166 
167 private:
setGlobalObjectFlag(unsigned Bit,bool Val)168   void setGlobalObjectFlag(unsigned Bit, bool Val) {
169     unsigned Mask = 1 << Bit;
170     setGlobalValueSubClassData((~Mask & getGlobalValueSubClassData()) |
171                                (Val ? Mask : 0u));
172   }
173 
174   StringRef getSectionImpl() const;
175 };
176 
177 } // end namespace llvm
178 
179 #endif // LLVM_IR_GLOBALOBJECT_H
180