1 //===---------------------- TableManager.h ----------------------*- 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 // Fix edge for edge that needs an entry to reference the target symbol
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_EXECUTIONENGINE_JITLINK_TABLEMANAGER_H
14 #define LLVM_EXECUTIONENGINE_JITLINK_TABLEMANAGER_H
15 
16 #include "llvm/ExecutionEngine/JITLink/JITLink.h"
17 #include "llvm/Support/Debug.h"
18 
19 namespace llvm {
20 namespace jitlink {
21 
22 /// A CRTP base for tables that are built on demand, e.g. Global Offset Tables
23 /// and Procedure Linkage Tables.
24 /// The getEntyrForTarget function returns the table entry corresponding to the
25 /// given target, calling down to the implementation class to build an entry if
26 /// one does not already exist.
27 template <typename TableManagerImplT> class TableManager {
28 public:
29   /// Return the constructed entry
30   ///
31   /// Use parameter G to construct the entry for target symbol
32   Symbol &getEntryForTarget(LinkGraph &G, Symbol &Target) {
33     assert(Target.hasName() && "Edge cannot point to anonymous target");
34 
35     auto EntryI = Entries.find(Target.getName());
36 
37     // Build the entry if it doesn't exist.
38     if (EntryI == Entries.end()) {
39       auto &Entry = impl().createEntry(G, Target);
40       DEBUG_WITH_TYPE("jitlink", {
41         dbgs() << "    Created " << impl().getSectionName() << " entry for "
42                << Target.getName() << ": " << Entry << "\n";
43       });
44       EntryI = Entries.insert(std::make_pair(Target.getName(), &Entry)).first;
45     }
46 
47     assert(EntryI != Entries.end() && "Could not get entry symbol");
48     DEBUG_WITH_TYPE("jitlink", {
49       dbgs() << "    Using " << impl().getSectionName() << " entry "
50              << *EntryI->second << "\n";
51     });
52     return *EntryI->second;
53   }
54 
55   /// Register a pre-existing entry.
56   ///
57   /// Objects may include pre-existing table entries (e.g. for GOTs).
58   /// This method can be used to register those entries so that they will not
59   /// be duplicated by createEntry  the first time that getEntryForTarget is
60   /// called.
61   bool registerPreExistingEntry(Symbol &Target, Symbol &Entry) {
62     assert(Target.hasName() && "Edge cannot point to anonymous target");
63     auto Res = Entries.insert({
64         Target.getName(),
65         &Entry,
66     });
67     return Res.second;
68   }
69 
70 private:
71   TableManagerImplT &impl() { return static_cast<TableManagerImplT &>(*this); }
72   DenseMap<StringRef, Symbol *> Entries;
73 };
74 
75 } // namespace jitlink
76 } // namespace llvm
77 
78 #endif
79