LLVM  14.0.0git
JITLinkGeneric.h
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1 //===------ JITLinkGeneric.h - Generic JIT linker utilities -----*- 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 // Generic JITLinker utilities. E.g. graph pruning, eh-frame parsing.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LIB_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H
14 #define LIB_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H
15 
16 #include "llvm/ADT/DenseSet.h"
18 
19 #define DEBUG_TYPE "jitlink"
20 
21 namespace llvm {
22 
23 class MemoryBufferRef;
24 
25 namespace jitlink {
26 
27 /// Base class for a JIT linker.
28 ///
29 /// A JITLinkerBase instance links one object file into an ongoing JIT
30 /// session. Symbol resolution and finalization operations are pluggable,
31 /// and called using continuation passing (passing a continuation for the
32 /// remaining linker work) to allow them to be performed asynchronously.
34 public:
35  JITLinkerBase(std::unique_ptr<JITLinkContext> Ctx,
36  std::unique_ptr<LinkGraph> G, PassConfiguration Passes)
37  : Ctx(std::move(Ctx)), G(std::move(G)), Passes(std::move(Passes)) {
38  assert(this->Ctx && "Ctx can not be null");
39  assert(this->G && "G can not be null");
40  }
41 
42  virtual ~JITLinkerBase();
43 
44 protected:
48 
49  // Returns the PassConfiguration for this instance. This can be used by
50  // JITLinkerBase implementations to add late passes that reference their
51  // own data structures (e.g. for ELF implementations to locate / construct
52  // a GOT start symbol prior to fixup).
53  PassConfiguration &getPassConfig() { return Passes; }
54 
55  // Phase 1:
56  // 1.1: Run pre-prune passes
57  // 1.2: Prune graph
58  // 1.3: Run post-prune passes
59  // 1.4: Allocate memory.
60  void linkPhase1(std::unique_ptr<JITLinkerBase> Self);
61 
62  // Phase 2:
63  // 2.2: Run post-allocation passes
64  // 2.3: Notify context of final assigned symbol addresses
65  // 2.4: Identify external symbols and make an async call to resolve
66  void linkPhase2(std::unique_ptr<JITLinkerBase> Self, AllocResult AR);
67 
68  // Phase 3:
69  // 3.1: Apply resolution results
70  // 3.2: Run pre-fixup passes
71  // 3.3: Fix up block contents
72  // 3.4: Run post-fixup passes
73  // 3.5: Make an async call to transfer and finalize memory.
74  void linkPhase3(std::unique_ptr<JITLinkerBase> Self,
76 
77  // Phase 4:
78  // 4.1: Call OnFinalized callback, handing off allocation.
79  void linkPhase4(std::unique_ptr<JITLinkerBase> Self, FinalizeResult FR);
80 
81 private:
82  // Run all passes in the given pass list, bailing out immediately if any pass
83  // returns an error.
84  Error runPasses(LinkGraphPassList &Passes);
85 
86  // Copy block contents and apply relocations.
87  // Implemented in JITLinker.
88  virtual Error fixUpBlocks(LinkGraph &G) const = 0;
89 
90  JITLinkContext::LookupMap getExternalSymbolNames() const;
91  void applyLookupResult(AsyncLookupResult LR);
92  void abandonAllocAndBailOut(std::unique_ptr<JITLinkerBase> Self, Error Err);
93 
94  std::unique_ptr<JITLinkContext> Ctx;
95  std::unique_ptr<LinkGraph> G;
96  PassConfiguration Passes;
97  std::unique_ptr<InFlightAlloc> Alloc;
98 };
99 
100 template <typename LinkerImpl> class JITLinker : public JITLinkerBase {
101 public:
103 
104  /// Link constructs a LinkerImpl instance and calls linkPhase1.
105  /// Link should be called with the constructor arguments for LinkerImpl, which
106  /// will be forwarded to the constructor.
107  template <typename... ArgTs> static void link(ArgTs &&... Args) {
108  auto L = std::make_unique<LinkerImpl>(std::forward<ArgTs>(Args)...);
109 
110  // Ownership of the linker is passed into the linker's doLink function to
111  // allow it to be passed on to async continuations.
112  //
113  // FIXME: Remove LTmp once we have c++17.
114  // C++17 sequencing rules guarantee that function name expressions are
115  // sequenced before arguments, so L->linkPhase1(std::move(L), ...) will be
116  // well formed.
117  auto &LTmp = *L;
118  LTmp.linkPhase1(std::move(L));
119  }
120 
121 private:
122  const LinkerImpl &impl() const {
123  return static_cast<const LinkerImpl &>(*this);
124  }
125 
126  Error fixUpBlocks(LinkGraph &G) const override {
127  LLVM_DEBUG(dbgs() << "Fixing up blocks:\n");
128 
129  for (auto *B : G.blocks()) {
130  LLVM_DEBUG(dbgs() << " " << *B << ":\n");
131 
132  // Copy Block data and apply fixups.
133  LLVM_DEBUG(dbgs() << " Applying fixups.\n");
134  assert((!B->isZeroFill() || B->edges_size() == 0) &&
135  "Edges in zero-fill block?");
136  for (auto &E : B->edges()) {
137 
138  // Skip non-relocation edges.
139  if (!E.isRelocation())
140  continue;
141 
142  // Dispatch to LinkerImpl for fixup.
143  if (auto Err = impl().applyFixup(G, *B, E))
144  return Err;
145  }
146  }
147 
148  return Error::success();
149  }
150 };
151 
152 /// Removes dead symbols/blocks/addressables.
153 ///
154 /// Finds the set of symbols and addressables reachable from any symbol
155 /// initially marked live. All symbols/addressables not marked live at the end
156 /// of this process are removed.
157 void prune(LinkGraph &G);
158 
159 } // end namespace jitlink
160 } // end namespace llvm
161 
162 #undef DEBUG_TYPE // "jitlink"
163 
164 #endif // LLVM_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H
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