1//====- Internalize.h - Internalization API ---------------------*- 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 pass loops over all of the functions and variables in the input module.
10// If the function or variable does not need to be preserved according to the
11// client supplied callback, it is marked as internal.
12//
13// This transformation would not be legal in a regular compilation, but it gets
14// extra information from the linker about what is safe.
15//
16// For example: Internalizing a function with external linkage. Only if we are
17// told it is only used from within this module, it is safe to do it.
18//
19//===----------------------------------------------------------------------===//
20
21#ifndef LLVM_TRANSFORMS_IPO_INTERNALIZE_H
22#define LLVM_TRANSFORMS_IPO_INTERNALIZE_H
23
24#include "llvm/ADT/DenseMap.h"
25#include "llvm/ADT/StringSet.h"
26#include "llvm/IR/PassManager.h"
27#include <functional>
28
29namespace llvm {
30class Module;
31
32/// A pass that internalizes all functions and variables other than those that
33/// must be preserved according to \c MustPreserveGV.
34class InternalizePass : public PassInfoMixin<InternalizePass> {
35  struct ComdatInfo {
36    // The number of members. A comdat with one member which is not externally
37    // visible can be freely dropped.
38    size_t Size = 0;
39    // Whether the comdat has an externally visible member.
40    bool External = false;
41  };
42
43  bool IsWasm = false;
44
45  /// Client supplied callback to control wheter a symbol must be preserved.
46  const std::function<bool(const GlobalValue &)> MustPreserveGV;
47  /// Set of symbols private to the compiler that this pass should not touch.
48  StringSet<> AlwaysPreserved;
49
50  /// Return false if we're allowed to internalize this GV.
51  bool shouldPreserveGV(const GlobalValue &GV);
52  /// Internalize GV if it is possible to do so, i.e. it is not externally
53  /// visible and is not a member of an externally visible comdat.
54  bool maybeInternalize(GlobalValue &GV,
55                        DenseMap<const Comdat *, ComdatInfo> &ComdatMap);
56  /// If GV is part of a comdat and is externally visible, keep track of its
57  /// comdat so that we don't internalize any of its members.
58  void checkComdat(GlobalValue &GV,
59                   DenseMap<const Comdat *, ComdatInfo> &ComdatMap);
60
61public:
62  InternalizePass();
63  InternalizePass(std::function<bool(const GlobalValue &)> MustPreserveGV)
64      : MustPreserveGV(std::move(MustPreserveGV)) {}
65
66  /// Run the internalizer on \p TheModule, returns true if any changes was
67  /// made.
68  bool internalizeModule(Module &TheModule);
69
70  PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
71};
72
73/// Helper function to internalize functions and variables in a Module.
74inline bool
75internalizeModule(Module &TheModule,
76                  std::function<bool(const GlobalValue &)> MustPreserveGV) {
77  return InternalizePass(std::move(MustPreserveGV))
78      .internalizeModule(TheModule);
79}
80} // end namespace llvm
81
82#endif // LLVM_TRANSFORMS_IPO_INTERNALIZE_H
83