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/DenseSet.h"
25#include "llvm/ADT/StringSet.h"
26#include "llvm/IR/GlobalValue.h"
27#include "llvm/IR/PassManager.h"
28#include <functional>
29
30namespace llvm {
31class Module;
32class CallGraph;
33
34/// A pass that internalizes all functions and variables other than those that
35/// must be preserved according to \c MustPreserveGV.
36class InternalizePass : public PassInfoMixin<InternalizePass> {
37 /// Client supplied callback to control wheter a symbol must be preserved.
38 const std::function<bool(const GlobalValue &)> MustPreserveGV;
39 /// Set of symbols private to the compiler that this pass should not touch.
40 StringSet<> AlwaysPreserved;
41
42 /// Return false if we're allowed to internalize this GV.
43 bool shouldPreserveGV(const GlobalValue &GV);
44 /// Internalize GV if it is possible to do so, i.e. it is not externally
45 /// visible and is not a member of an externally visible comdat.
46 bool maybeInternalize(GlobalValue &GV,
47 const DenseSet<const Comdat *> &ExternalComdats);
48 /// If GV is part of a comdat and is externally visible, keep track of its
49 /// comdat so that we don't internalize any of its members.
50 void checkComdatVisibility(GlobalValue &GV,
51 DenseSet<const Comdat *> &ExternalComdats);
52
53public:
54 InternalizePass();
55 InternalizePass(std::function<bool(const GlobalValue &)> MustPreserveGV)
56 : MustPreserveGV(std::move(MustPreserveGV)) {}
57
58 /// Run the internalizer on \p TheModule, returns true if any changes was
59 /// made.
60 ///
61 /// If the CallGraph \p CG is supplied, it will be updated when
62 /// internalizing a function (by removing any edge from the "external node")
63 bool internalizeModule(Module &TheModule, CallGraph *CG = nullptr);
64
65 PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
66};
67
68/// Helper function to internalize functions and variables in a Module.
69inline bool
70internalizeModule(Module &TheModule,
71 std::function<bool(const GlobalValue &)> MustPreserveGV,
72 CallGraph *CG = nullptr) {
73 return InternalizePass(std::move(MustPreserveGV))
74 .internalizeModule(TheModule, CG);
75}
76} // end namespace llvm
77
78#endif // LLVM_TRANSFORMS_IPO_INTERNALIZE_H
79