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 29 namespace llvm { 30 class Comdat; 31 class GlobalValue; 32 class Module; 33 34 /// A pass that internalizes all functions and variables other than those that 35 /// must be preserved according to \c MustPreserveGV. 36 class InternalizePass : public PassInfoMixin<InternalizePass> { 37 struct ComdatInfo { 38 // The number of members. A comdat with one member which is not externally 39 // visible can be freely dropped. 40 size_t Size = 0; 41 // Whether the comdat has an externally visible member. 42 bool External = false; 43 }; 44 45 bool IsWasm = false; 46 47 /// Client supplied callback to control wheter a symbol must be preserved. 48 const std::function<bool(const GlobalValue &)> MustPreserveGV; 49 /// Set of symbols private to the compiler that this pass should not touch. 50 StringSet<> AlwaysPreserved; 51 52 /// Return false if we're allowed to internalize this GV. 53 bool shouldPreserveGV(const GlobalValue &GV); 54 /// Internalize GV if it is possible to do so, i.e. it is not externally 55 /// visible and is not a member of an externally visible comdat. 56 bool maybeInternalize(GlobalValue &GV, 57 DenseMap<const Comdat *, ComdatInfo> &ComdatMap); 58 /// If GV is part of a comdat and is externally visible, keep track of its 59 /// comdat so that we don't internalize any of its members. 60 void checkComdat(GlobalValue &GV, 61 DenseMap<const Comdat *, ComdatInfo> &ComdatMap); 62 63 public: 64 InternalizePass(); 65 InternalizePass(std::function<bool(const GlobalValue &)> MustPreserveGV) 66 : MustPreserveGV(std::move(MustPreserveGV)) {} 67 68 /// Run the internalizer on \p TheModule, returns true if any changes was 69 /// made. 70 bool internalizeModule(Module &TheModule); 71 72 PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM); 73 }; 74 75 /// Helper function to internalize functions and variables in a Module. 76 inline bool 77 internalizeModule(Module &TheModule, 78 std::function<bool(const GlobalValue &)> MustPreserveGV) { 79 return InternalizePass(std::move(MustPreserveGV)) 80 .internalizeModule(TheModule); 81 } 82 } // end namespace llvm 83 84 #endif // LLVM_TRANSFORMS_IPO_INTERNALIZE_H 85