1 //===-- StripDeadPrototypes.cpp - Remove unused function declarations ----===// 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 in the input module, looking for 10 // dead declarations and removes them. Dead declarations are declarations of 11 // functions for which no implementation is available (i.e., declarations for 12 // unused library functions). 13 // 14 //===----------------------------------------------------------------------===// 15 16 #include "llvm/Transforms/IPO/StripDeadPrototypes.h" 17 #include "llvm/ADT/Statistic.h" 18 #include "llvm/IR/Module.h" 19 #include "llvm/Transforms/IPO.h" 20 21 using namespace llvm; 22 23 #define DEBUG_TYPE "strip-dead-prototypes" 24 25 STATISTIC(NumDeadPrototypes, "Number of dead prototypes removed"); 26 27 static bool stripDeadPrototypes(Module &M) { 28 bool MadeChange = false; 29 30 // Erase dead function prototypes. 31 for (Function &F : llvm::make_early_inc_range(M)) { 32 // Function must be a prototype and unused. 33 if (F.isDeclaration() && F.use_empty()) { 34 F.eraseFromParent(); 35 ++NumDeadPrototypes; 36 MadeChange = true; 37 } 38 } 39 40 // Erase dead global var prototypes. 41 for (GlobalVariable &GV : llvm::make_early_inc_range(M.globals())) { 42 // Global must be a prototype and unused. 43 if (GV.isDeclaration() && GV.use_empty()) 44 GV.eraseFromParent(); 45 } 46 47 // Return an indication of whether we changed anything or not. 48 return MadeChange; 49 } 50 51 PreservedAnalyses StripDeadPrototypesPass::run(Module &M, 52 ModuleAnalysisManager &) { 53 if (stripDeadPrototypes(M)) 54 return PreservedAnalyses::none(); 55 return PreservedAnalyses::all(); 56 } 57