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 20 using namespace llvm; 21 22 #define DEBUG_TYPE "strip-dead-prototypes" 23 24 STATISTIC(NumDeadPrototypes, "Number of dead prototypes removed"); 25 26 static bool stripDeadPrototypes(Module &M) { 27 bool MadeChange = false; 28 29 // Erase dead function prototypes. 30 for (Function &F : llvm::make_early_inc_range(M)) { 31 // Function must be a prototype and unused. 32 if (F.isDeclaration() && F.use_empty()) { 33 F.eraseFromParent(); 34 ++NumDeadPrototypes; 35 MadeChange = true; 36 } 37 } 38 39 // Erase dead global var prototypes. 40 for (GlobalVariable &GV : llvm::make_early_inc_range(M.globals())) { 41 // Global must be a prototype and unused. 42 if (GV.isDeclaration() && GV.use_empty()) 43 GV.eraseFromParent(); 44 } 45 46 // Return an indication of whether we changed anything or not. 47 return MadeChange; 48 } 49 50 PreservedAnalyses StripDeadPrototypesPass::run(Module &M, 51 ModuleAnalysisManager &) { 52 if (stripDeadPrototypes(M)) 53 return PreservedAnalyses::none(); 54 return PreservedAnalyses::all(); 55 } 56