LLVM  mainline
StripDeadPrototypes.cpp
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00001 //===-- StripDeadPrototypes.cpp - Remove unused function declarations ----===//
00002 //
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file is distributed under the University of Illinois Open Source
00006 // License. See LICENSE.TXT for details.
00007 //
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This pass loops over all of the functions in the input module, looking for 
00011 // dead declarations and removes them. Dead declarations are declarations of
00012 // functions for which no implementation is available (i.e., declarations for
00013 // unused library functions).
00014 //
00015 //===----------------------------------------------------------------------===//
00016 
00017 #include "llvm/Transforms/IPO.h"
00018 #include "llvm/ADT/Statistic.h"
00019 #include "llvm/IR/Module.h"
00020 #include "llvm/Pass.h"
00021 using namespace llvm;
00022 
00023 #define DEBUG_TYPE "strip-dead-prototypes"
00024 
00025 STATISTIC(NumDeadPrototypes, "Number of dead prototypes removed");
00026 
00027 namespace {
00028 
00029 /// @brief Pass to remove unused function declarations.
00030 class StripDeadPrototypesPass : public ModulePass {
00031 public:
00032   static char ID; // Pass identification, replacement for typeid
00033   StripDeadPrototypesPass() : ModulePass(ID) {
00034     initializeStripDeadPrototypesPassPass(*PassRegistry::getPassRegistry());
00035   }
00036   bool runOnModule(Module &M) override;
00037 };
00038 
00039 } // end anonymous namespace
00040 
00041 char StripDeadPrototypesPass::ID = 0;
00042 INITIALIZE_PASS(StripDeadPrototypesPass, "strip-dead-prototypes",
00043                 "Strip Unused Function Prototypes", false, false)
00044 
00045 bool StripDeadPrototypesPass::runOnModule(Module &M) {
00046   bool MadeChange = false;
00047   
00048   // Erase dead function prototypes.
00049   for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
00050     Function *F = I++;
00051     // Function must be a prototype and unused.
00052     if (F->isDeclaration() && F->use_empty()) {
00053       F->eraseFromParent();
00054       ++NumDeadPrototypes;
00055       MadeChange = true;
00056     }
00057   }
00058 
00059   // Erase dead global var prototypes.
00060   for (Module::global_iterator I = M.global_begin(), E = M.global_end();
00061        I != E; ) {
00062     GlobalVariable *GV = I++;
00063     // Global must be a prototype and unused.
00064     if (GV->isDeclaration() && GV->use_empty())
00065       GV->eraseFromParent();
00066   }
00067   
00068   // Return an indication of whether we changed anything or not.
00069   return MadeChange;
00070 }
00071 
00072 ModulePass *llvm::createStripDeadPrototypesPass() {
00073   return new StripDeadPrototypesPass();
00074 }