StripDeadPrototypes.cpp revision ae73dc1448d25b02cabc7c64c86c64371453dda8 
1//===-- StripDeadPrototypes.cpp - Remove unused function declarations ----===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This pass loops over all of the functions in the input module, looking for
11// dead declarations and removes them. Dead declarations are declarations of
12// functions for which no implementation is available (i.e., declarations for
13// unused library functions).
14//
15//===----------------------------------------------------------------------===//
16
17#define DEBUG_TYPE "strip-dead-prototypes"
18#include "llvm/Transforms/IPO.h"
19#include "llvm/Pass.h"
20#include "llvm/Module.h"
21#include "llvm/ADT/Statistic.h"
22#include "llvm/Support/Compiler.h"
23using namespace llvm;
24
25STATISTIC(NumDeadPrototypes, "Number of dead prototypes removed");
26
27namespace {
28
29/// @brief Pass to remove unused function declarations.
30class VISIBILITY_HIDDEN StripDeadPrototypesPass : public ModulePass {
31public:
32  static char ID; // Pass identification, replacement for typeid
33  StripDeadPrototypesPass() : ModulePass(&ID) { }
34  virtual bool runOnModule(Module &M);
35};
36
37} // end anonymous namespace
38
39char StripDeadPrototypesPass::ID = 0;
40static RegisterPass<StripDeadPrototypesPass>
41X("strip-dead-prototypes", "Strip Unused Function Prototypes");
42
43bool StripDeadPrototypesPass::runOnModule(Module &M) {
44  bool MadeChange = false;
45
46  // Erase dead function prototypes.
47  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
48    Function *F = I++;
49    // Function must be a prototype and unused.
50    if (F->isDeclaration() && F->use_empty()) {
51      F->eraseFromParent();
52      ++NumDeadPrototypes;
53      MadeChange = true;
54    }
55  }
56
57  // Erase dead global var prototypes.
58  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
59       I != E; ) {
60    GlobalVariable *GV = I++;
61    // Global must be a prototype and unused.
62    if (GV->isDeclaration() && GV->use_empty())
63      GV->eraseFromParent();
64  }
65
66  // Return an indication of whether we changed anything or not.
67  return MadeChange;
68}
69
70ModulePass *llvm::createStripDeadPrototypesPass() {
71  return new StripDeadPrototypesPass();
72}
73