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 #include "llvm/Transforms/IPO.h"
18 #include "llvm/ADT/Statistic.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/Pass.h"
21 using namespace llvm;
22
23 #define DEBUG_TYPE "strip-dead-prototypes"
24
25 STATISTIC(NumDeadPrototypes, "Number of dead prototypes removed");
26
27 namespace {
28
29 /// @brief Pass to remove unused function declarations.
30 class StripDeadPrototypesPass : public ModulePass {
31 public:
32 static char ID; // Pass identification, replacement for typeid
StripDeadPrototypesPass()33 StripDeadPrototypesPass() : ModulePass(ID) {
34 initializeStripDeadPrototypesPassPass(*PassRegistry::getPassRegistry());
35 }
36 bool runOnModule(Module &M) override;
37 };
38
39 } // end anonymous namespace
40
41 char StripDeadPrototypesPass::ID = 0;
42 INITIALIZE_PASS(StripDeadPrototypesPass, "strip-dead-prototypes",
43 "Strip Unused Function Prototypes", false, false)
44
runOnModule(Module & M)45 bool StripDeadPrototypesPass::runOnModule(Module &M) {
46 bool MadeChange = false;
47
48 // Erase dead function prototypes.
49 for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
50 Function *F = I++;
51 // Function must be a prototype and unused.
52 if (F->isDeclaration() && F->use_empty()) {
53 F->eraseFromParent();
54 ++NumDeadPrototypes;
55 MadeChange = true;
56 }
57 }
58
59 // Erase dead global var prototypes.
60 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
61 I != E; ) {
62 GlobalVariable *GV = I++;
63 // Global must be a prototype and unused.
64 if (GV->isDeclaration() && GV->use_empty())
65 GV->eraseFromParent();
66 }
67
68 // Return an indication of whether we changed anything or not.
69 return MadeChange;
70 }
71
createStripDeadPrototypesPass()72 ModulePass *llvm::createStripDeadPrototypesPass() {
73 return new StripDeadPrototypesPass();
74 }
75