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/InitializePasses.h"
20 #include "llvm/Pass.h"
21 #include "llvm/Transforms/IPO.h"
22
23 using namespace llvm;
24
25 #define DEBUG_TYPE "strip-dead-prototypes"
26
27 STATISTIC(NumDeadPrototypes, "Number of dead prototypes removed");
28
stripDeadPrototypes(Module & M)29 static bool stripDeadPrototypes(Module &M) {
30 bool MadeChange = false;
31
32 // Erase dead function prototypes.
33 for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
34 Function *F = &*I++;
35 // Function must be a prototype and unused.
36 if (F->isDeclaration() && F->use_empty()) {
37 F->eraseFromParent();
38 ++NumDeadPrototypes;
39 MadeChange = true;
40 }
41 }
42
43 // Erase dead global var prototypes.
44 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
45 I != E; ) {
46 GlobalVariable *GV = &*I++;
47 // Global must be a prototype and unused.
48 if (GV->isDeclaration() && GV->use_empty())
49 GV->eraseFromParent();
50 }
51
52 // Return an indication of whether we changed anything or not.
53 return MadeChange;
54 }
55
run(Module & M,ModuleAnalysisManager &)56 PreservedAnalyses StripDeadPrototypesPass::run(Module &M,
57 ModuleAnalysisManager &) {
58 if (stripDeadPrototypes(M))
59 return PreservedAnalyses::none();
60 return PreservedAnalyses::all();
61 }
62
63 namespace {
64
65 class StripDeadPrototypesLegacyPass : public ModulePass {
66 public:
67 static char ID; // Pass identification, replacement for typeid
StripDeadPrototypesLegacyPass()68 StripDeadPrototypesLegacyPass() : ModulePass(ID) {
69 initializeStripDeadPrototypesLegacyPassPass(
70 *PassRegistry::getPassRegistry());
71 }
runOnModule(Module & M)72 bool runOnModule(Module &M) override {
73 if (skipModule(M))
74 return false;
75
76 return stripDeadPrototypes(M);
77 }
78 };
79
80 } // end anonymous namespace
81
82 char StripDeadPrototypesLegacyPass::ID = 0;
83 INITIALIZE_PASS(StripDeadPrototypesLegacyPass, "strip-dead-prototypes",
84 "Strip Unused Function Prototypes", false, false)
85
createStripDeadPrototypesPass()86 ModulePass *llvm::createStripDeadPrototypesPass() {
87 return new StripDeadPrototypesLegacyPass();
88 }
89