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
20using namespace llvm;
21
22#define DEBUG_TYPE "strip-dead-prototypes"
23
24STATISTIC(NumDeadPrototypes, "Number of dead prototypes removed");
25
26static bool stripDeadPrototypes(Module &M) {
27 bool MadeChange = false;
28
29 // Erase dead function prototypes.
30 for (Function &F : llvm::make_early_inc_range(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(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
50PreservedAnalyses StripDeadPrototypesPass::run(Module &M,
51 ModuleAnalysisManager &) {
52 if (stripDeadPrototypes(M))
53 return PreservedAnalyses::none();
54 return PreservedAnalyses::all();
55}
56