ModuleUtils.cpp revision 263508 
1//===-- ModuleUtils.cpp - Functions to manipulate Modules -----------------===//
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 family of functions perform manipulations on Modules.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Transforms/Utils/ModuleUtils.h"
15#include "llvm/ADT/SmallPtrSet.h"
16#include "llvm/IR/DerivedTypes.h"
17#include "llvm/IR/Function.h"
18#include "llvm/IR/IRBuilder.h"
19#include "llvm/IR/Module.h"
20
21using namespace llvm;
22
23static void appendToGlobalArray(const char *Array,
24                                Module &M, Function *F, int Priority) {
25  IRBuilder<> IRB(M.getContext());
26  FunctionType *FnTy = FunctionType::get(IRB.getVoidTy(), false);
27  StructType *Ty = StructType::get(
28      IRB.getInt32Ty(), PointerType::getUnqual(FnTy), NULL);
29
30  Constant *RuntimeCtorInit = ConstantStruct::get(
31      Ty, IRB.getInt32(Priority), F, NULL);
32
33  // Get the current set of static global constructors and add the new ctor
34  // to the list.
35  SmallVector<Constant *, 16> CurrentCtors;
36  if (GlobalVariable * GVCtor = M.getNamedGlobal(Array)) {
37    if (Constant *Init = GVCtor->getInitializer()) {
38      unsigned n = Init->getNumOperands();
39      CurrentCtors.reserve(n + 1);
40      for (unsigned i = 0; i != n; ++i)
41        CurrentCtors.push_back(cast<Constant>(Init->getOperand(i)));
42    }
43    GVCtor->eraseFromParent();
44  }
45
46  CurrentCtors.push_back(RuntimeCtorInit);
47
48  // Create a new initializer.
49  ArrayType *AT = ArrayType::get(RuntimeCtorInit->getType(),
50                                 CurrentCtors.size());
51  Constant *NewInit = ConstantArray::get(AT, CurrentCtors);
52
53  // Create the new global variable and replace all uses of
54  // the old global variable with the new one.
55  (void)new GlobalVariable(M, NewInit->getType(), false,
56                           GlobalValue::AppendingLinkage, NewInit, Array);
57}
58
59void llvm::appendToGlobalCtors(Module &M, Function *F, int Priority) {
60  appendToGlobalArray("llvm.global_ctors", M, F, Priority);
61}
62
63void llvm::appendToGlobalDtors(Module &M, Function *F, int Priority) {
64  appendToGlobalArray("llvm.global_dtors", M, F, Priority);
65}
66
67GlobalVariable *
68llvm::collectUsedGlobalVariables(Module &M, SmallPtrSet<GlobalValue *, 8> &Set,
69                                 bool CompilerUsed) {
70  const char *Name = CompilerUsed ? "llvm.compiler.used" : "llvm.used";
71  GlobalVariable *GV = M.getGlobalVariable(Name);
72  if (!GV || !GV->hasInitializer())
73    return GV;
74
75  const ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
76  for (unsigned I = 0, E = Init->getNumOperands(); I != E; ++I) {
77    Value *Op = Init->getOperand(I);
78    GlobalValue *G = cast<GlobalValue>(Op->stripPointerCastsNoFollowAliases());
79    Set.insert(G);
80  }
81  return GV;
82}
83