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
21 using namespace llvm;
22
appendToGlobalArray(const char * Array,Module & M,Function * F,int Priority)23 static 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
28 // Get the current set of static global constructors and add the new ctor
29 // to the list.
30 SmallVector<Constant *, 16> CurrentCtors;
31 StructType *EltTy;
32 if (GlobalVariable *GVCtor = M.getNamedGlobal(Array)) {
33 // If there is a global_ctors array, use the existing struct type, which can
34 // have 2 or 3 fields.
35 ArrayType *ATy = cast<ArrayType>(GVCtor->getType()->getElementType());
36 EltTy = cast<StructType>(ATy->getElementType());
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 } else {
45 // Use a simple two-field struct if there isn't one already.
46 EltTy = StructType::get(IRB.getInt32Ty(), PointerType::getUnqual(FnTy),
47 nullptr);
48 }
49
50 // Build a 2 or 3 field global_ctor entry. We don't take a comdat key.
51 Constant *CSVals[3];
52 CSVals[0] = IRB.getInt32(Priority);
53 CSVals[1] = F;
54 // FIXME: Drop support for the two element form in LLVM 4.0.
55 if (EltTy->getNumElements() >= 3)
56 CSVals[2] = llvm::Constant::getNullValue(IRB.getInt8PtrTy());
57 Constant *RuntimeCtorInit =
58 ConstantStruct::get(EltTy, makeArrayRef(CSVals, EltTy->getNumElements()));
59
60 CurrentCtors.push_back(RuntimeCtorInit);
61
62 // Create a new initializer.
63 ArrayType *AT = ArrayType::get(EltTy, CurrentCtors.size());
64 Constant *NewInit = ConstantArray::get(AT, CurrentCtors);
65
66 // Create the new global variable and replace all uses of
67 // the old global variable with the new one.
68 (void)new GlobalVariable(M, NewInit->getType(), false,
69 GlobalValue::AppendingLinkage, NewInit, Array);
70 }
71
appendToGlobalCtors(Module & M,Function * F,int Priority)72 void llvm::appendToGlobalCtors(Module &M, Function *F, int Priority) {
73 appendToGlobalArray("llvm.global_ctors", M, F, Priority);
74 }
75
appendToGlobalDtors(Module & M,Function * F,int Priority)76 void llvm::appendToGlobalDtors(Module &M, Function *F, int Priority) {
77 appendToGlobalArray("llvm.global_dtors", M, F, Priority);
78 }
79
80 GlobalVariable *
collectUsedGlobalVariables(Module & M,SmallPtrSetImpl<GlobalValue * > & Set,bool CompilerUsed)81 llvm::collectUsedGlobalVariables(Module &M, SmallPtrSetImpl<GlobalValue *> &Set,
82 bool CompilerUsed) {
83 const char *Name = CompilerUsed ? "llvm.compiler.used" : "llvm.used";
84 GlobalVariable *GV = M.getGlobalVariable(Name);
85 if (!GV || !GV->hasInitializer())
86 return GV;
87
88 const ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
89 for (unsigned I = 0, E = Init->getNumOperands(); I != E; ++I) {
90 Value *Op = Init->getOperand(I);
91 GlobalValue *G = cast<GlobalValue>(Op->stripPointerCastsNoFollowAliases());
92 Set.insert(G);
93 }
94 return GV;
95 }
96