xref: /freebsd/contrib/llvm-project/llvm/lib/Transforms/Utils/ModuleUtils.cpp (revision 60d0871dbfbebe20a9e24c1b4c659cfe841154c1) 
1  //===-- ModuleUtils.cpp - Functions to manipulate Modules -----------------===//
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 family of functions perform manipulations on Modules.
10  //
11  //===----------------------------------------------------------------------===//
12  
13  #include "llvm/Transforms/Utils/ModuleUtils.h"
14  #include "llvm/Analysis/VectorUtils.h"
15  #include "llvm/IR/DerivedTypes.h"
16  #include "llvm/IR/Function.h"
17  #include "llvm/IR/IRBuilder.h"
18  #include "llvm/IR/Module.h"
19  #include "llvm/Support/raw_ostream.h"
20  using namespace llvm;
21  
22  #define DEBUG_TYPE "moduleutils"
23  
24  static void appendToGlobalArray(const char *Array, Module &M, Function *F,
25                                  int Priority, Constant *Data) {
26    IRBuilder<> IRB(M.getContext());
27    FunctionType *FnTy = FunctionType::get(IRB.getVoidTy(), false);
28  
29    // Get the current set of static global constructors and add the new ctor
30    // to the list.
31    SmallVector<Constant *, 16> CurrentCtors;
32    StructType *EltTy = StructType::get(
33        IRB.getInt32Ty(), PointerType::getUnqual(FnTy), IRB.getInt8PtrTy());
34    if (GlobalVariable *GVCtor = M.getNamedGlobal(Array)) {
35      if (Constant *Init = GVCtor->getInitializer()) {
36        unsigned n = Init->getNumOperands();
37        CurrentCtors.reserve(n + 1);
38        for (unsigned i = 0; i != n; ++i)
39          CurrentCtors.push_back(cast<Constant>(Init->getOperand(i)));
40      }
41      GVCtor->eraseFromParent();
42    }
43  
44    // Build a 3 field global_ctor entry.  We don't take a comdat key.
45    Constant *CSVals[3];
46    CSVals[0] = IRB.getInt32(Priority);
47    CSVals[1] = F;
48    CSVals[2] = Data ? ConstantExpr::getPointerCast(Data, IRB.getInt8PtrTy())
49                     : Constant::getNullValue(IRB.getInt8PtrTy());
50    Constant *RuntimeCtorInit =
51        ConstantStruct::get(EltTy, makeArrayRef(CSVals, EltTy->getNumElements()));
52  
53    CurrentCtors.push_back(RuntimeCtorInit);
54  
55    // Create a new initializer.
56    ArrayType *AT = ArrayType::get(EltTy, CurrentCtors.size());
57    Constant *NewInit = ConstantArray::get(AT, CurrentCtors);
58  
59    // Create the new global variable and replace all uses of
60    // the old global variable with the new one.
61    (void)new GlobalVariable(M, NewInit->getType(), false,
62                             GlobalValue::AppendingLinkage, NewInit, Array);
63  }
64  
65  void llvm::appendToGlobalCtors(Module &M, Function *F, int Priority, Constant *Data) {
66    appendToGlobalArray("llvm.global_ctors", M, F, Priority, Data);
67  }
68  
69  void llvm::appendToGlobalDtors(Module &M, Function *F, int Priority, Constant *Data) {
70    appendToGlobalArray("llvm.global_dtors", M, F, Priority, Data);
71  }
72  
73  static void appendToUsedList(Module &M, StringRef Name, ArrayRef<GlobalValue *> Values) {
74    GlobalVariable *GV = M.getGlobalVariable(Name);
75    SmallPtrSet<Constant *, 16> InitAsSet;
76    SmallVector<Constant *, 16> Init;
77    if (GV) {
78      if (GV->hasInitializer()) {
79        auto *CA = cast<ConstantArray>(GV->getInitializer());
80        for (auto &Op : CA->operands()) {
81          Constant *C = cast_or_null<Constant>(Op);
82          if (InitAsSet.insert(C).second)
83            Init.push_back(C);
84        }
85      }
86      GV->eraseFromParent();
87    }
88  
89    Type *Int8PtrTy = llvm::Type::getInt8PtrTy(M.getContext());
90    for (auto *V : Values) {
91      Constant *C = ConstantExpr::getPointerBitCastOrAddrSpaceCast(V, Int8PtrTy);
92      if (InitAsSet.insert(C).second)
93        Init.push_back(C);
94    }
95  
96    if (Init.empty())
97      return;
98  
99    ArrayType *ATy = ArrayType::get(Int8PtrTy, Init.size());
100    GV = new llvm::GlobalVariable(M, ATy, false, GlobalValue::AppendingLinkage,
101                                  ConstantArray::get(ATy, Init), Name);
102    GV->setSection("llvm.metadata");
103  }
104  
105  void llvm::appendToUsed(Module &M, ArrayRef<GlobalValue *> Values) {
106    appendToUsedList(M, "llvm.used", Values);
107  }
108  
109  void llvm::appendToCompilerUsed(Module &M, ArrayRef<GlobalValue *> Values) {
110    appendToUsedList(M, "llvm.compiler.used", Values);
111  }
112  
113  FunctionCallee
114  llvm::declareSanitizerInitFunction(Module &M, StringRef InitName,
115                                     ArrayRef<Type *> InitArgTypes) {
116    assert(!InitName.empty() && "Expected init function name");
117    return M.getOrInsertFunction(
118        InitName,
119        FunctionType::get(Type::getVoidTy(M.getContext()), InitArgTypes, false),
120        AttributeList());
121  }
122  
123  Function *llvm::createSanitizerCtor(Module &M, StringRef CtorName) {
124    Function *Ctor = Function::createWithDefaultAttr(
125        FunctionType::get(Type::getVoidTy(M.getContext()), false),
126        GlobalValue::InternalLinkage, 0, CtorName, &M);
127    Ctor->addFnAttr(Attribute::NoUnwind);
128    BasicBlock *CtorBB = BasicBlock::Create(M.getContext(), "", Ctor);
129    ReturnInst::Create(M.getContext(), CtorBB);
130    // Ensure Ctor cannot be discarded, even if in a comdat.
131    appendToUsed(M, {Ctor});
132    return Ctor;
133  }
134  
135  std::pair<Function *, FunctionCallee> llvm::createSanitizerCtorAndInitFunctions(
136      Module &M, StringRef CtorName, StringRef InitName,
137      ArrayRef<Type *> InitArgTypes, ArrayRef<Value *> InitArgs,
138      StringRef VersionCheckName) {
139    assert(!InitName.empty() && "Expected init function name");
140    assert(InitArgs.size() == InitArgTypes.size() &&
141           "Sanitizer's init function expects different number of arguments");
142    FunctionCallee InitFunction =
143        declareSanitizerInitFunction(M, InitName, InitArgTypes);
144    Function *Ctor = createSanitizerCtor(M, CtorName);
145    IRBuilder<> IRB(Ctor->getEntryBlock().getTerminator());
146    IRB.CreateCall(InitFunction, InitArgs);
147    if (!VersionCheckName.empty()) {
148      FunctionCallee VersionCheckFunction = M.getOrInsertFunction(
149          VersionCheckName, FunctionType::get(IRB.getVoidTy(), {}, false),
150          AttributeList());
151      IRB.CreateCall(VersionCheckFunction, {});
152    }
153    return std::make_pair(Ctor, InitFunction);
154  }
155  
156  std::pair<Function *, FunctionCallee>
157  llvm::getOrCreateSanitizerCtorAndInitFunctions(
158      Module &M, StringRef CtorName, StringRef InitName,
159      ArrayRef<Type *> InitArgTypes, ArrayRef<Value *> InitArgs,
160      function_ref<void(Function *, FunctionCallee)> FunctionsCreatedCallback,
161      StringRef VersionCheckName) {
162    assert(!CtorName.empty() && "Expected ctor function name");
163  
164    if (Function *Ctor = M.getFunction(CtorName))
165      // FIXME: Sink this logic into the module, similar to the handling of
166      // globals. This will make moving to a concurrent model much easier.
167      if (Ctor->arg_empty() ||
168          Ctor->getReturnType() == Type::getVoidTy(M.getContext()))
169        return {Ctor, declareSanitizerInitFunction(M, InitName, InitArgTypes)};
170  
171    Function *Ctor;
172    FunctionCallee InitFunction;
173    std::tie(Ctor, InitFunction) = llvm::createSanitizerCtorAndInitFunctions(
174        M, CtorName, InitName, InitArgTypes, InitArgs, VersionCheckName);
175    FunctionsCreatedCallback(Ctor, InitFunction);
176    return std::make_pair(Ctor, InitFunction);
177  }
178  
179  void llvm::filterDeadComdatFunctions(
180      SmallVectorImpl<Function *> &DeadComdatFunctions) {
181    SmallPtrSet<Function *, 32> MaybeDeadFunctions;
182    SmallPtrSet<Comdat *, 32> MaybeDeadComdats;
183    for (Function *F : DeadComdatFunctions) {
184      MaybeDeadFunctions.insert(F);
185      if (Comdat *C = F->getComdat())
186        MaybeDeadComdats.insert(C);
187    }
188  
189    // Find comdats for which all users are dead now.
190    SmallPtrSet<Comdat *, 32> DeadComdats;
191    for (Comdat *C : MaybeDeadComdats) {
192      auto IsUserDead = [&](GlobalObject *GO) {
193        auto *F = dyn_cast<Function>(GO);
194        return F && MaybeDeadFunctions.contains(F);
195      };
196      if (all_of(C->getUsers(), IsUserDead))
197        DeadComdats.insert(C);
198    }
199  
200    // Only keep functions which have no comdat or a dead comdat.
201    erase_if(DeadComdatFunctions, [&](Function *F) {
202      Comdat *C = F->getComdat();
203      return C && !DeadComdats.contains(C);
204    });
205  }
206  
207  std::string llvm::getUniqueModuleId(Module *M) {
208    MD5 Md5;
209    bool ExportsSymbols = false;
210    auto AddGlobal = [&](GlobalValue &GV) {
211      if (GV.isDeclaration() || GV.getName().startswith("llvm.") ||
212          !GV.hasExternalLinkage() || GV.hasComdat())
213        return;
214      ExportsSymbols = true;
215      Md5.update(GV.getName());
216      Md5.update(ArrayRef<uint8_t>{0});
217    };
218  
219    for (auto &F : *M)
220      AddGlobal(F);
221    for (auto &GV : M->globals())
222      AddGlobal(GV);
223    for (auto &GA : M->aliases())
224      AddGlobal(GA);
225    for (auto &IF : M->ifuncs())
226      AddGlobal(IF);
227  
228    if (!ExportsSymbols)
229      return "";
230  
231    MD5::MD5Result R;
232    Md5.final(R);
233  
234    SmallString<32> Str;
235    MD5::stringifyResult(R, Str);
236    return ("." + Str).str();
237  }
238  
239  void VFABI::setVectorVariantNames(CallInst *CI,
240                                    ArrayRef<std::string> VariantMappings) {
241    if (VariantMappings.empty())
242      return;
243  
244    SmallString<256> Buffer;
245    llvm::raw_svector_ostream Out(Buffer);
246    for (const std::string &VariantMapping : VariantMappings)
247      Out << VariantMapping << ",";
248    // Get rid of the trailing ','.
249    assert(!Buffer.str().empty() && "Must have at least one char.");
250    Buffer.pop_back();
251  
252    Module *M = CI->getModule();
253  #ifndef NDEBUG
254    for (const std::string &VariantMapping : VariantMappings) {
255      LLVM_DEBUG(dbgs() << "VFABI: adding mapping '" << VariantMapping << "'\n");
256      Optional<VFInfo> VI = VFABI::tryDemangleForVFABI(VariantMapping, *M);
257      assert(VI && "Cannot add an invalid VFABI name.");
258      assert(M->getNamedValue(VI.value().VectorName) &&
259             "Cannot add variant to attribute: "
260             "vector function declaration is missing.");
261    }
262  #endif
263    CI->addFnAttr(
264        Attribute::get(M->getContext(), MappingsAttrName, Buffer.str()));
265  }
266  
267  void llvm::embedBufferInModule(Module &M, MemoryBufferRef Buf,
268                                 StringRef SectionName, Align Alignment) {
269    // Embed the memory buffer into the module.
270    Constant *ModuleConstant = ConstantDataArray::get(
271        M.getContext(), makeArrayRef(Buf.getBufferStart(), Buf.getBufferSize()));
272    GlobalVariable *GV = new GlobalVariable(
273        M, ModuleConstant->getType(), true, GlobalValue::PrivateLinkage,
274        ModuleConstant, "llvm.embedded.object");
275    GV->setSection(SectionName);
276    GV->setAlignment(Alignment);
277  
278    LLVMContext &Ctx = M.getContext();
279    NamedMDNode *MD = M.getOrInsertNamedMetadata("llvm.embedded.objects");
280    Metadata *MDVals[] = {ConstantAsMetadata::get(GV),
281                          MDString::get(Ctx, SectionName)};
282  
283    MD->addOperand(llvm::MDNode::get(Ctx, MDVals));
284    GV->setMetadata(LLVMContext::MD_exclude, llvm::MDNode::get(Ctx, {}));
285  
286    appendToCompilerUsed(M, GV);
287  }
288