xref: /freebsd/contrib/llvm-project/llvm/lib/Transforms/Utils/ModuleUtils.cpp (revision c7a063741720ef81d4caa4613242579d12f1d605) 
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/TargetLibraryInfo.h"
15 #include "llvm/Analysis/VectorUtils.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 #include "llvm/Support/raw_ostream.h"
21 using namespace llvm;
22 
23 #define DEBUG_TYPE "moduleutils"
24 
25 static void appendToGlobalArray(const char *Array, Module &M, Function *F,
26                                 int Priority, Constant *Data) {
27   IRBuilder<> IRB(M.getContext());
28   FunctionType *FnTy = FunctionType::get(IRB.getVoidTy(), false);
29 
30   // Get the current set of static global constructors and add the new ctor
31   // to the list.
32   SmallVector<Constant *, 16> CurrentCtors;
33   StructType *EltTy = StructType::get(
34       IRB.getInt32Ty(), PointerType::getUnqual(FnTy), IRB.getInt8PtrTy());
35   if (GlobalVariable *GVCtor = M.getNamedGlobal(Array)) {
36     if (Constant *Init = GVCtor->getInitializer()) {
37       unsigned n = Init->getNumOperands();
38       CurrentCtors.reserve(n + 1);
39       for (unsigned i = 0; i != n; ++i)
40         CurrentCtors.push_back(cast<Constant>(Init->getOperand(i)));
41     }
42     GVCtor->eraseFromParent();
43   }
44 
45   // Build a 3 field global_ctor entry.  We don't take a comdat key.
46   Constant *CSVals[3];
47   CSVals[0] = IRB.getInt32(Priority);
48   CSVals[1] = F;
49   CSVals[2] = Data ? ConstantExpr::getPointerCast(Data, IRB.getInt8PtrTy())
50                    : Constant::getNullValue(IRB.getInt8PtrTy());
51   Constant *RuntimeCtorInit =
52       ConstantStruct::get(EltTy, makeArrayRef(CSVals, EltTy->getNumElements()));
53 
54   CurrentCtors.push_back(RuntimeCtorInit);
55 
56   // Create a new initializer.
57   ArrayType *AT = ArrayType::get(EltTy, CurrentCtors.size());
58   Constant *NewInit = ConstantArray::get(AT, CurrentCtors);
59 
60   // Create the new global variable and replace all uses of
61   // the old global variable with the new one.
62   (void)new GlobalVariable(M, NewInit->getType(), false,
63                            GlobalValue::AppendingLinkage, NewInit, Array);
64 }
65 
66 void llvm::appendToGlobalCtors(Module &M, Function *F, int Priority, Constant *Data) {
67   appendToGlobalArray("llvm.global_ctors", M, F, Priority, Data);
68 }
69 
70 void llvm::appendToGlobalDtors(Module &M, Function *F, int Priority, Constant *Data) {
71   appendToGlobalArray("llvm.global_dtors", M, F, Priority, Data);
72 }
73 
74 static void appendToUsedList(Module &M, StringRef Name, ArrayRef<GlobalValue *> Values) {
75   GlobalVariable *GV = M.getGlobalVariable(Name);
76   SmallPtrSet<Constant *, 16> InitAsSet;
77   SmallVector<Constant *, 16> Init;
78   if (GV) {
79     if (GV->hasInitializer()) {
80       auto *CA = cast<ConstantArray>(GV->getInitializer());
81       for (auto &Op : CA->operands()) {
82         Constant *C = cast_or_null<Constant>(Op);
83         if (InitAsSet.insert(C).second)
84           Init.push_back(C);
85       }
86     }
87     GV->eraseFromParent();
88   }
89 
90   Type *Int8PtrTy = llvm::Type::getInt8PtrTy(M.getContext());
91   for (auto *V : Values) {
92     Constant *C = ConstantExpr::getPointerBitCastOrAddrSpaceCast(V, Int8PtrTy);
93     if (InitAsSet.insert(C).second)
94       Init.push_back(C);
95   }
96 
97   if (Init.empty())
98     return;
99 
100   ArrayType *ATy = ArrayType::get(Int8PtrTy, Init.size());
101   GV = new llvm::GlobalVariable(M, ATy, false, GlobalValue::AppendingLinkage,
102                                 ConstantArray::get(ATy, Init), Name);
103   GV->setSection("llvm.metadata");
104 }
105 
106 void llvm::appendToUsed(Module &M, ArrayRef<GlobalValue *> Values) {
107   appendToUsedList(M, "llvm.used", Values);
108 }
109 
110 void llvm::appendToCompilerUsed(Module &M, ArrayRef<GlobalValue *> Values) {
111   appendToUsedList(M, "llvm.compiler.used", Values);
112 }
113 
114 FunctionCallee
115 llvm::declareSanitizerInitFunction(Module &M, StringRef InitName,
116                                    ArrayRef<Type *> InitArgTypes) {
117   assert(!InitName.empty() && "Expected init function name");
118   return M.getOrInsertFunction(
119       InitName,
120       FunctionType::get(Type::getVoidTy(M.getContext()), InitArgTypes, false),
121       AttributeList());
122 }
123 
124 Function *llvm::createSanitizerCtor(Module &M, StringRef CtorName) {
125   Function *Ctor = Function::createWithDefaultAttr(
126       FunctionType::get(Type::getVoidTy(M.getContext()), false),
127       GlobalValue::InternalLinkage, 0, CtorName, &M);
128   Ctor->addFnAttr(Attribute::NoUnwind);
129   BasicBlock *CtorBB = BasicBlock::Create(M.getContext(), "", Ctor);
130   ReturnInst::Create(M.getContext(), CtorBB);
131   // Ensure Ctor cannot be discarded, even if in a comdat.
132   appendToUsed(M, {Ctor});
133   return Ctor;
134 }
135 
136 std::pair<Function *, FunctionCallee> llvm::createSanitizerCtorAndInitFunctions(
137     Module &M, StringRef CtorName, StringRef InitName,
138     ArrayRef<Type *> InitArgTypes, ArrayRef<Value *> InitArgs,
139     StringRef VersionCheckName) {
140   assert(!InitName.empty() && "Expected init function name");
141   assert(InitArgs.size() == InitArgTypes.size() &&
142          "Sanitizer's init function expects different number of arguments");
143   FunctionCallee InitFunction =
144       declareSanitizerInitFunction(M, InitName, InitArgTypes);
145   Function *Ctor = createSanitizerCtor(M, CtorName);
146   IRBuilder<> IRB(Ctor->getEntryBlock().getTerminator());
147   IRB.CreateCall(InitFunction, InitArgs);
148   if (!VersionCheckName.empty()) {
149     FunctionCallee VersionCheckFunction = M.getOrInsertFunction(
150         VersionCheckName, FunctionType::get(IRB.getVoidTy(), {}, false),
151         AttributeList());
152     IRB.CreateCall(VersionCheckFunction, {});
153   }
154   return std::make_pair(Ctor, InitFunction);
155 }
156 
157 std::pair<Function *, FunctionCallee>
158 llvm::getOrCreateSanitizerCtorAndInitFunctions(
159     Module &M, StringRef CtorName, StringRef InitName,
160     ArrayRef<Type *> InitArgTypes, ArrayRef<Value *> InitArgs,
161     function_ref<void(Function *, FunctionCallee)> FunctionsCreatedCallback,
162     StringRef VersionCheckName) {
163   assert(!CtorName.empty() && "Expected ctor function name");
164 
165   if (Function *Ctor = M.getFunction(CtorName))
166     // FIXME: Sink this logic into the module, similar to the handling of
167     // globals. This will make moving to a concurrent model much easier.
168     if (Ctor->arg_empty() ||
169         Ctor->getReturnType() == Type::getVoidTy(M.getContext()))
170       return {Ctor, declareSanitizerInitFunction(M, InitName, InitArgTypes)};
171 
172   Function *Ctor;
173   FunctionCallee InitFunction;
174   std::tie(Ctor, InitFunction) = llvm::createSanitizerCtorAndInitFunctions(
175       M, CtorName, InitName, InitArgTypes, InitArgs, VersionCheckName);
176   FunctionsCreatedCallback(Ctor, InitFunction);
177   return std::make_pair(Ctor, InitFunction);
178 }
179 
180 void llvm::filterDeadComdatFunctions(
181     SmallVectorImpl<Function *> &DeadComdatFunctions) {
182   SmallPtrSet<Function *, 32> MaybeDeadFunctions;
183   SmallPtrSet<Comdat *, 32> MaybeDeadComdats;
184   for (Function *F : DeadComdatFunctions) {
185     MaybeDeadFunctions.insert(F);
186     if (Comdat *C = F->getComdat())
187       MaybeDeadComdats.insert(C);
188   }
189 
190   // Find comdats for which all users are dead now.
191   SmallPtrSet<Comdat *, 32> DeadComdats;
192   for (Comdat *C : MaybeDeadComdats) {
193     auto IsUserDead = [&](GlobalObject *GO) {
194       auto *F = dyn_cast<Function>(GO);
195       return F && MaybeDeadFunctions.contains(F);
196     };
197     if (all_of(C->getUsers(), IsUserDead))
198       DeadComdats.insert(C);
199   }
200 
201   // Only keep functions which have no comdat or a dead comdat.
202   erase_if(DeadComdatFunctions, [&](Function *F) {
203     Comdat *C = F->getComdat();
204     return C && !DeadComdats.contains(C);
205   });
206 }
207 
208 std::string llvm::getUniqueModuleId(Module *M) {
209   MD5 Md5;
210   bool ExportsSymbols = false;
211   auto AddGlobal = [&](GlobalValue &GV) {
212     if (GV.isDeclaration() || GV.getName().startswith("llvm.") ||
213         !GV.hasExternalLinkage() || GV.hasComdat())
214       return;
215     ExportsSymbols = true;
216     Md5.update(GV.getName());
217     Md5.update(ArrayRef<uint8_t>{0});
218   };
219 
220   for (auto &F : *M)
221     AddGlobal(F);
222   for (auto &GV : M->globals())
223     AddGlobal(GV);
224   for (auto &GA : M->aliases())
225     AddGlobal(GA);
226   for (auto &IF : M->ifuncs())
227     AddGlobal(IF);
228 
229   if (!ExportsSymbols)
230     return "";
231 
232   MD5::MD5Result R;
233   Md5.final(R);
234 
235   SmallString<32> Str;
236   MD5::stringifyResult(R, Str);
237   return ("." + Str).str();
238 }
239 
240 void VFABI::setVectorVariantNames(
241     CallInst *CI, const SmallVector<std::string, 8> &VariantMappings) {
242   if (VariantMappings.empty())
243     return;
244 
245   SmallString<256> Buffer;
246   llvm::raw_svector_ostream Out(Buffer);
247   for (const std::string &VariantMapping : VariantMappings)
248     Out << VariantMapping << ",";
249   // Get rid of the trailing ','.
250   assert(!Buffer.str().empty() && "Must have at least one char.");
251   Buffer.pop_back();
252 
253   Module *M = CI->getModule();
254 #ifndef NDEBUG
255   for (const std::string &VariantMapping : VariantMappings) {
256     LLVM_DEBUG(dbgs() << "VFABI: adding mapping '" << VariantMapping << "'\n");
257     Optional<VFInfo> VI = VFABI::tryDemangleForVFABI(VariantMapping, *M);
258     assert(VI.hasValue() && "Cannot add an invalid VFABI name.");
259     assert(M->getNamedValue(VI.getValue().VectorName) &&
260            "Cannot add variant to attribute: "
261            "vector function declaration is missing.");
262   }
263 #endif
264   CI->addFnAttr(
265       Attribute::get(M->getContext(), MappingsAttrName, Buffer.str()));
266 }
267 
268 void llvm::embedBufferInModule(Module &M, MemoryBufferRef Buf,
269                                StringRef SectionName) {
270   // Embed the buffer into the module.
271   Constant *ModuleConstant = ConstantDataArray::get(
272       M.getContext(), makeArrayRef(Buf.getBufferStart(), Buf.getBufferSize()));
273   GlobalVariable *GV = new GlobalVariable(
274       M, ModuleConstant->getType(), true, GlobalValue::PrivateLinkage,
275       ModuleConstant, "llvm.embedded.object");
276   GV->setSection(SectionName);
277 
278   appendToCompilerUsed(M, GV);
279 }
280