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
appendToGlobalArray(const char * Array,Module & M,Function * F,int Priority,Constant * Data)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
appendToGlobalCtors(Module & M,Function * F,int Priority,Constant * Data)66 void llvm::appendToGlobalCtors(Module &M, Function *F, int Priority, Constant *Data) {
67 appendToGlobalArray("llvm.global_ctors", M, F, Priority, Data);
68 }
69
appendToGlobalDtors(Module & M,Function * F,int Priority,Constant * Data)70 void llvm::appendToGlobalDtors(Module &M, Function *F, int Priority, Constant *Data) {
71 appendToGlobalArray("llvm.global_dtors", M, F, Priority, Data);
72 }
73
appendToUsedList(Module & M,StringRef Name,ArrayRef<GlobalValue * > Values)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
appendToUsed(Module & M,ArrayRef<GlobalValue * > Values)106 void llvm::appendToUsed(Module &M, ArrayRef<GlobalValue *> Values) {
107 appendToUsedList(M, "llvm.used", Values);
108 }
109
appendToCompilerUsed(Module & M,ArrayRef<GlobalValue * > Values)110 void llvm::appendToCompilerUsed(Module &M, ArrayRef<GlobalValue *> Values) {
111 appendToUsedList(M, "llvm.compiler.used", Values);
112 }
113
114 FunctionCallee
declareSanitizerInitFunction(Module & M,StringRef InitName,ArrayRef<Type * > InitArgTypes)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
createSanitizerCtor(Module & M,StringRef CtorName)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->addAttribute(AttributeList::FunctionIndex, 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
createSanitizerCtorAndInitFunctions(Module & M,StringRef CtorName,StringRef InitName,ArrayRef<Type * > InitArgTypes,ArrayRef<Value * > InitArgs,StringRef VersionCheckName)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>
getOrCreateSanitizerCtorAndInitFunctions(Module & M,StringRef CtorName,StringRef InitName,ArrayRef<Type * > InitArgTypes,ArrayRef<Value * > InitArgs,function_ref<void (Function *,FunctionCallee)> FunctionsCreatedCallback,StringRef VersionCheckName)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_size() == 0 ||
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
filterDeadComdatFunctions(Module & M,SmallVectorImpl<Function * > & DeadComdatFunctions)180 void llvm::filterDeadComdatFunctions(
181 Module &M, SmallVectorImpl<Function *> &DeadComdatFunctions) {
182 // Build a map from the comdat to the number of entries in that comdat we
183 // think are dead. If this fully covers the comdat group, then the entire
184 // group is dead. If we find another entry in the comdat group though, we'll
185 // have to preserve the whole group.
186 SmallDenseMap<Comdat *, int, 16> ComdatEntriesCovered;
187 for (Function *F : DeadComdatFunctions) {
188 Comdat *C = F->getComdat();
189 assert(C && "Expected all input GVs to be in a comdat!");
190 ComdatEntriesCovered[C] += 1;
191 }
192
193 auto CheckComdat = [&](Comdat &C) {
194 auto CI = ComdatEntriesCovered.find(&C);
195 if (CI == ComdatEntriesCovered.end())
196 return;
197
198 // If this could have been covered by a dead entry, just subtract one to
199 // account for it.
200 if (CI->second > 0) {
201 CI->second -= 1;
202 return;
203 }
204
205 // If we've already accounted for all the entries that were dead, the
206 // entire comdat is alive so remove it from the map.
207 ComdatEntriesCovered.erase(CI);
208 };
209
210 auto CheckAllComdats = [&] {
211 for (Function &F : M.functions())
212 if (Comdat *C = F.getComdat()) {
213 CheckComdat(*C);
214 if (ComdatEntriesCovered.empty())
215 return;
216 }
217 for (GlobalVariable &GV : M.globals())
218 if (Comdat *C = GV.getComdat()) {
219 CheckComdat(*C);
220 if (ComdatEntriesCovered.empty())
221 return;
222 }
223 for (GlobalAlias &GA : M.aliases())
224 if (Comdat *C = GA.getComdat()) {
225 CheckComdat(*C);
226 if (ComdatEntriesCovered.empty())
227 return;
228 }
229 };
230 CheckAllComdats();
231
232 if (ComdatEntriesCovered.empty()) {
233 DeadComdatFunctions.clear();
234 return;
235 }
236
237 // Remove the entries that were not covering.
238 erase_if(DeadComdatFunctions, [&](GlobalValue *GV) {
239 return ComdatEntriesCovered.find(GV->getComdat()) ==
240 ComdatEntriesCovered.end();
241 });
242 }
243
getUniqueModuleId(Module * M)244 std::string llvm::getUniqueModuleId(Module *M) {
245 MD5 Md5;
246 bool ExportsSymbols = false;
247 auto AddGlobal = [&](GlobalValue &GV) {
248 if (GV.isDeclaration() || GV.getName().startswith("llvm.") ||
249 !GV.hasExternalLinkage() || GV.hasComdat())
250 return;
251 ExportsSymbols = true;
252 Md5.update(GV.getName());
253 Md5.update(ArrayRef<uint8_t>{0});
254 };
255
256 for (auto &F : *M)
257 AddGlobal(F);
258 for (auto &GV : M->globals())
259 AddGlobal(GV);
260 for (auto &GA : M->aliases())
261 AddGlobal(GA);
262 for (auto &IF : M->ifuncs())
263 AddGlobal(IF);
264
265 if (!ExportsSymbols)
266 return "";
267
268 MD5::MD5Result R;
269 Md5.final(R);
270
271 SmallString<32> Str;
272 MD5::stringifyResult(R, Str);
273 return ("." + Str).str();
274 }
275
setVectorVariantNames(CallInst * CI,const SmallVector<std::string,8> & VariantMappings)276 void VFABI::setVectorVariantNames(
277 CallInst *CI, const SmallVector<std::string, 8> &VariantMappings) {
278 if (VariantMappings.empty())
279 return;
280
281 SmallString<256> Buffer;
282 llvm::raw_svector_ostream Out(Buffer);
283 for (const std::string &VariantMapping : VariantMappings)
284 Out << VariantMapping << ",";
285 // Get rid of the trailing ','.
286 assert(!Buffer.str().empty() && "Must have at least one char.");
287 Buffer.pop_back();
288
289 Module *M = CI->getModule();
290 #ifndef NDEBUG
291 for (const std::string &VariantMapping : VariantMappings) {
292 LLVM_DEBUG(dbgs() << "VFABI: adding mapping '" << VariantMapping << "'\n");
293 Optional<VFInfo> VI = VFABI::tryDemangleForVFABI(VariantMapping, *M);
294 assert(VI.hasValue() && "Cannot add an invalid VFABI name.");
295 assert(M->getNamedValue(VI.getValue().VectorName) &&
296 "Cannot add variant to attribute: "
297 "vector function declaration is missing.");
298 }
299 #endif
300 CI->addAttribute(
301 AttributeList::FunctionIndex,
302 Attribute::get(M->getContext(), MappingsAttrName, Buffer.str()));
303 }
304