1 //===-- IRMutator.cpp -----------------------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/FuzzMutate/IRMutator.h"
11 #include "llvm/Analysis/TargetLibraryInfo.h"
12 #include "llvm/FuzzMutate/Operations.h"
13 #include "llvm/FuzzMutate/Random.h"
14 #include "llvm/FuzzMutate/RandomIRBuilder.h"
15 #include "llvm/IR/BasicBlock.h"
16 #include "llvm/IR/Function.h"
17 #include "llvm/IR/Instructions.h"
18 #include "llvm/IR/InstIterator.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/Transforms/Scalar/DCE.h"
24 static void createEmptyFunction(Module &M) {
25 // TODO: Some arguments and a return value would probably be more interesting.
26 LLVMContext &Context = M.getContext();
27 Function *F = Function::Create(FunctionType::get(Type::getVoidTy(Context), {},
29 GlobalValue::ExternalLinkage, "f", &M);
30 BasicBlock *BB = BasicBlock::Create(Context, "BB", F);
31 ReturnInst::Create(Context, BB);
34 void IRMutationStrategy::mutate(Module &M, RandomIRBuilder &IB) {
36 createEmptyFunction(M);
38 auto RS = makeSampler<Function *>(IB.Rand);
40 if (!F.isDeclaration())
41 RS.sample(&F, /*Weight=*/1);
42 mutate(*RS.getSelection(), IB);
45 void IRMutationStrategy::mutate(Function &F, RandomIRBuilder &IB) {
46 mutate(*makeSampler(IB.Rand, make_pointer_range(F)).getSelection(), IB);
49 void IRMutationStrategy::mutate(BasicBlock &BB, RandomIRBuilder &IB) {
50 mutate(*makeSampler(IB.Rand, make_pointer_range(BB)).getSelection(), IB);
53 void IRMutator::mutateModule(Module &M, int Seed, size_t CurSize,
55 std::vector<Type *> Types;
56 for (const auto &Getter : AllowedTypes)
57 Types.push_back(Getter(M.getContext()));
58 RandomIRBuilder IB(Seed, Types);
60 auto RS = makeSampler<IRMutationStrategy *>(IB.Rand);
61 for (const auto &Strategy : Strategies)
62 RS.sample(Strategy.get(),
63 Strategy->getWeight(CurSize, MaxSize, RS.totalWeight()));
64 auto Strategy = RS.getSelection();
66 Strategy->mutate(M, IB);
69 static void eliminateDeadCode(Function &F) {
70 FunctionPassManager FPM;
71 FPM.addPass(DCEPass());
72 FunctionAnalysisManager FAM;
73 FAM.registerPass([&] { return TargetLibraryAnalysis(); });
77 void InjectorIRStrategy::mutate(Function &F, RandomIRBuilder &IB) {
78 IRMutationStrategy::mutate(F, IB);
82 std::vector<fuzzerop::OpDescriptor> InjectorIRStrategy::getDefaultOps() {
83 std::vector<fuzzerop::OpDescriptor> Ops;
84 describeFuzzerIntOps(Ops);
85 describeFuzzerFloatOps(Ops);
86 describeFuzzerControlFlowOps(Ops);
87 describeFuzzerPointerOps(Ops);
88 describeFuzzerAggregateOps(Ops);
89 describeFuzzerVectorOps(Ops);
93 fuzzerop::OpDescriptor
94 InjectorIRStrategy::chooseOperation(Value *Src, RandomIRBuilder &IB) {
95 auto OpMatchesPred = [&Src](fuzzerop::OpDescriptor &Op) {
96 return Op.SourcePreds[0].matches({}, Src);
98 auto RS = makeSampler(IB.Rand, make_filter_range(Operations, OpMatchesPred));
100 report_fatal_error("No available operations for src type");
104 void InjectorIRStrategy::mutate(BasicBlock &BB, RandomIRBuilder &IB) {
105 SmallVector<Instruction *, 32> Insts;
106 for (auto I = BB.getFirstInsertionPt(), E = BB.end(); I != E; ++I)
107 Insts.push_back(&*I);
108 if (Insts.size() < 1)
111 // Choose an insertion point for our new instruction.
112 size_t IP = uniform<size_t>(IB.Rand, 0, Insts.size() - 1);
114 auto InstsBefore = makeArrayRef(Insts).slice(0, IP);
115 auto InstsAfter = makeArrayRef(Insts).slice(IP);
117 // Choose a source, which will be used to constrain the operation selection.
118 SmallVector<Value *, 2> Srcs;
119 Srcs.push_back(IB.findOrCreateSource(BB, InstsBefore));
121 // Choose an operation that's constrained to be valid for the type of the
122 // source, collect any other sources it needs, and then build it.
123 fuzzerop::OpDescriptor OpDesc = chooseOperation(Srcs[0], IB);
124 for (const auto &Pred : makeArrayRef(OpDesc.SourcePreds).slice(1))
125 Srcs.push_back(IB.findOrCreateSource(BB, InstsBefore, Srcs, Pred));
126 if (Value *Op = OpDesc.BuilderFunc(Srcs, Insts[IP])) {
127 // Find a sink and wire up the results of the operation.
128 IB.connectToSink(BB, InstsAfter, Op);
132 uint64_t InstDeleterIRStrategy::getWeight(size_t CurrentSize, size_t MaxSize,
133 uint64_t CurrentWeight) {
134 // If we have less than 200 bytes, panic and try to always delete.
135 if (CurrentSize > MaxSize - 200)
136 return CurrentWeight ? CurrentWeight * 100 : 1;
137 // Draw a line starting from when we only have 1k left and increasing linearly
138 // to double the current weight.
139 int Line = (-2 * CurrentWeight) * (MaxSize - CurrentSize + 1000);
140 // Clamp negative weights to zero.
146 void InstDeleterIRStrategy::mutate(Function &F, RandomIRBuilder &IB) {
147 auto RS = makeSampler<Instruction *>(IB.Rand);
148 // Avoid terminators so we don't have to worry about keeping the CFG coherent.
149 for (Instruction &Inst : instructions(F))
150 if (!Inst.isTerminator())
151 RS.sample(&Inst, /*Weight=*/1);
155 // Delete the instruction.
156 mutate(*RS.getSelection(), IB);
157 // Clean up any dead code that's left over after removing the instruction.
158 eliminateDeadCode(F);
161 void InstDeleterIRStrategy::mutate(Instruction &Inst, RandomIRBuilder &IB) {
162 assert(!Inst.isTerminator() && "Deleting terminators invalidates CFG");
164 if (Inst.getType()->isVoidTy()) {
165 // Instructions with void type (ie, store) have no uses to worry about. Just
166 // erase it and move on.
167 Inst.eraseFromParent();
171 // Otherwise we need to find some other value with the right type to keep the
173 auto Pred = fuzzerop::onlyType(Inst.getType());
174 auto RS = makeSampler<Value *>(IB.Rand);
175 SmallVector<Instruction *, 32> InstsBefore;
176 BasicBlock *BB = Inst.getParent();
177 for (auto I = BB->getFirstInsertionPt(), E = Inst.getIterator(); I != E;
179 if (Pred.matches({}, &*I))
180 RS.sample(&*I, /*Weight=*/1);
181 InstsBefore.push_back(&*I);
184 RS.sample(IB.newSource(*BB, InstsBefore, {}, Pred), /*Weight=*/1);
186 Inst.replaceAllUsesWith(RS.getSelection());